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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.

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.

Galvez D.A.,University of Alberta | Galvez D.A.,University of British Columbia | Landhausser S.M.,University of Alberta | Tyree M.T.,Northwest University, China
New Phytologist | Year: 2013

Climate models suggest that more frequent drought events of greater severity and length, associated with climate change, can be expected in the coming decades. Although drought-induced tree mortality has been recognized as an important factor modulating forest demography at the global scale, the mechanisms underlying drought-induced tree mortality remain contentious. Above- and below-ground growth, gas exchange, water relations and carbon reserve accumulation dynamics at the organ and whole-plant scale were quantified in Populus tremuloides and P. balsamifera seedlings in response to severe drought. Seedlings were maintained in drought conditions over one growing and one dormant winter season. Our experiment presents a detailed description of the effect of severe drought on growth and physiological variables, leading to seedling mortality after an extended period of drought and dormancy. After re-watering following the dormant period, drought-exposed seedlings did not re-flush, showing that the root system had died off. The results of this study suggest a complex series of physiological feedbacks between the measured variables in both Populus species. Further, they reveal that reduced reserve accumulation in the root system during drought decreases the conversion of starch to soluble sugars in roots, which may contribute to the root death of drought-exposed seedlings during the dormant season by compromising the frost tolerance of the root system. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Ji L.,Northwest University, China | Ji L.,Henan Agricultural University
Physica A: Statistical Mechanics and its Applications | Year: 2010

The second-order conditional LieBcklund symmetries of nonlinear diffusion equations with variable coefficients are studied. A number of examples are considered and some exact solutions are constructed via the compatibility of conditional LieBcklund symmetries and the governing equations. These solutions possess the extended forms of the separation of variables, including the extensions of the instantaneous source solutions of the porous medium equations. © 2010 Elsevier B.V. All rights reserved.

Song L.,Xian University of Arts and Science | Gao J.,Northwest University, China | Li J.,Xian University of Arts and Science
Journal of Luminescence | Year: 2014

A facile route has been established for the synthesis of PVP/CaF 2: RE3+ and PVP/CaF2: Ce3+ nanoparticles (RE=Eu, Tb, Ce/Tb; PVP=Poly(N-vinyl-2-pyrrolidone)) heated at 70 C in ethanol at ambient pressure. The as-prepared nanoparticles were shown to be well dispersed in water. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation of fluorescence properties showed that there exists energy transfer from the surface coating of PVP to Eu3+ and Tb3+ leading to the sensitized fluorescence emission of Eu3+ and Tb3+. Co-doping the PVP/CaF2: Tb3+ nanoparticles with Ce3+ results in significant increase in the emission intensity of Tb3+ and this has been attributed to the sensitization of Ce3+ and PVP on Tb 3+. © 2014 Elsevier B.V.

Wang G.,Illinois Institute of Technology | Zhao Q.,University of Texas at Arlington | Kang X.,Northwest University, China | Guan X.,Illinois Institute of Technology
Journal of Physical Chemistry B | Year: 2013

In this work, DNA-Hg(II) interactions were investigated by monitoring the translocation of DNA hairpins in a protein ion channel in the absence and presence of metal ions. Our experiments demonstrate that target-specific hairpin structures could be stabilized much more significantly by mercuric ions than by the stem length and the loop size of the hairpin due to the formation of Thymine-Hg(II)-Thymine complexes. In addition, the designed DNA probe allows the development of a highly sensitive nanopore sensor for Hg2+ with a detection limit of 25 nM. Further, the sensor is specific, and other tested metal ions including Pb2+, Cu2+, Cd2+, and so on with concentrations of up to 2 orders of magnitude greater than that of Hg2+ would not interfere with the mercury detection. © 2013 American Chemical Society.

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.

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.

Dickin A.P.,McMaster University | McNutt R.H.,McMaster University | Martin C.,McMaster University | Guo A.,Northwest University, China
Bulletin of the Geological Society of America | Year: 2010

A large Nd isotope data set is presented to generate a crustal formation age map for the southwest Grenville Province, placing it in the context of the province as a whole. Previous studies have shown that most crust in the central and eastern parts of the province is pre-Grenvillian, composed largely of juvenile 1.5, 1.7, 1.9, and 2.7 Ga arc terranes, partly reworked by later ensialic arcs and collision zones. In contrast, new Nd data reported here show that juvenile monocyclic crust is restricted to the SW Grenville Province, in part of the Central Metasedimentary Belt interpreted as a failed backarc rift zone. There is a clear isotopic distinction between this rift zone and the pre-Grenvillian crust on the flanks. On the flanks of the rift zone, there is evidence for two crust-forming events, comprising an earlier (1.5 Ga) juvenile Pinwarian event, and a later 1.4-1.3 Ga continental margin arc (the Elzevirian Orogeny). Based on the geographical distribution of Nd model ages in the SW Grenville Province, a revised tectonic model for the Grenville Orogeny is developed. In this model, backarc spreading created a rift zone behind a (pre-Grenvillian) Elzevirian subduction zone that obliquely straddled the edge of a Mesoproterozoic continental margin. As a result of this geometry, the rift zone died out to the north as it propagated into cold Archean crust. Elzevirian subduction was probably halted by the collision of the continental margin with an offshore arc, and later with a major continental block, giving rise respectively to the Shawinigan and the Ottawan orogenic events. These collisional events can be grouped as parts of the Grenville Orogenic Cycle. © 2010 Geological Society of America.

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.

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.

Redshaw C.,Northwest University, China | Redshaw C.,University of Hull
Dalton Transactions | Year: 2016

This perspective review discusses metallocalix[n]arene complexes that have been employed in either α-olefin polymerization or in the ring opening polymerization (ROP) of cyclic esters over the last 5 years. Synthesis, molecular structure and catalytic potential are discussed. For α-olefin polymerization, systems based on early transition metals in combination with calix[n]arenes (n = 4, 6 or 8), depleted calix[4]arenes or thia/sulfinyl/sulfonyl calix[4]arenes have been reported, and in some cases, are highly active. For the ROP studies, a number of the systems, typically of the early transition metals, only exhibit activity under robust conditions, whereas other systems, for example those of magnesium, demonstrate exceptional activity, immortal behaviour and intriguing stereoselectivity. © 2016 The Royal Society of Chemistry.

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.

Wang L.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Wang L.,Northwest University, China | Wang D.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Dong X.Y.,CAS Suzhou Institute of Nano Technology and Nano Bionics | And 5 more authors.
Chemical Communications | Year: 2011

An innovative strategy of fabricating electrode material by layered assembling two kinds of one-atom-thick sheets, carboxylated graphene oxide (GO) and Co-Al layered double hydroxide nanosheet (Co-Al LDH-NS) for the application as a pseudocapacitor is reported. The Co-Al LDH-NS/GO composite exhibits good energy storage properties. © 2011 The Royal Society of Chemistry.

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.

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.

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 Quebec
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.

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.

Liu B.,Chinese Ministry of Water Resources | Liu B.,University of Chinese Academy of Sciences | Shao M.,Northwest University, China
Journal of Hydrology | Year: 2014

An understanding of the temporal stability of soil water storage (SWS) in deep soil profiles is critical to optimize monitoring strategies and to predict the status of soil water on the Loess Plateau. This study tested and validated the feasibility of estimating mean SWS over multiple years by the SWSs at selected locations. The SWSs in 0-1, 1-2, 2-3, and 3-4. m layers were collected using neutron probes at 11 sites in each of four land-use types: cropland (CL), grassland (GL), fallow land (FL), and shrubland (SL). The most time-stable locations (MTSLs) for the various layers and the location at mid-slope for each land use were selected on 20 sampling occasions during a calibration period from July 2004 to December 2005. A validation data sets from January 2006 to October 2013 was used to test the length of time the estimates of mean SWS remained valid. The SWSs in SL and GL decreased with plant growth, and the temporal variations were larger in SL and GL than in FL and CL. The temporal stability of the SWSs was high for all soil layers in four land uses, with the rank correlations over the threshold of significance (. α=. 0.05) over 10. years. The degree of temporal stability of SWSs was ranked as CL. >. FL. >. GL. >. SL, and the temporal stability of SWSs in SL and GL decreased with increasing lengths of observation period, as indicated by lower mean Spearman's correlations for all soil layers. The MTSLs selected from the calibration period could accurately estimate mean SWSs for diverse layers under four land uses with estimation errors less than 10% over eight years. The study verified that a single location at mid-slope of each land use could be sampled in order to reduce the required number of samples and save time and labor while maintaining a high accuracy of prediction over multiple years. © 2014 .

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.

Jia Y.-H.,ShenYang Agricultural University | Jia Y.-H.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Shao M.-A.,Northwest University, China
Journal of Hydrology | Year: 2014

The limitation of soil water in semiarid regions restricts the formation of a good cover of vegetation. The Loess Plateau in China, well known for its severe soil erosion, has a thick loessial soil that holds substantial volumes of water and provides the basis of a sustainable restoration of vegetation. Our limited understanding of the dynamics of deep soil moisture, however, could lead to the mismanagement of soil-water resources or could even misguide the policies of vegetational reconstruction. To evaluate the temporal response of deep soil moisture in different types of revegetation, we observed soil moisture to a depth of 340. cm in four plots, planted with Korshinsk peashrub (KOP), purple alfalfa (ALF), native plants (natural fallow, NAF), and millet (MIL), on 15 measurement events from 2010 to 2012. Our analysis provided four main conclusions. (1) The quantitative difference of potential evapotranspiration and actual precipitation resulted in natural deficits of soil moisture. The dynamics of deep soil moisture, however, were mainly dominated by the type of vegetation. Deep soils in plots of KOP and ALF became drier than the soil in plots of NAF and MIL. (2) Deep soil moisture in KOP and ALF was weakly variable. Correlations of time series of soil moisture between the upper and lower layers tended not to be significant. Dried soil layer, a special hydrological phenomenon, had formed in the plots. (3) The correlation between variances of soil moisture and the corresponding mean values were not always significantly positive due to the influence of vegetational type, observational depth, and date. (4) Fallow may be the best cover for achieving adequate hydrological sustainability of the soil. These results are expected to help improve the understanding of the response of deep soil moisture to vegetational restoration and to provide insight into the dynamics of deep soil moisture influenced by vegetation on loessial slopes. © 2014 .

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.

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.

Zhao B.,Northwest University, China
Indian Journal of Horticulture | Year: 2014

Rhododendron purdomii Rehd. et Wils is an endemic and important ornamental plant species in China. The effect of temperature (20°C, 30°C and 20°C (16 h) /30°C (8h) and GA3 (0, 200, 400, 600, 800 and 1000 mg/l) on R. purdomii seed germination and early seedling establishment were studied. The results showed that there was little difference among the effects of three temperatures on germination time and germination speed, it significantly affected germination percentage, germination vigour and early seedling growth. High temperature had negative effects on seed germination, and the germination vigour at 20°C were significantly higher than those at two other temperature treatments, germination percentage and germination vigour were the lowest at 30°C; and the survival rate and leaf length of the seedlings at 20°C/30°C were far better than those at two other temperature treatments. Treatment with 600 mgl-1 GA3 for 24 h and 20°C/30°C temperature has a much higher survival rate and growth performance. Therefore, the findings from this study would greatly help the R. purdomii germplasm propagation, conservation and utilization. © 2014, Horticulture Society of India. All rights reserved

Fang Y.,Northwest University, China
IEEE Transactions on Communications | Year: 2012

Low-density parity-check (LDPC) codes have been used to implement lossless distributed or conventional source coding. However, block-wise LDPC codes are difficult to adapt to varying source statistics as traditional symbol-wise entropy coding techniques. In this paper, we propose the sliding-window belief propagation (SWBP) algorithm which is able to simultaneously recover the source and refine the estimate of varying source statistics. The SWBP is easy to implement and performs well in simulations. © 2012 IEEE.

Liu H.,Northwest University, China
Designs, Codes, and Cryptography | Year: 2014

In this paper we give a new family of elliptic curve pseudorandom binary sequences, and study the well-distribution, correlation, linear complexity, collision and avalanche effect of the family of sequences, by using the estimate of exponential sums over elliptic curves. © 2013 Springer Science+Business Media New York.

Fullenkamp D.E.,Northwestern University | Rivera J.G.,Northwestern University | Gong Y.-K.,Northwest University, China | Lau K.H.A.,Northwestern University | And 3 more authors.
Biomaterials | Year: 2012

A silver-releasing antibacterial hydrogel was developed that simultaneously allowed for silver nanoparticle formation and gel curing. Water-soluble polyethylene glycol (PEG) polymers were synthesized that contain reactive catechol moieties, inspired by mussel adhesive proteins, where the catechol containing amino acid 3,4-dihydroxyphenylalanine (DOPA) plays an important role in the ability of the mussel to adhere to almost any surface in an aqueous environment. We utilized silver nitrate to oxidize polymer catechols, leading to covalent cross-linking and hydrogel formation with simultaneous reduction of Ag(I). Silver release was sustained for periods of at least two weeks in PBS solution. Hydrogels were found to inhibit bacterial growth, consistent with the well-known antibacterial properties of silver, while not significantly affecting mammalian cell viability. In addition, thin hydrogel films were found to resist bacterial and mammalian cell attachment, consistent with the antifouling properties of PEG. We believe these materials have a strong potential for antibacterial biomaterial coatings and tissue adhesives, due to the material-independent adhesive properties of catechols. © 2012 Elsevier Ltd.

Song S.,Northwest University, China | Singh V.P.,Texas A&M University
Stochastic Environmental Research and Risk Assessment | Year: 2010

This study aims to model the joint probability distribution of drought duration, severity and inter-arrival time using a trivariate Plackett copula. The drought duration and inter-arrival time each follow the Weibull distribution and the drought severity follows the gamma distribution. Parameters of these univariate distributions are estimated using the method of moments (MOM), maximum likelihood method (MLM), probability weighted moments (PWM), and a genetic algorithm (GA); whereas parameters of the bivariate and trivariate Plackett copulas are estimated using the log-pseudolikelihood function method (LPLF) and GA. Streamflow data from three gaging stations, Zhuangtou, Taian and Tianyang, located in the Wei River basin, China, are employed to test the trivariate Plackett copula. The results show that the Plackett copula is capable of yielding bivariate and trivariate probability distributions of correlated drought variables. © 2010 Springer-Verlag.

Ma R.N.,Northwest University, China
Molekuliarnaia biologiia | Year: 2010

The alpha-lactalbumin (alpha-LA) plays a key role in lactose synthesis in mammary glands of domestic animals. Mutations in the alpha-LA gene are associated with the milk traits in dairy cattle. In our study, a novel SNP: NO_X06366:g.875 C > T was detected in 708 dairy goat individuals--268 of the Xinong Saanen breed and 440 of Guanzhong breed, which revealed a synonymous mutation in the exon 1 of alpha-LA gene. The Polymerase Chain Reaction-Single Strand Conformation Polymorphism (PCR-SSCP) and sequencing techniques showed that there were three genotypes: CC, CT and TT. Moreover, the chi2-test showed that the genotype frequencies of the two breeds were in good agreement with the Hardy-Weinberg equilibrium (P > 0.05). The relationship of the polymorphism of dairy goat alpha-LA gene with the milk trait and the body size trait was revealed. Individuals with the CC genotype were significantly smaller at chest circumference than those with CT (P < 0.05) in both breeds. But the milk trait and other body size traits of the two dairy goat breeds had no significant association with genotypes studied.

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.

Fu J.,Northwest University, China | Wang S.,Huazhong Agricultural University
Frontiers in Plant Science | Year: 2011

The phytohormone auxin has been known to be a regulator of plant growth and development ever since its discovery. Recent studies on plant-pathogen interactions identify auxin as a key character in pathogenesis and plant defense. Like plants, diverse pathogens possess the capacity to synthesize indole-3-acetic acid (IAA), the major form of auxin in plants. The emerging knowledge on auxin-signaling components, auxin metabolic processes, and indole-derived phytoalexins in plant responses to pathogen invasion has provided putative mechanisms of IAA in plant susceptibility and resistance to non-gall- or tumor-inducing pathogens. © 2011 Fu and Wang.

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.

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.

Lai M.-H.,University of Malaya | Gunawardena D.S.,University of Malaya | Lim K.-S.,University of Malaya | Yang H.-Z.,Northwest University, China | Ahmad H.,University of Malaya
Optics Express | Year: 2015

In this work, we have demonstrated for the first time grating regeneration in hydrogenated fibers by direct CO2 laser annealing. During the annealing process, the center wavelength redshifts as the intensity of the focused CO2 laser on the grating is elevated. The reflectivity of the grating begins to decay as the temperature induced in the grating approaches the erasure temperature. The grating is completely erased and regenerated afterwards. The observed spectral results have provided the proof of occurrence of dehydroxylation and stress relaxation in the fiber core during the annealing process. Regenerated gratings with low loss, good temperature sensitivities and sustainability have been successfully developed by this technique. © 2015 Optical Society of America.

Tang M.,University of Wyoming | Xu L.,University of Wyoming | Xu L.,Northwest University, China | Fan M.,University of Wyoming
Applied Energy | Year: 2015

•Partial oxidation of CH4 (POM) possesses advantages over steam reforming of CH4.•Applying chemical-looping combustion concept can resolve the drawbacks of POM.•The appropriate selection of oxygen carrier becomes a critical issue for POM.•The use of steam or CO2 to replace air remains to be a great challenge.•Perovskites using lattice oxygen for syngas production showed prominent results. This work comprehensively reviews the recent advances for chemical-looping reforming of CH4 (CLR) technology, which breaks down the traditional CH4 reforming process (including steam and dry reforming) into two separate half-steps, namely CH4 oxidation and replenishment of oxygen carrier (OC) with appropriate oxidizing agents. In order to steer the conversion of CH4 toward partial oxidation (POM) for synthesis gas (H2+CO) production rather than total oxidation for producing CO2 and H2O, the appropriate selection of OC becomes a critical issue. Moreover, instead of the commonly used air to re-oxidize the oxygen-depleted OC after reaction with CH4, steam and CO2 have been proposed as two alternatives, opening up the opportunities to produce extra H2 and CO. However, owing to much weaker oxidization ability of steam and CO2 than air, the low oxidation degree and slow oxidation rate seem to remain as challenges. Furthermore, the resistance of OC to attrition, agglomeration and carbon deposition is also of great importance. In these regards, the latest major milestones are compiled. © 2015 Elsevier Ltd.

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.

Zhang Z.,Northwest University, China
Nongye Jixie Xuebao/Transactions of the Chinese Society of Agricultural Machinery | Year: 2011

The sewage sludge of Shenzhen Binhe Wastewater Treatment Plant was used as the research object, the dry sludge and returned sludge as the water amendment, the leaves powder and woodchip as C/N and water conditioner, the four aerated static pile (ASP) systems (1.5 m×1 m×1.5 m) as the composting equipment, the sewage sludge composting process conditions were studied. The results showed that using the dry or returned sludge as water amendment to mix with the fresh sludge to the volume ratio of 1:1, the water content of the mixture could meet the composting conditions. Using leaves powder or woodchip as the C/N and water conditioner to mix with fresh sludge is more useful than using the dry or returned sludge, but it could increase the cost of the compost. For the different treatments the time the temperature of the compost over the 55°C is more than 12 d, and the compost satisfied the standard of harmless and stabilization. The two pilot-scale ASP systems (10 m×2 m×1.5 m) were used to confirm the conditions come from the small ASP systems experiment. The results indicated that one volume of fresh sludge mixed with one volume of dry or returned sludge the water content of the mix is appropriate for composting, but the volume ratio of 1:1 fresh sludge mixed with dry sludge is more effective than that of returned sludge and the compost could meet the standard of harmless and stabilization.

Wei L.,Northwest University, China | Qi J.-J.,Xidian University
Knowledge-Based Systems | Year: 2010

One of the key problems of knowledge discovery is knowledge reduction. Rough set theory and the theory of concept lattices are two efficient tools for knowledge discovery. Attribute reduction based on rough set theory and the theory of concept lattices both have been researched. Since an information system, the data description of rough set theory, and a formal context, the data description of concept lattice theory, can be taken as the other one, the attribute reduction based on the same data base can be studied from these two perspectives, and researching their relation is significant. This paper mainly discusses the relation between concept lattice reduction and rough set reduction based on classical formal context, which will be meaningful for the relation research between these two theories, and for their knowledge discovery. © 2010 Elsevier B.V. All rights reserved.

Zhang Y.,CAS Dalian Institute of Chemical Physics | Zhang Y.,University of Chinese Academy of Sciences | Wang X.,CAS Dalian Institute of Chemical Physics | Zhu Y.,Northwest University, China | Zhang T.,CAS Dalian Institute of Chemical Physics
Applied Catalysis B: Environmental | Year: 2013

The stabilization of volatile ruthenium from catalysts at high temperatures is an important issue in both academia and industry. In this paper, Ru-substituted barium hexaalumimates (BaRu0.2FeAl10.8O19) with βI-Al2O3 structure were prepared using the carbonates route and investigated for high-concentration of N2O decomposition. It was for the first time found that the evaporation of ruthenium species under high-temperature condition (1100-1200°C) could be effectively suppressed by the addition of Fe in the hexaaluminate precursor. Fe promoted the formation of intermediate stable BaRuO3 phase, which greatly alleviated the evaporation of Ru species during calcination, and thus allowed more Ru species enter into the final sintering-resistant hexaaluminate lattice after high-temperature treatment. Ru ions in the hexaaluminate structure only occupied the distorted tetrahedral interstitial Al(5) sites in the loosely packed mirror plane, which originated from Ru species in oxidic entities dispersed on the Ba-modified γ-Al2O3 and the intermediate BaRuO3 in the precursors. Ru ions in the Al(5) sites were key factors responsible for the high activity of N2O decomposition. © 2012 Elsevier B.V.

Qu K.X.,Northwest University, China
Genetika | Year: 2012

BMY cattle (1/2 Brahman, 1/4 Murray Grey and 1/4 Yunnan Yellow cattle) has been inter se breeding since 1980s. Genetic diversity of BMY cattle was extensively investigated using 16 microsatellite markers. A total of 130 microsatellite alleles and high allele size variance were detected. All loci displayed high genetic diversity with overall mean of N(a) = 8.13, PIC = 0.7224 and H(e) = 0.7666, which were higher than those of many other beef breeds. The allele-sharing neighbour-joining tree clearly displayed the new genotypic combinations and the minglement from both BMY cattle and Brahman. The results provided the genetic information to match the standards of new beef breed in South China.

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.

Feng H.-J.,Northwest University, China
Materials Chemistry and Physics | Year: 2015

First-principles calculations show that the photovoltaic effect of the BiFeO3/TiO2 heterostructures in the visible-light region can be improved by applying epitaxial strain and an electric field. The multi-field coupling effect in the interface makes the heterojunction an intriguing candidate towards fabricating the multifunctional photoelectric devices, and the microscopic mechanism involved is attributed to the spin transfer and charge rearrangement between the Fe 3d and O 2p orbitals in the vicinity of the interface. © 2015 Elsevier B.V. All rights reserved.

Cai X.,Northwest University, China | Li W.,Hong Kong Polytechnic University
IEEE Transactions on Audio, Speech and Language Processing | Year: 2013

Multi-document summarization aims to create a condensed summary while retaining the main characteristics of the original set of documents. Under such background, sentence ranking has hitherto been the issue of most concern. Since documents often cover a number of topic themes with each theme represented by a cluster of highly related sentences, sentence clustering has been explored in the literature in order to provide more informative summaries. For each topic theme, the rank of terms conditional on this topic theme should be very distinct, and quite different from the rank of terms in other topic themes. Existing cluster-based summarization approaches apply clustering and ranking in isolation, which leads to incomplete, or sometimes rather biased, analytical results. A newly emerged framework uses sentence clustering results to improve or refine the sentence ranking results. Under this framework, we propose a novel approach that directly generates clusters integrated with ranking in this paper. The basic idea of the approach is that ranking distribution of sentences in each cluster should be quite different from each other, which may serve as features of clusters and new clustering measures of sentences can be calculated accordingly. Meanwhile, better clustering results can achieve better ranking results. As a result, ranking and clustering by mutually and simultaneously updating each other so that the performance of both can be improved. The effectiveness of the proposed approach is demonstrated by both the cluster quality analysis and the summarization evaluation conducted on the DUC 2004-2007 datasets. © 2006-2012 IEEE.

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.

Zhang S.,Northwest University, China | Zhang S.,Shaanxi Center for Stem Cell Engineering and Technology | Teng Y.,Arizona State University
Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis | Year: 2013

Generating homozygous mutants in mammalian cells has been complicated by their diploid genome. If one allele of an autosomal gene was disrupted, the resulting heterozygous mutant is unlikely to display a phenotype due to the existence of the other allele. Although embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are excellent cellular models for analyzing developmental events or disease phenotypes in vitro, a direct analysis of recessive phenotypes has been limited by their diploidy. Recently, four independent research groups reported successful derivation of haploid mouse embryonic stem cells which provide an effective platform for studying mammalian gene function. The aim of this review is to describe the strategies for deriving haploid ESCs and compare their characteristics with diploid ESCs, and further discuss the potential application of haploid ESCs in genetic screening and homozygous mutant animal production. © 2013 Elsevier B.V.

Yang X.,Portland State University | Yang X.,Northwest University, China | Guo Y.,Portland State University | Strongin R.M.,Portland State University
Organic and Biomolecular Chemistry | Year: 2012

A fluorescent chemodosimeter for cysteine detection was developed based on a tandem conjugate addition and intramolecular cyclization reaction. The method exhibited an excellent selectivity for cysteine over other biothiols such as homocysteine and glutathione. © The Royal Society of Chemistry 2012.

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.

Zhao J.,Northwest University, China | Bai M.,Zhaoqing University
Nonlinear Analysis: Real World Applications | Year: 2016

In this paper, we investigate some sufficient conditions for the breakdown of local smooth solutions to the three dimensional nonlinear nonlocal dissipative system modeling electro-hydrodynamics. This model is a strongly coupled system by the well-known incompressible Navier-Stokes equations and the classical Poisson-Nernst-Planck equations. We show that the maximum of the vorticity field alone controls the breakdown of smooth solutions, which reveals that the velocity field plays a more dominant role than the density functions of charged particles in the blow-up theory of the system. Moreover, some Prodi-Serrin type blow-up criteria are also established. © 2016 Elsevier Ltd. All rights reserved.

Fang Y.,Northwest University, China
IEEE Communications Letters | Year: 2010

Source correlation estimation is an important issue remained in Slepian-Wolf Coding (SWC), while a counterpart issue in noisy transmission is channel noise estimation. This letter considers the transmission of SWC bitstream over a noisy channel. We show that it is possible to estimate both source correlation and channel noise using an accumulated Low-Density Parity-Check (LDPC) syndrome. © 2010 IEEE.

Yang M.,University of Eastern Finland | Kuittinen S.,University of Eastern Finland | Zhang J.,Northwest University, China | Keinanen M.,University of Eastern Finland | Pappinen A.,University of Eastern Finland
Bioresource Technology | Year: 2013

This study investigated the effects of pretreatment conditions, dilute sulfuric acid concentration and treatment time, on the carbohydrate solubility of a mixture of barley straw and grain. The conditions were expressed as combined severity (CS) to evaluate sugar recovery from pretreated samples. Enzymatic hydrolysates from the lignocellulose pretreatment residues were also included to the results. CS was positively correlating with glucose recovery in all conditions, but in higher acid concentrations CS did not predict xylose recovery. It appeared that the residual xylan better indicate the xylose release. An optimal fermentable sugar yield from the mixture of barley straw and grain was obtained by maintaining the CS at around 1.38, corresponding to an overall glucose yield of 96% and a xylose yield of 57%. © 2013 Elsevier Ltd.

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..

Xu Z.,Xian Jiaotong University | Chang X.,Xian Jiaotong University | Xu F.,Xian 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.

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.

Zhu N.,Northwest University, China
Dong wu xue yan jiu = Zoological research / "Dong wu xue yan jiu" bian ji wei yuan hui bian ji | Year: 2012

This study compares superovulation efficiency during different stages of the estrus cycle in mice by investigating the pudendum appearance, vaginal epithelial cell type, and the follicular development dynamics, in relation to the estrus cycle. We determined the stages of the estrus cycle by observing the pudendum and making vaginal smears of the Kunming mouse, and ascertaining the follicular development by making paraffin sections. Based on the observation, mice in stages of proestrus, oestrus, metoestrus and dioestrus were superovulated respectively, and their follicular developments and embryo collection results were tracked to ascertain the appropriate estrus cycle stage for superovulation. Our data showed that pudendum appearance and vaginal smears could effectively distinguish different stages of the estrus cycle and that ovarian tissue observation showed that follicular development, corpus luteum formation and luteolysis were regular during the estrus cycle. Likewise, during the estrus cycle of the Kunming mouse, pudendum appearance, vaginal epithelial cell type and follicular development were relational to one another. Superovulating mice in different stages of the estrus cycle showed marked differences both in pregnancy rate and average number of embryos collected. Proestrus was significantly better than metoestrus and dioestrus (P<0.05), and better than oestrus, but the difference between them was not significant (P>0.05). We suggest that pudendum appearance and vaginal smears can be used to distinguish estrus cycle stages and that proestrus is the optimal stage of the estrus cycle for superovulation.

Guo J.,Northwest University, China | Guo J.,Swedish University of Agricultural Sciences | Jorjani H.,Swedish University of Agricultural Sciences | Carlborg T.,Swedish University of Agricultural Sciences
BMC Genetics | Year: 2012

Background: The genome-wide association study (GWAS) is a useful approach to identify genes affecting economically important traits in dairy cattle. Here, we report the results from a GWAS based on high-density SNP genotype data and estimated breeding values for nine production, fertility, body conformation, udder health and workability traits in the Brown Swiss cattle population that is part of the international genomic evaluation program.Result: GWASs were performed using 50 k SNP chip data and deregressed estimated breeding values (DEBVs) for nine traits from between 2061 and 5043 bulls that were part of the international genomic evaluation program coordinated by Interbull Center. The nine traits were milk yield (MY), fat yield (FY), protein yield (PY), lactating cow's ability to recycle after calving (CRC), angularity (ANG), body depth (BDE), stature (STA), milk somatic cell score (SCS) and milk speed (MSP). Analyses were performed using a linear mixed model correcting for population confounding. A total of 74 SNPs were detected to be genome-wide significantly associated with one or several of the nine analyzed traits. The strongest signal was identified on chromosome 25 for milk production traits, stature and body depth. Other signals were on chromosome 11 for angularity, chromosome 24 for somatic cell score, and chromosome 6 for milking speed. Some signals overlapped with earlier reported QTL for similar traits in other cattle populations and were located close to interesting candidate genes worthy of further investigations.Conclusions: Our study shows that international genetic evaluation data is a useful resource for identifying genetic factors influencing complex traits in livestock. Several genome wide significant association signals could be identified in the Brown Swiss population, including a major signal on BTA25. Our findings report several associations and plausible candidate genes that deserve further exploration in other populations and molecular dissection to explore the potential economic impact and the genetic mechanisms underlying these production traits in cattle. © 2012 Guo et al.; licensee BioMed Central Ltd.

Sun C.-Y.,Northwest University, China | Yue R.-H.,Ningbo University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

It is found by Cai and Su that the interaction between dark energy and cold dark matter is likely to change the sign during the cosmological evolution. Motivated by this, we suggest a new form of interaction between dark energy and dark matter, which changes from negative to positive as the expansion of or universe changes from decelerated to accelerated. We find that the interacting model is consistent with the second law of thermodynamics and the observational constraints. And, we also discuss the unified adiabatic-squared sound speed of the model. © 2012 American Physical Society.

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.

Cao Y.,Northwest University, China
Wei sheng wu xue bao = Acta microbiologica Sinica | Year: 2012

We studied the isolation methods and diversity of culturable fecal actinobacteria associated with Panthera tigris tigris by using culture-dependent approaches. Fresh fecal samples of healthy Panthera tigris tigris were collected from Yunnan Safari Park. Pretreatment of the samples, isolation media and inhibitors were tested for actinobacteria isolation. 16S rRNA genes of actinobacteria were sequenced and subjected to phylogenetic analysis. The abundance of culturable actinobacteria was 1.10 x 10(8) cfu/g colony forming units (CFU) per gram of feces (wet weight). We obtained 110 purified cultural actinobacterium strains. The analysis based on 16S rRNA gene sequences showed that these strains were distributed in 10 different families and 12 genera of actinobacteria at least, and most of them were non-filamentous, such as Arthrobacter, Dietzia, Kocuria, Corynebacterium and Microbacterium. Streptomyces was the mainly classical filamentous actinobacteria, and up to 64% of total. Drying and heating up the fecal samples can greatly increase the rate of the actinobacteria. Many kinds of inhibitors and chemical defined media are suitable for isolation of fecal actinobacteria. The culturable actinobacteria are abundant in Panthera tigris tigris feces. Our study found an effective method to isolate animals' fecal actinobacteria and it's useful for studying and exploiting animals' fecal actinobacteria.

Yang F.,Northwest University, China | Yang F.,University of Nebraska - Lincoln | Hanna M.A.,University of Nebraska - Lincoln | Sun R.,Beijing Forestry University
Biotechnology for Biofuels | Year: 2012

Biodiesel is a promising alternative, and renewable, fuel. As its production increases, so does production of the principle co-product, crude glycerol. The effective utilization of crude glycerol will contribute to the viability of biodiesel. In this review, composition and quality factors of crude glycerol are discussed. The value-added utilization opportunities of crude glycerol are reviewed. The majority of crude glycerol is used as feedstock for production of other value-added chemicals, followed by animal feeds. © 2012 Yang et al; licensee BioMed Central Ltd.

Hao M.,Dalian University of Technology | Li Y.,Dalian University of Technology | Wang Y.,Northwest University, China | Zhang S.,Dalian University of Technology
Analytica Chimica Acta | Year: 2011

Presently, a genetic algorithm (GA)-support vector machine (SVM) coupled approach is proposed for optimizing the 2D molecular descriptor subset generated for series of P2Y12 (members of the G-protein-coupled receptor family) antagonists, with the statistical performance and efficiency of the model being simultaneously enhanced by SVM kernel-based nonlinear projection. As we know, this is the first QSAR study for prediction of P2Y12 inhibition activity based on an unusually large dataset of 364 P2Y12 antagonists with diversity of structures. In addition, three other widely used approaches, i.e., partial least squares (PLS), random forest (RF), and Gaussian process (GP) routines combined with GA (namely, GA-PLS, GA-RF, GA-GP, respectively) are also employed and compared with the GA-SVM method in terms of several rigorous evaluation criteria. The obtained results indicate that the GA-SVM model is a powerful tool for prediction of P2Y12 antagonists, producing a conventional correlation coefficient R2 of 0.976 and Rcv2 (cross-validation) of 0.829 for the training set as well as Rpred2 of 0.811 for the test set, which significantly outperforms the other three methods with the average R2=0.894, Rcv2=0.741, Rpred2=0.693. The proposed model with excellent prediction capacity from both the internal to external quality should be helpful for screening and optimization of potential P2Y12 antagonists prior to chemical synthesis in drug development. © 2011 Elsevier B.V.

Shi Y.,Northwest University, China | Shi Y.,Purdue University | Lee L.-Y.,Purdue University | Gelvin S.B.,Purdue University
Plant Journal | Year: 2014

Summary Agrobacterium genetically transforms plants by transferring and integrating T-(transferred) DNA into the host genome. This process requires both Agrobacterium and host proteins. VirE2 interacting protein 1 (VIP1), an Arabidopsis bZIP protein, has been suggested to mediate transformation through interaction with and targeting of VirE2 to nuclei. We examined the susceptibility of Arabidopsis vip1 mutant and VIP1 overexpressing plants to transformation by numerous Agrobacterium strains. In no instance could we detect altered transformation susceptibility. We also used confocal microscopy to examine the subcellular localization of Venus-tagged VirE2 or Venus-tagged VIP1, in the presence or absence of the other untagged protein, in different plant cell systems. We found that VIP1-Venus localized in both the cytoplasm and the nucleus of Arabidopsis roots, agroinfiltrated Nicotiana benthamiana leaves, Arabidopsis mesophyll protoplasts and tobacco BY-2 protoplasts, regardless of whether VirE2 was co-expressed. VirE2 localized exclusively to the cytoplasm of tobacco and Arabidopsis protoplasts, whether in the absence or presence of VIP1 overexpression. In transgenic Arabidopsis plants and agroinfiltrated N. benthamina leaves we could occasionally detect small aggregates of the Venus signal in nuclei, but these were likely to be imagining artifacts. The vast majority of VirE2 remained in the cytoplasm. We conclude that VIP1 is not important for Agrobacterium-mediated transformation or VirE2 subcellular localization. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Lai M.-H.,University of Malaya | Lim K.-S.,University of Malaya | Gunawardena D.S.,University of Malaya | Yang H.-Z.,Northwest University, China | And 2 more authors.
Optics Letters | Year: 2015

In this work, we have demonstrated thermal stress relaxation in regenerated fiber Bragg gratings (RFBGs) by using direct CO2-laser annealing technique. After the isothermal annealing and slow cooling process, the Bragg wavelength of the RFBG has been red-shifted. This modification is reversible by re-annealing and rapid cooling. It is repeatable with different cooling process in the subsequent annealing treatments. This phenomenon can be attributed to the thermal stress modification in the fiber core by means of manipulation of glass transition temperature with different cooling rates. This finding in this investigation is important for accurate temperature measurement of RFBG in dynamic environment. © 2015 Optical Society of America.

Feng H.-J.,Northwest University, China
Physica B: Condensed Matter | Year: 2013

First-principals calculations show that the magnetization reversal of BiFeO3 film can be observed in y component with reversal of electric field more than ±0.001 V/Å. The charge distribution and hybridization is determined by the surface atomic distortions in plane. Bi-6s stereochemically active lone pair is still able to contribute to the electronic localization and thus the electric polarization in the film. © 2012 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.

He X.,Xian 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.

Hu X.,Northwest University, China | Spilke J.,Martin Luther University of Halle Wittenberg
Field Crops Research | Year: 2011

The primary method used to analyze regional crop variety trials is based on the analysis of variance (ANOVA), which requires a homogenous variance-covariance of data. While other models are available, the problem of how the models should be assessed and which model is more suitable for a given trial's data has not been solved. This restricts the applicability of the models. Therefore, a mixed linear model with flexible variance-covariance structures is proposed. Relationships are introduced for various variance-covariance structures of mixed models, and other models for analyzing crop regional trials. Using data from regional corn trials in northeastern and northern China, an assessment was made of the information criterion and likelihood-ratio-test, along with the goodness of fit of variance-covariance structures. This regional trial data facilitated comparison between an ANOVA model and a mixed linear model with an optimal variance-covariance structure. The results showed that the variance-covariance of varietal effects over environmental influences was not homogeneous, as is required in the ANOVA model. Instead, it was found to be heterogeneous in all trials considered. On average, the ratio of significant varietal differences for the same variety was only 86% when comparing the ANOVA model and the optimal mixed linear model. Also, there were obvious differences in the yield ranking of varieties between the two models. The mean standard error of a difference of varietal effects in the optimally-fitted mixed linear model was smaller than that in the ANOVA model. © 2010 Elsevier B.V.

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.

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.

Sato T.,University of Tokyo | Isozaki Y.,University of Tokyo | Hitachi T.,University of Tokyo | Shu D.,Northwest University, China
Gondwana Research | Year: 2014

In the earliest Cambrian the major diversification of small shelly fossils (SSFs) was the first episode of the so-called Cambrian Explosion. In order to clarify the background environmental conditions of this event, we examined the lowermost Cambrian strata with bedded phosphorites in the Chengjiang area, South China. The lowermost Cambrian (the Zhongyicun Mb of the Zhujiaqing Fm) in eastern Yunnan is composed of bedded phosphorites and phosphatic limestones with diverse SSFs. We investigated 3 sections within the Chengjiang area at Hongjiachong, Maotianshan, and Xiaolantian. Detailed lithostratigraphic analysis of outcrops and drill cores at Hongjiachong indicates that the Zhongyicun Mb consists of 5 distinct units, A to E in ascending order. The presence of 15 genera of SSFs in 20 horizons shows that the Zhongyicun Mb yields two distinct SSF assemblages of Fortunian age (earliest Cambrian; 541-529. Ma); i.e. the first assemblage with simple-shape SSFs (Anabarites, Protohertzina) from basal Unit A, and the second assemblage with various molluscan shells (Paracarinachites, Ocruranus-Eohalobia) from Units C-E. As well as abundant phosphate grains, all SSFs occur as clastic grains, suggesting that phosphorite was primarily formed in extreme shallow-water settings, as were the small shelly animals. We established that the first occurrence of the second SSF assemblage is at least 5. m lower (ca. 1-2. myr earlier in age) than previously reported in Chengjiang, and we speculate that the major diversification in SSF assemblage likely occurred during the Fortunian, at least before ca. 534. Ma. Judging from the rift-related tectonic setting and relevant paleogeography of western South China, we further speculate that the Zhongyicun Mb was primarily deposited in restricted embayments in the Kangdian rift basin, and that the rapid SSF diversification in the Fortunian occurred in a unique setting in highly phosphorus-rich seawater. © 2013 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.

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.

Sun C.-Y.,Northwest University, China | Yue R.-H.,Ningbo University
Journal of Cosmology and Astroparticle Physics | Year: 2013

It is found that the evolutions of density perturbations on the super-Hubble scales are unstable in the models with dark-sector interaction Q proportional to the energy density of cold dark matter (CDM) and constant equation of state parameter of dark energy (DE). In this paper, to avoid the instabilities, we suggest a new covariant model for the energy-momentum transfer between DE and CDM. Then we show that the the large-scale instabilities of curvature perturbations can be avoided in a universe filled only by DE and CDM. Furthermore, by including the additional components of radiation and baryons, we calculate the dominant non-adiabatic modes in the radiation era and find that the modes grow in the power law with exponent at the order of unit. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

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.

Bai Y.,Northwest University, China | Wang Y.,CAS Institute of Soil and Water Conservation
Soil Science | Year: 2011

An understanding of spatial variability for soil chemical properties is essential in optimizing fertilization and sustaining yield. The objective of this study was to investigate the spatial variability of soil chemical properties in a 10-year-old jujube trees hillslope (2,725 m) on the Loess Plateau of China. A total of 250 soil samples were collected at two depths (0-10 and 10-30 cm) in August 2010. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus, pH, and electrical conductivity were determined for all soil samples, and data were analyzed by the classic and geostatistical methods. Classic statistics showed that soil organic carbon, TN, total phosphorus, and electrical conductivity had moderate variability, and pH had low variability. Soil organic carbon and TN in the lower position were significantly greater than in the upper and middle positions (P < 0.01), whereas pH in the middle slope was significantly greater than the other positions (P < 0.01). The geostatistical statistics results showed that the soil chemical properties were defined by the exponential or spherical models. The nugget-to-sill ratios indicated that all soil chemical properties had moderate dependences. The results of cross-validation showed that spatial prediction maps from ordinary kriging method were reliable in the study slope (the kriged reduced mean square error higher than 0.99 and the kriged average error close to 0). These results and maps could provide useful information for the development and application of precision agriculture on the Loess Plateau. © 2011 by Lippincott Williams & Wilkins.

Ning J.,Hong Kong Polytechnic University | Ning J.,Xidian University | Ning J.,Northwest University, China | Zhang L.,Hong Kong Polytechnic University | And 2 more authors.
Pattern Recognition | Year: 2010

Efficient and effective image segmentation is an important task in computer vision and object recognition. Since fully automatic image segmentation is usually very hard for natural images, interactive schemes with a few simple user inputs are good solutions. This paper presents a new region merging based interactive image segmentation method. The users only need to roughly indicate the location and region of the object and background by using strokes, which are called markers. A novel maximal-similarity based region merging mechanism is proposed to guide the merging process with the help of markers. A region R is merged with its adjacent region Q if Q has the highest similarity with Q among all Q's adjacent regions. The proposed method automatically merges the regions that are initially segmented by mean shift segmentation, and then effectively extracts the object contour by labeling all the non-marker regions as either background or object. The region merging process is adaptive to the image content and it does not need to set the similarity threshold in advance. Extensive experiments are performed and the results show that the proposed scheme can reliably extract the object contour from the complex background. © 2009 Elsevier Ltd. All rights reserved.

Song X.,Northwest University, China
Wood and Fiber Science | Year: 2012

Cork is a natural and renewable raw material harvested from the outer bark of oak (Quercus spp.) trees. Unique and valuable properties of cork include low density, low permeability, high elasticity, good heat and acoustic insulation properties, and resistance to chemical and microbial attack. Chemical composition of cork is affected by many factors including the Quercus species and the number of times that cork has been harvested from the tree (ie virgin vs reproduction cork). Differences in chemical composition can significantly influence cork properties. In this study, chemical composition of virgin and reproduction cork from Quercus variablis trees in Shaanxi Province, China, was investigated. Cork samples were sequentially extracted with dichloromethane, ethanol, and water in a Soxhlet extractor. Eluted fractions were analyzed using ion chromatography. Chemical composition of virgin Q. variablis cork was 34.3% suberin, 20.6% lignin, 17.4% extractives, and 15.2% polysaccharides. Composition of reproduction cork was 36.9% suberin, 19.9% lignin, 12.7% extractives, and 12.0% polysaccharides. These results show that composition of virgin and reproduction Q. variablis cork was similar. Virgin Q. variablis cork had greater extractives and polysaccharides content than reproduction cork but a little less suberin. Chemical composition of Q. variablis cork from China is significantly different from that of Quercus suber L. cork from Europe. © 2012 by the Society of Wood Science and Technology.

Vannier J.,CNRS Geological Laboratory of Lyon: earth, planets and environment | Liu J.,Northwest University, China | Lerosey-Aubril R.,CNRS Geological Laboratory of Lyon: earth, planets and environment | Vinther J.,University of Bristol | Daley A.C.,University of Oxford
Nature Communications | Year: 2014

Understanding the way in which animals diversified and radiated during their early evolutionary history remains one of the most captivating of scientific challenges. Integral to this is the 'Cambrian explosion', which records the rapid emergence of most animal phyla, and for which the triggering and accelerating factors, whether environmental or biological, are still unclear. Here we describe exceptionally well-preserved complex digestive organs in early arthropods from the early Cambrian of China and Greenland with functional similarities to certain modern crustaceans and trace these structures through the early evolutionary lineage of fossil arthropods. These digestive structures are assumed to have allowed for more efficient digestion and metabolism, promoting carnivory and macrophagy in early arthropods via predation or scavenging. This key innovation may have been of critical importance in the radiation and ecological success of Arthropoda, which has been the most diverse and abundant invertebrate phylum since the Cambrian. © 2014 Macmillan Publishers Limited.

Liang H.,Northwest University, China | Liang H.,University of Chicago | Deng X.,University of Chicago | Li X.,University of North Dakota | And 2 more authors.
Nucleic Acids Research | Year: 2014

The Pseudomonas aeruginosa quorum-sensing (QS) systems contribute to bacterial homeostasis and pathogenicity. Although the AraC-family transcription factor VqsM has been characterized to control the production of virulence factors and QS signaling molecules, its detailed regulatory mechanisms still remain elusive. Here, we report that VqsM directly binds to the lasI promoter region, and thus regulates its expression. To identify additional targets of VqsM in P. aeruginosa PAO1, we performed chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq) and detected 48 enriched loci harboring VqsM-binding peaks in the P. aeruginosa genome. The direct regulation of these genes by VqsM has been confirmed by electrophoretic mobility shift assays and quantitative real-time polymerase chain reactions. A VqsMbinding motif was identified by using the MEME suite and verified by footprint assays in vitro. In addition, VqsM directly bound to the promoter regions of the antibiotic resistance regulator NfxB and the master type III secretion system (T3SS) regulator ExsA. Notably, the vqsM mutant displayed more resistance to two types of antibiotics and promoted bacterial survival in a mouse model, compared to wild-type PAO1. Collectively, this work provides new cues to better understand the detailed regulatory networks of QS systems, T3SS, and antibiotic resistance. © The Author(s) 2014.

Song S.,Northwest University, China | Singh V.P.,Texas A&M University
Stochastic Environmental Research and Risk Assessment | Year: 2010

This study aims to model the joint probability distribution of periodic hydrologic data using meta-elliptical copulas. Monthly precipitation data from a gauging station (410120) in Texas, US, was used to illustrate parameter estimation and goodness-of-fit for univariate drought distributions using chi-square test, Kolmogorov-Smirnov test, Cramer-von Mises statistic, Anderson-Darling statistic, modified weighted Watson statistic, and Liao and Shimokawa statistic. Pearson's classical correlation coefficient r n, Spearman's ρ n, Kendall's τ, Chi-Plots, and K-Plots were employed to assess the dependence of drought variables. Several meta-elliptical copulas and Gumbel-Hougaard, Ali-Mikhail-Haq, Frank and Clayton copulas were tested to determine the best-fit copula. Based on the root mean square error and the Akaike information criterion, meta-Gaussian and t copulas gave a better fit. A bootstrap version based on Rosenblatt's transformation was employed to test the goodness-of-fit for meta-Gaussian and t copulas. It was found that none of meta-Gaussian and t copulas considered could be rejected at the given significance level. The meta-Gaussian copula was employed to model the dependence, and these results were found satisfactory. © 2009 Springer-Verlag.

Yang X.,Portland State University | Yang X.,Northwest University, China | Guo Y.,Portland State University | Strongin R.M.,Portland State University
Angewandte Chemie - International Edition | Year: 2011

Similar but different: A benzothiazole derivative can be used to detect cysteine (Cys) and homocysteine (Hcy) simultaneously in neutral media. The method involves thioether formation followed by cyclization to release 2-(2′-hydroxy-3′-methoxyphenyl)benzothiazole (HMBT) and a lactam. The differences in ring-formation kinetics allow spectral or kinetic modes to be used to identify Cys and Hcy. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li Z.,Northwest University, China | Li Z.,CAS Institute of Soil and Water Conservation | Zheng F.-L.,CAS Institute of Soil and Water Conservation | Liu W.-Z.,CAS Institute of Soil and Water Conservation
Agricultural and Forest Meteorology | Year: 2012

The present and future spatiotemporal characteristics of reference evapotranspiration (ET 0) are examined in this paper. ET 0 during 1961-2009 are calculated by the Penman-Monteith method recommended by FAO (Food and Agriculture Organization) with historical weather data while ET 0 during 2011-2099 are downscaled from HadCM3 (Hadley Centre Coupled Model, version 3) outputs under two emission scenarios (A2 and B2) by SDSM (Statistical DownScaling Model). The spatial distribution and temporal trend in ET 0 are interpreted by Inverse Distance Weighted Interpolation and Mann-Kendall method, respectively. Results show that the annual mean ET 0 is 1060.3mm, the lowest and highest values are found in the southwest and northwest region due to the spatial distribution of climatic factors, respectively. ET 0 has increased significantly due to the downward trend in relative humidity and upward trend in temperature on the Loess Plateau during 1961-2009. HadCM3 projects a continuous increase in ET 0 in the 21st century and the upward trend will be more pronounced after 2050. Averaged over the two emission scenarios for the whole area, the projected increase are 4%, 7% and 12% for the three periods 2011-2040, 2041-2070 and 2071-2099, respectively; the increase under A2 scenario are slightly greater than those under B2 scenario. An obvious gradient is detected for the projected increase in ET 0 from northeast to southwest region in the 21st century. The increase in ET 0 will possibly influence the water resource on the Loess in the 21st century and some countermeasures should be taken to reduce the adverse impacts. © 2011 Elsevier B.V.

Liu J.-Q.,Guangdong Medical College | Huang Y.-S.,Guangdong Medical College | Zhao Y.Y.,Northwest University, China | Jia Z.B.,Guangdong Medical College
Crystal Growth and Design | Year: 2011

On the basis of 1, 4-bis(2-methyl-imidazol-1-yl)butane (bib), three new coordination polymers, namely, [Co(L1)(bib)]n (1), {[Co(L2)(bib)] 1.5H2O}n (2), and {[Co(L3)(bib)0.5] H 2O}n (3)(H2L1 = m-phthalic acid, H 2L2 = glutaric acid, and H2L3 = 1, 4-phenylenediacetic acid), have been synthesized and characterized. Polymer 1 features a three-dimensional (3D) 3-fold interpenetrating CdSO4 motif containing multiple interweaving helical chains. Compound 2 displays a 3D 3-fold interpenetrating 3-connected ThSi2 architecture with intriguing pseudo-Borromean links. Complex 3 shows a 3D 2-fold interpenetrating Pcu net. The results reveal that the dicarboxyl building blocks with different conformations play a significant role in promoting the diversity of the observed structural motifs. In addition, the magnetic property of 3 is also studied. © 2010 American Chemical Society.

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.

Feng H.-J.,Northwest University, China
EPL | Year: 2013

First-principles calculations show that spin-up and spin-down carriers accumulate adjacent to the opposite surfaces of a BiFeO3 (BFO) film upon applying an external bias. The spin carriers are equal in magnitude and opposite in direction, and spin-down carriers move in the direction opposite to the external electric field while spin-up ones move along the field direction. This novel spin transfer properties make the BFO film an intriguing candidate for application in spin capacitors and BFO-based multiferroic field-effect devices. © Copyright EPLA, 2013.

Wang Q.,Xidian University | Wang Q.,Northwest University, China | Yun Y.,Beijing Forestry University
Microchimica Acta | Year: 2012

We have investigated the oxidative electrochemistry of nitrite on glassy carbon electrodes modified with cobalt nanoparticles, poly(3,4-ethylenedioxythiophene) (PEDOT), and graphene. The modified electrode was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The results suggest that this new type of electrode combines the advantages of PEDOT-graphene films and cobalt nanoparticles and exhibits excellent electrocatalytic activity towards the oxidation of nitrite. There is a linear relationship between the peak current and the nitrite concentration in the range from 0. 5 μM to 240 μM, and the detection limit is 0. 15 μM. The modified electrodes also enable the determination of nitrite at low potentials where the noise level and interferences by other electro-oxidizable compounds are weak. © 2012 Springer-Verlag.

Li X.,Northwest University, China
Mathematical Problems in Engineering | Year: 2015

The main purpose of this paper is using the combinatorial method and algebraic manipulations to study some sums of powers of Chebyshev polynomials and give several interesting identities. As some applications of these results, we obtained several divisibility properties involving Chebyshev polynomials. © 2015 Xiaoxue Li.

Zheng L.,Xian Shiyou University | Song J.-F.,Xian 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.

Song S.,Northwest University, China | Nie R.,Wei He Watershed Management Bureau of shanxi
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2011

This paper derives conditional Copulas and Copula densities of 5 common asymmetric Archimedean Copulas, and presents a procedure for applying these copulas to hydrological drought joint probability distribution. Monthly average flow data from Zhuangtou gauging station in Weihe Basin, China, is used to illustrate this approach, and parameters of these univariate distributions are estimated using the methods of moments (MOM), probability weighted moments (PWM), maximum likelihood method (MLM) and genetic algorithm (GA). A goodness-of-fit test indicates that the given univariate distribution is acceptable, that the drought variables have a high inter-dependency, and that M12 Copula gives better fitting of joint probability distribution. Calculation results of M12 Copula of the station for joint probabilities, conditional probabilities and their return periods are also presented. © Copyright.

Chen N.,Nanjing University | Ma T.,Heilongjiang Provincial Research Institute of Surveying and Mapping | Zhang X.,Northwest University, China
Catena | Year: 2016

Understanding the responses of soil erosion processes to land cover changes would benefit catchment ecological management. Landsat thematic mapper images in 1987, 1995, and 2007 were collected to obtain the historical normalized difference vegetation index and land cover data of the Beiluo River basin, one of the catchments in the Loess Plateau. The sediment load data of five subcatchments were collected in the corresponding periods. A set of location-weighted landscape contrast indices was used to analyze the effect of land cover changes on soil erosion processes, as specified by the following indices: slope gradient, flow path length, relative altitude, and relative distance. Results showed that vegetation cover (VC) notably increased from 41.12% to 63.43% in the basin from 1987 to 2007. The increased VC was mainly concentrated in the hilly-gully area from 18.40% in 1987 and 20.21% in 1995 to 41.65% in 2007. The mean annual sediment load modulus in the region over the same periods significantly decreased by 90%. All the indices for each subcatchment exhibited a decreasing trend. The change extent of the indices revealed a significantly positive correlation with that of sediment load modulus. Slope gradient and flow path length were the most important influential factors on soil erosion. Results implied that the improvement in land cover in the Beiluo River basin from 1987 to 2007 led to sediment entrapment in the sink area and changed the soil erosion processes, especially the slope gradient and flow length of the soil erosion source area. This study contributed to improving catchment ecological management and evaluating erosion control practices in the Loess Plateau. © 2015 Elsevier B.V.

Wen J.G.,Northwest University, China
Xi bao yu fen zi mian yi xue za zhi = Chinese journal of cellular and molecular immunology | Year: 2011

To clone a novel swine gene P58(IPK)[58-kDa(inhibitor of protein kinase) protein] and prepare its polyclonal antibody for further research of influenza and host interaction. The swine P58(IPK); gene was first identified in silico through homology searching in the swine EST database. Then this gene was amplified by reverse transcription polymerase chain reaction (RT-PCR). The cDNA of the gene contained the complete open reading frame(ORF) of 1 518 bp, and encoded 505 amino acid residues (Accession No.HQ287801). The gene was first analyzed using bioinformatics methods. Then P58(IPK) was cloned into a prokaryotic expression vector pET-32a to construct a recombinant plasmid named as pET-P58(IPK). The fusion protein his-P58(IPK) was expressed in E.coli BL21 and purified using a his-tag protein purification column. Subsequently rabbits were immunized with the purified protein. Specific polyclonal antibody against the fusion protein his-P58(IPK) was obtained. The activity of the antibody was determined through double-immunodiffusion test. The titer of the antibody was 1:20 000 as shown by ELISA. specifically recognized the protein P58(IPK) by Western blot and immunofluorescence assay. The novel swine gene P58(IPK) has been successfully cloned and its polyclonal antibody has been prepared.

Li Z.,Northwest University, China | Brissette F.,University of Quebec | Chen J.,University of Quebec
Hydrological Processes | Year: 2013

Six precipitation probability distributions (exponential, Gamma, Weibull, skewed normal, mixed exponential and hybrid exponential/Pareto distributions) are evaluated on their ability to reproduce the statistics of the original observed time series. Each probability distribution is also indirectly assessed by looking at its ability to reproduce key hydrological variables after being used as inputs to a lumped hydrological model. Data from 24 weather stations and two watersheds (Chute-du-Diable and Yamaska watersheds) in the province of Quebec (Canada) were used for this assessment. Various indices or statistics, such as the mean, variance, frequency distribution and extreme values are used to quantify the performance in simulating the precipitation and discharge. Performance in reproducing key statistics of the precipitation time series is well correlated to the number of parameters of the distribution function, and the three-parameter precipitation models outperform the other models, with the mixed exponential distribution being the best at simulating daily precipitation. The advantage of using more complex precipitation distributions is not as clear-cut when the simulated time series are used to drive a hydrological model. Although the advantage of using functions with more parameters is not nearly as obvious, the mixed exponential distribution appears nonetheless as the best candidate for hydrological modelling. The implications of choosing a distribution function with respect to hydrological modelling and climate change impact studies are also discussed. Copyright © 2012 John Wiley & Sons, Ltd.

Li Z.,Northwest University, China | Brissette F.,University of Quebec | Chen J.,University of Quebec
International Journal of Climatology | Year: 2014

Stochastic modelling of daily precipitation is useful for many hydrological and agricultural applications; however, the ability of the precipitation generator should be assessed to ensure accurate precipitation simulation. In particular, the appropriate choice of a precipitation probability distribution is of utmost importance. The Loess Plateau in China has a semi-arid climate with strong monsoon influence and contains some of the most erodible soils in the world. The large annual variability in precipitation and the common occurrence of very large rainfall events makes this region very challenging for stochastic generation of precipitation. Accordingly, the objective of this study is to compare the performances of six precipitation probability distributions (exponential, gamma, Weibull, skewed normal, mixed exponential and hybrid exponential/generalized Pareto distributions) on the Loess Plateau of China based on daily precipitation data of 47 stations during 1961-2009. Results indicate that using increasingly more complex precipitation distributions contribute to more accurate precipitation simulation. However, none of the tested distributions is able to simulate all the observed statistical characteristics of precipitation. The three-parameter models are superior to simulating the observed mean and variance. The hybrid exponential/generalized Pareto distribution is the best at simulating the frequency distributions and interannual variations of precipitation while the skewed normal distribution performs the best in reproducing extreme precipitation events. Overall, as erosion on the Loess Plateau is highly dependent on extreme precipitation, the skewed normal distribution may be the best candidate and therefore is recommended on the Loess Plateau. © 2013 Royal Meteorological Society.

Zhao Q.,Northwest University, China
Wei sheng wu xue bao = Acta microbiologica Sinica | Year: 2012

Avian hepatitis E virus (HEV), a member of Hepeviridae family, is genetically and antigenically related with human and swine HEV in the family. Since its discovery, avian HEV infection has been investigated in many countries from serology and molecular epidemiology studies. At present, five complete or near complete genomes of avian HEV isolates were reported in GenBank and were divided into three genotypes. The complete genome of avian HEV contains 3 ORFs of which ORF2 gene encodes capsid protein containing the primary epitopes of viral particles and is target gene for serodiagnostic antigen and vaccine candidate. Because avian HEV infection has significant impact on the poultry industry and potential zoonotic transmission, the researches on avian HEV have been given much attention. We here give a broad review of the research update on the aetiology, pathogenesis and the antigenicity of capsid protein of avian HEV based on identification of Chinese avian HEV isolate.

Li X.,Xidian University | Yi H.,Northwest University, China
Fuzzy Sets and Systems | Year: 2016

Compactness, closeness and SC are conditions to ensure the existence of fuzzy bases for polymatroids, G-V fuzzy matroids and H fuzzy matroids respectively. In this work, relations of these three conditions with different fuzzy independent systems are studied. Furthermore, the equivalence of compactness, closeness and SC for G-V fuzzy matroids is proved and the existence of fuzzy bases of H fuzzy matroids is verified. Finally, it has been pointed out that H fuzzy matroids and E fuzzy matroids induced from polymatroids are the same and the question whether an H fuzzy matroid is a fuzzy pre-matroid is solved. © 2016 Elsevier B.V.

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.

Zhao Z.,Northwest University, China
Fangzhi Gaoxiao Jichukexue Xuebao | Year: 2015

For a given positive integer a, the generalizations of higher-order Euler numbers Ek n, a were defined by using (Equation). By using the elementary methods, several explicit formulas, some congruences and an inversion formula for generalizations of higher-order Euler numbers were obtained.

Zhang J.,Nanyang Technological University | Cao C.,Nanyang Technological University | Cao C.,Queens University of Belfast | Xu X.,Northwest University, China | And 4 more authors.
ACS Nano | Year: 2014

Tailoring optical properties of artificial metamaterials, whose optical properties go beyond the limitations of conventional and naturally occurring materials, is of importance in fundamental research and has led to many important applications such as security imaging, invisible cloak, negative refraction, ultrasensitive sensing, and transformable and switchable optics. Herein, by precisely controlling the size, symmetry, and topology of alphabetical metamaterials with U, S, Y, H, U-bar, and V shapes, we have obtained highly tunable optical response covering visible-to-infrared (vis-NIR) optical frequency. In addition, we show a detailed study on the physical origin of resonance modes, plasmonic coupling, the dispersion of resonance modes, and the possibility of negative refraction. We have found that all the electronic and magnetic modes follow the dispersion of surface plasmon polaritons; thus, essentially they are electronic- and magnetic-surface-plasmon-polaritons-like (ESPP-like and MSPP-like) modes resulted from diffraction coupling between localized surface plasmon and freely propagating light. On the basis of the fill factor and formula of magnetism permeability, we predict that the alphabetical metamaterials should show the negative refraction capability in visible optical frequency. Furthermore, we have demonstrated the specific ultrasensitive surface enhanced Raman spectroscopy (SERS) sensing of monolayer molecules and femtomolar food contaminants by tuning their resonance to match the laser wavelength, or by tuning the laser wavelength to match the plasmon resonance of metamaterials. Our tunable alphabetical metamaterials provide a generic platform to study the electromagnetic properties of metamaterials and explore the novel applications in optical frequency. © 2014 American Chemical Society.

Deng Y.,Northwest University, China
Fangzhi Gaoxiao Jichukexue Xuebao | Year: 2015

Using the theorem for the generalized Dedekind sums and Dirichlet L-functions to study the distribution property of the hybrid mean value involving the generalized Dedekind sums and two-term exponential sums. Thus, two sharper asymptotic formulas are given.

Li Q.,Northwest University, China
Advance Journal of Food Science and Technology | Year: 2015

This study offers a series of scientific, reasonable, simple and pragmatic plan of nutrition meal, which tallies with the characteristics of motor projects, researching the dinning condition and nutritious situation in the certain period of training, in order to provide reference for scientifically tennis training, teaching and exercising. Stamina is the base of motor skill, in which nutritious supplement is the core. Reasonable nutritious supplement plays a key role in the training effect and race scores of national short track speed skating. According to the judgment of energy metabolism, organism state of tennis and the features of energy supply system in tennis competition. © Maxwell Scientific Organization, 2015.

Zhao J.,Northwest University, China
Journal of Mathematical Physics | Year: 2016

In this paper, we first generalize a new energy approach, developed by Guo and Wang [Commun. Partial Differ. Equations 37, 2165-2208 (2012)] in the framework of homogeneous Besov spaces for proving the optimal temporal decay rates of solutions to the fractional power dissipative equation, then we apply this approach to the critical and supercritical surface quasi-geostrophic equation and the critical Keller-Segel system.We show that certain weighted negative Besov norm of solutions is preserved along time evolution and obtain the optimal temporal decay rates of the spatial derivatives of solutions by the Fourier splitting approach and the interpolation techniques.

Wang D.,Northwest University, China
Fangzhi Gaoxiao Jichukexue Xuebao | Year: 2015

In order to study the orthogonality of Laguerre polynomial convolution, a kind of identity on Laguerre polynomial convolution H(x, k+1, n) is obtained with the use of primary methods and properties of power series, and computational formulas of this convolution and its orthogonality are obtained with the use of definition and known properties, the conclusions promote the study of Laguerre polynomial.

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.

Zhang R.,Nanyang Technological University | Zhang R.,Northwest University, China | Xu Z.-B.,Xian 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.

Zhan A.,Northwest University, China | Zhan A.,Pennsylvania State University | Lynch J.P.,Pennsylvania State University
Journal of Experimental Botany | Year: 2015

Suboptimal nitrogen (N) availability is a primary constraint for crop production in developing countries, while in developed countries, intensive N fertilization is a primary economic, energy, and environmental cost for crop production. We tested the hypothesis that under low-N conditions, maize (Zea mays) lines with few but long (FL) lateral roots would have greater axial root elongation, deeper rooting, and greater N acquisition than lines with many but short (MS) lateral roots. Maize recombinant inbred lines contrasting in lateral root number and length were grown with adequate and suboptimal N in greenhouse mesocosms and in the field in the USA and South Africa (SA). In low-N mesocosms, the FL phenotype had substantially reduced root respiration and greater rooting depth than the MS phenotype. In low-N fields in the USA and SA, the FL phenotype had greater rooting depth, shoot N content, leaf photosynthesis, and shoot biomass than the MS phenotype. The FL phenotype yielded 31.5% more than the MS phenotype under low N in the USA. Our results are consistent with the hypothesis that sparse but long lateral roots improve N capture from low-N soils. These results with maize probably pertain to other species. The FL lateral root phenotype merits consideration as a selection target for greater crop N efficiency. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

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.

Gong Y.-K.,Northwest University, China | Winnik F.M.,University of Montreal | Winnik F.M.,Japan National Institute of Materials Science
Nanoscale | Year: 2012

Engineered nanoparticles (NPs) play an increasingly important role in biomedical sciences and in nanomedicine. Yet, in spite of significant advances, it remains difficult to construct drug-loaded NPs with precisely defined therapeutic effects, in terms of release time and spatial targeting. The body is a highly complex system that imposes multiple physiological and cellular barriers to foreign objects. Upon injection in the blood stream or following oral administation, NPs have to bypass numerous barriers prior to reaching their intended target. A particularly successful design strategy consists in masking the NP to the biological environment by covering it with an outer surface mimicking the composition and functionality of the cell's external membrane. This review describes this biomimetic approach. First, we outline key features of the composition and function of the cell membrane. Then, we present recent developments in the fabrication of molecules that mimic biomolecules present on the cell membrane, such as proteins, peptides, and carbohydrates. We present effective strategies to link such bioactive molecules to the NPs surface and we highlight the power of this approach by presenting some exciting examples of biomimetically engineered NPs useful for multimodal diagnostics and for target-specific drug/gene delivery applications. Finally, critical directions for future research and applications of biomimetic NPs are suggested to the readers. © 2012 The Royal Society of Chemistry.

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.

Sun J.,Northwest University, China
Electronics, Communications and Networks IV - Proceedings of the 4th International Conference on Electronics, Communications and Networks, CECNet2014 | Year: 2015

The demodulation technology of angle-error in Unmanned Aerial Vehicle (UAV) data-link is theoretically analyzed and its engineering implementation is also discussed in this paper. Using the angle-error demodulation method, the design of the automatic tracking system has been successfully applied to a certain type of UAV) currently. © 2015 Taylor & Francis Group, London.

Nie M.,Northwest University, China
Finite Fields and their Applications | Year: 2016

We determine the zeta functions of trinomial curves in terms of Jacobi sums, and obtain an explicit formula of the genus of a trinomial curve over a finite field, and we study the conditions for this curve to be a maximal curve over a finite field. © 2016 Elsevier Inc. All rights reserved.

Pang Y.,University of Michigan | Song H.,University of Michigan | Kim J.H.,University of Michigan | Hou X.,University of Michigan | And 2 more authors.
Nature Nanotechnology | Year: 2014

Optical tweezers use the momentum of photons to trap and manipulate microscopic objects, contact-free, in three dimensions. Although this technique has been widely used in biology and nanotechnology to study molecular motors, biopolymers and nanostructures, its application to study viruses has been very limited, largely due to their small size. Here, using optical tweezers that can simultaneously resolve two-photon fluorescence at the single-molecule level, we show that individual HIV-1 viruses can be optically trapped and manipulated, allowing multi-parameter analysis of single virions in culture fluid under native conditions. We show that individual HIV-1 differs in the numbers of envelope glycoproteins by more than one order of magnitude, which implies substantial heterogeneity of these virions in transmission and infection at the single-particle level. Analogous to flow cytometry for cells, this fluid-based technique may allow ultrasensitive detection, multi-parameter analysis and sorting of viruses and other nanoparticles in biological fluid with single-molecule resolution. © 2014 Macmillan Publishers Limited.

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.

Wang S.,CAS Research Center for Eco Environmental Sciences | Wang S.,Northwest University, China | Zhang S.,CAS Research Center for Eco Environmental Sciences | Huang H.,CAS Research Center for Eco Environmental Sciences | And 2 more authors.
Environmental Pollution | Year: 2014

In order to characterize polybrominated diphenyl ethers (PBDEs), and hydroxylated and methoxylated PBDEs (OH-PBDEs and MeO-PBDEs) in the soil-plant system, soil and plant samples were collected from an e-waste recycling area in China. Forty one PBDEs, twelve OH-PBDEs and MeO-PBDEs were detected in the soil and plant samples. Concentrations of PBDEs in roots were significantly correlated to their concentrations in the soils, but the percentages of lower brominated congeners in the plants were higher than those in the soils. Significant positive linear relationships exist between concentrations of ΣOH-PBDEs and ΣMeO-PBDEs with higher levels of ΣMeO-PBDEs than those of ΣOH-PBDEs in the soils, plant roots and leaves. A majority of the OH-/MeO-PBDEs had the hydroxyl or methoxy group at the ortho-positions to the biphenyl bond for most of the plant species. However the occurrence of meta- and para- substituted OH-/MeO-PBDEs in soils and plants were also confirmed. © 2013 Elsevier Ltd. All rights reserved.

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.

Fu Q.,Northwest University, China
International Journal of Online Engineering | Year: 2016

Health is an eternal topic of human concern, especially in modern times, and fitness equipment is an important part fitness routines. With the rapid development of information technology and electronic technology, using photoelectric methods to detect the physiology index of the human body has become an unescapable trend. Therefore, bringing in some advanced technology in other fields to design a portable, noninvasive, low-cost multifunctional human physiological health index monitor has great significance. This thesis first introduces the situation of fitness equipment, then studies people's demand for intelligent fitness equipment, and specifically proposes the measurement scheme of a human physical health index based on a photoelectric sensor. By studying the production principle of photoelectric volume pulse waves, this thesis sets up the experimental platform to prove the effectiveness of the proposed method. Finally, this research shows that intelligent fitness equipment like a multifunctional fitness monitor based on a photoelectric sensor can effectively improve people's exercise style and has large market application prospects.

Zhao Y.-Y.,Northwest University, China | Zhao Y.-Y.,University of California at Irvine | Cheng X.-L.,National Institutes for Food and Drug Control | Lin R.-C.,Beijing University of Chinese Medicine
International Review of Cell and Molecular Biology | Year: 2014

Lipids are the fundamental components of biological membranes as well as the metabolites of organisms. Lipids play diverse and important roles in biologicals. The lipid imbalance is closely associated with numerous human lifestyle-related diseases, such as atherosclerosis, obesity, diabetes, and Alzheimer's disease. Lipidomics or lipid profiling is a system-based study of all lipids aiming at comprehensive analysis of lipids in the biological system. Lipidomics has been accepted as a lipid-related research tool in lipid biochemistry, clinical biomarker discovery, disease diagnosis, and in understanding disease pathology. Lipidomics will not only provide insights into the specific functions of lipid species in health and disease, but will also identify potential biomarkers for establishing preventive or therapeutic programs for human diseases. This review presents an overview of lipidomics followed by in-depth discussion of its application to the study of human diseases, including extraction methods of lipids, analytical technologies, data analysis, and clinical research in cancer, neuropsychiatric disease, cardiovascular disease, kidney disease, and respiratory disease. We describe the current status of the identification of metabolic biomarkers in different diseases. We also discuss the lipidomics for the future perspectives and their potential problems. The application of lipidomics in clinical studies may provide new insights into lipid profiling and pathophysiological mechanisms. © 2014 Elsevier Inc.

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.

Dowen J.M.,Whitehead Institute For Biomedical Research | Fan Z.P.,Whitehead Institute For Biomedical Research | Fan Z.P.,Massachusetts Institute of Technology | Hnisz D.,Whitehead Institute For Biomedical Research | And 12 more authors.
Cell | Year: 2014

The pluripotent state of embryonic stem cells (ESCs) is produced by active transcription of genes that control cell identity and repression of genes encoding lineage-specifying developmental regulators. Here, we use ESC cohesin ChIA-PET data to identify the local chromosomal structures at both active and repressed genes across the genome. The results produce a map of enhancer-promoter interactions and reveal that super-enhancer-driven genes generally occur within chromosome structures that are formed by the looping of two interacting CTCF sites co-occupied by cohesin. These looped structures form insulated neighborhoods whose integrity is important for proper expression of local genes. We also find that repressed genes encoding lineage-specifying developmental regulators occur within insulated neighborhoods. These results provide insights into the relationship between transcriptional control of cell identity genes and control of local chromosome structure. © 2014 Elsevier Inc.

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.

Liu C.-Y.,Northwest University, China
Journal of High Energy Physics | Year: 2013

We study the correlation function of fundamental and anti-symmetric Wilson surfaces in AdS 7 /CF T 6 correspondence. We discuss the classical annulus solution on the AdS side and the boundary terms. The total on-shell action of annulus has divergence. Despite of this fact, we can study the Gross-Ooguri phase transition. The reason is that the two possible leading contributions to the correlation have same singularity. From this, we find that the Gross-Ooguri phase transition also exist in Wilson surface case. © 2013 SISSA, Trieste, Italy.

To elucidate how physiological and biochemical mechanisms of chilling stress are regulated by abscisic acid (ABA) pretreatment, pepper variety (cv. 'P70') seedlings were pretreated with 0.57 mM ABA for 72 h and then subjected to chilling stress at 10°/6°C (day/night). Chilling stress caused severe necrotic lesions on the leaves and increased malondialdehyde and H(2)O(2) levels. Activities of monodehydroascorbate reductase (DHAR), dehydroascorbate reductase, glutathione reductase, guaiacol peroxidase, ascorbate peroxidase, ascorbate, and glutathione increased due to chilling stress during the 72 h, while superoxide dismutase and catalase activities decreased during 24 h, suggesting that chilling stress activates the AsA-GSH cycle under catalase deactivation in pepper leaves. ABA pretreatment induced significant increases in the above-mentioned enzyme activities and progressive decreases in ascorbate and glutathione levels. On the other hand, ABA-pretreated seedlings under chilling stress increased superoxide dismutase and guaiacol peroxidase activities and lowered concentrations of other antioxidants compared with untreated chilling-stressed plants. These seedlings showed concomitant decreases in foliage damage symptoms, and levels of malondialdehyde and H(2)O(2). Induction of Mn-SOD and POD was observed in chilling-stressed plants treated with ABA. The expression of DHAR1 and DHAR2 was altered by chilling stress, but it was higher in the presence than in the absence of ABA at 24 h. Overall, the results indicate that exogenous application of ABA increases tolerance of plants to chilling-induced oxidative damage, mainly by enhancing superoxide dismutase and guaiacol peroxidase activities and related gene expression.

Sun Y.D.,Northwest University, China
Genetics and molecular research : GMR | Year: 2012

Fruit lycopene content and total soluble solid content are important factors determining fruit quality of tomatoes; however, the dynamic quantitative trait loci (QTL) controlling lycopene and soluble solid content have not been well studied. We mapped the chromosomal regions controlling these traits in different periods in F(2:3) families derived from a cross between the domestic and wild tomato species Solanum lycopersicum and S. pimpinellifolium. Fifteen QTLs for lycopene and soluble solid content and other related traits analyzed at three different fruit ripening stages were detected with a composite interval mapping method. These QTLs explained 7-33% of the individual phenotypic variation. QTLs detected in the color-changing period were different from those detected in the other two periods. On chromosome 1, the soluble solid content QTL was located in the same region during the color-changing and full-ripe periods. On chromosome 4, the same QTL for lycopene content was found during the color-changing and full-ripe periods. The QTL for lycopene content on chromosome 4 co-located with the QTL for soluble solid content during the full-ripe period. Co-location of lycopene content QTL and soluble solid content QTLs may be due to pleiotropic effects of a single gene or a cluster of genes via physiological relationships among traits. On chromosome 9, the same two QTLs for lycopene content at two different fruit ripening periods may reflect genes controlling lycopene content that are always expressed in tomato fruit development.

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.

Zhao L.,Northwest University, China
Fangzhi Gaoxiao Jichukexue Xuebao | Year: 2015

A systematic investigation to derive the Lie symmetries and exact solution of Rosenau-Hyman equation is presented. First of all, the symmetry group of Rosenau-Hyman equation is given with the help of Lie symmetry method and its partial differential form, and further the corresponding traveling wave solution is found out. Second, the exact solutions are obtained with the heuristics of the Jacobi elliptic function. These solutions have extensive application values to further research about some physical phenomenon which are described by the Rosenau-Hyman equation.

Li W.,Northwest University, China
Fangzhi Gaoxiao Jichukexue Xuebao | Year: 2015

By using the elementary method, according to the properties of the character χ of the mod q and the congruence equations, the mean value properties of the mixed exponential sums with Dirichlet characters is studied. An explicit formula for the fourth power mean of mixed exponential sums under certain conditions is given, and the previous results are also generalized.

Cytoplasmic male sterile line RC(7) of Chinese cabbage produces mature anthers without pollen. To understand the mechanisms involved, we examined the ultrastructural changes during development of the microspores. Development of microspores was not affected at the early tetrad stage. During the ring-vacuolated period, some large vacuoles appeared in the tapetum cells, making them larger, extending to the anther sac center during the monocyte period. At the same time, the tapetum degenerated as the microspores aborted, resulting in pollen-deficient anthers. As a result, the locules collapsed and the anthers shriveled. The callose was degraded in the pollen walls; abnormal deposits of electrodense material gave rise to irregular spike-shaped structures, rather than the characteristic rod-like shape of the B7 bacula. The internal intine wall of RC(7) was thinner than that of the B7 type. At the mitosis I microspore stage, the tapetum cells contained multiple plastids, with numerous small spherical plastoglobuli, and lipid bodies. Based on these observations, we suggest that RC(7) abortion may be due to mutated genes that normally regulate development of the pollen wall and cell walls in the RC(7) line.

Niu H.,CAS Research Center for Eco Environmental Sciences | Dizhang,CAS Research Center for Eco Environmental Sciences | Meng Z.,Northwest University, China | Cai Y.,CAS Research Center for Eco Environmental Sciences
Journal of Hazardous Materials | Year: 2012

Alginate-Fe 2+/Fe 3+ polymer coated Fe 3O 4 magnetic nanoparticles (Fe 3O 4@ALG/Fe MNPs) with core/shell structure are prepared and used as heterogeneous Fenton nanocatalyst to degrade norfloxacin (NOF). The Fenton-like process based on Fe 3O 4@ALG/Fe shows much higher efficiency on NOF degradation. Compared with Fe 3O 4 nanoparticle-H 2O 2 system, NOF degradation in Fe 3O 4@AlG/Fe-H 2O 2 system can be conducted in a wide pH range (pH 3.5-6.5) and independent on temperature. With 0.98mM H 2O 2 and 0.4gL -1 Fe 3O 4@ALG/Fe, 100% of NOF and 90% of TOC is removed within 60min, and the fluorine element in NOF molecule changes into F - ions within 1min, indicating that NOF degradation in this Fenton-like reaction is performed through direct defluorination pathway. XPS analysis shows that TOC removal in reaction solution mainly results from the adsorption of NOF degradation intermediates on catalyst. Due to the paramagneticity and high saturation magnetization of Fe 3O 4@ALG/Fe, the used catalyst with adsorbed NOF intermediate is collected from aqueous solution by applying an external magnetic field, leading to complete removal of NOF from water samples. As being composed of inorganic materials and biopolymer, Fe 3O 4@ALG/Fe MNPs are robust, thermo-stable, nontoxic and environmentally friendly. These attractive features endow Fe 3O 4@ALG/Fe as a potent Fenton-like catalyst for fluoroquinolones degradation. © 2012 Elsevier B.V.

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.

Feng H.,Northwest University, China
Plant physiology and biochemistry : PPB / Société française de physiologie végétale | Year: 2012

Quantitative real-time PCR (qRT-PCR) is currently the most accurate and widely applied method to detect differential genes expression, but choosing a suitable gene to be the internal control is a crucial factor for correct analysis of the results. MicroRNAs are fundamental regulatory genes of eukaryotic genomes, acting on several biological functions. Transcription accumulation of microRNAs has been studied using qRT-PCR, while no validated reference genes for microRNAs in wheat are available until now. In this study, nine previous reported housekeeping genes and ten wheat microRNAs were examined with regard to their use as normalizer and data was analyzed using geNorm and NormFind software. Expression stability of candidate inner reference genes was investigated in different conditions. After analysis of all the sample pools and samples after biotic and abiotic stress treatments, it was found that microRNAs had better expression stability than protein-coding genes, and mi167 and mi159 appeared to be the two most suitable reference genes in wheat. To confirm the stable expression of the putative reference genes in wheat, expression of mi171b of wheat was examined with inner reference genes mi167, mi159 and combination of mi157 and mi159 respectively. We provided evidence for that in order to get a more accurate result of gene expression, mi167 and mi159 should be used as inner reference gene for normalization together. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Jia S.,CAS Xian Institute of Optics and Precision Mechanic | Wu Y.,CAS Xian Institute of Optics and Precision Mechanic | Wang X.,CAS Xian Institute of Optics and Precision Mechanic | Wang N.,Northwest University, China
IEEE Photonics Journal | Year: 2014

A novel plasmonic lens consisting of metallic nanoslits with a patterned dielectric substrate is proposed. In the structure, all metallic nanoslits have the same geometrical parameters and interspacing. The phase of incident light is modulated beforehand by the substrate before they bump on the metal slits. The surface plasmon polaritons (SPPs) wave excited by the modulated light will be focused after passing through the slits. Numerical simulation demonstrates that the size of the generated focal spot is very close to half wavelength. The overriding advantage of the proposed structure is that it significantly reduces the difficulty in fabrication while the focusing properties are comparable to the ones with filling materials in the slits. © 2009-2012 IEEE.

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.

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.

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.

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.

Fang Y.,Northwest University, China
Science China Information Sciences | Year: 2011

Correlation estimation is a critical issue that impacts the application of Slepian-Wolf coding (SWC) in practice. Dynamic online correlation estimation is a type of newly-appearing approaches, in which the decoder estimates the virtual correlation channel between two correlated sources using both side information and the compressed SWC bitstream of the source. Since the compressed SWC bitstream usually contains partial information of the source, the emergence of dynamic online correlation estimation is helpful to solving the problem of correlation estimation in the SWC and further makes the SWC realisable. Currently, the SWC is usually implemented by LDPC codes. In this case, the SWC bitstream is just the LDPC syndrome of the source. It has been revealed that there are residual redundancies in LDPC syndromes, which can be used to estimate the crossover probability between two correlated binary sequences. However, this algorithm has not been well justified yet. This paper makes use of the central limit theorem (CLT) to establish a mathematic model for analyzing the performance of this algorithm. Especially, for irregular LDPC codes, the optimization of weight vectors is discussed in detail. Representative experimental results are provided to validate the analysis. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

Lin Q.,Northwest Normal University | Chen P.,Northwest Normal University | Liu J.,Northwest University, China | Fu Y.-P.,Northwest Normal University | And 2 more authors.
Dyes and Pigments | Year: 2013

The specific colorimetric detection of Cu2+ in the context of interference from coexisting metal ions in aqueous solution is a challenge. Therefore, a series of Cu2+ colorimetric chemosensors CS1∼CS3, bearing acylthiosemicarbazide moiety as binding site and nitrophenyl moiety as signal group, were designed and synthesized. Among these sensors, CS3 showed excellent colorimetric specific selectivity and high sensitivity for Cu 2+in DMSO/H2O binary solutions. When Cu2+ was added to the solution of CS3, a dramatic color change from brown to green was observed, while the cations Fe3+, Hg2+, Ag, Ca 2+, Zn2+, Pb2+, Cd2+, Ni2 , Co 2+, Cr3+ and Mg2+ did not interfere with the recognition process for Cu2+. The detection limits were 5.0 × 10-6 and 1.0 × 10-7 M of Cu2+ using the visual color changes and UVevis changes respectively. Test strips based on CS3 were fabricated, which could act as a convenient and efficient Cu2+ test kit. © 2013 Elsevier Ltd.

Since the first case of acquired immunodeficiency syndrome (AIDS) was reported in 1981, AIDS, as the global disease affecting 33.2 million people in 2007, has always been an unsolved problem worldwide. Reverse transcriptase (RT) is a crucial enzyme in the life cycle of human immunodeficiency virus type 1 (HIV-1), and thereby has been the prime drugs target for antiretroviral (ARV) therapy against AIDS. To date, two classes of RT inhibitors (RTIs), e.g., nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs), and a lot of compounds tested as RTIs have been described. To our knowledge, bis(heteroaryl)piperazines (BHAPs) have been considered as one class of promising NNRTIs, such as structurally and chemically related NNRTI delavirdine, which was approved by the U. S. Food and Drug Administration (FDA) for the treatment of HIV-1 infection in 1997. In this minireview, we make attempts to report the progress of synthesis and structure - activity relationship (SAR) of BHAPs, in the meantime, the synergistic inhibition of HIV-1 replication by combining delavirdine with other HIV-1 inhibitors is also discussed. It will pave the way for the design and development of BHAPs as anti-HIV-1 agents in AIDS chemotherapy in the future. © 2010 Bentham Science Publishers Ltd.

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.

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.

Zou D.,Northwest University, China
Metallurgical and Mining Industry | Year: 2015

This paper quantizes the mesoscopic inductor coupled circuit with dissipation by using the methods of normalized canonical transformation and unitary transformation, giving the accurate Hamiltonian. The fluctuation of the dissipative mesoscopic inductor coupled circuit is investigated. It shows that the average values for all the charges and currents are zero, but their mean-square values are not all zero when the circuit has no power. We also find that the zero point fluctuations of charges and currents exist in this system. It reveals that when t → ∞, the fluctuations of the charges and currents would attenuate as time evolving.

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.

The denoising of a natural image corrupted by additive Gaussian white noise is a classical problem in image processing. A new image denoising method is proposed by using the dependencies between the non-subsampled shearlet transform (NSST) coefficients and their neighbors. The NSST is well known for its approximate shift invariance and better directional selectivity, which are very important in image denoising. In order to take account of the dependency between the current NSST coefficient and its neighbors, a new multivariate probability density function (pdf) is exploited, and a multivariate shrinkage function for image denoising is derived from it by using the maximum a posteriori (MAP) estimator. Then, the blend of the proposed multivariate shrinkage function and its method noise thresholding using NSST is proposed for image denoising. Experimental results demonstrate that the proposed method is very competitive when compared with other existing denoising methods in the literature. © 2013 Elsevier GmbH.

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.

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.

Li Z.,Northwest University, China
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Reference crop evapotranspiration (ET0) is a very important variable for hydrology and agriculture and has been widely applied to actual evapotranspiration and crop water requirement calculation as well as hydrological simulation. Under the background of global changes, analyzing the spatiotemporal characteristics of ET0 can provide useful information for impact assessment of climate change on hydrology. After calculating ET0 with Penman-Monteith equation using meteorological data from 48 stations, inverse distance weighted interpolation and Mann-Kendall test are used to analyze the spatial distribution and temporal changes in ET0 on the Loess Plateau during 1961-2009. Results show that the annual mean value of ET0 is 1060. 3 mm; the values in the northwest region are greater than those in the southeast region and the smallest values occur in the southwest region, which is possibly caused by the regional combinations of different meteorological variables. Upward and downward trends are detected for 36 and 12 stations; however, only 30 and nine stations have increased and decreased significantly, respectively. Averaged over the Loess Plateau, ET0 has increased significantly by 1. 3 mm/ a; the greatest and smallest changes are in spring and winter, respectively. ET0 occurs abrupt change in 1994 and increases more significantly since then. The temporal trend in ET0 is possibly caused by the evolutions of meteorological factors, especially by the downward trend in humidity and upward trend in temperature as ET0 is most sensitive to changes in humidity and temperature on the Loess Plateau. The detected monotonic trend in ET0 on the Loess Plateau is different from other regions and the upward trend in ET0 is confirmed by this study. The continuous increase in ET0 and decrease in precipitation will worsen the water shortage on the Loess Plateau; therefore, some countermeasures are necessary to mitigate the adverse impacts of climate changes.

Wang G.,Xian 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.

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.

Yan S.,CAS Xian Institute of Optics and Precision Mechanic | Yao B.,CAS Xian Institute of Optics and Precision Mechanic | Zhao W.,CAS Xian Institute of Optics and Precision Mechanic | Lei M.,Northwest University, China
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2010

We demonstrate the possibility of creating multiple spherical spots in a 4-π- focusing system with a radially polarized beam. Using spherical waves to expand the plane wave factor in the Richards-Wolf integral, it is found that a proper spatial modulation in the amplitude of the input field with radial polarization can form multiple spherical spots with a focusing system satisfying the Herschel condition. These spots are distributed symmetrically about the focus on the optical axis with variable positions and intensities. Although we consider only the case of three spherical spots in this paper, generalization to the multiple-spots case will present no difficulty. © 2010 Optical Society of America.

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.

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.

Qiu L.,Northwest University, China | Qiu L.,Swedish University of Agricultural Sciences | Lindberg S.,Swedish University of Agricultural Sciences | Nielsen A.B.,Swedish University of Agricultural Sciences
Landscape and Urban Planning | Year: 2013

This study investigated whether preferences and biodiversity are compatible in an urban green space setting and whether people actually recognise and appreciate ecologically rich environments when exposed to these as part of a recreational visit. Data were collected through an on-site visitor-employed photography (VEP) study employing both lay people and ecology experts. Photos were taken by the participants during a walk along a 1.6. km trail through a recreational park with clear habitat variation. Half of the lay people and half of the experts each took five photos of features reflecting high preference and five reflecting low preference. The remaining half each took five photos of features they perceived to represent high species richness and five representing low species richness. Photos and written comments were then compared against an assessment of biodiversity values of the different habitats experienced along the trail. The results indicated that people can correctly perceive differences in biodiversity between urban green space habitat types. High biodiversity did not, however, relate positively to preference as half-open park areas were preferred to areas of more complex vegetation. Nevertheless, negative preferences for these richer habitat types were mostly related to the presence or execution of human interventions. The VEP method revealed on-site perception and preference to be highly context-specific, mainly triggered by specific features rather than the overall scenery and character of the setting. Differences in attitude between experts and lay people suggested that ecological knowledge could have a positive influence on preference for certain aspects of biodiversity. © 2013 Elsevier B.V.

Jia Y.-H.,Chinese Ministry of Water Resources | Jia Y.-H.,ShenYang Agricultural University | Jia Y.-H.,University of Chinese Academy of Sciences | Shao M.-A.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Jia X.-X.,Northwest University, China
Journal of Hydrology | Year: 2013

Temporal stability of spatial distributions of soil moisture are usually observed after repeated surveys of soil moisture across an area. To understand how temporal stability of soil moisture varied with soil depth under the combined influences of vegetation and local topography, we collected soil moisture data at intervals of 10. cm within 1-m profiles on a loessial slope in China in four plots (61. m × 5. m) under different types of vegetation (Korshinsk peashrub, KOP; purple alfalfa, ALF; natural fallow, NAF; millet, MIL). Measurements of soil water content were made by neutron probes on 15 occasions between 2010 and 2012. Soil moisture distributions in both the vertical and horizontal dimensions were investigated to describe its spatial pattern and to lay the groundwork for better understanding its temporal stability characteristics. The results indicated that: (1) soil moisture presented different vertical but similar horizontal trends in the four plots, with significant correlations of soil moisture occurring primarily among adjacent soil layers irrespective of vegetation types, mostly in soil profiles under KOP and ALF and less frequently in soil profiles under NAF and MIL; (2) based on Spearman rank correlation coefficients, with increasing depth temporal stability generally increased under KOP and MIL, but first increased and then decreased under ALF, and increased after the first three measurements under NAF; (3) based on the relative difference technique, points with extreme moisture tended to remain representative at more depths than did points with average moisture and their time stability increased with increasing soil depth; and (4) the correlation between MRD (mean relative differences) and the wetness index weakened with soil depth. The relationship between SDRD (the standard deviation of MRD) and the wetness index varied nonlinearly with soil depth. Vegetation type, soil depth and the wetness index, in descending order of influence, had significant effects on the temporal stability of soil moisture. Among selected soil properties, saturated hydraulic conductivity, bulk density and soil organic carbon all significantly affected the SDRDs. These observations are expected to add valuable information to the theory of temporal stability and for the practices of soil moisture management. © 2013.

Lu X.,Kyoto University | Lu X.,Northwest University, China | Saka S.,Kyoto University
Journal of Supercritical Fluids | Year: 2012

Typical monosaccharides, which constitute hemicelluloses and cellulose of lignocellulosic materials, were treated in batch hot compressed water to investigate monosaccharides' isomerization and decomposition. It was found that glucose and mannose were isomerized to each other while galactose was isomerized to tagatose and talose. On the other hand, arabinose was isomerized to ribulose and ribose while xylose was isomerized to xylulose and lyxose. Additionally, these isomerization products' formation was not only affected by initial monosaccharides but also the reaction conditions. Similarly the dehydration and the fragmentation reactions also depended on reaction conditions, in which possibly dehydration occurred firstly and fragmentation reaction followed. Furthermore, furfural was also detected when hexoses were treated in hot compressed water and it was proposed that furfural was formed via hexose fragmentation reactions through a pentose and formaldehyde pathway. On the other hand, the detection of 5-HMF when pentoses were treated in hot compressed water provided a hint that not only retro-aldol condensation reaction but also aldol condensation occurred when monosaccharides were treated in hot-compressed water. Based on these experiments, some new isomerization, fragmentation and dehydration reaction pathways were proposed to supplement previous knowledge on monosaccharides' decomposition scheme in hot compressed water. © 2011 Elsevier B.V. All rights reserved.

Cai X.,Northwest University, China | Li W.,Hong Kong Polytechnic University
IEEE Transactions on Audio, Speech and Language Processing | Year: 2012

Manifold-ranking has been recently exploited for query-focused summarization. It propagates query relevance from the given query to the document sentences by making use of both the relationships among the sentences and the relationships between the given query and the sentences. The sentences in a document set can be grouped into several topic themes with each theme represented by a cluster of highly related sentences. However, it is a well-recognized fact that a document set often covers a number of such topic themes. In this paper, we present a novel model to enhance manifold-ranking based relevance propagation via mutual reinforcement between sentences and theme clusters. Based on the proposed model, we develop two new sentence ranking algorithms, namely the reinforcement after relevance propagation (RARP) algorithm and the reinforcement during relevance propagation (RDRP) algorithm. The convergence issues of the two algorithms are examined. When evaluated on the DUC2005-2007 datasets and TAC2008 dataset, the performance of the two proposed algorithms is comparable with that of the top three systems. The results also demonstrate that the RDRP algorithm is more effective than the RARP algorithm. © 2012 IEEE.

Ren Y.,Shaanxi Normal University | Chang H.-L.,Northwest University, China | Endress P.K.,University of Zurich
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.

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.

Sun Y.,Xian University of Arts and Science | Zhao Y.,Northwest University, China
Journal of Nanoscience and Nanotechnology | Year: 2012

Rhaponticin (RA) extracted from many medicinal plants has been demonstrated to possess a variety of pharmacological activities including potent antitumor, antitumor-promoting, antithrombotic, antioxidant and vasorelaxant activities. However, its poor solubility and bioavailability restricted the clinical application greatly. In this work, surface modification of liposome with polyethylene glycol (PEG) was developed with the purpose of improving the pharmacokinetics and anti-tumor efficacy of RA. PEGylated liposomal RA (PEGL-RA) was prepared by dry-film method. Its mean particle size was 89.3±8.7 nm, mean zeta potential was -4.1 mV and encapsulation efficiency was 67.4±6.4%. Moreover, the results of pharmacokinetic analysis showed that the time of maximum plasma concentration (Tmax) of PEGL-RA was about 4.5 times higher than that of free RA after oral administration due to the lower distribution into the gastrointestinal tract. The mean T1/2 value of PEGL-RA and free RA were 350.12±0.87 min and 180.02±1.96 min, respectively. The AUC0→∞ ratio of PEGL-RA to free RA was about 2.41-fold (93.23 μg/mLmin/40.81 μg/mLmin). Plasma protein binding ability of RA was also studied. The results showed that RA with 33.6 μg/mL concentrations in human plasma and HSA achieved the percent of bound 39.23±3.78% and 22.28±2.34%, respectively. In the in vivo studies utilizing solid tumor-bearing rat, it was confirmed that PEGL-RA delivered remarkably larger amount of RA to tumor tissue and provided more significant anti-tumor activity than free RA. Furthermore, the cytotoxicity and fluorescence microscopic studies showed higher intracellular uptake of PEGL-RA than that of RA. In conclusion, PEGylated liposome was an effective delivery formulation for RA to increase the pharmacokinetics and therapeutic efficacy. Copyright © 2012 American Scientific Publishers. All rights reserved.

Feng H.-J.,Northwest University, China
Journal of Applied Physics | Year: 2013

First-principles density-functional theory calculations show that switching of magnetization by 90° can be achieved in BiFeO3 ultrathin film by applying external electric field. Spin-up carriers appear to the surface with positive field while spin-down ones to the negative field surface, arising from the redistribution of Fe-t2g orbital. The half-metallic behavior of Fe-3 d states in the surface of rhombohedral phase film makes it a promising candidate for antiferromagnetic/ferromagnetic bilayer heterostructure possessing electric field tunable ferromagnetic magnetization reversal and opens a new way towards designing spintronic multiferroics. The interface exchange-bias effect in this BiFeO3/ferromagnetic bilayer is mainly driven by the Fe-t2g orbital reconstruction, as well as spin transferring and rearrangement. © 2013 AIP Publishing LLC.

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.

Cheng Z.H.,Northwest University, China
Genetics and molecular research : GMR | Year: 2012

Garlic (Allium sativum) is propagated asexually. Since sexual cross breeding is almost impossible, means for effective breeding are not currently available and the available production cultivars are seriously aged and degenerated. A possible alternative for breeding is chemical induction. Trifluralin, a type of herbicide, has been reported to provoke chromosome doubling. However, this chemical had not been tested on garlic. We tested various trifluralin concentrations and treatment durations for efficiency in the induction of tetraploid garlic. A clove base of garlic with a stem cv. Gailiang was used as the ex-plant to induce calluses on Murashige and Skoog (MS) medium; the calluses were then inoculated onto MS medium containing different levels of trifluralin and cultured to induce chromosome number variation in vitro. Garlic calluses were effectively induced via the ex-plant and both shoots and roots differentiated well on MS medium containing 6-benzylaminopurine at 3.0 mg/L and indole-3-acetic acid at 0.1 mg/L. However, increases in trifluralin concentration and treatment duration reduced the survival rate and differentiation rate of calluses. Garlic callus cultured for 15 days on medium containing 100 μM trifluralin gave the highest rate of chromosome doubling. Through observation of chromosome number in the root apical cells and the morphology of guard cells on the leaf epidermis of the regenerated plantlets, it was clear that chromosome number variation was induced and tetraploids were produced in vitro by trifluralin treatment.

Fang Y.,Northwest University, China
IEEE Transactions on Communications | Year: 2013

Though distributed arithmetic coding (DAC) is an effective implementation of Slepian-Wolf coding, its performance, which is closely linked with its decoding complexity, has not received a thorough analysis. With binary sources with equally-likely symbols as the research object, this paper develops the DAC spectrum and makes use of it as a tool to answer the complexity problem of the ideal DAC decoder. Based on an in-depth analysis on DAC decoding process, we define the DAC spectrum and propose to find it by a recursive formulation. Firstly, the initial DAC spectrum is constrained by a functional equation and the Fourier transform is utilized to obtain its general explicit form. Secondly, an equation is given through which stage-(i+1) DAC spectrum can be deduced from stage-i DAC spectrum. A numerical method is also proposed for calculating DAC spectrum, whose convergency is proved. To measure the complexity of the ideal DAC decoder, we define the expansion factor and relate it to DAC spectrum. It is proved that if binary symbols 0 and 1 are mapped onto partially overlapped intervals [0, q) and [1-q, 1) respectively, the expansion factor will converge to 2q, i.e., the complexity of the ideal rate-α DAC decoder is approximately O(2n(1-α)). © 2013 IEEE.

Wu F.,Northwest University, China | Zhou W.,Xian 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.

Yin Z.,Northwest University, China
Methods in molecular biology (Clifton, N.J.) | Year: 2012

Encapsulation-vitrification and encapsulation-dehydration are two newly developed techniques for cryopreservation of embryogenic cell suspensions. Here, we describe the two protocols using grapevine (Vitis) as a model plant. Cell suspensions at the exponential growth stage cultured in a cell suspension maintenance medium are encapsulated to form beads, each being about 4 mm in diameter and containing 25% cells. In the encapsulation-vitrification procedure, the beads are stepwise precultured in increasing concentrations of sucrose medium up to 0.75 M, with 1 day for each concentration. The precultured beads are treated with a loading solution for 60 min and then dehydrated with plant vitrification solution 2 at 0°C for 270 min before a direct immersion in liquid nitrogen. Following cryostorage, the beads are rapidly rewarmed at 40°C for 3 min and then unloaded with 1 M sucrose solution for 30 min. In the encapsulation-dehydration procedure, the beads are precultured in increasing concentrations of sucrose medium up to 1 M, with 1 day for each concentration, and then maintained on 1 M sucrose medium for 3 days. The precultured beads are dehydrated for 6 h under a sterile air flow, prior to rapid freezing in liquid nitrogen. The freezing and rewarming procedures are the same as used in the encapsulation-vitrification technique. The unloaded beads from encapsulation-vitrification and rewarmed beads from encapsulation-dehydration are postcultured on a recovery medium for 3 days at 25°C in the dark for survival. Surviving cells are transferred to a regrowth medium to induce cell proliferation. Embryogenic cell suspensions are reestablished by suspending the cells in a cell suspension maintenance medium maintained on a gyratory shaker at 25°C in the dark. For plant regeneration, surviving cells are transferred from the recovery medium to an embryo maturation medium and maintained at 25°C under light conditions. Embryos at the torpedo stage are cultured on a rooting medium until whole plantlet regenerates.

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.

Sun R.,Northwest University, China | Sun R.,University of Lorraine | Dubessy J.,University of Lorraine
Geochimica et Cosmochimica Acta | Year: 2012

The SAFT-LJ equation of state improved by Sun and Dubessy (2010) can represent the vapor-liquid equilibrium and PVTx properties of the CO 2-H 2O system over a wide P-T range because it accounts for the energetic contribution of the main types of molecular interactions in terms of reliable molecular based models. Assuming that NaCl fully dissociates into individual ions (spherical Na + and Cl -) in water and adopting the restricted primitive model of mean spherical approximation to account for the energetic contribution due to long-range electrostatic forces between ions, this study extends the improved SAFT-LJ EOS to the H 2O-NaCl and the CO 2-H 2O-NaCl systems at temperatures below 573K. The EOS parameters for the interactions between ion and ion and between ion and water were determined from the mean ionic activity coefficient data and the density data of the H 2O-NaCl system. The parameters for the interactions between ion and CO 2 were evaluated from CO 2 solubility data of the CO 2-H 2O-NaCl system. Comparison with the experimental data shows that this model can predict the mean ionic activity coefficient, osmotic coefficient, saturation pressure, and density of aqueous NaCl solution and can predict the vapor-liquid equilibrium and PVTx properties of the CO 2-H 2O-NaCl system over the range from 273 to 573K, from 0 to 1000bar, and from 0 to 6mol/kg NaCl with high accuracy. © 2012 Elsevier Ltd.

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.

Li J.,Northwest University, China | Jia H.,Lanzhou University
Plant Physiology and Biochemistry | Year: 2013

The phytohormone auxin participates in lateral root formation and primary root growth in plants. The auxin gradient formation is mainly regulated by the direction of polar auxin transport (PAT). PAT requires PIN family proteins, which are auxin transport facilitators and contribute to the establishment and maintenance of auxin gradients and mediate multiple developmental processes. Here, we report the effect of the 3', 5'-cyclic guanosine monophosphate (cGMP), an important second messenger, on postembryonic developmental of Arabidopsis lateral root. We find that enhanced cGMP level through the application of the membrane permeable cGMP analog 8-Br-cGMP, promotes the initiation of lateral root primordia and formation of lateral root. 6-Anilino-5,8-quinolinedione (Ly83583, the guanylate cyclase inhibitor) negatively regulates the process. cGMP also mediates acropetal auxin transport and basipetal auxin transport in the root. We further find that 8-Br-cGMP and Ly83583 change the expression of auxin transport genes and alter the polar localization and expression of PIN1 and PIN2 proteins. Moreover, Ly83583 affects actin organization and localization. Taken together, we propose that cGMP affects auxin transport and auxin gradient through modulation PINs proteins localization and expression. cGMP regulates postembryonic formation of Arabidopsis lateral root through the crosstalk with PAT. © 2013 Elsevier Masson SAS.

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.

Yu C.-Y.,Northwest University, China
Journal of Applied Genetics | Year: 2013

Yellow seed is a desirable characteristic for the breeding of oilseed Brassica crops, but the manifestation of seed coat color is very intricate due to the involvement of various pigments, the main components of which are flavonols, proanthocyanidin (condensed tannin), and maybe some other phenolic relatives, like lignin and melanin. The focus of this review is to examine the genetics mechanism regarding the biosynthesis and regulation of these pigments in the seed coat of oilseed Brassica. This knowledge came largely from recent researches on the molecular mechanism of TRANSPARENT TESTA (tt) and similar mutations in the ancestry model plant of Brassica, Arabidopsis. Some key enzymes in the flavonoid (flavonols and proanthocyanidin) biosynthetic pathway have been characterized in tt mutants. Some orthologs to these TRANSPARENT TESTA genes have also been cloned in Brassica species. However, it is suggested that some alterative metabolism pathways, including lignin and melanin, might also be involved in seed color manifestation. Polyphenol oxidases, such as laccase, tyrosinase, or even peroxidase, participate in the oxidation step in proanthocyanidin, lignin, and melanin biosynthesis. Moreover, some researches also suggested that melanic pigment in black-seeded Brassica was several fold higher than in yellow-seeded Brassica. Although more experiments are required to evaluate the importance of lignin and melanin in seed coat browning, the current results suggest that the flavonols and proanthocyanidin are not the only roles affecting seed color. © 2013 Institute of Plant Genetics, Polish Academy of Sciences, Poznan.

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.

Kelly P.,Renmin University of China | Huo X.,Northwest University, China
Journal of Forest Economics | Year: 2013

In developing countries with small holdings, targeting payments-for-environmental-services prices to site-specific environmental benefits becomes administratively impractical. Instead, governments fix price and either dictate parcel enrollment or let farmers decide, which might be expected to maximize environmental benefits and minimize opportunity costs, respectively. No paper has actually tested such hypotheses in a developing-country setting. This paper examines China's Sloping Land Conversion Program, with 32 million planting forests, using a unique dataset on 3397 parcels, including farmer-choice and government-choice parcels. Farmers consider similar criteria to local governments but weight land characteristics within the farm (not the landscape) and household characteristics. © 2012 Department of Forest Economics, Swedish University of Agricultural Sciences, Umeå.

Yi W.J.,Northwest University, China
Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban | Year: 2010

Paddy soil samples were collected from six provinces of China, and an anaerobic incubation test was conducted to examine the microbial Fe(III) reduction potential under the conditions of different flooding time and with glucose, pyruvate, lactate, or acetate as the sole carbon source. The results showed that flooding time had significant effects on the eigenvalue of Fe(III) reduction, Vmax, with the order of 20 d > 30 d > 12 d > 1 d > 5 d, which suggested that the difference in the microbial community structure in different flooding periods was the main reason inducing the different potential of Fe(III) reduction. In all test flooding periods, glucose and pyruvate were the superior carbon sources, with the Fe(III) reduction rate being 88.1%-99.9% and 58.0%-97.9%, respectively. When lactate was amended, the Fe(III) reduction rate varied greatly among different paddy soils. For the paddy soils from Hunan and Zhejiang, the Fe(III) reduction rate during flooding period could reach 87.1%-100%; while for other soils, it was 5.0%-49.4% in the first 5 days of flooding and 52.2%-99.9% in 12 days after flooding. When acetate was used as a carbon source, the Fe(III) reduction rate increased with flooding time. Especially in the paddy soil from Zhejiang, the Fe(III) reduction rate changed greatly from 5.3% to 75.8%.

Hong A.,Northwest University, China | Hong A.,Clark University | Tao M.,Worcester Polytechnic Institute | Kudrolli A.,Clark University
Physics of Fluids | Year: 2015

We investigate the erosion threshold of a granular bed driven by a fluid flow as a function of grain size and grain roughness. Experiments are performed with a bed in an enclosed cylindrical channel under laminar flow conditions. The shear rate at threshold for a prescribed flow rate is obtained from the height of the fluid above the bed as it comes to rest, and used along with the grain size to determine the particle Reynolds number Rep. We estimate that the shear lift force acting on the granular surface is negligible over the range of Rep investigated. We calculate the critical Shields number θc given by the ratio of the viscous shear stress and the normal gravitation and buoyancy stresses at the threshold of motion. We find that bed armoring leads to a systematic significant increase in θc independent of the grain roughness. This observed increase is of the same order of magnitude as scatter reported in the literature when ?c is drawn from different data sets. While comparing similarly prepared beds with increasing particle size, we find that θc decreases systematically with Rep, in contrast with the Shields curve which is constant at low Rep. In order to understand the condition at erosion threshold, we use the condition of torque balance at threshold to determine the critical torque needed to dislodge grains due to viscous drag. This torque is found to be significantly lower than the value needed to dislodge a spherical grain on the bed surface which is fully exposed to a linear shear flow. However, further studies of the surface packing and its evolution are needed to fully understand the observed systematic dependence on the grain size and bed preparation. © 2015 AIP Publishing LLC.

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.

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).

Zhang L.,Northwest University, China | Merkley G.P.,Utah State University
Irrigation Science | Year: 2012

The coefficient of uniformity, CU, and the distribution uniformity, DU, are perhaps the two most common indicators of irrigation application uniformity, especially for pressurized irrigation methods. The magnitude of CU is usually greater than that of DU, but this is not the case for all data sets, as has been observed in practice by irrigation engineers and researchers. This paper describes the conditions under which CU > DU, and vice versa, proving that either situation can occur in practice. A comparison of some alternative measures of irrigation application uniformity is also compared using two data sets from agricultural sprinklers operating at different pressures. © 2011 Springer-Verlag.

Zhang R.,Nanyang Technological University | Zhang R.,Northwest University, China | Lan Y.,Nanyang Technological University | Huang G.-B.,Nanyang Technological University | Xu Z.-B.,Xian 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.

Wang C.Y.,Northwest University, China
Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban | Year: 2010

The litters of eight plant species from the Loess Plateau were cut into pieces with 2 mm and 1 cm in size, and extracted with distilled water and 0.01 mol x L(-1) CaCl2 to determine the soluble organic carbon (SOC) content. In the meantime, a 7-day indoor incubation test was conducted at (25 +/- 3) degrees C to investigate their biodegradability. The SOC content and the ratio of SOC to total carbon (SOC/TC) in the litters were 18.20-156.82 g x kg(-1) and 4.21%-32.84%, respectively. Shrub litter had a slightly higher SOC content than tree litter, while grass litter had the lowest SOC content. After 7-day incubation, the biodegradation rate of SOC in the plant litters ranged from 44.5% to 80.6% (62.9% on average), and decreased in the order of shrub > tree > grass. By the end of the incubation, the proportion of soluble organic matter in solution had a significant increasing trend, which was related to the rapid biodegradation of labile composition in the litters. The higher content and higher biodegradation rate of SOC in plant litters might play important roles in nutrient cycling and energy flow during the vegetation restoration on Loess Plateau.

Zhang S.,PLA Fourth Military Medical University | Mao T.,PLA Fourth Military Medical University | Chen F.,Northwest University, China
International Journal of Oral and Maxillofacial Surgery | Year: 2011

This study evaluated the effect of platelet-rich plasma (PRP) on the bone formation of marrow stromal cells (MSCs) in porous coral. MSCs in 50 μl of PRP were seeded into natural coral disks (diameter 8.0 mm; thickness 2.0 mm). The composites were clotted and cultured in vitro or implanted subcutaneously into nude mice. Coral scaffolds loading MSCs or PRP alone acted as control. Alkaline phosphatase (ALP) activity of the specimens cultured in vitro for 7 and 14 days was measured, and the level of ectopic bone formation was investigated 4 and 8 weeks after operation. The samples from the coral/PRP/MSC group exhibited significantly higher ALP activity, compared with that from the coral/MSC group or the coral/PRP group (p < 0.05). New bone and/or cartilage formation could be observed in specimens from both coral/PRP/MSC and coral/MSC groups in ectopic sites, and osteogenesis followed the pattern of endochondral bone formation. Histomorphometric analyses showed enhanced cartilage and/or bone formation in the coral/PRP/MSC group, 4 and 8 weeks after implantation. No bone or cartilage formation could be observed in the coral/PRP group. The authors concluded that PRP could improve the ALP activity of MSCs on coral and increase ectopic bone formation. © 2011 International Association of Oral and Maxillofacial Surgeons.

Xu J.,Northwest University, China
International Journal of Modern Physics B | Year: 2015

We investigate the lazy states, entangled states and discordant states for 2-qubit systems. We show that many lazy states are discordant, many lazy states are entangled, and many mixed entangled states are not lazy. With these investigations, we provide a laziness-discord-entanglement hierarchy diagram for 2-qubit quantum correlations. © 2015 World Scientific Publishing Company.

Zander M.,University of Gottingen | Chen S.,Northwest University, China | Imkampe J.,University of Gottingen | Thurow C.,University of Gottingen | Gatz C.,University of Gottingen
Molecular Plant | Year: 2012

Glutaredoxins are small heat-stable oxidoreductases that transfer electrons from glutathione (GSH) to oxidized cysteine residues, thereby contributing to protein integrity and regulation. In Arabidopsis thaliana, floral glutaredoxins ROXY1 and ROXY2 and pathogen-induced ROXY19/GRX480 interact with bZIP transcription factors of the TGACG (TGA) motif-binding family. ROXY1, ROXY2, and TGA factors PERIANTHIA, TGA9, and TGA10 play essential roles in floral development. In contrast, ectopically expressed ROXY19/GRX480 negatively regulates expression of jasmonic acid (JA)/ethylene (ET)-induced defense genes through an unknown mechanism that requires clade II transcription factors TGA2, TGA5, and/or TGA6. Here, we report that at least 17 of the 21 land plant-specific glutaredoxins encoded in the Arabidopsis genome interact with TGA2 in a yeast-two-hybrid system. To investigate their capacity to interfere with the expression of JA/ET-induced genes, we developed a transient expression system. Activation of the ORA59 (OCTADECANOID-RESPONSIVE ARABIDOPSIS AP2/ERF-domain protein 59) promoter by transcription factor EIN3 (ETHYLENE INSENSITVE 3) was suppressed by co-expressed ROXY19/GRX480. Suppression depended on the L**LL motif in the C-terminus of ROXY19/GRX480. This putative protein interaction domain was recently described as being essential for the TGA/ROXY interaction. Ten of the 17 tested ROXY proteins suppressed ORA59 promoter activity, which correlated with the presence of the C-terminal ALWL motif, which is essential for ROXY1 function in flower development. ROXY19/GRX480-mediated repression depended on the GSH binding site, suggesting that redox modification of either TGA factors or as yet unknown target proteins is important for the suppression of ORA59 promoter activity. The Author 2011. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.2011 © The Author 2011. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.

Lee S.-J.,Korea Institute for Advanced Study | Wang Z.-L.,Korea Institute for Advanced Study | Wang Z.-L.,Northwest University, China | Yi P.,Korea Institute for Advanced Study
Journal of High Energy Physics | Year: 2014

We count Higgs "phase" BPS states of general non-Abelian quiver, possibly with loops, by mapping the problem to its Abelian, or toric, counterpart and imposing Weyl invariance later. Precise Higgs index computation is particularly important for quivers with superpotentials; the Coulomb "phase" index is recently shown to miss important BPS states, dubbed intrinsic Higgs states or quiver invariants. We demonstrate how the refined Higgs index is naturally decomposed to a sum over partitions of the charge. We conjecture, and show in simple cases, that this decomposition expresses the Higgs index as a sum over a set of partition-induced Abelian quivers of the same total charge but generically of smaller rank. Unlike the previous approach inspired by a similar decomposition of the Coulomb index, our formulae compute the quiver invariants directly, and thus offer a self-complete routine for counting BPS states.

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.

Wu G.,Northwest University, China
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2016

We introduce a radially polarized partially coherent twisted beam based on the unified theory of coherence and polarization. We also derive expressions of this beam propagating in free space and examine the influence of twist factor and coherence of the source plane on its propagation properties. It is found that both twist factor and coherence of the source plane affect its average intensity, polarization, and coherence. Those results also show that the beam is rotating with beam propagation, and the beam's rotation is independent of coherence of the source plane. © 2016 Optical Society of America.

Liu M.,Northwest University, China
Proceedings - 2011 International Conference of Information Technology, Computer Engineering and Management Sciences, ICM 2011 | Year: 2011

Computer-mediated Communication (CMC) systems in language teaching and learning refers to the net-based computer systems which offers opportunities for group communication such as Newsgroups, E-mail conferencing, Internet Relay Chat, Bulletin Board System and Virtual Classrooms through which collaborative activities such as discussions, debates, games/simulations, role-plays, case studies, etc. can be performed. CMC creates an excellent environment for a group of people to construct knowledge together by cooperating, comparing, evaluating and reflecting on their own views and those of others. Because of the above mentioned advantages, the collaborative learning model was implemented in English teaching in the author's university. After two years' experimental teaching, a quantitative study and a qualitative study were conducted to evaluate the effectiveness of the new teaching method through students' final examination results of the 4 semesters from 2008 and 2009 and a carefully designed questionnaire. The result shows that CMC collaborative class is more effective than traditional class, in that students in CMC class have made consistent progress, have stronger learning motivation, more learning interests and develop more cooperative learning ability. © 2011 IEEE.

Wei M.,Northwest University, China | Song M.,Chinese Academy of Sciences | Fan S.,Chinese Academy of Sciences | Yu S.,Chinese Academy of Sciences
BMC Genomics | Year: 2013

Background: Cotton (Gossypium hirsutum) anther development involves a diverse range of gene interactions between sporophytic and gametophytic tissues. However, only a small number of genes are known to be specifically involved in this developmental process and the molecular mechanism of the genetic male sterility (GMS) is still poorly understand. To fully explore the global gene expression during cotton anther development and identify genes related to male sterility, a digital gene expression (DGE) analysis was adopted. Results: Six DGE libraries were constructed from the cotton anthers of the wild type (WT) and GMS mutant (in the WT background) in three stages of anther development, resulting in 21,503 to 37,352 genes detected in WT and GMS mutant anthers. Compared with the fertile isogenic WT, 9,595 (30% of the expressed genes), 10,407 (25%), and 3,139 (10%) genes were differentially expressed at the meiosis, tetrad, and uninucleate microspore stages of GMS mutant anthers, respectively. Using both DGE experiments and real-time quantitative RT-PCR, the expression of many key genes required for anther development were suppressed in the meiosis stage and the uninucleate microspore stage in anthers of the mutant, but these genes were activated in the tetrad stage of anthers in the mutant. These genes were associated predominantly with hormone synthesis, sucrose and starch metabolism, the pentose phosphate pathway, glycolysis, flavonoid metabolism, and histone protein synthesis. In addition, several genes that participate in DNA methylation, cell wall loosening, programmed cell death, and reactive oxygen species generation/scavenging were activated during the three anther developmental stages in the mutant. Conclusions: Compared to the same anther developmental stage of the WT, many key genes involved in various aspects of anther development show a reverse gene expression pattern in the GMS mutant, which indicates that diverse gene regulation pathways are involved in the GMS mutant anther development. These findings provide the first insights into the mechanism that leads to genetic male sterility in cotton and contributes to a better understanding of the regulatory network involved in anther development in cotton. © 2013 Wei et al; licensee BioMed Central 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.

Qu K.X.,Northwest University, China
Genetics and molecular research : GMR | Year: 2012

We examined the cytogenetics of mithun (Bos frontalis), a domesticated version of the Asian gaur, and hybrids (F(1) generation) produced by artificial insemination of Brahman cows (Bos indicus) with mithun semen. Reproductive potential was also examined in the F(1) generation and a backcrossed heifer for utilization of heterosis. Metaphase chromosome spreads were examined by conventional staining and fluorescence in situ hybridization hybridized with the entire chromosome 1 of mithun as a specific probe. Chromosome 1 of mithun was found to be equivalent to Bos taurus chromosomes 2 and 28. The karyotype of the female mithun (N = 4) comprised 58 chromosomes, including 54 acrocentric and four large submetacentric chromosomes, without the four acrocentric chromosomes found in the domesticated species B. indicus. However, one of the four female mithuns with a normal mithun phenotype had an abnormal karyotype (2n = 59), indicating introgression from B. taurus or B. indicus. The F(1) karyotypes (N = 6, 3♂3♀) of the mithun bull × Brahman cow cross had 2n = 59, intermediate between their parents; they were consistent heterozygous carriers with a centric fusion involving rob(2;28), as expected. Two pronounced red signals were seen in the mithun karyotypes, three red signals in the mithun × Brahman hybrids, and four red signals in the Brahman cattle, in good agreement with centric fusion of bovine rob(2;28). The female backcross hybrid (N = 1) with 2n = 59 had a similar chromosome configuration to the F(1) karyotypes and had rob(2;28). Such female backcross hybrids normally reproduce; however, the F(1) bulls (N = 3) had not yet generated normal sperm at 24 months.

Li X.,Northwest University, China | Zhang L.,Northwestern Polytechnical University | Yin X.,Northwestern Polytechnical University
Journal of the European Ceramic Society | Year: 2013

Pyrolytic carbon-Si3N4 ceramics (PyC-Si3N4) with gradient PyC distribution (Gradient-PyC-Si3N4) is fabricated by directional oxidation. After directional oxidation for 1.0h, the electromagnetic absorptivity of Gradient-PyC-Si3N4 increases significantly from 0.8 to 50.1% with the obvious reduction of electromagnetic reflectivity from 99.2 to 43.8%. The Gradient-PyC-Si3N4 is a good electromagnetic absorbing material meeting the requirement of self-concealing technology. © 2012 Elsevier Ltd.

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.

Cheng S.-G.,Northwest University, China
Journal of Physics Condensed Matter | Year: 2010

Recent experiments have confirmed that the electron-hole inhomogeneity in graphene is a new type of charge disorder. Motivated by such confirmation, we theoretically study the transport properties of a monolayer graphene (MLG) based p-n junction and a bilayer graphene (BLG) p-n junction in the quantum Hall regime where electron-hole puddles are considered. By using the non-equilibrium Green function method, both the current and conductance are obtained. We find that, in the presence of the electron-hole inhomogeneity, the lowest quantized conductance plateau at e2/h emerges in the MLG p-n junction under very small charge puddle disorder strength. For a BLG p-n junction, however, the conductance in the p-n region is enhanced with charge puddles, and the lowest quantized conductance plateau emerges at 2e2/h. Besides, when an ideal quantized conductance plateau is formed for a MLG p-n junction, the universal conductance fluctuation is found to be 2e2/3h. Furthermore, we also investigate the influence of Anderson disorder on such p-n junctions and the comparison and discussion are given accordingly. To compare the two models with different types of disorder, we investigate the conductance distribution specially. Finally the influence of disorder strength on the conductance of a MLG p-n junction is investigated. © 2010 IOP Publishing Ltd.

Trost B.M.,Stanford University | Luan X.,Stanford University | Luan X.,Northwest University, China
Nature Protocols | Year: 2012

This protocol describes a new approach for the preparation of ±-allylated α,β-unsaturated carbonyl compound by chemoselective cross-coupling of propargyl alcohols with allyl carbonates using an unprecedented vanadium/palladium contemporaneous dual catalysis. This process involves 1,3-transposition of propargyl alcohols by an oxyvanadium catalyst to generate vanadium allenoates and the activation of allyl carbonates by a palladium catalyst to generate π-allylpalladium species. These two active intermediates trap each other more rapidly to afford the observed product, rather than being intercepted by the large excess of starting propargyl alcohol. One example for the preparation of this type of α-allylated ±,β-unsaturated carbonyl compound is included in the text. It takes ∼20 h to complete the protocol: 1.0 h to set up the reaction, 16 h for the reaction and 2.0 h for isolation and purification. This chemistry has been applied to obtain a wide range of α-allylated α,β-unsaturated ketones, esters and amides, which are highly valuable building blocks in organic synthesis. © 2012 Nature America, Inc. All rights reserved.

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.

Liu J.-Q.,Guangdong Medical College | Jia Z.-B.,Guangdong Medical College | Wang Y.-Y.,Northwest University, China
Journal of Molecular Structure | Year: 2011

Three new coordination polymers, namely, {[Cd3(L 1)2(IP)2(H2O)4]} n (1), {[Cd2(L2)2(IP) 2]·(CH3OH)(DMF)}n (2) and [Cd(L 3)(IP)]n (3) (H3L1 = benzene-1,2,4-tricarboxylic acid, H2L2 = 2,2-bis(4-carboxyphenyl)hexafluoropropane, H2L3 = 1,3-phenylenediacetic acid and IP = 1H-imidazo[4,5-f][1,10]-phenanthroline), were prepared via self-assembly of pharmaceutical agent IP with cadmium sulfate in the presence of the different backbones of carboxylate linkers under mild conditions. All the polymers possess 2D structural motifs. The rigid tricarboxylate ligand links the metal centers to form a tetranuclear core in 1. In 2, the 2D network with trinuclear cores is further extended into 3D supramolecular arrays through aromatic stacking interactions. Interestingly, IP ligand acts in a tridentate mode via the two N atoms of pyridyl rings and the third N atom of imidazole ring and connects metal atoms into 1D zigzag chain in 3. The structural analysis reveals that the backbones of carboxylates have critical effect on the construction of the complexes. Solid-state luminescent spectra of the Cd(II) complexes indicate intense fluorescent emissions. © 2010 Elsevier B.V. All rights reserved.

Song L.,Xian University of Arts and Science | Gao J.,Northwest University, China
Journal of Molecular Structure | Year: 2013

The two dinuclear rare earth complexes Eu2(PBa) 6(Phen)2 and Tb2(PBa)6(Phen) 2, (where PBa = 4-pentylbenzoate group and Phen = 1, 10-phenanthroline), were synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Both of them crystallize in space group P-1 with similar cell parameters. Each Eu or Tb ion is nine-coordinated with one 1, 10-phenanthroline molecule, one bidentate chelating carboxylate group, two bidentate bridging carboxylate groups, and two tridentate bridging carboxylate groups. The fluorescent properties of the europium and terbium complexes were also investigated. Under the UV excitation, the two complexes exhibit extensive characteristic emissions of europium and terbium ions, respectively. © 2012 Elsevier B.V. All rights reserved.

Chen V.L.,Harvard University | Surana N.K.,Harvard University | 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 L.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Dong Z.H.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Wang Z.G.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Zhang F.X.,Northwest University, China | Jin J.,CAS Suzhou Institute of Nano Technology and Nano Bionics
Advanced Functional Materials | Year: 2013

The effect of space accessible to electrolyte ions on the electrochemical activity is studied for a system of transition-metal hydroxide-based pseudocapacitors. Layered α-Co(OH)2 with various intercalated anions is used as a model material. Three types of layered α-Co(OH) 2 with intercalated anions of dodecyl sulfate, benzoate, or nitrate, are prepared by a simple reflux and an anion-exchange process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations and X-ray diffraction (XRD) data show the formation of layered α-Co(OH) 2 nanocones with interlayer spacing between adjacent Co(OH) 2 single sheets of 1.6, 0.7, and 0.09 nm, corresponding to the anions as listed above. Electrochemical characterization reveals that interlayer space has a great effect on the electrochemical activity of α-Co(OH) 2 nanocones as an electrode material. For the interlayer spacing of 1.6 nm, in the case of dodecyl sulfate-intercalated α-Co(OH)2, the Faradaic reaction takes place more adequately than for benzoate- and nitrate-intercalated α-Co(OH)2. As a result, a higher specific capacitance and better cycling stability is obtained for the dodecyl sulfate-intercalated α-Co(OH)2. The electrochemical activity obviously reduces when the interlayer space decreases to 0.7 nm. Our results suggest the importance of rational designing the interlayer space of layered transition metal hydroxides for high-performance pseudocapacitors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xu J.,Northwest University, China
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

Coherence arises from the superposition principle and plays a key role in quantum mechanics. Recently, Baumgratz et al. [T. Baumgratz, M. Cramer, and M. B. Plenio, Phys. Rev. Lett. 113, 140401 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.140401] established a rigorous framework for quantifying the coherence of finite-dimensional quantum states. In this work we provide a framework for quantifying the coherence of Gaussian states and explicitly give a coherence measure for Gaussian states based on the relative entropy. © 2016 American Physical Society.

Liu J.-R.,Northwest University, China
Modern Physics Letters B | Year: 2016

Multi-wave resonant solutions of a class of nonlinear heat-type equations are investigated by their corresponding generalized bilinear equations. We develop a new technique for searching for resonant solutions to those generalized bilinear equations, using the idea of weights of dependent variables. The results show that generalized bilinear operators and generalized bilinear equations are powerful and irreplaceable tools for dealing with nonlinear differential equations. © 2016 World Scientific Publishing Company.