Xi'an, China

Northwest University , located in Xi'an city, Shaanxi Province, is one of the nation's leading comprehensive universities. Founded in 1902, it is one of the oldest institutions of learning in Northwest China.Presently, the university has 11 colleges, 33 departments, 63 Bachelor's and Associate's programs. Its student population amounts to 18,000, including about 2000 Ph.D. and master students, and about 100 international students.The university stresses international academic and personnel exchanges. Since the start of the Chinese economic reform in 1978, it has established cooperation and exchange relations with nearly 30 institutions of higher education of scientific research in the United States, Japan, United Kingdom, France, Germany, Italy, Russia, Canada, Australia, Switzerland, Hong Kong, Taiwan, and The Philippines. Wikipedia.

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Liu X.L.,Northwest University, China | Liu X.L.,National University of Singapore | Fan H.M.,Northwest University, China | Yi J.B.,University of New South Wales | And 5 more authors.
Journal of Materials Chemistry | Year: 2012

Highly monodispersed magnetite nanoparticles with controlled particle size and mPEG surface coating have been successfully synthesized as a model system to investigate the effect of surface coating on the specific absorption rate (SAR) under an alternating magnetic field. Enhanced SAR with decreased surface coating thickness was observed and ascribed to the increased Brownian loss, improved thermal conductivity as well as improved dispersibility. By elaborate optimization of the surface coating and particle size, a significant increase of SAR (up to 74%) could be achieved with a minimal variation of the saturation magnetization (<5%). In particular, the 19nm@2000 sample exhibited the highest SAR of 930 W g -1 among the samples. Furthermore, this high heating capacity can be maintained in various simulated physiological conditions. Our results provide a general strategy for surface coating optimization of magnetic cores for high performance hyperthermia agents. © The Royal Society of Chemistry 2012.

Chen Y.,Yibin University | Hu W.,Yibin University | Feng Y.,Northwest University, China | Sweeney S.,Northwest University, China
Renewable and Sustainable Energy Reviews | Year: 2014

Developing biogas capacity is a key pillar in China's rural sustainable development program. The very dynamic transition of the rural socio-economic platform on which the current biogas development strategy has been based will require significant adjustments in material, technology and supply. The changes of socio-economic status, the problems of resent state and prospects of rural biogas development in China, including fermentation material, fermentation technology, development model and comprehensive utilization of biogas, are discussed in this paper. The results of our analysis indicated the full use of straw as a raw material will be the direction of biogas development in China. Dry methane fermentation will become an important method in the large scale production of biogas from agricultural wastes. The central supply model is the future biogas development model in rural China. It is with broad market and great potential to produce commercial fertilizer from biogas residue. Using biogas to generate electricity has become a new and efficient way to use biogas. © 2014 Elsevier Ltd.

Zhao Y.,Northwest University, China | Sun Y.,Northwest University, China | Diwu C.,Northwest University, China | Guo A.-L.,Northwest University, China | Ao W.-H.,Northwest University, China
Gondwana Research | Year: 2016

The Dunhuang region is located in the east of the Tarim Craton and has long been considered as part of a Precambrian terrane of the Tarim or North China Craton. Aiming to further understand the tectonic evolution of the Dunhuang region and its relations with the adjacent tectonic units, this study is to investigate the metamafic rocks in the Sanweishan area, Dunhuang region, and in turn to summarize the tectono-thermal events and re-examine the tectonic characteristics of the region. The metamafic rocks in the Sanweishan area include three types of amphibolites. They are garnet-clinopyroxene amphibolites, garnet-free amphibolites and garnet-mica amphibolites. The whole-rock major and trace element compositions suggest that their protoliths probably are E-MORB type tholeiitic basalts with some crustal addition. The LA-ICP-MS zircon U-Pb data of the garnet-clinopyroxene amphibolite and the garnet-free amphibolite yielded lower intercept ages of 410 ± 11 Ma and 403 ± 8 Ma, respectively, while the garnet-mica amphibolite gave three metamorphic ages of 441 ± 3 Ma, 408 ± 12 Ma and 370 ± 2 Ma. Three suites of metamorphic conditions have been estimated at 1.14-1.55 Gpa and 458-548 °C, 0.67-0.82 Gpa and 590-600 °C, and 0.47-0.66 Gpa and 557-586 °C for garnet-clinopyroxene amphibolite, using different mineral thermobarometers, which illustrate a collisional orogeny-related clockwise P-T path. Integrated with the study on the high-pressure granulite in the Mogutai area, it can be inferred that the metamafic rocks in the Sanweishan area obviously experienced amphibolite-facies metamorphism at ca. 410-400 Ma, and they could also underwent high-grade metamorphism at ca. 440-430 Ma. Therefore, we suggest that the E-W-trending collisional orogeny of ca. 440-400 Ma could sweep cross the Dunhuang region. The Dunhuang region records multiple tectono-thermal events occurring at ca. 3.1-2.5 Ga, ca. 2.3-1.6 Ga, ca. 440-400 Ma and ca. 370-310 Ma. However, compared with the limited exposure of the Precambrian complex, the Early Silurian-Late Carboniferous (ca. 440-310 Ma) orogeny-related metamorphic and magmatic rocks are widely distributed in the Dunhuang region, making up nearly 70% of the total exposure. Thus, it is proposed that the geological bodies in the Dunhuang region were mainly produced by a Paleozoic orogeny and represent a Paleozoic orogen, while the limited Precambrian complex probably is a microcontinental fragment or part of the margin of the Tarim or North China Cratons that was involved in this Paleozoic orogeny during the Early Silurian-Late Carboniferous. We infer that the Dunhuang orogenic belt is part of the Central Asian Orogenic Belt (CAOB), and thus the CAOB probably extends beyond the Beishan orogenic collage and southward into the Dunhuang region. © 2015 International Association for Gondwana Research.

Chen Y.,Northwest University, China | He M.,Northwest University, China | Wang C.,Northwest University, China | Wei Y.,Northwest University, China
Journal of Materials Chemistry A | Year: 2014

A novel polyvinyltetrazole-grafted resin with high capacity for the adsorption of heavy metal ions was prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) of acrylonitrile on chloromethylated crosslinked styrene-divinylbenzene resin and a subsequent cyano-tetrazole conversion reaction under microwave assistance. Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy were used to characterize the surface composition of the polyvinyltetrazole-grafted resin. It was found that the grafting amount of acrylonitrile increased linearly with the polymerization time, and approximately 70% of the cyano groups on the resin surface were converted to tetrazolyl groups, as estimated by elemental analysis. The maximum adsorption capacity of the resin was up to 1.52 mmol g-1 for Pb(ii), 2.65 mmol g-1 for Cu(ii) and 3.36 mmol g-1 for Cr(iii) at pH 5.0. The effects of pH and salt concentration on the adsorption suggested that the adsorption of metal ions was governed mainly by the chelation interaction. The adsorption isotherms of the three metal ions were best described by the Langmuir model, and their adsorption kinetics followed the pseudosecond-order kinetic equation. The adsorption of the three concerned metal ions was hardly affected by common coexisting ions such as Na(i), K(i), Ca(ii) and Mg(ii), whereas it was slightly decreased when Fe(iii) and Zn(ii) coexisted in the solution, which illustrates the selective adsorption of Pb(ii), Cu(ii) and Cr(iii) from wastewater. The resin has a good desorption rate and is reusable. In addition, the resin exhibited excellent chemical stability under strong acidic and alkaline conditions. These findings suggest that the resin could be potentially applied to the efficient removal of heavy metal ions from wastewater. © 2014 the Partner Organisations.

Deng S.,National University of Singapore | Tjoa V.,Nanyang Technological University | Tjoa V.,Singapore Institute of Manufacturing Technology | Fan H.M.,Northwest University, China | And 7 more authors.
Journal of the American Chemical Society | Year: 2012

Reduced graphene oxide (rGO)-conjugated Cu 2O nanowire mesocrystals were formed by nonclassical crystallization in the presence of GO and o-anisidine under hydrothermal conditions. The resultant mesocrystals are comprised of highly anisotropic nanowires as building blocks and possess a distinct octahedral morphology with eight {111} equivalent crystal faces. The mechanisms underlying the sequential formation of the mesocrystals are as follows: first, GO-promoted agglomeration of amorphous spherical Cu 2O nanoparticles at the initial stage, leading to the transition of growth mechanism from conventional ion-by-ion growth to particle-mediated crystallization; second, the evolution of the amorphous microspheres into hierarchical structure, and finally to nanowire mesocrystals through mesoscale transformation, where Ostwald ripening is responsible for the growth of the nanowire building blocks; third, large-scale self-organization of the mesocrystals and the reduction of GO (at high GO concentration) occur simultaneously, resulting in an integrated hybrid architecture where porous three-dimensional (3D) framework structures interspersed among two-dimensional (2D) rGO sheets. Interestingly, "super-mesocrystals" formed by 3D oriented attachment of mesocrystals are also formed judging from the voided Sierpinski polyhedrons observed. Furthermore, the interior nanowire architecture of these mesocrystals can be kinetically controlled by careful variation of growth conditions. Owing to high specific surface area and improved conductivity, the rGO-Cu 2O mesocrystals achieved a higher sensitivity toward NO 2 at room temperature, surpassing the performance of standalone systems of Cu 2O nanowires networks and rGO sheets. The unique characteristics of rGO-Cu 2O mesocrystal point to its promising applications in ultrasensitive environmental sensors. © 2012 American Chemical Society.

Hu X.,Northwest University, China | Yan S.,Shaanxi Provincial Fruit Trees Propagation Center | Shen K.,Northwest University, China
Field Crops Research | Year: 2013

Multi-location trials play an important role when evaluating genotypes at many stages of plant-breeding programs, as well as when recommending varietal plant production. The most common procedure for analyzing these trials is based on the assumption that the residual error variance is homogenous across all considered locations. However, this may often be unrealistic, and therefore limit the accuracy of genotype evaluations or the reliability of varietal recommendations. The objectives of this study were to investigate how frequently and how seriously the problem of heterogeneous variances appears across locations in multi-location trials, and to evaluate the impact of the analytical procedure with different considerations about error variations when comparing genotype effects. A series of 16 multi-location trials from a corn-breeding program in the north of China were simultaneously analyzed from 2005 to 2008 using a randomized complete block design at each location; the analysis used models with homogeneous residual variances, as well as models with heterogeneous residual variances to take into account that different locations may have different levels of precision. The results showed that the residual error variances strongly varied across locations in all of the considered trials. The model with heterogeneous residual error variances was significantly (α<. 0.001) more appropriate than the one with homogeneous error variances in all of the trials for both fixed and random locations, according to model fitting statistics. Ignoring error variance differences across locations in the analysis procedure of multi-location trials could result in a large Type I error rate for comparisons (F-test) of the main effect of genotypes, especially in case of random location main effects and genotype-location interactions, locations, and genotype-location interactions, as well as an inflation or deflation of statistical Type I error rates for comparisons (t-test) of simple genotype effects depending on specific locations. © 2013 Elsevier B.V.

Zheng Z.-C.,Sichuan Agricultural University | Zheng Z.-C.,Beijing Normal University | Zheng Z.-C.,Northwest University, China | He S.-Q.,University of Sichuan | Wu F.-Q.,Northwest University, China
Hydrological Processes | Year: 2014

The objective of this study was to determine the changing characteristics of soil surface roughness under different rainfall intensities and examine the interaction between soil surface roughness and different water erosion processes. Four artificial management practices (raking cropland, artificial hoeing, artificial digging, and contour tillage) were used according to the local agriculture customs of the Loess Plateau of China to simulate different types of soil surface roughness, using an additional smooth slope for comparison purposes. A total of 20 rainfall simulation experiments were conducted in five 1m by 2m boxes under two rainfall intensities (0.68 and 1.50mmmin-1) on a 15° slope. During splash erosion, soil surface roughness decreased in all treatments except raking cropland and smooth baseline under rainfall intensity of 0.68mmmin-1, while increasing for all treatments except smooth baseline under rainfall intensity of 1.50mmmin-1. During sheet erosion, soil surface roughness decreased for all treatments except hoeing cropland under rainfall intensity of 0.68mmmin-1. However, soil surface roughness increased for the artificial hoeing and raking cropland under rainfall intensity of 1.50mmmin-1. Soil surface roughness has a control effect on sheet erosion for different treatments under two rainfall intensities. For rill erosion, soil surface roughness increased for raking cropland and artificial hoeing treatments, and soil surface roughness decreased for artificial digging and the contour tillage treatments under two rainfall intensities. Under rainfall intensity of 0.68mmmin-1, the critical soil surface roughness was 0.706cm for the resistance control of runoff and sediment yield. Under rainfall intensity of 1.50mmmin-1, the critical soil surface roughness was 1.633cm for the resistance control of runoff, while the critical soil surface roughness was 0.706cm for the resistance control of sediment yield. These findings have important implications for clarifying the erosive nature of soil surface roughness and harnessing sloped farmland. © 2013 John Wiley & Sons, Ltd.

Cao J.,CAS Institute of Physics | Cui S.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Yang W.-L.,The Interdisciplinary Center | And 2 more authors.
Nuclear Physics B | Year: 2014

The spin- 1/2 XYZ model with both periodic and anti-periodic boundary conditions is studied via the off-diagonal Bethe ansatz method. The exact spectra of the Hamiltonians and the Bethe ansatz equations are derived by constructing the inhomogeneous T- Q relations, which allow us to treat both the even N (the number of lattice sites) and odd N cases simultaneously in a unified approach. © 2014 The Authors.

Li Y.-Y.,CAS Institute of Physics | Cao J.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Yang W.-L.,The Interdisciplinary Center | And 2 more authors.
Nuclear Physics B | Year: 2014

In two previous papers [26,27], the exact solutions of the spin-12 chains with arbitrary boundary fields were constructed via the off-diagonal Bethe ansatz (ODBA). Here we introduce a method to approach the thermodynamic limit of those models. The key point is that at a sequence of degenerate points of the crossing parameter η = ηm, the off-diagonal Bethe ansatz equations (BAEs) can be reduced to the conventional ones. This allows us to extrapolate the formulae derived from the reduced BAEs to arbitrary η case with O(N -2) corrections in the thermodynamic limit N→ ∞ As an example, the surface energy of the XXZ spin chain model with arbitrary boundary magnetic fields is derived exactly. This approach can be generalized to all the ODBA solvable models. © 2014.

Liu S.-Y.,Northwest University, China | Liu S.-Y.,CAS Institute of Physics | Zhang Y.-R.,CAS Institute of Physics | Zhao L.-M.,CAS Institute of Physics | And 2 more authors.
Annals of Physics | Year: 2014

We provide a family of general monogamy inequalities for global quantum discord (GQD), which can be considered as an extension of the usual discord monogamy inequality. It can be shown that those inequalities are satisfied under the similar condition for the holding of usual monogamy relation. We find that there is an intrinsic connection among them. Furthermore, we present a different type of monogamy inequality and prove that it holds under the condition that the bipartite GQDs do not increase when tracing out some subsystems. We also study the residual GQD based on the second type of monogamy inequality. As applications of those quantities, we investigate the GQDs and residual GQD in characterizing the quantum phase transition in the transverse field Ising model. © 2014 Elsevier Inc.

Zhang J.,Northwest University, China | Zhang H.-F.,Northwest University, China | Zhang H.-F.,CAS Institute of Geology and Geophysics | Lu X.-X.,Henan Academy of Land and Resources science
Precambrian Research | Year: 2013

A combined whole-rock geochemical and zircon U-Pb and Lu-Hf isotope study on two Precambrian lithotectonic units in the Songshan area, south-central North China Craton (NCC), was performed to constrain the tectonic evolution of the Trans-North China Orogen (TNCO) during collision between the Eastern and Western Blocks of the NCC. The metamorphic unit at Shipaihe consists of dioritic gneiss with minor amphibolitic enclave, whereas the magmatic unit at Shicheng is composed of granite. Zircon U-Pb dating demonstrate that the dioritic gneiss and enclave amphibolite were originally emplaced contemporaneously at ca. 2.5Ga. The magmatic zircons exhibit e{open}Hf(t) values of 2.2-7.8 and Hf model ages of 2.52-2.73Ga, suggesting that the dioritic gneiss was produced by reworking of the juvenile crust. The magmatic zircons of amphibolite have e{open}Hf(t) values of 0.7-8.1 and Hf model ages of 2.51-2.79Ga. The granite primarily gave zircon U-Pb ages of ca. 1.78Ga, with inherited zircons in ca. 1.87Ga. Zircon Lu-Hf isotopic analyses yield negative e{open}Hf(t) values of -16.7 to -1.8 and Hf model ages of 2.55-3.47Ga, indicating that the granite was mainly derived from reworking of ancient Archean crust. The Neoarchean dioritic gneiss and amphibolite show enrichment of LREE and LILE but depletion of HREE and HFSE, suggesting their derivation from anatexis of juvenile arc-type crust and enriched lithospheric mantle, respectively. The dioritic gneiss also has highly fractionated REE patterns and negligible negative Eu anomalies, implying anatexis at high pressures, where garnet and possibly amphibole as residual phases. The Paleoproterozoic granite has high K2O+Na2O and Zr, high ratios of total FeO/MgO and Ga/Al, and low contents of CaO, Al2O3, Ba, Sr and Eu/Eu* values, consistent with the characteristics of A-type granites. The negative Eu, Ba and Sr anomalies suggest that plagioclase acted as a residual phase during partial melting at relatively low pressures. Taken together, the Songshan metamorphic complex would originally derive from the reworking of juvenile arc-type crust and coeval partial melting of juvenile, enriched lithospheric mantle. Thus, an active continental margin was present in the late Neoarchean in south-central NCC, generating arc-type magmatism between the Eastern and Western Blocks. During the collisional orogeny, the arc-type crust in southern NCC underwent intensive metamorphism that followed by post-collisional extension at ca. 1.78Ga, and the reworking of the old continent in the southern TNCO yield Shicheng A-type granite. © 2012 Elsevier B.V.

Folmer H.,University of Groningen | Folmer H.,Northwest University, China | Johansson-Stenman O.,Gothenburg University
Environmental and Resource Economics | Year: 2011

In this paper we first critically review conventional environmental economics. We conclude that the standard theory offers too narrow a perspective for many real world problems and that many theories are not empirically tested. Consequently, environmental economics is at risk of producing aeroplanes without engines. Next, we welcome and discuss some recent trends, particularly the rapid developments of behavioural and new institutional economics as well as the increased interest in empirical analysis. Yet, we conclude that more 'logical duels' between competing theories, more interaction between theory and empirics, and more integration between the social sciences are needed to achieve a better understanding of real world environmental problems and the development of adequate policy handles. Finally, we present an outline of steps towards the development of an environmental social science and briefly present the papers that make up this special issue as important building stones of such a discipline. © 2011 Springer Science+Business Media B.V.

Rao Y.,Northwest University, China | Su J.,Northwest University, China | Su J.,Huazhong Agricultural University
Journal of Immunology Research | Year: 2015

Global fish production from aquaculture has rapidly grown over the past decades, and grass carp shares the largest portion. However, hemorrhagic disease caused by grass carp reovirus (GCRV) results in tremendous loss of grass carp (Ctenopharyngodon idella) industry. During the past years, development of molecular biology and cellular biology technologies has promoted significant advances in the understanding of the pathogen and the immune system. Immunoprophylaxis based on stimulation of the immune system of fish has also got some achievements. In this review, authors summarize the recent progresses in basic researches on GCRV; viral nucleic acid sensors, high-mobility group box proteins (HMGBs); pattern recognition receptors (PRRs), Toll-like receptors (TLRs) and retinoic acid inducible gene I- (RIG-I-) like receptors (RLRs); antiviral immune responses induced by PRRs-mediated signaling cascades of type I interferon (IFN-I) and IFN-stimulated genes (ISGs) activation. The present review also notices the potential applications of molecule genetic markers. Additionally, authors discuss the current preventive and therapeutic strategies (vaccines, RNAi, and prevention medicine) and highlight the importance of innate immunity in long term control for grass carp hemorrhagic disease. © 2015 Youliang Rao and Jianguo Su.

Zhao X.-D.,National University of Singapore | Fan H.-M.,National University of Singapore | Luo J.,CAS Institute of Physics | Ding J.,Northwest University, China | And 3 more authors.
Advanced Functional Materials | Year: 2011

A superhydrophobic membrane of MnO2 nanotube arrays on which a water droplet can be immobilized by application of a small DC bias, despite a large contact angle, is reported. For a 3 μL water droplet, the measured adhesive force increases monotonically with increasing negative voltage, reaching a maximum of 130 μN at 22 V, 25 times the original value. It follows that the nearly spherical water droplet can be controllably pinned on the substrate, even if the substrate is turned upside down. Moreover, the electrically adjustable adhesion is strongly polarity-dependent: only a five-fold increase is found when a positive bias of 22 V is applied. This remarkable electrically-controlled adhesive property is ascribed to the change in contact geometry between the water droplet and MnO2 nanotube array, on which water droplets exhibit the different continuities of three-phase contact line. As the modulation in this manner is in situ, fast, efficient and environmentally-friendly, this kind of smart material with electrically adjustable adhesive properties has a wide variety of applications in biotechnology and in lab-on-chip devices. The adhesive force of a water droplet on a superhydrophobic MnO2 nanotube array (MTA) shows a successive and controllable increase with the application of a small negative DC bias. This remarkable adhesive property is ascribed to the change in contact geometry between the water droplet and MTA. Such a smart interfacial material has a variety of applications in biotechnology and in lab-on-chip devices. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang D.,Peking University | Wang J.,Peking University | Lu M.,Peking University | Song F.,Peking University | And 2 more authors.
Bioinformatics | Year: 2010

Motivation: It is popular to explore meaningful molecular targets and infer new functions of genes through gene functional similarity measuring and gene functional network construction. However, little work is available in this field for microRNA (miRNA) genes due to limited miRNA functional annotations. With the rapid accumulation of miRNAs, it is increasingly needed to uncover their functional relationships in a systems level. Results: It is known that genes with similar functions are often associated with similar diseases, and the relationship of different diseases can be represented by a structure of directed acyclic graph (DAG). This is also true for miRNA genes. Therefore, it is feasible to infer miRNA functional similarity by measuring the similarity of their associated disease DAG. Based on the above observations and the rapidly accumulated human miRNA-disease association data, we presented a method to infer the pairwise functional similarity and functional network for human miRNAs based on the structures of their disease relationships. Comparisons showed that the calculated miRNA functional similarity is well associated with prior knowledge of miRNA functional relationship. More importantly, this method can also be used to predict novel miRNA biomarkers and to infer novel potential functions or associated diseases for miRNAs. In addition, this method can be easily extended to other species when sufficient miRNA-associated disease data are available for specific species. Availability: The online tool is available at http://cmbi.bjmu.edu.cn/misim. Contact: cuiqinghua@hsc.pku.edu.cn. Supplementary information: Supplementary data are available at Bioinformatics online. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org.

Zhao X.D.,National University of Singapore | Fan H.M.,National University of Singapore | Fan H.M.,Northwest University, China | Liu X.Y.,National University of Singapore | And 2 more authors.
Langmuir | Year: 2011

Tuning the adhesive force on a superhydrophobic MnO 2 nanostructured film was achieved by fabricating different patterns including meshlike, ball cactus-like, and tilted nanorod structures. The marvelous modulation range of the adhesive forces from 130 to nearly 0 μN endows these superhydrophobic surfaces with extraordinarily different dynamic properties of water droplets. This pattern-dependent adhesive property is attributed to the kinetic barrier difference resulting from the different continuity of the three-interface contact line. This finding will provide the general strategies for the adhesion adjustment on superhydrophobic surfaces. © 2011 American Chemical Society.

Zhang Y.,Yulin College | Zheng J.,Northwest University, China
Chinese Journal of Chemistry | Year: 2011

A robust and effective composite film combined the benefits of Nafion, room temperature ionic liquid (RTIL) and multi-wall carbon nanotubes (MWNTs) was prepared. Hemoglobin (Hb) was successfully immobilized on glassy carbon electrode surface by entrapping in the composite film. Direct electrochemistry and electrocatalysis of immobilized Hb were investigated in detail. A pair of well-defined and quasi-reversible redox peaks of Hb was obtained in 0.10 mol·L-1 pH 7.0 phosphate buffer solution (PBS), indicating that the Nafion-RTIL-MWNTs film showed an obvious promotion for the direct electron transfer between Hb and the underlying electrode. The immobilized Hb exhibited an excellent electrocatalytic activity towards the reduction of H 2O2. The catalysis current was linear to H 2O2 concentration in the range of 2.0×10 -6 to 2.5×10-4 mol·L-1, with a detection limit of 8.0×10-7 mol·L-1 (S/N=3). The apparent Michaelis-Menten constant (Km app) was calculated to be 0.34 mmol·L-1. Moreover, the modified electrode displayed a good stability and reproducibility. Based on the composite film, a third-generation reagentless biosensor could be constructed for the determination of H2O2. Directly electrochemistry of Hb was achieved through entrapping it in Nafion-RTIL-MWNTs composite film. The integration of RTILs and MWNTs provided a remarkable synergistic promotion for the direct electron transfer between Hb and the underlying electrode. The immobilized Hb showed an excellent electrocatalytic activity towards the reduction of H2O2. Based on the composite film, a third- generation reagentless biosensor could be constructed for the determination of H2O2. © 2011 SIOC, CAS, Shanghai & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wu S.,Northwest University, China
Advanced Materials Research | Year: 2012

In order to improve oxidation/erosion resistance of the T/P 24 steel components used in advanced power plants, chrome carbide coatings were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) on T/P24 at 700-1000°C. Microstructure and phase composition of the obtained surface layers were characterized employing X-ray diffraction and scanning electron microscopy with chemical analysis (SEM/EDS). Results showed that homogenous smooth chrome carbide coatings can be formed on the substrate. Phase composition of the prepared coatings are differs with PIRAC temperatures. Prepared at lower temperatures or short times treatment, Cr 23C 6, Cr 7C 3and Cr 3C 2 can be detected in the coatings. While, at higher temperatures or longer treatment times, Cr23C6 is subtotal phase of the produced coating. Moreover, the lower the PIRAC temperature is, the more of Cr 7C 3 and Cr 3C 2 are. Thermodynamics calculation based on Gibbs free energy is applied to explain phase composition difference of the coatings. © (2012) Trans Tech Publications.

Zhang J.,Northwest University, China | Chen S.,Jiangxi Agricultural University | Yang R.,Northwest University, China | Yan Y.,Northwest University, China
Fuel | Year: 2010

Zanthoxylum bungeanum seed oil (ZSO) with high free fatty acids (FFA) can be used for biodiesel production by ferric sulfate-catalyzed esterification followed by transesterification using calcium oxide (CaO) as an alkaline catalyst. Acid value of ZSO with high FFA can be reduced to less than 2 mg KOH/g by one-step esterification with methanol-to-FFA molar ratio 40.91:1, ferric sulfate 9.75% (based on the weight of FFA), reaction temperature 95 °C and reaction time 2 h, which satisfies transesterification using an alkaline catalyst. The response surface methodology (RSM) was used to optimize the conditions for ZSO biodiesel production using CaO as a catalyst. A quadratic polynomial equation was obtained for biodiesel conversion by multiple regression analysis and verification experiments confirmed the validity of the predicted model. The optimum combination for transesterification was methanol-to-oil molar ratio 11.69:1, catalyst amount 2.52%, and reaction time 2.45 h. At this optimum condition, the conversion to biodiesel reached above 96%. This study provided a practical method to biodiesel production from raw feedstocks with high FFA with high reaction rate, less corrosion, less toxicity, and less environmental problems. *ANOVA*analysis of variance*CaO*calcium oxide*FFA*free fatty acids*RSM*response surface methodology*ZSO*Zanthoxylum bungeanum seed oil. © 2009 Elsevier Ltd. All rights reserved.

Chen Y.,Yibin University | Hu W.,Yibin University | Sweeney S.,Northwest University, China
Renewable and Sustainable Energy Reviews | Year: 2013

The objective of this study was to assess biogas production capacity in different regions of China based on climate conditions and substrate availability. The results of our analysis indicated large differences in below-ground temperature and solar energy resources among different regions of China. According to data collected in 2006, slightly more than 1200 million tons of crop residue and manure could be used as substrates for biogas production. We suggest that household biogas technology must be developed according to local conditions. © 2013 Published by Elsevier Ltd.

Xiao Y.,Durham University | Niu Y.,Durham University | Niu Y.,Lanzhou University | Song S.,Peking University | And 2 more authors.
Lithos | Year: 2013

Subduction zone metamorphism (SZM) and behaviors of chemical elements in response to this process are important for both arc magmatism and mantle compositional heterogeneity. In this paper, we report the results of our petrographic and geochemical studies on blueschist and eclogite facies rocks of sedimentary and basaltic protoliths from two metamorphic sub-belts with different metamorphic histories in the North Qilian Mountain, Northwest China. The protolith of low-grade blueschists is basaltic in composition and is most likely produced in a back-arc setting, while the protoliths of high-grade blueschists/eclogites geochemically resemble the present-day normal and enriched mid-oceanic ridge basalts plus some volcanic arc rocks. The meta-sedimentary rocks, including meta-graywacke, meta-pelite, meta-chert and marble, show geochemical similarity to global oceanic (subducted) sediments. Assuming that high field strength elements (HFSEs) are relatively immobile, the correlated variations of rare earth elements (REEs) and Th with HFSEs suggest that all these elements are probably also immobile, whereas Pb and Sr are mobile in rocks of both basaltic and sedimentary protoliths during SZM. Ba, Cs and Rb are immobile in rocks of sedimentary protoliths and mobile in rocks of basaltic protolith. The apparent mobility of U in rocks of basaltic protolith may be inherited from seafloor alterations rather than caused by SZM.On the basis of in situ mineral compositional analysis (both major and trace elements), the most significant trace element storage minerals in these subduction-zone metamorphic rocks are: lawsonite, pumpellyite, apatite, garnet and epidote group minerals for REEs, white micas (both phengite and paragonite) for large ion lithophile elements, rutile and titanite for HFSEs. The presence and stability of these minerals exert the primary controls on the geochemical behaviors of most of these elements during SZM. The immobility of REEs, Th and U owing to their redistribution into newly formed minerals suggests that subduction-zone dehydration metamorphism will not contribute to the enrichment of these elements in arc magmatism. These observations require the formation and contribution of supercritical fluids or hydrous melts (these can effectively transport the aforementioned incompatible elements) from greater depths to arc magmatism. In addition, the overall sub-chondritic Nb/Ta ratio retained in rutile-bearing eclogites indicates that the subducting/subducted residual ocean crust passing through SZM cannot be responsible for the missing Nb (relative to Ta) in the bulk silicate earth. © 2012 Elsevier B.V.

Vasudevan D.,National University of Singapore | Vasudevan D.,Novartis | Fu A.,University of California at Berkeley | Fu A.,Northwest University, China | And 3 more authors.
Plant Cell | Year: 2012

Cyclophilin38 (CYP38) is one of the highly divergent cyclophilins from Arabidopsis thaliana. Here, we report the crystal structure of the At-CYP38 protein (residues 83 to 437 of 437 amino acids) at 2.39-Å resolution. The structure reveals two distinct domains: an N-terminal helical bundle and a C-terminal cyclophilin b-barrel, connected by an acidic loop. Two N-terminal b-strands become part of the C-terminal cyclophilin b-barrel, thereby making a previously undiscovered domain organization. This study shows that CYP38 does not possess peptidyl-prolyl cis/trans isomerase activity and identifies a possible interaction of CYP38 with the E-loop of chlorophyll protein47 (CP47), a component of photosystem II. The interaction of CYP38 with the E-loop of CP47 is mediated through its cyclophilin domain. The N-terminal helical domain is closely packed together with the putative C-terminal cyclophilin domain and establishes a strong intramolecular interaction, thereby preventing the access of the cyclophilin domain to other proteins. This was further verified by protein-protein interaction assays using the yeast two-hybrid system. Furthermore, the non-Leucine zipper N-terminal helical bundle contains several new elements for protein-protein interaction that may be of functional significance. Together, this study provides the structure of a plant cyclophilin and explains a possible mechanism for autoinhibition of its function through an intramolecular interaction. © 2012 American Society of Plant Biologists. All rights reserved.

Kale S.D.,Virginia Polytechnic Institute and State University | Gu B.,Virginia Polytechnic Institute and State University | Gu B.,Northwest University, China | Capelluto D.G.S.,Virginia Polytechnic Institute and State University | And 11 more authors.
Cell | Year: 2010

Pathogens of plants and animals produce effector proteins that are transferred into the cytoplasm of host cells to suppress host defenses. One type of plant pathogens, oomycetes, produces effector proteins with N-terminal RXLR and dEER motifs that enable entry into host cells. We show here that effectors of another pathogen type, fungi, contain functional variants of the RXLR motif, and that the oomycete and fungal RXLR motifs enable binding to the phospholipid, phosphatidylinositol-3-phosphate (PI3P). We find that PI3P is abundant on the outer surface of plant cell plasma membranes and, furthermore, on some animal cells. All effectors could also enter human cells, suggesting that PI3P-mediated effector entry may be very widespread in plant, animal and human pathogenesis. Entry into both plant and animal cells involves lipid raft-mediated endocytosis. Blocking PI3P binding inhibited effector entry, suggesting new therapeutic avenues. © 2010 Elsevier Inc.

Lanza M.,Peking University | Bayerl A.,Autonomous University of Barcelona | Gao T.,CAS Beijing National Laboratory for Molecular | Porti M.,Autonomous University of Barcelona | And 5 more authors.
Advanced Materials | Year: 2013

Graphene single-layer films are grown by chemical vapor deposition and transferred onto commercially available conductive tips for atomic force microscopy. Graphene-coated tips are much more resistant to both high currents and frictions than commercially available, metal-varnished, conductive atomic force microscopy tips, leading to much larger lifetimes and more reliable imaging due to a lower tip-sample interaction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Du Z.,Northwest University, China | Du Z.,Tarim University
Natural Product Communications | Year: 2011

A facile total synthesis of the bisabolane sesquiterpene, xanthorrhizol (1), has been achieved in 6 steps, in 48% overall yield. The starting material was 3-methoxy-4-methyl-phenoacetone (7), and a Claisen-Johnson rearrangement was used as the key step to construct the skeleton of the target molecule.

Li G.-L.,Northwest University, China | Pang X.-M.,Tianshui Soil and Water Conservation Experiment Station
Land Use Policy | Year: 2010

The purpose of this study was to assess the effect of grassland (GL) conversion to cropland (CL) and cropland conversion to forest (FL) and orchard (OL) on soil C and N distribution in dry aggregate size fractions in Nihegou catchment of the southern Loess Plateau, China. Four main land-use changes were analyzed in different agronomic management systems in 2006. The soil is wind-deposited loessial parent materials with a rather homogeneous silty clay loam texture classified as Calcic Cambosols. The GL was long-term over-used grassland. The CL was changed from GL after 33 years tillage with conventional tillage and fertilizer. The FL and OL originated from long-term CL after 23- and 7-year planted, respectively. Samples were taken at soil depths of 0-20 cm and 20-50 cm and were subjected to a physical fractionation process by way of aggregate size. Soil aggregate size fractions, total C and N contents and distributions were determined on all soil samples. Three dry aggregate fractions of very coarse (2.0-0.2 mm), coarse (0.2-0.05 mm) and fine (<0.05 mm) were obtained by shaking and sieving for 20 min. After 33 years of tillage, CL had 22% lower content of very coarse aggregates (2.0-0.2 mm) and 34% higher contents of fine aggregates (<0.05 mm) than GL. FL and OL soils had increased 9% and 10% contents of very coarse aggregates, and decreased 2% and 8% contents of fine aggregates compared to the CL. C and N losses in whole CL soils were 31% and 26% higher than those in GL. However, conversion of land uses from CL to FL (after 23 years) and OL (after 7 years) has increased C and N stocks by 76% and 40% in FL soils and by 66% and 63% in OL soils, respectively. This accessorial C and N stocks were higher in very coarse aggregate fractions (1.10 kg C m-2 and 0.13 kg N m-2 in FL soils, 1.43 kg C m-2 and 0.17 kg N m-2 in OL soils); moreover, the C and N stocks in fine aggregate fraction increased by 8% and 33% in FL soils and by 58% and 69% in OL soils, respectively. This results showed that C and N turnover and loss in aggregate fractions of this silty clay loam soils was very fast. Conversion of land uses from CL to FL and OL has obviously recovered the soil structure, and improved soil quality. © 2009 Elsevier Ltd. All rights reserved.

An S.-S.,Northwest University, China | An S.-S.,CAS Institute of Soil and Water Conservation | Darboux F.,French National Institute for Agricultural Research | Cheng M.,CAS Institute of Soil and Water Conservation
Geoderma | Year: 2013

Soil aggregate stability influences several aspects of soil physical behavior, such as water infiltration and soil erosion (Amézketa, 1999). We investigated the soil aggregate stability characteristics in the framework of the 'Grain for Green' vegetation rehabilitation project at the Loess Plateau (China) by using the Le Bissonnais (1996) and the modified Yoder (1936) methods. Both non-grazed grassland and afforestation revegetations were considered.The size distribution mode was always >. 2. mm for the fast wetting test (FW) in the non-grazed grassland communities. This fraction accounted for approximately 40% to 80% of the total soil weight. The wet stirring (WS) test showed a distribution similar to that determined by the FW test. For the slow wetting (SW) test, 80% or more of the non-grazed grassland soil fragments was >. 2. mm.The mean weighted diameter (MWD) that was determined by the Le Bissonnais' method was different among the tests and land uses. For the FW test, all the plant communities were significantly different from that of the recently abandoned grazing on grassland at the 0-20 and 20-40. cm depths. In the Artemisia sacrorum community, the maximum MWD was approximately 3. mm for the 0-20. cm depth. There were no significant differences among the plant communities after 3. years of afforestation and 7. years of non-grazing of the grassland. The MWDs were lower in the afforestation area than in the non-grazed grassland area. The maximum MWD value from the FW test was approximately 1.8. mm and was significantly lower (<. 0.5. mm) for cropland. The MWD of the modified Yoder method was positively related to the slow wetting and wet stirring (WS) tests of the Le Bissonnais' method (n. = 20 and r. = 0.83 and 0.87, respectively).In the Loess Plateau, revegetations by non-grazed grassland and afforestation are efficient means of increasing aggregate stability and decreasing soil erodibility. The aggregate stability under non-grazed grasslands is higher than that under afforestation. The effect of revegetation is persistent, which makes it a suitable long-term management practice. Compared with the modified Yoder's method, the FW test of the Le Bissonnais' method is better at determining aggregate stability differences among land uses and is recommended for future studies.© 2013 The Authors.

Li N.,Peking University | Chen Y.-J.,Peking University | Pirajno F.,University of Western Australia | Gong H.-J.,Northwest University, China | And 2 more authors.
Lithos | Year: 2012

Mesozoic granitoids are widespread in the southern margin of the North China Craton, and of particular geological interests because of their indication for lithospheric evolution and close association with porphyry Mo mineralization. In this contribution, in situ LA-ICP-MS U. -Pb, Hf isotope and trace element analyses of zircon crystals have been combined to constrain the emplacement time and petrogenesis of the Heyu granitic batholith which hosts the Yuchiling porphyry Mo system, Henan Province, China. As inferred from field investigations, the concentrically zoned Heyu batholith mainly consists of four texturally distinguishable phases, and displays a pattern of monotonically decreasing U. -Pb age from 143.0 ± 1.6. Ma for Phase 1, through 138.4 ± 1.5. Ma for Phase 2, through to ca. 135. Ma for Phase 3, and to 133.6 ± 1.3. Ma for the Mo-mineralized Yuchiling granite porphyry (Phase 4). The εHf(t) values (- 27.7 to - 3.4) and the two stage Hf model ages (1403 to 2924. Ma) of zircon grains, together with the ages of local strata, suggest that the magmas forming the Heyu batholith were dominantly sourced from the crust, with input of a mantle component. The higher Ce/Ce * ratios of the zircon crystals in the mineralized Yuchiling porphyry compared to those in the Mo-barren phases suggests that fluids exsolved from oxidic magmas might be more favorable for Mo enrichment. A regional synthesis suggests that intensive lithospheric thinning in the southern margin of the North China Craton should not be earlier than 130. Ma. © 2012 Elsevier B.V.

Jing G.,Northwest University, China | Zhang X.,Peking University | Yu D.,Peking University
Applied Physics A: Materials Science and Processing | Year: 2010

Although studies of ZnO nanostructured materials have concentrated on the electric, optical, and magnetic properties, applicational devices with nanoscale moving parts usually suffer mechanical fatigue and failure for reasons that are less understood. Here, differing from vertical bending and tension measurements, conventional threepoint bending tests are employed to study the elastic modulus and bending strength of ZnO nanowires (NWs) in an atomic force microscopy system. To shed new light on the extensive disagreement regarding the mechanical behavior of ZnO NWs, the effect of the surface morphology of the prepared NWs is mainly investigated. An average Young's modulus of 148 GPa close to that of the bulk ZnO materials is obtained, and the size dependence is found to be unaffected by the detailed micro and macro surface morphology. On the other hand, the bending strain of 0.2-0.7% is one order of magnitude lower than that reported in the literature. It indicates that an irregular surface such as cracks, flaws, curved and neck-like surface, and body defects dominates the fracture properties of ZnO NWs, rather than the elastic behavior. © 2010 Springer-Verlag.

Wei S.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Song J.,Northwest University, China | Khan N.I.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Khan N.I.,University of Dhaka
Hydrological Processes | Year: 2012

Accurate simulation and prediction of the dynamic behaviour of a river discharge over any time interval is essential for good watershed management. It is difficult to capture the high-frequency characteristics of a river discharge using traditional time series linear and nonlinear model approaches. Therefore, this study developed a wavelet-neural network (WNN) hybrid modelling approach for the predication of river discharge using monthly time series data. A discrete wavelet multiresolution method was employed to decompose the time series data of river discharge into sub-series with low (approximation) and high (details) frequency, and these sub-series were then used as input data for the artificial neural network (ANN). WNN models with different wavelet decomposition levels were employed to predict river discharge 48 months ahead of time. Comparison of results from the WNN models with those of the ANN models alone indicated that WNN models performed a more accurate prediction. © 2011 John Wiley & Sons, Ltd.

Wang J.,Northwest University, China | Fang D.,Northwest University, China | Chen X.,Northwest University, China | Yang Z.,University of Victoria | And 2 more authors.
Proceedings - IEEE INFOCOM | Year: 2013

Without relying on devices carried by the target, device-free localization (DFL) is attractive for many applications, such as wildlife monitoring. There still exist many challenges for DFL for multiple targets without dense deployment of sensor nodes. To fit the gap, in this paper, we propose a multi-target localization method based on compressive sensing, named LCS. The key observation is that given a pair of nodes, the received signal strength (RSS) will be different when a target locates at different locations. Taking advantage of compressive sensing in sparse recovery to handle the sparse property of the localization problem, (i.e., the vector which contains the number and location information of k targets is an ideal k-sparse signal), we presented a scalable compressive sensing based multiple target counting and localization method i.e., LCS, and rigorously justify the validity of the problem formulation. The results from our realistic deployment in a 12m×l2m open space are promising. For 12 people with 24 nodes, the worst localization error ratio and counting error ratio of our LCS is no more than 8.3% and 33.3% respectively. © 2013 IEEE.

Li Y.,Northwest University, China | Li Y.,University of Adelaide | Skouroumounis G.K.,University of Adelaide | Elsey G.M.,University of Adelaide | Taylor D.K.,University of Adelaide
Food Chemistry | Year: 2011

A microwave assisted extraction (MAE) method has been developed for the extraction of polyphenols from grape seeds of Vitis vinifera cultivars Cabernet Sauvignon, Shiraz, Sauvignon Blanc and Chardonnay. An initial five-factor (ethanol concentration in the extraction solvent, liquid:solid ratio, time, power and temperature), five-level orthogonal experimental array was designed and three factors (ethanol concentration in the extraction solvent, liquid:solid ratio and time) plus their best levels were chosen to optimise the extraction using a central composite rotatable design (CCRD) experiment. This revealed, after the use of response surface methodology, that the optimal extraction conditions were ethanol concentration (47.2%), liquid:solid ratio (45.3:1) and time (4.6 min). Total polyphenols were determined by application of the Folin-Ciocalteau method. Sequential application of the optimal conditions to one sample revealed that approximately 92% of the total polyphenols were extracted in the first instance. In comparison with other extraction methods, MAE provided comparable or better extraction, but was very much quicker. One key finding was that varying the applied power to the extraction was essentially irrelevant; inspection of the applied power profile during extraction revealed that the power was strictly modulated to maintain a constant temperature in the reaction cell. © 2011 Elsevier Ltd. All rights reserved.

Liu J.-Q.,Guangdong Medical College | Wang Y.-Y.,Northwest University, China | Wu T.,Guangdong Medical College | Wu J.,Guangxi University for Nationalities
CrystEngComm | Year: 2012

A series of entangled metal-organic polymers, namely [Co(bcp)(bib)] n (1), {[Co(bce)(bib) 0.5]·2H 2O} n (2), {[Co(oba)(bib)]·H 2O} n (3), {[Co(oba)(bib) 0.5]·0.5H 2O} n (4) and [Co(bce)(bi) 0.5] n (5) (H 2bcp = 1,3-bis(4-carboxy-phenoxy)propane, H 2bce = 1,2-bis(4-carboxy-phenoxy) ethane, H 2oba = 4,4′-oxybis(benzoic acid), bib = 1,4-bis(2-methyl-imidazol-1-yl)butane and bi = 1,1′-(1,4-butanediyl) bis(imidazole)), have been synthesized and structurally characterized by single crystal X-ray diffraction. Complexes 1-5 display various coordination motifs with different entangled forms and conformations. The result clearly indicates that the steric bulk effect of ligands is significant in the direction of these networks, which is also well regulated by the molar ratio. In addition, the magnetic behavior of polymers 1-4 are investigated. © 2012 The Royal Society of Chemistry.

Ye G.,Northwest University, China | Ye G.,CAS National Center for Nanoscience and Technology | Chen S.,CAS National Center for Nanoscience and Technology | Xiao Z.,CAS National Center for Nanoscience and Technology | And 3 more authors.
Journal of Materials Chemistry | Year: 2012

Two novel 56π-electron fullerenes, o-quinodimethane-methano[60]fullerene (OQMF) and thieno-o-quinodimethane-methano[60]fullerene (TOQMF), were prepared by Diels-Alder reaction between methano[60]fullerene and o-quinodimethane type dienes. These fullerenes possess not only high LUMO levels but also sterically small addends, featuring outstanding performance in polymer solar cells. Up to 5.74% and 5.51% PCEs were achieved for OQMF/P3HT and TOQMF/P3HT solar cells, respectively. © 2012 The Royal Society of Chemistry.

Cao J.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Shi K.,Northwest University, China | Wang Y.,CAS Institute of Physics
Nuclear Physics B | Year: 2013

Employing the off-diagonal Bethe ansatz method proposed recently by the present authors, we exactly diagonalize the XXX spin chain with arbitrary boundary fields. By constructing a functional relation between the eigenvalues of the transfer matrix and the quantum determinant, the associated T- Q relation and the Bethe ansatz equations are derived. © 2013 Elsevier B.V.

Cao J.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Shi K.,Northwest University, China | Wang Y.,CAS Institute of Physics
Nuclear Physics B | Year: 2013

The anisotropic spin-. 12 chains with arbitrary boundary fields are diagonalized with the off-diagonal Bethe ansatz method. Based on the properties of the R-matrix and the K-matrices, an operator product identity of the transfer matrix is constructed at some special points of the spectral parameter. Combining with the asymptotic behavior (for XXZ case) or the quasi-periodicity properties (for XYZ case) of the transfer matrix, the extended T-. Q ansatzes and the corresponding Bethe ansatz equations are derived. © 2013 Elsevier B.V.

Feng J.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Zhang Y.-Z.,University of Queensland | Fan H.,CAS Institute of Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We investigate the quantum teleportation between a conformal detector Alice and an inertial detector Bob in de Sitter space in two schemes, (i) one uses free scalar modes and (ii) one utilizes cavity to store qubit. We show that the fidelity of the teleportation is degraded for Bob in both cases. While the fidelity-loss is due to the Gibbons-Hawking effect associated with his cosmological horizon in the scheme (i), the entanglement decreases in the scheme (ii) because the ability to entangle the cavities is reduced by the spacetime curvature. With a cutoff at Planck-scale, comparing with the standard Bunch-Davies choice, we also show that the possible Planckian physics cause extra modifications to the fidelity of the teleportation protocol in both schemes. © 2013 Elsevier B.V.

Huang D.,Shanghai JiaoTong University | Huang P.,Shanghai JiaoTong University | Lin D.,Shanghai JiaoTong University | Wang C.,Shanghai JiaoTong University | And 2 more authors.
Optics Letters | Year: 2015

Wereport a100-MHz continuous-variable quantumkey distribution (CV-QKD) experiment over a 25-km fiber channel without sending a local oscillator (LO). We use a "locally" generated LO and implement with a 1-GHz shot-noise-limited homodyne detector to achieve high-speed quantum measurement, and we propose a secure phase compensation scheme to maintain a low level of excess noise. These make high-bit-rate CV-QKD significantly simpler for larger transmission distances compared with previous schemes in which both LO and quantum signals are transmitted through the insecure quantumchannel. © 2015 Optical Society of America.

Cao J.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Shi K.,Northwest University, China | Wang Y.,CAS Institute of Physics
Physical Review Letters | Year: 2013

A general method is proposed for constructing the Bethe ansatz equations of integrable models without U(1) symmetry. As an example, the exact spectrum of the XXZ spin ring with a Möbius-like topological boundary condition is derived by constructing a modified T-Q relation based on the functional connection between the eigenvalues of the transfer matrix and the quantum determinant of the monodromy matrix. With the exact solution, the elementary excitations of the topological XX spin ring are discussed in detail. It is found that the excitation spectrum indeed shows a nontrivial topological nature. © 2013 American Physical Society.

He Z.,Georgetown University | He Z.,Shanghai JiaoTong University | Jiang J.,Georgetown University | Kokkinaki M.,Georgetown University | And 5 more authors.
Stem Cells | Year: 2013

Studies on spermatogonial stem cells (SSCs) are of unusual significance because they are the unique stem cells that transmit genetic information to subsequent generations and they can acquire pluripotency to become embryonic stem-like cells that have therapeutic applications in human diseases. MicroRNAs (miRNAs) have recently emerged as critical endogenous regulators in mammalian cells. However, the function and mechanisms of individual miRNAs in regulating SSC fate remain unknown. Here, we report for the first time that miRNA-20 and miRNA-106a are preferentially expressed in mouse SSCs. Functional assays in vitro and in vivo using miRNA mimics and inhibitors reveal that miRNA-20 and miRNA-106a are essential for renewal of SSCs. We further demonstrate that these two miRNAs promote renewal at the post-transcriptional level via targeting STAT3 and Ccnd1 and that knockdown of STAT3, Fos, and Ccnd1 results in renewal of SSCs. This study thus provides novel insights into molecular mechanisms regulating renewal and differentiation of SSCs and may have important implications for regulating male reproduction. © AlphaMed Press.

Li Y.-Y.,CAS Institute of Physics | Cao J.,CAS Institute of Physics | Yang W.-L.,Northwest University, China | Yang W.-L.,The Interdisciplinary Center | And 2 more authors.
Nuclear Physics B | Year: 2014

The one-dimensional Hubbard model with arbitrary boundary magnetic fields is solved exactly via the Bethe ansatz methods. With the coordinate Bethe ansatz in the charge sector, the second eigenvalue problem associated with the spin sector is constructed. It is shown that the second eigenvalue problem can be transformed into that of the inhomogeneous XXX spin chain with arbitrary boundary fields which can be solved via the off-diagonal Bethe ansatz method. © 2013 The Authors.

Cheng S.-G.,Northwest University, China | Cheng S.-G.,Cooperation Technology | Zhang H.,CAS Institute of Physics | Sun Q.-F.,CAS Institute of Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The electron-hole inhomogeneity in graphene has been confirmed to be a new type of charge disorder by recent experiments, and the largest energy displacement of electron and hole puddles with respect to the Dirac point can reach nearly 30 meV. Here we focus on how the electron-hole inhomogeneity affects the specular Andreev reflection as well as the Andreev retroreflection. In a four-terminal graphene-superconductor hybrid system, we find that the Andreev coefficients can hardly be affected even under a rather large electron-hole inhomogeneity (typically 30 meV), and the boundary distinguishing two Andreev reflections can well hold, although the strength of the charge puddles, W=30 meV, is much larger than the superconductor gap, Δ=1 meV. Furthermore, when charge puddles are two orders of magnitude larger than the superconductor gap, a specific kind of Andreev reflection can still be obviously detected. To quantitatively describe what degree of the boundary is blurred, a quantity D is introduced which measures the width of a crossover region between specular Andreev reflection and retroreflection in energy space. We confirm that the boundary blurring is much smaller than the charge puddle strength W. In addition, we study the effect of Anderson disorder for comparison, and we find that the boundary is held much more obviously in this case. Finally, the fluctuations of the Andreev reflection coefficient are studied. Under a typical experimental charge puddle, the fluctuations are very small when the energy of the particles is away from the boundary, again confirming that the retroreflection and specular reflection can be clearly distinguished and detected in the presence of the electron-hole inhomogeneity. © 2011 American Physical Society.

Li W.,CAS Institute of Physics | Hou X.-M.,Northwest University, China | Wang P.-Y.,CAS Institute of Physics | Xi X.-G.,Northwest University, China | And 2 more authors.
Journal of the American Chemical Society | Year: 2013

Single-stranded guanine-rich sequences fold into compact G-quadruplexes. Although G-triplexes have been proposed and demonstrated as intermediates in the folding of G-quadruplexes, there is still a debate on their folding pathways. In this work, we employed magnetic tweezers to investigate the folding kinetics of single human telomeric G-quadruplexes in 100 mM Na+ buffer. The results are consistent with a model in which the G-triplex is an in-pathway intermediate in the folding of the G-quadruplex. By finely tuning the force exerted on the G-quadruplex, we observed reversible transitions from the G-quadruplex to the G-triplex as well as from the G-triplex to the unfolded coil when the force was increased from 26 to 39 pN. The energy landscape derived from the probability distribution shows clearly that the G-quadruplex goes through an intermediate when it is unfolded, and vice versa. © 2013 American Chemical Society.

Feng W.,Northwest University, China | Reisner A.,University of Illinois at Urbana - Champaign
Journal of Environmental Management | Year: 2011

Currently one of the largest and most rapidly developing countries, China also has some of the world's most severe environmental problems. China will most likely need to use all of the potential major strategies currently available to solve the country's huge environmental challenges, including promoting individual conservation behavior through educational campaigns and encouraging public environmental advocacy. This paper summarized the findings of a survey of 347 residents of Shaanxi province on environmental attitudes and behaviors. The survey found generally high levels of environmental knowledge and high recognition of the seriousness of environmental issues, moderate levels of individual actions supporting environmental resource conservation and low levels of public environmental behaviors, particularly for organized public advocacy. Further analysis indicated that the perceived importance of environmental protection is the most important factor influencing individual environmental resource conservation, but not public advocacy behaviors. Implications for environmental campaigns are discussed. © 2010 Elsevier Ltd.

Chen J.-C.,CAS Institute of Physics | Cheng S.-G.,Northwest University, China | Shen S.-Q.,University of Hong Kong | Sun Q.-F.,CAS Institute of Physics
Journal of Physics Condensed Matter | Year: 2010

Electronic transport in a graphene-based ferromagnetic/normal/ferromagnetic junction is investigated by means of the Landauer-Büttiker formalism and the nonequilibrium Green function technique. For the zigzag edge case, the results show that the conductance is always larger than e2/h for the parallel configuration of lead magnetizations, but for the antiparallel configuration the conductance becomes zero because of the band-selective rule. Therefore, a magnetoresistance (MR) plateau emerges with the value 100% when the Fermi energy is located around the Dirac point. In addition, choosing narrower graphene ribbons can yield wider 100% MR plateaus and the length change of the central graphene region does not affect the 100% MR plateaus. Although the disorder will reduce the MR plateau, the plateau value can still be kept about 50% even in a large disorder strength case. In addition, when the magnetizations of the left and right leads have a relative angle, the conductance changes as a cosine function of the angle. What is more, for the armchair edge case, the MR is usually small. So, it is more favorable to fabricate a graphene-based spin valve device by using a zigzag edge graphene ribbon. © 2010 IOP Publishing Ltd.

Huang K.,Northwest University, China | Ritland K.,University of British Columbia | Guo S.,Northwest University, China | Shattuck M.,University of Illinois at Urbana - Champaign | Li B.,Northwest University, China
Molecular Ecology Resources | Year: 2014

Studies in genetics and ecology often require estimates of relatedness coefficients based on genetic marker data. Many diploid estimators have been developed using either method-of-moments or maximum-likelihood estimates. However, there are no relatedness estimators for polyploids. The development of a moment estimator for polyploids with polysomic inheritance, which simultaneously incorporates the two-gene relatedness coefficient and various 'higher-order' coefficients, is described here. The performance of the estimator is compared to other estimators under a variety of conditions. When using a small number of loci, the estimator is biased because of an increase in ill-conditioned matrices. However, the estimator becomes asymptotically unbiased with large numbers of loci. The ambiguity of polyploid heterozygotes (when balanced heterozygotes cannot be distinguished from unbalanced heterozygotes) is also considered; as with low numbers of loci, genotype ambiguity leads to bias. A software, PolyRelatedness, implementing this method and supporting a maximum ploidy of 8 is provided. © 2013 John Wiley & Sons Ltd.

Farlow A.,Institute For Populationsgenetik | Farlow A.,Gregor Mendel Institute of Molecular Plant Biology | Dolezal M.,Institute For Populationsgenetik | Hua L.,Institute For Populationsgenetik | And 2 more authors.
Molecular Biology and Evolution | Year: 2012

Understanding the function of noncoding regions in the genome, such as introns, is of central importance to evolutionary biology. One approach is to assay for the targets of natural selection. On one hand, the sequence of introns, especially short introns, appears to evolve in an almost neutral manner. Whereas on the other hand, a large proportion of intronic sequence is under selective constraint. This discrepancy is largely dependent on intron length and differences in the methods used to infer selection. We have used a method based on DNA strand asymmetery that does not require comparison with any putatively neutrally evolving sequence, nor sequence conservation between species, to detect selection within introns. The strongest signal we identify is associated with short introns. This signal comes from a family of motifs that could act as cryptic 5# splice sites during mRNA processing, suggesting a mechanistic justification underlying this signal of selection. Together with an analysis of intron length and splice site strength, we observe that the genomic signature of splicing-coupled selection differs between long and short introns. © The Author 2011.

Zhao M.,Northwest University, China | Johnston R.J.,Clark University | Schultz E.T.,University of Connecticut
Environmental and Resource Economics | Year: 2013

The ecological literature accepts that many policy outcomes cannot be observed directly and must be characterized using indicators. Multiple indicators can often be used to communicate similar ecological outcomes. Previous studies using alternative indicators in stated preference surveys suggest that welfare estimates may be indicator-dependent, casting doubt on whether welfare estimates are sufficiently reliable for cost benefit analysis. We suggest that the reason for such indicator dependence may be that indicators used in these prior studies represented different outcomes valued by respondents. This possibility underscores the need for greater attention to selection of indicators and their properties within stated preference survey design. This paper develops a model introducing the concept of outcome equivalent indicators, defined as indicators that provide alternative representations of identical underlying outcomes. To assess empirically whether welfare estimates are indeed robust to indicator choice when alternative indicators are expected to be outcome equivalent, we analyze data from a choice experiment estimating willingness to pay for migratory fish restoration in Rhode Island, USA. Results demonstrate that welfare estimates are robust to the use of alternative ecological indicators within stated preference scenarios. © 2013 Springer Science+Business Media Dordrecht.

Li Y.,Northwest University, China | Luo X.,Northwest University, China | Yan Z.,Northwest University, China | Zheng J.,Northwest University, China | Qi H.,Shaanxi Normal University
Chemical Communications | Year: 2013

A method based on electrogenerated chemiluminescence (ECL) for detection of DNA methylation and assay of the methyltransferase activity is developed, and it is demonstrated that the label-free ECL method is capable of detecting methyltransferase with a detection limit of 3 × 10-6 U mL -1, using a supersandwich amplification technique. © 2013 The Royal Society of Chemistry.

Ma C.,University of Arizona | Ma C.,Northwest University, China | Zhang H.H.,University of Arizona | Wang X.,University of Arizona | Wang X.,China Agricultural University
Trends in Plant Science | Year: 2014

Rapid advances in high-throughput genomic technology have enabled biology to enter the era of 'Big Data' (large datasets). The plant science community not only needs to build its own Big-Data-compatible parallel computing and data management infrastructures, but also to seek novel analytical paradigms to extract information from the overwhelming amounts of data. Machine learning offers promising computational and analytical solutions for the integrative analysis of large, heterogeneous and unstructured datasets on the Big-Data scale, and is gradually gaining popularity in biology. This review introduces the basic concepts and procedures of machine-learning applications and envisages how machine learning could interface with Big Data technology to facilitate basic research and biotechnology in the plant sciences. © 2014 Elsevier Ltd.

Chen Y.,Shaanxi Normal University | Sun R.,Shaanxi Normal University | Wang B.,Northwest University, China
Journal of Colloid and Interface Science | Year: 2011

Betulinic acid (BA, a natural pentacyclic triterpene) can induce mitochondrial membrane damage and trigger the mitochondrial pathway of apoptosis in tumor cells. The monolayer behavior of binary systems of BA and cardiolipin (CL, a unique phospholipid found only in mitochondria membrane in animals) was studied by surface pressure-area (π-A) measurements and analyses and Atomic force microscopy (AFM) observation. The miscibility analysis presents that in mixed monolayers BA takes both tilted and nearly perpendicular orientations at surface pressure below 30. mN/m but only nearly perpendicular orientation at 30. mN/m. The thermodynamic stability analysis indicates that phase separation and repulsion occur in mixed BA/CL monolayers. The compressibility analysis shows that at 30. mN/m, 20% addition of BA does markedly translate the liquid-condensed CL monolayer to mixed BA/CL monolayer with the coexistence of liquid-condensed and liquid-expanded phases. The AFM images of supported monolayers give direct evidence of the conclusions obtained from the analyses of π-A isotherms. These results confirm that at high surface pressure near to real biologic situations, BA orients nearly perpendicularly with hydroxyl group toward water, causes phase separation and changes the permeability of CL film, which correlates with the mitochondrial membrane damage induced by BA. © 2010 Elsevier Inc.

Deng L.,Northwest University, China | Sweeney S.,Istanbul Science University | Shangguan Z.-P.,Northwest University, China
Grass and Forage Science | Year: 2014

This study quantifies the impact of four different grazing regimes (heavy, moderate, light and ungrazed) on the vegetation dynamics of rangeland ecosystems along the southern boundary area of the Mu Us Desert, China. As the grazing intensities decreased, the soil quality, canopy cover, height, density, above- and below-ground biomass, litter, root/shoot ratio and native plant (Aneurolepidium dasystachys) and grass abundances significantly increased; the above-ground biomass of grasses increased, but the above-ground biomass of forbs decreased. Ungrazed grassland has significantly improved from grasslands experiencing three other levels of grazing pressure, especially in the grassland biomass. Species richness increased as the grazing intensity decreased in the grazing grasslands, but peak species richness appeared under moderate and light grazing against lower productivity. Grazing exclusion causes desirable transitions in plant communities of desert steppe rangelands. Therefore, appropriate and efficient grazing exclusion is an available way to counteract local grassland degradation and promote rangeland sustainability. © 2013 John Wiley & Sons Ltd.

Ma L.-F.,Luoyang Normal University | Liu B.,Northwest University, China | Wang L.-Y.,Luoyang Normal University | Li C.-P.,Tianjin Normal University | Du M.,Tianjin Normal University
Dalton Transactions | Year: 2010

Hydrothermal reactions of mixed ligands 5-methoxyisophthalate (CH 3O-H2ip) and dipyridyl with Cu(OAc)2· 2H2O afford five new coordination polymers, including {[Cu(CH 3O-ip)(bpa)]·H2O}n (1), [Cu 2(CH3O-ip)2(bpa)0.5(H 2O)]n (2), [Cu2(CH3O-ip) 2(bpp)(H2O)]n (3), {[Cu3(CH 3O-ip)3(bpp)2(H2O)]·3H 2O}n (4) and [Cu4(CH3O-ip) 3(bpe)(OH)2]n (5) (bpp = 1,3-di(4-pyridyl) propane, bpa = 1,2-bi(4-pyridyl)ethane, and bpe = 1,2-di(4-pyridyl)ethylene). Compound 1 consists of CH3O-ip anion-bridged 1D CuII chains that are linked by trans-bpa into a 2D layer. Compound 2 is a 2D (4,4) layer that is connected by CH3O-ip anions. The gauche bpa in 2 lies in the cavity and meets the coordination requirement of the paddle-wheel dimeric copper unit. Compound 3 is an extended 3D polythreading network consisting of 2D (4,4) motifs with dangling bpp lateral arms. Compound 4 exhibits a 3D (4,6)-connected self-penetrating (65.8)(614.8) network that is composed of binuclear and mononuclear metal nodes. Compound 5 exhibits a 3D network with the tetranuclear [Cu4(μ3-OH) 2]6+ cluster acting as nodes, which is constructed by the interconnection of 2D helical layers via bpe pillars. The results of magnetic determination show that the syn-anti carboxylato bridges in our cases induce a weak antiferromagnetic interaction in 1, and the syn-syn carboxylato bridge in 3 and 4 mediates a strong antiferromagnetic interaction. © The Royal Society of Chemistry 2010.

Kong L.-A.,China Agricultural University | Kong L.-A.,Northwest University, China | Yang J.,China Agricultural University | Li G.-T.,Northwest University, China | And 6 more authors.
PLoS Pathogens | Year: 2012

Chitin is a major component of fungal cell wall and is synthesized by chitin synthases (Chs). Plant pathogenic fungi normally have multiple chitin synthase genes. To determine their roles in development and pathogenesis, we functionally characterized all seven CHS genes in Magnaporthe oryzae. Three of them, CHS1, CHS6, and CHS7, were found to be important for plant infection. While the chs6 mutant was non-pathogenic, the chs1 and chs7 mutants were significantly reduced in virulence. CHS1 plays a specific role in conidiogenesis, an essential step for natural infection cycle. Most of chs1 conidia had no septum and spore tip mucilage. The chs6 mutant was reduced in hyphal growth and conidiation. It failed to penetrate and grow invasively in plant cells. The two MMD-containing chitin synthase genes, CHS5 and CHS6, have a similar expression pattern. Although deletion of CHS5 had no detectable phenotype, the chs5 chs6 double mutant had more severe defects than the chs6 mutant, indicating that they may have overlapping functions in maintaining polarized growth in vegetative and invasive hyphae. Unlike the other CHS genes, CHS7 has a unique function in appressorium formation. Although it was blocked in appressorium formation by germ tubes on artificial hydrophobic surfaces, the chs7 mutant still produced melanized appressoria by hyphal tips or on plant surfaces, indicating that chitin synthase genes have distinct impacts on appressorium formation by hyphal tip and germ tube. The chs7 mutant also was defective in appressorium penetration and invasive growth. Overall, our results indicate that individual CHS genes play diverse roles in hyphal growth, conidiogenesis, appressorium development, and pathogenesis in M. oryzae, and provided potential new leads in the control of this devastating pathogen by targeting specific chitin synthases. © 2012 Kong et al.

Wei Z.,New Mexico State University | Wang T.,New Mexico State University | Wang T.,Northwest University, China | Nguyen P.A.,Ho Chi Minh City International University
International Journal of Approximate Reasoning | Year: 2015

In this paper, multivariate dependence concepts such as affiliation, association and positive lower orthant dependent are studied in terms of copulas. Relationships among these dependent concepts are obtained. An affiliation is a notion of dependence among the elements of a random vector. It has been shown that the affiliation property is preserved using linear interpolation of subcopula. Also our results are applied to the multivariate skew-normal copula. As an application, the dependence concepts used in auction with affiliated signals are discussed. Several examples are given for illustration of the main results. © 2015 Elsevier Inc.

Zhao D.,Tianjin Normal University | Zhao D.,Northwest University, China | Hopkins W.D.,Agnes Scott College | Hopkins W.D.,Yerkes National Primate Research Center | Li B.,Northwest University, China
American Journal of Physical Anthropology | Year: 2012

Handedness is a defining feature of human manual skill and understanding the origin of manual specialization remains a central topic of inquiry in anthropology and other sciences. In this study, we examined hand preference in a sample of wild primates on a task that requires bimanual coordinated actions (tube task) that has been widely used in captive primates. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is an arboreal Old World monkey species that is endemic to China, and 24 adult individuals from the Qinling Mountains of China were included for the analysis of hand preference in the tube task. All subjects showed strong individual hand preferences and significant group-level left-handedness was found. There were no significant differences between males and females for either direction or strength of hand preference. Strength of hand preferences of adults was significantly greater than juveniles. Use of the index finger to extract the food was the dominant extractive-act. Our findings represent the first evidence of population-level left-handedness in wild Old World monkeys and broaden our knowledge on evaluating primate hand preference via experimental manipulation in natural conditions. © 2012 Wiley Periodicals, Inc.

Lu C.,Northwest University, China | Zhang H.-Y.,Chinese Academy of Fishery Sciences | Ji J.,Northwest University, China | Wang G.-X.,Northwest University, China
Parasitology Research | Year: 2012

In order to find natural agents against Dactylogyrus intermedius in goldfish, petroleum ether, chloroform, ethyl acetate, acetone, and methanol extracts of three medicinal plants (Dryopteris crassirhizoma, Kochia scoparia, and Polygala tenuifolia) were screened for antiparasitic properties using in vivo anthelmintic efficacy assay. Among these extracts investigated, methanolic extract of D. crassirhizoma was observed the most effective with EC 50 value of 22.97 mg L -1 after 48 h of exposure, which exhibited a 100% efficacy against D. intermedius at 60.00 mg L -1, followed by the methanolic extracts of K. scoparia and P. tenuifolia with EC 50 values of 31.28 and 154.79 mg L -1, showing 100% efficacy against D. intermedius at 60.00 and 500.00 mg L -1, respectively. In addition, acute toxicity assay indicated that 48-h LC 50 values of methanolic extracts of D. crassirhizoma, K. scoparia, andP. tenuifolia were 4.10-, 2.27-, and 5.00-fold higher than the corresponding EC 50. The obtained results demonstrated that methanolic extracts of D. crassirhizoma, K. scoparia, and P. tenuifolia have the potential for the development of novel therapy for the control of D. intermedius in aquaculture. © Springer-Verlag 2011.

Li Y.,Northwest University, China | Huang C.,Northwest University, China | Zheng J.,Northwest University, China | Qi H.,Shaanxi Normal University
Talanta | Year: 2013

An ultrasensitive electrogenerated chemiluminescent (ECL) DNA-based biosensing switch for the determination of bleomycin (BLM) was developed based on Fe(II)·BLM-mediated hairpin DNA strand cleavage and a structure-switching ECL-dequenching mechanism. A thiolated ss-DNA was used as a substrate for BLMs: one terminus was tethered onto an electrode surface, and the other terminus was labelled with the ECL quencher ferrocene to form a hairpin structure. This thiolated ss-DNA self-assembled on to the tris(2,2′- bipyridine)ruthenium-gold nanoparticle composite modified gold electrode. In the presence of Fe(II)·BLM, the ECL DNA biosensing switch undergoes an irreversible cleavage event that can trigger a significant increase in ECL intensity. The relationship of ECL intensity and the concentration of BLMs was found to be linear in the range of 5 fM-5000 fM with a detection limit of 2 fM. This work demonstrates that the design of a highly sensitive ECL DNA-based biosensing switch that uses the sequence selectivity of DNA cleavage mediated by the antitumor drug BLM in combination with a chemical quencher, such as ferrocene, to quench ECL signal(s), offers a promising approach for the determination of ultratrace amounts of antitumor drugs. © 2012 Elsevier B.V. All rights reserved.

He J.-M.,Shaanxi Normal University | He J.-M.,CAS Institute of Earth Environment | Ma X.-G.,Shaanxi Normal University | Zhang Y.,Shaanxi Normal University | And 5 more authors.
Plant Physiology | Year: 2013

Heterotrimeric G proteins have been shown to transmit ultraviolet B (UV-B) signals in mammalian cells, but whether they also transmit UV-B signals in plant cells is not clear. In this paper, we report that 0.5Wm-2 UV-B induces stomatal closure in Arabidopsis (Arabidopsis thaliana) by eliciting a cascade of intracellular signaling events including Ga protein, hydrogen peroxide (H2O2), and nitric oxide (NO). UV-B triggered a significant increase in H2O2 or NO levels associated with stomatal closure in the wild type, but these effects were abolished in the single and double mutants of AtrbohD and AtrbohF or in the Nia1 mutants, respectively. Furthermore, we found that UV-B-mediated H2O2 and NO generation are regulated by GPA1, the Ga-subunit of heterotrimeric G proteins. UV-B-dependent H2O2 and NO accumulation were nullified in gpa1 knockout mutants but enhanced by overexpression of a constitutively active form of GPA1 (cGa). In addition, exogenously applied H2O2 or NO rescued the defect in UV-B-mediated stomatal closure in gpa1 mutants, whereas cGa AtrbohD/AtrbohF and cGa nia1 constructs exhibited a similar response to AtrbohD/ AtrbohF and Nia1, respectively. Finally, we demonstrated that Ga activation of NO production depends on H2O2. The mutants of AtrbohD and AtrbohF had impaired NO generation in response to UV-B, but UV-B-induced H2O2 accumulation was not impaired in Nia1. Moreover, exogenously applied NO rescued the defect in UV-B-mediated stomatal closure in the mutants of AtrbohD and AtrbohF. These findings establish a signaling pathway leading to UV-B-induced stomatal closure that involves GPA1-dependent activation of H2O2 production and subsequent Nia1-dependent NO accumulation. © 2013 American Society of Plant Biologists. All Rights Reserved.

Chen K.,Northwest University, China | Liu C.,Northwest University, China | He Y.,Oklahoma State University | Jiang H.,Oklahoma State University | Lu Z.,Northwest University, China
Developmental and Comparative Immunology | Year: 2014

Recognition of invading microbes as non-self is the first step of immune responses. In insects, peptidoglycan recognition proteins (PGRPs) detect peptidoglycans (PGs) of bacterial cell wall, leading to the activation of defense responses. Twelve PGRPs have been identified in the silkworm, Bombyx mori, through bioinformatics analysis. However, their biochemical functions are mostly uncharacterized. In this study, we found PGRP-S5 transcript levels were up-regulated in fat body and midgut after bacterial infection. Using recombinant protein isolated from Escherichia coli, we showed that PGRP-S5 binds to PGs from certain bacterial strains and induces bacteria agglutination. Enzyme activity assay confirmed PGRP-S5 is an amidase; we also showed it is an antibacterial protein effective against both Gram-positive and -negative bacteria. Additionally, we demonstrated that specific recognition of PGs by PGRP-S5 is involved in the prophenoloxidase activation pathway. Together, these data suggest the silkworm PGRP-S5 functions as a pattern recognition receptor for the prophenoloxidase pathway initiation and as an effecter to inhibit bacterial growth as well. We finally discussed possible roles of PGRP-S5 as a receptor for antimicrobial peptide gene induction and as an immune modulator in the midgut. © 2014 Elsevier Ltd.

Zhang S.,Northwest University, China | Sadras V.,South Australian Research And Development Institute | Chen X.,China Agricultural University | Zhang F.,China Agricultural University
Field Crops Research | Year: 2014

Owing to the critical situation of water resources and demographic pressure, improvement of crop water use efficiency (WUE = grain yield per unit seasonal evapotranspiration) in the dryland area of Loess Plateau of China is crucial. The aims of this study were (i) quantifying WUE of dryland maize (Zea mays L.) in the Loess Plateau, and (ii) identifying management practices that improve both WUE and yield. We compiled a data base of 36 sets of experiments spanning more than 20 years, where conventional practice (CT) was compared with alternatives including RT/NT, reduced or no tillage without straw mulching; SM, straw mulching; PM, plastic film mulching 100%; RM, plastic film mulching 50% or more; RMS, ridge mulched with plastic film. +. furrow mulched with crop straw. Yield ranged from 1.12 to 14.6Mgha-1 and WUE from 2.8 to 39.0kgha-1mm-1; the maximum yield and WUE were achieved under RM, PM and RMS and the minimum under CT. Practices had small and inconsistent effect on seasonal evapotranspiration, hence variation in yield and WUE were attributable to changes in both the contribution of soil evaporation to total evapotranspiration and the partitioning of seasonal water use before and after silking. The yield-evapotranspiration relationship indicated that attainable WUE was 40kgha-1mm-1. Few crops, however, reached this efficiency emphasizing the opportunities for improvement. Implications for crop management and further improvement in yield and WUE are discussed. © 2014 Elsevier B.V.

Zhao D.,Tianjin Normal University | Zhao D.,Northwest University, China | Li B.,Northwest University, China | Yu K.,Tianjin Normal University | Zheng L.,Tianjin Normal University
American Journal of Physical Anthropology | Year: 2012

The ratio of the length of the second finger to the fourth finger (2D:4D) is considered to be a putative proxy of prenatal exposure to testosterone, and has been increasingly used as a promising tool to evaluate the impact of prenatal androgenization in humans in such traits as physical performance. In this study, for the first time, we present 2D:4D data on adult participants of Han ethnicity. We consider the sexual dimorphism of 2D:4D and handgrip strength, and also report the relationship between 2D:4D and handgrip strength of males and females. The sample consisted of 54 males and 55 females recruited from a remote village in the Qinling Mountains, China. We found sexual dimorphism of both 2D:4D and handgrip strength, i.e., males had lower 2D:4D and right-left 2D:4D than females and greater handgrip strength than females. There was a sex-specific correlation between 2D:4D and handgrip strength, i.e., 2D:4D in the right hand was negatively correlated with handgrip strength in males but not in females. This relationship may be driven by sexual selection operating on fetal programming. Copyright © 2012 Wiley Periodicals, Inc.

Li Y.,Northwest University, China | Li Y.,Shaanxi Normal University | Qi H.,Shaanxi Normal University | Gao Q.,Shaanxi Normal University | Zhang C.,Shaanxi Normal University
Biosensors and Bioelectronics | Year: 2011

A novel label-free electrogenerated chemiluminescence (ECL) aptasensor for the determination of lysozyme is designed employing lysozyme binding aptamer (LBA) as molecular recognition element for lysozyme as a model analyte and Ru(bpy)32+ as an ECL signal compound. This ECL aptasensor was fabricated by self-assembling the thiolated LBA onto the surface of a gold electrode. Using this aptasensor, sensitive quantitative detection of lysozyme is realized on basis of the competition of lysozyme with Ru(bpy)32+ cation for the binding sites of LBA. In the presence of lysozyme, the aptamer sequence prefers to form the LBA-lysozyme complex, the less negative environment allows Ru(bpy)32+ cations to be less bound electrostatically to the LBAs on the electrode surface, in conjunction with the generation of a decreased ECL signal. The integrated ECL intensity versus the concentration of lysozyme was linear in the range from 6.4×10-10M to 6.4×10-7M. The detection limit was 1.2×10-10M. This work demonstrates that using the competition of target protein with an ECL signal compound Ru(bpy)32+ for binding sites of special aptamer confined on the electrode is promising approach for the design of label-free ECL aptasensors for the determination of proteins. © 2010 Elsevier B.V.

Hu T.,Northwest University, China | Kang S.,China Agricultural University | Li F.,Guangxi University | Zhang J.,Hong Kong Baptist University
Journal of Experimental Botany | Year: 2011

Effects of partial root-zone irrigation (PRI) on the hydraulic conductivity in the soil-root system (Lsr) in different root zones were investigated using a pot experiment. Maize plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation, CI), on one side only (fixed PRI, FPRI), or alternately on one of two sides (alternate PRI, APRI). Results show that crop water consumption was significantly correlated with Lsr in both the whole and irrigated root zones for all three irrigation methods but not with Lsr in the non-irrigated root zone of FPRI. The total L sr in the irrigated root zone of two PRIs was increased by 49.0-92.0% compared with that in a half root zone of CI, suggesting that PRI has a significant compensatory effect of root water uptake. For CI, the contribution of Lsr in a half root zone to Lsr in the whole root zone was ∼50%. For FPRI, the Lsr in the irrigated root zone was close to that of the whole root zone. As for APRI, the Lsr in the irrigated root zone was greater than that of the non-irrigated root zone. In comparison, the Lsr in the non-irrigated root zone of APRI was much higher than that in the dried zone of FPRI. The L sr in both the whole and irrigated root zones was linearly correlated with soil moisture in the irrigated root zone for all three irrigation methods. For the two PRI treatments, total water uptake by plants was largely determined by the soil water in the irrigated root zone. Nevertheless, the non-irrigated root zone under APRI also contributed to part of the total crop water uptake, but the continuously non-irrigated root zone under FPRI gradually ceased to contribute to crop water uptake, suggesting that it is the APRI that can make use of all the root system for water uptake, resulting in higher water use efficiency. © 2011 The Author.

Fan H.,Northwest University, China | Kong L.,CAS Wuhan Institute of Rock and Soil Mechanics
Canadian Geotechnical Journal | Year: 2013

As indicated by the theory of a clay-water-electrolyte system, the dispersive mechanism of cohesive soil involves three aspects: low clay content, high sodium ion percentage, and strongly alkaline pH. Accordingly, an empirical equation was established with an associated procedure and criteria proposed for evaluating the dispersivity of cohesive soil. The equation consists of four soil physical and chemical indicators: liquid limit (WL), clay content (PC), sodium percentage in the pore water (PS), and pH. The equation is F = 4 - 0.01(2WL + PC - PS) + 0.1 pH, where F is the soil dispersivity value. Compared with the evaluation based on laboratory tests, the empirical equation had higher accuracy for the evaluation of the dispersivity of cohesive soil, and was thus conducive to greater engineering safety. This indicates that the proposed empirical equation is applicable for evaluating the dispersivity of cohesive soil in general engineering.

Deng L.,Northwest University, China | Shangguan Z.-P.,Northwest University, China | Sweeney S.,Istanbul Science University
PLoS ONE | Year: 2013

The revegetation of abandoned farmland significantly influences soil organic C (SOC) and total N (TN). However, the dynamics of both soil OC and N storage following the abandonment of farmland are not well understood. To learn more about soil C and N storages dynamics 30 years after the conversion of farmland to grassland, we measured SOC and TN content in paired grassland and farmland sites in the Zhifanggou watershed on the Loess Plateau, China. The grassland sites were established on farmland abandoned for 1, 7, 13, 20, and 30 years. Top soil OC and TN were higher in older grassland, especially in the 0-5 cm soil depths; deeper soil OC and TN was lower in younger grasslands (<20 yr), and higher in older grasslands (30 yr). Soil OC and N storage (0-100 cm) was significantly lower in the younger grasslands (<20 yr), had increased in the older grasslands (30 yr), and at 30 years SOC had increased to pre-abandonment levels. For a thirty year period following abandonment the soil C/N value remained at 10. Our results indicate that soil C and TN were significantly and positively correlated, indicating that studies on the storage of soil OC and TN needs to focus on deeper soil and not be restricted to the uppermost (0-30 cm) soil levels. © 2013 Deng et al.

Cai Y.,Northwest University, China | Cai Y.,CAS Nanjing Institute of Geology and Palaeontology | Hua H.,Northwest University, China | Schiffbauer J.D.,University of Missouri | And 2 more authors.
Gondwana Research | Year: 2014

Cloudina are important Ediacaran index fossils, as they have a consistent terminal Neoproterozoic age and a worldwide distribution. The morphology of Cloudina has been reconstructed primarily on the basis of three-dimensionally preserved Chinese and Spanish specimens, but questions remain surrounding their phylogenetic placement. Understanding Cloudina paleoecology is an important aspect for the interpretation of these enigmatic organisms. Although their paleoecological dynamics remain unresolved, a possible "mat sticker" life mode has found support from recent taphonomic investigation of Paraguayan Cloudina specimens. Here, from analysis of fossil material from the upper part of the Ediacaran Dengying Formation (Gaojiashan and Lijiagou sections, Ningqiang area, southern Shaanxi Province, South China), we document complex tube growth patterns of Cloudina in addition to a close association of these fossils with preserved microbially induced sedimentary structures (specifically matgrounds). Sedimentological and taphonomic data of Cloudina-bearing carbonate sequences at the Gaojiashan section show a relationship between Cloudina and microbial mats, and further document erectly preserved Cloudina tubes. In conjunction with observations from the Paraguay material, the Dengying fossils described here provide supportive evidence for the paleoecological interpretation of Cloudina as inhabitants of a microbially bound carbonate substrate. The apical-most part of the tube (or cone) may have served as an attachment apparatus, situated within or beneath a microbial mat. Three-dimensionally phosphatized tubes of Cloudina from the Lijiagou section reveal that single tubes often have multiple growth orientations, which is demonstrated to have resulted from the curved growth of the tube walls (both cones and funnels). As these organisms exhibited a sessile, epibenthic life mode, the observed plasticity in growth direction and orientation may have been a competition-driven adaptation to ensure wider access to available food sources and potentially greater feeding efficiency. Although Cloudina have been found to co-occur in some deposits with biostromes and bioherms (e.g., stromatolites and thrombolites), sedimentological and taphonomic features of the Ningqiang Cloudina suggest that they inhabited a stratified carbonate substrate exhibiting matground features, but where biostromes and bioherms were absent. © 2013 International Association for Gondwana Research.

Qiao F.,Northwest University, China | Qiao F.,Karlsruhe Institute of Technology | Chang X.-L.,Karlsruhe Institute of Technology | Nick P.,Karlsruhe Institute of Technology
Journal of Experimental Botany | Year: 2010

The cytoskeleton undergoes dramatic reorganization during plant defence. This response is generally interpreted as part of the cellular repolarization establishing physical barriers against the invading pathogen. To gain insight into the functional significance of cytoskeletal responses for defence, two Vitis cell cultures that differ in their microtubular dynamics were used, and the cytoskeletal response to the elicitor Harpin in parallel to alkalinization of the medium as a fast response, and the activation of defence-related genes were followed. In one cell line derived from the grapevine cultivar 'Pinot Noir', microtubules contained mostly tyrosinylated α-tubulin, indicating high microtubular turnover, whereas in another cell line derived from the wild grapevine V. rupestris, the α-tubulin was strongly detyrosinated, indicating low microtubular turnover. The cortical microtubules were disrupted and actin filaments were bundled in both cell lines, but the responses were elevated in V. rupestris as compared with V. vinifera cv. 'Pinot Noir'. The cytoskeletal responsiveness correlated with elicitor-induced alkalinization and the expression of defence genes. Using resveratrol synthase and stilbene synthase as examples, it could be shown that pharmacological manipulation of microtubules could induce gene expression in the absence of elicitor. These findings are discussed with respect to a role for microtubules as positive regulators of defence-induced gene expression. © 2010 The Author(s).

Ren Y.,Shaanxi Normal University | Chang H.-L.,Northwest University, China | Endress P.K.,University of Zürich
Botanical Journal of the Linnean Society | Year: 2010

The floral development of two Clematis species and four Anemone species (including Pulsatilla) (Anemoneae, Ranunculaceae) is described. Shared features are: (1) sepals shortly after initiation broad, crescent-shaped, as opposed to the other organs, which are narrow and hemispherical; (2) outermost organs of the androecium often smaller than the others and sometimes sterile; (3) carpels ascidiate, with distinctive stalk, stigma papillate, decurrent; the carpels have one median fertile ovule and a few lateral sterile ovules in all species studied; the fertile ovule appears before the carpel closes. Generic differences are: (1) In Clematis, four sepals are initiated in two pairs; sometimes one of the sepals in the second pair appears to be divided into two organs (double position) resulting in a pentamerous perianth; the first eight stamens are positioned in two alternating whorls, the outer whorl alternating with the four sepals. In Anemone, the perianth organs, if five, are initiated in spiral sequence; in the Pulsatilla group of Anemone, six sepals are initiated in two whorls; the first three organs of the androecium (staminodes) alternate with the inner sepals. (2) Further androecial organs are mostly in complex whorls (i.e. including double positions) in Clematis, but in an irregular spiral or in irregular complex whorls in Anemone. (3) Anther maturation is largely centripetal in Clematis, but centrifugal or bidirectional in Anemone. In Clematis macropetala, the outermost organs of the androecium lack anthers and the filaments expand and become petal-like. In contrast, in the Pulsatilla group of Anemone, these organs retain sterile anthers and become small, capitate organs. © 2010 The Linnean Society of London.

Zhang S.,Northwest University, China | Sadras V.,SARDI Aquatic Sciences Center | Chen X.,China Agricultural University | Zhang F.,China Agricultural University
Field Crops Research | Year: 2013

Improvement of wheat water use efficiency (WUE = grain yield per unit seasonal evapotranspiration) in the dryland area of Loess Plateau of China is an imperative imposed by the critical situation of water resources, as well as by the demographic pressure. The aims of this study were (i) assessing WUE of dryland wheat in the Loess Plateau, and (ii) identifying management practices returning higher efficiencies. We compiled a data base of 39 sets of experiments spanning 20 years, where conventional practice was compared with alternatives including NT, no tillage without straw mulching; RT, reduced tillage without straw mulching; NTS, no tillage with straw mulching; SS, subsoiling with straw mulching; CTS, conventional tillage with straw mulching; PM, plastic film mulching 100%; RM, ridge mulched with plastic film + bare furrow; RMS, ridge mulched with plastic film + furrow mulched with crop straw.Yield ranged from 818 to 7900kgha-1 and WUE from 3.4 to 23.4kgha-1mm-1; the maximum yield and WUE were achieved under RM and RMS and the minimum under NT/RT. Practices had small and inconsistent effect on seasonal evapotranspiration, hence variation in both yield and WUE were attributable to changes in the contribution of soil evaporation to total evapotranspiration, and the partitioning of seasonal water use before and after anthesis. The yield-evapotranspiration relationship indicated that present yields are limited by environmental (e.g. seasonal distribution of rainfall) and management factors. The range of WUE is very large for the same or various practices, and thus offers tremendous opportunities for maintaining or increasing WUE. Implications for crop management and further improvement in yield and WUE are discussed. © 2013 Elsevier B.V.

Hao Y.,Northwest University, China | Hao Y.,Carnegie Institution of Washington | Oh E.,Carnegie Institution of Washington | Choi G.,KAIST | And 2 more authors.
Molecular Plant | Year: 2012

Phytochromes (Phy) and phytochrome-interacting factor (PIF) transcription factors constitute a major signaling module that controls plant development in response to red and far-red light. A low red:far-red ratio is interpreted as shading by neighbor plants and induces cell elongation - a phenomenon called shade-avoidance syndrome (SAS). PAR1 and its closest homolog PAR2 are negative regulators of SAS; they belong to the HLH transcription factor family that lacks a typical basic domain required for DNA binding, and they are believed to regulate gene expressions through DNA binding transcription factors that are yet to be identified. Here, we show that light signal stabilizes PAR1 protein and PAR1 interacts with PIF4 and inhibits PIF4-mediated gene activation. DNA pull-down and chromatin immunoprecipitation (ChIP) assays showed that PAR1 inhibits PIF4 DNA binding in vitro and in vivo. Transgenic plants overexpressing PAR1 (PAR1OX) are insensitive to gibberellin (GA) or high temperature in hypocotyl elongation, similarly to the pifq mutant. In addition to PIF4, PAR1 also interacts with PRE1, a HLH transcription factor activated by brassinosteroid (BR) and GA. Overexpression of PRE1 largely suppressed the dwarf phenotype of PAR1OX. These results indicate that PAR1-PRE1 and PAR1-PIF4 heterodimers form a complex HLH/bHLH network regulating cell elongation and plant development in response to light and hormones. © 2012 The Author.

He M.,Shaanxi Normal University | Wang Y.,Northwest University, China | Hua W.,Shaanxi Institute of Education | Zhang Y.,Shaanxi Normal University | Wang Z.,Shaanxi Normal University
PLoS ONE | Year: 2012

Background: Hypericum perforatum L. (St. John's wort) is a medicinal plant with pharmacological properties that are antidepressant, anti-inflammatory, antiviral, anti-cancer, and antibacterial. Its major active metabolites are hypericins, hyperforins, and melatonin. However, little genetic information is available for this species, especially that concerning the biosynthetic pathways for active ingredients. Methodology/Principal Findings: Using de novo transcriptome analysis, we obtained 59,184 unigenes covering the entire life cycle of these plants. In all, 40,813 unigenes (68.86%) were annotated and 2,359 were assigned to secondary metabolic pathways. Among them, 260 unigenes are involved in the production of hypericin, hyperforin, and melatonin. Another 2,291 unigenes are classified as potential Type III polyketide synthase. Our BlastX search against the AGRIS database reveals 1,772 unigenes that are homologous to 47 known Arabidopsis transcription factor families. Further analysis shows that 10.61% (6,277) of these unigenes contain 7,643 SSRs. Conclusion: We have identified a set of putative genes involved in several secondary metabolism pathways, especially those related to the synthesis of its active ingredients. Our results will serve as an important platform for public information about gene expression, genomics, and functional genomics in H. perforatum. © 2012 He et al.

Li D.-S.,China Three Gorges University | Li D.-S.,Nanjing University | Zhao J.,China Three Gorges University | Wu Y.-P.,China Three Gorges University | And 4 more authors.
Inorganic Chemistry | Year: 2013

Two novel Co(II)-cluster-based coordination polymers - namely, [Co 5(μ3-OH)2(1,4-ndc)4(bix) 2]n (1) and {[Co8(μ3-OH) 4(1,4-ndc)6(btp)(H2O)6] ·H2O}n (2) - were prepared by hydrothermal reactions of Co(II) perchlorate with 1,4-naphthalenedicarboxylic acid (1,4-H2ndc) and different N-donor coligands (bix = 1,4-bis(imidazol-1-ylmethyl)benzene and btp = 4,4′-bis(triazol-1-ylmethyl) biphenyl). In 1, 10-connected [Co5(μ3-OH) 2(COO)8] clusters are extended by the μ4-1, 4-ndc2- and trans-bix ligands to construct a rare, self-penetrating ile framework that can interestingly be regarded as the cross-link of two interpenetrating 6-connected pcu networks. While for 2, [Co8(μ 3-OH)4(COO)12] clusters serve as the 8-connected nodes, which are bridged by the μ4/μ5-1, 4-ndc2- and trans-btp ligands to afford the highest-connected uninodal self-penetrating (420.68) network based on octacobalt clusters. A synthetic and structural comparison of 1 and 2 demonstrates that the features of auxiliary N-donor ligands play a key role in governing the in situ formed clusters and the final 3-D coordination frameworks. Magnetic susceptibility measurements indicate that complex 1 shows an antiferromagnetic interaction between the adjacent Co(II) ions, whereas 2 displays the dominant antiferromagnetic exchanges in 300-50 K and a ferrimagnetic-like behavior at lower temperatures. © 2013 American Chemical Society.

Xu Y.,Northwest University, China | Li B.,Shaanxi Normal University | Xiao L.,Northwest University, China | Ouyang J.,Northwestern Polytechnical University | And 2 more authors.
Chemical Communications | Year: 2014

A dual-channel including a colorimetric and fluorescent probe based on the aggregation-caused quenching (ACQ) and enzymolysis approach has been presented to screen acid phosphatase (ACP) and its inhibitor. Moreover, the ACP activity was determined by real time assay. © 2014 the Partner Organisations.

Li Y.,Northwest University, China | Huang C.,Northwest University, China | Zheng J.,Northwest University, China | Qi H.,Shaanxi Normal University
Biosensors and Bioelectronics | Year: 2012

A novel electrogenerated chemiluminescence (ECL) biosensing method for highly sensitive detection of DNA methylation and assay of the CpG methyltransferase (M. SssI) activity was developed on basis of enzyme-linkage reactions and ruthenium complex served as an ECL tag. The ECL biosensing electrode was fabricated by self-assembling 5'-thiol modified 32-mer single-strand DNA (ss-DNA)-tagged with ruthenium bis (2,2'-bipyridine) (2,2'-bipyridine-4,4'-dicarboxylic acid)-ethylenediamine on the surface of a gold electrode, and then hybridized with complementary ss-DNA to form duplex DNA (ds-DNA). When M. SssI and S-adenosylmethionine were introduced, all cytosine residues within 5'-CG-3' of ds-DNA on the biosensing electrode were methylated. After the methylated biosensing electrode was treated by HpaII endonuclease, the un-methylated cytosines were cleaved, thus led to decrease ECL signal. The ECL intensity of ECL biosensing electrode is related to the methylation level and M. SssI activity in a fixed concentration HpaII endonuclease. The increased ECL intensity was direct proportion to M. SssI activity in the range from 0.05 to 100. U/mL with a detection limit of 0.02. U/mL. This work demonstrates that the combination of the enzyme-linkage reactions with a highly sensitive ECL technique is a great promising approach for the detection of DNA methylation level, assay of the activity of MTase, and evaluation of the capability of inhibitors for the methyltransferase. © 2012 Elsevier B.V.

Zhang N.,Northwest University, China | Lee S.J.,Pohang University of Science and Technology | Chen T.-G.,Dalian University of Technology
Geomorphology | Year: 2015

Trajectories of aeolian sand particles behind a porous wind fence embedded in a simulated atmospheric boundary layer were visualized experimentally, to investigate the shelter effect of the fence on sand saltation. Two sand samples, one collected from a beach (d. =. 250. μm) and the other from a desert (d. =. 100. μm), were tested in comparison with the previous studies of a 'no-fence' case. A wind fence (. ε=. 38.5%) was installed on a flat sand bed filled with each sand sample. A high-speed photography technique and the particle tracking velocimetry (PTV) method were employed to reconstruct the trajectories of particles saltating behind the fence. The collision processes of these sand particles were analyzed, momentum and kinetic energy transfer between saltating particles and ground surface were also investigated. In the wake region, probability density distributions of the impact velocities agree well with the pattern of no-fence case, and can be explained by a log-normal law. The horizontal component of impact velocity for the beach sand is decreased by about 54%, and about 76% for the desert sand. Vertical restitution coefficients of bouncing particles are smaller than 1.0 due to the presence of the wind fence. The saltating particles lose a large proportion of their energy during the collision process. These results illustrate that the porous wind fence effectively abates the further evolution of saltating sand particles. © 2014 Elsevier B.V.

Yang H.Z.,Northwest University, China | Qiao X.G.,Northwest University, China | Das S.,Indian Central Glass and Ceramic Research Institute | Paul M.C.,Indian Central Glass and Ceramic Research Institute
Optics Letters | Year: 2014

The work demonstrates for the first time a thermal regenerated grating (RG) operating at an ultra-high temperature up to 1400°C. A new class of photosensitive optical fiber based on erbium-doped yttrium stabilized zirconiacalcium- alumina-phospho silica (Er-YZCAPS) glass is fabricated using modified chemical vapor deposition (MCVD) process, followed by solution doping technique and conventional fiber drawing. A type-I seed grating inscribed in this fiber is thermal regenerated based on the conventional thermal annealing technique. The investigation result indicates that the produced RG has an ultrahigh temperature sustainability up to 1400°C. The measured temperature sensitivities are 14.1 and 15.1 pm/°C for the temperature ranges of 25°C-1000°C and 1000°C-1400°C, respectively. © 2014 Optical Society of America.

Liu J.-Q.,Guangdong Medical College | Wang Y.-Y.,Northwest University, China | Batten S.R.,Monash University | Sakiyama H.,Yamagata University | Ma D.-Y.,Zhaoqing University
Inorganic Chemistry Communications | Year: 2012

The synthesis, structure and magnetic property of a new coordination network {[Co 2(bcp) 2(bpt) 2]•2H 2O} n (1) (H 2bcp = 1,3-bis(4-carboxy-phenoxy) propane and bpt = 2,5-bis(4-pyridyl)-1,3,4-thiadiazole), is reported. Complex 1 shows a 3D 4 8.6 6.8 topology with unusual self-penetration, in which represents a new example of 6-connected networks. In addition, the magnetic property of 1 has also been investigated. © 2012 Elsevier B.V. All rights reserved.

Wang W.,Northwest University, China | Zhao Y.,Xiamen University
Physical Chemistry Chemical Physics | Year: 2014

The dissociation and recombination rates of physisorbed H2, and the total dissociation rate of gas phase H2 on the rigid Ni(100) surface, as well as the corresponding kinetic isotope effects, are calculated by using the quantum instanton method, together with path integral Monte Carlo and adaptive umbrella sampling techniques. Both the dissociation and recombination rates of physisorbed H2 are dramatically enhanced by the quantum motions of H2 at low temperatures, for instance, the quantum rates are 43 and 7.5 times larger than the classical ones at 200 K, respectively. For the dissociation of gas phase H2, at high temperatures, the H 2 can fly over the physisorbed state and dissociate directly, however, at low temperatures, the H2 is first physisorbed and then dissociates under steady state approximation. The total dissociation rate of gas phase H2 can be expressed as a combination of the direct and steady state dissociation rates. It has the form of an inverted bell with a minimum value at about 400 K, and detailed analysis shows that the dissociation of gas phase H2 is dominated by a steady state process below 400 K, however, both the steady state and direct processes are important above 400 K. The calculated kinetic isotope effects reveal that H2 always has larger rates than D2 no matter which dissociative process they undergo. © 2014 The Owner Societies.

Qu C.,Ningbo University | Zhang Y.,Tianshui Normal University | Liu X.,Northwest University, China | Liu Y.,University of Texas at Arlington
Archive for Rational Mechanics and Analysis | Year: 2014

In this paper, we study the orbital stability of the periodic peaked solitons of the generalized μ-Camassa-Holm equation with nonlocal cubic and quadratic nonlinearities. The equation is a μ-version of a linear combination of the Camassa-Holm equation and the modified Camassa-Holm equation. It is also integrable with the Lax-pair and bi-Hamiltonian structure and admits the single peakons and multi-peakons. By constructing an inequality related to the maximum and minimum of solutions with the conservation laws, we prove that, even in the case that the Camassa-Holm energy counteracts in part the modified Camassa-Holm energy, the shapes of periodic peakons are still orbitally stable under small perturbations in the energy space. © 2013 Springer-Verlag Berlin Heidelberg.

Li P.,Northwest University, China | Li P.,Cornell University | Ma F.,Northwest University, China | Cheng L.,Cornell University
Physiologia Plantarum | Year: 2013

The metabolism of carbohydrates, organic acids, amino acids and phenolics was compared between the sun-exposed peel and the shaded peel of apple fruit. Contents of sorbitol and glucose were higher in the sun-exposed peel, whereas those of sucrose and fructose were almost the same in the two peel types. This was related to lower sorbitol dehydrogenase activity and higher activities of sorbitol oxidase, neutral invertase and acid invertase in the sun-exposed peel. The lower starch content in the sun-exposed peel was related to lower sucrose synthase activity early in fruit development. Dark respiratory metabolism in the sun-exposed peel was enhanced by the high peel temperature due to high light exposure. Activities of most enzymes in respiratory metabolism were higher in the sun-exposed peel, but the concentrations of most organic acids were relatively stable, except pyruvate and oxaloacetate. Due to the different availability of carbon skeletons from dark respiration in the two peel types, amino acids with higher C/N ratios are accumulated in the sun-exposed peel whereas those with lower C/N ratios are accumulated in the shaded peel. Contents of anthocyanins and flavonols and activities of phenylalanine ammonia-lyase, UDP-galactose:flavonoid 3-O-glucosyltransferase and several other enzymes were higher in the sun-exposed peel than in the shaded peel, indicating the entire phenylpropanoid pathway is upregulated in the sun-exposed peel. Comprehensive analyses of the metabolites and activities of enzymes involved in primary metabolism and secondary metabolism have allowed us to gain a full picture of the metabolic network in the two peel types under natural light exposure. © Physiologia Plantarum 2012.

Wang P.,Northwest University, China | Sun X.,Northwest University, China | Wang N.,Northwest University, China | Tan D.-X.,University of Texas Health Science Center at San Antonio | Ma F.,Northwest University, China
Journal of Pineal Research | Year: 2015

The beneficial effect that melatonin has against mitochondrial dysfunctioning seems to be linked to mitophagy. Roles for melatonin have been demonstrated in promoting health and preventing disease, as well as activating the process of autophagy in general. However, no reports have been made about how the application of melatonin regulates that process when plants are exposed to oxidative stress. We investigated the influence of different concentrations of melatonin (0.0, 0.5, 5.0, 10.0, or 50.0 μm) on autophagy under methyl viologen (MV)-induced oxidative stress. Arabidopsis seedlings that were pretreated with 5 or 10 μm melatonin underwent relatively strong induction of autophagy, as evidenced by the number of monodansylcadaverine (MDC)-stained autophagosomes in root samples. Pretreatment with 10 μm melatonin also alleviated MV-induced photo-oxidation damage and significantly reduced the accumulation of oxidized proteins. Those responses might have been due to the strong upregulation of genes that involved in AtATG8-PE conjugation pathway, which enhanced the capacity for autophagy. Histochemical staining revealed that both O2-· and H2O2 were highly accumulated upon MV exposure, although the response did not differ significantly between control and melatonin-pretreated seedlings. By contrast, exogenous melatonin upregulated the expression of two genes for H2O2-scavenging enzymes, that is, AtAPX1 and AtCATs. The activation of autophagy by melatonin without an alteration in ROS production may be part of a survival mechanism that is enhanced by melatonin after cellular damage. Therefore, it represents a second level of defense to remove damaged proteins when antioxidant activities are compromised. © 2015 John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

Alleviating the urban heat-island effect (UHI) is one of the important means to meet energy conservation and pollution reduction targets by demand side. Rational architectural layout and landscape design are significant measures to achieve building energy efficiency and sustainable building. In this study, the effects of building layout patterns and trees arrangement on the outdoor wind environment and thermal comfort at the pedestrian level were investigated by using Simulation Platform for Outdoor Thermal Environment (SPOTE). The conclusions were summarized as follows: 1) it has been found that trees arrangement, buildings layout patterns and their orientations with respect to wind have significant effects on the outdoor wind environment and pedestrian level thermal comfort. The long facades of building, which are parallel to the prevailing wind direction, can accelerate horizontal vortex airflow at the edges and obtain pleasant thermal comfort and wind environment at pedestrian level. 2) Configurations that contain a square central space articulated by buildings and oriented toward the prevailing wind can offer better exposure to air currents as a result of attenuated revised standard effective temperature (SET*). Such configurations are regarded as the optimum building layout patterns and trees arrangement. © 2014 Elsevier Ltd.

Deng F.,CAS Shanghai Institute of Materia Medica | Liu H.-Y.,Northwest University, China
Synthetic Communications | Year: 2012

A chiral bifunctional organocatalyst using sulfamide as novel type of hydrogen bonding donor has been developed. This catalyst was found to efficiently catalyze the Michael addition of cyclic ketones to nitroolefins in water, and the products were obtained in good yield (up to 97%), and excellent diastereoselectivities (up to >50:1) and enantioselectivities (up to 96%). © Taylor & Francis Group, LLC.

Zhang H.-F.,Northwest University, China | Zhang H.-F.,CAS Institute of Geology and Geophysics | Yang Y.-H.,CAS Institute of Geology and Geophysics | Santosh M.,Kochi University | And 3 more authors.
Gondwana Research | Year: 2012

We report U-Pb ages and Hf isotopes of zircons in granulites from two continental suture zones in the North China Craton (NCC)-from granulite xenoliths entrained in the Cenozoic Hannuoba basalts within the Trans-North China Orogen (TNCO) that amalgamates the Western and Eastern Blocks, and from a mafic granulite associated with ultrahigh-temperature (UHT) granulites within the Inner Mongolia Suture Zone (IMSZ) that welds the Yinshan and Ordos Blocks. The zircons in these rocks, together with the inherited zircons from Mesozoic subalkalic intrusives of these regions, show several distinct U-Pb age populations and provide constraints on the evolution of the lower crust beneath the NCC. Parts of the older zircons from the TNCO yield discordant data that project to ages of about 2.5 to 2.7Ga. These old zircons show Hf T DM model ages of 2.6-2.9Ga suggesting the existence of Archean lower crust beneath the TNCO, which is coupled with the Neoarchean metamorphic basement and greenstone belt. A major zircon population grew at 1.75-2.0Ga, consistent with the timing of the Paleoproterozoic collision between the various crustal blocks within the NCC, suggesting that this event had a significant effect on the Archean lower crust. The older inherited zircons from the Western Block also yield discordant data that project to younger ages of about 1.8 to 1.9Ga. This age is consistent with the timing of intrusion of the mafic magmatic protoliths of the granulites associated with the UHT rocks in the khondalite belt within the IMSZ. These older zircons yield Hf T DM model ages of 2.0-2.5Ga suggesting that the lower crust beneath the Western Block in the NCC to be dominantly Paleoproterozoic, and decoupled with the Archean metamorphic basement of the region. Yet another population of zircons from the Hannuoba banded granulite xenoliths, garnet-bearing pyroxenite cumulate and dark pyroxenite xenoliths yield a large spread of Phanerozoic concordant ages ranging from 470Ma to 40Ma with peaks at 315Ma, 220-230Ma, 120Ma and 46Ma. The Late Paleozoic zircons predominantly occur in the garnet-bearing pyroxenite xenoliths and yield variable εHf(t) values of -24 to +18. Triassic-Cretaceous zircons mainly occur in the banded granulite xenoliths and yield highly variable εHf(t) values, ranging from -48 to +16. The Tertiary zircons occur only in the dark pyroxenite xenoliths and show a restricted εHf(t) with a dominant range from 0 to +18. These data suggest episodic magmatic underplating in the ancient lower crust of the NCC, lasting continuously throughout Phanerozoic, producing zircons from the underplated magmas or providing the heat source for the recrystallization of zircons from the ancient crust. Our data clearly demonstrate the important events of Phanerozoic magmatic underplating beneath the Neoarchean-Paleoproterozoic crust of the NCC. © 2011 International Association for Gondwana Research.

Xie X.-T.,Chinese University of Hong Kong | Xie X.-T.,Northwest University, China | Zhu B.-F.,Tsinghua University | Liu R.-B.,Chinese University of Hong Kong
New Journal of Physics | Year: 2013

We theoretically investigate the effects of the excitation frequency on the plateau of high-order terahertz sideband generation (HSG) in semiconductors driven by intense terahertz (THz) fields. We find that the plateau of the sideband spectrum strongly depends on the detuning between the near-infrared laser field and the band gap. We use the quantum trajectory theory (three-step model) to understand the HSG. In the three-step model, an electron-hole pair is first excited by a weak laser, then driven by the strong THz field, and finally recombined to emit a photon with energy gain. When the laser is tuned below the band gap (negative detuning), the electron-hole generation is a virtual process that requires quantum tunneling to occur. When the energy gained by the electron-hole pair from the THz field is less than 3.17 times the ponderomotive energy (Up), the electron and the hole can be driven to the same position and recombined without quantum tunneling, so that the HSG will have large probability amplitude. This leads to a plateau feature of the HSG spectrum with a high-frequency cutoff at about 3.17Up above the band gap. Such a plateau feature is similar to the case of high-order harmonics generation in atoms where electrons have to overcome the binding energy to escape the atomic core. A particularly interesting excitation condition in HSG is that the laser can be tuned above the band gap (positive detuning), corresponding to the unphysical 'negative' binding energy in atoms for high-order harmonic generation. Now the electron-hole pair is generated by real excitation, but the recombination process can be real or virtual depending on the energy gained from the THz field, which determines the plateau feature in HSG. Both the numerical calculation and the quantum trajectory analysis reveal that for positive detuning, the HSG plateau cutoff depends on the frequency of the excitation laser. In particular, when the laser is tuned more than 3.17Up above the band gap, the HSG spectrum presents no plateau feature but instead sharp peaks near the band edge and near the excitation frequency. © IOP Publishing and Deutsche Physikalische Gesellschaft.

Zhai M.,Northwest University, China | Zhai M.,CAS Institute of Geology and Geophysics | Santosh M.,China University of Geosciences | Santosh M.,Kochi University
Gondwana Research | Year: 2013

The North China Craton (NCC) has experienced a complex geological evolution since the early Precambrian, and carries important records of secular changes in tectonics and metallogeny. Here we synthesize the salient geological and tectonic features of the evolution and destruction of the NCC vis-à-vis major metallogenic events, and the formation of potential ore deposits. We identify a close relationship between the major geological events in the NCC and those reported elsewhere on the globe. We trace the records of a regular change in the pattern of metallogeny, mineral deposit character, spatial distribution and genetic mechanisms, which closely match the timing and styles of the major geological and tectonic events in this craton.The NCC went through five major tectonic cycles: (1) Neoarchean crustal growth and stabilization, (2) Paleoproterozoic rifting-subduction-accretion-collision with imprints of the Great Oxidation Event (GOE), (3) Late Paleoproterozoic-Neoproterozoic multi-stage rifting, (4) Paleozoic orogenesis at the margins of the craton, and (5) Mesozoic extensional tectonics associated with lithospheric thinning and decratonization. Coinciding with these major geological events are five major metallogenic systems identified as follows: (1) an Archean BIF system, (2) Paleoproterozoic Cu-Pb-Zn and Mg-B systems, (3) a Mesoproterozoic REE-Fe-Pb-Zn system, (4) a Paleozoic orogenic Cu-Mo system, and (5) Mesozoic intracontinental Au and Ag-Pb-Zn and Mo systems. The ore-deposit types in each of these metallogenic systems show distinct characteristics and tectonic affinities.From Early Precambrian through Late Precambrian to Paleozoic and Mesozoic, the NCC records a transition from primitive- to modern-style plate tectonics. Evidence for imbricated oceanic plate stratigraphy in a subduction-accretion setting, and collisional orogenesis along at least three major zones of ocean closure are documented. Major transitions in tectonic style and surface environmental changes recorded in other parts of the world are also reflected in the geological history and metallogenic events in the NCC. Large-scale gold deposits formed through intraplate tectonics during the Mesozoic provide important insights into mantle dynamics and crust-mantle interaction associated with lithospheric thinning and craton destruction. The NCC provides one of the best examples for documenting secular changes in the geological history and metallogenic epochs of an evolving Earth. © 2013 International Association for Gondwana Research.

Hou L.,Sun Yat Sen University | Hou L.,Northwest University, China | Zhang W.-X.,Sun Yat Sen University | Zhang J.-P.,Sun Yat Sen University | And 3 more authors.
Chemical Communications | Year: 2010

Solvothermal reaction of CoSO4 with 2,6-di-p-carboxyphenyl-4, 4′-bipyridine affords a novel, octacobalt cluster based, (3,12)-connected porous framework, which exhibits gas sorption and spin-glassy magnetic behaviour. © 2010 The Royal Society of Chemistry.

Peng C.,Northwest University, China | Peng C.,Aix - Marseille University | Peng C.,University of Quebec at Montréal | Guiot J.,Aix - Marseille University | And 4 more authors.
Ecology Letters | Year: 2011

It is increasingly being recognized that global ecological research requires novel methods and strategies in which to combine process-based ecological models and data in cohesive, systematic ways. Model-data fusion (MDF) is an emerging area of research in ecology and palaeoecology. It provides a new quantitative approach that offers a high level of empirical constraint over model predictions based on observations using inverse modelling and data assimilation (DA) techniques. Increasing demands to integrate model and data methods in the past decade has led to MDF utilization in palaeoecology, ecology and earth system sciences. This paper reviews key features and principles of MDF and highlights different approaches with regards to DA. After providing a critical evaluation of the numerous benefits of MDF and its current applications in palaeoecology (i.e. palaeoclimatic reconstruction, palaeovegetation and palaeocarbon storage) and ecology (i.e. parameter and uncertainty estimation, model error identification, remote sensing and ecological forecasting), the paper discusses method limitations, current challenges and future research direction. In the ongoing data-rich era of today's world, MDF could become an important diagnostic and prognostic tool in which to improve our understanding of ecological processes while testing ecological theory and hypotheses and forecasting changes in ecosystem structure, function and services. © 2011 Blackwell Publishing Ltd/CNRS.

Andriantahina F.,Northwest University, China | Liu X.,Northwest University, China | Feng T.,Soochow University of China | Xiang J.,CAS Qingdao Institute of Oceanology
Marine Biotechnology | Year: 2013

At present, research and progress in shrimp genomics and genetics show significant developments. Shrimp genetics and genomics also show immense potential for an increased production in a way that meets shrimp culture progress goals for the third millennium. This review article aims to provide an overview of its current status and future direction, discusses questions that need focused research to address them, and summarizes areas where genetics and genomics knowledge can make a positive difference to shrimp culture sustainability. Sustainable progress of penaeid shrimps will depend upon feasible solutions for environmental, research, economic, consumer problems, proper development, and planning policy enforcement. It is recommended that increased funding for biotechnology research and progress be directed to expand worldwide commercial shrimp culture and address environmental and public health issues. For any researcher or shrimp company member who has attempted to or whom would like to thoroughly search the literature to gain a complete understanding of the current state of shrimp genetics and genomics, this publication will be an invaluable source of reference materials, some of which is reported here for the first time. © 2013 Springer Science+Business Media New York.

Wang J.-G.,Northwest University, China | Wang J.-G.,Tsinghua University | Yang Y.,Tsinghua University | Huang Z.-H.,Tsinghua University | Kang F.,Tsinghua University
Electrochimica Acta | Year: 2014

A novel MnO2/polypyrrole (PPy) heterogeneous composite with nanotubular structure is reported by a facile preparation of in situ chemical polymerization via a reactive template of MnO2. MnO2 nanotubes are found to be served as both appropriate oxidants and scaffolds to polymerize conducting PPy nanocoatings on the surface, thus constructing a unique coaxial configuration. The electrochemical measurements show that both components in the hybrid nanocomposites exhibit highly pseudocapacitive behavior in neutral KCl aqueous electrolyte. MnO2/PPy nanocomposites prepared from an initial MnO2/pyrrole ratio (3:1) deliver a maximum specific capacitance of 337 F g-1 at 0.5 A g-1 with good rate capability and long-term cycling stability, demonstrating their promising applications in high-performance supercapacitors. Moreover, the synthetic methodology may provide a generic guideline in developing different nanostructured MnO2/PPy electrode materials for electrochemical energy storage. © 2014 Elsevier Ltd.

Zheng L.,Xi'an Shiyou University | Song J.-F.,Xi'an Shiyou University | Song J.-F.,Northwest University, China
Journal of Applied Electrochemistry | Year: 2011

A modified electrode, nickel(II)-morin complex modified multi-wall carbon nanotube paste electrode (Ni(II)-MR-MWCNT-PE), has been fabricated by electrodepositing Ni(II)-MR complex on the surface of MWCNTPE in alkaline solution. The Ni(II)-MR-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)-MR complex modified carbon paste electrode (CPE). It also shows better electrocatalytic activity toward the oxidation of hydroxylamine than the Ni(II) modified MWCNT-PE (Ni(II)-MWCNT-PE) and Ni(II)-MR-CPE. Kinetic parameters such as the electron transfer coefficient αa, rate constant ks of the electrode reaction and the catalytic rate constant k cat of the catalytic reaction are determined. Moreover, the catalytic currents present linear dependence on the concentration of hydroxylamine from 2.5 × 10-6 to 4.0 × 10-4 mol L-1 by amperometry. The detection limit and sensitivity are 8.0 × 10 -7 mol L-1 and 56.2 mA L mol-1, respectively. The modified electrode for hydroxylamine determination is of the property of simple preparation, good stability, fast response and high sensitivity. © Springer Science+Business Media B.V. 2010.

Wang W.,Northwest University, China | Zhao Y.,Xiamen University
Journal of Physical Chemistry C | Year: 2013

The rate constants and kinetic isotope effects of H2 dissociation and recombination on Ni(100) surface are calculated by using the quantum instanton method, together with path integral Monte Carlo and adaptive umbrella sampling techniques. The Ni(100) surface model containing 104 nickel atoms and the potential energy surface based on the embedded diatomics in molecules are used. For the H2 dissociation, the results on the rigid lattice are consistent with experimental data. Compared to the rigid lattice, the classical and quantum motions of the lattice further enhance the dissociation rates by 18 and 49% at 300 K. The calculated kinetic isotope effects show that the H2 always has the largest rate, while the D2 has the smallest one. For the H2 recombination, however, the effects of lattice motions on the rates are different from those for the dissociation, that is, compared to the rigid lattice, both the classical and quantum motions of the lattice lower the recombination rates. The possible mechanism is analyzed by the corresponding free energy profiles. © 2013 American Chemical Society.

Bian L.,Northwest University, China | Ji X.,Northwest University, China | Hu W.,Shaanxi Provincial Peoples Hospital
Journal of Agricultural and Food Chemistry | Year: 2014

Due to the high toxicity of silver(I) ions, a method for the rapid, sensitive, and selective detection for silver(I) ions in water, pharmaceutical products, and food is of great importance. Herein, a novel single-labeled fluorescent oligonucleotide (OND) probe based on cytosine-Ag(I)-cytosine coordination and the inherent fluorescence quenching ability of the G-quadruplex is designed to detect silver(I) ions. The formation of a hairpin structure in the OND-Ag(I) complex brings the hexachloro fluorescein (HEX) labeled at the 5-end of the OND probe close to the G-quadruplex located at the 3-end of the OND probe, leading to a fluorescence quenching due to photoinduced electron transfer between HEX and the G-quadruplex. Through this method, silver(I) ions can be detected quantitatively, the linear response range is from 1 to 100 nmol/L with a detection limit of 50 pmol/L, and no obvious interference occurs with other metal ions with a 10-fold concentration. This assay is simple, sensitive, and selective, and it can be used to detect silver(I) ions in actual water, drug, and food samples. © 2014 American Chemical Society.

Zhang H.-F.,CAS Institute of Geology and Geophysics | Zhang H.-F.,Northwest University, China | Zhu R.-X.,CAS Institute of Geology and Geophysics | Santosh M.,Kochi University | And 3 more authors.
Gondwana Research | Year: 2013

A comprehensive synthesis of U-Pb geochronology and Hf isotopes of zircons from granulite/pyroxenite xenoliths entrained in Phanerozoic magmatic rocks and inherited xenocrysts from the associated lower crust rocks from various domains of the North China Craton (NCC) provides new insights into understanding the Phanerozoic evolution of the lower crust in this craton. Episodic widespread magma underplating into the ancient lower crust during Phanerozoic has been identified throughout the NCC from early Paleozoic to Cenozoic, broadly corresponding to the Caledonian, Hercynian, Indosinian, Yanshanian, and Himalayan orogenies on the circum-craton mobile belts. The early Paleozoic (410-490. Ma) ages come from xenoliths in the northern and southern margins as well as the central domain of the Eastern Block of the craton which mark the first phase of Phanerozoic magma underplating since the final cratonization of the NCC in the Paleoproterozoic. The magmatism coincided with the northward subduction of the Paleotethysian Ocean in the south and the southward subduction of the Paleoasian Ocean in the north. The subduction not only triggered magma underplating but also led to the emplacement of the diamondiferous kimberlites on the craton, marking the initiation of decratonization. The late Paleozoic event as represented by the 315. Ma garnet pyroxenite and/or lherzolite xenoliths in Hannuoba was restricted to the northern and southern margins of the craton, correlating with the arc magmatism continuous associated with the subduction of the Paleotethysian and Paleoasian Oceans and resulting in the interaction between the melts from subducted slabs and the lithospheric mantle/lower crust. The early Mesozoic event also dominantly occurred in the northern and southern margins and was related with the final closure of the Paleotethysian and Paleoasian Oceans as well as the collisional orogeny between the NCC and the Yangtze Craton. The late Mesozoic (ca. 120. Ma) was a major and widespread magmatic event which manifested throughout the NCC, associated with the geothermal overturn due to the giant south Pacific mantle plume. The Cenozoic magmatism, identified only in the dark clinopyroxenite xenoliths in the Hannuoba, was probably induced by the Himalayan movement in eastern Asia and might also have been influenced by the subduction of the Pacific Ocean to some extent. These widespread and episodic magma underplating or rejuvenation of the ancient lower crust beneath the NCC revealed by U-Pb and Hf isotope data resulted from the corresponding addition of juvenile materials from mantle to lower crust, with a mixing of the old crust with melts. The process inevitably resulted in the compositional modification of the ancient lower crust, similar to the compositional transformation from the refractory lithospheric mantle to a fertile one through the refractory peridotite - infiltrated melt reaction as revealed in the lithospheric mantle beneath the craton. © 2012 International Association for Gondwana Research.

Hui J.,Northwest University, China | Hui J.,Tsinghua University | Wang X.,Tsinghua University
Inorganic Chemistry Frontiers | Year: 2014

Hydroxyapatite (HAp) nanocrystals with excellent biocompatibility and bioresorbability are usually used in the fields of tissue engineering, medicine, etc. In this review, recent advances in the tunable synthesis, ion doping, assembly and applications of monodisperse HAp nanocrystals are summarized, which may be helpful for the designed synthesis and surface modification of HAp or other nanocrystals according to practical applications. This journal is © the Partner Organisations 2014.

Zhang Q.,University of Delaware | Scrafford K.,University of Delaware | Li M.,University of North Texas | Cao Z.,University of Delaware | And 4 more authors.
Nano Letters | Year: 2014

Substantial differences in charge storage mechanisms exist between dielectric capacitors (DCs) and electrochemical capacitors (ECs), resulting in orders of magnitude difference of stored charge density in them. However, if ionic diffusion, the major charge transport mechanism in ECs, is confined within nanoscale dimensions, the Helmholtz layers and diffusion layers will overlap, resulting in dismissible ionic diffusion. An interesting contradiction between appreciable energy density and unrecognizable ionic diffusion is observed in solid-state capacitors made from reduced graphene oxide films that challenge the fundamental charge storage mechanisms proposed in such devices. A new capacitive model is proposed, which combines the two distinct charge storage mechanisms of DCs and ECs, to explain the contradiction, of high storage capacity yet undetectable ionic diffusion, seen in graphene oxide based supercapacitors. © 2014 American Chemical Society.

Wang F.,Northwest University, China | Yang H.,Tsinghua University | Fu H.,Tsinghua University | Pei Z.,Northwest University, China
Chemical Communications | Year: 2013

A novel and efficient copper-catalyzed Michael addition of acrylic derivatives with primary alcohols in the presence of base has been developed. The protocol uses readily available acrylic derivatives and primary alcohols as the starting materials, inexpensive CuCl2 as the catalyst, and the corresponding addition products were obtained in moderate to excellent yields. © 2013 The Royal Society of Chemistry.

Li M.,Northwest University, China | Li M.,Cornell University | Feng F.,Northwest University, China | Feng F.,Cornell University | Cheng L.,Cornell University
PLoS ONE | Year: 2012

Both sorbitol and sucrose are imported into apple fruit from leaves. The metabolism of sorbitol and sucrose fuels fruit growth and development, and accumulation of sugars in fruit is central to the edible quality of apple. However, our understanding of the mechanisms controlling sugar metabolism and accumulation in apple remains quite limited. We identified members of various gene families encoding key enzymes or transporters involved in sugar metabolism and accumulation in apple fruit using homology searches and comparison of their expression patterns in different tissues, and analyzed the relationship of their transcripts with enzyme activities and sugar accumulation during fruit development. At the early stage of fruit development, the transcript levels of sorbitol dehydrogenase, cell wall invertase, neutral invertase, sucrose synthase, fructokinase and hexokinase are high, and the resulting high enzyme activities are responsible for the rapid utilization of the imported sorbitol and sucrose for fruit growth, with low levels of sugar accumulation. As the fruit continues to grow due to cell expansion, the transcript levels and activities of these enzymes are down-regulated, with concomitant accumulation of fructose and elevated transcript levels of tonoplast monosaccharide transporters (TMTs), MdTMT1 and MdTMT2; the excess carbon is converted into starch. At the late stage of fruit development, sucrose accumulation is enhanced, consistent with the elevated expression of sucrose-phosphate synthase (SPS), MdSPS5 and MdSPS6, and an increase in its total activity. Our data indicate that sugar metabolism and accumulation in apple fruit is developmentally regulated. This represents a comprehensive analysis of the genes involved in sugar metabolism and accumulation in apple, which will serve as a platform for further studies on the functions of these genes and subsequent manipulation of sugar metabolism and fruit quality traits related to carbohydrates. © 2012 Li et al.

Wang W.,Northwest University, China | Zhao Y.,Xiamen University
Physical Chemistry Chemical Physics | Year: 2011

Thermal rate constants and kinetic isotope effects for the title reaction are calculated by using the quantum instanton approximation within the full dimensional Cartesian coordinates. The obtained results are in good agreement with experimental measurements at high temperatures. The detailed investigation reveals that the anharmonicity of the hindered internal rotation motion does not influence the rate too much compared to its harmonic oscillator approximation. However, the motion of the nonreactive methyl group in C2H 6 significantly enhances the rates compared to its rigid case, which makes conventional reduced-dimensionality calculations a challenge. In addition, the temperature dependence of kinetic isotope effects is also revealed. © the Owner Societies 2011.

Hui J.,Tsinghua University | Hui J.,Northwest University, China | Zhang X.,Tsinghua University | Zhang Z.,Tsinghua University | And 4 more authors.
Nanoscale | Year: 2012

Water-dispersible hydrophilic fluoridated HAp:Ln3+ (Ln = Eu or Tb) nanoparticles were prepared via hydrophobic/hydrophilic transformation with surfactants (Pluronic F127). The HAp:Ln3+ (Ln = Eu or Tb) nanoparticles with unique luminescent properties and excellent biocompatibility are promising for cell imaging applications. © 2012 The Royal Society of Chemistry.

Pan S.,Northwest University, China | Zhang Y.,Northwest University, China | Li X.,Queensland University of Technology
Knowledge and Information Systems | Year: 2012

Most of studies on streaming data classification are based on the assumption that data can be fully labeled. However, in real-life applications, it is impractical and time-consuming to manually label the entire stream for training. It is very common that only a small part of positive data and a large amount of unlabeled data are available in data stream environments. In this case, applying the traditional streaming algorithms with straightforward adaptation to positive unlabeled stream may not work well or lead to poor performance. In this paper, we propose a Dynamic Classifier Ensemble method for Positive and Unlabeled text stream (DCEPU) classification scenarios. We address the problem of classifying positive and unlabeled text stream with various concept drift by constructing an appropriate validation set and designing a novel dynamic weighting scheme in the classification phase. Experimental results on benchmark dataset RCV1-v2 demonstrate that the proposed method DCEPU outperforms the existing LELC (Li et al. 2009b), DVS (with necessary adaption) (Tsymbal et al. in Inf Fusion 9(1):56-68, 2008), and Stacking style ensemble-based algorithm (Zhang et al. 2008b). © 2011 Springer-Verlag London Limited.

Kang J.,Northwest University, China | Zhang Z.,Northwest University, China | Wang J.J.,Louisiana State University
Bioresource Technology | Year: 2011

Influence of humic substances (HS) on bioavailability of Cu and Zn was characterized during 120. days co-composting of sewage sludge and maize straw. At the initial stage of composting, Cu and Zn in sewage sludge were released as organic matter was degraded, and water soluble Cu and Zn increased markedly. Water soluble Cu and FA content decreased after 21. days whereas water soluble Zn increased during the whole process. Both HA-Cu and HA-Zn were significantly and positively correlated with HA and H/F, respectively. At the end of composting, the distribution coefficients of HA-Cu and HA-Zn reached 27.50% and 3.33% respectively with HA-Cu/HA-Zn ratio increased from 1.29 to 2.73. The results suggest that Cu combined with HA more strongly than Zn, and composting treatment could decrease bioavailability of Cu markedly. © 2011 Elsevier Ltd.

Wang W.,Northwest University, China | Zhao Y.,Xiamen University
Journal of Chemical Physics | Year: 2012

Thermal rate constants for the title reaction are calculated by using the quantum instanton approximation within the full dimensional Cartesian coordinates. The results reveal that the quantum effect is remarkable for the reaction at both low and high temperatures, and the obtained rates are in good agreement with experimental measurements at high temperatures. Compared to the harmonic approximation, the torsional anharmonic effect of the internal rotation has a little influence on the rates at low temperatures, however, it enhances the rate by about 20% at 1000 K. In addition, the free energy barriers for the isotopic reactions and the temperature dependence of kinetic isotope effects are also investigated. Generally speaking, for the title reaction, the replacement of OH with OD will reduce the free energy barrier, while substituting D for H (connected to C) will increase the free energy barrier. © 2012 American Institute of Physics.

Liu Q.,Academy of Agricultural science | Liu Q.,Academy of Military Medical science | Li M.-W.,Academy of Agricultural science | Li M.-W.,Guangdong Ocean University | And 3 more authors.
The Lancet Infectious Diseases | Year: 2015

Human sparganosis is a food borne zoonosis caused by the plerocercoid larvae (spargana) of various diphyllobothroid tapeworms of the genus Spirometra. Human infections are acquired by ingesting the raw or undercooked meat of snakes or frogs, drinking untreated water, or using raw flesh in traditional poultices. More than 1600 cases of sparganosis have been documented worldwide, mostly in east and southeast Asia. Sporadic cases have been reported in South America, Europe, and Africa, and several cases have been described in travellers returning from endemic regions. Epidemiological data suggest that the increased effect of sparganosis on human health is because of greater consumption of raw meat of freshwater frogs and snakes. This Review provides information about the Spirometra parasites and their lifecycles, summarises clinical features, diagnosis, and treatment of human sparganosis, and describes geographical distribution and infection characteristics of Spirometra parasites in host animals. © 2015 Elsevier Ltd.

Chen Y.-X.,Hefei University of Technology | Zheng Y.-F.,Hefei University of Technology | Chen R.-X.,Hefei University of Technology | Zhang S.-B.,Hefei University of Technology | And 3 more authors.
Geochimica et Cosmochimica Acta | Year: 2011

A combined in situ SIMS and LA-(MC)-ICPMS study of U-Pb ages, trace elements, O and Lu-Hf isotopes was conducted for zircon from eclogite-facies metamorphic rocks in the Sulu orogen. The two microbeam techniques sampled various depths of zircon domains, revealing different element and isotope relationships between residual magmatic cores and new metamorphic rims and thus the geochemical architecture of metamorphic zircons which otherwise cannot be recognized by the single microbeam technique. This enables discrimination of metamorphic growth from different subtypes of metamorphic recrystallization. Magmatic cores with U-Pb ages of 769±9Ma have positive δ18O values of 0.1-10.1‰, high Th/U and 176Lu/177Hf ratios, high REE contents, and steep MREE-HREE patterns with negative Eu anomalies. They are interpreted as crystallizing from positive δ18O magmas during protolith emplacement. In contrast, newly grown domains have concordant U-Pb ages of 204±4 to 252±7Ma and show negative δ18O values of -10.0‰ to -2.2‰, low Th/U and 176Lu/177Hf ratios, low REE contents, and flat HREE patterns with weak to no Eu anomalies. They are interpreted as growing from negative δ18O fluids that were produced by metamorphic dehydration of high-T glacial-hydrothermally altered rocks during continental subduction-zone metamorphism. Differences in δ18O between different domains within single grains vary from 0.8‰ to 12.5‰, suggesting different degrees of O isotope exchange between the positive δ18O magmatic core and the negative δ18O metamorphic fluid during the metamorphism. The magmatic zircons underwent three subtypes of metamorphic recrystallization, depending on their accessibility to negative δ18O fluids. The zircons recrystallized in solid-state maintained positive δ18O values, and REE and Lu-Hf isotopes of protolith zircon, but their U-Pb ages are lowered. The zircons recrystallized through dissolution exhibit negative δ18O values similar to the metamorphic growths, almost completely reset U-Pb ages, and partially reset REE systems. The zircons recrystallized through replacement show variably negative δ18O values, and partially reset REE, and U-Pb and Lu-Hf isotopic systems. Therefore, this study places robust constraints on the origin of metamorphic zircons in eclogite-facies rocks and provides a methodological framework for linking the different types of metamorphic zircons to petrological processes during continental collision. © 2011 Elsevier Ltd.

Zhang H.-F.,China University of Geosciences | Zhang H.-F.,Northwest University, China | Zhai M.-G.,CAS Institute of Geology and Geophysics | Santosh M.,Kochi University | And 2 more authors.
Gondwana Research | Year: 2011

Neoarchean potassic meta-granites occurring in the Huai'an Complex within the north central part of the North China Craton (NCC) comprise leucocratic syenogranites, biotite monzogranites, and garnet-bearing syenogranites. High-pressure garnet-granulites occur as lenses, sheets or dismembered dikes with the granitoids. Here we present SHRIMP zircon U-Pb data from the leucocratic syenogranites which show an age of 2493±6Ma (MSWD=1), and LA-ICP-MS U-Pb data from the biotite-monzogranites and garnet-syenogranites, revealing their formation ages of 2437±10Ma (MSWD=2.0) and 1977-2003Ma, respectively. We also report metamorphic ages of ca. 1800Ma from zircons in the garnet-syenogranites. Geochemical studies show low MgO (0.5-0.06wt.%), Cr (6.19-0.53ppm) and Ni (27.66-2.01ppm) with varying SiO2 (62.3 to 76.8wt.%) contents, indicating their derivation from a crustal source. The leucosyenogranites exhibit elevated positive Eu anomalies with decreasing Sr, Th, U, and bulk REE concentrations, and Th/U ratio, whereas Rb and Ba values increase with decreasing Th/U ratio, indicating fluid-melt interaction. The leucosyenogranites have high Sr and Ba contents and Sr/Y and (La/Yb)N ratios and low Y and HREEs, with zircon εHf(t) values ranging from +1.7 to +5.8 and Hf model ages of 2.60-2.73Ga, reflecting their derivation by partial melting of overthickened juvenile lower crust of eclogitic composition, or an eclogitic mineral assemblage in the residue.Geochemical compositions of the biotite-monzogranites, with positive εNd(t) values (+2.3 to +2.5) and model ages <2.60Ga, indicate that they are evolved partial melts from a thickened juvenile crust of garnet amphibolite composition, or with garnet and amphiboles in the residue, followed by fractionation dominated by plagioclase precipitation. The garnet-syenogranites display variable contents of SiO2 (62.3-72.3wt.%), and relatively high Zr (491-1096ppm), Ga (23.5-31.2ppm), Zn (38-124ppm), Y (34.1-85.6ppm) and Nb (9.4-90.0ppm) abundances with 104×Ga/Al ratios of 3.1-4.2. They also possess low Sr (50-161ppm) concentrations and strong negative Eu anomalies. These features, integrated with Nd model ages of 2.46-2.50Ga and relatively constant negative εNd(t) values (-2.5 to -2.9) with increasing SiO2 contents, suggest A-type granitic affinities of intraplate extensional or rift setting with evolution of the magma from partial melts derived from Neoarchean tonalitic rocks. The distinct geochemical features and zircon saturation temperatures of the granitoids are indicative of high melting temperatures (900-1000°C) at relatively low pressures (6-10kbar). Based on previous works and our new data, we link the ca. 2500-2450Ma and 2000Ma magmatic events to a Neoarchean amalgamation of microblocks and Paleoproterozoic mobile belts. The metamorphic ages of 1800-1820Ma might reflect an amphibolite facies retrograde event. © 2011.

Dai L.-Q.,Hefei University of Technology | Zhao Z.-F.,Hefei University of Technology | Zheng Y.-F.,Hefei University of Technology | Li Q.,CAS Institute of Geology and Geophysics | And 2 more authors.
Earth and Planetary Science Letters | Year: 2011

In-situ SIMS zircon U-Pb dating and O isotope analysis as well as LA-(MC)-ICPMS zircon U-Pb dating and Lu-Hf isotope analysis were carried out for postcollisional mafic-ultramafic rocks in the Dabie orogen, China. The zircon U-Pb dating gave consistent ages of 126±1 to 131±1Ma for magma crystallization. Survival of residual zircon cores is identified by CL imaging and U-Pb dating, yielding ages of 697±10 and 770±11Ma that agree with protolith U-Pb ages of UHP metaigneous rocks in the Dabie orogen. The zircon Hf-O isotope compositions show systematic variations that can be categorized into three groups. Group I has the lowest δ18O values of 2.0 to 2.9‰ but the highest εHf(t) values of -3.5 to -1.0 with the youngest Hf model ages of 1.2 to 1.4Ga. Group II displays intermediate δ18O values of 4.0 to 5.1‰ and εHf(t) values of -22.5 to -13.2 with Hf model ages of 2.0 to 2.6Ga. Group III exhibits the highest δ18O values of 5.2 to 7.3‰ but the lowest εHf(t) values of -29.1 to -18.6 with the oldest Hf model ages of 2.4 to 3.0Ga. The three groups of Hf-O isotope compositions correspond to a three-layer Hf-O isotope structure in the subducted continental crust, suggesting their involvement in the mantle source. Along with existing data for whole-rock Sr-Nd isotopes and trace elements, it appears that the mantle source for the postcollisional mafic-ultramafic rocks is characterized by fertile lithochemistry, the arc-like signature of trace elements, the heterogeneous enrichment of radiogenic isotopes, the differential incorporation of supracrustal materials, and the variable concentrations of water. Clearly, such a source is neither the asthenospheric mantle nor the refractory subcontinental lithospheric mantle (SCLM). It is a kind of the orogenic SCLM that would be generated by reaction of the overlying SCLM-wedge peridotite with hydrous silicate melts derived from different layers of the subducted continental crust. Therefore, the postcollisional mafic-ultramafic rocks provide a petrological record of crust-mantle interaction during the continental deep subduction. © 2011 Elsevier B.V.

Zhai M.-G.,Northwest University, China | Zhai M.-G.,CAS Institute of Geology and Geophysics | Santosh M.,Kochi University
Gondwana Research | Year: 2011

The crustal growth and stabilization of the North China Craton (NCC) relate to three major geological events in the Precambrian: (1) a major phase of continental growth at ca. 2.7. Ga; (2) the amalgamation of micro-blocks and cratonization at ca. 2.5. Ga; and (3) Paleoproterozoic rifting-subduction-accretion-collision tectonics and subsequent high-grade granulite facies metamorphism-granitoid magmatism during ca. 2.0-1.82. The major period of continental growth during 2.9-2.7. Ga in the NCC correlates with the global growth of Earth's crust recognized from other regions. The enormous volume of tonalite-trondhjemite-granodiorite (TTG) rocks and associated komatiite-bearing magmatic suites developed during this period possibly suggest the manifestation of plume tectonics. The cratonization of the NCC at the end of Neoarchean at ca. 2.5. Ga (Archean-Proterozoic boundary) through the amalgamation of micro-blocks was accompanied by granulite facies metamorphism and voluminous intrusion of crustally-derived granitic melts leading to the construction of the basic tectonic framework of the NCC. Several Neoarchean greenstone belts surround the micro-blocks and represent the vestiges of older arc-continent collision. The next major imprint in the NCC is the Paleoproterozoic orogenic events during 2.35 -1.82 Ga which involved rifting followed by subduction -accretion -collision processes, followed by plume-triggered extension and rifting, offering important insights into modern-style plate tectonics operating in the Paleoproterozoic. Extreme crustal metamorphism and formation of high pressure (HP) and ultra-high temperature (UHT) orogens during 1950-1820. Ma accompanied the subduction-collision process and the suturing of continental blocks within the Paleoproterozoic supercontinent Columbia. Multiple subduction zones with opposing subduction polarity promoted the rapid assembly of crustal fragments of the NCC and their incorporation into the Columbia supercontinent. The HP and HT-UHT granulites demonstrate two main stages of metamorphism at ca. 1.95-1.89. Ga and at ca. 1.85-1.82. Ga, exhuming the basement rocks from lowermost crust level to the lower-middle crust level. With the emplacement of extensive mafic dyke swarms associated with continental rifting, and the intrusion of anorogenic magmatic suites, the evolution of the NCC into a stable continental platform was finally accomplished. © 2011 International Association for Gondwana Research.

Duan L.,Northwest University, China | Meng Q.-R.,CAS Institute of Geology and Geophysics | Zhang C.-L.,Northwest University, China | Liu X.-M.,Northwest University, China
Gondwana Research | Year: 2011

U-Pb detrital zircon geochronology from Lower Devonian quartz arenites of the northwestern margin of the Yangtze block yields dominant early Neoproterozoic (0.85-1.0Ga), Pan-African (0.5-0.65Ga) and middle Neoproterozoic (0.68-0.8Ga) age populations and minor Mesoproterozoic to middle Mesoarchean (1.0-3.0Ga) ages. Middle Mesoarchean to Mesoproterozoic rocks, however, are widespread in the South China block. Although Hf isotopic compositions show both juvenile crustal growth and crustal reworking for all the age groupings, the crust growth, essentially mantle-derived, occurred mainly around 3.1Ga, 1.9Ga and 1.0Ga, respectively. Zircon typology and youngest grain ages indicate that this suite of quartz arenites was the product of multiphase reworking. Abundant magmatic zircon detritus with concordant U-Pb Grenvillian and Pan-African ages, together with accompanying various εHf(t) values, indicate an exotic provenance for the quartz arenite external to the South China block. Qualitative comparisons of age spectra for the late Neoproterozoic sediments of the Cathaysian Block, early Paleozoic sediments of pre-rift Tethyan Himalaya sequence in North India and lower Paleozoic sandstone from the Perth Basin in West Australia, show that they all have two the largest age clusters representing Grenvillian and Pan-African orogenic episodes. The resemblance of these age spectra and zircon typology suggests that the most likely source for the Lower Devonian quartz arenites of the South China block was the East African Orogen and Kuunga Orogen for their early Grenvillian and Pan-African populations, whereas the Hannan-Panxi arc, Jiangnan orogen, and the Yangtze block basements might have contributed to the detrital zircon grains of the Neoproterozoic and Pre-Grenvillian ages. Hf isotopic data indicate that the crustal evolution of the drainage area matches well with the episodic crust generation of Gondwana. These results imply that the previously suggested position of the SCB in Gondwana should be re-evaluated, and the South China block should be linked with North India and West Australia as a part of East Gondwana during the assembly of Gondwana, rather than a discrete continent block in the paleo-Pacific. © 2010 International Association for Gondwana Research.

Chen L.,CAS Nanjing Institute of Geology and Palaeontology | Chen L.,University of Chinese Academy of Sciences | Xiao S.,Virginia Polytechnic Institute and State University | Pang K.,CAS Nanjing Institute of Geology and Palaeontology | And 4 more authors.
Nature | Year: 2015

Phosphorites of the EdiacaranDoushantuo Formation (600 million yearsold) yield spheroidalmicrofossilswith a palintomic cell cleavage pattern1,2. These fossils have been variously interpreted as sulphuroxidizing bacteria3, unicellular protists4, mesomycetozoean-like holozoans5, green algae akin to Volvox6,7, and blastula embryos of early metazoans1,2,8-10 or bilaterian animals11,12. However, their complete life cycle is unknownand it is uncertain whether they had a cellularly differentiated ontogenetic stage, making it difficult to test their various phylogenetic interpretations. Here we describe new spheroidal fossils from black phosphorites of the Doushantuo Formation that have been overlooked in previous studies.These fossils represent later developmental stages of previouslypublishedblastula-like fossils, and they show evidence for cell differentiation, germ-soma separation, and programmed cell death. Their complexmulticellularity is inconsistent with a phylogenetic affinity with bacteria,unicellular protists, or mesomycetozoean-like holozoans. Available evidence also indicates that the Doushantuo fossils are unlikely crown-group animals or volvocine green algae.Weconclude that an affinity with cellularly differentiated multicellular eukaryotes, including stem-group animals or algae, is likely butmore data are needed to constrain further the exact phylogenetic affinity of the Doushantuo fossils. © 2014 Macmillan Publishers Limited. All rights reserved.

Tam P.Y.,University of Hong Kong | Zhao G.,University of Hong Kong | Zhou X.,Chinese Academy of Geological Sciences | Sun M.,University of Hong Kong | And 5 more authors.
Gondwana Research | Year: 2012

High-pressure pelitic granulites have recently been found from the Jiaobei massif in the southern segment of the Jiao-Liao-Ji Belt (JLJB), which separates the Eastern Block of the North China Craton into the Longgang and Langrim Blocks. Petrological evidence from these high-pressure pelitic granulites indicates three distinct metamorphic stages (M1-M3). The pre-peak (M1) stage is represented by a mineral assemblage of garnet (core). +. inclusion-type minerals within the garnet (biotite. +. kyanite. +. muscovite. +. plagioclase. +. quartz. +. ilmenite). The peak (M2) stage is marked by a mineral assemblage of garnet (mantle). +. K-feldspar. +. kyanite. +. plagioclase. +. biotite. +. rutile. +. ilmenite. +. quartz. The post-peak (M3) stage is featured by a mineral assemblage of garnet (rim). +. sillimanite. +. plagioclase. +. biotite. +. ilmenite. +. quartz. Using the THERMOCALAC technique, the NCKFMASHTO system has been applied to construct pseudosections for a representative high-pressure pelitic granulite sample. P-T conditions for the M1, M2 and M3 stages are constrained at 9.3-10.7. kbar/645-670. °C, 14.8-16.2. kbar/860-890. °C, and 6.3-8.5. kbar/710-740. °C, respectively. The mineral assemblages and P-T conditions of the high-pressure pelitic granulites define a clockwise P-T path involving decompression and cooling following the peak high-pressure granulite facies metamorphism. This suggests that the high-pressure pelitic granulites experienced the initial crustal thickening (M1 and M2), followed by exhumation and cooling (M3), which implies that the southern segment of the JLJB must have been involved in subduction- or collision-related tectonic processes. Therefore, the JLJB may represent another Paleoproterozoic collisional belt along which the Longgang and Langrim Blocks amalgamated to form the Eastern Block. © 2011 International Association for Gondwana Research.

Qiang H.,Northwest University, China | Qiang H.,Tohoku University | Lang D.-L.,Northwest University, China | Li Y.-Y.,Tohoku University | Li Y.-Y.,Xi'an University of Architecture and Technology
Bioresource Technology | Year: 2012

The effect of trace metals on the mesophilic methane fermentation of high-solid food waste was investigated using both batch and continuous experiments. The continuous experiment was conducted by using a CSTR-type reactor with three run. During the first run, the HRT of the reactor was stepwise decreased from 100. days to 30. days. From operation day 50, the reactor efficiency deteriorated due to the lack of trace metals. The batch experiment showed that iron, cobalt, and nickel combinations had a significant effect on food waste. According to the results of the batch experiment, a combination of iron, cobalt, and nickel was added into the CSTR reactor by two different methods at run II, and III. Based on experimental results and theoretical calculations, the most suitable values of Fe/COD, Co/COD, and Ni/COD in the substrate were identified as 200, 6.0, and 5.7. mg/kg COD, respectively. © 2011 Elsevier Ltd.

Gao J.-M.,Northwest University, China | Yang S.-X.,Zhejiang Agriculture And forestry University | Qin J.-C.,Jilin University
Chemical Reviews | Year: 2013

Researchers survey the chemical and biological literature regarding the isolation, structure elucidation, biological activities, biosynthesis, and chemical synthesis of azaphilone derivatives from nature. The general methods for the synthesis of some natural azaphilone-like scaffolds are also discussed. Citrinin produced by several fungal species of genera Penicillium, Monascus, and Aspergillus, is widely considered as a hazardous contaminant of foods and feeds. A number of various derivatives of the citrinin family have been isolated from different P. citrinum strains and two Aspergillus species. The derivatives can be classified into four different categories on the basis of the degree of polymerization of the citrinin core, including monomeric citrinin congeners 2-6 and decarboxydihydrocitrinin.

Tang Y.-J.,CAS Institute of Geology and Geophysics | Zhang H.-F.,CAS Institute of Geology and Geophysics | Zhang H.-F.,Northwest University, China | Ying J.-F.,CAS Institute of Geology and Geophysics | Su B.-X.,CAS Institute of Geology and Geophysics
Earth-Science Reviews | Year: 2013

Studies of mantle xenoliths have confirmed that Archean subcontinental lithospheric mantle (SCLM) is highly depleted in basaltic components (such as Al, Ca and Na) due to high-degree extraction of mafic and ultramafic melts and thus is refractory and buoyant, which made it chronically stable as tectonically independent units. However, increasing studies show that ancient SCLM can be refertilized by episodic rejuvenation events like infiltration of upwelling fertile material. The North China Craton is one of the most typical cases for relatively complete destruction of its Archean keel since the eruption of Paleozoic kimberlites, as is evidenced by a dramatic change in the compositions of mantle xenoliths sampled by Paleozoic to Cenozoic magmas, reflecting significant lithospheric thinning and the change in the character of the SCLM. The compositional change has been interpreted as the result of refertilization of Archean SCLM via multiple-stage peridotite-melt reactions, suggested by linear correlations between MgO and indices of fertility, covariations of Al2O3 with CaO, La/Yb, 87Sr/86Sr, 143Nd/144Nd, 187Os/188Os and Re-depletion ages (TRD), high Re abundances, scatter in Re-Os isotopic plot, variable in situ TRD ages of sulfides, and correlation between TRD ages and olivine Fo of peridotite xenoliths in Paleozoic kimberlites and Cenozoic basalts on the craton.By integrating major and trace element, Sr, Nd and Os isotopic compositions of peridotite xenoliths and orogenic massif peridotites from the continents of Europe, Asia, America, Africa and Australia, together with previous studies of petrology and geochemistry of global peridotites, we suggest that (1) refertilization of cratonic and circum-cratonic lithospheric mantle is widespread; (2) Archean SCLM worldwide has experienced a multi-stage history of melt depletion and refertilization since segregation from the convecting mantle; (3) cratonic SCLM may be more susceptible to compositional change caused by refertilization than is generally assumed; (4) the original character of much Archean cratonic mantle has been partly overprinted, or even erased by varying degrees of refertilization, which may play a key role in the rejuvenation and erosion of the SCLM beneath the Archean cratons.Due to the refertilization of ancient SCLM, (1) many published whole-rock Re-depletion ages cannot represent the formation ages of peridotites, but the mixtures of different generations of sulfides. Thus, the chronological significance of the Re-Os isotopic composition in individual peridotite should be cautiously interpreted; (2) many kimberlite- and intraplate basalt-borne lherzolite xenoliths, with major element compositions close to primitive mantle, may be the fragments of the ancient SCLM, strongly refertilized by infiltration of asthenosphere-derived melts, rather than newly-accreted SCLM. Consequently, new accretion of SCLM beneath ancient cratons such as the North China Craton may be less than was previously assumed. © 2013 Elsevier B.V.

Luo Y.,Northwest University, China | Zhang T.,Northwest University, China | Wu H.,Rice University
Biotechnology Advances | Year: 2014

Escherichia coli can uptake and utilize many common natural sugars to form biomass or valuable target bio-products. Carbon catabolite repression (CCR) will occur and hamper the efficient production of bio-products if E. coli strains are cultivated in a mixture of sugars containing some preferred sugar, such as glucose. Understanding the transport and metabolism mechanisms of the common and inexpensive sugars in E. coli is important for further improving the efficiency of sugar bioconversion and for reducing industrial fermentation costs using the methods of metabolic engineering, synthetic biology and systems biology. In this review, the transport and mediation mechanisms of glucose, fructose, sucrose, xylose and arabinose are discussed and summarized, and the hierarchical utilization principles of these sugars are elucidated. © 2014 Elsevier Inc.

Jing H.,Northwest University, China | Guo C.,Northwest University, China | Zhang G.,Sun Yat Sen University | Su X.,Northwest University, China | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Ce 3+-doped Ba 2Ln(BO 3) 2Cl (Ln = Gd, Y) phosphors were synthesized through a conventional high-temperature solid state method in CO atmosphere. Structural and spectroscopic characterizations of the samples have been performed by X-ray diffraction and photoluminescence spectra measurements. The phosphors can be efficiently excited by near ultraviolet (n-UV) light resulting in blue emission. The optimal Ce 3+ dopant concentrations in both compounds were determined, and the concentration quenching mechanisms were also discussed. The photoluminescence excitation (PLE) and emission (PL) spectra, and decay curves at liquid helium temperature were measured to analyze the crystallographic occupancy sites of Ce 3+ in the Ba 2Ln(BO 3) 2Cl (Ln = Gd, Y) hosts. The thermal stabilities of the phosphors Ba 2Ln(BO 3) 2Cl:Ce 3+ (Ln = Gd, Y) were studied using the dependence of the luminescence intensities on temperature (300-500 K), and their luminescence quenching temperatures and thermal activation energies were also determined. The results indicate that the phosphor Ba 2Gd(BO 3) 2Cl:Ce 3+ offers excellent optical properties as a potential blue-emitting phosphor candidate for n-UV LEDs, such as a higher thermal stability and a stronger luminescence intensity, than those of the phosphor Ba 2Y(BO 3) 2Cl:Ce 3+. © 2012 The Royal Society of Chemistry.

Zhang Y.,Northwest University, China | Zhang Y.,Cornell University | Li P.,Cornell University | Cheng L.,Cornell University
Food Chemistry | Year: 2010

The developmental changes of carbohydrates, organic acids, amino acids and phenolic compounds in 'Honeycrisp' apple flesh were investigated using GC-MS and HPLC. A total of 12 carbohydrates, 8 organic acids, 20 amino acids, and 18 phenolic compounds were identified and quantified. Each metabolite showed characteristic changes during fruit development, but in general, concentrations of most sugars and sugar alcohols either increased or remained unchanged whereas concentrations of most organic acids, amino acids and phenolic compounds decreased with fruit development, indicating that most sugars and sugar alcohols are synthesised and/or accumulate at a faster or similar rate relative to fruit growth whereas organic acids, amino acids and phenolics are synthesised and/or accumulate at a slower rate relative to fruit growth. On a whole fruit basis, the content of most metabolites increased with fruit development. In the flesh of mature 'Honeycrisp' apple, fructose and sucrose and sorbitol are the major sugars and sugar alcohol; malic acid is the major organic acid; aspartic acid, asparagine, glutamic acid, proline, threonine and γ-aminobutyric acid are the major amino acids; and procyanidin B1, procyanidin B2, chlorogenic acid, catechin and epicatechin are the major phenolic compounds, respectively. © 2010 Elsevier Ltd.

Jiao L.,Xi'an Shiyou University | Li H.,Northwest University, China
Chemometrics and Intelligent Laboratory Systems | Year: 2010

A practicable quantitative structure property relationship (QSPR) model for predicting aqueous solubility, Sw, of 23 polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was developed. Linear artificial neural network (L-ANN) was used to develop the calibration model of Sw. The input variables of L-ANN were selected from 11 structural descriptors of the investigated PCDD/Fs by using stepwise regression. Leave one out cross validation and split-sample validation were carried out to assess the predictive performance of the developed model. The results of leave one out cross validation and split-sample validation are both satisfactory, which verify the reliability and practicability of the developed model. It is demonstrated that L-ANN combined with stepwise regression is a practicable method for developing QSPR model for Sw of PCDD/Fs. Additionally, stepwise regression is shown to be a practicable approach for the selection of input variables when developing a QSPR model with L-ANN. © 2010 Elsevier B.V.

Wang P.,Northwest University, China | Sun X.,Northwest University, China | Chang C.,Northwest University, China | Feng F.,Northwest University, China | And 3 more authors.
Journal of Pineal Research | Year: 2013

Melatonin has an important anti-aging role in plant physiology. We tested the effects of long-term melatonin exposure on metabolic status and protein degradation during natural leaf senescence in trees of Malus hupehensis Rehd. The 2-month regular supplement of 100 μm melatonin to the soil once every 6 days altered the metabolic status and delayed protein degradation. For example, leaves from treated plants had significantly higher photosynthetic activity, chlorophyll concentrations, and levels of three photosynthetic end products (sorbitol, sucrose, and starch) when compared with the control. The significant inhibition of hexose (fructose and glucose) accumulation possibly regulated the signaling of MdHXK1, a gene for which expression was also repressed by melatonin during senescence. The plants also exhibited better preservation of their nitrogen, total soluble protein, and Rubisco protein concentrations than the control. The slower process of protein degradation might be a result of melatonin-linked inhibition on the expression of apple autophagy-related genes (ATGs). Our results are the first to provide evidence for this delay in senescence based on the metabolic alteration and protein degradation. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Niu Q.,Tohoku University | Qiao W.,Tohoku University | Qiao W.,China University of Petroleum - Beijing | Qiang H.,Northwest University, China | And 2 more authors.
Bioresource Technology | Year: 2013

The thermophilic methane fermentation of chicken manure (10% TS) was investigated within a wide range of ammonia. Microbiological analysis showed significant shifts in Archaeal and Bacterial proportions with VFA accmulation and CH4 formation before and after inhibition. VFA accumulated sharply with lower methane production, 0.29 L/g VS, than during the steady stage, 0.32L/g VS. Biogas production almost ceased with the synergy inhibition of TAN (8000mg/L) and VFA (25,000mg/L). Hydrogenotrophic Methanothermobacter thermautotrophicus str. was the dominate archaea with 95% in the inhibition stage and 100% after 40days recovery compared to 9.3% in the steady stage. Aceticlastic Methanosarcina was not encountered with coincided phenomenal of high VFA in the inhibition stage as well as recovery stage. Evaluation of the microbial diversity and functional bacteria indicated the dominate phylum of Firmicutes were 94.74% and 84.4% with and without inhibition. The microbial community shifted significantly with elevated ammonia concentration affecting the performance. © 2013 .

Liu Q.,Hunan Normal University | Zhao J.,Northwest University, China
Nonlinear Analysis: Real World Applications | Year: 2014

We investigate blow-up criteria for the local in time classical solution of the nematic liquid crystal flows in dimensions two and three. More precisely, we prove that 0

Niu Q.,Tohoku University | Qiao W.,Tohoku University | Qiao W.,China University of Petroleum - Beijing | Qiang H.,Northwest University, China | And 3 more authors.
Bioresource Technology | Year: 2013

A 12L mesophilic CSTR of chicken manure fermentation was operated for 400days to evaluate process stability, inhibition occurrence and the recovery behavior suffering TAN concentrations from 2000mg/L to 16,000mg/L. A biogas production of 0.35-0.4L/gVSin and a COD conversion of 68% were achieved when TAN concentration was lower than 5000mg/L. Ammonia inhibition occurred due to the addition of NH4HCO3 to the substrate. The biogas and COD conversion decreased to 0.3L/gVSin and 20% at TAN 10,000mg/L and was totally suppressed at TAN 16,000mg/L. Carbohydrate and protein conversion decreased by 33% and 77% after inhibition. After extreme inhibition, the reactor was diluted and washed, reducing TAN and FA to 4000mg/L and 300mg/L respectively, and the recovered biogas production was 0.5L/gVSin. The extended Monod model manifested the different sensitivities of hydrolysis, acidogenesis and methanogenesis to inhibition. VFA accumulation accompanied an increase in ammonia and exerted a toxic on microorganism. © 2013 Elsevier Ltd.

Gao H.,Xi'an Shiyou University | Sun W.,Northwest University, China
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2010

Diagenesis and favorable diagenetic facies of Chang 8 reservoir in Heshui area, Ordos basin are researched using physical property analysis, mercury penetration, cast section and SEM technique. The results show that physical property is poor, pore throat is minute, fine-mesograin feldspathic litharenite dominated, clastic constituents arecomplicate,compositional maturity is low and texture maturity is low to middle. Original pore spaces are decreased because ofcompaction, cementation damage not only partial primary pore but also secondary dissolved pore, dissolution improves the physical property. Five kinds of diagenetic facies are classified on the base of the influence of diagenesis on physical property. There is an intimate relationship between qualifying reservoir and diagenetic facies, physical property and oil bearing of chlorite cementation-feldspar corrosion facies are the best, chlorite cementation facies follows, which construct the favorable diagenetic facies of reservoir develop.

Zhang H.-F.,Northwest University, China | Zhang H.-F.,CAS Institute of Geology and Geophysics | Ying J.-F.,CAS Institute of Geology and Geophysics | Santosh M.,Kochi University | Zhao G.-C.,University of Hong Kong
Precambrian Research | Year: 2012

A comprehensive review of U-Pb geochronology and Hf isotopes of zircons separated from granulite xenoliths entrained in Phanerozoic magmatic rocks and inherited xenocrysts from the associated lower crust rocks from various domains of the North China Craton (NCC) provides new insights into understanding the evolution of the lower crust in this part of the Precambrian nucleus of Asia. The oldest zircons recorded in granulite xenoliths show ages up to 3.6Ga, slightly younger than the oldest zircons (3.8Ga) from samples of the exposed Archean upper crust. However, the Hf isotope features indicate that the oldest lower crust might have been derived from a 4.0 to 4.1Ga primordial crust as indicated by the data from an inherited zircon in the North Qinling Orogenic Belt at the southern part of the NCC. Our synthesis also suggests that ca. 2.5Ga mark an important period for the evolution of the lower crust of the NCC and the cratonization of the Archean blocks in the NCC, at least for the Eastern Block, with a possible link to mantle plume activity. The occasional presence of zircons with 2.6-3.1Ga ages in the lower crustal granulite xenoliths suggests a continuous reworking of the Paleoarchean lower crust during the Archean. The comprehensive data also show that 1.8-2.0Ga period was the first significant event for the evolution of the lower crust after the cratonization of the Archean blocks of the NCC, which affected the whole lower crust of the Eastern NCC. Episodic growth or rejuvenation of the Precambrian lower crust beneath the NCC is also revealed by U-Pb and Hf isotope data, resulting from the corresponding addition of juvenile materials from mantle to lower crust, with a mixing of the old crust with juvenile magma. This compositional modification of the lower crust resembles the compositional transformation from the refractory lithospheric mantle to a fertile one through the refractory peridotite - infiltrated melt reaction as revealed in the lithospheric mantle beneath the NCC. © 2011 Elsevier B.V.

Zhao Z.-F.,Hefei University of Technology | Zheng Y.-F.,Hefei University of Technology | Zhang J.,Hefei University of Technology | Zhang J.,Northwest University, China | And 3 more authors.
Chemical Geology | Year: 2012

A combined study of zircon U-Pb ages, Lu-Hf isotopes, mineral O isotopes, whole-rock elements and Sr-Nd isotopes was carried out for alkaline intrusive rocks (including gabbro, syenite and granite) in the Sulu orogen. The results provide insights into crust-mantle interaction in the continental subduction zone. SIMS and LA-ICPMS zircon U-Pb dating yield Late Triassic ages of 201±2 to 212±1Ma for their crystallization. These ages are younger than Middle Triassic ages for ultrahigh-pressure (UHP) metamorphism of country rocks, corresponding to syn-exhumation magmatism during continental collision. The alkaline rocks are characterized by the arc-like patterns of trace element distribution, with relative enrichment of LILE and LREE but relative depletion of HFSE. They have high initial 87Sr/ 86Sr ratios of 0.7064 to 0.7114 and highly negative ε Nd(t) values of -16.4 to -13.8 with two-stage Nd model ages of 2.11 to 2.33Ga for whole-rock. Zircon Lu-Hf isotope analyses also show highly negative ε Hf(t) values of -20.9±0.5 to -14.1±0.9, with two-stage Hf model ages of 2.10±0.06 to 2.56±0.03Ga. The zircon exhibits relatively consistent δ 18O values of 5.6 to 6.2‰, slightly higher than normal mantle values. The enrichment of radiogenic Sr-Nd-Hf isotopes in the gabbro indicates its origination from an isotopically enriched mantle source, whereas the arc-like pattern of trace element distribution for it suggests a fertile mantle source with enrichment of LILE and LREE. Thus, it is part of the orogenic lithospheric mantle that would be generated by underplate reaction of the subcontinental lithospheric mantle with hydrous felsic melts derived from the subducted continental crust during the Triassic continental collision. On the other hand, there are general similarities in trace element and radiogenic isotope characteristics between the syenite-granite and UHP metaigneous rocks in the Dabie-Sulu orogenic belt, suggesting its genetic link to the subducted continental crust itself. Therefore, the alkaline rocks are derived from partial melting of the orogenic lithospheric mantle and the subducted continental crust in the stage of exhumation. They provide a petrological record of recycling the subducted continental crust into mantle depths with consequent crust-mantle interaction during the continental collision. © 2011 Elsevier B.V.

Luo X.,PLA Air Force Aviation University | Xu J.,PLA Air Force Aviation University | Xu J.,Northwest University, China | Bai E.,PLA Air Force Aviation University | Li W.,Airport Management Office
Construction and Building Materials | Year: 2012

Alkali-activated slag-fly ash cementitious material system (CMS-ASF) was prepared by using NaOH (NH), Na 2CO 3 (NC) as alkali-activator and slag, fly ash as composite material. The basic characteristics, including temperature-stimulating, strength, setting and hardening, application, of CMS-ASF were systematically studied based on the paste specimen. The results showed that the rheological characterization and mechanical properties were sensitive to the change of alkali-activator temperature. Reliable strength system that endures the examination of practice was established by Response Surface Methodology, the strength system can provide a direction for practical application and used in developing theory research. When alkali-activator temperature is 40 °C, the setting time conformed to the requirements of national standard. CMS-ASF has following application characteristics: simple manufacturing technique, low cost in production, eco-friendly. So CMS-ASF has a series of excellent characteristics, there is a bright future development prospect. © 2011 Elsevier Ltd. All rights reserved.

Zhang H.-F.,Northwest University, China | Zhang H.-F.,CAS Institute of Geology and Geophysics
Gondwana Research | Year: 2012

Zircons from granulite xenoliths entrained in a Late Cretaceous mafic dike in the Jiaodong Peninsula, North China Craton (NCC), show three distinct U-Pb age populations. Part of the old zircon grains yield discordant data that project to ages of about 2.4 to 2.5Ga, a few grains indicate growth at about 2.0Ga and a third group yield Cretaceous ages with peaks at 120 and 90Ma. The oldest zircons give Hf TDM model ages of 2.6-2.8Ga. These results demonstrate the existence of original Archean lower crust in the Jiaodong region. Zircons of 2.0Ga have similar Hf TDM model ages as the Neoarchean-Paleoproterozoic grains, suggesting that these zircons were products of metamorphic recrystallization due to thermal event without juvenile input. Early Cretaceous zircons yield εHf(t) values of -21 to -12 and Late Cretaceous zircons large variable εHf(t) from +4 to -50. These data suggest that magmatic underplating occurred in the Neoarchean to Earliest Proterozoic lower crust of the NCC, both in the Early and Late Cretaceous. It is suggested that the Mesozoic magma underplating, which also provided the heat source for the voluminous Mesozoic magmatism in the NCC, significantly modified the composition of the Archean to Paleoproterozoic lower crust of the NCC. © 2011 International Association for Gondwana Research.

Zhang J.,Hefei University of Technology | Zhao Z.-F.,Hefei University of Technology | Zheng Y.-F.,Hefei University of Technology | Liu X.,Northwest University, China | Xie L.,CAS Institute of Geology and Geophysics
Lithos | Year: 2012

Postcollisional mafic to felsic dykes in the western part of the Sulu orogen consist of monzogranite, diorite, plagioclase-bearing hornblendite and gabbro. LA-ICPMS zircon U-Pb dating yielded broadly consistent ages of 111±3 to 129±1Ma for their crystallization, with Neoproterozoic ages of 743±9 to 773±9Ma for residual cores. The mafic to felsic dykes are characterized by the arc-like patterns of trace element distribution with positive LILE and LREE anomalies but negative HFSE anomalies in the spidergram. They have high initial 87Sr/ 86Sr ratios of 0.7079 to 0.7100 and variably negative ε Nd(t) values of -21.6 to -13.6 for whole-rock. Zircons also have highly negative ε Hf(t) values of -36.7 to -10.6, with two-stage Hf model ages of 1.84 to 3.47Ga. The zircons exhibit relatively consistent δ 18O values of 4.57 to 5.98‰, only some of them being slightly deviated from those for the normal mantle. The radiogenic isotope signatures for the mafic dykes require their derivations from isotopically enriched mantle sources, whereas the trace element compositions suggest that the mantle sources were metasomatized by arc-like crustal melts. Thus, the mantle sources may be generated by the reaction between the mantle-wedge peridotite and the felsic melts from the subducting continental crust during the Triassic continental collision. Nevertheless, there are significant differences in some element contents and slight differences in Nd-Hf isotope compositions between the gabbro and hornblendite, suggesting their derivation from different compositions of orogenic lithospheric mantle. The gabbro has relatively high MgO, Cr and Ni contents but low Al 2O 3 contents, indicating its derivation from an orthopyroxene-rich mantle source. The hornblendite displays relatively high Al 2O 3 and K 2O contents but low MgO, Cr and Ni contents, suggesting its derivation from a hydrous (amphibole-rich) mantle source. On the other hand, there are general similarities in element and isotope characteristics between the felsic-intermediate dykes (monzogranite and diorite) and the widespread postcollisional Early Cretaceous granitoids in the Dabie-Sulu orogenic belt. This indicates their derivation from similar crustal sources, i.e. the subducted continental crust of the South China Block. Therefore, the mafic to felsic dykes originated from partial melting of the orogenic lithosphere that included ultramafic pyroxenite and hornblendite which acted as sources for the mafic magmatism. © 2011 Elsevier B.V.

Sheng Y.-M.,Hefei University of Technology | Zheng Y.-F.,Hefei University of Technology | Chen R.-X.,Hefei University of Technology | Li Q.,CAS Institute of Geology and Geophysics | Dai M.,Northwest University, China
Lithos | Year: 2012

In-situ SIMS analyses of O and U-Pb isotopes as well as LA-(MC)-ICPMS analyses of trace elements, U-Pb, and Lu-Hf isotopes were carried out for zircon from a quartz vein and its host UHP eclogite in the Dabie orogen. The results are integrated to decipher the effect of aqueous fluid on the new growth of metamorphic zircon and on the recrystallization of protolith zircon during continental subduction-zone metamorphism. Most zircons show distinct core-(mantle)-rim structures in CL images. The rims are unzoned and have low trace element contents, low Th/U ratios of 0.003 to 0.06 and shallow MREE-HREE patterns, and insignificant negative Eu anomalies, indicating their growth from metamorphic fluid. The rims from the vein have concordant U-Pb ages of 222±6 to 212±4Ma, suggesting protracted growth during exhumation of the deeply subducted continental crust. In contrast, the rims from the eclogite gave two groups of concordant U-Pb ages at 221±3 and 208±3Ma, respectively, corresponding to two episodes of fluid action. The all rims have relatively uniformly negative δ 18O values of -2.59 to -1.23‰ for the vein and -3.37 to -0.33‰ for the eclogite, suggesting their growth from negative δ 18O metamorphic fluids of the same origin. The cores exhibit clearly oscillatory or patchy zonation, high trace element contents, high Th/U ratios of 0.13 to 2.12, steep MREE-HREE patterns, and significant negative Eu anomalies. They gave discordia Neoproterozoic upper-intercept U-Pb ages for the both vein and eclogite. Most cores have discordant U-Pb ages and variably positive δ 18O values, with no correlation between the two variables. This suggests non-linear isotope alteration of the protolith zircon by metamorphic recrystallization in the presence of aqueous fluid. The highest δ 18O value of 4.76‰ with the concordant Neoproterozoic U-Pb age is considered as a proxy for the primary δ 18O value for the protolith zircon. In this regard, the cores would crystallize from slightly low δ 18O magmas in the Neoproterozoic, and interacted with the negative δ 18O fluids of metamorphic origin in the Triassic. In particular, the cores in the vein are the xenocrystal that was trapped by the metamorphic fluids from the eclogite. Therefore, the occurrence of the both magmatic cores and metamorphic growth in the vein suggests that sinking of the metamorphic fluids into eclogite factures brought about both the physical transport of protolith zircon and the chemical transport of element Zr during the continental collision. © 2011 Elsevier B.V.

Cheng B.,Tohoku University | Cheng B.,Northwest University, China | Zhao D.,Tohoku University | Zhang G.,Northwest University, China
Physics of the Earth and Planetary Interiors | Year: 2011

In order to understand the generation mechanism of the Iwate-Miyagi earthquake (M 7.2) that occurred on 14 June 2008 in Northeast Japan, we determined high-resolution 3D seismic velocity (Vp, Vs) and Poisson's ratio (σ) structures as well as P-wave azimuthal anisotropy in and around the source area using 246,623 P-wave and 189,153 S-wave high-quality arrival times from 1941 aftershocks of the 2008 Iwate-Miyagi earthquake as well as 4878 shallow and intermediate-depth earthquakes in this area recorded by the dense High-Sensitivity Seismic Network (Hi-net) and the seismic stations of Tohoku University. Our results show that hypocenters of the mainshock and three large aftershocks are located in a boundary zone where both seismic velocity and Poisson's ratio change drastically in a short distance. A zone with pronounced low-velocity and high Poisson's ratio is revealed in the lower crust and uppermost mantle under the source area, which may reflect the arc magma and fluids ascending from the upper-mantle wedge. The P-wave azimuthal anisotropy is complex under the study area, which may also indicate the complex crustal structure there. These results indicate that the generation of the 2008 Iwate-Miyagi earthquake was influenced by the ascending arc magma and fluids associated with the dehydration reactions of the subducting Pacific slab under Northeast Japan. © 2010 Elsevier B.V.

Xu L.,Northwest University, China | Wang J.,Xi'an Jiaotong University | Chen Q.,Tsinghua University
Energy Conversion and Management | Year: 2012

Extended Kalman filtering is an intelligent and optimal means for estimating the state of a dynamic system. In order to use extended Kalman filtering to estimate the state of charge (SOC), we require a mathematical model that can accurately capture the dynamics of battery pack. In this paper, we propose a stochastic fuzzy neural network (SFNN) instead of the traditional neural network that has filtering effect on noisy input to model the battery nonlinear dynamic. Then, the paper studies the extended Kalman filtering SOC estimation method based on a SFNN model. The modeling test is realized on an 80 Ah Ni/MH battery pack and the Federal Urban Driving Schedule (FUDS) cycle is used to verify the SOC estimation method. The maximum SOC estimation error is 0.6% compared with the real SOC obtained from the discharging test. © 2011 Elsevier Ltd. All rights reserved.

Li Z.,Northwest University, China | Lu X.,University of Jinan
Energy Procedia | Year: 2011

We investigate the multifractal characteristics of the volatility time series from China's agricultural commodity futures markets, using Multifractal Detrended Fluctuation Analysis and multifractal spectrum analysis. We find that prominent multifractal features exit in China's major agricultural commodity futures markets, including the Hard Winter Wheat (HW) futures, the Strong Gluten Wheat (SG) futures, Soy Bean (SB) futures and corn futures. Furthermore, the multifractality strength and multifractal spectrum width of HW futures are both bigger than that of SG, SB and corn futures, implying that the market risk for HW futures might be the strongest among all the four futures contracts. Finally, comparing empirical results of shuffling and surrogate data, we also find that nonlinear temporal correlations instead of non-Gaussian distribution constitute the major contributions in the formation of multifractal features in these four agricultural commodity futures markets. © 2011 Published by Elsevier Ltd.

Zheng L.,Northwest University, China | Zheng L.,Xi'an Shiyou University | Song J.-F.,Northwest University, China
Journal of Solid State Electrochemistry | Year: 2010

A modified electrode Ni(II)-Qu-MWCNT-PE has been fabricated by electrodepositing nickel(II)-quercetin [Ni(II)-Qu] complex on the surface of multi-wall carbon nanotube paste electrode (MWCNT-PE) in alkaline solution. Ni(II)-Qu-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)-MWCNT-PE and Ni(II)-Qu-carbon paste electrode. It also shows electrocatalytic activity toward the oxidation of methanol and other short chain aliphatic alcohols, such as ethanol, 1-propanol, and 1-butanol. The catalytic peak current and peak potential decrease in exponential form with the increase of carbon number of the chains. Kinetic parameters such as the electron transfer coefficient, α, rate constant, k s, of the electrode reaction, and the catalytic rate constant, k cat, for oxidation of methanol are determined. The stability and reproducibility of the Ni(II)-Qu-MWCNT-PE are good for practical applications. © 2009 Springer-Verlag.

Liu C.,University of Hong Kong | Zhao G.,University of Hong Kong | Sun M.,University of Hong Kong | Zhang J.,University of Hong Kong | And 4 more authors.
Gondwana Research | Year: 2011

There is a broad consensus that the North China Craton formed by the amalgamation of the Western and Eastern Blocks along the nearly N-S trending Trans-North China Orogen. However, it still remains controversial whether the Western and Eastern Blocks collided at ~2.5Ga or ~1.85Ga. U-Pb ages and Hf isotopic data of detrital zircons from foreland basins in the Trans-North China Orogen can place rigorous constraints on this controversial issue. One of such foreland basins is represented by the Hutuo Group in the Wutai Complex in the middle sector of the Trans-North China Orogen. The sequences of the Hutuo Group range from lower basal conglomerates and sandstones (Doucun Subgroup), through clastic sediments, dolomites and meta-basalts (Lower Dongye Subgroup), phyllites and dolomites (Upper Dongye Subgroup), to coarse-grained sandstones and conglomerates at the top (Guojiazhai Subgroup), most of which contain large amounts of detrital zircons. The detrital zircons from the Doucun, Lower Dongye, Upper Dongye and Guojiazhai Subgroups yield concordant 207Pb/206Pb ages of 2.11-3.88Ga, 2.01-2.84Ga, 1.88-2.72Ga and 1.92-2.65Ga respectively, the majority with Neoarchean to Paleoproterozoic ages. The presence of ~1.88Ga detrital zircons in the Upper Dongye and Guojiazhai Subgroups indicates that they deposited at some time after ~1.88Ga. This is in accordance with collision between the Eastern and Western Blocks along the Trans-North China Orogen to form the North China Craton at ~1.85Ga. © 2010 International Association for Gondwana Research.

Zhao Y.-Y.,Northwest University, China | Lei P.,Shaanxi Microbiology Research Institute | Chen D.-Q.,Northwest University, China | Feng Y.-L.,Northwest University, China | Bai X.,Waters Technologies Shanghai Ltd
Journal of Pharmaceutical and Biomedical Analysis | Year: 2013

Poria cocos epidermis is one of ancient traditional Chinese medicines (TCMs), which is usually used for the treatment of chronic kidney disease (CKD) for thousands of years in China. A metabonomic approach based on ultra performance liquid chromatography coupled with quadrupole time-of-flight high-sensitivity mass spectrometry (UPLC Q-TOF/HSMS) and a mass spectrometryElevated Energy (MSE) data collection technique was developed to obtained a systematic view of the development and progression of CKD and biochemistry mechanism of therapeutic effects of P. cocos epidermis (Fu-Ling-Pi, FLP). By partial least squares-discriminate analysis, 19 metabolites were identified as potential biomarkers of CKD. Among the 19 biomarkers, 10 biomarkers including eicosapentaenoic acid, docosahexaenoic acid, lysoPC(20:4), lysoPC(18:2), lysoPC(15:0), lysoPE(20:0/0:0), indoxyl sulfate, hippuric acid, p-cresol sulfate and allantoin were reversed to the control level in FLP-treated groups. The study indicates that FLP treatment can ameliorate CKD by intervening in some dominating metabolic pathways, such as fatty acid metabolism, phospholipid metabolism, purine metabolism and tryptophan metabolism. This work was for the first time to investigate the FLP therapeutic effect based on metabonomics technology, which is a potentially powerful tool to study the TCMs. © 2013 Elsevier B.V.

Zhai M.,Northwest University, China | Zhai M.,CAS Institute of Geology and Geophysics
Geoscience Frontiers | Year: 2014

The North China Craton (NCC) has a complicated evolutionary history with multi-stage crustal growth, recording nearly all important geological events in the early geotectonic history of the Earth. Our studies propose that the NCC can be divided into six micro-blocks with >∼3.0-3.8 Ga old continental nuclei that are surrounded by Neoarchean greenstone belts (GRB). The micro-blocks are also termed as high-grade regions (HGR) and are mainly composed of orthogneisses with minor gabbros and BIF-bearing supracrustal beds or lenses, all of which underwent strong deformation and metamorphism of granulite- to high-grade amphibolite-facies. The micro-blocks are, in turn, from east to west, the Jiaoliao (JL), Qianhuai (QH), Ordos (ODS), Ji'ning (JN) and Alashan (ALS) blocks, and Xuchang (XCH) in the south. Recent studies led to a consensus that the basement of the NCC was composed of different blocks/terranes that were finally amalgamated to form a coherent craton at the end of Neoarchean. Zircon U-Pb data show that TTG gneisses in the HGRs have two prominent age peaks at ca. 2.9-2.7 and 2.6-2.5 Ga which may correspond to the earliest events of major crustal growth in the NCC. Hafnium isotopic model ages range from ca. 3.8 to 2.5 Ga and mostly are in the range of 3.0-2.6 Ga with a peak at 2.82 Ga. Recent studies revealed a much larger volume of TTG gneisses in the NCC than previously considered, with a dominant ca. 2.7 Ga magmatic zircon ages. Most of the ca. 2.7 Ga TTG gneisses underwent metamorphism in 2.6-2.5 Ga as indicated by ubiquitous metamorphic rims around the cores of magmatic zircon in these rocks. Abundant ca. 2.6-2.5 Ga orthogneisses have Hf-in-zircon and Nd whole-rock model ages mostly around 2.9-2.7 Ga and some around 2.6-2.5 Ga, indicating the timing of protolith formation or extraction of the protolith magma was from the mantle. Therefore, it is suggested that the 2.6-2.5 Ga TTGs probably represent a coherent event of continental accretion and major reworking (crustal melting). As a distinct characteristic, nearly all GRBs in the NCC underwent amphibolite-facies metamorphism. Zircon U-Pb ages of metamorphosed GRB mafic rocks mainly show two peak ranges at ∼2.6-2.5 and 2.8-2.7 Ga. The mafic rocks are commonly believed to be derived from metabasalts, it is therefore possible that the ages represent the time of metamorphism. The tectonic settings of the GRBs are still a problem. Their geochemical characteristics are, respectively, similar to back-arc basins, rifts, island arcs or suggest imprints of mantle plumes. BIFs occur in all GRBs but also in the HGRs. This metallogenic specificity is quite different from all Phanerozoic geotectonic settings. The ∼2.5 Ga metamorphic-magmatic event is stronger than in most other cratons in the world. How to understand the geological significance of the 2.5 Ga event? The following points are emphasized: (1) nearly all old rocks >2.5 Ga underwent metamorphism at ∼2.52-2.5 Ga; (2) Archean basement rocks in the NCC experienced strong partial melting and migmatization; (3) granitoid rocks derived from partial melting include potassium granites, TTG granites and monzonites. These granitoids rocks intruded both the Archean greenstone belts and micro-blocks; (4) ∼2.5 Ga mafic dikes (amphibolites), granitic dikes (veins) and syenitic-ultramafic dykes are also developed. Therefore, we suggest an assembly model that all micro-blocks in the NCC were welded together by late Archean greenstone belts at the end of the late Neoarchean. We also propose that the various micro-blocks were surrounded by small ocean basins, and the old continental crust and the oceanic crust were hotter than today. Subduction and collision were on much smaller scales as compared to the Phanerozoic plate tectonic regime, although the tectonic style and mechanisms were more or less similar. The formation of crustal melt granites is one of the processes of cratonization, inducing generation of stable upper and lower crustal layers. This process also generated an upper crust of more felsic composition and a lower crust of more mafic composition, due to molten residual materials and some underplated gabbros. © 2014, China University of Geosciences (Beijing) and Peking University.

Wang J.-G.,Northwest University, China | Wang J.-G.,Tsinghua University | Wei B.,Northwest University, China | Wei B.,University of Delaware | Kang F.,Tsinghua University
RSC Advances | Year: 2014

We report an eco-friendly and one-step route for the chemical synthesis of hierarchical conducting polypyrrole (PPy) nanostructures via a reactive template of MnO2. The as-prepared PPy nanotubes are found to show good electrical conductivity and superior electrochemical properties for supercapacitor applications. © 2014 The Royal Society of Chemistry.

Chen Q.,Sun Yat Sen University | Lin J.-B.,Sun Yat Sen University | Xue W.,Sun Yat Sen University | Zeng M.-H.,Northwest University, China | Chen X.-M.,Sun Yat Sen University
Inorganic Chemistry | Year: 2011

A microporous coordination polymer, namely, [Co3(ina) 4(OH)(C2H5OH)3](NO3) · C2H5OH· (H2O)3 (1, or MCF-38, ina = isonicotinate), with 8-connected {Co3(OH)} clusters as the structural secondary building units, has been solvothermally synthesized. The hydroxo-centered Co(II) cluster involves multiple active metal sites. The interesting apical ligand substitutions have been directly observed, and the corresponding products of [Co3(ina)4(OH)(G) x(H2O)n](NO3) · G· (H2O)m (1 ⊃ PrOH, G = PrOH, x = 2, n =1, m = 3; 1 ⊃ BuOH, G = BuOH, x = 2, n = 1, m = 1, and 1 ⊃ MeOH,G = MeOH, x = 3, n = 0, m = 7) have also been obtained by solvothermal syntheses or crystal-to-crystal transformations. High-pressure H2 adsorption measurement at 77 K reveals that activated 1 can absorb 2.2 wt % H2 at 5 bar. Therelative H2 absorption at low pressure (86% of the storage capacity at 1 bar) is higher than the corresponding values reported for some typical porous coordination polymers. The magnetic studies of 1 show a dominant antiferromagnetic coupling between Co(II) ions of intra-and inter-cluster. © 2011 American Chemical Society.

Lei Q.-P.,CAS Nanjing Institute of Geology and Palaeontology | Lei Q.-P.,University of Chinese Academy of Sciences | Han J.,Northwest University, China | Ou Q.,China University of Geosciences | Wan X.-Q.,China University of Geosciences
Gondwana Research | Year: 2014

Substrates have perpetually played a crucial role in shaping the morphology of animal bodies, particularly the sedentary apparatus of benthic suspension feeders. In-situ preservation of sedentary forms from Cambrian Lagerstätten, especially the Lower Cambrian Chengjiang Lagerstätte, Yunnan Province, southwestern China, provides a unique opportunity for studying ancient interactions between the benthos and their substrates. The sedentary apparatuses of anthozoa-like animals Xianguangia sinica Chen & Erdtmann, 1991, Archotuba conoidalis Hou et al., 1999 and Archisaccophyllia kunmingensis Hou et al., 2005 from the Chengjiang Lagerstätte are investigated in their sedimentary context. X. sinica bears a cylindrical, rigid column and a basal, rounded, cuticularized attachment disc that partially attached into the soft muddy substrate; A. kunmingensis has a prominent, flexible pedal-shaped disc that attached directly to the substrate by expanding its disc surface area; whereas A. conoidalis has a unique, posterior-tapering tube and probably might have secreted mucus to firmly attach to the 'sclerotized' substrates. These three sedentary taxa employed different adaptive strategies, i.e., the 'iceberg', the 'snowshoe' and one newly defined but later widespread in Phanerozoic period, the 'anchoring-nail', to cope with the soft substrates. Furthermore, the anchoring-nail mode, sclerite-sticking behavior represented by Archotuba is a Phanerozoic innovative strategy in response to the appearance of pelagic larvae and small shelly fossils, especially to the first widespread biomineralization event at the beginning of the Cambrian, whereas the other two modes have already developed for about 90. Ma from the Ediacaran. © 2012 International Association for Gondwana Research.

Dai T.,Northwest University, China | Dai T.,CAS Nanjing Institute of Geology and Palaeontology | Zhang X.,Northwest University, China | Peng S.,CAS Nanjing Institute of Geology and Palaeontology
Gondwana Research | Year: 2014

The juvenile morphology and ontogeny of the Cheiruroidid trilobite Hunanocephalus ovalis Lee, 1963 from the lower Cambrian Shuijingtuo Formation in Hubei Province, South China is presented. The new material comprises a relatively complete meraspid ontogenetic series (degree 0 to 10), which reveals more details on their morphological changes such as the contraction and disappearance of the pronounced posteromedial notch in the pygidium and the addition of the trunk segments, which are all documented for the first time and can also be used as developmental markers defining their ontogenetic phases. The trunk segmentation schedule of H. ovalis is also discussed, which is similar to the other early Cambrian oryctocephalid trilobites, i.e. as the boundary between the thorax and pygidium migrated posteriorly there is no change in the trunk segment number; the processes of liberation of the thoracic segment and segment insertion into the pygidium are separated from one another, implying that the control of trunk exoskeletal segment appearance and articulation might be decoupled in these trilobites. © 2013 International Association for Gondwana Research.

Luo D.,South China Agricultural University | Luo D.,Guangxi University | Xu H.,South China Agricultural University | Xu H.,Northwest University, China | And 17 more authors.
Nature Genetics | Year: 2013

Plant cytoplasmic male sterility (CMS) results from incompatibilities between the organellar and nuclear genomes and prevents self pollination, enabling hybrid crop breeding to increase yields. The Wild Abortive CMS (CMS-WA) has been exploited in the majority of 'three-line' hybrid rice production since the 1970s, but the molecular basis of this trait remains unknown. Here we report that a new mitochondrial gene, WA352, which originated recently in wild rice, confers CMS-WA because the protein it encodes interacts with the nuclear-encoded mitochondrial protein COX11. In CMS-WA lines, WA352 accumulates preferentially in the anther tapetum, thereby inhibiting COX11 function in peroxide metabolism and triggering premature tapetal programmed cell death and consequent pollen abortion. WA352-induced sterility can be suppressed by two restorer-of-fertility (Rf) genes, suggesting the existence of different mechanisms to counteract deleterious cytoplasmic factors. Thus, CMS-related cytoplasmic-nuclear incompatibility is driven by a detrimental interaction between a newly evolved mitochondrial gene and a conserved, essential nuclear gene. © 2013 Nature America, Inc. All rights reserved.

Zhang H.-F.,Northwest University, China | Zhang H.-F.,CAS Institute of Geology and Geophysics
Precambrian Research | Year: 2014

Oxygen isotope analyses were carried out using SIMS technique (Cameca-1280) on zircons from well-studied lower crust xenoliths/xenocrysts from the North China Craton (NCC). The results show that magmatic zircons with Archean-Paleoproterozoic 207Pb/206Pb ages have an extremely large variation in δ18O values that range from less than normal mantle value (4.74±0.28‰ (2σ)) to 18O-enriched supracrustal value (8.88±0.40‰ (2σ)) and differ in localities of the NCC (δ18OQindao from 5.27±0.45‰ to 8.88±0.40‰ δ18OHannuoba from 6.78±0.23‰ to 7.69±0.41‰ δ18OXiuyan from 4.74±0.28‰ to 6.57±0.39‰). Such a variation demonstrates that the Neoarchean lower crust beneath the NCC was highly heterogeneous in oxygen isotope compositions, even in an individual region. The fact that the predominant zircons have high δ18O values suggests that the recycling of 18O-enriched supracrustal materials into the Neoarchean lower crust indeed happened during zircon crystallization. Some zircons with core-rim texture have nearly identical δ18O both in core and its rim. On the other hand, others have a distinctive oxygen isotope ratio between the core and its rim, possessing slightly higher δ18O in the rim than its core or vice versa. Such an oxygen isotope feature in zoned zircons suggests a complicated evolutional history of ancient lower crust in the NCC. This study provides convincing evidence that a large amounts of the supracrustal materials have been recycled into the Neoarchean lower crust beneath the NCC, a process resulting in the highly heterogeneity in oxygen isotopes. © 2014 Elsevier B.V.

Yang Y.,Northwest University, China | Yang Y.,Tsinghua University | Ma H.,Northwest University, China | Zhuang J.,Tsinghua University | Wang X.,Tsinghua University
Inorganic Chemistry | Year: 2011

An oriented attachment growth process was found for the morphology and shape control of various inorganic materials in solution-based systems. In this Article, a well-defined iron oxide polyhedron was prepared via a simple hydrothermal method. Detailed investigations revealed that the single-crystalline polyhedron evolved from polycrystalline aggregates. The shape and size control of the iron oxide crystals were achieved by simply adjusting the synthesis parameters. The as-prepared products exhibit excellent gas sensing selectivity to ethanol vapor. The gas-sensing ability is closely related to the exposure of high-index facets. © 2011 American Chemical Society.

Zhang X.,Tsinghua University | Hui J.,Northwest University, China | Yang B.,Tsinghua University | Yang Y.,Tsinghua University | And 4 more authors.
Polymer Chemistry | Year: 2013

PEGylation is a popular approach for the surface functionalization of nanoparticles to achieve improved properties and better performance. Herein, we developed a facile method for surface PEGylation of hydrophobic fluoridated hydroxyapatite (FAp):Ln3+ (Ln = Eu or Tb) nanorods via hydrophobic interactions between oleic acid and amphiphilic synthetic copolymers, which were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization using stearyl methacrylate (SMA) and poly(ethylene glycol) methacrylate (PEGMA) as monomers. Our results demonstrated that the morphology and fluorescent properties of the FAp nanorods are not significantly changed by the PEGylation procedure, and the resulting FAp nanorods were found to be stable in aqueous solution. More importantly, these PEGylated FAp nanorods are biocompatible with cells and could be utilized for cell imaging applications. Therefore, we believe that the method described in this work is a simple, efficient and general strategy for the surface PEGylation of hydrophobic nanoparticles. This journal is © 2013 The Royal Society of Chemistry.

Wu B.,Arizona Center for Reproductive Endocrinology and Infertility | Zan L.,Northwest University, China
Reproduction in Domestic Animals | Year: 2012

Embryo biotechnology has become one of the prominent high businesses worldwide. This technology has evolved through three major changes, that is, traditional embryo transfer (in vivo embryo production by donor superovulation), in vitro embryo production by ovum pick up with in vitro fertilization and notably current cloning technique by somatic cell nuclear transfer and transgenic animal production. Embryo biotechnology has widely been used in dairy and beef cattle industry and commercial bovine embryo transfer has become a large international business. Currently, many developed biotechnologies during the period from early oocyte stage to pre-implantation embryos can be used to create new animal breeds and accelerate genetic progression. Based on recent advances in embryo biotechnologies and authors current studies, this review will focus on a description of the application of this technology to beef cattle improvement and discuss how to use this technology to accelerate beef cattle breeding and production. The main topics of this presentation include the following: (i) how to increase calf production numbers from gametes including sperm and oocyte; (ii) multiple ovulation and embryo transfer breeding schemes; (iii) in vitro fertilization and intracytoplasm sperm injection in bovine; (iv) pronuclear development and transgenic animals; (v) sex selection from sperm and embryos; (vi) cloning and androgenesis; (vii) blastocyst development and embryonic stem cells; (viii) preservation of beef cattle genetic resources; and (ix) conclusions. © 2011 Blackwell Verlag GmbH.

Liu T.-X.,Northwest University, China | Stansly P.A.,University of Florida | Gerling D.,Tel Aviv University
Annual Review of Entomology | Year: 2015

Whiteflies are small hemipterans numbering more than 1,550 described species, of which about 50 are agricultural pests. Adults are free-living, whereas late first to fourth instars are sessile on the plant. All known species of whitefly parasitoids belong to Hymenoptera; two genera, Encarsia and Eretmocerus, occur worldwide, and others are mostly specific to different continents. All parasitoid eggs are laid in-or in Eretmocerus, under-the host. They develop within whitefly nymphs and emerge from the fourth instar, and in Cales, from either the third or fourth instar. Parasitized hosts are recognized by conspecifics, but super- and hyperparasitism occur. Dispersal flights are influenced by gender and mating status, but no long-range attraction to whitefly presence on leaves is known. Studies on En. formosa have laid the foundation for behavioral studies and biological control in general. We review past and ongoing studies of whitefly parasitoids worldwide, updating available information on species diversity, biology, behavior, tritrophic interactions, and utilization in pest management. © 2015 by Annual Reviews. All rights reserved.

Zhao X.,Northwest University, China | Schaffner D.W.,Rutgers University | Yue T.,Northwest University, China
Food Control | Year: 2013

The purpose of this study was to estimate the risk of illness posed by aflatoxin B1 resulting from consumption of Chinese spices. Quantitative estimates of cancer risk from aflatoxin B1 residues were constructed based on 480 retail samples of various spices in China. The samples were comprised of pepper, chili, prickly ash, cinnamon, aniseed, fennel, curry powder, cumin and ginger. All of the samples were analyzed for aflatoxin B1 content by high-performance liquid chromatography (HPLC). The risk assessment included the variability in aflatoxin concentration in Chinese spices; the variability in spice consumption by the Chinese population as represented by surrogate data from 5 other counties or regions and the influence of Hepatitis B infection on cancer risk. The risk assessment compared three different mitigation scenarios where aflatoxin levels above different thresholds were excluded. Our results show that about 11% of the 480 Chinese spices samples tested contained detectible levels of aflatoxin, with the highest concentrations found in chili, prickly ash and pepper. The deterministic risk assessment shows that assumptions about spice consumption patterns do have an effect on estimated risk for those infected with Hepatitis B and excluding spices with higher levels of aflatoxin can reduce risk in some cases. Both probabilistic risk assessments estimated higher levels of risk when compared to the deterministic risk assessment. Aflatoxin concentration produced in this manuscript are consistent with those reported by others, and our estimates indicate that spices may contribute about 10% of all Chinese exposure to aflatoxin. © 2013 Elsevier Ltd.

Zhou Z.,Northwest University, China | Jiang F.,Northwest University, China | Lee T.-C.,Rutgers University | Yue T.,Northwest University, China
Journal of Alloys and Compounds | Year: 2013

A new two-step route for the preparation of nano-scaled magnetic chitosan particles has been developed, different from reported one-step in situ preparation and two-step preparation method of reversed-phase suspension, Triton X-100 reversed-phase water-in-oil microemulsion encapsulation method was employed in coating the pre-prepared Fe3O4 nanoparticles with chitosan. The resultant magnetic chitosan particles owned a narrow size distribution ranging from 50 to 92 nm. X-ray diffraction patterns (XRD) indicated that the chitosan coating procedure did not change the spinal structure of Fe3O4 magnetic nanoparticles. The results of Fourier transform infrared (FTIR) analysis and thermogravimetric analysis (TGA) demonstrated that the chitosan was coated on Fe3O4 nanoparticles and its average mass content was ~50%. The saturated magnetization of the magnetic Fe3O4/chitosan nanoparticles reached 18.62 emu/g, meanwhile, the nanoparticles showed the characteristics of superparamagnetism. The magnetic chitosan nanoparticles showed a high recoverability of 99.99% in 10 min when pH exceeded 4. The results suggested that the as-prepared magnetic chitosan particles were nano-scaled with a narrow size distribution and a high recoverability. © 2013 Elsevier B.V. All rights reserved.

Zhang J.,Northwest University, China | Siika-Aho M.,VTT Technical Research Center of Finland | Puranen T.,Roal Oy | Tang M.,Northwest University, China | And 2 more authors.
Biotechnology for Biofuels | Year: 2011

Background: In the hydrolysis of lignocellulosic materials, thermostable enzymes decrease the amount of enzyme needed due to higher specific activity and elongate the hydrolysis time due to improved stability. For cost-efficient use of enzymes in large-scale industrial applications, high-level expression of enzymes in recombinant hosts is usually a prerequisite. The main aim of the present study was to compare the biochemical and hydrolytic properties of two thermostable recombinant glycosyl hydrolase families 10 and 11 (GH10 and GH11, respectively) xylanases with respect to their potential application in the hydrolysis of lignocellulosic substrates. Results: The xylanases from Nonomuraea flexuosa (Nf Xyn11A) and from Thermoascus aurantiacus (Ta Xyn10A) were purified by heat treatment and gel permeation chromatography. Ta Xyn10A exhibited higher hydrolytic efficiency than Nf Xyn11A toward birchwood glucuronoxylan, insoluble oat spelt arabinoxylan and hydrothermally pretreated wheat straw, and it produced more reducing sugars. Oligosaccharides from xylobiose to xylopentaose as well as higher degree of polymerization (DP) xylooligosaccharides (XOSs), but not xylose, were released during the initial hydrolysis of xylans by Nf Xyn11A, indicating its potential for the production of XOS. The mode of action of Nf Xyn11A and Ta Xyn10A on glucuronoxylan and arabinoxylan showed typical production patterns of endoxylanases belonging to GH11 and GH10, respectively. Conclusions: Because of its high catalytic activity and good thermostability, T. aurantiacus xylanase shows great potential for applications aimed at total hydrolysis of lignocellulosic materials for platform sugars, whereas N. flexuosa xylanase shows more significant potential for the production of XOSs. © 2011 Zhang et al; licensee BioMed Central Ltd.

Gao Q.-H.,Northwest University, China | Wu C.-S.,Jiangnan University | Wang M.,Northwest University, China
Journal of Agricultural and Food Chemistry | Year: 2013

The nutritional jujube (Ziziphus jujube Mill.) fruit belonging to the Rhamnaceous family grows mostly in Europe, southern and eastern Asia, and Australia, especially the inland region of northern China. Jujube has a long history of usage as a fruit and remedy. The main biologically active components are vitamin C, phenolics, flavonoids, triterpenic acids, and polysaccharides. Recent phytochemical studies of jujube fruits have shed some light on their biological effects, such as the anticancer, anti-inflammatory, antiobesity, immunostimulating, antioxidant, hepatoprotective, and gastrointestinal protective activities and inhibition of foam cell formation in macrophages. A stronger focus on clinical studies and phytochemical definition of jujube fruits will be essential for future research efforts. This review may be useful for predicting other medicinal uses and potential drug or food interactions and may be beneficial for people living where the jujube fruits are prevalent and health care resources are scarce. © 2013 American Chemical Society.

Su X.,Northwest University, China | Li J.,Huizhou City Huayu Water Resources and Hydropower Engineering investigation Co. | Singh V.P.,Texas A&M University
Water Resources Management | Year: 2014

Without subdividing into blue and green virtual water, the virtual crop water is currently used in the allocation of water resources based on virtual water strategy. In order to improve agricultural water use efficiency and the proportion of green water utilization, a multi-objective optimal allocation model for agricultural water resources is developed in this study. The model is based on the subdivision of virtual water into blue and green virtual water, subject to three objectives of the maximum net benefit from agriculture, the minimum fairness difference in the utilization of water, and the maximum proportion of green water utilization. Taking Shiyang River basin as an example, agricultural water resources are optimized through regional virtual water trade in the basin. Results show that compared with the situation in the year 2007, the net benefit of agriculture, the fairness difference in the utilization of water, and the proportion of green water utilization are optimized. At the same time, the planting ratio of food crops, such as corn, reduces, while the planting ratio of cash crops, such as cotton, vegetables, and fruits, increases. Through regional virtual water strategy in the basin, with the crops of different districts having comparative advantages, the proportion of green water utilization and the blue water use efficiency are improved. The study provides a scientific basis to solve the water shortage problem in the basin. © 2014 Springer Science+Business Media Dordrecht.

Gao Q.-H.,Northwest University, China | Wu C.-S.,Jiangnan University | Wang M.,Northwest University, China | Xu B.-N.,Northwest University, China | Du L.-J.,Northwest University, China
Journal of Agricultural and Food Chemistry | Year: 2012

This study investigated the changes in sugars, organic acids, α-tocopherol, β-carotene, phenolic profiles, total phenolic content (TPC), and antioxidant capacity of jujube fruits after four drying treatments (sun-, oven-, microwave- and freeze-drying). Sugar, organic acid, phenolic compounds, α-tocopherol, and β-carotene were qualitatived and quantitatived by high-performance liquid chromatography. The TPC and antioxidant activity of jujube samples were evaluated using the Folin-Ciocalteau method and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity, respectively. Freeze-drying resulted in jujubes with higher antioxidant activity and was also a good choice for the preparation of β-carotene from jujubes for the food industry. Microwave-dried jujubes had a higher content of protocatechuic acid, catechin, and epicatechin and maintained the same antioxidant capacity with the freeze-dried jujubes. The combination of microwave- and freeze-drying may be an efficient alternative with shorter processing time and, consequently, less impact on the nutritional value of the jujube. © 2012 American Chemical Society.

Zhang R.,Northwest University, China | Sun Y.,Northwest University, China | Zhang X.,Northwest University, China | Ao W.,Northwest University, China | Santosh M.,China University of Geosciences
Gondwana Research | Year: 2016

Neoproterozoic magmatic rocks in the South Qinling Belt of China provide important clues for understanding the mechanism and timing of the amalgamation and breakup of the Rodinia supercontinent. Here we report new geochemical and high-precision LA-ICP-MS zircon U-Pb-Hf isotopic analyses on magmatic suites from the Liuba and Zhashui areas in the South Qinling Belt. Our data show that the crystallization ages of the granitic intrusions from Tiefodian and Tangjiagou in the Liuba area are 863 ± 22 Ma and 794 ± 11 Ma, respectively, whereas those of the dioritic and gabbroic intrusions at Chishuigou in the Zhashui area are 925 ± 28 Ma and 832.6 ± 4.0 Ma, respectively. The diorites at Chishuigou display arc-related geochemical affinity, characterized by strong depletion in Nb, Ta, P and Ti, and enrichment in large-ion lithophile elements (i.e., Rb, Ba, Th and U), indicating a subduction-related arc setting at ca. 925 Ma. The Tiefodian granitic rocks have high SiO2 (68.46-70.98 wt.%), Na2O (3.87-4.51 wt.%), and low K2O (1.34-2.61 wt.%) contents with TTG affinity. However, their Cr, and Ni contents and Cr/Ni, Nb/Ta ratios are similar to those of continental crust, and together with high negative εHf(t) values (-4.87 to -14.84), suggesting a continental margin arc at ca. 863 Ma. The gabbros at Chishuigou have high TiO2 content (2.74-3.14 wt.%), Zr/Y (3.93-4.24), Ta/Yb (0.19-0.25) ratios and low Zr/Nb ratios (11.37-13.17), similar to the features of within-plate basalts, indicating an intra-continental rift setting at ca. 833 Ma. The granitoids at Tangjiagou exhibit enrichment of LREE, K and Pb, and depletion of Nb, Ta, P and Ti, suggesting an extensional tectonic environment at ca. 794 Ma. The results indicate that Neoproterozoic magmatic rocks in the South Qinling Belt formed before ca. 833 Ma and might represent the amalgamation of the Rodinia supercontinent in an arc-related subduction environment, whereas the magmatic events with the peak ages at ~. 740 Ma during ca. 833-680 Ma represent the breakup of Rodinia. Integrating our new data with those from previous works, we propose a new tectonic model for the evolutionary history of the South Qinling Belt in the Neoproterozoic, including four key stages: 1) an ocean that separated the South Qinling Belt and the Yangtze Block in the Early Neoproterozoic (ca.1000-956 Ma); 2) bidirectional subduction of the oceanic lithosphere during ca. 956-870 Ma; 3) subduction and collision between the South Qinling Belt and the Yangtze Block during ca. 870-833 Ma, thus suggesting that the South Qinling Belt was as a part of the Yangtze Block from this period; and 4) intra-continental rifting during ca. 833-680 Ma, although the blocks were not entirely rifted apart. © 2015 International Association for Gondwana Research.

Yu Y.-C.,Northwest University, China | Yu Y.-C.,Harbin Institute of Technology | Gao D.-W.,Harbin Institute of Technology | Tao Y.,Harbin Institute of Technology
Applied Microbiology and Biotechnology | Year: 2013

In this study, anammox bacteria were rapidly enriched in sequencing batch biofilm reactors (SBBRs) with different inoculations. The activated sludge taken from a sequencing batch reactor was used and inoculated to SBBR1, while SBBR2 was seeded with stored anaerobic sludge from an upflow anaerobic fixed bed (2-year stored at 5-15 C). Nitrogen removal performance, anammox activity, biofilm characteristics and variation of the microbial community were evaluated. The maximum total nitrogen loading rate (NLR) of SBBR1 gradually reached to 1.62 kg N/(m3/day) with a removal efficiency higher than 88 % and the NLR of SBBR2 reached to 1.43 kg N/(m3/day) with a removal efficiency of 86 %. SBBR2 was more stable compared to SBBR1. These results, combined with molecular techniques such as scanning electron microscope, fluorescence in situ hybridization, and terminal restriction fragment length polymorphism, indicated that different genera of anammox bacteria became dominant. This research also demonstrates that SBBR is a promising bioreactor for starting up and enriching anammox bacteria. © 2012 Springer-Verlag Berlin Heidelberg.

Yang Z.,Jiangnan University | Zhao J.,Jiangnan University | Wei N.,Northwest University, China
Applied Physics Letters | Year: 2015

The temperature-dependent stress-strain relations of monolayer black phosphorus (BP) under biaxial and uniaxial tension as well as shear deformation are investigated using molecular dynamics (MD) simulations. The predicted strength and moduli are in good agreement with the available results from the first-principle method. In particular, the amplitude to wavelength ratio of wrinkles under shear deformation using MD simulations also agrees well with that from the existing theory. This study provides physical insights into the origins of the temperature-dependent mechanical properties of the monolayer BP. © 2015 AIP Publishing LLC.

Shu D.-G.,Northwest University, China | Shu D.-G.,China University of Geosciences | Conway Morris S.,University of Cambridge | Zhang Z.-F.,Northwest University, China | Han J.,Northwest University, China
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

While the broad framework of deuterostome evolution is now clear, the remarkable diversity of extant forms within this group has rendered the nature of the ancestral types problematic: what, for example, does the common ancestor of a sea urchin and lamprey actually look like? The answer to such questions can be addressed on the basis of remarkably well-preserved fossils from Cambrian Lagerstätten, not least the celebrated Chengjiang Lagerstätte (Yunnan, China). This deposit is particularly important because of its rich diversity of deuterostomes. These include some of the earliest known representatives, among which are the first vertebrates, as well as more enigmatic groups, notably the vetulicolians and yunnanozoans. The latter groups, in particular, have been the subject of some radical divergences in opinion as to their exact phylogenetic placements. Here, we both review the known diversity of Chengjiang deuterostomes and in particular argue that the vetulicolians and yunnanozoans represent very primitive deuterostomes. Moreover, in the latter case we present new data to indicate that the yunnanozoans are unlikely to be any sort of chordate. © 2009 The Royal Society.

Chen V.L.,Harvard University | Surana N.K.,Harvard University | Surana N.K.,Boston Childrens Hospital | Duan J.,Northwest University, China | Kasper D.L.,Harvard University
PLoS ONE | Year: 2013

Interleukin (IL)-1 signaling plays a critical role in intestinal immunology. Here, we report that the major population of intestinal lamina propria lymphocytes expressing IL-1 receptor 1 (IL-1R1) is the lymphoid tissue inducer (LTi)-like cell, a type of innate lymphoid cell. These cells are significant producers of IL-22, and this IL-22 production depends on IL-1R1 signaling. LTi-like cells are required for defense against Salmonella enterica serovar Typhimurium. Moreover, colonic LTi-like cell numbers depend on the presence of the intestinal microbiota. LTi-like cells require IL-1R1 for production of protective cytokines and confer protection in infectious colitis, and their cell numbers in the colon depend upon having a microbiome. © 2013 Chen et al.

Wang G.,Xi'an University of Science and Technology | Ren D.,Northwest University, China
Medical and Biological Engineering and Computing | Year: 2013

In order to effectively control a prosthetic system, considerable attempts have been made in recent years to improve the classification accuracy of surface electromyographic (SEMG) signals. However, the extraction of effective features is still a primary challenge for the classification of SEMG signals. This study tried to solve the problem by applying the multifractal analysis. It was found that the SEMG signals were characterized by multifractality during forearm movements and different types of forearm movements were related to different multifractal singularity spectra. To quantitatively evaluate the multifractal singularity spectra of the SEMG signals, the areas of the singularity spectrum curves were calculated by integrating the spectrum curves with respect to the singularity strengths. Our results showed that there were several separate clusters resulting from singularity spectrum areas of different forearm movements when two channels of SEMG signals were used in this experimental research, which demonstrated that the multifractal analysis approach was suitable for identifying different types of forearm movements. By comparing with other feature extraction techniques, the multifractal singularity spectrum approach provided higher classification accuracy in terms of the classification of SEMG signals. © 2012 International Federation for Medical and Biological Engineering.

Xia Z.,Northwest University, China | Qiu P.,University of Florida
Biometrika | Year: 2015

Nonparametric regression analysis when the regression function is discontinuous has many applications. Existing methods for estimating a discontinuous regression curve usually assume that the number of jumps in the regression curve is known beforehand, which is unrealistic in some situations. Although there has been research on estimation of a discontinuous regression curve when the number of jumps is unknown, the problem remains mostly open because such research often requires assumptions on other related quantities, such as a known minimum jump size. In this paper we propose a jump information criterion which consists of a term measuring the fidelity of the estimated regression curve to the observed data and a penalty related to the number of jumps and the jump sizes. The number of jumps can then be determined by minimizing our criterion. Theoretical and numerical studies show that our method works well © 2015 Biometrika Trust.

Niu J.,Hokkaido University | Yi X.,Northwest University, China | Nakatsugawa I.,Combustion Synthesis Co. | Akiyama T.,Hokkaido University
Intermetallics | Year: 2013

A novel method of producing submicron-size β-SiAlON powders by combustion synthesis using NaCl as a diluent was proposed. The combustion synthesis was carried out with the raw materials Si, SiO2, and Al powders, and varying amounts of NaCl under a nitrogen pressure of 1 MPa. Phase compositions and particle morphologies of the synthesized powders were analyzed. The results revealed that as the z-values increased, the amount of NaCl needed to complete the reaction increased, which in turn decreased the particle size of the product. With small z-values, single-phase products were obtained; however, with large z-values, NaCl and unreacted Si remained in the products due to the large amount of liquid phase. NaCl acted not only as a diluent by absorbing the heat generated by the reaction but also as a diffusion barrier between β-SiAlON particles, which greatly limited the growth of β-SiAlON crystals.©2012 Elsevier Ltd. All rights reserved.

Li S.,Northwest University, China | Li S.,Rutgers University | Huang K.,Rutgers University | Zhang J.,Northwest University, China | And 2 more authors.
Organic Letters | Year: 2013

A novel rhodium catalytic system with Naphos as ligand was developed for an efficient hydroaminomethylation of 1,1-diphenylethene under relatively mild conditions. This will allow for an atom-economic and environmentally benign synthesis of fenpiprane and related pharmaceuticals. © 2013 American Chemical Society.

Liu H.,University of Florida | Zou T.,University of Florida | Gao J.-M.,Northwest University, China | Gu L.,University of Florida
Food Chemistry | Year: 2013

Procyanidin dimers, trimers, and tetramers are absorbable, whereas larger oligomers are not. Procyanidins in cranberries are bioactive components that help prevent chronic diseases; however, 85% of cranberry procyanidins are large oligomers or polymers with a degree of polymerization above four. The objective of this study was to depolymerize cranberry procyanidins, particularly the polymers, into absorbable oligomers. Partially purified cranberry procyanidins (PCP) were obtained using chromatographic methods. The resultant extract contained predominant polymers with a degree of polymerization above ten (77.2% w/w). The extract was depolymerized, using 0.1 or 1 M methanolic HCl, with (+)-cate-chin, (-)-epicatechin, or (-)-epigallocatechin gallate (EGCG) added as chain breakers. Depolymerization converted polymers into A-type and B-type dimers, trimers and tetramers. Use of EGCG as a chain breaker resulted in A- and B-type oligomers with EGCG as a terminal unit, indicating that the added flavan-3-ol attached to the C4 carbocations from procyanidins during depolymerization. The yield of B-type oligomers was higher than that of A-type oligomers. The yield increased when higher amounts of flavan-3-ols were used for depolymerization. EGCG, as a chain breaker, produced fewer procyanidin oligomers than did catechin or epicatechin. This research provided a practical approach that may enhance the bioavailability and bioactivity of procyanidins in cranberries. © 2013 Elsevier Ltd. All rights reserved.

Wang D.,Northwest University, China | Wang D.,Xiangtan University | Xiao A.,Xiangtan University | Yang W.,Xiangtan University
Journal of Computational Physics | Year: 2014

In this paper, a linearly implicit conservative difference scheme for the coupled nonlinear Schrödinger equations with space fractional derivative is proposed. This scheme conserves the mass and energy in the discrete level and only needs to solve a linear system at each step. The existence and uniqueness of the difference solution are proved. The stability and convergence of the scheme are discussed, and it is shown to be convergent of order O(τ2 + h2) in the discrete l2 norm with the time step τ and mesh size h. When the fractional order is two, all those results are in accord with the difference scheme proposed for the classical non-fractional coupled nonlinear Schrödinger equations. Some numerical examples are also reported. © 2014 Elsevier Inc.

Geng R.,Northwest University, China | Geng R.,Yancheng Teachers University | Yuan C.,Northwest University, China | Chen Y.,Northwest University, China
PLoS ONE | Year: 2013

Cashmere goat (Capra hircus) hair follicle development and cycling can be divided into three stages: anagen, catagen and telogen. To elucidate the genes involved in hair follicle development and cycling in cashmere goats, transcriptome profiling of skin was carried out by analysing samples from three hair follicle developmental stages using RNA-Seq. The RNA-Seq analysis generated 8487344, 8142514 and 7345335 clean reads in anagen, catagen and telogen stages, respectively, which provided abundant data for further analysis. A total of 1332 differentially expressed genes (DEGs) were identified, providing evidence that the development of hair follicles among the three distinct stages changed considerably. A total of 683 genes with significant differential expression were detected between anagen and catagen, 530 DEGs were identified between anagen and telogen, and 119 DEGs were identified between catagen and telogen. A large number of DEGs were predominantly related to cellular process, cell & cell part, binding, biological regulation and metabolic process among the different stages of hair follicle development. In addition, the Wnt, Shh, TGF-β and Notch signaling pathways may be involved in hair follicle development and the identified DEGs may play important roles in these signaling pathways. These results will expand our understanding of the complex molecular mechanisms of hair follicle development and cycling in cashmere goats and provide a foundation for future studies. © 2013 Geng et al.

Li S.,Northwest University, China | Li S.,Rutgers University | Huang K.,Rutgers University | Zhang J.,Northwest University, China | And 2 more authors.
Organic Letters | Year: 2013

The highly linear-selective hydroaminomethylation of styrenes is very challenging. Herein, an efficient, highly chemoselective, and linear-selective hydroaminomethylation (l/b up to >99:1) of styrenes using Rh(nbd) 2SbF6 with a pyrrole-based 3,3′,5,5′- substituted tetraphosphorus ligand is documented. This is in sharp contrast to other available processes leading to branched amines and provides a novel atom economic approach to 3-arylpropylamines. © 2013 American Chemical Society.

Ou Q.,China University of Geosciences | Shu D.,China University of Geosciences | Shu D.,Northwest University, China | Mayer G.,University of Leipzig
Nature Communications | Year: 2012

Cambrian lobopodians are important for understanding the evolution of arthropods, but despite their soft-bodied preservation, the organization of the cephalic region remains obscure. Here we describe new material of the early Cambrian lobopodian Onychodictyon ferox from southern China, which reveals hitherto unknown head structures. These include a proboscis with a terminal mouth, an anterior arcuate sclerite, a pair of ocellus-like eyes and branched, antenniform appendages associated with this ocular segment. These findings, combined with a comparison with other lobopodians, suggest that the head of the last common ancestor of fossil lobopodians and extant panarthropods comprized a single ocular segment with a proboscis and terminal mouth. The lack of specialized mouthparts in O. ferox and the involvement of non-homologous mouthparts in onychophorans, tardigrades and arthropods argue against a common origin of definitive mouth openings among panarthropods, whereas the embryonic stomodaeum might well be homologous at least in Onychophora and Arthropoda. © 2012 Macmillan Publishers Limited.

Yang Q.-Y.,China University of Geosciences | Santosh M.,China University of Geosciences | Santosh M.,Northwest University, China | Tsunogae T.,University of Tsukuba | Tsunogae T.,University of Johannesburg
Precambrian Research | Year: 2014

The assembly of crustal blocks within the North China Craton (NCC) at the terminal stage of craton building during Paleoproterozoic witnessed major subduction-collision events. Here we illustrate a case where hot and anhydrous magmas emplaced in the lower crust during the early Paleoproterozoic subduction realm in the NCC led to the formation of orthopyroxene-bearing dehydrated zones of incipient charnockites within the adjacent TTG (tonalite-trondhjemite-granodiorite) suite. The coarse greenish anhydrous zones of incipient charnockite show an assemblage of antiperthitic plagioclase+orthopyroxene+K-feldspar+quartz with minor clinopyroxene, ilmenite+magnetite and secondary biotite. The peak P-T conditions of the incipient charnockite are estimated as 890-970°C and 3.5-6.5kbar based on mineral chemical analysis and pseudosection modeling in the system NCKFMASHTO, suggesting ultra-high temperature metasomatism, and the 'hottest incipient charnockites' so far reported. Zircons from the massive charnockite show oscillatory-zoned magmatic cores with high Th/U values rimmed by unzoned and luminescent thin metamorphic overgrowths. A concordant group of magmatic zircons yields weighted mean 207Pb/206Pb age of 2401±29Ma, and a lower intercept age of ca. 1834±81Ma. A similar concordant group of zircons from the TTG yields a weighted mean 207Pb/206Pb age of 2446±18Ma and a weighted mean lower intercept age of 1834±47Ma. The ca. 2.45Ga age from the TTG and 2.40 age from the charnockite are taken to represent the magma emplacement ages, and the identical 1.83Ga from zircons in both rocks denoting the timing of late Paleoproterozoic metamorphism. Lu-Hf analysis of magmatic cores of the zircons from the charnockite and the TTG show clear positive e{open}Hf(t) values (1.2-5.9), suggesting juvenile sources.The formation of incipient charnockite zones close to the contact with the charnockite pluton is consistent with the quantitative numerical models that predict CO2 migration in anhydrous silicate melt and metasomatic fluid from a rapidly cooling pluton. The ultra-high temperature metasomatism and solid-state reaction generating the incipient charnockites provide important insights on CO2 advection from lower crustal magmas during Paleoproterozoic orogeny in the North China Craton. © 2014 Elsevier B.V.

Mao Y.,Northwest University, China | Li Q.,Northwest University, China | Wang W.,Gansu Key Laboratory of Crop Improvement and Germplasm Enhancement | Liang P.,Northwest University, China | Tao S.,Northwest University, China
Genome Biology and Evolution | Year: 2013

Various regulatory elements in messenger RNAs (mRNAs) carrying the secondary structure play important roles in a wide range of expression processes. Numerous recent works have focused on the discovery of these functional elements that contain the conserved mRNA structures. However, to date, regions with high structural stability have been largely overlooked. In this study, we defined high stability regions (HSRs) in the coding sequences (CDSs) in bacteria based on the normalized folding free energy. We found that CDSs had high number of HSRs, and these HSRs showed high structural context robustness compared with random sequences, indicating a direct selective constraint imposed on HSRs. A reduced ribosome speed was detected near the start position of HSR, implying a possibility that HSR acted as obstacle to drive translational pausing that coordinated protein synthesis. Interestingly, we found that genes with high HSR density were enriched in the processes of translation, protein folding, and cell division. In addition, essential genes exhibited higher HSR density than nonessential genes. Overall, our study presented the previously unappreciated correlation between the number variation of HSRs and cellular processes. © The Author(s) 2013.

Zhang Z.,University of Florida | Zhang Z.,Northwest University, China | Huber D.J.,University of Florida | Rao J.,Northwest University, China
Postharvest Biology and Technology | Year: 2013

Preclimacteric avocado (Persea americana Mill. cv. Booth 7) fruit were treated with aqueous 1-methylcyclopropene (1-MCP) at 0.93 and 9.3mmolm-3 and then stored at 20°C to investigate the effect of 1-MCP on antioxidant systems of mesocarp tissue during ripening. Exposure to 1-MCP concentrations significantly delayed softening and peak ethylene production. 1-MCP significantly delayed accumulation of total soluble phenolics, flavonoids, and total antioxidant capacity although levels eventually reached control fruit maxima. The influence of 1-MCP was more pronounced at the higher concentration. Activities of peroxidase [POD (EC], superoxide dismutase [SOD (EC], catalase [CAT (] and l-ascorbate peroxidase [APX (EC] increased during early ripening of control fruit followed by slight (CAT) or significant (POD, APX) declines with further ripening. Increases in activities of all enzymes were delayed in proportion to 1-MCP concentration, and maximum activities attained during ripening were largely unaffected by 1-MCP. Postclimacteric declines in POD and APX were not observed at the higher 1-MCP concentration, possibly reflecting incomplete ripening. The results indicate that changes in antioxidant parameters of avocado fruit are not markedly influenced by 1-MCP but are delayed or altered in proportion to the general suppression of ripening as indicated by ethylene production and fruit softening trends. Together with previously published reports, the data also indicate that the effects of ethylene-action suppression on antioxidant parameters during ripening vary considerably among different fruits. Relationships between antioxidant systems, ethylene and ripening are discussed. © 2012 Elsevier B.V.

Bai X.-L.,Northwest University, China | Yue T.-L.,Northwest University, China | Yuan Y.-H.,Northwest University, China | Zhang H.-W.,Zhejiang University of Technology
Journal of Separation Science | Year: 2010

A simple and efficient microwave-assisted extraction of polyphenols from industrial apple pomace was developed and optimized by the maximization of the yield using response surface methodology. A Box-Behnken design was used to monitor the effect of microwave power, extraction time, ethanol concentration and ratio of solvent to raw material (g/mL) on the polyphenols yield. The results showed that the optimal conditions were as follows: microwave power 650.4 W, extraction time 53.7 s, ethanol concentration 62.1% and ratio of solvent to raw material 22.9:1. Validation tests indicated that the actual yield of polyphenols was 62.68±0.35 mg gallic acid equivalents per 100 g dry apple pomace with RSD=0.86% (n=5) under the optimal conditions, which was in good agreement with the predicted yield and higher than those of reflux and ultrasonic-assisted extraction methods. HPLC analysis indicated that the major polyphenols of apple pomace consisted of chlorogenic acid, caffeic acid, syrigin, procyanidin B2, (-)-epicatechin, cinnamic acid, coumaric acid, phlorizin and quercetin, of which procyanidin B2 had the highest content of 219.4 mg/kg. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang G.,Northwest University, China | Bai J.,Northwest University, China | Wang Y.,Northwest University, China | Ren Z.,Northwest University, China | Bai J.,École Centrale Paris
Scripta Materialia | Year: 2011

A nanocomposite of CeO2-graphene was prepared by a simple hydrothermal method and its electrochemical properties were investigated as a possible anode material for lithium ion batteries. Morphological characterization revealed that quasi-spherical CeO2 particles with a size of ∼100 nm were dispersed randomly on the graphene matrix. The nanocomposite shows a greater capacity for reversal and a better performance rate than a bare CeO2 electrode. The better electrochemical performance could be attributed to the unique structure of the nanocomposite, which combines the conductive graphene network with dispersed CeO2 particles. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Wei X.,Northwest University, China | Shao M.,Northwest University, China | Gale W.J.,Northwest University, China | Zhang X.,Northwest University, China | Li L.,Beijing Museum of Natural History
Soil Biology and Biochemistry | Year: 2013

The conversion of natural forest to cropland generally results in the loss of soil organic carbon (OC) and an increase in CO2 flux to the atmosphere. The dynamics of aggregate-associated OC after conversion to cropland are still not well understood. Such an understanding is essential for accurately estimating C flux between soil and the atmosphere. To learn more about OC dynamics after cultivation of natural forest land, we measured total soil and aggregate-associated OC in paired forest and cropland plots in Shaanxi Province, China. The cropland had been converted from adjacent forest 4, 50, and 100 yrs previously. As expected, the conversion to cropland resulted in significant declines in total soil OC concentrations and stocks. The largest decreases occurred during the early stages of cultivation. A century of cultivation decreased total soil OC stocks in the 0-20 cm depth by 0.77 kg m-2. Macroaggregate-associated OC stocks decreased, but microaggregate-associated OC stocks increased following the conversion of forest to cropland. Silt + clay-associated OC stocks were not affected. The reduction in macroaggregate-associated OC stocks was caused by declines in both the amount of soil in the macroaggregate fraction and by decreases in the concentration of macroaggregate-associated OC. The results of this study indicate the conversion of forest to cropland not only reduced total soil OC stocks, but also caused a percentage shift in the distribution of total soil OC among aggregate size classes and among soil depths. These shifts would delay the loss of OC, so the loss of OC in forest soil due to cultivation might thus be lower than expected. © 2012 Elsevier Ltd.

Ma S.,Northwest University, China | Wang H.,Northwest University, China | Wang Y.,Northwest University, China | Bu H.,Northwest University, China | Bai J.,École Centrale Paris
Renewable Energy | Year: 2011

One-factor-at-a-time design and orthogonal design were used in the experimental design methods to optimize bio-hydrogen (bio-H2) production from cornstalk wastes by anaerobic fermentation. Three series of experiments were designed to investigate the effects of substrate concentration, initial pH and orthogonal design on the bio-H2 production by using the natural sludge as inoculant. Experimental results indicate that substrate concentration was the most significant condition for optimal hydrogen production. The optimum orthogonal design method was proposed to be at an enzymatic temperature of 50 °C, an enzymatic time of 72 h, an initial pH of 7.0 and a substrate concentration of 10 g/L. The proposed method facilitated the optimization of optimum design parameters, only with a few well-defined experimental sets. Under the proposed condition, the maximum cumulative H2 yield was 141.29 ml g-1-CS (cornstalk, or 164.48 ml g-1-TS, total solid, TS = 0.859 Wdried cornstalk), with an average H2 production rate of 12.31 ml g-1-CS h-1. The hydrogen content reached 57.85% and methane was not detected in the biogas. © 2010 Elsevier Ltd.

Bai X.,Northwest University, China | Zhang H.,Zhejiang University of Technology | Ren S.,Northwest University, China
Journal of the Science of Food and Agriculture | Year: 2013

BACKGROUND: Phenolic compounds are the predominant ingredients in apple pomace. However, polyphenols from industrial apple pomace, which usually consists of several cultivars, have not been studied in detail. The present work focused on the antioxidant assay and HPLC analysis of polyphenol-enriched extracts from industrial apple pomace. RESULTS: Six fractions of apple polyphenols, API to APVI, were acquired through extraction and purification using absorbent macroporous resin. Fraction APIII, eluted by 40% aqueous ethanol, had the highest content of total phenolics (1.48±0.03 g gallic acid equivalents g-1 dry apple pomace), which consisted of chlorogenic acid, caffeic acid, syrigin, procyanidin B2, (-)-epicatechin, cinnamic acid, coumaric acid and quercetin. Antioxidant assays showed that APIII had the strongest antioxidant activity of DPPH radical scavenging rate (90.96%±10.23%), ABTS radical inhibition rate (89.78%±6.54%) and the strongest reducing power (8.30±0.71 μmol Trolox equivalents kg-1 dry apple pomace). It also indicated that procyanidin B2, chlorogenic acid, (-)-epicatechin and quercetin had stronger antioxidant capacity than other phenols. CONCLUSION: Our data suggested that extracts from industrial apple pomace were rich in phenols and exhibited potent antioxidant activity. Extraction of polyphenols from industrial apple pomace would bring a great benefit and improve development of apple juice and cider industries. © 2013 Society of Chemical Industry.

Wang B.,Northwest University, China | Wang G.,Northwest University, China | Zheng Z.,Northwest University, China | Wang H.,Northwest University, China | And 2 more authors.
Electrochimica Acta | Year: 2013

A hybrid material of carbon coated Fe3O4 (Fe 3O4@C) is synthesized by chemical vapor deposition method using Fe2O3 as starting material and acetylene as carbon source. The obtained material is Fe3O4 spheres of ∼400 nm coated by thin carbon layer with a thickness of ∼10 nm. As an anode material for lithium ion batteries, Fe3O4@C shows an improved electrochemical performance in the reversible capacity and cycling stability, together with excellent rate capability. The performance is much better than the results obtained from bare Fe2O3 and commercial Fe3O4 of the same size. In addition to the comparison of electrochemical impedance spectra of the Fe2O 3, Fe3O4 and Fe3O4@C electrodes before and after 50 charge/discharge cycles, a surface contrast of the three electrodes before and after cycling is systematically investigated to explore the influence of carbon layer on the electrochemical performance of the Fe3O4 spheres. © 2013 Elsevier Ltd. All rights reserved.

Du J.,Northwest University, China | Yuan Z.,Northwest University, China | Ma Z.,Northwest University, China | Song J.,University of Maryland University College | And 2 more authors.
Molecular BioSystems | Year: 2014

The dynamic impact approach (DIA) represents an alternative to overrepresentation analysis (ORA) for functional analysis of time-course experiments or those involving multiple treatments. The DIA can be used to estimate the biological impact of the differentially expressed genes (DEGs) associated with particular biological functions, for example, as represented by the Kyoto encyclopedia of genes and genomes (KEGG) annotations. However, the DIA does not take into account the correlated dependence structure of the KEGG pathway hierarchy. We have developed herein a path analysis model (KEGG-PATH) to subdivide the total effect of each KEGG pathway into the direct effect and indirect effect by taking into account not only each KEGG pathway itself, but also the correlation with its related pathways. In addition, this work also attempts to preliminarily estimate the impact direction of each KEGG pathway by a gradient analysis method from principal component analysis (PCA). As a result, the advantage of the KEGG-PATH model is demonstrated through the functional analysis of the bovine mammary transcriptome during lactation. © 2014 the Partner Organisations.

Huang C.,Northwest University, China | Zheng C.,Northwest University, China | Li Y.,Dalian University of Technology | Wang Y.,Northwest University, China | And 2 more authors.
Briefings in Bioinformatics | Year: 2013

Systems pharmacology is an emerging field that integrates systems biology and pharmacology to advance the process of drug discovery, development and the understanding of therapeutic mechanisms. The aim of the present work is to highlight the role that the systems pharmacology plays across the traditional herbal medicines discipline, which is exemplified by a case study of botanical drugs applied in the treatment of depression. First, based on critically examined pharmacology and clinical knowledge, we propose a large-scale statistical analysis to evaluate the efficiency of herbs used in traditional medicines. Second, we focus on the exploration of the active ingredients and targets by carrying out complex structure-, omics- and network-based systematic investigations. Third, specific informatics methods are developed to infer drug- disease connections, with purpose to understand how drugs work on the specific targets and pathways. Finally, we propose a new systems pharmacology method, which is further applied to an integrated platform (Herbal medicine Systems Pharmacology) of blended herbal medicine and omics data sets, allowing for the systematization of current and traditional knowledge of herbal medicines and, importantly, for the application of this emerging body of knowledge to the development of new drugs for complex human diseases. © The Author 2013.

Yuan J.-K.,École Centrale Paris | Li W.-L.,École Centrale Paris | Li W.-L.,Northwest University, China | Yao S.-H.,Joseph Fourier University | And 3 more authors.
Applied Physics Letters | Year: 2011

Vertically aligned carbon nanotubes (CNTs) were synthesized on SiC microplates. Resultant SiC-CNTs hybrids were further incorporated into poly(vinylidene fluoride) (PVDF) as conductive filler to prepare percolative composites. They exhibited a much low percolation threshold (1.47 vol %), but the dielectric permittivity was enhanced significantly. The largest dielectric permittivity of 8700 was observed in the SiC-CNTs/PVDF composites with 2.3 vol % CNTs at 100 Hz. A microcapacitor model was proposed to explain the obtained results based on the special geometry of the hybrid SiC-CNTs filler. © 2011 American Institute of Physics.

Tian N.,Northwest University, China | Wang J.,Ankang University | Xu Z.Q.,Northwest University, China
South African Journal of Botany | Year: 2011

Salinity is the main limiting factor of plant growth and agricultural productivity. A lot of previous works showed that the introduction of Na+/H+ antiporter gene could improve the tolerance of plants to salt. In this study, a vacuolar Na+/H+ antiporter gene, AtNHX1 from Arobidopsis, was transferred into kiwifruit by Agrobacterium-mediated protocol. Polymerase chain reaction (PCR) and Southern blot analysis confirmed that AtNHX1 was successfully integrated into the kiwifruit genome. Reverse transcription (RT)-PCR analysis indicated that AtNHX1 expressed highly in transgenic plants. It was found that transgenic kiwifruit plants exhibited improved resistance to 200mmol/l NaCl in comparison with wide-type plants. Under salt stress, these transgenic lines accumulated more Na+ than control, due to an increased Na+/H+ antiporter activity. In physiological analysis, the traits such as osmotic adjustment and antioxidation capability of transgenic lines under salt stress were obviously higher than that of wide-type plants. These results suggested that the overexpression of vacuolar Na+/H+ antiporter gene could increase the salt tolerance of kiwifruit. © 2010 SAAB.

Wang G.,Northwest University, China | Wang H.,Northwest University, China | Cai S.,Northwest University, China | Bai J.,Northwest University, China | And 2 more authors.
Journal of Power Sources | Year: 2013

A hybrid material of carbon-coated Fe2O3 submicro-particles loaded on graphene nanosheets (Fe2O 3@C/GNs) is prepared by a two step route including a hydrothermal and a subsequent glucose impregnation-pyrolysis process. The obtained material is composed of GNs and ∼400 nm size Fe2O3 particles coated by thin carbon layer with a thickness of 5 nm. As an anode material for lithium ion batteries, Fe2O3@C/GNs hybrid shows an improved electrochemical performance in the initial coulombic efficiency (71%), reversible capacity (900 mA h g-1 after 50 cycles at a current of 200 mA g-1) and capacity retention rate (82% after 50 cycles). This result is much better than the synthesized bare Fe2O3 and Fe2O3/GNs electrodes. In addition to the contribution of GNs, the carbon-coated layer around Fe2O3 particles is believed to be a key factor to improve the electrochemical performance of Fe2O3. © 2013 Elsevier B.V. All rights reserved.

Chen D.,Northwest University, China | Chen D.,Arizona State University | Wu C.,University of Waterloo | Iu H.H.C.,University of Western Australia | Ma X.,Northwest University, China
Nonlinear Dynamics | Year: 2013

We design a new three-dimensional double-wing fractional-order chaotic system with three quadratic terms, confirmed by numerical simulation and circuit implementation. We then study the synchronization between the new double-wing fractional-order chaotic system and different Lorenz systems with different structures. In the process of the synchronization, the definition of 'the simplest response system' and the practical method of designing the circuit have been originally proposed. The circuit of 'the simplest response system' (even the simplest incommensurate-order response system), holding different structures with the drive system, of any one integral or fractional drive system now can be designed effectively and sufficiently. Our results are supported by numerical simulation and circuit implementation. © 2013 Springer Science+Business Media Dordrecht.

Wei X.,Northwest University, China | Shao M.,Northwest University, China | Gale W.,Shihezi University | Li L.,Beijing Museum of Natural History
Scientific Reports | Year: 2014

Several reviews have analyzed the factors that affect the change in soil organic C (SOC) when forest is converted to agricultural land; however, the effects of forest type and cultivation stage on these changes have generally been overlooked. We collated observations from 453 paired or chronosequential sites where forests have been converted to agricultural land and then assessed the effects of forest type, cultivation stage, climate factors, and soil properties on the change in the SOC stock and the SOC turnover rate constant (k). The percent decrease in SOC stocks and the turnover rate constants both varied significantly according to forest type and cultivation stage. The largest decrease in SOC stocks was observed in temperate regions (52% decrease), followed by tropical regions (41% decrease) and boreal regions (31% decrease). Climate and soil factors affected the decrease in SOC stocks. The SOC turnover rate constant after the conversion of forests to agricultural land increased with the mean annual precipitation and temperature. To our knowledge, this is the first time that original forest type was considered when evaluating changes in SOC after being converted to agricultural land. The differences between forest types should be considered when calculating global changes in SOC stocks.

Ming Z.,Inner Mongolia University of Science and Technology | Yu S.,Inner Mongolia University of Science and Technology | Sheng T.C.,Northwest University, China
Journal of the European Ceramic Society | Year: 2011

Grain growth of 2wt% V2O5/Sb2O3 precursor doped ZnO-V2O5 based ceramics was studied for sintering from 900 to 1050°C. The results are discussed and compared with those of the conventional Sb2O3 doped ZnO-V2O5 based ones of the same stoichiometric ratio in terms of the phenomenological grain growth kinetics equation: Gn-G0n=K0t exp(-Q/RT). Grain growth exponent and apparent activation energy of the precursor doped ceramics are found to be 2.44 and about 218kJ/mol, respectively, much lower than 4.03 and about 365kJ/mol for the Sb2O3 doped samples. This result and the XRPD examination of the phase transformation within two extra batches of the precursor or the Sb2O3 slightly over-doped samples sintered at 550-900°C for 1h indicate the elimination of Sb2O3 related films contributes mainly to the observed noteworthy low temperature sintering (900°C) of the precursor doped ZnO-V2O5 ceramics. © 2011 Elsevier Ltd.

Li Z.,Northwest University, China | Zheng F.-L.,Northwest University, China | Liu W.-Z.,CAS Institute of Soil and Water Conservation | Flanagan D.C.,U.S. Department of Agriculture
Quaternary International | Year: 2010

Extreme climate events often cause catastrophic damage to nature and human society. Therefore, regional assessments in various climates and geographic regions are needed for understanding the uncertainties of the change trends for extreme climate events. The objective of this study was to assess the spatial distribution and temporal trends of extreme precipitation and temperature events on the Loess Plateau of China during 1961-2007. Nine indicators (pq90, px5d, pint, pxcdd, pnl9, txq90, tnq10, tnfd, txhw90) were chosen to quantify extreme climate events, the Mann-Kendall method and linear trend analysis were used to test the change in trend and the magnitude, and inverse distance weighted interpolation was used to interpolate the spatial patterns. Results showed that most extreme climate indicators were spatially distributed with obvious gradients from the southeast to the northwest. Heavy rainfall threshold (pq90), greatest 5-day total rainfall (px5d), heavy rainfall days (pnl9) and cold-night threshold (tnq10) decreased from the southeast to the northwest, while simple daily rainfall intensity (pint), longest dry period (pxcdd) and number of frost days (tnfd) increased from the southeast to the northwest. Most stations had monotonic trends in extreme indicators during 1961-2007. However, the number of stations with significant trends varied greatly. Precipitation-based indicators showed more mixed patterns of change and few stations had significant trends. However, temperature-based indicators had more uniform changes and most stations had significant trends. Hot-day threshold (txq90) and cold-night threshold (tnq10), and the longest heatwave (txhw90) tended to increase while the number of frost days decreased since the 1960s on the Loess Plateau. Overall, extreme precipitation events did not change significantly; however, extreme temperature events became more severe and frequent. The results implied that extreme climate events on the Loess Plateau will continue to have adverse impacts, and adaptive measures should be considered for future ecological construction and agriculturally sustainable development. © 2010 Elsevier Ltd and INQUA.

Stewart C.E.,U.S. Department of Agriculture | Stewart C.E.,Colorado State University | Zheng J.,Northwest University, China | Botte J.,Colorado State University | Cotrufo M.F.,Colorado State University
GCB Bioenergy | Year: 2013

Char is a product of thermochemical conversion of biomass via pyrolysis, together with gas (syngas), liquid (bio-oil), and heat. Fast pyrolysis is a promising process for bio-oil generation, which leaves 10-30% of the original biomass as char. Char produced for soil application, is defined biochar (BC), and it may increase soil C storage, and reduce soil emissions of greenhouse gases (GHG), such as N2O and CH4 -potentially making fast pyrolysis bioenergy generation a C-negative system. However, differences in production conditions (e.g., feedstock, pyrolysis temperature and speed, post handling, and storage conditions) influence the chemical properties of BC and its net effect when added to soils. Understanding if fast pyrolysis BC can increase C sequestration and reduce GHG emissions will enable full assessment of the economic value and environmental benefits of this form of bioenergy. We characterized a BC produced by fast pyrolysis for bio-oil generation and examined GHG (CO2, N2O and CH4) efflux, C partitioning using δ13C, and soil C sequestration across four temperate soils and five BC rates; 0%, 1%, 5%, 10%, and 20% w/w. The fast pyrolysis process created a highly aromatic, low N, ash-rich BC with a O: C ratio of 0.01, which we expected to be highly recalcitrant. Across soils, CO2 emissions increased linearly and N2O emissions decreased exponentially with increasing BC addition rates. Despite still being actively respired after 2 years, total BC-derived C-CO2 comprised less than the BC volatile C content (4%). Expressed as CO2 equivalents, CO2 was the primary GHG emitted (97.5%), followed by N2O. All GHG emissions were small compared to the total SOC sequestered in the BC. Fast pyrolysis produced a highly recalcitrant BC that sequestered C and reduced GHG emissions. The recovery and soil application of BC would contribute to a negative carbon balance for this form of bioenergy generation. © 2012 Blackwell Publishing Ltd.

Li Z.,Northwest University, China | Liu W.-Z.,CAS Institute of Soil and Water Conservation | Zhang X.-C.,U.S. Department of Agriculture | Zheng F.-L.,CAS Institute of Soil and Water Conservation
Climatic Change | Year: 2011

Climate changes may have great impacts on the fragile agro-ecosystems of the Loess Plateau of China, which is one of the most severely eroded regions in the world. We assessed the site-specific impacts of climate change during 2010-2039 on hydrology, soil loss and crop yields in Changwu tableland region in the Loess Plateau of China. Projections of four climate models (CCSR/NIES, CGCM2, CSIRO-Mk2 and HadCM3) under three emission scenarios (A2, B2 and GGa) were used. A simple spatiotemporal statistical method was used to downscale GCMs monthly grid outputs to station daily weather series. The WEPP (Water and Erosion Prediction Project) model was employed to simulate the responses of agro-ecosystems. Compared with the present climate, GCMs projected a -2.6 to 17.4% change for precipitation, 0.6 to 2.6°C and 0.6 to 1.7°C rises for maximum and minimum temperature, respectively. Under conventional tillage, WEPP predicted a change of 10 to 130% for runoff, -5 to 195% for soil loss, -17 to 25% for wheat yield, -2 to 39% for maize yield, -14 to 18% for plant transpiration, -8 to 13% for soil evaporation, and -6 to 9% for soil water reserve at two slopes during 2010-2039. However, compared with conventional tillage under the present climate, conservation tillage would change runoff by -34 to 71%, and decrease soil loss by 26 to 77% during 2010-2039, with other output variables being affected slightly. Overall, climate change would have significant impacts on agro-ecosystems, and adoption of conservation tillage has great potential to reduce the adverse effects of future climate changes on runoff and soil loss in this region. © 2010 Springer Science+Business Media B.V.

He X.,Xi'an Jiaotong University | Song Z.,Northwest University, China
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

In this paper, a new mathematical equation of lg(F0 F)/F = 1/nlg[P] + 1/nlgKa, which was used to obtain interaction parameters (the binding constant Ka and the number of binding sites n) between the protein and the small molecule ligand by using the ligand as a fluorescence (FL) probe, was constructed for the first time. The interaction parameters between myoglobin, catalase, lysozyme, bovine serum albumin (BSA) and luminol were obtained by this equation with luminol used as a FL probe, showing that the binding constants Ka were 8.78 × 105, 4.47 × 105, 4.21 ×104 and 3.95 × 104 respectively, and the number of binding sites n approximately equaled to 1.0 for myoglobin, catalase, and 2.0 for lysozyme, BSA. The interactions of ferritin, ovalbumin, aldolase, chymotrypsinogen and ribonuclease with luminol were also studied by this method. The binding constants Ka were at 10 4-105 level, and the number of binding sites n mostly approximately equaled to 2.0. The binding ability of luminol to the studied proteins followed the pattern: myoglobin > aldolase > ferritin > ovalbumin > catalase > ribonuclease > lysozyme > BSA > chymotrypsinoge. © 2013 Elsevier B.V. All rights reserved.

Su H.,PLA Air Force Aviation University | Xu J.,PLA Air Force Aviation University | Xu J.,Northwest University, China | Ren W.,PLA Air Force Aviation University
Materials and Design | Year: 2014

The research herein is made on the quasi-static and dynamic mechanical properties of ceramic fiber reinforced concrete (CRFRC for short) through the adoption of a hydraulically-driven testing system as well as a 100-mm-diameter split Hopkinson pressure bar (SHPB) system. As test results have turned out, such quasi-static properties as compressive strength, splitting tensile strength and flexural strength of CRFRC increase with the rise in the volume fraction of fiber. Within the strain range of 20-120s-1, the effect of the axial strain acceleration on the dynamic strength of CRFRC could be ignored. Therefore, the dynamic increase ratio (DIF) derived from SHPB tests can truly reflect the dynamic enhancement of CRFRC. The dynamic strength, critical strain and specific energy absorption (SEA) of CRFRC are sensitive to the strain rate. The addition of ceramic fiber to plain concrete can significantly improve its properties-dynamic strength, critical strain and energy absorption. And also, an analysis is conducted of the mechanism for strengthening and toughening the concrete. © 2014 Elsevier Ltd.

Zhang J.,Northwest University, China | Siika-Aho M.,VTT Technical Research Center of Finland | Tenkanen M.,University of Helsinki | Viikari L.,University of Helsinki
Biotechnology for Biofuels | Year: 2011

Background: Due to the complexity of lignocellulosic materials, a complete enzymatic hydrolysis into fermentable sugars requires a variety of cellulolytic and xylanolytic enzymes. Addition of xylanases has been shown to significantly improve the performance of cellulases and to increase cellulose hydrolysis by solubilizing xylans in lignocellulosic materials. The goal of this work was to investigate the effect of acetyl xylan esterase (AXE) originating from Trichoderma reesei on xylan solubilization and enzymatic hydrolysis of cellulose. Results: The solubilization of xylan in pretreated wheat straw and giant reed (Arundo donax) by xylanolytic enzymes and the impact of the sequential or simultaneous solubilization of xylan on the hydrolysis of cellulose by purified enzymes were investigated. The results showed that the removal of acetyl groups in xylan by AXE increased the accessibility of xylan to xylanase and improved the hydrolysis of xylan in pretreated wheat straw and giant reed. Solubilization of xylan led to an increased accessibility of cellulose to cellulases and thereby increased the hydrolysis extent of cellulose. A clear synergistic effect between cellulases and xylanolytic enzymes was observed. The highest hydrolysis yield of cellulose was obtained with a simultaneous use of cellulases, xylanase and AXE, indicating the presence of acetylated xylan within the cellulose matrix. Acetylated xylobiose and acetylated xylotriose were produced from xylan without AXE, as confirmed by atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry. Conclusions: The results in this paper demonstrate that supplementation of xylanase with AXE enhances the solubilization of xylan to some extent and, consequently, increases the subsequent hydrolysis of cellulose. The highest hydrolysis yield was, however, obtained by simultaneous hydrolysis of xylan and cellulose, indicating a layered structure of cellulose and xylan chains in the cell wall substrate. AXE has an important role in the hydrolysis of lignocellulosic materials containing acetylated xylan. © 2011 Zhang et al; licensee BioMed Central Ltd.

Chen D.,Northwest University, China | Song Z.,Northwest University, China | Lv H.,Northwest University, China | Lv H.,Xi'an Jiaotong University
Food Chemistry | Year: 2012

A sensitive flow injection-chemiluminescence (FI-CL) method for the determination of isocarbophos (ICP) residue on tangerines and oranges was proposed. It was found that the CL intensity from luminol-albumin CL reaction could be obviously quenched in the presence of ICP and the decrease in CL intensity was proportional to the logarithm of ICP concentrations ranging from 1.0 to 1000 pmol L-1, giving the limit of detection of 0.3 pmol L-1 (3σ). The proposed procedure was successfully applied to the determination of ICP residue on tangerines and oranges with recoveries varying from 92.0 to 111.0% and RSDs less than 5.0%. The possible CL mechanism of luminol-albumin-ICP reaction was discussed, and ICP to albumin's binding constant (KD = 1.00 × 106 L mol-1) and the number of binding sites (n = 1.00) were given by the homemade FI-CL model. © 2012 Elsevier Ltd. All rights reserved.

Zhu H.,Northwest University, China | Huang Z.,Northwest University, China | Wang S.,Northwest University, China | Wang S.,Washington State University
Journal of Electromagnetic Waves and Applications | Year: 2014

Top electrode voltage of a radio frequency (RF) heating system is an important parameter to accurately determine final sample temperatures using computer simulation. The purpose of this study was to establish the correlation between the top electrode voltage obtained by analytical method or simulation and the measured electrical currents. A measuring circuit was designed and developed to directly measure the top electrode voltage in the 27 MHz 6 kW RF unit together with the anode current read from the RF generator. The top electrode voltage was experimentally determined with 3 kg soybeans under five electrode gaps using computer simulation based on the matched temperature profiles in three layers, and analytical methods based on the heating rates measured by infrared camera, fiber optic sensors and thermocouples. Results showed that the electrode voltage decreased with increasing electrode gap or decreasing heating rate. The correlation between the electrode voltage estimated by temperature distributions from three-layer thermal imaging and the electrical currents both from the anode reading and direct measurement was the best one among the estimation methods and could be used for future computer simulations. © 2014 Taylor & Francis.

Xu Z.,Xi'an Jiaotong University | Chang X.,Xi'an Jiaotong University | Xu F.,Xi'an Jiaotong University | Zhang H.,Northwest University, China
IEEE Transactions on Neural Networks and Learning Systems | Year: 2012

The special importance of L1/2 regularization has been recognized in recent studies on sparse modeling (particularly on compressed sensing). The L1/2 regularization, however, leads to a nonconvex, nonsmooth, and non-Lipschitz optimization problem that is difficult to solve fast and efficiently. In this paper, through developing a threshoding representation theory for L1/2 regularization, we propose an iterative half thresholding algorithm for fast solution of L1/2 regularization, corresponding to the well-known iterative soft thresholding algorithm for L1 regularization, and the iterative hard thresholding algorithm for L0 regularization. We prove the existence of the resolvent of gradient of ||x||1/2 1/2, calculate its analytic expression, and establish an alternative feature theorem on solutions of L1/2 regularization, based on which a thresholding representation of solutions of L1/2 regularization is derived and an optimal regularization parameter setting rule is formulated. The developed theory provides a successful practice of extension of the well-known Moreau's proximity forward-backward splitting theory to the L1/2 regularization case. We verify the convergence of the iterative half thresholding algorithm and provide a series of experiments to assess performance of the algorithm. The experiments show that the half algorithm is effective, efficient, and can be accepted as a fast solver for L1/2 regularization. With the new algorithm, we conduct a phase diagram study to further demonstrate the superiority of L1/2 regularization over L1 regularization. © 2012 IEEE.

Xu X.-M.,Northwest University, China | Xu X.-M.,East Malling Research | Jeger M.J.,Imperial College London
Phytopathology | Year: 2013

Effective use of biocontrol agents (BCAs) is a potentially important component of sustainable agriculture; recently, there has been a trend for combined use of several BCAs, with an expectation of synergistic interactions among them. A previous numerical study suggested that, under homogenous conditions in which two BCAs occupied the same host tissue as the pathogen, combined use of two BCAs with different biocontrol mechanisms resulted, in most cases, in efficacies similar to using the more efficacious one alone; this result is consistent with published experimental results. The present study investigates whether combined use of a mycoparasitic and a competitive BCA leads to greater efficacy than that expected when the model is modified to allow for fluctuating temperature regimes and the effects of temperature on the pathogen and BCAs. Within the range of parameter values considered, combined use of two BCAs is shown to be less effective than that expected under the assumption of Bliss independence, and to result in a level of efficacy similar to that achieved by the more efficacious component used alone, indicating antagonistic interactions between the two BCAs. Nevertheless, combined use of two BCAs resulted in a slightly longer delay in epidemic development than did individual use of BCAs. Stochastic variability in simulated hourly temperatures did not result in a high level of variability in efficacy among replicates; nevertheless, the among-replicate variability appeared to be greater for the combined use of BCAs than for individual BCAs used alone. In contrast, there were greater effects of varying BCA-temperature relationships and application time (reflected in the temperature profile) on efficacy, suggesting the importance of characterizing the relationship between BCA activity and environmental conditions in future research. © 2013 The American Phytopathological Society.

Zhang J.,Northwest University, China | Pakarinen A.,University of Helsinki | Viikari L.,University of Helsinki
Bioresource Technology | Year: 2013

The impact of pectinases in the hydrolysis of fresh, steam-exploded and ensiled hemp was investigated and the synergy between cellulases, pectinases and xylanase in the hydrolysis was evaluated. About half; 59.3% and 46.1% of pectin in the steam-exploded and ensiled hemp, respectively, could be removed by a low dosage of pectinases used. Pectinases were more efficient than xylanase in the hydrolysis of fresh and ensiled hemp whereas xylanase showed higher hydrolytic efficiency than the pectinase preparation used in the hydrolysis of steam-exploded hemp. Clear synergistic action between cellulases and xylanase could be observed in the hydrolysis of steam-exploded hemp. Supplementation of pectinase resulted in clear synergism with cellulases in the hydrolysis of all hemp substrates. Highest hydrolysis yield of steam-exploded hemp was obtained in the hydrolysis with cellulases and xylanase. In the hydrolysis of ensiled hemp, the synergistic action between cellulases and pectinases was more obvious for efficient hydrolysis. © 2012 Elsevier Ltd.

Hou L.,Northwest University, China | Ling B.,Northwest University, China | Wang S.,Northwest University, China | Wang S.,Washington State University
Postharvest Biology and Technology | Year: 2014

Methyl bromide fumigation, widely used for disinfesting chestnuts, will be banned in developing countries by 2015 under Montreal Protocol due to its adverse effects on human health and environment. The purpose of this research was to study possible applications of radio frequency (RF) heating for disinfestations of chestnuts to replace chemical fumigation. A 6. kW, 27. MHz free-running oscillator RF system was used to determine the effect of a developed RF treatment protocol on quality of chestnuts. The results showed that the heating time needed only 5.4. min to heat the 2.5. kg chestnuts from 20 °C to 55 °C using RF energy, and 170. min for chestnuts to reach 52.5 °C using hot air at 55 °C and 1.6 m/s. Based on the heating uniformity studies, a RF treatment protocol was finally developed to combine 0.6. kW RF powers with a forced hot air at 55 °C, movement of the conveyor, mixing twice, and holding at 55. °C hot air for 5. min, followed by forced room air cooling through single-layer samples. Quality of chestnuts was not affected by the RF treatments because no significant differences in moisture, protein, fat, soluble sugar, firmness, and color were observed between RF treatments and untreated controls after 8 days at 35. °C, simulating one year of storage at 4 °C. The RF treatments may provide a rapid and environmentally friendly method to replace chemical fumigation for disinfesting chestnuts. © 2014 Elsevier B.V.

Yu R.,Northwest University, China | Zhong S.,Jiangxi Normal University | Xue N.,Northwest University, China | Li H.,Northwest University, China | Ma H.,Northwest University, China
Dalton Transactions | Year: 2014

Polycrystalline samples of Ce3+-doped NaBaBO3 (0.5-15 mol%) were prepared by the solid-phase synthesis. The phase formation was confirmed by X-ray powder diffraction (XRD) measurements and structural refinement. The photoluminescence excitation and emission spectra and decay curves were measured. The absolute luminescence quantum efficiency (QE) and the activation energy (ΔE) were reported. Under the excitation of near-UV light, Ce3+-doped NaBaBO3 presents a green-emission band centred at 505 nm from the allowed inter-configurational 4f-5d transition. The maximum absolute QE of NaBaBO3:Ce3+ was measured to be 58% excited with 395 nm light at 300 K. The thermal stability of the green luminescence was evaluated by the luminescence decays as a function of temperature. The phosphor shows an excellent thermal stability on temperature quenching effects. Compared with the reported Ce3+-doped alkali metal and alkaline earth orthoborates with the general formula MNBO3 with only blue luminescence, the peculiarity of NaBaBO3:Ce3+ is the green emission and a high doping concentration in the lattices. The results were discussed on the relationship between the structure and the luminescence properties. © 2014 the Partner Organisations.

Gomez J.D.,Colorado State University | Gomez J.D.,National Autonomous University of Mexico | Denef K.,Colorado State University | Stewart C.E.,Colorado State University | And 3 more authors.
European Journal of Soil Science | Year: 2014

Biochar (BC) amendment to soils is a proposed strategy to improve soil fertility and mitigate climate change. However, before this can become a recommended management practice, a better understanding of the impacts of BC on the soil biota is needed. We determined the effect of addition rates (0, 1, 5, 10 and 20% by mass) of a fast-pyrolysis wood-derived BC on the extraction efficiency (EE), abundance and temporal dynamics of phospholipid fatty acids (PLFAs, microbial community biomarkers) in four temperate soils during a 1-year incubation. Additionally, the effects on microbial mineralization/incorporation of BC-C were determined by measuring CO2 efflux and the BC contribution to CO2 and PLFA-C using the natural 13C abundance difference between BC and soils. Biochar addition proportionally increased microbial abundance in all soils and altered the community composition, particularly at the greatest addition rate, towards a more gram-negative bacteria-dominated (relative to fungi and gram-positive) community. Though chemically recalcitrant, the BC served as a substrate for microbial activity, more so at large addition rates and in soil with little organic matter. Microbial utilization of BC-C for growth could only partially explain the observed increase in microbial biomass, suggesting that other, potentially abiotic, mechanisms were involved. The strong decrease in PLFA EE (-77%) in all soils with biochar addition emphasizes the need to measure and correct for EE when using PLFA biomarkers to estimate soil microbial responses to BC additions. Overall, our study provides support for BC use as a soil amendment that potentially stimulates microbial activity and growth. © 2013 British Society of Soil Science.

Zhang X.-C.,U.S. Department of Agriculture | Liu W.-Z.,CAS Institute of Soil and Water Conservation | Li Z.,Northwest University, China | Chen J.,University of Québec
Agricultural and Forest Meteorology | Year: 2011

Trends and uncertainty of the climate change impacts on hydrology, soil erosion, and wheat production during 2010-2039 at El Reno in central Oklahoma, USA, were evaluated for 12 climate change scenarios projected by four GCMs (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emissions scenarios (A2, B2, and GGa). Compared with the present climate, overall t-tests (n= 12) show that it is almost certain that mean precipitation will decline by some 6% (>98.5% probability), daily precipitation variance increase by 12% (>99%), and maximum and minimum temperature increase by 1.46 and 1.26. °C (>99%), respectively. Compared with the present climate under the same tillage systems, it is very likely (>90%) that evapotranpiration and long-term soil water storage will decease, but runoff and soil loss will increase despite the projected declines in precipitation. There will be no significant changes in wheat grain yield.Paired t-tests show that daily precipitation variance projected under GGa is greater than those under A2 and B2 (P= 0.1), resulting in greater runoff and soil loss under GGa (P= 0.1). HadCM3 projected greater mean annual precipitation than CGCM2 and CSIRO (P= 0.1). Consequently, greater runoff, grain yield, transpiration, soil evaporation, and soil water storage were simulated for HadCM3 (P= 0.1). The inconsistency among GCMs and differential impact responses between emission scenarios underscore the necessity of using multi-GCMs and multi-emission scenarios for impact assessments. Overall results show that no-till and conservation tillage systems will need to be adopted for better soil and water conservation and environmental protection in the region during the next several decades. © 2011.

Pyykko P.,University of Helsinki | Xu W.-H.,University of Helsinki | Xu W.-H.,Northwest University, China
Chemistry - A European Journal | Year: 2015

It has recently been suggested that the oxidation states of Ir run from the putative -III in the synthesized solid Na3[Ir(CO)3] to the well-documented +IX in the species IrO4+. Furthermore, [Ir(CO)3]3- was identified as an 18-electron species. A closer DFT study now finds support for this picture: The orbitals spanned by the 6s,6p,5d orbitals of the iridium are all occupied. Although some have considerable ligand character, the deviations from 18 e leave the orbital symmetries unchanged. The isoelectronic systems from Os-IV to Au-I behave similarly, suggesting further possible species. To paraphrase Richard P. Feynmann "there is plenty of room at the bottom". Room at the bottom: A qualitative 18-electron structure is maintained in [Ir(CO)3]3- and beyond. A good correlation of the oxidation state with the experimental Mössbauer isomer shifts is found for IrIII-IX (see figure). A map of these numerous [M(CO)n]x species was also made. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang Y.,CAS Guangzhou Institute of Geochemistry | Wang Y.,Northwest University, China | Zhang A.,CAS Guangzhou Institute of Geochemistry | Cawood P.A.,University of St. Andrews | And 5 more authors.
Precambrian Research | Year: 2013

U-Pb geochronology along with elemental and Nd-Hf-Os isotopic data from the earliest Neoproterozoic metabasic rocks within the Cathaysia Block of the South China Block (SCB) constrain the tectonic setting and paleogeography of the block within the Rodinia supercontinent. The metabasic rocks give zircon U-Pb ages of 969-984Ma, εHf(t) values of +1.8 to +15.3 and Hf model ages of 0.92-1.44Ga. They are subalkaline basalts that can be geochemically classified into four groups. Group 1 has low Nb contents (1.24-4.33ppm), highly positive εNd(t) values (+4.3 to +5.2), and REE and multi-elemental patterns similar to fore-arc MORB-type basalt. Group 2 has Nb contents ranging from 3.13ppm to 6.48ppm, εNd(t) of +3.1 to +6.2, low Re and Os contents and high initial Os isotopic ratios, and displays an E-MORB geochemical signature. Group 3 has Nb=7.18-29.87ppm, Nb/La=0.60-1.40, Nb/U=5.0-37, Ce/Pb=1.1-6.6, εNd(t)=+2.9 to +7.0, 187Re/188Os=5.87-8.87 and γOs (t)=178-772, geochemically resembling to the Pickle Nb-enriched basalt. Group 4 has strong LREE/HREE and HREE fractionation and high εNd(t) values (+2.3 to +5.6), and is characterized by similar element patterns to arc volcanic rocks. Serpentinites coeval to Group 4 show 187Os/188Os of 0.1143-0.1442 and γOs (t) of -7.8 to +0.1. Groups 1 and 2 are interpreted to originate from the N-MORB and E-MORB-like sources with the addition of an arc-like component, genetically linked to fore- and back-arc settings, respectively. Groups 3 and 4 show inputs of newly subduction-derived melt and fluid in the wedge source. These geochronological and geochemical signatures fingerprint the development of an earliest Neoproterozoic (~970Ma) arc-back-arc system along the Wuyi-Yunkai domain of the Cathaysia Block. Regional relationships indicate that the Wuyi-Yunkai arc-back-arc system was one of a series of separate convergent margin settings, which included the Shuangxiwu (~970-880Ma) and Jiangnan (~870-820Ma) systems that developed in the SCB. The formation and closure of these arc-back-arc systems resulted in the northwestwardly episodic amalgamation of various pieces of the Yangtze and Cathaysia to finally form the SCB. These signatures require the SCB to occupy an exterior accretionary orogen along the periphery of Rodinia during 990-820Ma, rather than to have formed through Mesoproterozoic Sibao orogenesis within the interior of Rodinia. © 2013 Elsevier B.V.

Wang Y.,CAS Guangzhou Institute of Geochemistry | Fan W.,CAS Guangzhou Institute of Geochemistry | Zhang G.,Northwest University, China | Zhang Y.,CSIRO
Gondwana Research | Year: 2013

The Phanerozoic tectonic regimes of the South China Block (SCB) hold a key to understanding of its geodynamic evolution with respect to formation of numerous mineral resources. Despite long-time debates in the past three decades, there is still no consensus on the two key points whether the Phanerozoic tectonothermal events were due to subduction of the Pacific plate or intracontinental reworking and whether the three periods of tectonothermal events in the middle Paleozoic (Kwangsian), Triassic (Indosinian) and Jurassic-Cretaceous (Yanshanian) are mainly driven by tectonic transition in subduction of the oceanic crust from Paleotethyan in the west to Pacific in the east. This paper presents an overview of key geological observations in the SCB with respect to its Phanerozoic tectonics. Available data show that there are distinctive sedimentary, magmatic, structural and metamorphic records across the Xuefeng-Jiangnan Domain in the SCB. The geological signatures associated with the Kwangsian and Indosinian tectonothermal events are predominantly preserved in the eastern SCB, including the eastern Yangtze and Cathaysia Blocks to the east of the Xuefeng-Jiangnan Domain. They are characterized by strong thrusting/transpression, anatexic granitic magmatism, high-grade metamorphism and the poor involvement of the juvenile mantle-derived rocks. The two events were dated at ca. 400-460. Ma and ca. 200-250. Ma, respectively. The Yanshanian tectonothermal event is dominantly represented by the development of a wide magmatic belt of exceeding 1300. km (from the coastal province to the Xuefeng-Jiangnan Domain) and a broad deformational belt of more than 2000. km (from the coastal province to the Sichuan basin). The Yanshanian I-, S- and A-type granites, syenite and volcanic rocks display two arrays, which are oblique and parallel to the coastal provinces of the southeast China, respectively. They were mainly formed at the three age-spans of 152-180. Ma, 120-130 and 87-107. Ma with the peak of 158. Ma, 125. Ma and 93. Ma, respectively. The stillstand time of the Yanshanian magmatism was temporally overlapped by the deformation time of the top-to-the-NW progressive transpression or sinistral strike-slip at 132-142. Ma and 95-112. Ma, respectively. In conjunction with the observations and controversies, a geodynamic model is proposed for the Mesozoic tectonic evolution of the SCB. © 2012 International Association for Gondwana Research.

Xu W.-C.,Wuhan University | Zhang H.-F.,Wuhan University | Guo L.,Wuhan University | Yuan H.-L.,Northwest University, China
Lithos | Year: 2010

Post-collisional (26-10 Ma) high Sr/Y and HREE-depleted intrusive rocks occur in an E-W trending belt paralleling the Yarlung-Zangbo suture in south Tibet. Their petrogenesis has been a subject of debate. Here, we present chronological, geochemical and Sr-Nd-Hf isotopic data for two newly discovered large-volume high Sr/Y granitoids (the Pagu granodiorite and the Nanmuqie granite) and three high Sr/Y porphyries intruding the granitoids in the Lhasa terrane. LA-ICP-MS zircon U-Pb dating for the Pagu granodiorite and Nanmuqie granite yielded identical magma crystallization ages of 14.0-14.4 Ma, which is indistinguishable from their associated high Sr/Y porphyries (14.2-14.6 Ma). The granitoid was intruded at middle-crust depth, whereas the porphyry was intruded at upper-crust depth, indicating that the Lhasa terrane has experienced a rapid crustal uplift during the high Sr/Y magma emplacement. Zircon Hf isotopic and whole-rock Sr-Nd isotopic compositions for these granitoids and porphyries suggest that their magmas were dominantly derived from partial melting of crustal materials. The granitoids and porphyries have εHf(t) values overlapping with the mafic granulites in the Himalayan terrane (Indian plate). Their Sr-Nd isotopic compositions show two-endmember mixing between the Himalayan mafic lower crust and the ultrapotassic lavas/the Lhasa lower crust. We suggest that the high Sr/Y magmas in the Lhasa terrane could be derived from partial melting of subducted Indian mafic lower crust with incorporation of the ultrapotassic lava and/or the Lhasa lower crust components. Our study suggests a new model for the high Sr/Y magma generation in the Lhasa terrane and provides a line of geochemical evidence that the Indian continental crust was subducted beneath the southern Lhasa terrane in the early-middle Miocene. © 2009 Elsevier B.V. All rights reserved.

Liu S.,PLA Air Force Aviation University | Xu J.,PLA Air Force Aviation University | Xu J.,Northwest University, China
International Journal of Rock Mechanics and Mining Sciences | Year: 2013

Dynamic mechanical experiments are carried out on marble under different temperatures and different impact loadings by using the high temperature split Hopkinson pressure bar (SHPB) experimental system which is set up by integrating the 100. mm diameter SHPB with high temperature device. Combining the transformation of mineral components with the change of mineral particles under high temperatures, the dynamic mechanical characteristics are analyzed and the essence of rock fracture is explored. The experimental results show that the stress-strain curves under impact loadings and different temperatures have the same change law below 800 °C. When temperature exceeds 800 °C, the densification stage prolongs, the curve moves towards right quickly, the slope decreases and the yielding stage extends evidently. The dynamic mechanical characteristics of marble take on obvious temperature effects. The peak stress, peak strain and elastic modulus with the same impact velocity fluctuate in different extents with the increase of temperature before 400 °C. When temperature is above 400 °C, the peak stress, peak strain and elastic modulus increase or decline nearly linearly with the increase of temperature. There is remarkable difference among dynamic failure modes of marble under different temperatures. Especially, when temperature reaches 1000 °C, the fragments are powder and uniform particles. © 2013.

Huang Z.,Northwest University, China | Zhu H.,Northwest University, China | Yan R.,Northwest University, China | Wang S.,Northwest University, China | Wang S.,Washington State University
Biosystems Engineering | Year: 2015

Radio frequency (RF) heating is considered as a potential postharvest technology for disinfesting legumes. However, the non-uniformity in RF heating is still a major problem in developing effective RF heat treatments for pest control and other applications. A computer simulation model was developed with a finite element-based commercial software, COMSOL, to analyse the temperature distributions. Dry soybeans packed in a rectangular plastic container were used to determine the heating uniformity and validate the simulation model using a 27.12MHz, 6kW RF system. Both simulated and experimental results showed similar heating patterns in RF treated soybeans, in which corners and edges were more heated and the temperature values were higher in the lower part of the container. The simulation results demonstrated that the RF heating uniformity could be improved using a similar dielectric material around the samples, a smaller top plate area (similar to the sample size), and placing the samples in the middle of the two plate electrodes. The simulation model developed in this study could be applied to improve the RF heating uniformity and to optimise the treatment parameters. © 2014 IAgrE.

Zhang R.,Nanyang Technological University | Zhang R.,Northwest University, China | Xu Z.-B.,Xi'an Jiaotong University | Huang G.-B.,Nanyang Technological University | Wang D.,La Trobe University
IEEE Transactions on Neural Networks and Learning Systems | Year: 2012

The online backpropagation (BP) training procedure has been extensively explored in scientific research and engineering applications. One of the main factors affecting the performance of the online BP training is the learning rate. This paper proposes a new dynamic learning rate which is based on the estimate of the minimum error. The global convergence theory of the online BP training procedure with the proposed learning rate is further studied. It is proved that: 1) the error sequence converges to the global minimum error; and 2) the weight sequence converges to a fixed point at which the error function attains its global minimum. The obtained global convergence theory underlies the successful applications of the online BP training procedure. Illustrative examples are provided to support the theoretical analysis. © 2012 IEEE.

Xiang B.,Wuhan University | Xiang B.,University of Western Ontario | Jiang D.,Northwest University, China
Journal of Structural Geology | Year: 2013

We test the hypothesis that small ductile shear zones are developed from initial rheologically weak domains. We regard weak domains as ellipsoidal inhomogeneities and apply Eshelby's formalism extended for power-law viscous materials to investigate the kinematics and finite strain evolution of the partitioned flow fields in weak domains. We show that, under an imposed bulk flow field, weak domains, regardless of their initial shapes and orientations, deform into zone-like features at relatively small bulk strains and the deformation paths inside weak domains have all characteristics expected in ductile shear zones. We apply our model to the Cap de Creus area Spain, where abundant small ductile shear zones exist. To relate the fabrics inside these shear zones with the regional deformation, we take a multi-scale approach. We assume that the area contained many weak domains which were randomly shaped and oriented initially and were deformed into shear zones eventually in response to the regional flow. We constrain the regional flow field by the fabric patterns across the area and compute numerically the partitioned flow fields in individual weak domains. The latter are related to fabrics inside shear zones. Our model reproduces first-order features of field-observed fabrics. Although the deformation path of each shear zone was close to simple shearing, the deformation of the whole belt was not. Our approach also resolves the strain compatibility problem for a finite-sized shear zone embedded in a far less deformed country rock. © 2013 Elsevier Ltd. All rights reserved.

Zhang J.,Northwest University, China | Tuomainen P.,University of Helsinki | Siika-aho M.,VTT Technical Research Center of Finland | Viikari L.,University of Helsinki
Bioresource Technology | Year: 2011

Recombinant xylanase preparations from Nonomuraea flexuosa (Nf Xyn, GH11) and Thermoascus aurantiacus (Ta Xyn, GH10) were evaluated for their abilities to hydrolyze hydrothermally pretreated wheat straw. The GH family 10 enzyme Ta Xyn was clearly more efficient in solubilizing xylan from pretreated wheat straw. Improvement of the hydrolysis of hydrothermally pretreated wheat straw by addition of the thermostable xylanase preparations to thermostable cellulases was evaluated. Clear synergistic enhancement of hydrolysis of cellulose was observed when cellulases were supplemented even with a low amount of pure xylanases. Xylobiose was the main hydrolysis product from xylan. It was found that the hydrolysis of cellulose increased nearly linearly with xylan removal during the enzymatic hydrolysis. The results also showed that the xylanase preparation from T. aurantiacus, belonging to GH family 10 always showed better hydrolytic capacity of solubilizing xylan and acting synergistically with thermostable cellulases in the hydrolysis of hydrothermally pretreated wheat straw. © 2011 Elsevier Ltd.

Cai J.,Northwest University, China | Cai J.,University of Alberta | Tyree M.T.,University of Alberta | Tyree M.T.,U.S. Department of Agriculture
Plant, Cell and Environment | Year: 2010

The objective of this study was to quantify the relationship between vulnerability to cavitation and vessel diameter within a species. We measured vulnerability curves (VCs: percentage loss hydraulic conductivity versus tension) in aspen stems and measured vessel-size distributions. Measurements were done on seed-grown, 4-month-old aspen (Populus tremuloides Michx) grown in a greenhouse. VCs of stem segments were measured using a centrifuge technique and by a staining technique that allowed a VC to be constructed based on vessel diameter size-classes (D). Vessel-based VCs were also fitted to Weibull cumulative distribution functions (CDF), which provided best-fit values of Weibull CDF constants (c and b) and P50 = the tension causing 50% loss of hydraulic conductivity. We show that P50 = 6.166D-0.3134 (R2 = 0.995) and that b and 1/c are both linear functions of D with R2 > 0.95. The results are discussed in terms of models of VCs based on vessel D size-classes and in terms of concepts such as the 'pit area hypothesis' and vessel pathway redundancy. © 2010. This article is a US Government work and is in the public domain in the USA.

Wu F.,Northwest University, China | Zhou W.,Xi'an Jiaotong University
Heat Transfer Research | Year: 2015

With two kinds of methods of boundary condition treatment, three-dimensional turbulent flow and heat transfer problems in two types of internally finned tubes with a blocked core-tube have been studied numerically by the realizable k-ε model. The numerical simulation results obtained from two calculation models were compared with experimental data. It was found that the simulation results obtained from the turbulent flow model are closer to the experimental values than those obtained from the laminar flow model. Meanwhile, it has been found that the critical Reynolds number for the flow that develops in internally finned tubes from a laminar flow to a turbulent one is much less than the Reynolds number for traditional bare tubes. The calculation results also indicate that the periodical ridges inside the finned tubes change the distribution of the inner flow field and temperature profile. Unlike straight tubes, in internally finned tubes, a secondary vortex flow emerges that plays a definitely destructive role for the flow boundary layer and increases the turbulent kinetic energy of the flow field. With the field synergy principle, a contrasting analysis of the intensified heat exchange mechanism for internally finned tubes and a bare annular tube was performed quantitatively. The results show that the field synergy degree of longitudinally ridged and internally finned tubes is bett er than that of bare annular tubes, which enhance heat transfer. © 2015 by Begell House, Inc.

Wu F.,Northwest University, China | Zhou W.,Xi'an Jiaotong University | Ma X.,Northwest University, China
International Journal of Heat and Mass Transfer | Year: 2015

This study reports a numerical investigation of the natural convective flow and heat transfer in a rectangular cavity filled with a heat-generating porous medium by adopting the local thermal non-equilibrium model. The top and bottom walls of the enclosure are adiabatic and the left and right walls are partially heated and partially cooled by sinusoidal temperature profile. The results show that periodic variations with positive and negative values appear in the isotherms for fluid phase and solid phase, and the periodicity increases with the increase of N. The phase deviation has significant influence on fluid flow and heat transfer in the porous cavity. When N is large enough (N = 32), patterns of streamlines, isotherms for fluid phase and solid phase display like that of uniform thermal boundary condition case, and the total heat transfer rate through the whole cavity is close to that resulted by uniform thermal boundary condition. The heat transfer of porous cavity can be enhanced by sinusoidal thermal boundary condition and the phase deviation has tiny effect on the heat transfer of cavity when N is large enough (N = 32). The increase of inter-phase heat transfer coefficient leads to faster reduction of Q with the increase of periodicity parameter. © 2015 Elsevier Ltd. All rights reserved.

Su H.,PLA Air Force Aviation University | Xu J.,PLA Air Force Aviation University | Xu J.,Northwest University, China | Ren W.,PLA Air Force Aviation University
Materials and Design | Year: 2014

Strain rate effect and temperature effect are two important factors affecting the mechanical behavior of concrete. Each of them has been studied for several years. However, the two factors usually work together in the engineering practice. It is necessary to understand the mechanical responses of concrete under high strain rate and elevated temperature. A self-designed high temperature SHPB apparatus was used to study the dynamic compressive mechanical properties of concrete at elevated temperature. The results show that the dynamic compressive strength and specific energy absorption of concrete increase with strain rate at all temperatures. The elastic modulus decreases obviously with strain rate at room temperature and stabilizes at a level with slightly decrease at elevated temperature. The dynamic compressive strength of concrete at 400. °C increases by nearly 14% compared to the room temperature. However, it decreases at 200. °C, 600. °C and 800. °C with the decrease ratio of 20%, 16% and 48%, respectively. The dynamic elastic modulus decreases largely subjected to elevated temperature. The specific energy absorption at 200. °C, 400. °C and 600. °C is higher than room temperature and decreases to be lower than room temperature at 800. °C. Formulas are established under the consideration of mutual effect of strain rate and temperature. © 2013 Elsevier Ltd.

Dong Y.,Northwest University, China | Zhang G.,Northwest University, China | Neubauer F.,University of Salzburg | Liu X.,Northwest University, China | And 3 more authors.
Gondwana Research | Year: 2011

The eastern part of the Central Tianshan Belt in China is characterized by abundant granitoids, which are not only indicators of the interaction between crust and mantle but also can be used for tracking the tectonic evolutionary history of the orogen. Four granitic plutons, muscovite granites (MG), biotite monzonitic granites (BMG), biotite granites (BG), and alkali granites (AG), have been recognized to have intruded in the Mishigou area, Central Tianshan Belt. The MG has pronounced a S-type affinity, which is strongly peraluminous with a high aluminum saturation index, and displays positive Rb, Th, U and LREE anomalies with a strong negative Ba, Nb, Sr, P, Ti and Eu anomalies. Therefore, the magma of the MG is considered to have been derived from melting of thickened continental crust, which is composed mainly of the sediments eroded from a pre-Silurian continental island-arc. The U-Pb zircon age of 424.5 ± 2.6. Ma constrains the age of MG and crust thickening. The BG and BMG granitoids display I-type geochemical features and have affinities to subduction arcs. Both of them are characterized by calc-alkaline peraluminous granites with a significant LREE enrichment and a negative Eu anomaly, as well as a depletion in Ba, Nb, Ta, Sr, P and Ti and an enrichment in Rb, Th, U, Nd, Zr and Sm. These characteristics indicate that they were derived from a mixed magma source between lower continental crust and the input of components derived from the mantle wedge above the subduction zone. The LA-ICPMS zircon U-Pb ages of 411 ± 4.7. Ma and 402 ± 3.4. Ma represent the formation ages of the BG and BMG granitoids, respectively, which also constrain that the subduction of the South Tianshan oceanic crust also occurred during Early Devonian time. The AG shows a typical A-type granite affinity with depletion of Nb, Ta, Sr, P, Ti and Y. It is interpreted that AG was formed in a within-plate tectonic setting, and related to continental up-doming and rifting zones as a consequence of the extensional collapse after the collision of the Tianshan orogen. The U-Pb zircon age of 290 ± 5.1. Ma represents the formation age of the AG, and the time of the extensional collapse and rifting. © 2011 International Association for Gondwana Research.

Peters T.J.,Vanderbilt University | Ayers J.C.,Vanderbilt University | Gao S.,Northwest University, China | Gao S.,Wuhan University | Liu X.-M.,Northwest University, China
Gondwana Research | Year: 2013

The Huwan Shear Zone (HSZ) is an eclogite bearing transpressive wrench zone located along the Shangdan Suture that juxtaposes the Paleozoic Qinling and Mesozoic Hong'an-Dabie orogenic terrains. The region preserves a complex history that bridges the gap between adjacent orogenic terrains. Simultaneous in-situ trace element, U-Th-Pb and Lu-Hf-isotope analysis of zircon grains from samples of the Xiongdian and Sujiahe eclogite identify a late Carboniferous to early Permian period of high pressure metamorphism, ca. 283 to 306Ma. Zircon grains are observed to respond to metamorphic overprint via a two stage process: (1) An initial prograde stage of fluid catalyzed interface coupled dissolution-reprecipitation, involving exsolution of a non-ideal solid solution thorite (ThSiO4) end member and loss of highly incompatible components (LREE and Pb), (2) A second stage of coupled zircon dissolution, coarsening, and new rim growth in equilibrium with garnet at high pressure conditions. We identify Proterozoic whole rock Sm-Nd and zircon grain Lu-Hf isotopic evidence which challenges the traditional interpretation that the Xiongdian and Sujiahe eclogite formed in response to early Paleozoic mantle melting and oceanic crust generation. We argue the Huwan Shear Zone contains no conclusive evidence of early/middle Paleozoic oceanic crust, but rather Proterozoic crustal components analogous to those found in the Northern Qinling Terrain and associated with formation of the Shangdan Suture. We present a simpler geodynamic model involving continuous convergence and accretion of terrains onto the southern margin of the North China Block during the Paleozoic Qinling and Mesozoic Dabie orogenies. © 2012 International Association for Gondwana Research.

Dong Y.,Northwest University, China | Zhang G.,Northwest University, China | Hauzenberger C.,University of Graz | Neubauer F.,University of Salzburg | And 3 more authors.
Lithos | Year: 2011

The tectonic framework and the evolutionary history of the Qinling orogenic belt are keys for understanding the convergent processes between the North China and South China blocks. The widely exposed ophiolitic and subduction-related volcanic melange along the Shangdan and Erlangping belts provides important constraints on the tectonic evolutionary processes of the Qinling orogen. The melange in the Shangdan zone is predominantly composed of ultramafic and mafic rocks that can be divided into three geochemical groups: (1) N- MORB type; (2) E-MORB type; and (3) island-arc/active continental margin-related basalts. The samples with N- and E-MORB affinity are characterized by depletion or slight enrichment of LREE without fractionation of HFSE and no negative Nb-Ta anomaly. The island-arc/active continental margin-related basalts are typically depleted in Nb-Ta and Ti. It is inferred that the melange within the Shangdan suture represents remnants of an oceanic crust and associated volcanics. An age for the melange can be constrained by a U-Pb zircon age of 517.8 ± 2.8. Ma, obtained from the gabbro within the E-MORB-type ophiolite in the Yanwan area.To the north of the suture zone, the Erlangping melange consists similarly of ultramafic and mafic rocks, andesites and rhyolites. The mafic and andesitic rocks exhibit strong depletion of Nb-Ta and Ti indicating a subduction-related affinity. However, their depletion in Nb-Ta is weaker than that of the island-arc/active continental margin-related volcanic rocks. Taken together, the two ophiolitic melange zones indicate the existence of an early Palaeozoic Shangdan Ocean that was associated with a back-arc basin on the northern North Qinling Island arc terrane, separating the South China from the North China blocks. © 2010 Elsevier B.V.

Li S.-C.,Xi'an Jiaotong University | Zhao L.-C.,Northwest University, China
Journal of the Optical Society of America B: Optical Physics | Year: 2014

We investigate the properties of phase transitions in a weakly coupled ultracold atom-molecule boson system based on the phase space analysis approach. We identify the pure molecular and mixed atom-molecule phases of the system by different values of the time average of molecular population. When applying a periodic modulation on the energy detuning, we find that the atom-molecule mixing dynamics can be well controlled. For both high- and low-frequency modulations, it is shown that the transition points can be shifted effectively by choosing parameters of the periodic modulation appropriately. The analytical expressions for the dependence of the transition parameters on the modulation parameters are also obtained for the two cases. In particular, when the modulation with a frequency near the atom-molecule transition frequency is applied, the resonance between the periodic modulation and atom-molecule Rabi oscillation will emerge, which can affect the atom-molecule mixing dynamics dramatically and lead to the complex chaos phenomenon. © 2014 Optical Society of America.

Yan B.,Northwest University, China | Tomer M.D.,U.S. Department of Agriculture | James D.E.,U.S. Department of Agriculture
Journal of Soil and Water Conservation | Year: 2010

River valleys have been influenced by sediment derived from agricultural erosion and channel straightening intended to hasten flood routing. Post-settlement alluvium (PSA) has been little documented in tile-drained areas of the upper Midwest, where agricultural setdement began around 1850, and few soils are highly erodible.This study investigated channel movement and PSA accumulation along the South Fork of the Iowa River. Channels of the South Fork and tributary Tipton Creek were digitized using rectified aerial photographs taken in 1939 and 2002. Soil cores were collected along valley-crossing transects to determine PSA extent and thickness. Within 80 m (262 ft) of the South Fork, PSA averaged 0.78 m (30.7 in) thick and 85% frequency of occurrence. Beyond 80 m, PSA decreased below 50%. Within 43 m (141 ft) of Tipton Creek, PSA averaging 0.58 m thick occurred with 75% frequency. An estimated 9.2 × 106 Mg (10.2 × 106 tn) of PSA is stored along these valleys, representing 156.6 Mg ha-1 (69.8 tn ac-1) of soil eroded from uplands since settlement. The volume of PSA is equivalent to 11 mm (0.44 in) runoff from the watershed. The valley's flood-storage capacity has been reduced by 5.1 × 106 m3 (4,123 ac ft), considering pore space of the PSA. Modern flooding events are accordingly exacerbated by accretion of agricultural sediment, compared to presetdement river conditions. Channels were straightened in response to local flood events, which reduced stream length by 10% and hastened routing to the Iowa River. Design of river restoration projects should take account of fluvial processes and how these processes are responding to historical sedimentation and channel straightening.

Zhao L.-C.,Northwest University, China | Li S.-C.,Xi'an Jiaotong University | Ling L.,South China University of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We investigate the solution in rational form for the Sasa-Satsuma equation on a continuous background which describes a nonlinear fiber system with higher-order effects including the third-order dispersion, Kerr dispersion, and stimulated inelastic scattering. The W-shaped soliton in the system is obtained analytically. It is found that the height of hump for the soliton increases with decreasing the background frequency in certain parameter regime. The maximum height of the soliton can be three times the background's height and the corresponding profile is identical with the one for the well-known eye-shaped rogue wave with maximum peak. The numerical simulations indicate that the W-shaped soliton is stable with small perturbations. Particularly, we show that the W-shaped soliton corresponds to a stable supercontinuum pulse by performing exact spectrum analysis. © 2014 American Physical Society.

Zhang J.,Northwest University, China | Tang M.,Northwest University, China | Viikari L.,University of Helsinki
Bioresource Technology | Year: 2012

Hemicelluloses have been found to be physical barriers in the hydrolysis of cellulose, and prevent the access of enzymes to cellulose surface. In addition, soluble hemicelluloses may strongly inhibit the cellulase activity. In this work, birchwood xylan clearly inhibited the enzymatic hydrolysis of wheat straw, Avicel and nanocellulose by cellulases. Hydrolysis efficiencies of cellobiohydrolase I (CBHI, from Thermoascus aurantiacus), cellobiohydrolase II (CBHII, from Trichoderma reesei) and endoglucanase II (from T. aurantiacus) were clearly inhibited by birchwood xylan, respectively. The strongest inhibitory effect of birchwood xylan was observed on the hydrolysis of Avicel by CBHI and CBHII, as a dramatically decreased formation of the main product, cellobiose. After additions of soluble and insoluble oat spelt xylan, cleaved cellobiose units by CBHI from cellulose chain decreased from 8 to 4 and 6, respectively. The results in this work demonstrated that xylans clearly inhibited the hydrolysis efficiencies of both endoglucanase and cellobiohydrolase. © 2012 Elsevier Ltd.

Zhang J.,Northwest University, China | Viikari L.,University of Helsinki
Bioresource Technology | Year: 2012

The effects of xylo-oligosaccharides (XOS) and xylose on the hydrolytic activities of cellulases, endoglucanase II (EGII, originating from Thermoascus aurantiacus), cellobiohydrolase I (CBHI, from T. aurantiacus), and cellobiohydrolase II (CBHII, from Trichoderma reesei) on Avicel and nanocellulose were investigated. After the addition of XOS, the amounts of cellobiose, the main product released from Avicel and nanocellulose by CBHI, decreased from 0.78 and 1.37. mg/ml to 0.59 and 1.23. mg/ml, respectively. During hydrolysis by CBHII, the amounts of cellobiose released from the substrates were almost cut in half after the addition of XOS. Kinetic experiments showed that xylobiose and xylotriose were competitive inhibitors of CBHI. The results revealed that the strong inhibition of cellulase by XOS can be attributed to the inhibitory effect of XOS especially on cellobiohydrolase I. The results indicate the necessity to totally hydrolyze xylo-oligosaccharides into the less inhibitory product, xylose, to increasing hydrolytic efficiency. © 2012 Elsevier Ltd.

Pakarinen A.,University of Helsinki | Zhang J.,Northwest University, China | Brock T.,University of Helsinki | Maijala P.,University of Helsinki | Viikari L.,University of Helsinki
Bioresource Technology | Year: 2012

Pectinolytic enzymes, steam explosion and alkaline treatment were used to assess the role of pectin for the accessibility of hydrolytic enzymes in the enzymatic hydrolysis of biomass. Hemp (Cannabis sativa L.), a potential energy crop especially in boreal climate with a low need of fertilizers, was used in the study either as untreated or anaerobically preserved raw material. Addition of pectinases increased the hydrolysis yield by 26%, 54%, and 64% from the theoretical carbohydrates of untreated, acid, and alkali-preserved materials, respectively. Steam explosion and hot alkali treatment increased the conversion of the total carbohydrates by 78% and 60%, respectively, compared to the untreated hemp. Elevated separation of cells within the hemp stalk tissues and an increased surface area was revealed after hot alkali or pectinase treatments, contributing to the increased conversion to sugars by commercial enzymes. © 2011 Elsevier Ltd.

Xu X.-M.,Northwest University, China | Xu X.-M.,East Malling Research | Jeffries P.,University of Kent | Pautasso M.,Imperial College London | Jeger M.J.,Imperial College London
Phytopathology | Year: 2011

Effective use of biological control agents (BCAs) is a potentially important component of sustainable agriculture. Recently, there has been an increasing interest among researchers in using combinations of BCAs to exploit potential synergistic effects among them. The methodology for investigating such synergistic effects was reviewed first and published results were then assessed for available evidence for synergy. Correct formulation of hypotheses based on the theoretical definition of independence (Bliss independence or Loewe additivity) and the subsequent and statistical testing for the independence-synergistic-antagonistic interactions have rarely been carried out thus far in studies on biocontrol of plant diseases. Thus, caution must be taken when interpreting reported "synergistic" effects without assessing the original publications. Recent theoretical modeling work suggested that disease suppression from combined use of two BCAs was, in general, very similar to that achieved by the more efficacious one, indicating no synergistic but more likely antagonistic interactions. Only in 2% of the total 465 published treatments was there evidence for synergistic effects among BCAs. In the majority of the cases, antagonistic interactions among BCAs were indicated. Thus, both theoretical and experimental studies suggest that, in combined use of BCAs, antagonistic interactions among BCAs are more likely to occur than synergistic interactions. Several research strategies, including formulation of synergy hypotheses in relation to biocontrol mechanisms, are outlined to exploit microbial mixtures for uses in biocontrol of plant diseases. © 2011 The American Phytopathological Society.

Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwest University, China | Liu S.,PLA Air Force Aviation University
Yantu Lixue/Rock and Soil Mechanics | Year: 2012

The size distribution of marble fragmentation subjected to impact loading is analyzed statistically from the view of fractal geometry. The result indicates that the fragment-size distribution of fragments has fractal property. Fractal dimension can quantitatively describe the fragment distribution characteristics of fracture process of marble; and can reflect the fragmentation degree reasonably. There is obvious relativity between the average fragment-size of marble and impact loading speed; but the relativity declines with the increase of loading speed. Subsequently, the relationship between the specific energy absorption and fractal dimension is established. It is illustrated that energy absorbency of marble is crucial factors influencing the changes of fractal dimension. The fractal dimension is an appropriate parameter which generally indicates the whole process of rock fragmentation.

Eusebio-Cope A.,Okayama University | Sun L.,Northwest University, China | Tanaka .,Okayama University | Chiba S.,Okayama University | And 2 more authors.
Virology | Year: 2015

The chestnut blight fungus, Cryphonectria parasitica, is an important plant pathogenic ascomycete. The fungus hosts a wide range of viruses and now has been established as a model filamentous fungus for studying virus/host and virus/virus interactions. This is based on the development of methods for artificial virus introduction and elimination, host genome manipulability, available host genome sequence with annotations, host mutant strains, and molecular tools. Molecular tools include sub-cellular distribution markers, gene expression reporters, and vectors with regulatable promoters that have been long available for unicellular organisms, cultured cells, individuals of animals and plants, and certain filamentous fungi. A comparison with other filamentous fungi such as Neurospora crassa has been made to establish clear advantages and disadvantages of C. parasitica as a virus host. In addition, a few recent studies on RNA silencing vs. viruses in this fungus are introduced. © 2014 Elsevier Inc.

Guo W.,Northwest University, China | Zhu X.,Northwest University, China | Liu Y.,Northwest University, China | Zhuang H.,U.S. Department of Agriculture
Journal of Food Engineering | Year: 2010

The dielectric properties of pure yellow locust, jujube and rape flower honey and their water-adulterated products with water content from 18% to 42.6% were measured with open-ended coaxial-line probe technology and a network analyzer from 10 to 4500 MHz at 25 °C. Dielectric constants of pure honeys and water-added honey samples decreased monotonically with increasing frequency, and increased with increasing water content. Dielectric relaxation was evident in the dielectric loss factors. The critical frequency and the maximum loss factor increased with increasing water content. There were strong linear correlations between the dielectric constant and the total soluble solids and water contents. The linear coefficients of determination were higher than 0.995 from 650 to 960 MHz. The good linear correlations and the sufficient penetration depth >20 mm below 960 MHz, suggest that microwave dielectric properties could be used in developing sensors to determine sugar and water contents. © 2009 Elsevier Ltd.

Zhao H.,Northwest University, China | Zhao H.,Washington State University | Kim Y.K.,Washington State University | Huang L.,Northwest University, China | Xiao C.L.,Washington State University
Postharvest Biology and Technology | Year: 2010

Gray mold caused by Botrytis cinerea is a common postharvest disease of pome fruit. Thiabendazole was the most commonly used postharvest fungicide prior to the registration of fludioxonil and pyrimethanil in 2004 for postharvest use on pome fruit. In this study, 83 and 40 isolates of B. cinerea that had not been exposed to fludioxonil and pyrimethanil were obtained from apple and pear, respectively, screened for resistance to thiabendazole, and tested for sensitivity to fludioxonil and pyrimethanil. Three isolates from apple were highly resistant to thiabendazole, while all remaining isolates were sensitive to thiabendazole. EC50 values of fludioxonil ranged from 0.003 to 0.038 (mean = 0.005) mg/L for apple isolates and from 0.003 to 0.008 (mean = 0.005) mg/L for pear isolates. EC50 values of pyrimethanil ranged from 0.013 to 0.173 (mean = 0.060) mg/L and from 0.015 to 0.117 (mean = 0.048) mg/L for apple and pear isolates, respectively. One apple isolate exhibited reduced sensitivity to fludioxonil with EC50 of 0.038 mg/L, which was significantly higher than those of remaining isolates tested and was considered resistant to fludioxonil. After 20 successive generations on potato dextrose agar and four generations on apple fruit, the fludioxonil-resistant isolate retained the same level of resistance to fludioxonil as the initial generation. However, it showed a higher sensitivity to osmotic stress in vitro, was less pathogenic and virulent on apple fruit, and produced fewer conidia in vivo at 0 °C than fludioxonil-sensitive isolates. On apple fruit at 0 °C, the fludioxonil-resistant isolate was effectively controlled by thiabendazole and pyrimethanil but only partially controlled by fludioxonil. The results indicate that insensitivity to fludioxonil was present in a non-fludioxonil-exposed population of B. cinerea from pome fruit in the region but at a low frequency and that the vast majority of isolates in the baseline population of B. cinerea from pome fruit in the region were sensitive to and can be effectively controlled by the two newly registered postharvest fungicides. © 2009 Elsevier B.V. All rights reserved.

Guo W.,Northwest University, China | Wang S.,Washington State University | Tiwari G.,Washington State University | Johnson J.A.,U.S. Department of Agriculture | Tang J.,Washington State University
LWT - Food Science and Technology | Year: 2010

Dielectric properties data are important in developing thermal treatments using radio frequency (RF) and microwave (MW) energy and are essential in estimating heating uniformity in electromagnetic fields. Dielectric properties of flour samples from four legumes (chickpea, green pea, lentil, and soybean) at four different moisture contents were measured with an open-ended coaxial probe and impedance analyzer at frequencies of 10-1800 MHz and temperatures of 20-90 °C. The dielectric constant and loss factor of the legume samples decreased with increasing frequency but increased with increasing temperature and moisture content. At low frequencies and high temperatures and moisture contents, negative linear correlations were observed between the loss factor and frequency on a log-log plot, which was mainly caused by the ionic conductance. At 1800 MHz, the dielectric properties data could be used to estimate the legume sample density judging from high linear correlations. Loss factors for the four legume samples were similar at 27 MHz, 20 °C and low moisture contents (e.g. <15 g/100 g). At the highest moisture content (e.g. 20 g/100 g) soybean had the highest loss factor at 27 MHz and 20 °C, followed by lentil, green pea, and chickpea. The difference in loss factor among the four legumes did not show clear patterns at 915 MHz. Deep penetration depths at 27 MHz could help in developing large-scale industrial RF treatments for postharvest insect control or other applications that require bulk heating in legumes with acceptable heating uniformity and throughputs. © 2009.

Background: Deployment of cultivars with different resistance in mixtures is one means to manage plant diseases and prolong the life of resistance genes. One major concern in adopting mixtures is the development of 'super-races' that can overcome many resistance genes present in the mixture. A stochastic simulation model was developed to study the dynamics of virulence alleles in two-cultivar mixtures of perennial crops, focusing on the effects of cost of virulence and pathogen reproduction mechanism. The simulated mechanism of virulence has characteristics of both major and minor genes.Results: Random genetic drift due to repeated population crashes during the overwintering phase led to fixation of a single fungal genotype (in terms of its virulence), often within 100 seasons. Overall, cost of virulence is most important in determining the virulence dynamics under the present model formulation. With cost of virulence incorporated, nearly all simulation runs ended up with a single fungal genotype that can infect only one of the two cultivars. In absence of cost of virulence, most of the simulation runs ended up with fungal genotypes that can infect both host cultivars but in many cases do not contain the maximum possible number of virulence alleles due to random drift. A minimum of 20% sexual reproduction between strains from different cultivars is necessary to ensure that the final fixed strains are able to infect both cultivars. Although the number of virulence alleles in the final genotype and the time to fixation are affected by simulation factors, most of the variability was among replicate simulation runs (i.e. stochastic in nature). The time to fixation is generally long relative to cropping cycles.Conclusions: A single fungal genotype will dominate a population due to the bottleneck in overwintering with cost of virulence primarily determining whether the dominant genotype can infect both cultivars. However, the dominant genotype is unlikely to accumulate all the virulence alleles due to genetic drift. The risk of emergence and spread of super-races is insufficiently great to prevent the use of cultivar mixtures of perennial crops as a means to reduce disease development provided that host resistance structure in mixtures is altered every cropping cycle. © 2012 Xu; licensee BioMed Central Ltd.

Zhang R.,Nanyang Technological University | Zhang R.,Northwest University, China | Lan Y.,Nanyang Technological University | Huang G.-B.,Nanyang Technological University | Xu Z.-B.,Xi'an Jiaotong University
IEEE Transactions on Neural Networks and Learning Systems | Year: 2012

Extreme learning machines (ELMs) have been proposed for generalized single-hidden-layer feedforward networks which need not be neuron-like and perform well in both regression and classification applications. In this brief, we propose an ELM with adaptive growth of hidden nodes (AG-ELM), which provides a new approach for the automated design of networks. Different from other incremental ELMs (I-ELMs) whose existing hidden nodes are frozen when the new hidden nodes are added one by one, in AG-ELM the number of hidden nodes is determined in an adaptive way in the sense that the existing networks may be replaced by newly generated networks which have fewer hidden nodes and better generalization performance. We then prove that such an AG-ELM using Lebesgue p-integrable hidden activation functions can approximate any Lebesgue p-integrable function on a compact input set. Simulation results demonstrate and verify that this new approach can achieve a more compact network architecture than the I-ELM. © 2012 IEEE.

Jiao S.,Washington State University | Johnson J.A.,U.S. Department of Agriculture | Tang J.,Washington State University | Wang S.,Northwest University, China | Wang S.,Washington State University
Journal of Stored Products Research | Year: 2012

Radio frequency (RF) treatments are considered to be a potential postharvest technology for disinfesting legumes of internal seed pests such as the cowpea weevil. After treatment protocols are shown to control postharvest insects without significant quality degradation, it is important to scale-up laboratory RF treatments to industrial level applications. A 27.12MHz, 6kW RF unit with a built-in forced hot air system was used to conduct industrial scale-up studies. A treatment protocol was designed to provide 100% cowpea weevil mortality combined RF with forced hot air to heat product to 60°C for 10min, followed by forced ambient air cooling for 20min. An electrode gap (14.0cm) was chosen based on the electric current and heating time, and conveyor belt speed was set to 7.5m/h. Heating uniformity was evaluated by measuring post-treatment surface temperatures with a thermal image camera and interior temperatures with thermocouples. Changes in moisture content, color and germination were used to evaluate treatment effects on product quality. Finally, the RF system heating efficiency and throughput were calculated. Results showed that heating uniformity and quality of lentils in continuous RF treatment with hot air and movement were acceptable, the average heating efficiency of the RF system was 76.5% and throughput was 208.7kg/h. The average energy efficiency and throughput of the RF system provided sufficient data to develop an industrial-scale RF process as an alternative to chemical fumigation. © 2011 Elsevier Ltd.

Teng F.-Z.,University of Arkansas | Dauphas N.,University of Chicago | Helz R.T.,U.S. Geological Survey | Gao S.,Wuhan University | And 2 more authors.
Earth and Planetary Science Letters | Year: 2011

Diffusion plays an important role in Earth sciences to estimate the timescales of geological processes such as erosion, sediment burial, and magma cooling. In igneous systems, these diffusive processes are recorded in the form of crystal zoning. However, meaningful interpretation of these signatures is often hampered by the fact that they cannot be unambiguously ascribed to a single process (e.g., magmatic fractionation, diffusion limited transport in the crystal or in the liquid). Here we show that Mg and Fe isotope fractionations in olivine crystals can be used to trace diffusive processes in magmatic systems. Over sixty olivine fragments from Hawaiian basalts show isotopically fractionated Mg and Fe relative to basalts worldwide, with up to 0.4‰ variation in 26Mg/24Mg ratios and 1.6‰ variation in 56Fe/54Fe ratios. The linearly and negatively correlated Mg and Fe isotopic compositions [i.e., δ56Fe=(δ3.3±0.3)×δ26Mg], co-variations of Mg and Fe isotopic compositions with Fe/Mg ratios of olivine fragments, and modeling results based on Mg and Fe elemental profiles demonstrate the coupled Mg and Fe isotope fractionation to be a manifestation of Mg-Fe inter-diffusion in zoned olivines during magmatic differentiation. This characteristic can be used to constrain the nature of mineral zoning in igneous and metamorphic rocks, and hence determine the residence times of crystals in magmas, the composition of primary melts, and the duration of metamorphic events. With improvements in methodology, in situ isotope mapping will become an essential tool of petrology to identify diffusion in crystals. © 2011 Elsevier B.V.

Pu Z.,CAS Institute of Earth Environment | Pu Z.,Northwest University, China | Weiguo L.,CAS Institute of Earth Environment | Weiguo L.,Xi'an Jiaotong University
Organic Geochemistry | Year: 2011

We present δDwax values from different forms of plants and soils, and δDsw values from soil water along the northern slope of Mount Taibai, China. The results show a highly negative linear correlation of the δDwax values for soils with altitude (R2 0.74) and we observed the same correlation for δDsw values of soil water with altitude (R2 0.68). The δDwax of living plants behaves like the soil, but does not exhibit a significant linear correlation with altitude (R2 0.11). The δDwax values of woody plants and grasses also show a similar trend with respect to altitude with significant and no linear correlation, respectively (R2 0.50 for woody plants and 0.17 for grass), which suggest that the "altitude effect" can not be well documented for the δDwax values of living plants, which may be due to differences in plant type and/or evapotranspiration controlled by the plant microclimate. The εwax-sw values of woody plants, grasses and soil show minor fluctuations with altitude. However, the εwax-sw and δDwax values of woody plants are roughly 51‰ and 50‰ more positive, respectively, than those of grasses, suggesting that an "altitude effect" could be documented in the δDwax of woody plants and grasses, with each responding independently to changes in precipitationalong the altitude transect. Additionally, the εwax-sw values of soil are relatively constant with altitude, suggesting that the altitudinal change in the proportions between woody plant and grass input to soils will likely change the relationship between the δDwax values of soil n-alkanes and altitude. © 2010.

Xu X.-M.,Northwest University, China | Xu X.-M.,East Malling Research | Jeger M.J.,Imperial College London
Phytopathology | Year: 2013

There has been a trend for combined use of several biocontrol agents (BCAs) with an expectation of synergistic interactions among BCAs. However, previous modeling studies suggested that, under homogeneous and temporal-fluctuating conditions, combined use of two BCAs, in most cases, only results in efficacies similar to the more efficacious one used alone; a result consistent with published experimental data. The present modeling study investigated whether combined use of two mycoparasitic BCAs, two competitive BCAs, or a mycoparasitic and a competitive BCA leads to synergistic interactions under spatially heterogeneous conditions. In the model, there were two patches with varying relative sizes and two BCAs differentially adapted to the two patches. Within the range of model parameter values considered, combined use of two BCAs is more effective than the more efficacious BCA used alone in 72% of the simulated cases. There was also a considerable proportion ( 21%) of model simulations in which combined use of two BCAs led to synergy (i.e., efficacy was greater than expected under the assumption of Bliss independence, especially when each of the two BCAs can only survive in one [different] patch). Combined use of a mycoparasitic BCA with a competitive one is more likely to result in synergy than the other two BCA combinations. When biocontrol activities of individual BCAs are low or moderate, biocontrol efficacy arising from combined use of two BCAs does not depend greatly on biocontrol mechanisms. However, for high BCA activities, combined use with at least one competitive BCA resulted in better control than combined use of two mycoparasitic BCAs. The present modeling study emphasized the need for understanding the degree of spatial patchiness and quantitative relationships between biocontrol activities and external conditions in order to apply commercial BCAs effectively. © 2013 The American Phytopathological Society.

Huang G.-B.,Nanyang Technological University | Zhou H.,Nanyang Technological University | Ding X.,Xi'an Jiaotong University | Zhang R.,Nanyang Technological University | Zhang R.,Northwest University, China
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2012

Due to the simplicity of their implementations, least square support vector machine (LS-SVM) and proximal support vector machine (PSVM) have been widely used in binary classification applications. The conventional LS-SVM and PSVM cannot be used in regression and multiclass classification applications directly, although variants of LS-SVM and PSVM have been proposed to handle such cases. This paper shows that both LS-SVM and PSVM can be simplified further and a unified learning framework of LS-SVM, PSVM, and other regularization algorithms referred to extreme learning machine (ELM) can be built. ELM works for the "generalized" single-hidden-layer feedforward networks (SLFNs), but the hidden layer (or called feature mapping) in ELM need not be tuned. Such SLFNs include but are not limited to SVM, polynomial network, and the conventional feedforward neural networks. This paper shows the following: 1) ELM provides a unified learning platform with a widespread type of feature mappings and can be applied in regression and multiclass classification applications directly; 2) from the optimization method point of view, ELM has milder optimization constraints compared to LS-SVM and PSVM; 3) in theory, compared to ELM, LS-SVM and PSVM achieve suboptimal solutions and require higher computational complexity; and 4) in theory, ELM can approximate any target continuous function and classify any disjoint regions. As verified by the simulation results, ELM tends to have better scalability and achieve similar (for regression and binary class cases) or much better (for multiclass cases) generalization performance at much faster learning speed (up to thousands times) than traditional SVM and LS-SVM. © 2006 IEEE.

Zheng J.,Northwest University, China | Stewart C.E.,U.S. Department of Agriculture | Cotrufo M.F.,Colorado State University
Journal of Environmental Quality | Year: 2012

Biochar (BC) application to agricultural soils could potentially sequester recalcitrant C, increase N retention, increase water holding capacity, and decrease greenhouse gas (GHG) emissions. Biochar addition to soils can alter soil N cycling and in some cases decrease extractable mineral N (NO3- and NH4+) and N2O emissions.These benefits are not uniformly observed across varying soil types, N fertilization, and BC properties. To determine the effects of BC addition on N retention and GHG flux, we added two sizes (>250 and <250 μm) of oak-derived BC (10% w/w) to two soils (aridic Argiustoll and aquic Haplustoll) with and without N fertilizer and measured extractable NO3- and NH4+ and GHG efflux (N2O, CO2,and CH4) in a 123-d laboratory incubation. Biochar had no effect on NO3-, NH4+, or N2O in the unfertilized treatments of either soil. Biochar decreased cumulative extractable NO3- in N fertilizedtreatments by 8% but had mixed effects on NH4+. Greenhouse gas efflux differed substantially between the two soils, but generally with N fertilizer BC addition decreased N2O 3 to 60%, increased CO2 10 to 21%, and increased CH4 emissions5 to 72%. Soil pH and total treatment N (soil + fertilizer + BC) predicted soil N2O flux well across these two different soils. Expressed as CO2 equivalents,BC significantly reduced GHG emissions only in the N-fertilized silt loam by decreasing N2O flux. In unfertilized soils, CO2 was the dominant GHG component, and thedirection of the flux was mediated by positive or negative BC effects on soil CO2 flux.On the basis of our data, the use of BC appears to be an effective management strategy to reduce N leaching and GHG emissions,particularly in neutral to acidic soils with high N content. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwest University, China | Liu S.,PLA Air Force Aviation University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The tests on marble after different temperatures under dynamic loading at different impact velocities are carried out by using the split Hopkinson pressure bar (SHPB) apparatus 100 mm in diameter. The influences of impact velocity on the peak stress, peak strain and elastic modulus are studied. The test results show that the peak stress and peak strain after the same temperature increase linearly with the increasing impact velocity. When the temperature is above 800°C, the peak stress increases slightly and the peak strain increases obviously with the increase of impact velocity. However, the elastic modulus has no obvious impact velocity effect. The elastic modulus gradually declines with the increase of temperature. When the temperature reaches 1000°C, the elastic modulus nearly does not change with the variation of impact velocity. Considering the microstructure characteristics and the energy absorbency of marble, the effect of impact velocity on the dynamic mechanical characteristics is analyzed.

Luo X.,PLA Air Force Aviation University | Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwest University, China | Bai E.-L.,PLA Air Force Aviation University | Li W.,Airport Office
Materials and Design | Year: 2014

Cementitious materials and ceramic aggregates used as basic materials, ceramics-cement based porous material (CCPM) has been prepared. Φ100. mm SHPB has been improved by wave shaping techniques, which can guarantee the availability of the tests. Quasi static compression test and impacting compression test have been carried out, the damage process of specimen under loading has been analyzed, and mechanics parameters under different strain rates have been obtained, moreover, based on this, the mechanical properties of CCPM under impact loading, including strength property, deformation property, impacting toughness, have been studied, in addition, the prospect of CCPM's application has also been discussed. The results indicate that, the quasi static and impact compressive stress-strain curve of CCPM includes a strain plateau, which helps to better absorb energy; the dynamic strength increase factors of CCPM and the natural logarithm of relative strain rate are of a linear relationship; the relationship between the dynamic peak strain increase factors and the related strain rate can be described with an exponential linear, which shows obvious "damage softening" effect; with the increase of average strain rate, the impacting toughness of CCPM gets strengthened continuously and the impact toughness indexes are in a logarithm relationship with strain rate; CCPM is more strain rate sensitive than ordinary cement based composite materials. Thus it can be seen, CCPM possesses the advantageous mechanical properties of both porous materials and ordinary cement based composite materials. Besides, the material is easy to prepare and simple to make. Along with its high plasticity and low density, CCPM has a promising future to perform its potential advantages in engineering, especially in national defense engineering. © 2013 Elsevier Ltd.

Wu F.,Northwest University, China | Wang G.,Lanzhou University of Technology | Zhou W.,Xi'an Jiaotong University
Numerical Heat Transfer; Part A: Applications | Year: 2015

This article presents a numerical investigation of steady non-Darcy natural convection heat transfer in a square cavity filled with a heat-generating porous medium with partial cooling using a local thermal nonequilibrium (LTNE) model. Five different partial cooling boundary conditions and the fully cooled boundary condition are investigated under LTNE and local thermal equilibrium (LTE). The cooling portions of the left and the right sidewalls of the cavity are maintained at temperature T0 while the enclosure's top and bottom walls, as well as the inactive parts of its sidewalls, are kept insulated. The simulation results show that the placement order of wall cooling has a significant effect on the flow pattern and heat transfer rate. Compared with the fully cooled wall, the partially cooled wall of the cavity yielded a higher local Nusselt number for both fluid and solid phases. Under the same boundary conditions, the LTNE and LTE models can demonstrate significant differences in flow patterns and temperature fields. The total heat transfer rate increases with both Darcy number and Rayleigh number. Enhancement of interphase heat transfer coefficient (H) reduces the impact of Darcy number on the heat transfer rate of a porous cavity. Also, the total heat transfer rate of the porous medium decreases steadily with thermal conductivity ratio γ and interphase heat transfer coefficient H. © 2015 Copyright Taylor & Francis Group, LLC.

Xu X.-M.,Northwest University, China | Xu X.-M.,East Malling Research
Plant Pathology | Year: 2011

A simulation study was conducted to investigate epidemic development of a race-specific pathogen in cultivar mixtures over six consecutive seasons where the spatial position of each mixture component was systematically altered between seasons. Results showed that, even for a relative large genotype unit area in a mixture, altering cultivar positions between seasons could, on average, increase disease suppression by a third over the corresponding mixture without position changes between seasons. Overall, the disease suppression achieved by mixtures with position change between seasons was close to that achieved by random mixtures. Greater redistribution distance of overwintered inoculum reduced the disease control efficacy achieved by change in the position of individual mixture components between seasons. It is therefore concluded that using mixtures with a relatively large genotype unit area together with systematic changes in the spatial positions of individual mixture components between seasons is a feasible option for integrated disease management. © 2011 The Author. Plant Pathology © 2011 BSPP.

Zhang J.,Northwest University, China | Moilanen U.,University of Helsinki | Tang M.,Northwest University, China | Viikari L.,University of Helsinki
Biotechnology for Biofuels | Year: 2013

Background: The enzymatic hydrolysis step converting lignocellulosic materials into fermentable sugars is recognized as one of the major limiting steps in biomass-to-ethanol process due to the low efficiency of enzymes and their cost. Xylanases have been found to be important in the improvement of the hydrolysis of cellulose due to the close interaction of cellulose and xylan. In this work, the effects of carbohydrate-binding module (CBM family II) of the xylanase 11 from Nonomuraea flexuosa (Nf Xyn11) on the adsorption and hydrolytic efficiency toward isolated xylan and lignocellulosic materials were investigated. Results: The intact family 11 xylanase of N. flexuosa clearly adsorbed on wheat straw and lignin, following the Langmuir-type isotherm. The presence of the CBM in the xylanase increased the adsorption and hydrolytic efficiency on insoluble oat spelt xylan. But the presence of the CBM did not increase adsorption on pretreated wheat straw or isolated lignin. On the contrary, the CBM decreased the adsorption of the core protein to lignin containing substrates, indicating that the CBM of N. flexuosa xylanase did not contribute to the non-productive adsorption. Conclusion: The CBM of the N. flexuosa xylanase was shown to be a xylan-binding module, which had low affinity on cellulose. The CBM of the N. flexuosa xylanase reduced the non-specific adsorption of the core protein to lignin and showed potential for improving the hydrolysis of lignocellulosic materials to platform sugars. © 2013 Zhang et al.; licensee BioMed Central Ltd.

Zhang F.,Xi'an Jiaotong University | Guo X.,Xi'an Jiaotong University | Wang W.,Xi'an Jiaotong University | Yan H.,Northwest University, China | Li C.,Xi'an Jiaotong University
PLoS ONE | Year: 2011

Kashin-Beck Disease (KBD) is an endemic osteochondropathy, the pathogenesis of which remains unclear now. In this study, we compared gene expression profiles of articular cartilage derived respectively from KBD patients and normal controls. Total RNA were isolated, amplified, labeled and hybridized to Agilent human 1A 22 k whole genome microarray chip. qRT-PCR was conducted to validate our microarray data. We detected 57 up-regulated genes (ratios ≥2.0) and 24 down-regulated genes (ratios ≤0.5) in KBD cartilage. To further identify the key genes involved in the pathogenesis of KBD, Bayesian analysis of variance for microarrays(BAM) software was applied and identified 12 potential key genes with an average ratio 6.64, involved in apoptosis, metabolism, cytokine and growth factor and cytoskeleton and cell movement. Gene Set Enrichment Analysis (GSEA) software was used to identify differently expressed gene ontology categories and pathways. GSEA found that a set of apoptosis, hypoxia and mitochondrial function related gene ontology categories and pathways were significantly up-regulated in KBD compared to normal controls. Based on the results of this study, we suggest that chronic hypoxia-induced mitochondrial damage and apoptosis might play an important role in the pathogenesis of KBD. Our efforts may help to understand the pathogenesis of KBD as well as other osteoarthrosis with similar articular cartilage lesions. © 2011 Zhang et al.

Choi Y.-E.,Purdue University | Choi Y.-E.,U.S. Department of Agriculture | Xu J.-R.,Purdue University | Xu J.-R.,Northwest University, China
Molecular Plant-Microbe Interactions | Year: 2010

Fusarium verticillioides is one of the most important fungal pathogens of maize. Mycotoxin, fumonisins produced by this pathogen pose a threat to human and animal health. Because cAMP signaling has been implicated in regulating diverse developmental and infection processes in fungal pathogens, in this study, we aimed to elucidate the function of the cAMP-protein kinase A (PKA) pathway in toxin production and plant infection in F verticillioides. Targeted deletion mutants were generated for the CPK1 and FAC1 genes that encode a catalytic subunit of PKA and the ade-nylate cyclase, respectively. Defects in radial growth and macroconidiation were observed in both the cpk1 and fac1 deletion mutants. The fac1 mutant also was significantly reduced in virulence and microconidiation but increased in tolerance to heat and oxidative stresses. These phenotypes were not observed in the cpk1 mutant, indicating that addi-tional catalytic subunit of PKA must exist and function downstream from FAC1. The fac1 mutant formed microco-nidia mainly in false heads. The expression levels of the hydrophobin genes HYD1 and HYD2, which are known to be associated with change in formation of microconidia, were significantly reduced in the fac1 mutant. Expression of F. verticillioides GSY2 and HSP26 genes, two other puta-tive downstream targets of FAC1, was increased in the fac1 mutant and may be associated with its enhanced stress tol-erance. Although fumonisin production was normal, bio-synthesis of bikaverin was increased in the fac1 mutant, suggesting that FAC1 and cAMP signaling may have path-way- or metabolite-specific regulatory roles in secondary metabolism. Overall, the pleiotropic defects of the fac1 de-letion mutant indicate that the cAMP-PKA pathway is involved in growth, conidiation, bikaverin production, and plant infection in F. verticillioides. © 2010 The American Phytopathological Society.

Caron J.-B.,Royal Ontario Museum | Morris S.C.,University of Cambridge | Shu D.,Northwest University, China
PLoS ONE | Year: 2010

Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian) Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian), form a distinctive clade (herein the cambroernids). Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts), we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles. Copyright: © 2010 Caron et al.

Chen W.,Northwest University, China | Sun S.,Johns Hopkins University | Li Z.,Northwest University, China
PLoS ONE | Year: 2012

Increasing numbers of H5N1 influenza viruses (IVs) are responsible for human deaths, especially in North Africa and Southeast Asian. The binding of hemagglutinin (HA) on the viral surface to host sialic acid (SA) receptors is a requisite step in the infection process. Phylogenetic analysis reveals that H5N1 viruses can be divided into 10 clades based on their HA sequences, with most human IVs centered from clade 1 and clade 2.1 to clade 2.3. Protein sequence alignment in various clades indicates the high conservation in the receptor-binding domains (RBDs) is essential for binding with the SA receptor. Two glycosylation sites, 158N and 169N, also participate in receptor recognition. In the present work, we attempted to construct a serial H5N1 HA models including diverse glycosylated HAs to simulate the binding process with various SA receptors in silico. As the SA-α-2,3-Gal and SA-α-2,6-Gal receptor adopted two distinctive topologies, straight and fishhook-like, respectively, the presence of N-glycans at 158N would decrease the affinity of HA for all of the receptors, particularly SA-α-2,6-Gal analogs. The steric clashes of the huge glycans shown at another glycosylation site, 169N, located on an adjacent HA monomer, would be more effective in preventing the binding of SA-α-2,3-Gal analogs. © 2012 Chen et al.

Wang J.,Xi'an Jiaotong University | Wu S.,Xi'an Jiaotong University | Ren W.,Northwest University, China
Applied Optics | Year: 2014

A fiber-optics reflection probe based on fiber Fabry-Perot interference (FFPI) is proposed and experimentally demonstrated. The sensing structure comprises an epoxy resin (ER)-based cap on the end-face of the single-mode fiber. A well-defined interference spectrum is obtained by the reflective beams of two surfaces of the ER cap. The simultaneous measurements, including fringe contrast-referenced for the surrounding refractive index (SRI) and wavelength-referenced for temperature, have been achieved via selective interference dips monitoring. Experimental results indicate that the proposed FFPI presents an SRI sensitivity of 57.69 dB/RIU in the measurement range of 1.33-1.40 RIU and a temperature sensitivity of 0.98 pm · μm-1 · °C-1 with per unit cavity length in the range of 30°C-70°C. The proposed sensor has advantages of being compact and robust, making it an alternative candidate as a smart sensor in chemical and biological applications. © 2014 Optical Society of America.

Chen W.,Northwest University, China | Zhong Y.,Northwest University, China | Qin Y.,Northwest University, China | Sun S.,Johns Hopkins University | Li Z.,Northwest University, China
PLoS ONE | Year: 2012

Two glycoproteins, hemagglutinin (HA) and neuraminidase (NA), on the surface of influenza viruses play crucial roles in transfaunation, membrane fusion and the release of progeny virions. To explore the distribution of N-glycosylation sites (glycosites) in these two glycoproteins, we collected and aligned the amino acid sequences of all the HA and NA subtypes. Two glycosites were located at HA0 cleavage sites and fusion peptides and were strikingly conserved in all HA subtypes, while the remaining glycosites were unique to their subtypes. Two to four conserved glycosites were found in the stalk domain of NA, but these are affected by the deletion of specific stalk domain sequences. Another highly conserved glycosite appeared at the top center of tetrameric global domain, while the others glycosites were distributed around the global domain. Here we present a detailed investigation of the distribution and the evolutionary pattern of the glycosites in the envelope glycoproteins of IVs, and further focus on the H5N1 virus and conclude that the glycosites in H5N1 have become more complicated in HA and less influential in NA in the last five years. © 2012 Chen et al.

Zhao G.,University of Hong Kong | Cawood P.A.,University of St. Andrews | Li S.,Ocean University of China | Wilde S.A.,Curtin University Australia | And 4 more authors.
Precambrian Research | Year: 2012

Geological and geophysical data indicate that the Precambrian basement of the North China Craton (NCC) formed by amalgamation of a number of micro-continental blocks. The number of blocks, when they existed and how they came together are controversial, and in particular the following issues are disputed: (1) the timing of collisional event(s) leading to the amalgamation of the Eastern and Western blocks along the Trans-North China Orogen (TNCO); (2) the polarity of the subduction between the Eastern and Western blocks; (3) the validity of an old continental block (Fuping Block) that collided with the Eastern Block at ~2.1Ga; (4) the tectonic setting of the northern margin of the NCC in the Paleoproterozoic; (5) the tectonic nature of high-pressure (HP) and ultrahigh temperature (UHT) granulite-facies events in the Khondalite Belt of the Western Block; and (6) the tectonic setting of the Paleoproterozoic Jiao-Liao-Ji Belt in the Eastern Block.Analysis and integration of available stratigraphic, structural, geochemical, metamorphic and geochronologic data enable the development of an internally consistent and coherent model for assembly and stabilization of the various Archean blocks of the NCC in the Paleoproterozoic. All metamorphic ages obtained for the TNCO are around 1.85Ga, which establishes that the final amalgamation of the Western and Eastern blocks of the craton occurred at ~1.85Ga. The TNCO is characterized by a fan-shaped pattern of structural features, with the top-to-the-NW and top-to-the-SE thrusting in the northwest and southeast, respectively. This pattern does not constrain subduction polarity for the collisional assembly of the Eastern and Western blocks. Structures in lithospheric mantle and asthenosphere in the TNCO have been significantly modified/replaced in the Mesozoic and Cenozoic, and hence the present-day orientation of these structures, even if they relate to Paleoproterozoic assembly of the craton cannot be used to infer associated subduction polarity. There are no unique structural data or available metamorphic data to supporting the existence of an old continental block that intervened between the Eastern and Western Blocks, which collided with the Eastern Block at ~2.1Ga. Available data are also inconsistent with the existence of the Paleoproterozoic Inner Mongolia-North Hebei Orogen along the northern margin of the NCC that formed through accretion of an exotic arc at ~2.3Ga and incorporated into the Paleoproterozoic Columbia (Nuna) Supercontinent at 1.92-1.85Ga. We interpret the north Hebei portion of this inferred orogen as part of the TNCO, and the Inner Mongolian portion as an independent continental block (Yinshan Block). This block is separated from the Ordos Block by the Paleoproterozoic Khondalite Belt. The high-/medium-pressure granulite facies metamorphic event in the Khondalite Belt is considered to have resulted from collision between the Yinshan and Ordos blocks to form the Western Block at ~1.95Ga, whereas the ~1.92Ga UHT metamorphism within the belt was related to the underplating or intrusion of mantle-derived magmas during the post-collisional extension. The Jiao-Liao-Ji Belt in the Eastern Block likely formed through Paleoproterozoic rifting to form the Longgang and Langrim blocks, and subsequent basin closure and collision in the period 2.2-1.9Ga. © 2012 Elsevier B.V..

Jiang D.,University of Western Ontario | Jiang D.,Northwest University, China
Journal of Structural Geology | Year: 2014

Earth's lithosphere is made of rheologically heterogeneous elements of a wide range of characteristic lengths. A micromechanics-based self-consistent MultiOrder Power-Law Approach is presented to account for lithospheric deformations and the accompanying multiscale fabric development. The approach is principally based on the extended Eshelby theory for the motion of a power-law viscous ellipsoid in a power-law viscous matrix and the idea of embedding inhomogeneities within inhomogeneities. The extended theory provides a general means for investigating deformation partitioning in heterogeneous rocks. The "inhomogeneities within inhomogeneities" method allows multi-hierarchical levels of flow field partitioning and hence multiscale deformations to be investigated. Partitioned flow fields are used to investigate fabric development. Being based fully on micromechanics, the approach generates model predictions of both kinematic quantities (strain, strain rates, and vorticity) and stress histories. The former can be directly compared with field and laboratory structural observations while the latter can help to understand the physics of natural deformations.The self-consistent and multiscale approach is applied to a natural example of the Cascade Lake shear zone in the east Sierra Nevada of California. The modeling shows that the fabrics are most consistent with a steeply-dipping transpression zone with a convergence angle of 20° and a strike-slip displacement about 26km. Further, the strength evolution of the model zone confirms that a transpression zone is a weakening system with respect to the simple shearing component and a hardening one for the pure-shearing component. This is consistent with slip partitioning in obliquely convergent plate boundaries: boundary-normal convergence tends to spread over a broad area whereas boundary-parallel shear tends to localize in major strike-slip zones. © 2014 Elsevier Ltd.

Wei D.,Zhengzhou University | Wei D.,University of Kentucky | Lei B.,Northwest University, China | Lei B.,University of Kentucky | And 2 more authors.
Journal of the American Chemical Society | Year: 2012

First-principles quantum mechanical/molecular mechanical free energy calculations have been performed to provide the first detailed computational study on the possible mechanisms for reaction of proteasome with a representative peptide inhibitor, Epoxomicin (EPX). The calculated results reveal that the most favorable reaction pathway consists of five steps. The first is a proton transfer process, activating Thr1-O γ directly by Thr1-N z to form a zwitterionic intermediate. The next step is nucleophilic attack on the carbonyl carbon of EPX by the negatively charged Thr1-O γ atom, followed by a proton transfer from Thr1-N z to the carbonyl oxygen of EPX (third step). Then, Thr1-N z attacks on the carbon of the epoxide group of EPX, accompanied by the epoxide ring-opening (S N2 nucleophilic substitution) such that a zwitterionic morpholino ring is formed between residue Thr1 and EPX. Finally, the product of morpholino ring is generated via another proton transfer. Noteworthy, Thr1-O γ can be activated directly by Thr1-N z to form the zwitterionic intermediate (with a free energy barrier of only 9.9 kcal/mol), and water cannot assist the rate-determining step, which is remarkably different from the previous perception that a water molecule should mediate the activation process. The fourth reaction step has the highest free energy barrier (23.6 kcal/mol) which is reasonably close to the activation free energy (∼21-22 kcal/mol) derived from experimental kinetic data. The obtained novel mechanistic insights should be valuable for not only future rational design of more efficient proteasome inhibitors but also understanding the general reaction mechanism of proteasome with a peptide or protein. © 2012 American Chemical Society.

Yang G.-P.,Northwest University, China | Hou L.,Northwest University, China | Ma L.-F.,Northwest University, China | Ma L.-F.,Luoyang Normal University | Wang Y.-Y.,Northwest University, China
CrystEngComm | Year: 2013

Metal-organic frameworks (MOFs) have become a rapidly expanding research topic in the fields of synthetic chemistry and materials science in recent years. Entanglement is often considered to be an important phenomenon in MOFs. Currently, a large number of entangled metal-organic frameworks (EMOFs) have been yielded and documented well in the literature. The structure-property relationships of an EMOF can be directed and fine-tuned not only by the starting materials, i.e. metal ions/clusters and organic ligands, but also by the various reaction conditions, including reaction temperature, pH value, and molar ratio of reactants etc. In this highlight, we carefully attempt to analyze and summarize the key factors which significantly influence the formation of EMOFs, and we hope this work may provide some primary guide information to the predesign and construction of desired EMOFs. © 2013 The Royal Society of Chemistry.

Li Y.,Northwest University, China | Li Y.,University of Delaware | Hsieh W.-P.,University of Delaware | Mahmudov R.,University of Delaware | And 2 more authors.
Journal of Hazardous Materials | Year: 2013

A wastewater collected from a regional ammunition process site was treated with combined US-Fenton process. Factors such as pH, temperature, reaction time, US energy intensity, initial TOC concentration, and the molar ratio of iron to hydrogen peroxide that might affect the treatment efficiency were investigated. The removal of TOC, COD, and color increased with decreasing pH and increasing temperature and US intensity. Color was removed rapidly reaching 85% in 10min; whereas TOC and COD were removed slowly, only about 20% for both in 10min and approaching 65 and 92% removal in 120min, respectively. The optimal molar ratio of Fe(II) to H2O2 for TOC and COD removal was 500. The results showed that the change in the average carbon oxidation number (ACON) was parallel to that of the removal efficiency of TOC, COD, and color. The toxicity of treated wastewater was reduced as assessed by the respiration rate of Escherichia coli. © 2012.

Wu M.,University of Hong Kong | Zhao G.,University of Hong Kong | Sun M.,University of Hong Kong | Li S.,Ocean University of China | And 2 more authors.
Lithos | Year: 2013

As an important component of the Western Shandong Complex in the Eastern Block of the North China Craton, the Yishui Terrane consists of Neoarchean high-grade supracrustal rocks, granitoid gneisses and charnockites. LA-ICP-MS zircon UPb dating and Hf isotopic analyses on these lithologies have been carried out and the results provide new insights into the Neoarchean crustal evolution of the Eastern Block of the North China Craton. New zircon dating results reveal that the magmatic precursors of the supracrustal metapelites and granitoid gneisses were generated at 2.54-2.53Ga and 2.57-2.55Ga, respectively, and the charnockites were emplaced contemporaneously around 2.56-2.53Ga. Single metamorphic zircon grains and overgrowth rims from these rocks document consistent metamorphic ages at ~2.50Ga, suggesting that the Yishui Terrane experienced a high-grade metamorphic event at the end of the Neoarchean. Detrital zircons from pelitic gneisses yield 207Pb/206Pb ages of 2.89-2.65Ga, with a major age peak at ~2.53Ga and a subordinate age peak at ~2.70Ga, implying that the sedimentary protoliths of the pelitic gneisses may have been sourced from ~2.53Ga rocks in the Yishui Terrane and ~2.70Ga rocks in the adjacent Luxi Granite-Greenstone Terrane. Hf isotopic compositions show that the Neoarchean magmatic zircons have positive εHf(t) values ranging from +1.4 to +7.8 and depleted mantle model ages of 2.92-2.60Ga with a prominent peak at 2.8-2.7Ga, suggesting that the Neoarchean crust was derived mainly from juvenile sources and partly from the recycling of old continental crust in the Yishui area. Combined with previous data from the adjacent Luxi Granite-Greenstone Terrane and other complexes in the Eastern Block, it is concluded that the Neoarchean was an important period of crust accretion in the Eastern Block of the North China Craton. © 2013 Elsevier B.V.

Liu C.,University of Hong Kong | Zhao G.,University of Hong Kong | Sun M.,University of Hong Kong | Zhang J.,University of Hong Kong | And 2 more authors.
Precambrian Research | Year: 2012

The Dengfeng, Taihua and Zhongtiao Complexes are located in the southernmost segment of the Trans-North China Orogen, along which the Western and Eastern Blocks amalgamated to form the North China Craton. The Dengfeng Complex consists of the Neoarchean granitoids and supracrustal rocks, of which the latter are subdivided into the Dengfeng and Songshan Groups. The Songshan Group consists of basal conglomerates, quartzites, schists with minor dolomites and phyllites. Geochemistry of the Songshan schists and quartzites are indicative of felsic source rocks and display continental island arc and passive continental margin signatures, respectively. U-Pb ages of detrital zircons from the Songshan Group yielded three age populations of 3700-3100. Ma, 3000-2550. Ma and 2550-1950. Ma. The dominant 3000-2550. Ma detrital zircons were most likely sourced from the TTG gneisses of the Dengfeng and Taihua Complexes. The subordinate 2550-1950. Ma detrital zircons were probably derived from the Paleoproterozoic granitoid plutons and meta-rhyolites in the Dengfeng and Zhongtiao Complexes, and minor amounts of 3700-3100. Ma detrital zircons may have been derived from the Paleoarchean and Mesoarchean crust of the Eastern Block. The youngest detrital zircon age peaks in the Luohandong and Wuzhiling Formations constrain their maximum depositional ages at ~2350. Ma and ~1960. Ma, respectively. In combination with the 1775. Ma undeformed granitoids that cut the Songshan Group, the depositional age of the Songshan Group can be constrained in the period between ~2350 and ~1780. Ma. Considering the lithostratigraphic feature, provenance and depositional age, the Songshan Group is interpreted as having deposited in a retroarc foreland basin, which is consistent with the model that the collision between the Eastern and Western Blocks to form the Trans-North China Orogen occurred at ~1.85. Ga after long-lived subduction. © 2011 Elsevier B.V.

Chuang C.,University of Kentucky | Barajas D.,University of Kentucky | Qin J.,University of Kentucky | Qin J.,Northwest University, China | Nagy P.D.,University of Kentucky
PLoS Pathogens | Year: 2014

RNA viruses take advantage of cellular resources, such as membranes and lipids, to assemble viral replicase complexes (VRCs) that drive viral replication. The host lipins(phosphatidate phosphatases) are particularly interesting because these proteins play key roles in cellular decisions about membrane biogenesis versus lipid storage. Therefore, we examined the relationship between host lipins and tombusviruses, based on yeast model host. We show that deletion of PAH1 (phosphatidic acid phosphohydrolase), which is the single yeast homolog of the lipin gene family of phosphatidate phosphatases, whose inactivation is responsible for proliferation and expansion of the endoplasmic reticulum (ER) membrane, facilitates robust RNA virus replication in yeast. We document increased tombusvirus replicase activity in pah1Δ yeast due to the efficient assembly of VRCs. We show that the ER membranes generated in pah1Δ yeast is efficiently subverted by this RNA virus, thus emphasizing the connection between host lipins and RNA viruses. Thus, instead of utilizing the peroxisomal membranes as observed in wt yeast and plants, TBSV readily switches to the vastly expanded ER membranes in lipin-deficient cells to build VRCs and support increased level of viral replication. Over-expression of the Arabidopsis Pah2p in Nicotiana benthamiana decreased tombusvirus accumulation, validating that our findings are also relevant in a plant host. Over-expression of AtPah2p also inhibited the ER-based replication of another plant RNA virus, suggesting that the role of lipins in RNA virus replication might include several more eukaryotic viruses. © 2014 Chuang et al.

Fu L.B.,CAS Beijing Institute of Applied Physics And Computational Mathematics | Fu L.B.,Beijing University of Technology | Xin G.G.,Beijing Institute of Technology | Xin G.G.,Northwest University, China | And 4 more authors.
Physical Review Letters | Year: 2012

A semiclassical quasistatic model is used to investigate the recollision dynamics in circularly polarized laser fields. A velocity window for recollision to occur is found. Only when the return electron's orbits are irregular does significant double ionization take place. The model reproduces the experimental results for magnesium and explains the apparently conflicting experimental results in terms of an analytical formula that demarcates the phase diagram for the nonsequential double ionization in circularly polarized laser fields. © 2012 American Physical Society.

Butler J.E.,University of Iowa | Wertz N.,University of Iowa | Sun X.,Northwest University, China
Molecular Immunology | Year: 2013

Kappa transcripts from fetal piglets were compared to the recently reported kappa genome. Although five IGKV gene families are present in the genome, only IGKV1 and IGKV2 family genes are transcribed; the latter comprises >95% of the repertoire, in which two genes account for ~80%. We provisionally identified a new sequence allele of IGKV2-10 and two new IGKV genes that were not present in the genome of a single Duroc sow. One of these (IGKV2-1) accounted for 39% of the total pre-immune repertoire. The discovery of new IGKV genes and alleles in only 90 transcripts from mixed breeds, suggests considerable polymorphism and polygeny in the kappa locus of swine. Similar to lambda rearrangements, CDR3 length and diversity is restricted. The somatic mutation frequency is low and accumulates in especially CDR1.This transcriptional analysis of the pre-immune kappa repertoire completes a comparative study of all three Ig loci which has allowed the potential and actual combinatorial repertoire to be determined. Calculations show that combinatorial diversity in all three loci contribute comparatively little to the swine pre-immune antibody repertoire. Compared to humans that can potentially generate a million binding site variants, only 16-48 variant comprise 70% of the swine repertoire and 224 account for 95-100%. The frequency of somatic mutation does not differ among rearrangements from all three loci and the CDR3 diversity index shows that swine overwhelmingly generate their pre-immune repertoire by junctional diversity in heavy chain rearrangements. © 2013 Elsevier Ltd.

Lin J.-Y.,University of Kentucky | Mendu V.,University of Kentucky | Pogany J.,University of Kentucky | Qin J.,University of Kentucky | And 2 more authors.
PLoS Pathogens | Year: 2012

Replication of plus-stranded RNA viruses is greatly affected by numerous host-coded proteins acting either as susceptibility or resistance factors. Previous genome-wide screens and global proteomics approaches with Tomato bushy stunt tombusvirus (TBSV) in a yeast model host revealed the involvement of cyclophilins, which are a large family of host prolyl isomerases, in TBSV replication. In this paper, we identified those members of the large cyclophilin family that interacted with the viral replication proteins and inhibited TBSV replication. Further characterization of the most effective cyclophilin, the Cyp40-like Cpr7p, revealed that it strongly inhibits many steps during TBSV replication in a cell-free replication assay. These steps include viral RNA recruitment inhibited via binding of Cpr7p to the RNA-binding region of the viral replication protein; the assembly of the viral replicase complex and viral RNA synthesis. Since the TPR (tetratricopeptide repeats) domain, but not the catalytic domain of Cpr7p is needed for the inhibitory effect on TBSV replication, it seems that the chaperone activity of Cpr7p provides the negative regulatory function. We also show that three Cyp40-like proteins from plants can inhibit TBSV replication in vitro and Cpr7p is also effective against Nodamura virus, an insect pathogen. Overall, the current work revealed a role for Cyp40-like proteins and their TPR domains as regulators of RNA virus replication. © 2012 Lin et al.

Wu M.,University of Hong Kong | Zhao G.,University of Hong Kong | Sun M.,University of Hong Kong | Li S.,Ocean University of China | And 4 more authors.
Lithos | Year: 2014

The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U-Pb and Lu-Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U-Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~2.9Ga, ~2.7Ga and ~2.5Ga. Metamorphic zircon U-Pb data obtained for these rocks show distinct metamorphic ages at ~2.50 and ~1.9-1.8Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao-Liao-Ji Belt. Magmatic zircons have variable εHf(t) values from -5.5 to +7.7 with model ages of 3.92-2.57Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4-3.1Ga and a subordinate peak at 2.8-2.7Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4-3.1Ga and 2.8-2.7Ga, and a crustal reworking event with minor juvenile additions at ~2.5Ga in the Jiaodong Terrane.© 2013 Elsevier B.V.

Wu B.,Northwest University, China | Jia C.,CAS Lanzhou Institute of Chemical Physics | Wang X.,CAS Lanzhou Institute of Chemical Physics | Li S.,CAS Lanzhou Institute of Chemical Physics | And 2 more authors.
Organic Letters | Year: 2012

A series of acyclic oligourea receptors which closely resemble the scaffolds and coordination behavior of oligopyridines have been synthesized. Assembly of the receptors with chloride ions afforded mononuclear anion complexes or dinuclear foldamers depending on the number of the urea groups. © 2012 American Chemical Society.

Wu M.,University of Hong Kong | Zhao G.,University of Hong Kong | Sun M.,University of Hong Kong | Bao Z.,Northwest University, China | And 2 more authors.
Geological Magazine | Year: 2014

The Archaean Jiaodong Terrane is located in the southern segment of the Palaeoproterozoic Jiao-Liao-Ji Belt, which separates the Eastern Block of the North China Craton into the Longgang and Langrim blocks. Controversy has long surrounded the issue of whether the Jiaodong Terrane is part of the North China Craton or an exotic terrane. This study presents new zircon U-Pb ages for the major lithologies of the Jiaodong Terrane, and the results indicate that the terrane underwent two main magmatic events at ~2.89 Ga and 2.62-2.56 Ga and two metamorphic events at ~2.5 Ga and 1.9-1.8 Ga. These ages are consistent with those of other metamorphic complexes in the Eastern Block, suggesting that the Jiaodong Terrane was part of the Neoarchaean basement of the Eastern Block, which was reworked at 1.9-1.8 Ga in association with the development of the Palaeoproterozoic Jiao-Liao-Ji Belt. © Cambridge University Press 2013.

Zhao Y.-Y.,Northwest University, China | Cheng X.-L.,National Institutes for Food and Drug Control | Wei F.,National Institutes for Food and Drug Control | Bai X.,Waters Technologies Shanghai Ltd. | And 3 more authors.
Journal of Proteome Research | Year: 2013

Chronic kidney disease (CKD) is becoming a worldwide public health problem. In this study, a kidney metabonomics method based on the ultra performance liquid chromatography/high-sensitivity mass spectrometry with MSE data collection technique was undertaken to explore the excretion pattern of low molecular mass metabolites in rat model of adenine-induced chronic renal failure (CRF). Coupled with blood biochemistry and kidney histopathology results, the significant difference in metabolic profiling between the adenine-induced CRF group and the control group by using pattern recognition analysis indicated that changes in global tissue metabolites were occurred. Some significantly changed metabolites like fatty acids, p-cresol sulfate, and indoxyl sulfate have been identified. The results showed that the most important CRF-related metabolites were polyunsaturated fatty acids, indoxyl sulfate, and p-cresyl sulfate. Indoxyl sulfate and p-cresyl sulfate (uremic toxins) were significantly increased in CRF rats. Indoxyl sulfate and p-cresyl sulfate stimulate progressive tubulointerstitial fibrosis by increasing the expression of transforming growth factor-β1 (TGF-β1). These biochemical changes in tissue metabolites are related to the perturbations of fatty acid metabolism and amino metabolism, which may be helpful to further understand the TGF-β1 mechanisms of tubulointerstitial fibrosis. This work shows that the metabonomics method is a valuable tool for studying the essence of CKD. © 2012 American Chemical Society.

He Y.,University of Hong Kong | He Y.,Northwest University, China | Zhao G.,University of Hong Kong | Sun M.,University of Hong Kong
Journal of Geology | Year: 2010

The Xiong'er volcanic rocks constitute a large Paleo-Mesoproterozoic volcanic belt along the southern margin of the North China Craton. The volcanic rocks can be petrographically and geochemically classified into the basaltic andesite- andesite and dacite-rhyolite series, with the former being the dominant component of the Xiong'er volcanic rocks. The volcanic rocks of the dacite-rhyolite series have been derived from the wet and low-temperature differentiation of the basaltic andesite-andesite series at shallow depth, suggested by regional geological, lithological, and geochemical studies. In addition, crustal assimilation was involved in the magmas to form volcanic rocks of the dacite-rhyolite series, as suggested by low εNd(t) values (-8.09 to ̃-9.99) and high Th/Yb ratios (1.7-2.7). Some of volcanic rocks from the basaltic andesite-andesite series show features of high-Mg andesites (HMA), being characterized by high MgO contents and Mg numbers, representing the most primitive end-member of the magmatic series in the Xiong'er volcanic rocks, whereas other volcanic rocks of the basaltic andesite-andesite series (low-magnesium andesites) can be assigned to evolved andesites because of their low MgO and relatively high SiO2 contents. In the crystallization sequence of Opx → Cpx → Pl from the HMAs, through low-magnesium andesites, to dacite-rhyolite series, inferred by the covariation of major and trace elements, the early crystallization of plagioclases could have been suppressed as a result of high water content. The Xiong'er volcanic rocks are characterized by arclike geochemical signatures (large ion lithophile element and light rare earth element enrichments and negative Ta-Nb-Ti anomalies) as well as remarkably high Fe-Ti and high field strength element concentrations. These features can be interpreted in terms of the subduction-related hydrous melting of a mantle that experienced siliceous melt-metasomatismduring the Archean-Paleoproterozoic hot subduction in the Trans-North China Orogen. Thus, we interpret the Xiong'er volcanic rocks to have formed at an active continental margin. This implies that the North China Craton, like other continental components (e.g., North America, Greenland, Baltica, Amazonia, and other cratons) of the Columbia supercontinent, also underwent a subduction-related outgrowth along its southern margin during Paleo-Mesoproterozoic time. © 2010 by The University of Chicago. All rights reserved.

Jing G.,Northwest University, China | Jing G.,NanoBiophotonics Center | Ma J.,Northwest University, China
Journal of Physical Chemistry B | Year: 2012

Curved cracks widely exist in nanoparticle (NP) deposition produced by drying colloidal suspension. Circular cracks, for example, initiate and propagate along a circular trajectory. One feasible theoretical explanation of a circular crack is the Xia-Hutchinson model, in which a preexisting track (flaw loop) in the film is necessary for initiating and propagating the crack on the circular path. Here, we report the first experimental evidence of dried deposition to support this model. Our results indicate that cracks along the circular trajectory can surprisingly "pass" across a 180 μm air gap. Moreover, two arc-path cracks originate in different areas and propagate to meet, forming a circular trajectory. These unexpected crack initiation and propagation indicate that the crack propagates alone the "preformed" track, experimentally confirming the hypothesis proposed by the Xia-Hutchinson model. The transition of the circular crack to a radial one indicates that the deposition microstructure is the dominant factor for the crack formation. © 2012 American Chemical Society.

Chen B.,Northwest University, China | Diao Z.-J.,China University of Mining and Technology | Lu H.-Y.,China National Institute of Clean and Low Carbon Energy
Fuel | Year: 2014

The aim of this work is the investigation of the detailed mechanisms for the initiation reaction leading to the spontaneous combustion of lignite. To carry this out we have used the ReaxFF reactive force field to perform a series of molecular dynamics (MD) simulations on a unimolecular model compound. The initiation reaction observed in the ReaxFF MD simulations involves hydrogen abstraction from phenolic hydroxyl groups by O2 followed by the formation of HO2. The main products observed in our simulations include H2O2, H2O, CH2O, and CO 2. In addition, hydrogen abstraction reactions are responsible for the formation of H2O2 and H2O. The reaction products and the mechanisms involved in the initial stage of spontaneous combustion are consistent with previous results. The agreement of these results with available experimental observations demonstrates that ReaxFF MD simulations can provide an atomistic description of the initiation mechanism for spontaneous combustion and provide useful insights into the complicated reaction processes involved. © 2013 Elsevier Ltd. All rights reserved.

Sun C.-Y.,Northwest University, China | Song Y.,Northwest University, China | Yue R.-H.,Ningbo University
European Physical Journal C | Year: 2013

It was found that the model with interaction between cold dark matter (CDM) and dark energy (DE) proportional to the energy density of CDM ρm and constant equation of state of DE wd suffered from instabilities of the density perturbations on the super-Hubble scales. Here we suggest a new covariant model for the energy-momentum transfer between CDM and DE. Then using the covariant model, we analyze the evolution of density perturbations on the super-Hubble scale. We find that the instabilities can be avoided in the model with constant wd and interaction proportional to ρm. Furthermore, we analyze the dominant non-adiabatic mode in the radiation era and find that the mode grows regularly. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Kang Y.,Northwest University, China | Luczaj L.J.,University of Rzeszow | Ye S.,ul. Skargi 11 m 70
Genetic Resources and Crop Evolution | Year: 2012

Aconitum spp. are highly toxic due to the presence of aconitine-type alkaloids. Aconitum carmichaelii Debeaux is one of the most important and most studied Chinese medicines. However the scientific literature contains only anecdotal references to the use of A. carmichaelii as a food plant. The aim of the study was to document the traditional alimentary use of the species. Fifty people from three adjacent villages on Mount Taibai of the Qinling range (Shaanxi) were interviewed about the local use of the Aconitum. Most of them eat it on a regular basis every winter. The plant is widely cultivated in the area for food and nearly every family grows it. The tubers are cooked a few times during winter. Usually around 5 kg are prepared at one time and boiled, adding water four times, each time for at least 2 h, over a high flame. People usually eat one bowl a day (ca. 200 g). Respondents claim they eat them for two reasons: they heat the body in winter (they are "hot by nature") and they are nourishing like other staples. © 2012 Springer Science+Business Media Dordrecht.

Cortijo I.,University of Extremadura | Cai Y.,Northwest University, China | Hua H.,Northwest University, China | Schiffbauer J.D.,University of Missouri | Xiao S.,Virginia Polytechnic Institute and State University
Gondwana Research | Year: 2015

Cloudina is the best-known biomineralizing metazoan and a potential index fossil in the late Ediacaran Period, yet many aspects of its biology remain poorly understood. Previous reports have shown that Cloudina tubes grow from a basally closed funnel (or apical element), with occasional dichotomous branching. New material from the Ediacaran Beiwan Member of the Dengying Formation, South China, includes two distinct morphotypes-tubes with rounded versus pointed conical apices. In branching specimens, one of the daughter branches tends to have a conical apex. It is hypothesized that cloudinids with a spherical apex were derived from sexual reproduction, with their spherical termination representing the embryonic shell, whereas those with a conical apex are daughter branches detached from their parent tubes through asexual reproduction. These interpretations imply that Cloudina could reproduce both sexually and asexually, producing spherical embryonic shells and conical propagules, respectively. This strategy may have served to enhance dispersal, which was critical for the ecological success of early gregarious and sedentary animals such as Cloudina. © 2014 International Association for Gondwana Research.

Qi H.,Northwest University, China | Wang F.-B.,Northwest University, China | Deng H.,Microwise System Company Ltd
Wuli Xuebao/Acta Physica Sinica