Lanzhou, China
Lanzhou, China

Lanzhou University is a major research university in Lanzhou, Gansu Province, China. Founded in 1909, it is one of the key universities under China's Ministry of Education . It provides programs for undergraduate, graduate students on four campuses—three in Lanzhou city centre and one in Yuzhong County, about 30 miles away from the main campus. Total enrolment is approximately 20,000. Undergraduate students study at the Yuzhong campus. There are 6 National Bases for the Training of Researching and Teaching personnel for Fundamental Disciplines. The University operates an additional 35 institutes along with 1 national key Laboratory of the Applied Organic and 3 key laboratories of Arid and Grassland Ecology, West China Environment, Magnetism and Magnetic Materials of the Ministry of Education, a key laboratory of Grassland Agro-ecosystem of the Ministry of Agriculture. Lanzhou University was one of the first universities entitled to enroll Bachelor Master’s and Doctoral degree candidates in 1981. Lanzhou University is one of the top ten universities in contributions to academic publications in international journals frequently cited by ongoing research from around the world. Wikipedia.

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Wang Z.,Northwestern Polytechnical University | Wang Z.,Kyushu University | Andrews M.A.,University of Guelph | Wu Z.-X.,Lanzhou University | And 2 more authors.
Physics of Life Reviews | Year: 2015

It is increasingly recognized that a key component of successful infection control efforts is understanding the complex, two-way interaction between disease dynamics and human behavioral and social dynamics. Human behavior such as contact precautions and social distancing clearly influence disease prevalence, but disease prevalence can in turn alter human behavior, forming a coupled, nonlinear system. Moreover, in many cases, the spatial structure of the population cannot be ignored, such that social and behavioral processes and/or transmission of infection must be represented with complex networks. Research on studying coupled disease-behavior dynamics in complex networks in particular is growing rapidly, and frequently makes use of analysis methods and concepts from statistical physics. Here, we review some of the growing literature in this area. We contrast network-based approaches to homogeneous-mixing approaches, point out how their predictions differ, and describe the rich and often surprising behavior of disease-behavior dynamics on complex networks, and compare them to processes in statistical physics. We discuss how these models can capture the dynamics that characterize many real-world scenarios, thereby suggesting ways that policy makers can better design effective prevention strategies. We also describe the growing sources of digital data that are facilitating research in this area. Finally, we suggest pitfalls which might be faced by researchers in the field, and we suggest several ways in which the field could move forward in the coming years. © 2015 Elsevier B.V..

Chen H.-X.,Beijing University of Technology | Chen H.-X.,Beihang University | Chen W.,University of Saskatchewan | Liu X.,Lanzhou University | And 2 more authors.
Physics Reports | Year: 2016

In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like Zc states and bottomonium-like Zb states cannot be accommodated within the naive quark model. These charged Zc states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states. © 2016 Elsevier B.V..

Li X.,Samuel Roberts Noble Foundation | Wang X.,Lanzhou University | Wei Y.,Samuel Roberts Noble Foundation | Brummer E.C.,Samuel Roberts Noble Foundation
Theoretical and Applied Genetics | Year: 2011

Segregation distortion (SD) is often observed in plant populations; its presence can affect mapping and breeding applications. To investigate the prevalence of SD in diploid alfalfa (Medicago sativa L.), we developed two unrelated segregating F 1 populations and one F 2 population. We genotyped all populations with SSR markers and assessed SD at each locus in each population. The three maps were syntenic and largely colinear with the Medicago truncatula genome sequence. We found genotypic SD for 24 and 34% of markers in the F 1 populations and 68% of markers in the F 2 population; distorted markers were identified on every linkage group. The smaller percentage of genotypic SD in the F 1 populations could be because they were non-inbred and/or due to non-fully informative markers. For the F 2 population, 60 of 90 mapped markers were distorted, and they clustered into eight segregation distortion regions (SDR). Most SDR identified in the F 1 populations were also identified in the F 2 population. Genotypic SD was primarily due to zygotic rather than allelic distortion, suggesting zygotic not gametic selection is the main cause of SD. On the F 2 linkage map, distorted markers in all SDR except two showed heterozygote excess. The severe SD in the F 2 population likely biased genetic distances among markers and possibly also marker ordering and could affect QTL mapping of agronomic traits. To reduce the effects of SD and non-fully informative markers, we suggest constructing linkage maps and conducting QTL mapping in advanced generation populations. © 2011 Springer-Verlag.

Liu X.,Lanzhou University | Luo Z.-G.,Peking University | Sun Z.-F.,Lanzhou University
Physical Review Letters | Year: 2010

The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly purport to explain the newly observed X(3915) and X(4350) as new members in the P-wave charmonium family, i.e., χc0′ for X(3915) and χc2′′ for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the JPC quantum numbers of X(3915) and X(4350) must be 0++ and 2++ respectively, which provide important criteria to test the P-wave charmonium explanation for X(3915) and X(4350) proposed by this Letter. The decay behavior of the remaining two P-wave charmonium states with the second radial excitation is predicted, and an experimental search for them is suggested. © 2010 The American Physical Society.

Liu Y.,Lanzhou University
Dynamical Systems | Year: 2014

In this article, the existence of pullback attractors for a non-autonomous nonclassical diffusion equations is proved in. © 2013 © 2013 Taylor & Francis.

Wang Q.,Lanzhou University | He X.-R.,Peking University | Tian J.-H.,Lanzhou University | Yang K.-H.,Lanzhou University
Digestive Surgery | Year: 2014

Background and Objective: Several studies suggested that pancreatic stents had some benefit during pancreatoduodenectomy (PD), but others disagree. Whether pancreatic duct stents could prevent postoperative pancreatic fistula (POPF) is still under controversy. Methods: Randomized controlled trials published before November 2012 were all aggregated, focusing on the evaluation of pancreatic duct stents during PD. Trial data was reviewed and extracted independently by two reviewers. The quality of the including studies was assessed by the Cochrane handbook 5.1.0. Results: Seven studies were included, with a total of 793 patients. The results showed that compared with nonstents, stents during PD was associated with a significant difference on overall POPF rate (OR = 0.65, 95% CI 0.45-0.95, p = 0.02), POPF grades B and C (OR = 0.45, 95% CI 0.27-0.76, p = 0.003), and hospital stay (MD = -4.28, 95% CI -6.81, -1.75, p = 0.0009). Subgroup analyses showed that the external stent had a significant difference in the incidence of overall POPF (OR = 0.46, 95% CI 0.29-0.73, p = 0.0009), POPF grades B and C (OR = 0.49, 95% CI 0.30-0.79, p = 0.003), postoperative morbidity (OR = 0.63, 95% CI 0.42-0.96, p = 0.03), as well as hospital stay. Conclusions: Based upon this meta-analysis, there might be potential benefit in reducing POPF thanks to the use of pancreatic duct stents. © 2013 S. Karger AG, Basel.

Niu J.,Lanzhou University | Niu J.,Peking University | Gao H.,Lanzhou University
Journal of Luminescence | Year: 2014

Recently, nitrogen-doped carbon dots (NCDs) have attracted considerable interest since nitrogen (N) doping could effectively tailor the electronic properties and the chemical reactivity of carbon dots (CDs) for advanced potential applications. Herein, a one-step pyrolysis method was presented for synthesizing the NCDs with excellent water solubility, good stability and a high quantum yield of ca. 28%. The detection performance of NCDs for the antibacterial drugs was further explored, and it was proved to effectively enhance the fluorescence due to the strong interaction between the NCDs and antibacterial drugs. © 2014 Elsevier B.V.

Chen R.,Lanzhou University | Liu X.,Nankai University | Li X.-Q.,Beijing University of Technology | Li X.-Q.,Peking University | Zhu S.-L.,Lanzhou University
Physical Review Letters | Year: 2015

The LHCb Collaboration at the Large Hadron Collider at CERN discovered two pentaquark states Pc(4380) and Pc(4450). These two hidden-charm states are interpreted as the loosely bound Σc(2455)D∗ and Σc∗(2520)D∗ molecular states in the boson exchange interaction model, which provides an explanation for why the experimental width of Pc(4450) is much narrower than that of Pc(4380). The discovery of the new resonances Pc(4380) and Pc(4450), indeed, opens a new page for hadron physics. The partners of Pc(4380) and Pc(4450) should be pursued in future experiments. © 2015 American Physical Society.

Chen H.-X.,Beihang University | Chen W.,University of Saskatchewan | Liu X.,Lanzhou University | Steele T.G.,University of Saskatchewan | And 2 more authors.
Physical Review Letters | Year: 2015

Inspired by Pc(4380) and Pc(4450) recently observed by LHCb, a QCD sum rule investigation is performed, by which they can be identified as exotic hidden-charm pentaquarks composed of an anticharmed meson and a charmed baryon. Our results suggest that Pc(4380) and Pc(4450) have quantum numbers JP=3/2- and 5/2+, respectively. Furthermore, two extra hidden-charm pentaqurks with configurations D¯Σc∗ and D¯∗Σc∗ are predicted, which have spin-parity quantum numbers JP=3/2- and JP=5/2+, respectively. As an important extension, the mass predictions of hidden-bottom pentaquarks are also given. Searches for these partners of Pc(4380) and Pc(4450) are especially accessible at future experiments like LHCb and BelleII. © 2015 American Physical Society.

Ma L.,Peking University | Liu X.-H.,Peking University | Liu X.,Lanzhou University | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Through the spin rearrangement scheme in the heavy quark limit, we have performed a comprehensive investigation of the decay pattern and production mechanism of the hidden beauty dimeson states, which are either composed of a P-wave bottom meson and an S-wave bottom meson or two S-wave bottom mesons. We further extend the corresponding formula to discuss the decay behavior of some charmonium-like states by combining the experimental information with our numerical results. The typical ratios presented in this work can be measured by future experiments like BESIII, Belle, LHCb and the forthcoming BelleII, which shall provide important clues to the inner structures of the exotic states. © 2015 American Physical Society.

Wang Z.-Y.,King Abdullah University of Science and Technology | Wang Z.-Y.,Lanzhou University | Xiong L.,King Abdullah University of Science and Technology | Li W.,University of California at Riverside | And 3 more authors.
Plant Cell | Year: 2011

Osmotic stress activates the biosynthesis of abscisic acid (ABA). One major step in ABA biosynthesis is the carotenoid cleavage catalyzed by a 9-cis epoxycarotenoid dioxygenase (NCED). To understand the mechanism for osmotic stress activation of ABA biosynthesis, we screened for Arabidopsis thaliana mutants that failed to induce the NCED3 genee xpression in response to osmotic stress treatments. The ced1 (for 9-cis epoxycarotenoid dioxy genase defective 1) mutant isolated in this study showed markedly reduced expression of NCED3 in response to osmotic stress (polyethylene glycol)treatments compared with the wild type. Other ABA biosynthesis genes are also greatly reduced in ced1 under osmotic stress. ced1 mutant plants are very sensitive to even mild osmotic stress. Map-based cloning revealed unexpectedly thatCED1 encodes a putative a/b hydrolase domain-containing protein and is allelic to the BODYGUARD gene that was recently shown to be essential for cuticle biogenesis. Further studies discovered that other cut in biosynthesis mutants are also impaired in osmotic stress induction of ABA biosynthesis genes and are sensitive to osmotic stress. Our work demonstrates that the cuticle functions not merely as a physical barrier to minimize water loss but also mediates osmotic stress signaling and tolerance by regulating ABA biosynthesis and signaling. © 2011 American Society of Plant Biologists. All rights reserved.

Xia X.,Peking University | Song S.,Peking University | Niu Y.,Lanzhou University | Niu Y.,Durham University
Chemical Geology | Year: 2012

A tholeiite-boninite terrane occurs as a ~. 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower tholeiite unit and the upper boninite unit. The lower tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5-6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380-1460. °C at depths of 42-66. km and involvement of slab-derived hydrous fluids/melts. Zircon U-Pb SHRIMP dating shows that lower tholeiite magmatism lasted for at least 12. M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) tholeiite-boninite terrane. The lower tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively "dry" and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB tholeiite-boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma. © 2011 Elsevier B.V.

Zhang J.,Lanzhou University | Tian W.,Lanzhou University | Wang Z.,Lanzhou University | Xie F.,Beijing Normal University | Wang F.,Lanzhou University
Journal of Climate | Year: 2015

The influence of El Niño-Southern Oscillation (ENSO) on northern midlatitude ozone during the period January-March (JFM) is investigated using various observations and a chemistry-climate model. The analysis reveals that, during El Niño events, there are noticeable anomalously high total ozone column (TOC) values over the North Pacific, the southern United States, northeastern Africa, and East Asia but anomalously low values in central Europe and over the North Atlantic. La Niña events have almost the opposite effects on TOC anomalies. The longitudinal dependence of midlatitude ozone anomalies associated with ENSO events during the period JFM is found to be related to planetary waves. Planetary waves excited by tropical convection propagate into the middle latitudes and give rise to longwave trains (Pacific-North American pattern) and shortwave trains along the North African-Asian jet. These wave trains affect ozone in the upper troposphere and lower stratosphere (UTLS) by modulating the midlatitude tropopause height and cause TOC anomalies by changing the vertical distributions of ozone. In addition, synoptic-scale Rossby wave breaking increases on the poleward flanks of the enhanced westerly jet during El Niño events, leading to a stronger eddy-driven meridional circulation in the UTLS and hence causing TOC increases over the North Pacific, the southern United States, northeastern Africa, and East Asia and vice versa for La Niña events. It is also found that the contribution of changes in Brewer-Dobson circulation due to anomalous planetary wave dissipation in the stratosphere during ENSO events to TOC changes in the middle latitudes for the period JFM is small, not more than 1 Dobson unit (DU) per month. © 2015 American Meteorological Society.

Michalet R.,University of Bordeaux 1 | Xiao S.,University of Bordeaux 1 | Xiao S.,Lanzhou University | Touzard B.,University of Bordeaux 1 | And 2 more authors.
Ecology Letters | Year: 2011

Much is known about facilitation, but virtually nothing about the underlying genetic and evolutionary consequences of this important interaction. We assessed the potential of phenotypic differences in facilitative effects of a foundation species to determine the composition of an Alpine community in Arizona. Two phenotypes of Geum rossii occur along a gradient of disturbance, with 'tight' competitive cushions in stable conditions and 'loose' facilitative cushions in disturbed conditions. A common-garden study suggested that field-based traits may have a genetic basis. Field experiments showed that the reproductive fitness of G. rossii cushions decreased with increasing facilitation. Finally, using a dual-lattice model we showed that including the cost and benefit of facilitation may contribute to the co-occurrence of genotypes with contrasting facilitative effects. Our results indicate that changes in community composition due to phenotypic differences in facilitative effects of a foundation species may in turn affect selective pressures on the foundation species. © 2011 Blackwell Publishing Ltd/CNRS.

Liu Y.,Peking University | Zhang L.,Peking University | Jia Y.,Peking University | Jia Y.,Lanzhou University
Tetrahedron Letters | Year: 2012

The total synthesis of maremycins A, B, C 1/C 2, D 1, and D 2 is achieved starting from the natural amino acids l-isoleucine and S-methyl-l-cysteine, in which the total synthesis of maremycins B, C 1/C 2, and D 2 is accomplished for the first time. The synthesis features a position-selective intramolecular bromination process for the synthesis of key chiral building block, a Pd-catalyzed indole synthesis for the preparation of (2S,3S)-β- methyltryptophan and hydroxylation of oxindoles by molecular oxygen. In addition, the protocol for conversion of maremycins A and B to maremycins C and D was improved. © 2011 Elsevier Ltd. All rights reserved.

Tao P.,Peking University | Jia Y.,Peking University | Jia Y.,Lanzhou University
Chemical Communications | Year: 2014

The rhodium(iii)-catalyzed intramolecular annulation of alkyne-tethered acetanilides for the synthesis of fused tricyclic indole scaffolds via C-H activation has been developed, which has the potential for the synthesis of many indole alkaloids. This reaction proceeds under mild reaction conditions and with tolerance to a variety of functional groups. © 2014 the Partner Organisations.

Yuan B.-C.,Beijing Normal University | Yue D.-X.,Lanzhou University
Pedosphere | Year: 2012

Successional and seasonal effects on soil microbial and enzymatic properties were studied in Chinese pine (Pinus tabulaeformis) plantations in an age sequence of 3-, 7-, 13-, 21- and 28-year-old in northern Ziwuling region in the middle of Loess Plateau, China. The results indicated that plantation age and season affected soil microbial and enzymatic parameters significantly. Soil organic C, total N, microbial biomass C, microbial quotient, basal respiration, dehydrogenase, N-α-benzoyl-L-argininamide (BAA)-protease, urease and β-glucosidase increased quickly and tended to be highest at PF21 (21-year plantation), thereafter they remained nearly at a constant level, whereas the metabolic quotient (qCO 2) showed an initial increase and then decreased gradually. Measures of these soil properties showed significant seasonal fluctuations except for organic C and total N, which were found to be relatively stable throughout the study period, and the seasonal distributions were autumn > spring > summer > winter for microbial biomass C, microbial quotient, dehydrogenase, and β-glucosidase; autumn > summer > spring > winter for BAA-protease and urease; and summer > autumn > spring > winter for basal respiration and qCO 2. Significant season × age interaction was observed for biomass C, basal respiration, dehydrogenase and BAA-protease. © 2012 Soil Science Society of China.

Zhang Y.-A.,Peking University | Liu Q.,Peking University | Wang C.,Peking University | Jia Y.,Peking University | Jia Y.,Lanzhou University
Organic Letters | Year: 2013

A concise total synthesis of rugulovasine A is achieved by using Uhle's ketone derivative as the key intermediate, which was synthesized by intramolecular cyclization via metal-halogen exchange. Two different routes to construct a spirocyclic butyrolactone subunit involving a Ru-catalyzed cyclocarbonylation and a special Ru-catalyzed double bond rearrangement were studied. © 2013 American Chemical Society.

Song S.,Peking University | Niu Y.,Lanzhou University | Niu Y.,Durham University | Su L.,China University of Geosciences | Xia X.,Peking University
Gondwana Research | Year: 2013

The Qilian Orogen at the northern margin of the Tibetan Plateau is a type suture zone that recorded a complete history from continental breakup to ocean basin evolution, and to the ultimate continental collision in the time period from the Neoproterozoic to the Paleozoic. The Qilian Ocean, often interpreted as representing the "Proto-Tethyan Ocean", may actually be an eastern branch of the worldwide "Iapetus Ocean" between the two continents of Baltica and Laurentia, opened at ≥. 710. Ma as a consequence of breakup of supercontinent Rodinia. Initiation of the subduction in the Qilian Ocean probably occurred at ~ 520. Ma with the development of an Andean-type active continental margin represented by infant arc magmatism of ~ 517-490 Ma. In the beginning of Ordovician (~ 490. Ma), part of the active margin was split from the continental Alashan block and the Andean-type active margin had thus evolved to western Pacific-type trench-arc-back-arc system represented by the MORB-like crust (i.e., SSZ-type ophiolite belt) formed in a back-arc basin setting in the time period of ~ 490-445 Ma. During this time, the subducting oceanic lithosphere underwent LT-HP metamorphism along a cold geotherm of ~ 6-7. °C/km. The Qilian Ocean was closed at the end of the Ordovician (~ 445. Ma). Continental blocks started to collide and the northern edge of the Qilian-Qaidam block was underthrust/dragged beneath the Alashan block by the downgoing oceanic lithosphere to depths of ~ 100-200. km at about 435-420. Ma. Intensive orogenic activities occurred in the late Silurian and early Devonian in response to the exhumation of the subducted crustal materials. Briefly, the Qilian Orogen is conceptually a type example of the workings of plate tectonics from continental breakup to the development and evolution of an ocean basin, to the initiation of oceanic subduction and formation of arc and back-arc system, and to the final continental collision/subduction and exhumation. © 2012 International Association for Gondwana Research.

Li J.,Peking University | Yu J.,Peking Tsinghua Center for Life science | Zhao J.,Peking University | Wang J.,Peking Tsinghua Center for Life science | And 8 more authors.
Nature Chemistry | Year: 2014

Employing small molecules or chemical reagents to modulate the function of an intracellular protein, particularly in a gain-of-function fashion, remains a challenge. In contrast to inhibitor-based loss-of-function approaches, methods based on a gain of function enable specific signalling pathways to be activated inside a cell. Here we report a chemical rescue strategy that uses a palladium-mediated deprotection reaction to activate a protein within living cells. We identify biocompatible and efficient palladium catalysts that cleave the propargyl carbamate group of a protected lysine analogue to generate a free lysine. The lysine analogue can be genetically and site-specifically incorporated into a protein, which enables control over the reaction site. This deprotection strategy is shown to work with a range of different cell lines and proteins. We further applied this biocompatible protection group/catalyst pair for caging and subsequent release of a crucial lysine residue in a bacterial Type III effector protein within host cells, which reveals details of its virulence mechanism. © 2014 Macmillan Publishers Limited.

Qin H.,Peking University | Xu Z.,Peking University | Cui Y.,Peking University | Jia Y.,Lanzhou University
Angewandte Chemie - International Edition | Year: 2011

A photo op: The concise total syntheses of (±)-decursivine and (±)-serotobenine were achieved by using the titled cascade reaction, which is modeled on the biomimetic pathway. The synthesis of (±)-decursivine, which exhibits antimalarial activity, was carried out in five steps without using protecting groups. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li H.,Peking University | Liu J.,Peking University | Sun C.-L.,Peking University | Li B.-J.,Peking University | And 2 more authors.
Organic Letters | Year: 2011

The most efficient method to construct biaryls is the direct dehydrogenative cross-coupling of two different aromatic rings. Such an ideal cross arylation starting from distinct polyfluoroarenes and simple arenes was presented. The selectivity of the cross-coupling was controlled by both of the electronic property of fluoroarenes and steric hindrance of simple arenes. Diisopropyl sulfide was essential to promote the efficacy. © 2010 American Chemical Society.

Li J.,Peking University | Lin S.,Peking University | Wang J.,Peking University | Jia S.,Peking University | And 5 more authors.
Journal of the American Chemical Society | Year: 2013

Palladium, a key transition metal in advancing modern organic synthesis, mediates diverse chemical conversions including many carbon-carbon bond formation reactions between organic compounds. However, expanding palladium chemistry for conjugation of biomolecules such as proteins, particularly within their native cellular context, is still in its infancy. Here we report the site-specific protein labeling inside pathogenic Gram-negative bacterial cells via a ligand-free palladium-mediated cross-coupling reaction. Two rationally designed pyrrolysine analogues bearing an aliphatic alkyne or an iodophenyl handle were first encoded in different enteric bacteria, which offered two facial handles for palladium-mediated Sonogashira coupling reaction on proteins within these pathogens. A GFP-based bioorthogonal reaction screening system was then developed, allowing evaluation of both the efficiency and the biocompatibilty of various palladium reagents in promoting protein-small molecule conjugation. The identified simple compound-Pd(NO3) 2 exhibited high efficiency and biocompatibility for site-specific labeling of proteins in vitro and inside living E. coli cells. This Pd-mediated protein coupling method was further utilized to label and visualize a Type-III Secretion (T3S) toxin-OspF in Shigella cells. Our strategy may be generally applicable for imaging and tracking various virulence proteins within Gram-negative bacterial pathogens. © 2013 American Chemical Society.

Chen F.H.,Lanzhou University | Dong G.H.,Lanzhou University | Zhang D.J.,Lanzhou University | Liu X.Y.,Washington University in St. Louis | And 9 more authors.
Science | Year: 2015

Our understanding of when and how humans adapted to living on the Tibetan Plateau at altitudes above 2000 to 3000 meters has been constrained by a paucity of archaeological data. Here we report data sets from the northeastern Tibetan Plateau indicating that the first villages were established only by 5200 calendar years before the present (cal yr B.P.). Using these data, we tested the hypothesis that a novel agropastoral economy facilitated year-round living at higher altitudes since 3600 cal yr B.P. This successful subsistence strategy facilitated the adaptation of farmers-herders to the challenges of global temperature decline during the late Holocene. © 2015 American Association for the Advancement of Science. All right reserved.

Qi J.,Lanzhou University | Qi J.,University of California at Riverside | Olmedo M.,University of California at Riverside | Ren J.,University of California at Riverside | And 5 more authors.
ACS Nano | Year: 2012

Resistive memory is one of the most promising candidates for next-generation nonvolatile memory technology due to its variety of advantages, such as simple structure and low-power consumption. Bipolar resistive switching behavior was observed in epitaxial ZnO nanoislands with base diameters and heights ranging around 30 and 40 nm, respectively. All four different states (initial, electroformed, ON, and OFF) of the nanoscale resistive memories were measured by conductive atomic force microscopy immediately after the voltage sweeping was performed. Auger electron spectroscopy and other experiments were also carried out to investigate the switching mechanism. The formation and rupture of conducting filaments induced by oxygen vacancy migration are responsible for the resistive switching behaviors of ZnO resistive memories at the nanoscale. © 2012 American Chemical Society.

Guo L.,Peking University | Zhang F.,Peking University | Hu W.,Peking University | Li L.,Peking University | And 2 more authors.
Chemical Communications | Year: 2014

A new palladium-catalyzed method for the synthesis of benzofurans by reaction of 2-hydroxystyrenes and iodobenzenes via a C-H activation/oxidation tandem reaction has been unprecedentedly discovered. By using this strategy, the overall synthetic efficiency of the synthesis of decursivine and its analogues was indeed improved. Preliminary mechanistic studies shed light into the possible mechanisms. © The Royal Society of Chemistry 2014.

Qi J.,Lanzhou University | Olmedo M.,University of California at Riverside | Zheng J.-G.,University of California at Irvine | Liu J.,University of California at Riverside
Scientific Reports | Year: 2013

Resistive memory has attracted a great deal of attention as an alternative to contemporary flash memory. Here we demonstrate an interesting phenomenon that multimode resistive switching, i.e. threshold-like, self-rectifying and ordinary bipolar switching, can be observed in one self-assembled single-crystalline ZnO nanoisland with base diameter and height ranging around 30 and 40â€...nm on Si at different levels of current compliance. Current-voltage characteristics, conductive atomic force microscopy (C-AFM), and piezoresponse force microscopy results show that the threshold-like and self-rectifying types of switching are controlled by the movement of oxygen vacancies in ZnO nanoisland between the C-AFM tip and Si substrate while ordinary bipolar switching is controlled by formation and rupture of conducting nano-filaments. Threshold-like switching leads to a very small switching power density of 1 × 103 W/cm2.

Hu W.,Peking University | Qin H.,Peking University | Cui Y.,Peking University | Jia Y.,Peking University | Jia Y.,Lanzhou University
Chemistry - A European Journal | Year: 2013

In this article, the total syntheses of antimalarial compound decursivine and its biologically inactive sibling serotobenine are presented. The biomimetic synthesis of (±)-serotobenine was investigated first, but failed. During the subsequent investigation of other synthetic routes, we discovered a new cascade Witkop photocyclization/elimination/addition sequence, which enabled the expedient synthesis of not only racemic decursivine and serotobenine, but also enantiopure (+)- and (-)-decursivine and a variety of their analogues. The present syntheses represent the shortest pathway for the total synthesis of decursivine and serotobenine to date. Moreover, the newly developed cascade sequence for the total synthesis of decursivine does not need any protecting steps. The scope and the reaction mechanism of the cascade sequence were also studied. A rational mechanism for the cascade sequence is proposed, which is consistent with the previous studies and our current experimental results. Photomediated cascade reaction: The total synthesis of enantiopure (+)- and (-)-decursivine and (±)-serotobenine was achieved through a cascade Witkop photocyclization/elimination/addition sequence (see scheme). The scope of the cascade sequence was investigated, and a variety of analogues of decursivine were synthesized. A rational mechanism for the cascade sequence was also proposed based on current experimental results. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li J.,Shanghai University | Wang N.,Shanghai University | Li C.,Shanghai University | Jia X.,Shanghai University | Jia X.,Lanzhou University
Chemistry - A European Journal | Year: 2012

Multicomponent cycloadditions with readily available isocyanides, allenoates, and isatylidene malononitriles are disclosed. This reaction, which does not require the aid of any catalyst, allows the efficient syntheses of spirocyclic oxindoles with excellent regioselectivity. Reactions with ethyl 2,3-butadienoate and various structurally diverse α- and γ-substituted allenoates are also fully explored. Remarkably, we have shown that the usual three-component process can be further developed into an unprecedented four-component cycloaddition in the presence of water, which provides a new strategy to access highly unusual tricyclic oxindoles. From a synthetic point of view, this protocol is very interesting considering the high level of complexity reached in one step. The mechanism is thought to proceed by a triple Michael/cyclization process by using allenoate as a three carbon atom component (3 C). Furthermore, multicomponent reaction with γ-substituted allenoate also results in a very interesting conversion. In such cases, the unusual cleavage of the "C=C" double bond of isatylidene malononitrile and one of the "C=C" double bonds of allenoate is always observed. Multiply your chemistry! Multicomponent reactions with readily available isocyanides, allenoates, and isatylidene malononitriles are disclosed. This protocol provides a synthetic route to an exocyclic double bond containing a spirocyclic ring in an efficient manner with excellent regioselectivity (see scheme). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hu Y.,Peking University | Xia Y.,Peking University | Fu Q.,University of Washington | Fu Q.,Lanzhou University
Atmospheric Chemistry and Physics | Year: 2011

Recent simulations predicted that the stratospheric ozone layer will likely return to pre-1980 levels in the middle of the 21st century, as a result of the decline of ozone depleting substances under the Montreal Protocol. Since the ozone layer is an important component in determining stratospheric and tropospheric-surface energy balance, the recovery of stratospheric ozone may have significant impact on tropospheric-surface climate. Here, using multi-model results from both the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4) models and coupled chemistry-climate models, we show that as ozone recovery is considered, the troposphere is warmed more than that without considering ozone recovery, suggesting an enhancement of tropospheric warming due to ozone recovery. It is found that the enhanced tropospheric warming is mostly significant in the upper troposphere, with a global and annual mean magnitude of ∼0.41 K for 2001-2050. We also find that relatively large enhanced warming occurs in the extratropics and polar regions in summer and autumn in both hemispheres, while the enhanced warming is stronger in the Northern Hemisphere than in the Southern Hemisphere. Enhanced warming is also found at the surface. The global and annual mean enhancement of surface warming is about 0.16 K for 2001-2050, with maximum enhancement in the winter Arctic. © Author(s) 2011.

Shan D.,Peking University | Gao Y.,Peking University | Jia Y.,Peking University | Jia Y.,Lanzhou University
Angewandte Chemie - International Edition | Year: 2013

Core strength: A new and general strategy for the construction of 3,4-fused tricyclic indoles, which are the core structure of numerous natural products and bioactive molecules, has been developed. The method involves a one-step intramolecular Larock indolization and was successfully applied to the first total synthesis of fargesine. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhou P.-P.,Lanzhou University | Qiu W.-Y.,Lanzhou University | Liu S.,University of North Carolina at Chapel Hill
Physical Chemistry Chemical Physics | Year: 2011

A series of ring-shaped molecular complexes formed by H3N, HF and XY (X = Cl, Br and Y = F, Cl, Br) have been investigated at the MP2/aug-cc-pVTZ level of theory. Their optimized geometry, stretching mode, and interaction energy have been obtained. We found that each complex possesses two red-shifted hydrogen bonds and one red-shifted halogen bond, and the two hydrogen bonds exhibit strong cooperative effects on the halogen bond. The cooperativity among the NH3⋯FH, FH⋯XY and H 3N⋯XY interactions leads to the formations of these complexes. The AIM analysis has been performed at the CCSD(T)/aug-cc-pVQZ level of theory to examine the topological characteristics at the bond critical point and at the ring critical point, confirming the coexistence of the two hydrogen bonds and one halogen bond for each complex. The NBO analysis carried out at the B3LYP/aug-cc-pVTZ level of theory demonstrates the effects of hyperconjugation, hybridization, and polarization coming into play during the hydrogen and halogen bonding formations processes, based on which a clockwise loop of charge transfer was discovered. The molecular electrostatic potential has been employed to explore the formation mechanisms of these molecular complexes. © the Owner Societies.

Li J.,Shanghai University | Wang N.,Shanghai University | Li C.,Shanghai University | Jia X.,Lanzhou University
Organic Letters | Year: 2012

Unprecedented aryne Diels-Alder reactions by using methyleneindolinones as dienes have been disclosed, thus providing a quick access to unusual naphtho-fused oxindoles. A wide range of methyleneindolinones proceed readily with arynes to afford the functionalized oxindoles in good yields. © 2012 American Chemical Society.

Zhou S.,Peking University | Jia Y.,Peking University | Jia Y.,Lanzhou University
Organic Letters | Year: 2014

The total synthesis of (-)-goniomitine has been accomplished in 11 steps starting from commercially available diethyl l-malate. The synthesis features a chiral pool approach to prepare the chiral C-9 unit containing a quaternary carbon center, an Ir-catalyzed C-H borylation to synthesize the 2-indoleboronic acid pinacol ester, and a Suzuki reaction to couple together the two key intermediates. Notably, the high degree of convergence of this strategy makes it particularly amenable to the total synthesis of other aspidosperma family natural products. © 2014 American Chemical Society.

Duan X.-H.,Xi'an Jiaotong University | Liang Y.-M.,Lanzhou University
Accounts of Chemical Research | Year: 2011

Many groups have explored the scope of the palladium-based cyclization of propargylic compounds since Tsujis first report in 1985. Through the proper positioning of an internal nucleophilic center and the judicious selection of an appropriate external nucleophile, the synthetic chemist can effectively assert control over the course of the reaction and its products. However, initial investigations were very limited: only heterocyclic compounds were originally synthesized. We have found the palladium-catalyzed cyclization of propargylic compounds to be a very efficient method for producing both carbocyclic and heterocyclic compounds. In this Account, we discuss the cyclization reactions of functionalized propargylic compounds with a variety of nucleophiles that we have developed over the past few years. We also review similar reactions reported by other groups.We focus here on the cyclization of functionalized propargylic compounds containing a carbon nucleophilic center that is in close proximity to the propargylic moiety. We conducted a detailed investigation of their cyclizations with carbon nucleophiles, with nitrogen nucleophiles, with oxygen nucleophiles, and without nucleophiles. We have developed several efficient and useful methods for the synthesis of indenes, naphthalenes, polycycles, and spirocyclic compounds. All of these reactions proceed satisfactorily under very mild conditions; high regio- and stereoselectivity have been observed as well. In the course of our studies, we provided the first demonstration of a novel tandem C-H activation/bis-cyclization reaction of propargylic compounds with terminal alkynes.In addition, we used external nucleophiles to investigate the cyclization of functionalized propargylic compounds that bear an unsaturated carbon-carbon or carbon-heteroatom bond. We presented the first report of the use of external nucleophiles to initiate a novel cyclization of functionalized propargylic compounds containing an electrophile. This revelation provided a fresh perspective through the discovery of a new type of domino cyclization of propargylic compounds.Metal-catalyzed cyclization of propargylic compounds can provide indenes, cyclopentanones, cyclic carbonates, benzofurans, and a range of other cyclic molecules. A thorough understanding of the mechanisms involved in this class of reaction affords exceptional synthetic control, as shown here by our development of efficient procedures and reagents for palladium-catalyzed propargylic cyclizations. © 2010 American Chemical Society.

News Article | October 26, 2016

Severe weather is becoming more and more frequent around the globe. Often, the difference between minor property damage or something far more devastating is the ability to predict a storm in the first place, especially when it comes to the short-lived but severe variety. "Severe convective storms are intense local phenomena. Research on such phenomena requires high-resolution observational networks, and high-resolution numerical simulation and prediction tools, as well as researchers well trained on the subject," said XUE Ming, a professor of meteorology and the director of the Center for Analysis and Predictions of Storms at the University of Oklahoma. XUE is also an adjunct professor at the School of Atmospheric Sciences at Nanjing University, and a member of the Key Laboratory of Mesoscale Severe Weather/Ministry of Education, affiliated with Nanjing University. "For the past decade, rapid progresses have been made in establishing modern, integrated meteorological observation systems in China," XUE said, who also pointed out the availability of mobile research weather radars and other instruments needed to study convective storms. "The time was right to carry out systematic and organized research on convective storms, with the goal of improving the prediction skills of such weather systems." With that, the "Observation, Prediction and Analysis of severe Convection of China (OPACC)" project was formed. The five-year venture was started in 2013, and has more than $5 million in funding from the Chinese Ministry of Science and Technology. XUE serves as the principal scientist, and Nanjing University leads the project. Other members include Peking University, the Institute of Atmospheric Physics, the National Meteorological Center, the Nanjing University of Information Science and Technology, Lanzhou University, Zhejiang University, and the Beijing Institute of Urban Meteorology. Since 2013, project scientists have published 224 papers on convective weather in peer-reviewed journals. To help publicize the OPACC project, and the research results so far, Advances in Atmospheric Sciences - sponsored by the Institute of Atmospheric Physics of the Chinese Academy of Sciences and published by Springer - organized a special collection of 16 original papers spanning the October and November 2016 issues. The papers cover severe convection subjects ranging from extreme precipitation climatology, data assimilation, numerical simulation and prediction, radar observation, and analyses for convective weather, as well as a study on tornadic events. XUE, a co-chief editor of the journal with LYU Daren and ZHU Jiang, authored the collection's preface. XUE, as an expert on tornado dynamics and convective-scale weather in general, also contributed several papers to the collection, including a featured highlight article on several recent tornadoes in China. "In China, heavy and extreme precipitation, as well as typhoons have received much more attention in research over the past half a century or so, because they tend to produce widespread damages, and their larges sizes also make observational data on these systems much more readily available," XUE said. Observational data on tornadoes is much more difficult to collect, as the equipment has to be physically close to the twister. The tools are more readily available in the United States, where with more than a thousand tornadoes a year, tornado research and prediction has been a top priority. At about a one to 10 ratio, China has far fewer tornadoes than the United States. However, China's tornadoes tend to be in heavily populated areas along the coast, and cause significant damage and loss of life. The tornadoes introduced in XUE's paper were spawned from a variety of weather conditions. The paper serves as a call to action for more tornado research in China, as well as the development and implementation of forecasting and warning tools and operations. "The exact causes of tornado formation are still not well understood... Without understanding the tornado formation processes, and the necessary and sufficient conditions for tornadogenesis, it is difficult to predict tornadoes, or to provide accurate and effective tornado warnings to the public," XUE said. "Research on tornadoes will help us understand [these] questions, and to construct numerical models and establish methods and tools for predicting tornadoes in advance, and... to provide advanced warnings to the public and reduce loss of life and properties." XUE co-authored another paper that addresses this prediction problem, focusing on the July 21, 2012 flash flood in the Beijing area. Seventy-nine people died, and the area suffered 11.64 billion Chinese Yuan (more than $1.8 billion U.S. dollars) in damages. XUE's study uses the 2012 flood to demonstrate the efficacy of an ensemble forecasting system that uses a four-kilometer spacing grid to predict extreme rainfall. The system can successful predict accumulated precipitation of more than 400 millimeters, and it can calculate the probability of extreme precipitation. "Compared to single deterministic forecasts, ensemble forecasts can better capture extreme events and, at the same time, provide information on the reliability or uncertainty of the forecasts. The ensemble mean forecast is often more accurate than individual forecasts," XUE said. "Rapidly updated ensemble probabilistic prediction at convection-resolving resolutions is the future for the forecasting and warning of severe convective weather, and the effective assimilation of very high-resolution weather observations into the forecasting models is also essential." XUE hopes that the special issue of Advances in Atmospheric Sciences will heighten awareness regarding convective weather research associated with the OPACC project, as well as potentially attract more scientists to collaborate in future research endeavors. Related links are as follows: http://link. http://link. .

News Article | March 22, 2016

The researchers say it provides further strong evidence that maintaining biodiversity among the world's species should be a high priority. Published in the journal Ecology, Australian and Chinese researchers from the University of Adelaide and Fudan University in Shanghai studied meadow vegetation at a 3500 metre-altitude research station in the Tibetan Plateau. They investigated the impacts of levels of biodiversity on the severity of a fungal disease. "There are two main theories about the biodiversity-disease relationship in non-human species," says Professor Corey Bradshaw, Sir Hubert Wilkins Chair of Climate Change at the University of Adelaide's Environment Institute. "One is that with more species there is a greater pool of potential hosts for pathogens, so pathogens increase as biodiversity increases. The other asserts that disease decreases with higher diversity because of a 'dilution' effect, where the chance of a pathogen meeting its host species is reduced. "Unfortunately many, if not most, of past studies have used the number of species as the simplest measure of biodiversity but have confounded the results with the abundance of hosts. Another problem is that the evidence has been largely restricted to planting experiments, which limits the extension that can be made to natural communities. "Our experiments, on the other hand, used natural communities and species with similar abundance so we could control for confounding effects of species richness and abundance." The researchers manipulated species richness by removing specific groups of species. The experimental plots at the Alpine Meadow and Wetland Ecosystems Research Station of Lanzhou University are highly biodiverse – up to 40 species in a one square metre plot – making them an ideal "natural laboratory". Professor Bradshaw has been working with Professor Shurong Zhou and her team from Fudan University's School of Life Sciences for several years looking at variation in ecosystem functions in response to altered biodiversity. "The result was rather astounding," says Professor Bradshaw. "The variation in disease severity at the different biodiversity levels almost exactly matched that predicted under the dilution hypothesis. We showed unequivocally that greater biodiversity among the meadow plants reduced the overall incidence of fungal disease, even though there were more pathogens." A second experiment looked at the impact on disease of artificial warming and nitrogen fertiliser, and showed that both warming and nitrogen fertiliser increased the disease load. "Most interestingly, we showed that artificial fertiliser weakened the dilution effect of increasing host biodiversity, most likely by enhancing fungal spore production, infection success and lesion growth by the hosts," says co-author Professor Zhou. "Changing the delicate balance of a healthy community not only resulted in more pathogens but weakened the overall community's resistance to disease." More information: Warming and fertilization alter the dilution effect of host diversity on disease severity DOI: 10.1890/15-1784.1

Li J.J.,Lanzhou University | Li J.J.,University Paris - Sud | Long W.H.,Lanzhou University | Margueron J.,University Claude Bernard Lyon 1 | Van Giai N.,University Paris - Sud
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We have explored the occurrence of the spherical shell closures for superheavy nuclei in the framework of the relativistic Hartree-Fock-Bogoliubov (RHFB) theory. Shell effects are characterized in terms of two-nucleon gaps δ2n(p). Although the results depend slightly on the effective Lagrangians used, the general set of magic numbers beyond 208Pb are predicted to be Z = 120, 138 for protons and N = 172, 184, 228 and 258 for neutrons, respectively. Specifically the RHFB calculations favor the nuclide 120304 as the next spherical doubly magic one beyond 208Pb. Shell effects are sensitive to various terms of the mean-field, such as the spin-orbit coupling, the scalar and effective masses. © 2014 The Authors.

Wang L.J.,Lanzhou University | Sun B.Y.,Lanzhou University | Dong J.M.,CAS Institute of Physics | Long W.H.,Lanzhou University
Physical Review C - Nuclear Physics | Year: 2013

The odd-even staggerings (OESs) on nuclear binding energies are studied systematically within the spherical covariant density functional (CDF) theories, specifically the relativistic Hartree-Fock-Bogoliubov (RHFB) and the relativistic Hartree-Bogoliubov (RHB) theories. When taking the finite-range Gogny force D1S as an effective pairing interaction, both CDF models can provide appropriate descriptions on the OESs of nuclear binding energies for C, O, Ca, Ni, Zr, Sn, Ce, Gd, and Pb isotopes as well as for N=50 and 82 isotones. While there still exist some systematical discrepancies from the data, i.e., the underestimated OESs in light C and O isotopes and the overestimated ones in heavy regions, respectively, such discrepancies can be eliminated partially by introducing a Z- or N-dependent strength factor into the pairing force Gogny D1S. As an example of application, distinct improvements are achieved with the optimized pairing force in determining the single-particle configurations of 112,114,118,124Sn. © 2013 American Physical Society.

Lin S.,Lanzhou University | Lin S.,CAS Institute of Physics | Shen C.,CAS Institute of Physics | Lu D.,Lanzhou University | And 2 more authors.
Carbon | Year: 2013

Reduced graphene oxide (rGO)-encapsulated amine functionalized Fe 3O4 magnetic nanospheres (AMs), were used to support Pt catalysts (Pt-rGO-AMs). The Pt-rGO-AMs were fabricated by modifying positively-charged aminopropyltrimethoxysilane on the surface of Fe 3O4 nanoparticles (NPs) to form functionalized Fe 3O4 NPs. Then negatively-charged graphene oxide (GO) was coated on the surface of the functionalized Fe3O4 nanospheres by electrostatic layer-by-layer self-assembly. Finally, Pt NPs were uniformly anchored on the surface of GO by a polyol reduction reaction and the GO was simultaneously reduced to rGO. The Pt-rGO-AMs exhibit excellent ferromagnetic property, which makes it possible to realize controllable on-off reactions and convenient recycling of catalyst materials. The electrochemical activity of the catalyst for methanol oxidation is significantly improved compared to Pt NPs absorbed on a rGO sheet and has better stability. The superior performance of this Pt-rGO-AMs catalyst is attributed both to the structure, which improve the accessibility of the Pt NPs by exposing them on the surface of the support, and to the greatly improved electronic conductivity of the support. © 2012 Elsevier Ltd. All rights reserved.

Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Institute of Physics | Liu X.,Lanzhou University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In this work, we predict two charged charmoniumlike enhancement structures close to the D*D̄ and D*D ̄* thresholds, where the Initial Single Pion Emission mechanism is introduced in the hidden-charm dipion decays of higher charmonia ψ(4040), ψ(4160), ψ(4415) and charmoniumlike state Y(4260). We suggest BESIII to search for these structures in the J/ψπ+, ψ(2S)π+ and hb(1P) π+ invariant mass spectra of the ψ(4040) decays into J/ψπ+π-, ψ(2S)π+π - and hb(1P)π+π-. In addition, the experimental search for these enhancement structures in the J/ψπ+, ψ(2S)π+ and hc(1P) π+ invariant mass spectra of the ψ(4260) hidden-charm dipion decays will be accessible at Belle and BABAR. © 2011 American Physical Society.

Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Institute of Physics | Liu X.,Lanzhou University | Zhu S.-L.,Beijing University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Inspired by the newly observed two charged bottomoniumlike states, we consider the possible contribution from the intermediate Zb(10610) and Zb(10650) states to the Υ(5S)→Υ(2S) π+π- decay process, which naturally explains Belle's previous observation of the anomalous Υ(2S)π+π - production near the peak of Υ(5S) at √s=10.87GeV. The resulting dΓ(Υ(5S)→Υ(2S)π+π-)/ dmπ+π- and dΓ(Υ(5S) →Υ(2S)π+π-)/dcosθ distributions agree with Belle's measurement after inclusion of these Zb states. This formalism also reproduces the Belle observation of the double-peak structure and its reflection in the Υ(2S)π+ invariant mass spectrum of the Υ(5S)→Υ(2S)π+π- decay. © 2011 American Physical Society.

Zhu D.-C.,China University of Geosciences | Zhao Z.-D.,China University of Geosciences | Niu Y.,China University of Geosciences | Niu Y.,Lanzhou University | And 3 more authors.
Geology | Year: 2011

The U-Pb age and Hf isotope data on detrital zircons from Paleozoic metasedimentary rocks in the Lhasa terrane (Tibet) define a distinctive age population of ca. 1170 Ma with εHf(t) values identical to the coeval detrital zircons from Western Australia, but those from the western Qiangtang and Tethyan Himalaya terranes define an age population of ca. 950 Ma with a similar εHf(t) range. The ca. 1170 Ma detrital zircons in the Lhasa terrane were most likely derived from the Albany-Fraser belt in southwest Australia, whereas the ca. 950 Ma detrital zircons from both the western Qiangtang and Tethyan Himalaya terranes might have been sourced from the High Himalaya to the south. Such detrital zircon connections enable us to propose that the Lhasa terrane is exotic to the Tibetan Plateau system, and should no longer be considered as part of the Qiangtang-Greater India-Tethyan Himalaya continental margin system in the Paleozoic reconstruction of the Indian plate, as current models show; rather, it should be placed at the northwestern margin of Australia. These results provide new constraints on the paleogeographic reconstruction and tectonic evolution of southern Tibet, and indicate that the Lhasa terrane evolved as part of the late Precambrian-early Paleozoic evolution as part of Australia in a different paleogeographical setting than that of the Qiangtang-Greater India-Tethyan Himalaya system. © 2011 Geological Society of America.

Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Institute of Physics | Liu X.,Lanzhou University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We propose a unique mechanism called initial single pion emission existing in the Υ(5S) decays, and further study the line shapes of dΓ(Υ(5S→Υ(nS)π +π -))/ dmΥ(nS)π + (n=1,2,3) and dΓ(Υ(5S→h b(mP)π +π -))/dm hb(mP) π + (m=1,2). We find sharp structures around 10610MeV and 10650MeV in the obtained theoretical line shapes of dΓ(Υ(5S→Υ(nS) π +π -))/dmΥ(nS)π + and dΓ(Υ(5S→h b(mP)π +π -))/ dm hb(mP)π + distributions, which could naturally correspond to the Z b(10610) and Z b(10650) structures newly observed by Belle. © 2011 American Physical Society.

Niu Y.,Lanzhou University | Niu Y.,Durham University
RSC Advances | Year: 2012

Zr-Hf and Nb-Ta are two elemental twins, each of which has the same valence (i.e. 5 + for Nb and Ta, and 4 + for Zr and Hf) and same ionic size at a given coordination number (e.g. R Nb/R Ta = 1.000 and R Zr/R Hf = 1.006 to ∼1.026 for coordination numbers of 6, 7, 8 and 12). As a result, it has been the view that Zr does not fractionate from Hf and Nb does not fractionate from Ta in the formation of minerals and in all Earth processes. Recent studies, however, have shown that this traditional view is in error. Up to 2 orders of magnitude fractionations have been observed in rocks from the world ocean floor and also in the seawater on various scales. I discuss some possible processes that may help explain such large fractionations, but further work is needed to test the validity of these interpretations. Perspectives from the chemistry community are in compelling need to help address this basic problem of scientific significance in understanding the chemical differentiation of our planet. © 2012 The Royal Society of Chemistry.

Zhu D.-C.,China University of Geosciences | Zhao Z.-D.,China University of Geosciences | Niu Y.,Lanzhou University | Niu Y.,Durham University | And 4 more authors.
Gondwana Research | Year: 2013

Different hypotheses have been proposed for the origin and pre-Cenozoic evolution of the Tibetan Plateau as a result of several collision events between a series of Gondwana-derived terranes (e.g., Qiangtang, Lhasa and India) and Asian continent since the early Paleozoic. This paper reviews and reevaluates these hypotheses in light of new data from Tibet including (1) the distribution of major tectonic boundaries and suture zones, (2) basement rocks and their sedimentary covers, (3) magmatic suites, and (4) detrital zircon constraints from Paleozoic metasedimentary rocks. The Western Qiangtang, Amdo, and Tethyan Himalaya terranes have the Indian Gondwana origin, whereas the Lhasa Terrane shows an Australian Gondwana affinity. The Cambrian magmatic record in the Lhasa Terrane resulted from the subduction of the proto-Tethyan Ocean lithosphere beneath the Australian Gondwana. The newly identified late Devonian granitoids in the southern margin of the Lhasa Terrane may represent an extensional magmatic event associated with its rifting, which ultimately resulted in the opening of the Songdo Tethyan Ocean. The Lhasa-northern Australia collision at ~ 263. Ma was likely responsible for the initiation of a southward-dipping subduction of the Bangong-Nujiang Tethyan Oceanic lithosphere. The Yarlung-Zangbo Tethyan Ocean opened as a back-arc basin in the late Triassic, leading to the separation of the Lhasa Terrane from northern Australia. The subsequent northward subduction of the Yarlung-Zangbo Tethyan Ocean lithosphere beneath the Lhasa Terrane may have been triggered by the Qiangtang-Lhasa collision in the earliest Cretaceous. The mafic dike swarms (ca. 284. Ma) in the Western Qiangtang originated from the Panjal plume activity that resulted in continental rifting and its separation from the northern Indian continent. The subsequent collision of the Western Qiangtang with the Eastern Qiangtang in the middle Triassic was followed by slab breakoff that led to the exhumation of the Qiangtang metamorphic rocks. This collision may have caused the northward subduction initiation of the Bangong-Nujiang Ocean lithosphere beneath the Western Qiangtang. Collision-related coeval igneous rocks occurring on both sides of the suture zone and the within-plate basalt affinity of associated mafic lithologies suggest slab breakoff-induced magmatism in a continent-continent collision zone. This zone may be the site of net continental crust growth, as exemplified by the Tibetan Plateau. © 2012 International Association for Gondwana Research.

Qiu Q.-S.,University of Illinois at Urbana - Champaign | Qiu Q.-S.,Lanzhou University | Fratti R.A.,University of Illinois at Urbana - Champaign
Journal of Cell Science | Year: 2010

Nhx1p is a Na+(K+)/H+ antiporter localized at the vacuolar membrane of the yeast Saccharomyces cerevisiae. Nhx1p regulates the acidification of cytosol and vacuole lumen, and is involved in membrane traffic from late endosomes to the vacuole. Deletion of the gene leads to aberrant vacuolar morphology and defective vacuolar protein sorting. These phenotypes are hallmarks of malfunctioning vacuole homeostasis and indicate that membrane fusion is probably altered. Here, we investigated the role of Nhx1p in the regulation of homotypic vacuole fusion. Vacuoles isolated from nhx1Δ yeast showed attenuated fusion. Assays configured to differentiate between the first round of fusion and ongoing rounds showed that nhx1Δ vacuoles were only defective in the first round of fusion, suggesting that Nhx1p regulates an early step in the pathway. Although fusion was impaired on nhx1Δ vacuoles, SNARE complex formation was indistinguishable from wild-type vacuoles. Fusion could be rescued by adding the soluble SNARE Vam7p. However, Vam7p only activated the first round of nhx1Δ vacuole fusion. Once fusion was initiated, nhx1Δ vacuoles appeared behave in a wild-type manner. Complementation studies showed that ion transport function was required for Nhx1p-mediated support of fusion. In addition, the weak base chloroquine restored nhx1Δ fusion to wild-type levels. Together, these data indicate that Nhx1p regulates the initiation of fusion by controlling vacuole lumen pH.

Niu Y.,Lanzhou University | Niu Y.,Durham University | Wilson M.,University of Leeds | Humphreys E.R.,University of Bristol | O'Hara M.J.,Aberystwyth University
Journal of Petrology | Year: 2011

Based on an evaluation of major and trace element data for ocean island basalts (OIB), we demonstrate that oceanic lithosphere thickness variation, which we refer to as the lid effect, exerts the primary control on OIB geochemistry on a global scale. The lid effect caps the final depth (pressure) of melting or melt equilibration. OIB erupted on thick lithosphere have geochemical characteristics consistent with a low extent and high pressure of partial melting, whereas those erupted on thin lithosphere exhibit the reverse; that is, a high extent and low pressure of melting cessation. This observation requires that mantle melting beneath intra-plate volcanic islands takes place in the asthenosphere and results from dynamic upwelling and decompression. Melting beneath all ocean islands begins in the garnet peridotite facies, imparting the familiar 'garnet signature' to all OIB melts (e.g. [Sm/Yb]N > 1); however, the intensity of this signature decreases with increasing extent of melting beneath thinner lithospheric lids as a result of dilution. The dilution effect is also recorded in the radiogenic isotope composition of OIB, consistent with the notion that their mantle source regions are heterogeneous with an enriched component of lower solidus temperature dispersed in a more refractory matrix. High-quality data on the compositions of olivine phenocrysts from mid-ocean ridge basalt and global OIB sample suites are wholly consistent with the lid effect without the need to invoke olivine-free pyroxenite as a major source component for OIB. Caution is necessary when using basalt-based thermobarometry approaches to estimate mantle potential temperatures and solidus depth because OIB do not unequivocally record such information. For plate ages up to ~80 Ma, we demonstrate that the geophysically defined base of the growing oceanic lithosphere corresponds to both an isotherm (~1100°C) and the pargasite (amphibole) dehydration solidus of fertile mantle peridotite. As pargasite in H2O-CO2-bearing mantle peridotite is stable under conditions of T ≤ 1100°C and P ≤ 3 GPa (~90 km), this solidus is essentially isothermal (i.e. dT/dP ~ 0 in P-T space) with T ~ 1100°C) at depths ≤90 km, but becomes isobaric (i.e. dP/dT ~ 0 in P-T space) at the ~90 km depth. The latter explains why older (>70 Ma) oceanic lithosphere cannot be thicker than ~90 km without the need to invoke physically complex processes such as convective removal. © The Author 2011. Published by Oxford University Press. All rights reserved.

Wang C.,Lanzhou University | Liang X.-Z.,University of Illinois at Urbana - Champaign | Samel A.N.,Bowling Green State University
Journal of Climate | Year: 2011

Analysis of 26 simulations from 11 general circulation models (GCMs) of the Atmospheric Model Intercomparison Project (AMIP) II reveals a basic inability to simultaneously predict the Yangtze River Valley (YRV) precipitation (PrYRV) annual cycle and summer interannual variability in response to observed global SST distributions. Only the Community Climate System Model (CCSM) and L'Institut Pierre-Simon Laplace (IPSL) models reproduce the observed annual cycle, but both fail to capture the interannual variability. Conversely, only Max Planck Institute (MPI) simulates interannual variability reasonably well, but its annual cycle leads observations by 2 months. The interannual variability of PrYRV reveals two distinct signals in observations, which are identified with opposite subtropical Pacific SST anomalies in the east (SSTe) and west (SSTw). First, negative SSTe anomalies are associated with equatorward displacement of the upper-level East Asian jet (ULJ) over China. The resulting transverse circulation enhances low-level southerly flow over the South China Sea and south China while convergent flow and upward motion increase over the YRV. Second, positive SSTw anomalies are linked with westward movement of the subtropical high over the west-central Pacific. This strengthens the low-level jet (LLJ) to the south of the YRV. These two signals act together to enhance PrYRV. The AMIP II suite, however, generally fails to reproduce these features. Only the MPI.3 realization is able to simulate both signals and, consequently, realistic PrYRV interannual variations. It appears that PrYRV is governed primarily by coherent ULJ and LLJ variations that act as the atmospheric bridges to remote SSTe and SSTw forcings, respectively. The PrYRV response to global SST anomalies may then be realistically depicted only when both bridges are correctly simulated. The above hypothesis does not exclude other signals that may play important roles linking PrYRV with remote SST forcings through certain atmospheric bridges, which deserve further investigation. © 2011 American Meteorological Society.

Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2009.5.1 | Award Amount: 5.15M | Year: 2010

Mental health care represents over a third of the cost of health care to all EU nations. However little is being done to develop effective systems for Prevention of the onset of the illnesses or to provide easier Diagnosis with a view to better determine the effects of treatment.\nOPTIMI will change this by developing tools to perform Prediction through early identification of the onset of an illness by monitoring poor coping behaviour. It is based on the hypothesis that the central issue and starting point of longer term mental illness depends on the individuals capacity and ability to cope with stress.\nOPTIMI will first identify the occurrence of high stress in the individual on a daily basis. Then it will determine the ongoing effect of stress on the individual by studying the behaviour pattern over a longer period. Finally it will also make estimates of the base line changes in the persons state of mind using symptomatic measurements that closely link depression with cognitive, motor and verbal behaviour. We will use wearable and domestic appliances and identification will be based on noting when stress occurs, at a fine time resolution using ECG and Cortisol, and daily using the Electronic Diary. The effects on behaviour will be identified using EEG, Voice analysis, Physical Activity analysis and the Electronic Diary. Finally specific markers of depression will be checked using EEG, Voice analysis and Physical Activity.The smart sensors will be enhanced with a knowledge based rule system to interpret the data and provide a diagnostic tool for both pharmacological and CBT based preventative and intervening treatments. We will then augment two existing CCBT systems to use these tools in real time to optimise the treatment cycle. We will conduct two phases of trials with volunteers who come from high risk situations (such as mothers caring for a disabled child, recession unemployed and critical final examinations) both phases being held in total in 5 countries

Wang Y.,CAS Nanjing Institute of Geology and Palaeontology | Huang C.,Sichuan University | Sun B.,Lanzhou University | Quan C.,Jilin University | And 3 more authors.
Earth-Science Reviews | Year: 2014

The Cretaceous was one of the most remarkable periods in geological history, with a "greenhouse" climate and several important geological events. Reconstructions of atmospheric CO2 using proxies are crucial for understanding the Cretaceous "greenhouse." In this paper we summarize the major approaches for reconstructing CO2 based on paleobotanical or geochemical data, and synthesize the CO2 variations throughout the Cretaceous. The results show that atmospheric CO2 levels remained relatively high throughout the Cretaceous, but were lower in the early Cretaceous, highest in the mid-Cretaceous and gradually declined during the late Cretaceous. However, this overall trend was interrupted by several rapid changes associated with ocean anoxic events (OAEs) and the end-Cretaceous catastrophic event. New data on paleo-CO2 levels from paleobotanical and paleosol evidences support not only the overall trends indicated by geochemical models, but provide more precise records of the short-term fluctuations related to brief episodes of climate change. Temporal resolution within the long quiet magnetic period in the middle Cretaceous is one of the obstacles preventing us from a more comprehensive understanding of the CO2 climate linkage. But new paleo-CO2 determinations and climatic data from stratigraphic sections of sediments intercalated with datable volcanic rocks will allow a better understanding of the relationships between fluctuations of atmospheric CO2, climate change, and geological events. © 2013 Elsevier B.V.

Ma Q.,Lanzhou University | Mei Z.L.,Lanzhou University | Zhu S.K.,Lanzhou University | Jin T.Y.,Lanzhou University | Cui T.J.,Nanjing Southeast University
Physical Review Letters | Year: 2013

In recent years, invisibility cloaks have received a lot of attention and interest. These devices are generally classified into two types: passive and active. The design and realization of passive cloaks have been intensively studied using transformation optics and plasmonic approaches. However, active cloaks are still limited to theory and numerical simulations. Here, we present the first experiment on active cloaking and propose an active illusion for the Laplace equation. We make use of a resistor network to simulate a conducting medium. Then, we surround the central region with controlled sources to protect it from outside detection. We show that by dynamically changing the controlled sources, the protected region can be cloaked or disguised as different objects (illusion). Our measurement results agree very well with numerical simulations. Compared with the passive counterparts, the active cloaking and illusion devices do not need complicated metamaterials. They are flexible, in-line controllable, and adaptable to the environment. In addition to dc electricity, the proposed method can also be used for thermodynamics and other problems governed by the Laplace equation. © 2013 American Physical Society.

Li Y.-M.,Kunming University of Science and Technology | Shen Y.,Kunming University of Science and Technology | Chang K.-J.,Kunming University of Science and Technology | Yang S.-D.,Lanzhou University
Tetrahedron | Year: 2014

A novel metal-free oxidative arylphosphination of activated N-substituted-N-arylacrylamide derivatives by phosphorylation and C-H functionalization cascade process has been developed. This methodology provides an efficient way to construct a variety of phosphorus-containing oxindole moieties. © 2014 Elsevier Ltd. All rights reserved.

Li Y.-M.,Kunming University of Science and Technology | Shen Y.,Kunming University of Science and Technology | Chang K.-J.,Kunming University of Science and Technology | Yang S.-D.,Lanzhou University
Tetrahedron Letters | Year: 2014

A novel arylnitration of alkenes by nitration and C-H functionalization cascade process has been developed. This methodology provides an efficient way to construct a variety of nitro-containing oxindoles and dihydroquinolin-2(1H)- ones. In addition, the process exhibits significant functional group tolerance. Moreover, the use of inexpensive and readily available starting materials makes this practical and atom-economical approach particularly attractive. © 2013 Published by Elsevier Ltd.

Yu X.,Kunming University of Science and Technology | Xu X.,Lanzhou University | Qiu J.,Kunming University of Science and Technology
Materials Research Bulletin | Year: 2011

We report the observation of long lasting red phosphorescence in Sr 2SnO4:Sm3+ and Sr2SnO 4:Sm3+, Dy3+ phosphors. The decay patterns of afterglow curves demonstrate that the afterglow time of Sr2SnO 4:Sm3+ could be prolonged by the incorporation of Dy 3+. The remarkable changes in the thermoluminescence glow curve exhibited that the first band responsible for the origin of the afterglow becomes the most prominent feature when Dy3+ added. In other words, the enhancement of the red afterglow in Sr2SnO4:Sm 3+, Dy3+ compared with Sr2SnO 4:Sm3+ could be ascribed to more appropriate traps (the hole-traps V″Sr) created by the incorporation of Dy3+. © 2010 Elsevier Ltd © 2011 Elsevier Ltd. All rights reserved.

Che J.,Nanchang Institute of Technology | Wang J.,Lanzhou University | Wang G.,East China Jiaotong University | Wang G.,Baoshan College
Energy | Year: 2012

Electric load forecasting is an important task in the daily operations of a power utility associated with energy transfer scheduling, unit commitment and load dispatch. Inspired by the various non-linearity of electric load data and the strong learning capacity of support vector regression (SVR) for small sample and balanced data, this paper presents an adaptive fuzzy combination model based on the self-organizing map (SOM), the SVR and the fuzzy inference method. The adaptive fuzzy combination model can effectively count for electric load forecasting with good accuracy and interpretability at the same time. The key idea behind the combination is to build a human-understandable knowledge base by constructing a fuzzy membership function for each homogeneous sub-population. The comparison of different mathematical models and the effectiveness of the presented model are shown by the real data of New South Wales electricity market. The obtained results confirm the validity of the developed model. © 2011 Elsevier Ltd.

Ma F.,Lanzhou University | Qin Y.,Lanzhou University | Li Y.-Z.,Beihang University
Applied Physics Letters | Year: 2010

Co nanoflakes are synthesized through a low temperature hydrothermal method. The single-phased hexagonal close-packed Co nanoflakes have a diameter of several micrometers and a thickness about 80 nm. Magnetic hysteresis loops are quite different along different directions deviating from the nanoflakes plane, which shows Co nanoflakes have strong magnetic anisotropy. Flakelike morphology influence the performance of complex permeability in gigahertz frequency. Natural resonance peak happens at 5.74 GHz with the contribution of shape anisotropy. Multiple resonance phenomenon appears due to the exchange resonance effect, which makes Co nanoflakes a broadband candidate for microwave absorbing material. © 2010 American Institute of Physics.

Liu Y.,Sichuan University | Hu H.,Sichuan University | Zheng H.,Sichuan University | Xia Y.,Sichuan University | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2014

Highly efficient catalytic asymmetric Claisen rearrangements of O-propargyl β-ketoesters and O-allyl β-ketoesters have been accomplished under mild reaction conditions. In the presence of the chiral N,N′-dioxide/NiII complex, a wide range of allenyl/allyl-substituted all-carbon quaternary β-ketoesters was obtained in generally good yield (up to 99 %) and high diastereoselectivity (up to 99:1 d.r.) with excellent enantioselectivity (up to 99 % ee). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang F.,Lanzhou University | Mei Z.L.,Lanzhou University | Jin T.Y.,Lanzhou University | Cui T.J.,Nanjing Southeast University
Physical Review Letters | Year: 2012

We present the first experimental demonstration of a dc electric cloak for steady current fields. Using the analogy between electrically conducting materials and resistor networks, a dc invisibility cloak is designed, fabricated, and tested using the circuit theory. We show that the dc cloak can guide electric currents around the cloaked region smoothly and keep perturbations only inside the cloak. Outside the cloak, the current lines return to their original directions as if nothing happens. The measurement data agree exceptionally well with the theoretical prediction and simulation result, with nearly perfect cloaking performance. The proposed method can be directly used to realize other dc electric devices with anisotropic conductivities designed by the transformation optics. Manipulation of steady currents with the control of anisotropic conductivities has a lot of potential applications, such as electric impedance tomography, graphene, natural resource exploration, and military camouflage. © 2012 American Physical Society.

Wang R.,Lanzhou University | Mei Z.L.,Lanzhou University | Cui T.J.,Nanjing Southeast University
Applied Physics Letters | Year: 2013

We present a two-dimensional carpet cloak for static magnetic field, a design that renders the magnetic response of a given volume invisible from its exterior, without altering the external magnetic fields. The device is designed using transformation optics method and can be implemented with alternating superconducting and magnetic material layers. Through the proper design of the constitutive tensors and relative thicknesses of each slab, we achieve the perfect performance of invisibility. Full wave numerical simulations confirm our design. © 2013 AIP Publishing LLC.

Xiang Jiang W.,Nanjing Southeast University | Yang Luo C.,Nanjing Southeast University | Lei Mei Z.,Lanzhou University | Jun Cui T.,Nanjing Southeast University
Applied Physics Letters | Year: 2013

We propose and experimentally demonstrate an ultrathin but nearly perfect dc electric invisibility cloak. In the dc limit, transformation optics reduces to transformation electrostatics. Based on a special coordinate transformation, we derive a nearly perfect dc electric cloak which is composed of homogeneous and anisotropic conducting material. Due to the homogeneity feature, the dc cloak is realized using an ultrathin dc metamaterial with only one-unit-cell thickness, which is the ultra limit for practical artificial materials. Although ultrathin, our experimental results show that the dc cloak has excellent performance with nearly perfect cloaking behaviour. © 2013 American Institute of Physics.

Dong Y.-L.,Lanzhou University | Zhang H.-G.,Lanzhou University | Rahman Z.U.,Lanzhou University | Su L.,Lanzhou University | And 4 more authors.
Nanoscale | Year: 2012

In this report, graphene oxide-Fe 3O 4 magnetic nanocomposites were demonstrated to possess intrinsic peroxidase-like activity and enhanced affinity toward H 2O 2. The nanocomposites retain their magnetic properties and can be effectively separated by a magnet. Significantly, they were proved to be novel peroxidase mimetics which could quickly catalyze oxidation of the peroxidase substrate 3,3,5,5- tetramethylbenzidine (TMB) in the presence of H 2O 2, producing a blue-colored solution. Kinetic analysis indicates that the catalytic behavior is in accord with typical Michaelis-Menten kinetics and follows a ping-pong mechanism. On the basis of the high activity, the reaction provides a simple, sensitive and selective method for colorimetric detection of glucose in diabetic urine. © 2012 The Royal Society of Chemistry.

Xie M.,Sichuan University | Xie M.,Lanzhou University | Liu X.,Sichuan University | Wu X.,Sichuan University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2013

Add a ring: A catalytic asymmetric [8+2] cycloaddition reaction of azaheptafulvenes with alkylidene malonates was developed. When employing catalytic amounts of a chiral N,N-dioxide L-NiII complex, the reaction afforded functionalized cycloheptatriene-fused pyrrole derivatives in excellent yields (up to 99 %), diastereoselectivities (>95:5 d.r.), and enantioselectivities (91-97 % ee) under mild conditions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang Z.,University of Aarhus | Song J.,University of Aarhus | Song J.,Lanzhou University | Besenbacher F.,University of Aarhus | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2013

Efficient self-assembly: Self-assembly of DNA nanostructures at room temperature was achieved by incubating the component strands in the presence of a denaturing agent (30-40% formamide). This isothermal method is efficient for assembly of both DNA origami (purple, see scheme) and single-stranded tile (SST, blue) structures, as well as an SST ribbon growing on an origami template. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhou P.-P.,Beijing Computational Science Research Center | Zhou P.-P.,Lanzhou University | Zhang R.-Q.,City University of Hong Kong
Physical Chemistry Chemical Physics | Year: 2015

A series of benzene derivatives with different substituents adsorbed on graphene was investigated using a density-functional tight-binding method with a dispersion correction. Compared to benzene, the derivative with either an electron-withdrawing or -donating substituent exhibits stronger physisorption. Moreover, the steric size of the substituent is important in determining the adsorption strength, while the direction and the number of H atoms in the substituent affect the electron transfer from graphene. NBO analysis reveals that the stereoelectronic effect of the conjugation between the substituent and the benzene ring strongly influences the π⋯π interaction region between the molecule and graphene. The findings can deepen the understanding of the interaction between an aromatic molecule and graphene as well as the corresponding adsorption mechanism. © the Owner Societies 2015.

Li W.,Sichuan University | Liu X.,Sichuan University | Hao X.,Sichuan University | Cai Y.,Sichuan University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2012

Asymmetric expansion: A catalytic asymmetric ring-expansion reaction of the title compounds occurs in the presence of a Sc(OTf)3 catalyst bearing an N,N?-dioxide-based ligand. Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl).

Wu W.,Lanzhou University | Kirillov A.M.,University of Lisbon | Yan X.,Lanzhou University | Zhou P.,Lanzhou University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2014

A novel metal-organic framework (MOF) was fabricated by spontaneous K+-induced supramolecular self-assembly with the embedded tripodal ligand units. When the 3D ligand was loaded onto Fe3O4@mSiO2 core-shell nanoparticles, it could effectively separate K+ ions from a mixture of Na+, K+, Mg2+, and Ca2+ ions through nanoparticle-assisted MOF crystallization into a Fe3O4@mSiO2@MOF hybrid material. Excess potassium ions could be extracted because of the specific cation-π interaction between K+ and the aromatic cavity of the MOF, leading to enhanced separation efficiency and suggesting a new application for MOFs. A metal-organic framework (MOF) was fabricated by spontaneous K+-induced supramolecular self-assembly with the embedded 3D ligand units supported by Fe3O4@mSiO2 core-shell nanoparticles. The hybrid material based on Fe3O4@mSiO2@MOF can selectively separate K+ ions from a mixture of Na+, K+, Mg2+, and Ca2+ ions, facilitated by a specific cation-π interaction between K+ and the aromatic cavity of the MOF. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang F.,Lanzhou University | Mei Z.L.,Lanzhou University | Yang X.Y.,Lanzhou University | Jin T.Y.,Lanzhou University | Cui T.J.,Nanjing Southeast University
Advanced Functional Materials | Year: 2013

The theoretical design and the first experimental verification of an exterior dc invisibility cloak that can hide an object from dc detection at a distance are presented. Based on the transformation optics theory, the exterior dc cloak requires negative conductivity material to create folded geometry, which will cancel the real geometry of detected object in distance and make it invisible. Negative conductivities are designed and realized using active devices, together with resistor networks, to generate the equivalent conductivity materials required by the exterior dc cloak. An experimental sample of the dc cloak is fabricated on the printed circuit board and the measured result has excellent agreement with numerical and circuit simulations, showing very good cloaking performance at a distance. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mei Z.L.,Lanzhou University | Bai J.,Lanzhou University | Niu T.M.,Lanzhou University | Cui T.J.,Nanjing Southeast University
IEEE Transactions on Antennas and Propagation | Year: 2012

An X-band half Maxwell fish-eye lens antenna is designed based on the effective medium theory and metamaterials technology. The non-resonant I-shaped metamaterials have been chosen to realize the lens antenna due to the broadband and low-loss features. The laboratory prototype has been fabricated and measured using a two-dimensional near-field microwave scanning apparatus, where the experimental results agree with full-wave numerical simulations. © 2006 IEEE.

Lin L.,Sichuan University | Kuang Y.,Sichuan University | Liu X.,Sichuan University | Feng X.,Sichuan University | Feng X.,Lanzhou University
Organic Letters | Year: 2011

A highly diastereo- and enantioselective hetero-Diels-Alder (HDA) reaction of a Brassard-type diene with aliphatic aldehydes has been developed. The chiral N,N′-dioxide L2/In(OTf) 3 complex was efficient toward the obtention of the corresponding β-methoxy-γ-methyl α,β-unsaturated δ-lactones in good yields (up to 86%) as well as dr and ee values (up to 97:3 cis/trans and 94% ee). In addition, the product 4a could be easily transformed into the methyl-protected epi-prelactone B by hydrogenation. © 2011 American Chemical Society.

Cai R.-G.,CAS Institute of Theoretical Physics | Wang Y.-Q.,Lanzhou University | Zhang H.-Q.,University of Lisbon
Journal of High Energy Physics | Year: 2014

We construct a holographic model of superconducting quantum interference device (SQUID) in the Einstein-Maxwell-complex scalar theory with a negative cosmological constant. The SQUID ring consists of two Josephson junctions which sit on two sides of a compactified spatial direction of a Schwarzschild-AdS black brane. These two junctions interfere with each other and then result in a total current depending on the magnetic flux, which can be deduced from the phase differences of the two Josephson junctions. The relation between the total current and the magnetic flux is obtained numerically. © 2014 SISSA.

Du W.-B.,Beihang University | Wu Z.-X.,Lanzhou University | Cai K.-Q.,Beihang University
Physica A: Statistical Mechanics and its Applications | Year: 2013

With rapid economic and social development, the problem of traffic congestion is getting more and more serious. Accordingly, network traffic models have attracted extensive attention. In this paper, we introduce a shortest-remaining-path-first queuing strategy into a network traffic model on Barabási-Albert scale-free networks under efficient routing protocol, where one packet's delivery priority is related to its current distance to the destination. Compared with the traditional first-in-first-out queuing strategy, although the network capacity has no evident changes, some other indexes reflecting transportation efficiency are significantly improved in the congestion state. Extensive simulation results and discussions are carried out to explain the phenomena. Our work may be helpful for the designing of optimal networked-traffic systems. © 2013 Elsevier B.V. All rights reserved.

Mischke S.,Free University of Berlin | Zhang C.,Lanzhou University | Borner A.,German Aerospace Center | Herzschuh U.,Alfred Wegener Institute for Polar and Marine Research
Journal of Quaternary Science | Year: 2010

Predominantly laminated lake sediments from a saline closed-basin lake on the north-eastern Tibetan Plateau were investigated using a multi-proxy approach (14C-accelerator mass spec-trometry dating, smear-slide analysis, loss on ignition, grain size, X-ray diffraction, elemental concentration, ostracod assemblages, stable isotopes of ostracod shells) to trace the regional environmental and climatic history in the Lateglacial and Holocene. Before about 15cal.ka BP, small saline water bodies probably filled the basin under unstable cold and harsh environmental conditions. Soon after about 14.9cal. ka BP,a relatively deep saline lake was established, probably as a result of runoff from melting snow, ice and frozen ground in the lake's catchment. Large changes in flux of aeolian material to the lake were recorded during this initial period of formation of Lake Kuhai. Highest lake levels, a low sediment accumulation rate and less saline conditions were maintained between about 12.8 and 7.1cal.ka BP when the aeolian influx diminished significantly. After about 7.1cal.ka BP, the aeolian influx remained at a moderate level apart from a strongly increased dust delivery to the lake between about 6.1 and 5.4cal.ka BP and a minor short-lived period of slightly enhanced aeolian influx at about 2.7cal.ka BP. The strongly enhanced dust input to the lake between 6.1 and 5.4cal.ka BP represented the largest influx of aeolian material to Lake Kuhai during the entire Holocene. However, evidence for climatic deterioration during this period is not seen at most other palaeoclimate sites on the Tibetan Plateau, but instead a significant increase in aridity has been recorded at numerous sites in the northern foreland of the Tibetan Plateau and on the Chinese Loess Plateau. The large dust input to Lake Kuhai between 6.1 and 5.4cal.ka BP probably did not result from a severe climate deterioration on the Tibetan Plateau itself, but from the pronounced aridity in its northern and eastern foreland. In contrast, the increaseindust influx about 2.7 cal.kaBP seems tocorrespondtoa brief warming spell recorded at other sites on the Tibetan Plateau too. A slight increase in lake level and decrease in salinity after about 0.6cal.ka BP suggests a slightly higher effective moisture during the final lake stage, accompanied by a some what larger dust in flux. This apparent contradiction possibly results from enhanced human activities on the northeastern Tibetan Plateau during the last 600 years. © 2009 John Wiley & Sons, Ltd.

Mei Z.L.,Lanzhou University | Mei Z.L.,Nanjing Southeast University | Bai J.,Lanzhou University | Cui T.J.,Nanjing Southeast University
New Journal of Physics | Year: 2011

It is experimentally verified that a two-dimensional planar focusing antenna based on gradient-index metamaterials has a similar performance as that of its parabolic counterpart. The antenna is designed using quasi-conformal transformation optics, and is realized with non-resonant I-shaped metamaterial unit cells. It is shown that the antenna has a broad bandwidth and very low loss. Near-field distributions of the antenna are measured and far-field radiation patterns are calculated from the measured data, which have good agreement with the full-wave simulations. Using all-dielectric metamaterials, the design can be scaled down to find applications at optical frequencies. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Sun Y.,Lanzhou University | Sun Y.,Sichuan University | Abbott R.J.,University of St. Andrews | Li L.,Lanzhou University | And 2 more authors.
Molecular Ecology | Year: 2014

Hybridization and introgression can play an important role in speciation. Here, we examine their roles in the origin and evolution of Picea purpurea, a diploid spruce species occurring on the Qinghai-Tibet Plateau (QTP). Phylogenetic relationships and ecological differences between this species and its relatives, P. schrenkiana, P. likiangensis and P. wilsonii, are unclear. To clarify them, we surveyed sequence variation within and between them for 11 nuclear loci, three chloroplast (cp) and two mitochondrial (mt) DNA fragments, and examined their ecological requirements using ecological niche modelling. Initial analyses based on 11 nuclear loci rejected a close relationship between P. schrenkiana and P. purpurea. BP&P tests and ecological niche modelling indicated substantial divergence between the remaining three species and supported the species status of P. purpurea, which contained many private alleles as expected for a well-established species. Sequence variation for cpDNA and mtDNA suggested a close relationship between P. purpurea and P. wilsonii, while variation at the nuclear se1364 gene suggested P. purpurea was more closely related to P. likiangensis. Analyses of genetic divergence, Bayesian clustering and model comparison using approximate Bayesian computation (ABC) of nuclear (nr) DNA variation all supported the hypothesis that P. purpurea originated by homoploid hybrid speciation from P. wilsonii and P. likiangensis. The ABC analysis dated the origin of P. purpurea at the Pleistocene, and the estimated hybrid parameter indicated that 69% of its nuclear composition was contributed by P. likiangensis and 31% by P. wilsonii. Our results further suggested that during or immediately following its formation, P. purpurea was subject to organelle DNA introgression from P. wilsonii such that it came to possess both mtDNA and cpDNA of P. wilsonii. The estimated parameters indicated that following its origin, P. purpurea underwent an expansion during/after the largest Pleistocene glaciation recorded for the QTP. © 2013 John Wiley & Sons Ltd.

Zhang H.,Lanzhou University | Deng K.,Lanzhou University | Deng K.,Beifang University of Nationalities
Match | Year: 2015

The forcing number of a Kekulé structure of a hexagonal system is the smallest number of double bonds that determine the entire Kekulé structure. It is known that the maximum forcing number equals the Clar number for any hexagonal systems. In this paper by applying Z-transformation graph (or resonance graph) we show that the forcing numbers of all Kekulé structures of a hexagonal system H with a forcing edge form either the integer interval from 1 to the Clar number of H or with only the gap 2. © 2015 MATCH Commun. Math. Comput. Chem.

Mei Z.L.,Lanzhou University | Mei Z.L.,Nanjing Southeast University | Liu Y.S.,Lanzhou University | Yang F.,Lanzhou University | Cui T.J.,Nanjing Southeast University
Optics Express | Year: 2012

We propose, design, and implement a two-dimensional dc carpet cloak for steady electric field using the transformation optics (TO) method. Based on the circuit theory, we introduce a resistor network to mimic the resulting anisotropic conducting medium. The experimental prototype is fabricated using metal film resistors, and the measured results agree perfectly well with theoretical predictions. This study gives the first experimental verification of a dc carpet cloak, which expands the application of TO theory, and has potential applications in related areas. © 2012 Optical Society of America.

Liu M.,Lanzhou University | Liu M.,Gansu United Secondary Vocational School | Mei Z.L.,Lanzhou University | Ma X.,Lanzhou University | Cui T.J.,Nanjing Southeast University
Applied Physics Letters | Year: 2012

Based on the transformation optics method, we propose a dc illusion device, which can transform a metallic object into a magnified dielectric object using anisotropic conducting materials. Utilizing the analogy between electric conductivities and resistor networks, we design and fabricate the device using metal film resistors. The practical measurement data agree very well with simulation results. The proposed dc illusion device is easy to process and measure, and thus has potential applications in various sectors. © 2012 American Institute of Physics.

News Article | December 28, 2016

The first humans venturing onto the Tibetan Plateau, often called the “roof of the world,” faced one of the most brutal environments our species can endure. At an average elevation of over 4,500 meters, it is a cold and arid place with half the oxygen present at sea level. Science has long held that humans did not set foot in this alien place until 15,000 years ago, as suggested by archaeological evidence of the earliest known settlement on the northeastern fringe of the plateau 3,000 meters above sea level. But now new genetic data indicate this may have occurred much earlier—possibly as far back as the last ice age, 62,000 years ago. A better understanding of modern Tibetans’ genetic mix and diversity could help reconstruct the history of migration and population expansion in the region, and may help unravel the mystery of the ethnic origins of Tibetans—and of how humans have adapted to low-oxygen conditions at high altitudes. For the new study, researchers sequenced the entire genomes of 38 ethnic Tibetans and 39 Han Chinese (the country’s majority ethnic group), and compared the results with published genomic sequences of other ethnic groups around the world—information that allowed the team to pinpoint the common genetic origin of different populations and to get a better grasp on the history of migration in Tibet. “Tibetan-specific DNA sequences can be traced back to ancestors 62,000-38,000 years ago…This represents the earliest colonization of the Tibetan Plateau,” says Shuhua Xu, a population geneticist at the Chinese Institute of Sciences’ Shanghai Institutes for Biological Sciences. Xu’s work was published in September in the American Journal of Human Genetics, and presented at the American Society of Human Genetics’ annual meeting in Vancouver. Since that initial migration, as the ice age tightened its grip on the plateau, genetic mixing between Tibetans and non-Tibetans probably ground to a halt for tens of thousands of years—suggesting that movement into Tibet dropped to the minimum. “The migration routes were probably cut off by ice sheets,” Xu says. “It’s simply too harsh even for the toughest hunter-gatherers.” But about 15,000 to 9,000 years ago—after the so-called last glacial maximum (LGM), during which the Earth’s ice cover had reached its most extensive point and climate was at its harshest—people flocked into Tibet en masse. “It’s the most significant wave of migration that shaped the modern Tibetan gene pool,” Xu says. “We can really see rapid population expansion [on the plateau] during that time.” Interestingly, he adds, this was also when the common ancestor of Tibetans and Han Chinese split—contrary to a previous study suggesting that the divergence took place as late as 2,750 years ago. “This is the first study to sequence the entire genome of Tibetans, and the resolution is really impressive,” says Mark Aldenderfer, an archaeologist at the University of California, Merced, who was not involved in Xu’s study. The much earlier divergence between Tibetans and Han Chinese makes sense because there are continuous material cultures on the plateau since 15,000 years ago, he says. The study, Aldenderfer adds, “also provides fine details of how different populations from various directions may have combined their genes to ultimately create the people that we call Tibetans.” The data show that 94 percent of the present-day Tibetan genetic makeup came from modern humans—possibly those who ventured into Tibet in the second wave of migration—and the rest came from archaic hominins such as Denisovans, Neandertals and unknown groups. The modern part of the Tibetan genome shares 82 percent similarity with East Asians, 11 percent with Central Asians, and 6 percent with South Asians. “Among all ethic groups, Han Chinese are most closely related to Tibetans,” Xu says. The findings also reveal a startling genetic continuity since the plateau was first colonized 62,000 years ago. “This suggests that Tibet has always been populated—even during the toughest times as far as climate was concerned,” Xu says. That idea contradicts the commonly held notion that any early plateau dwellers would have been eliminated during harsh climate intervals such as LGM and another period known as the Younger Dryas between 12,900 and 11,600 years ago, says David Zhang, a geographer at the University of Hong Kong, who was not involved in Xu’s research. In 2002 Zhang and a colleague published a controversial study in Geophysical Review Letters showing marks of hands and feet from at least six individuals in rocks that were once soft mud, which was dated to 20,000 years ago at 4,000 meters above sea level in the heart of Tibet. Based on this they theorized that people were living in Tibet at the height of LGM, but the lack of archaeological finds near the site has cast doubt on this. “Many people don’t think it’s possible,” Aldenderfer says. “But there were plenty of places for [those early populations] to live where local conditions weren’t that bad, such as the big river valleys on the plateau.” The handprints and footprints were uncovered near one of the plateau’s many hot springs, which could have served as refuges for plants, animals and humans, he adds. Two independent archaeological studies presented at the 33rd International Geographical Congress, held in August in Beijing, also support the antiquity of Tibet settlement as suggested by Xu’s genetic data. A team led by archaeologist Guanghui Dong of Lanzhou University in Gansu province unveiled the earliest archaeological evidence of human presence—dating to 39,000-31,000 years ago—on the southeastern fringe of the Tibetan Plateau. The site, rich with stone tools and animal bones, lies at 2,500 meters above sea level at the bank of the Salween River. “This may represent one of the first steps of human colonization on the plateau,” Dong says. “Those hunter-gathers might then expand to the inner plateau along the river valley.” The second study pushes back the dates of human settlement above 4,000 meters by 4,000 years. Qinghai Normal University archaeologist Guangliang Hou and some of his colleagues recently excavated an archaeological site dated to 11,500 years ago, which is in line with the second and more important wave of migration that Xu’s study suggests. Hou said at the geographical congress that the site, close to a main tributary of the Yellow River, is teeming with charcoal—a telltale sign of fire use by humans. “This may have helped the plateau dwellers to survive the harsh conditions at such high elevations nearing the end of the Younger Dryas,” he says. “It’s increasingly clear that there has been much earlier and much more persistent human occupation of the plateau than we previously thought,” Aldenderfer says. He stresses, however, that pieces are still missing from the puzzle: “More excavations are required to close those gaps.”

Ji F.,Lanzhou University | Ji F.,Florida State University | Wu Z.,Florida State University | Huang J.,Lanzhou University | Chassignet E.P.,Florida State University
Nature Climate Change | Year: 2014

The global climate has been experiencing significant warming at an unprecedented pace in the past century. This warming is spatially and temporally non-uniform, and one needs to understand its evolution to better evaluate its potential societal and economic impact. Here, the evolution of global land surface air temperature trend in the past century is diagnosed using the spatial-temporally multidimensional ensemble empirical mode decomposition method. We find that the noticeable warming (>0.5 K) started sporadically over the global land and accelerated until around 1980. Both the warming rate and spatial structure have changed little since. The fastest warming in recent decades (>0.4 K per decade) occurred in northern mid-latitudes. From a zonal average perspective, noticeable warming (>0.2 K since 1900) first took place in the subtropical and subpolar regions of the Northern Hemisphere, followed by subtropical warming in the Southern Hemisphere. The two bands of warming in the Northern Hemisphere expanded from 1950 to 1985 and merged to cover the entire Northern Hemisphere. © 2014 Macmillan Publishers Limited.

He J.,CAS Lanzhou Institute of Modern Physics | He J.,Lanzhou University | He J.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In this paper it is proposed that the charged charmonium-like state Zc(3900) is a resonance above the threshold from the DD¯∗ interaction. The DD¯∗ interaction is described by the one-boson exchange model with light meson exchanges plus a short-range J/ψ exchange. The scattering amplitude is calculated within a Bethe-Salpeter equation approach, and the poles near the DD¯∗ threshold are searched. In the isoscalar sector, two poles found under the DD¯∗ threshold - i.e., bound states - have the quantum numbers IG(JPC)=0-(1+-) and 0+(1++). The latter can be related to the X(3872). In the isovector sector, a bound state with IG(JP)=1+(1+) is found with a large cutoff at about 3 GeV. If a cutoff at about 2 GeV is adopted with which a pole carrying the quantum number of the X(3872) is produced at an energy of about 3871 MeV, the pole for the bound state with 1+(1+) runs across the threshold to a second Riemann sheet and becomes a resonance above the DD¯∗ threshold, which can be identified with the Zc(3900). With such a cutoff, the DD¯∗ invariant mass spectrum is also investigated and the experimental results found by BESIII can be reproduced. © 2015 American Physical Society.

Wang G.,Arizona State University | Huang L.,Arizona State University | Huang L.,Lanzhou University | Lai Y.-C.,Arizona State University | And 2 more authors.
Physical Review Letters | Year: 2014

To search for and exploit quantum manifestations of classical nonlinear dynamics is one of the most fundamental problems in physics. Using optomechanical systems as a paradigm, we address this problem from the perspective of quantum entanglement. We uncover strong fingerprints in the quantum entanglement of two common types of classical nonlinear dynamical behaviors: periodic oscillations and quasiperiodic motion. There is a transition from the former to the latter as an experimentally adjustable parameter is changed through a critical value. Accompanying this process, except for a small region about the critical value, the degree of quantum entanglement shows a trend of continuous increase. The time evolution of the entanglement measure, e.g., logarithmic negativity, exhibits a strong dependence on the nature of classical nonlinear dynamics, constituting its signature. © 2014 American Physical Society.

Ci L.,Rice University | Song L.,Rice University | Jin C.,Japan National Institute of Advanced Industrial Science and Technology | Jariwala D.,Rice University | And 11 more authors.
Nature Materials | Year: 2010

Two-dimensional materials, such as graphene and monolayer hexagonal BN (h-BN), are attractive for demonstrating fundamental physics in materials and potential applications in next-generation electronics. Atomic sheets containing hybridized bonds involving elements B, N and C over wide compositional ranges could result in new materials with properties complementary to those of graphene and h-BN, enabling a rich variety of electronic structures, properties and applications. Here we report the synthesis and characterization of large-area atomic layers of h-BNC material, consisting of hybridized, randomly distributed domains of h-BN and C phases with compositions ranging from pure BN to pure graphene. Our studies reveal that their structural features and bandgap are distinct from those of graphene, doped graphene and h-BN. This new form of hybrid h-BNC material enables the development of bandgap-engineered applications in electronics and optics and properties that are distinct from those of graphene and h-BN. © 2010 Macmillan Publishers Limited. All rights reserved.

He J.,CAS Lanzhou Institute of Modern Physics | He J.,Lanzhou University | He J.,CAS Institute of Theoretical Physics
Nuclear Physics A | Year: 2014

Based on the high precision experimental data released by the CLAS Collaboration recently, the interaction mechanism of the photoproduction of Λ(1520) off a proton target is investigated within a Regge-plus-resonance approach. With the decay amplitudes predicted in the constituent quark model, the roles played by nucleon resonances are studied. It is found that N(2120) provides the most important contribution among the nucleon resonances predicted in the constituent quark model. The t channel contribution with Regge trajectories and the Λ intermediate u channel are responsible to the behaviors of the differential cross section at forward and backward angles, respectively. © 2014 Elsevier B.V.

Li K.,Sun Yat Sen University | Zhang L.-Y.,Sun Yat Sen University | Yan C.,Sun Yat Sen University | Wei S.-C.,Sun Yat Sen University | And 4 more authors.
Journal of the American Chemical Society | Year: 2014

Stepwise synthesis of nanosized Pd-Ru heteronuclear metal-organic cages from predesigned redox- and photo-active Ru(II)-metalloligand and naked Pd(II) ion is described. The resulting cage shows rhombododecahedral shape and contains a 5350 Å3 cavity and 12 open windows, facilitating effective trapping of both polar and nonpolar guest molecules. Protection of photosensitive guests against UV radiation is studied. © 2014 American Chemical Society.

Li H.,Tohoku University | Li H.,Lanzhou University | Yin S.,Tohoku University | Wang Y.,Lanzhou University | Sato T.,Tohoku University
Journal of Catalysis | Year: 2012

Nitrogen-doped titanium oxide (TiO 2-xN y) nanocrystalline with different phase of anatase, rutile or brookite was coupled with CaAl 2O 4:(Eu, Nd) particles by planetary ball milling treatment. The effect of phase structures on the persistent photocatalytic activity of a CaAl 2O 4:(Eu, Nd)/TiO 2- xN y composite was evaluated for the oxidative destruction of NO. The persistent catalytic degradation of NO by TiO 2- xN y was realized in the presence of CaAl 2O 4:(Eu, Nd), which shows a long afterglow luminescence. The persistent photocatalytic property of composites changed depending on the crystalline phase of TiO 2-xN y, i.e., the persistent photocatalytic property of CaAl 2O 4:(Eu, Nd) combined with brookite type TiO 2-xN y was superior to those of anatase or rutile phase TiO 2-xN y. © 2011 Elsevier Inc. All rights reserved.

Cheng X.,Lanzhou University | Lu H.,Hohai University
Nonlinear Analysis: Real World Applications | Year: 2012

In this paper, we establish the product formula for the fixed point index on product cone, and the relation between LeraySchauder degree and a pair of strict lower and upper solutions for a (p 1,p 2)-Laplacian system. Based on the product formula of the fixed point index and LeraySchauder degree theory, we deal with the multiplicity of positive solutions for a class of (p 1,p 2)-Laplacian systems. As applications, we prove the global existence of positive solutions for a multi-parameter system of (p 1,p 2)-Laplacian equations with respect to parameters. © 2012 Elsevier Ltd. All rights reserved.

Fu S.,Northwest Normal University | Fu S.,Guilin University of Electronic Technology | Zhang L.,Northwest Normal University | Hu P.,Lanzhou University
Nonlinear Analysis: Real World Applications | Year: 2013

In this paper, the global behavior of solutions is investigated for a Lotka-Volterra predator-prey system with prey-stage structure. First, we can see that the stability properties of nonnegative equilibria for the weakly coupled reaction-diffusion system are similar to that for the corresponding ODE system, that is, linear self-diffusions do not drive instability. Second, using Sobolev embedding theorems and bootstrap arguments, the existence and uniqueness of nonnegative global classical solution for the strongly coupled cross-diffusion system are proved when the space dimension is less than 10. Finally, the existence and uniform boundedness of global solutions and the stability of the positive equilibrium point for the cross-diffusion system are studied when the space dimension is one. It is found that the cross-diffusion system is dissipative if the diffusion matrix is positive definite. Furthermore, cross diffusions cannot induce pattern formation if the linear diffusion rates are sufficiently large. © 2013 Elsevier Ltd. All rights reserved.

Zhang J.-L.,Lanzhou University | Flowers T.J.,University of Sussex | Wang S.-M.,Lanzhou University
Plant and Soil | Year: 2010

The negative impact of soil salinity on agricultural yields is significant. For agricultural plants, sensitivity to salinity is commonly (but not exclusively) due to the abundance of Na + in the soil as excess Na + is toxic to plants. We consider reducing Na + uptake to be the key, as well as the most efficient approach, to control Na + accumulation in crop plants and hence to improve their salt resistance. Understanding the mechanism of Na + uptake by the roots of higher plants is crucial for manipulating salt resistance. Hence, the aim of this review is to highlight and discuss recent advances in our understanding of the mechanisms of Na + uptake by plant roots at both physiological and molecular levels. We conclude that continued efforts to investigate the mechanisms of root Na + uptake in higher plants are necessary, especially that of low-affinity Na + uptake, as it is the means by which sodium enters into plants growing in saline soils. © Springer Science + Business Media B.V. 2009.

Wang J.,Lanzhou University | Zhu S.,Lanzhou University | Zhang W.,Lanzhou University | Lu H.,University of Technology, Sydney
Energy | Year: 2010

Electric load forecasting is crucial for managing electric power systems economically and safely. This paper presents a new combined model for electric load forecasting based on the seasonal ARIMA forecasting model, the seasonal exponential smoothing model and the weighted support vector machines. The combined model can effectively count for the seasonality and nonlinearity shown in the electric load data and give more accurate forecasting results. The adaptive particle swarm optimization is employed to optimize the weight coefficients in the combined forecasting model. The proposed combined model has been compared with the individual models and the other combined model reported in the literature and its results are promising. © 2009 Elsevier Ltd.

Wang J.,Dongbei University of Finance and Economics | Dong Y.,Lanzhou University | Jiang H.,Florida State University
Energy Conversion and Management | Year: 2014

Electricity is an indispensable energy source for modern social and economic development. However, large-scale blackouts can cause incalculable loss to society. In 2012, three major Indian power grids collapsed, resulting in the interruption of the electricity supply to over 600 million people. To avoid an event like that, China needs to forecast the power generation and consumption of eight power grids effectively. This paper first analyzes the characteristics of eight power grids and then proposes a combined model based on three improved grey models optimized by a differential evolution algorithm to predict electricity production and consumption of each power grid. The optimized combined forecasting model provides a better prediction than other models, and it is also the most workable and satisfactory model. Experiment results show electricity production and consumption would increase. In consideration of the real situation and existing problems, some suggestions are proposed. The government could decrease thermal power and exploit renewable energy power, like hydroelectric power, wind power and solar power, to ensure the safe and reliable operation of China's major power grids and protect environment. © 2014 Elsevier Ltd. All rights reserved.

Wang W.-Z.,Tianshui Normal University | Wei X.-P.,Lanzhou University
Computational Materials Science | Year: 2011

Based on the first-principle calculations within density functional theory of electronic structure, we propose that the CuHg2Ti-type intermetallic ternary compound Mn2ZnCa is strong candidate for half-metallic (HM) antiferromagnet (AFM), the HM-AFM nature in Mn 2ZnCa originates from d-d orbital hybridization. We also find that the Fermi level just locates in the gap of spin-down states, and the HM properties of Mn2ZnCa is kept within the wide range of 5.91 and 6.60 where exhibit perfect 100% spin polarization of the conduction electrons. Our investigations also indicate the atom coordination surroundings have a great influence on the electron structure. © 2011 Elsevier B.V. All rights reserved.

Li Y.,Lanzhou University | Li Y.,Rice University | Gao W.,Rice University | Ci L.,Rice University | And 2 more authors.
Carbon | Year: 2010

We have investigated a simple approach for the deposition of platinum (Pt) nanoparticles onto surfaces of graphite oxide (GO) nanosheets with particle size in the range of 1-5 nm by ethylene glycol reduction. During Pt deposition, a majority of oxygenated functional groups on GO was removed, which resulted in a Pt/chemically converted graphene (Pt/CCG) hybrid. The electrochemically active surface areas of Pt/CCG and a comparative sample of Pt/multi-walled carbon nanotubes (Pt/MWCNT) are 36.27 and 33.43 m2/g, respectively. The Pt/CCG hybrid shows better tolerance to CO for electro-oxidation of methanol compared to the Pt/MWCNT catalyst. Our study demonstrates that CCG can be an alternative two-dimensional support for Pt in direct methanol fuel cells. © 2009 Elsevier Ltd. All rights reserved.

Yang D.,Lanzhou University | Wang L.,Lanzhou University | Han F.,Lanzhou University | Li D.,Lanzhou University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2015

A direct, facile, and highly diastereo- and enantio-selective dearomatization reaction of β-naphthol derivatives with aziridines has been developed for the first time. A newly designed Box-OH ligand was employed for an in situ generated magnesium catalyst and proved to be efficient. The corresponding dearomatization product was transformed into a polycyclic scaffold and polyhydroxylated compound. 1H NMR studies revealed the activation mode of the dearomatization process of β-naphthols, and a clear positive nonlinear effect was observed in the reaction, and provides insight into the coordination environment around the MgII center and the possible active species. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

Dong Y.,Lanzhou University | Wang J.,Lanzhou University | Jiang H.,Florida State University | Shi X.,Lanzhou University
Applied Energy | Year: 2013

The exploration of wind energy has become one of the most significant aims for countries all around the world. This is due to its low impact on the environment and its sustainable development. Therefore, it is very important to develop an effective and scientific way to evaluate wind resource potential and so that suitable wind turbines can be chosen. In this study, the 4-times daily wind speed data for the past 63. years in Huitengxile of Inner Mongolia in China was collected first to do mutation tests using Sliding T-test and Sliding F-test. The test results indicated that the wind speeds exhibited a significant change in the mean value and a big variation in variance. Secondly, in order to improve the assessment accuracy, three intelligent optimization algorithms were applied to estimate Weibull's parameters, including Particle Swarm Optimization (PSO), Differential Evolution (DE) and Genetic Algorithm (GA). Finally, some new criteria, such as matching index, turbine cost index and the integrated matching index, were proposed in order to choose the most fitting wind turbine in accordance with the local environment and economic cost. © 2013 Elsevier Ltd.

Guo Z.-H.,CAS Institute of Atmospheric Physics | Wu J.,Lanzhou University | Lu H.-Y.,University of Technology, Sydney | Wang J.-Z.,Lanzhou University
Knowledge-Based Systems | Year: 2011

Wind energy, which is intermittent by nature, can have a significant impact on power grid security, power system operation, and market economics, especially in areas with a high level of wind power penetration. Wind speed forecasting has been a vital part of wind farm planning and the operational planning of power grids with the aim of reducing greenhouse gas emissions. Improving the accuracy of wind speed forecasting algorithms has significant technological and economic impacts on these activities, and significant research efforts have addressed this aim recently. However, there is no single best forecasting algorithm that can be applied to any wind farm due to the fact that wind speed patterns can be very different between wind farms and are usually influenced by many factors that are location-specific and difficult to control. In this paper, we propose a new hybrid wind speed forecasting method based on a back-propagation (BP) neural network and the idea of eliminating seasonal effects from actual wind speed datasets using seasonal exponential adjustment. This method can forecast the daily average wind speed one year ahead with lower mean absolute errors compared to figures obtained without adjustment, as demonstrated by a case study conducted using a wind speed dataset collected from the Minqin area in China from 2001 to 2006. © 2011 Elsevier B.V. All rights reserved.

Finazzo S.I.,University of Sao Paulo | Nielsen M.,University of Sao Paulo | Liu X.,Lanzhou University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Using the QCD sum rules we test if the charmonium-like structure Y(4274), observed in the J/Ψ invariant mass spectrum, can be described with a DsD̄s0(2317)+h.c. molecular current with JPC=0Ψ+. We consider the contributions of condensates up to dimension ten and we work at leading order in α s. We keep terms which are linear in the strange quark mass ms. The mass obtained for such state is mDsDs0=(4.78±0.54) GeV. We also consider a molecular 0-+ DD0(2400)+h.c. current and we obtain mDD0=(4.55±0.49)GeV. Our study shows that the newly observed Y(4274) in the J/Ψ invariant mass spectrum can be, considering the uncertainties, described using a molecular charmonium current. © 2011 Elsevier B.V.

He J.,CAS Lanzhou Institute of Modern Physics | He J.,Lanzhou University | He J.,CAS Institute of Theoretical Physics
Physical Review C - Nuclear Physics | Year: 2014

The interaction mechanism of the Σ(1385) photoproduction from proton γp→K+Σ0(1385) is investigated within a Regge-plus-resonance approach based on the experimental data released by the CLAS Collaboration recently. The t channel and the u channel are responsible for the behaviors of differential cross sections at forward and backward angles, respectively. The contributions from nucleon resonances including N* and Δ*, which are determined by the predicted decay amplitudes in the constituent quark model, are found to be small, but the F35 state Δ(2000) is essential to reproduce the differential cross section. © 2014 American Physical Society.

He J.,CAS Lanzhou Institute of Modern Physics | He J.,Lanzhou University | He J.,CAS Institute of Theoretical Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

Very recently, two hidden-charmed resonances Pc(4380) and Pc(4450) consistent with pentaquark states were observed at the LHCb detector. The two Pc states locate just below the D-σc* and D-*σc thresholds with mass of gaps about 5 and 15 MeV, respectively. Inspired by this fact we perform a dynamical investigation about the D-σc*(2520) and D-*σc(2455) interactions which are described by the meson exchanges. A bound state which carries spin-parity JP=3/2- is produced from the D-σc*(2520) interaction, which is consistent with the Pc(4380) observed at the LHCb detector. From the D*σc(2455) interaction, a bound state with 5/2+ is produced, which can be related to the Pc(4450). The results suggest that the Pc(4380) and Pc(4450) are good candidates of D-σc*(2520) and D-*σc(2455) molecular states, respectively. © 2015.

Albuquerque R.M.,University of Sao Paulo | Liu X.,Lanzhou University | Nielsen M.,University of Sao Paulo
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We use the QCD sum rules to study possible B c-like molecular states. We consider isoscalar J P=0 + and J P=1 + D (*)B (*) molecular currents. We consider the contributions of condensates up to dimension eight and we work at leading order in α s. We obtain for these states masses around 7 GeV. © 2012 Elsevier B.V.

Meng X.,Nankai University | Meng X.,CAS Institute of Theoretical Physics | Du X.,Nankai University | Du X.,Lanzhou University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

In the generalized Einstein-aether theories by taking a special form of the Lagrangian density of aether field, the possibility of Einstein-aether theory as an alternative to dark energy model is discussed in detail, that is, taking a special aether field as a dark energy candidate. We compute the joint statistic constraints on this special model's parameters by using the recent type Ia supernovae (SNe Ia) data, the Cosmic Microwave Background (CMB) shift parameter data, and the Baryonic Acoustic Oscillations (BAOs) data traced by the Sloan Digital Sky Survey (SDSS). Furthermore, we analyze other constrains from the Observational Hubble parameter Data (OHD). The comparison with the standard cosmological model (cosmological constant Λ Cold Dark Matter (ΛCDM) model) is clearly shown with new features; also we comment on an interesting relation between the coupling constant M in this model and the possible existence of a special accelerating scale in the MOdified Newtonian Dynamics (MOND) model initially given by Milgrom with the hope for interpreting the galaxy rotation curves without introducing mysterious dark matter. © 2012.

He J.,CAS Lanzhou Institute of Modern Physics | He J.,Lanzhou University | He J.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

In this work the BB¯∗/DD¯∗ system is studied in the Bethe-Salpeter approach with quasipotential approximation. In our calculation both direct and cross diagrams are included in the one-boson-exchange potential. The numerical results indicate the existence of an isoscalar bound state DD¯∗ with JPC=1++, which may be related to the X(3872). In the isovector sector, no bound state is produced from the interactions of DD¯∗ and BB¯∗, which suggests the molecular state explanations for Zb(10610) and Zc(3900) are excluded. © 2014 American Physical Society.

Ding S.-Y.,Lanzhou University | Gao J.,Lanzhou University | Wang Q.,Lanzhou University | Wang Q.,CAS Beijing National Laboratory for Molecular | And 4 more authors.
Journal of the American Chemical Society | Year: 2011

Covalent organic frameworks (COFs) are crystalline porous solids with well-defined two- or three-dimensional molecular structures. Although the structural regularity provides this new type of porous material with high potentials in catalysis, no example has been presented so far. Herein, we report the first application of a new COF material, COF-LZU1, for highly efficient catalysis. The easily prepared imine-linked COF-LZU1 possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. Via a simple post-treatment, a Pd(II)-containing COF, Pd/COF-LZU1, was accordingly synthesized, which showed excellent catalytic activity in catalyzing the Suzuki-Miyaura coupling reaction. The superior utility of Pd/COF-LZU1 in catalysis was elucidated by the broad scope of the reactants and the excellent yields (96-98%) of the reaction products, together with the high stability and easy recyclability of the catalyst. We expect that our approach will further boost research on designing and employing functional COF materials for catalysis. © 2011 American Chemical Society.

Wang H.-L.,Lanzhou University | Li Z.,Tsinghua University | Wang G.-W.,Lanzhou University | Yang S.-D.,Lanzhou University
Chemical Communications | Year: 2011

A novel protocol for the preparation of various 3-alkylideneoxindoles via a silver-catalyzed aromatic C-H functionalization has been developed. The process is simple, environmentally conscious, and avoids the use of abundant bases, oxidants, or other additives. © 2011 The Royal Society of Chemistry.

Guo J.,Florida State University | Guo J.,Lanzhou University | Pang X.,Florida State University | Zhou H.-X.,Florida State University
Structure | Year: 2015

Allostery is an essential means for regulating biomolecular functions and provides unique opportunities for drug design, yet our ability to elucidate allosteric mechanisms remains limited. Here, based on extensive molecular dynamics simulations, we present an atomistic picture of the pathways mediating the allosteric regulation of the PPIase domain of Pin1 by its WW domain. Two pathways jointly propagate the action of substrate-WW binding to produce closure and rigidification of three PPIase catalytic-site loops. One pathway preexists in the apo protein, but remains dormant until substrate-WW binding completes the second. The reduction in conformational entropy and preorganization of the catalytic-site loops observed here may explain why substrate-WW binding enhances ligand affinity and catalytic activity of the PPIase domain and suggest a combination drug therapy for Pin1-related diseases. Whereas the traditional view of allostery has emphasized conformational transition, our study identifies a distinct role of conformational dynamics in eliciting allostery. © 2015 Elsevier Ltd All rights reserved.

Lou Y.-Q.,Tsinghua University | Hu X.-Y.,Lanzhou University
Monthly Notices of the Royal Astronomical Society | Year: 2016

We present a theoretical model framework for general polytropic (GP) hydrodynamic cylinder under self-gravity of infinite length with axial uniformity and axisymmetry. For self-similar dynamic solutions, we derive valuable integrals, analytic asymptotic solutions, sonic critical curves, shock conditions, and global numerical solutions with or without expansion shocks. Among others, we investigate various dynamic solutions featured with central free-fall asymptotic behaviours, corresponding to a collapsed mass string with a sustained dynamic accretion from a surrounding mass reservoir. Depending on the allowed ranges of a scaling index a < -1, such cylindrical dynamic mass accretion rate could be steady, increasing with time and decreasing with time. Physically, such a collapsed mass string or filament would break up into a sequence of sub-clumps and segments as induced by gravitational Jeans instabilities. Depending on the scales involved, such sub-clumps would evolve into collapsed objects or gravitationally bound systems. In diverse astrophysical and cosmological contexts, such a scenario can be adapted on various temporal, spatial and mass scales to form a chain of collapsed clumps and/or compact objects. Examples include the formation of chains of protostars, brown dwarfs and gaseous planets along molecular filaments; the formation of luminous massive stars along magnetized spiral arms and circum-nuclear starburst rings in barred spiral galaxies; the formation of chains of compact stellar objects such as white dwarfs, neutron stars, and black holes along a highly condensed mass string. On cosmological scales, one can perceive the formation of chains of galaxies, chains of galaxy clusters or even chains of supermassive and hypermassive black holes in the Universe including the early Universe. All these chains referred to above include possible binaries. © 2016 The Authors.

Guo Z.,CAS Institute of Atmospheric Physics | Zhao W.,Lanzhou University | Lu H.,University of Technology, Sydney | Wang J.,Lanzhou University
Renewable Energy | Year: 2012

In this paper, a modified EMD-FNN model (empirical mode decomposition (EMD) based feed-forward neural network (FNN) ensemble learning paradigm) is proposed for wind speed forecasting. The nonlinear and non-stationary original wind speed series is first decomposed into a finite and often small number of intrinsic mode functions (IMFs) and one residual series using EMD technique for a deep insight into the data structure. Then these sub-series except the high frequency are forecasted respectively by FNN whose input variables are selected by using partial autocorrelation function (PACF). Finally, the prediction results of the modeled IMFs and residual series are summed to formulate an ensemble forecast for the original wind speed series. Further more, the developed model shows the best accuracy comparing with basic FNN and unmodified EMD-based FNN through multi-step forecasting the mean monthly and daily wind speed in Zhangye of China. © 2011 Elsevier Ltd.

Liu Z.-Q.,Lanzhou University | Zhao L.,Gannan Normal University | Shang X.,Lanzhou University | Cui Z.,Lanzhou University
Organic Letters | Year: 2012

An unexpected Cu-catalyzed oxidative cleavage of the C(sp 3)-C(sp 3) bond in glycol ethers by using air or molecular oxygen as the terminal stoichiometric oxidant is demonstrated. As a result, the corresponding α-acyloxy ethers and formates of 1,2-ethanediol are formed by direct coupling of carboxylic acids and aldehydes with glycol ethers under the reaction conditions. This method represents the first example of Cu-catalyzed aerobic cleavage of saturated C-C bond in ethers. © 2012 American Chemical Society.

Wang Z.-C.,Lanzhou University | Wu J.,York University
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2010

We obtain full information about the existence and non-existence of travelling wave solutions for a general class of diffusive Kermack-McKendrick SIR models with nonlocal and delayed disease transmission. We show that this information is determined by the basic reproduction number of the corresponding ordinary differential model, and the minimal wave speed is explicitly determined by the delay (such as the latent period) and non-locality in disease transmission, and the spatial movement pattern of the infected individuals. The difficulty is the lack of order-preserving property of the general system, and we obtain the threshold dynamics for spatial spread of the disease by constructing an invariant cone and applying Schauder's fixed point theorem. © 2009 The Royal Society.

Li R.,Accelerator Centre | Li R.,CAS Lanzhou Institute of Modern Physics | Li M.-F.,Lanzhou University | Ren J.-R.,Lanzhou University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

We extend the recently proposed Kerr/CFT correspondence to examine the dual conformal field theory of four-dimensional Kaluza-Klein black hole in Einstein-Maxwell-Dilaton theory. For the extremal Kaluza-Klein black hole, the central charge and temperature of the dual conformal field are calculated following the approach of Guica, Hartman, Song and Strominger. Meanwhile, we show that the microscopic entropy given by the Cardy formula agrees with Bekenstein-Hawking entropy of extremal Kaluza-Klein black hole. For the non-extremal case, by studying the near-region wave equation of a neutral massless scalar field, we investigate the hidden conformal symmetry of Kaluza-Klein black hole, and find the left and right temperatures of the dual conformal field theory. Furthermore, we find that the entropy of non-extremal Kaluza-Klein black hole is reproduced by Cardy formula. © 2010 Elsevier B.V.

Lu J.,Tsinghua University | Hu J.,Tsinghua University | Song Y.,Tsinghua University | Ju Y.,Tsinghua University | Ju Y.,Lanzhou University
Organic Letters | Year: 2011

A novel functional tweezer based on uracil-appended glycyrrhetinic acid with excellent gelation ability was synthesized, and the gel could transform to sol by F- and Hg2+. © 2011 American Chemical Society.

Zhang J.-L.,Lanzhou University | Flowers T.J.,University of Sussex | Wang S.-M.,Lanzhou University
Plant and Soil | Year: 2013

Background and aims: Salinity is an increasing problem for agricultural production worldwide. Understanding how Na+ enters plants is important if reducing Na+ influx, a key component of the regulation of Na+ accumulation in plants and improving salt tolerance of crop plants, is to be achieved. Our previous work indicated that two distinct low-affinity Na+ uptake pathways exist in the halophyte Suaeda maritima. Here, we report the external NaCl concentration at which uptake switches from pathway 1 to pathway 2 and the kinetics of the interaction between external K+ concentration and Na+ uptake and accumulation in S. maritima in order to determine the roles of K+ transporters or channels in low-affinity Na+ uptake. Methods: Na+ influx, Na+ and K+ accumulations in S. maritima exposed to various concentrations of NaCl (0-200 mM) were analyzed in the absence and presence of the inhibitors TEA and Ba+ (5 mM TEA or 3 mM Ba2+) or KCl (0, 10 or 50 mM). Results: Our earlier proposal was confirmed and extended that there are two distinct low-affinity Na+ uptake pathways in S. maritima: pathway 1 might be mediated by a HKT-type transporter under low salinity conditions and pathway 2 by an AKT1-type channel or a KUP/HAK/KT type transporter under high salinity conditions. The external NaCl concentration at which two distinct low-affinity Na+ uptake switches from pathway 1 to pathway 2, the 'turning point', is between 90 and 95 mM. Over a short period (12 h) of Na+ and K+ treatments, a low concentration of K+ (10 mM) facilitated Na+ uptake by S. maritima under high salinity (100-200 mM NaCl), whether or not the plants had been subjected to a longer (3 d) period of K+ starvation. The kinetics suggests that low concentration of K+ (10 mM) might activate AKT1-type channels or KUP/HAK/KT-type transporters under high salinity (100-200 mM NaCl). Conclusions: The turning-point of external NaCl concentrations for the two low-affinity Na+ uptake pathways in Suaeda maritima is between 90 and 95 mM. A low concentration of K+ (10 mM) might activate AKT1 or KUP/HAK/KT and facilitate Na+ uptake under high salinity (100-200 mM NaCl). The kinetics of K+ on Na+ uptake and accumulation in S maritima are also consistent with there being two low-affinity Na+ uptake pathways. © 2012 Springer Science+Business Media Dordrecht.

Li Y.,Lanzhou University | Chen Q.,University of Tokyo | Chen Q.,Xiamen University | He D.,Lanzhou University | Li J.,Lanzhou University
Nano Energy | Year: 2014

Radial pn junction Si micro/nano-wire arrays exhibit unique optical and electrical characteristics for building photovoltaic devices with high performance-to-cost ratios over traditional planar junction bulk Si structures. Through optimizing the structural parameters, such as wire diameter and array periodicity, antireflection even superior to the optimized antireflective coatings can be realized. In the meantime, excellent light confinement is easily achievable for Si micro/nano-wire arrays using much less materials compared to their bulk Si counterparts. From the electrical aspect, the radial pn junction configuration formed around the wires significantly reduces the minority carrier collection length along the radial direction, providing outstanding tolerance to material qualities. Owing to these charming properties, radial junction Si micro/nano-wire array-based solar cells have been attracting extensive attention. The power conversion efficiency has also made huge progress from <1% to the present >12% in less than 10 years. With cell performance improvement, the number of research papers regarding theoretical understanding and optimization of the optical and electrical processes, experimental reports of the related solar cells has also surged, also including review papers. Accordingly, in this paper we are focusing on the recent progress, following a brief but systematic introduction to the related topic. Then the issues needing to be addressed for further improving the optical and electrical structures and cell performance are summarized. Following that, several other advanced solar cells employing Si micro/nano-wire arrays as a platform are introduced. © 2014 Elsevier Ltd.

News Article | December 4, 2015

Rice University researchers who pioneered the development of laser-induced graphene have configured their discovery into flexible, solid-state microsupercapacitors that rival the best available for energy storage and delivery. The devices developed in the lab of Rice chemist James Tour are geared toward electronics and apparel. They are the subject of a new paper in the journal Advanced Materials. Microsupercapacitors are not batteries, but inch closer to them as the technology improves. Traditional capacitors store energy and release it quickly (as in a camera flash), unlike common lithium-ion batteries that take a long time to charge and release their energy as needed. Rice’s microsupercapacitors charge 50 times faster than batteries, discharge more slowly than traditional capacitors, and match commercial supercapacitors for both the amount of energy stored and power delivered. The devices are manufactured by burning electrode patterns with a commercial laser into plastic sheets in room-temperature air, eliminating the complex fabrication conditions that have limited the widespread application of microsupercapacitors. The researchers see a path toward cost-effective, roll-to-roll manufacturing. “It’s a pain in the neck to build microsupercapacitors now,” Tour says. “They require a lot of lithographic steps. But these we can make in minutes: We burn the patterns, add electrolyte and cover them.” Their capacitance of 934 microfarads per square centimeter and energy density of 3.2 milliwatts per cubic centimeter rival commercial lithium thin-film batteries, with a power density two orders of magnitude higher than batteries, the researchers claimed. The devices displayed long life and mechanical stability when repeatedly bent 10,000 times. Their energy density is due to the nature of laser-induced graphene (LIG). Tour and his group discovered last year that heating a commercial polyimide plastic sheet with a laser burned everything but the carbon from the top layer, leaving a form of graphene. But rather than a flat sheet of hexagonal rings of atoms, the laser left a spongy array of graphene flakes attached to the polyimide, with high surface area. The researchers treated their LIG patterns — interdigitated like folded hands — with manganese dioxide, ferric oxyhydroxide or polyaniline through electrodeposition and turned the resulting composites into positive and negative electrodes. The composites could then be formed into solid-state microsupercapacitors with no need for current collectors, binders or separators. Tour is convinced the day is coming when supercapacitors replace batteries entirely, as energy storage systems will charge in minutes rather than hours. “We’re not quite there yet, but we’re getting closer all the time,” he says. “In the interim, they’re able to supplement batteries with high power. What we have now is as good as some commercial supercapacitors. And they’re just plastic.” Rice graduate students Lei Li and Jibo Zhang and alumnus Zhiwei Peng are lead authors of the paper. Co-authors are Rice postdoctoral researchers Yongsung Ji, Nam Dong Kim, Gedeng Ruan, and Yang Yang and graduate students Yilun Li, Ruquan Ye, and Huilong Fei; Caitian Gao, a visiting graduate student at Rice from Lanzhou University, China; and Qifeng Zhong, a visiting graduate student at Rice from Southeast University, Nanjing, China. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of materials science and nanoengineering and of computer science. The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative and the Chinese Scholarship Council supported the research.

Home > Press > Scientists see the light on microsupercapacitors: Rice University's laser-induced graphene makes simple, powerful energy storage possible Abstract: ice University researchers who pioneered the development of laser-induced graphene have configured their discovery into flexible, solid-state microsupercapacitors that rival the best available for energy storage and delivery. The devices developed in the lab of Rice chemist James Tour are geared toward electronics and apparel. They are the subject of a new paper in the journal Advanced Materials. Microsupercapacitors are not batteries, but inch closer to them as the technology improves. Traditional capacitors store energy and release it quickly (as in a camera flash), unlike common lithium-ion batteries that take a long time to charge and release their energy as needed. Rice's microsupercapacitors charge 50 times faster than batteries, discharge more slowly than traditional capacitors and match commercial supercapacitors for both the amount of energy stored and power delivered. The devices are manufactured by burning electrode patterns with a commercial laser into plastic sheets in room-temperature air, eliminating the complex fabrication conditions that have limited the widespread application of microsupercapacitors. The researchers see a path toward cost-effective, roll-to-roll manufacturing. "It's a pain in the neck to build microsupercapacitors now," Tour said. "They require a lot of lithographic steps. But these we can make in minutes: We burn the patterns, add electrolyte and cover them." Their capacitance of 934 microfarads per square centimeter and energy density of 3.2 milliwatts per cubic centimeter rival commercial lithium thin-film batteries, with a power density two orders of magnitude higher than batteries, the researchers claimed. The devices displayed long life and mechanical stability when repeatedly bent 10,000 times. Their energy density is due to the nature of laser-induced graphene (LIG). Tour and his group discovered last year that heating a commercial polyimide plastic sheet with a laser burned everything but the carbon from the top layer, leaving a form of graphene. But rather than a flat sheet of hexagonal rings of atoms, the laser left a spongy array of graphene flakes attached to the polyimide, with high surface area. The researchers treated their LIG patterns -- interdigitated like folded hands -- with manganese dioxide, ferric oxyhydroxide or polyaniline through electrodeposition and turned the resulting composites into positive and negative electrodes. The composites could then be formed into solid-state microsupercapacitors with no need for current collectors, binders or separators. Tour is convinced the day is coming when supercapacitors replace batteries entirely, as energy storage systems will charge in minutes rather than hours. "We're not quite there yet, but we're getting closer all the time," he said. "In the interim, they're able to supplement batteries with high power. What we have now is as good as some commercial supercapacitors. And they're just plastic." Rice graduate students Lei Li and Jibo Zhang and alumnus Zhiwei Peng are lead authors of the paper. Co-authors are Rice postdoctoral researchers Yongsung Ji, Nam Dong Kim, Gedeng Ruan and Yang Yang and graduate students Yilun Li, Ruquan Ye and Huilong Fei; Caitian Gao, a visiting graduate student at Rice from Lanzhou University, China; and Qifeng Zhong, a visiting graduate student at Rice from Southeast University, Nanjing, China. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of materials science and nanoengineering and of computer science. The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative and the Chinese Scholarship Council supported the research. About Rice University Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,888 undergraduates and 2,610 graduate students, Rice’s undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance. Follow Rice News and Media Relations via Twitter @RiceUNews For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Zhang H.F.,Lanzhou University | Lombardo U.,National Institute of Nuclear Physics, Italy | Zuo W.,CAS Lanzhou Institute of Modern Physics
Physical Review C - Nuclear Physics | Year: 2010

We present a numerical study of shear viscosity and thermal conductivity of symmetric nuclear matter, pure neutron matter, and β-stable nuclear matter, in the framework of the Brueckner theory. The calculation of in-medium cross sections and nucleon effective masses is performed with a consistent two- and three-body interaction. The investigation covers a wide baryon density range as needed in the applications to neutron stars. The results for the transport coefficients in β-stable nuclear matter are used to make preliminary predictions on the damping time scales of nonradial modes in neutron stars. © 2010 The American Physical Society.

Zhao G.,Harbin Institute of Technology | Yang C.,Harbin Institute of Technology | Guo L.,Harbin Institute of Technology | Sun H.,Harbin Institute of Technology | And 3 more authors.
Chemical Communications | Year: 2012

An efficient methodology for the functionalization of sp 3 C-H bond adjacent to nitrogen has been developed utilizing visible light-induced photoredox catalysis. Through optimization of solvent and light source, the reaction can be rapidly achieved to provide the desired product under mild reaction conditions. © The Royal Society of Chemistry.

Yang Y.,Lanzhou University | Wang Y.,Harbin Institute of Technology | Fu F.,City University London
Thin-Walled Structures | Year: 2014

Eight stiffened square concrete-filled steel tubular (CFST) stub columns with slender sections of encasing steel and two non-stiffened counterparts were tested subjected to axial compressive load. Four types of reinforcement stiffeners and steel tensile strips were introduced to postpone local buckling of steel tubes, in which the tensile strip was first used as stiffener in CFSTs. The stiffening mechanism, failure modes of concrete and steel tubes, strength and ductility of stiffened square CFSTs were also studied during the experimental research. A numerical modeling program was developed and verified against the experimental data. The program incorporates the effect of the stiffeners on postponing local buckling of the tube and the tube confinement on concrete core. Extensive parametric analysis was also conducted to examine the influencing parameters on mechanical properties of stiffened square CFSTs. © 2014 Elsevier Ltd.

Yin J.,University of Birmingham | Harrison R.M.,University of Birmingham | Chen Q.,Lanzhou University | Rutter A.,University of Wisconsin - Madison | Schauer J.J.,University of Wisconsin - Madison
Atmospheric Environment | Year: 2010

Airborne fine particulate matter (PM2.5) has been collected at two sites in the West Midlands conurbation, UK, representing urban background and rural locations. Chemical analyses have been carried out for major anions, trace metals, total OC and EC, and for individual organic marker species including n-alkanes, hopanes, PAHs, organic acids and sterols. Source apportionment has been conducted using both a pragmatic mass closure model and the US EPA chemical mass balance (CMB) model. The pragmatic mass closure model is well able to account for the measured PM2.5 mass in terms of chemical/source components, and the chemical mass balance model has been used to apportion the carbonaceous component of the aerosol. The dominant components of PM2.5 at both sites are secondary inorganic (sulphate and nitrate) and carbonaceous particles. The CMB model shows the latter to arise mainly from road traffic sources, with smaller contributions from vegetative detritus, wood smoke, natural gas, coal, and dust/soil. The CMB model also identifies an important component of the organic aerosol not associated with these primary sources, which correlates very strongly with secondary organic aerosol estimated from the OC/EC ratio. The split between different automotive source types does not relate well to UK emission inventories, and may indicate that CMB source profiles from North American studies and different carbon analysis protocols may lead to erroneous conclusions. © 2009 Elsevier Ltd. All rights reserved.

Zhao Y.,Lanzhou University | Yu Z.,Lehigh University | Zhao W.,Lanzhou University
Quaternary Science Reviews | Year: 2011

The climates on the eastern Tibetan Plateau are strongly influenced by direct insolation heating as well as monsoon-derived precipitation change. However, the moisture and temperature influences on regional vegetation and climate have not been well documented in paleoclimate studies. Here we present a well-dated and high-resolution loss-on-ignition, peat property and fossil pollen record over the last 10,000 years from a sedge-dominated fen peatland in the central Zoige Basin on the eastern Tibetan Plateau and discuss its ecological and climatic interpretations. Lithology results indicate that organic matter content is high at 60-80% between 10 and 3ka (1ka=1000calyrBP) and shows large-magnitude fluctuations in the last 3000 years. Ash-free bulk density, as a proxy of peat decomposition and peatland surface moisture conditions, oscillates around a mean value of 0.1g/cm3, with low values at 6.5-4.7ka, reflecting a wet interval, and an increasing trend from 4.7 to 2ka, suggesting a drying trend. The time-averaged mean carbon accumulation rates are 30.6gC/m2/yr for the last 10,000 years, higher than that from many northern peatlands. Tree pollen (mainly from Picea), mostly reflecting temperature change in this alpine meadow-forest ecotonal region, has variable values (from 3 to 34%) during the early Holocene, reaches the peak value during the mid-Holocene at 6.5ka, and then decreases until 2ka. The combined peat property and pollen data indicate that a warm and wet climate prevailed in the mid-Holocene (6.5-4.7ka), representing a monsoon maximum or " optimum climate" for the region. The timing is consistent with recent paleo-monsoon records from southern China and with the idea that the interplays of summer insolation and other extratropical large-scale boundary conditions, including sea-surface temperature and sea-level change, control regional climate. The cooling and drying trend since the mid-Holocene likely reflects the decrease in insolation heating and weakening of summer monsoons. Regional synthesis of five pollen records along a south-north transect indicates that this climate pattern can be recognized all across the eastern Tibetan Plateau. The peatland and vegetation changes in the late Holocene suggest complex and dramatic responses of these lowland and upland ecosystems to changes in temperature and moisture conditions and human activities. © 2011 Elsevier Ltd.

Wang X.,Japan International Center for Materials Nanoarchitectonics | Tian W.,Japan International Center for Materials Nanoarchitectonics | Liu D.,Japan International Center for Materials Nanoarchitectonics | Liu D.,Lanzhou University | And 3 more authors.
Nano Energy | Year: 2013

Nowadays, 2D nanosheets or nanoplatelets have attracted great attention due to their wide applications. However, the synthesis of 2D α-Fe2O3 nanosheets with well-defined hexagonal shape is extremely challenging, because the selective growth along one specific facet is very hard to be realized. In our work, we studied the non-capping ligand mediated reaction within graphene layer chamber, and successfully synthesized α-Fe2O3 hexagonal nanoplatelets sandwiched between graphene layers (HP-Fe-G). These materials exhibit an improved electrochemical performance compared with the pre-existing α-Fe2O3 nanoparticles loaded graphene (G-Fe2O3) composites because of the uniqueness of such architectures: thin nanoplatelets, large enough sandwiched spaces to buffer the volume expansion and N-doped graphene. HP-Fe-G delivered an ultrahigh reversible capacity of 1100mAh/g after 50 cycles, thus higher than their theoretical value (926mAh/g); while G-Fe2O3 composites showed relatively low capacity retention even after only 20 cycles (582mAh/g). In addition, HP-Fe-G also reveal superior rate capability, 887mAh/g at 1C; in comparison, this value was only 135mAh/g at 1C for G-Fe2O3. © 2012 Elsevier Ltd.

Liu J.,Harbin Institute of Technology | Zhou X.,Lanzhou University
Journal of Constructional Steel Research | Year: 2010

This paper presents an experimental and analytical study on the behavior of axially compressed tubed RC stub columns. Forty specimens including twenty circular tubed RC (STRC) and twenty square tubed RC (STRC) stub columns were tested to investigate the failure mode and axial load strength of tubed RC columns subjected to axial compression. The effect of diameter/width to thickness ratio of the tubes and compressive strength of concrete were also studied. The effect of height to diameter/width ratio of the separated tube in tubed RC columns was studied to investigate the effect of bond and friction between tube and concrete on the behavior of tubed RC columns. Elastic-plastic analysis on the steel tube was employed to study the mechanism of tubed RC stub columns subjected to axial compression. Equations for the prediction of the ultimate axial load strength of tubed RC stub columns were proposed and the results from prediction were compared with the test results. © 2009 Elsevier Ltd. All rights reserved.

Zhou X.,Lanzhou University | Liu J.,Harbin Institute of Technology
Journal of Constructional Steel Research | Year: 2010

Reinforced concrete (RC) short columns are vulnerable to brittle shear failure during an earthquake. The objective of this research is to evaluate the performance enhancement of RC short columns tubed with circular or square tubes. Eight short columns were tested under combined constant axial load and cyclic lateral load. The tested specimens included three circular tubed RC (CTRC) columns and three square tubed RC (STRC) columns. Two common RC short columns including one circular RC column and one square RC column were also tested as control specimens. The test results indicated that common RC short columns suffered brittle shear failure with little ductility, while the ductility of tubed RC short columns was excellent due to the effective confinement of the outer thin tube to the core concrete. The lateral load strength of CTRC short columns increases with the increasing of axial load ratio, while the axial load ratio has little effect on the plastic deformation capacity of CTRC short columns. The shear strength increases with increasing of axial load ratio, while the plastic deformation capacity decreases with increasing of axial load ratio for STRC short columns. A circular tube prevents the core concrete from shear failure more effectively than a square tube for the tubed RC short columns. A modified ACI design method is adopted to calculate the nominal shear strength of STRC columns as well as CTRC columns based on the test and analysis results. © 2009 Elsevier Ltd. All rights reserved.

Zhou X.,Lanzhou University | Liu J.,Harbin Institute of Technology
Journal of Constructional Steel Research | Year: 2010

The seismic behavior of tubed SRC short columns has been investigated by testing eight specimens subjected to combined constant axial compression and lateral cyclic load. Three circular tubed SRC columns (CTSRC) and three square tubed SRC (STSRC) columns were tested in this research with two common SRC columns for comparison. Different axial load ratios (n0 = 0.3, 0.4 and 0.5) have been adopted for the constant axial load. The test results indicate that the shear strength, plastic deformation capacity, ductility index, and energy dissipating capacity of the tubed SRC short columns were much higher than those of the SRC columns with the same steel ratio and axial compressive load. The lateral load strength of CTSRC and STSRC short columns increased with an increment in axial load level, while the axial load ratio has no obvious effect on the plastic deformation capacity of CTSRC and STSRC short columns. The steel tubes prevented the shear failure of the concrete more effectively in the circular columns than in the square ones. Shear connector studs should be used in CTSRC and STSRC short columns to prevent bond failure between concrete and flanges of the steel section. A modified ACI design method was adopted to calculate the nominal shear strength of STSRC columns as well as CTSRC columns. © 2010 Elsevier Ltd. All rights reserved.

Gao Q.,Central China Normal University | Zhang J.,Central China Normal University | Wu X.,Central China Normal University | Liu S.,Central China Normal University | And 2 more authors.
Organic Letters | Year: 2015

The first C3-dicarbonylation of indoles was realized through direct oxidative cross-coupling of indoles with methyl ketones in the presence of molecular iodine and pyrrolidine. This reaction constructed a highly efficient indolyl diketones scaffold, which might be regarded as a useful biological and pharmacological tool in the exploration of therapeutic A2BAR modulators. The use of inexpensive molecular iodine and pyrrolidine and a broad substrate scope make this protocol very practical. Preliminary mechanistic studies indicate that two paths are involved in this process. (Chemical Presented). © 2014 American Chemical Society.

Sun H.,Harbin Institute of Technology | Yang C.,Harbin Institute of Technology | Lin R.,Harbin Institute of Technology | Xia W.,Harbin Institute of Technology | Xia W.,Lanzhou University
Advanced Synthesis and Catalysis | Year: 2014

A mild and efficient procedure was developed for the regioselective ring-opening nucleophilic addition reactions of aziridines via visible light photoredox catalysis, that provides a practical synthetic access to 1,2-bifunctional compounds. Furthermore, the regioselective synthesis of non-racemic amino ethers from chiral aziridine could also be achieved under mild conditions. Finally, a possible reaction mechanism was proposed and further supported by control experiments. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA.

Opitz S.,University of Cologne | Zhang C.,Lanzhou University | Herzschuh U.,Alfred Wegener Institute for Polar and Marine Research | Mischke S.,University of Iceland
Quaternary Science Reviews | Year: 2015

A multi-proxy Lateglacial environmental record is described from Lake Naleng (31.10°N; 99.75°E, 4200m above sea level), situated on south-eastern Tibetan Plateau to gain deeper insights into the hydrological and palaeoclimate development since 17.7calka BP. Palynological reconstructions of variations in mean annual precipitation (MAP) and temperature (MAT), sedimentological data and sediment chemistry including weathering indicators provide a multi-faceted picture of local and regional environmental changes since the Lateglacial. Principal component analyses of all parameters provide information on interrelationships between each parameters, which help to evaluate their traceability to temperature and precipitation and to estimate their usability as proxy indicators for local and or regional variations. During the Lateglacial from 17.7 to 14.0calka BP Lake Naleng experienced cold and dry climate conditions with low biological productivity and supply of unaltered fine-grained material due to the high supply of glacier milk. During the second half of the Lateglacial, climate conditions changed abruptly: increases in MAT (from-4 to-2.2°C) and MAP (from 500mm to 820mm) between 14.0 and 13.0calka BP indicate a climate amelioration. This time interval can be correlated to the Bølling/Allerød (B/A) warming period in the North Atlantic region and is followed by the Younger Dryas cold reversal indicated by abrupt decreases of MAT (from-2.2 to-5°C) and MAP (from 820 to 650mm). The onset of the Holocene at about 11.5calka BP is indicated by rises in reconstructed MAT (from-5 to about-0.3°C) and MAP (from 600mm to 950mm), which led to an increased supply of weathered material and higher biological productivity. Between 5.0 and 3.0calka BP, MAT increases to about 0.2°C and MAP rises to maximum values of about 1000mm, followed by slightly decreasing MAT and MAP between 3.0 and 0calka BP.The biogeochemical parameters (total organic carbon (TOC), C/N, δ13Corg) and weathering indicators (e.g. the chemical index of alteration (CIA) and Sr/Ba) are directly (erosion of soils) or indirectly (changing provenance) related to moisture availability on the south-eastern TP and shows matching regional climate oscillations since the Lateglacial. In comparison to other Lateglacial records from the TP, MAP reconstructions from Lake Naleng indicate wetter climate conditions in the south-eastern part of the TP and dryer conditions farther away from moisture sources. © 2015 Elsevier Ltd.

Liu G.,Central China Normal University | Song D.,Central China Normal University | Chen F.,Lanzhou University
Talanta | Year: 2013

A label-free immunosensor based on SWNTs modified GC electrodes has been developed for the direct detection of paraoxon. Based on aryldiazonium salt chemistry, forest of SWNTs can be vertically aligned on mixed monolayers of aryldiazonium salt modified GC electrodes by CC bonding, which provides an interface showing efficient electron transfer between biomolecules. PEG molecules were introduced to the interface to resist non-specific protein adsorption. Ferrocenedimethylamine (FDMA) was subsequently attached to the ends of SWNTs through the amide bonding followed by the attachment of epitope i.e., paraoxon hapten to which a paraoxon antibody would bind. This immunosensor shows good selectivity and high specificity to paraoxon, and is functional for the detection of paraoxon in both laboratory and field by a displacement assay. There is a linear relationship between electrochemical signal of FDMA and the concentration of paraoxon over the range of 2-2500 ppb with a lowest detected limit of 2 ppb in 0.1 M phosphate buffer at pH 7.0. The SWNTs based amperometric immunosensor provides an opportunity to develop the sensing system for on-site sensitive detection of a spectrum of insecticides. © 2012 Elsevier B.V.

Zhang H.,University of the Humanities | Shaheen S.A.,University of California at Berkeley | Chen X.,Lanzhou University
International Journal of Sustainable Transportation | Year: 2014

This article examines four phases in bicycle evolution in China from initial entry and slow growth (1900s to 1978), to rapid growth (1978 to 1995), bicycle use reduction (1995 to 2002), and policy diversification (2002 to present). Two bicycle innovations, electric bikes, and public bikesharing (the shared use of a bicycle fleet), are also explored in this article. Electric bikes could provide a transitional mode on the pathway to bicycle and public transportation integration or to small battery electric cars. Four lessons have been learned from China's electric bike experience relevant to government policy and management. Public bikesharing represents an important step towards integrating the bicycle with bus, metro, and rail systems. Five early operational lessons have been identified from China's limited public bikesharing experience. © 2014 Copyright Taylor and Francis Group, LLC.

Li C.,Xi'an University of Science and Technology | Deng W.-H.,Lanzhou University
Communications in Theoretical Physics | Year: 2014

Following the fractional cable equation established in the letter [B.I. Henry, T.A.M. Langlands, and S.L. Wearne, Phys. Rev. Lett. 100 (2008) 128103], we present the time-space fractional cable equation which describes the anomalous transport of electrodiffusion in nerve cells. The derivation is based on the generalized fractional Ohm's law; and the temporal memory effects and spatial-nonlocality are involved in the time-space fractional model. With the help of integral transform method we derive the analytical solutions expressed by the Green's function; the corresponding fractional moments are calculated; and their asymptotic behaviors are discussed. In addition, the explicit solutions of the considered model with two different external current injections are also presented. © 2014 Chinese Physical Society and IOP Publishing Ltd.

Zhao Y.,Lanzhou University | Yu Z.,Lehigh University
Earth-Science Reviews | Year: 2012

Fossil pollen records from 20 sites with reliable chronologies and high-resolution data in the East Asian monsoon margin region were synthesized to document Holocene vegetation and climate change and to understand the large-scale controls. The vegetation experienced different changes over the Holocene in various sub-regions. (1) Near the boundary between modern forest and temperate steppe in Northeast China, forest showed clear expansion in the middle Holocene. (2) In central China near the boundary between steppe/forest and desert, vegetation showed various patterns at different sites. (3) Further west on the Tibetan Plateau near the boundary between highland meadow/steppe and semi-desert/desert, forest expanded at most sites during the early and middle Holocene. Our synthesis indicates that climate in the margin region was slightly moist in the early Holocene, wettest in the middle Holocene, and dry in the late Holocene, though there are regional differences as reflected by vegetation change. This general pattern is very different from either monsoon- or westerly-dominated regions. The maximum moisture occurred during the early Holocene in the monsoon region, while the arid central Asia dominated by the westerlies was driest in the early Holocene and wettest in the mid-Holocene. The interplay of the Asian summer monsoon, westerlies, topography and regional vegetation factors might have contributed to this spatial complexity. © 2012 Elsevier B.V..

Liu D.,Japan International Center for Materials Nanoarchitectonics | Liu D.,Lanzhou University | Wang X.,Japan International Center for Materials Nanoarchitectonics | Tian W.,Japan International Center for Materials Nanoarchitectonics | And 2 more authors.
Scientific Reports | Year: 2013

Functional materials with both exposed highly reactive planes and hollow structures have attracted considerable attentions with respect to improved catalytic activity and enhanced electrochemical energy storage. Herein, we report the synthesis of unusual single-crystal Co3 O4 nanocages with highly exposed {110} reactive facets via a one-step solution method. When tested as anode materials in lithium-ion batteries, these Co 3 O4 nanocages deliver a high reversible lithium storage capacity of 864 mAh g-1 at 0.2C over 50 cycles and exhibit an excellent rate capability. The dominantly exposed {110} planes, a high density of atomic steps in nanocages, and the large void interiors lead to the regarded superior electrochemical performance.

Deng Q.-H.,Central China Normal University | Chen J.-R.,Central China Normal University | Wei Q.,Central China Normal University | Zhao Q.-Q.,Central China Normal University | And 3 more authors.
Chemical Communications | Year: 2015

A visible-light-induced photocatalytic oxytrifluoromethylation reaction of N-allylamides has been developed for the efficient synthesis of CF3-containing oxazolines and benzoxazines under mild reaction conditions. This journal is © 2015 The Royal Society of Chemistry.

Wang Y.,Harbin Institute of Technology | Yang Y.,Lanzhou University | Zhang S.,Harbin Institute of Technology
Thin-Walled Structures | Year: 2012

Square concrete-filled steel tubes (CFSTs) are gaining increasing usage in modern construction practice, offering improved mechanical properties and increased material efficiency compared with the individual steel and core concrete components. However, the cross-section slenderness of the encasing steel is, although more inflexible than a comparable hollow steel tube, restrained due to local buckling. A number of innovative kinds of reinforcement stiffeners have been put forward particularly for the square CFSTs with slender sections of encasing steel. To investigate the mechanical effect of the reinforcement stiffeners and compare them with traditional ones in practice, four square CFSTs welded with various reinforcement stiffeners and one reference CFST have been tested, and are presented in this paper. The mechanical behaviors such as the resistance, ductility and failure modes investigated during the test were also studied in the theoretical research, which was carried out to predict and further summarize the comprehensive properties of the specimens. A numerical analysis program was written and verified with related scholars' experimental data, and extensive parametric analysis was conducted to investigate the influencing parameters on mechanical properties. Design recommendation for the cross-section strength has been put forward based on the test results and previous research. © 2012 Elsevier Ltd. All rights reserved.

Lin X.,Jimei University | Xu S.-J.,Lanzhou University | Yeh Y.-N.,Academia Sinica, Taiwan
Match | Year: 2013

The Hosoya polynomial (also called Wiener polynomial) of a graph G with the vertex set V (G) is defined as H(G, x) = Σ {u,v}⊆V (G)xdG(u,v) on variable x, where the sum is over all unordered pairs {u, v} of distinct vertices in G, dG(u, v) is the distance of two vertices u, v in G. In 2004, Yang and Yeh evaluated H(G, x) for certain graphs of chemical interest, and posted an open problem for evaluating the Hosoya polynomial of the circumcoronene Cr of order r. In this paper, we solve this problem and give analytical expressions associated with r. The topological indices-Wiener index and hyper-Wiener index of C r can also be obtained from H(Cr, x) through this work.

Sun H.,Harbin Institute of Technology | Yang C.,Harbin Institute of Technology | Gao F.,Harbin Institute of Technology | Li Z.,Harbin Institute of Technology | And 2 more authors.
Organic Letters | Year: 2013

The visible-light mediated oxidative C-C bond cleavage of aldehydes has been achieved in good yields at ambient temperature and open to air using Ru(bpy)3Cl2 (bpy = 2,2′-bipyridine) as the photoredox catalyst. Moreover, we further demonstrated the application in a tandem Michael/oxidative C-C bond cleavage reaction. © 2013 American Chemical Society.

Zhao C.,Lehigh University | Yu Z.,Lehigh University | Ito E.,University of Minnesota | Zhao Y.,Lanzhou University
Quaternary Science Reviews | Year: 2010

Earlier studies indicated that the general pattern of the Holocene climate in the northeastern United States changed from cool and dry (11.6-8.2ka; 1ka=1000 cal yr BP) to warm and wet (8.2-5.4ka) to warm and dry (5.4-3ka) to cool and wet (after 3ka). A new ∼35-year resolution stable isotope record of endogenic calcite from a sediment core for Lake Grinnell in northern New Jersey provided a chance to examine the Holocene climate variations of the region in a finer detail. After the Younger Dryas cold climate reversal, the δ18O fluctuated around a constant value of -7.4‰ until 5.8ka, thereafter shifted to a steadily decreasing trend to the most recent value of -8.2‰ Responding to this shift, the widely observed hemlock decline in the northeastern USA occurred about ∼350-500 (±143.5) years later. Detrended δ18O and δ13C records show a clear covariance at 910-year periodicity. The amplitudes of centennial-scale δ18O variations became much smaller after 4.7ka. At the same time, the dominant frequency of these variations changed from 330 to 500 years. We suggest that a non-linear response of atmospheric circulation to the gradual decrease in insolation is responsible for the shift in the climate trend at 5.8ka as indicated by the deceasing δ18O values. A dominant frequency shift in solar forcing and the decreased seasonal contrast of insolation might have caused the change in climate variability at 4.7ka through modulating ocean and atmosphere circulations. © 2010 Elsevier Ltd.

Liu Y.,Lanzhou University | Peng X.-P.,Lanzhou University | Lou X.,Xi'an University of Science and Technology | Zhou H.,Lanzhou University
Applied Physics Letters | Year: 2012

Electrocaloric effect in ultrathin SrRuO 3/BaTiO 3/SrRuO 3 capacitors is calculated using a multiscale thermodynamic model. It is found that the electrocaloric coefficient vs working temperature is shifted to higher temperatures with increasing the BaTiO 3 layer thickness (above the critical thickness). The electrocaloric effect above the critical thickness is much stronger than that below it. Furthermore, it is demonstrated that a giant electrocaloric effect (3.5 K under 0.24 V) in such capacitors (six BaTiO 3 unit cells) at 300 K can be achieved, which suggests that ultrathin ferroelectric capacitors may be promising candidates for room temperature solid-state refrigeration. © 2012 American Institute of Physics.

Mao J.,Anhui Science and Technology University | Mao J.,Lanzhou University | He Q.,Lanzhou University | Liu W.,Lanzhou University
Talanta | Year: 2010

An "off-on" rhodamine-based fluorescence probe for the selective signaling of Fe(III) has been designed exploiting the guest-induced structure transform mechanism. This system shows a sharp Fe(III)-selective fluorescence enhancement response in 100% aqueous system under physiological pH value and possesses high selectivity against the background of environmentally and biologically relevant metal ions including Al(III), Cd(II), Fe(II), Co(II), Cu(II), Ni(II), Zn(II), Mg(II), Ba(II), Pb(II), Na(I), and K(I). Under optimum conditions, the fluorescence intensity enhancement of this system is linearly proportional to Fe(III) concentration from 6.0 × 10-8 to 7.2 × 10-6 mol L-1 with a detection limit of 1.4 × 10-8 mol L-1. © 2009 Elsevier B.V. All rights reserved.

Huang Y.,Lanzhou University | Ng M.,Hong Kong Baptist University | Zeng T.,Hong Kong Baptist University
Communications in Computational Physics | Year: 2013

In this paper, we consider variational approaches to handle the multiplicative noise removal and deblurring problem. Based on rather reasonable physical blurring-noisy assumptions, we derive a new variational model for this issue. After the study of the basic properties, we propose to approximate it by a convex relaxation model which is a balance between the previous non-convex model and a convex model. The relaxed model is solved by an alternating minimization approach. Numerical examples are presentedto illustrate the effectivenessand efficiencyof the proposed method. © 2013 Global-Science Press.

Zhao X.-L.,University of Electronic Science and Technology of China | Wang F.,Lanzhou University | Huang T.-Z.,University of Electronic Science and Technology of China | Ng M.K.,Hong Kong Baptist University | Plemmons R.J.,Wake forest University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

The main aim of this paper is to study total variation (TV) regularization in deblurring and sparse unmixing of hyperspectral images. In the model, we also incorporate blurring operators for dealing with blurring effects, particularly blurring operators for hyperspectral imaging whose point spread functions are generally system dependent and formed from axial optical aberrations in the acquisition system. An alternating direction method is developed to solve the resulting optimization problem efficiently. According to the structure of the TV regularization and sparse unmixing in the model, the convergence of the alternating direction method can be guaranteed. Experimental results are reported to demonstrate the effectiveness of the TV and sparsity model and the efficiency of the proposed numerical scheme, and the method is compared to the recent Sparse Unmixing via variable Splitting Augmented Lagrangian and TV method by Iordache © 1980-2012 IEEE.

Lee S.,Umeå University | Holme P.,Umeå University | Holme P.,Sungkyunkwan University | Wu Z.-X.,Umeå University | Wu Z.-X.,Lanzhou University
Physical Review Letters | Year: 2011

We investigate a game-theoretic model of a social system where both the rules of the game and the interaction structure are shaped by the behavior of the agents. We call this type of model, with several types of feedback couplings from the behavior of the agents to their environment, a multiadaptive game. Our model has a complex behavior with several regimes of different dynamic behavior accompanied by different network topological properties. Some of these regimes are characterized by heterogeneous, hierarchical interaction networks, where cooperation and network topology coemerge from the dynamics. © 2011 American Physical Society.

Pieper D.,Witten/Herdecke University | Buechter R.B.,Institute for Quality and Efficiency in Health Care IQWiG | Li L.,Lanzhou University | Prediger B.,Witten/Herdecke University | Eikermann M.,Witten/Herdecke University
Journal of Clinical Epidemiology | Year: 2015

Objectives To summarize all available evidence on measurement properties in terms of reliability, validity, and feasibility of the Assessment of Multiple Systematic Reviews (AMSTAR) tool, including R(evised)-AMSTAR. Study Design and Setting MEDLINE, EMBASE, Psycinfo, and CINAHL were searched for studies containing information on measurement properties of the tools in October 2013. We extracted data on study characteristics and measurement properties. These data were analyzed following measurement criteria. Results We included 13 studies, four of them were labeled as validation studies. Nine articles dealt with AMSTAR, two articles dealt with R-AMSTAR, and one article dealt with both instruments. In terms of interrater reliability, most items showed a substantial agreement (>0.6). The median intraclass correlation coefficient (ICC) for the overall score of AMSTAR was 0.83 (range 0.60-0.98), indicating a high agreement. In terms of validity, ICCs were very high with all but one ICC lower than 0.8 when the AMSTAR score was compared with scores from other tools. Scoring AMSTAR takes between 10 and 20 minutes. Conclusion AMSTAR seems to be reliable and valid. Further investigations for systematic reviews of other study designs than randomized controlled trials are needed. R-AMSTAR should be further investigated as evidence for its use is limited and its measurement properties have not been studied sufficiently. In general, test-retest reliability should be investigated in future studies. © 2015 Elsevier Inc. All rights reserved.

Huang Y.-M.,Lanzhou University | Moisan L.,University of Paris Descartes | Ng M.K.,Hong Kong Baptist University | Zeng T.,Hong Kong Baptist University
IEEE Transactions on Image Processing | Year: 2012

Multiplicative noise removal is a challenging image processing problem, and most existing methods are based on the maximum a posteriori formulation and the logarithmic transformation of multiplicative denoising problems into additive denoising problems. Sparse representations of images have shown to be efficient approaches for image recovery. Following this idea, in this paper, we propose to learn a dictionary from the logarithmic transformed image, and then to use it in a variational model built for noise removal. Extensive experimental results suggest that in terms of visual quality, peak signal-to-noise ratio, and mean absolute deviation error, the proposed algorithm outperforms state-of-the-art methods. © 2012 IEEE.

Cheng H.-Y.,Academia Sinica, Taiwan | Yu F.-S.,Lanzhou University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The empirical observation of near degeneracy of scalar mesons above 1 GeV, namely, the mass of the strange-flavor scalar meson is similar to that of the nonstrange one, is at variance with the naive expectation of the quark model. Qualitatively, the approximate mass degeneracy can be understood as a consequence of self-energy effects due to strong coupled channels which will push down the mass of the heavy scalar meson in the strange sector more than that in the nonstrange partner. However, it works in the conventional model without heavy quark expansion, but not in the approach of heavy meson chiral perturbation theory as mass degeneracy and the physical masses of Ds0* and D0* cannot be accounted for simultaneously. In the heavy quark limit, near mass degeneracy observed in the scalar charm sector will imply the same phenomenon in the B system. We have the prediction MB0*≈MBs0*≈ 5715MeV+δΔS based on heavy quark symmetry and the leading-order QCD correction, where δΔS arises from 1/mQ corrections. A crude estimate indicates that δΔS is of order -35MeV or less. We stress that the closeness of Bs0* and B0* masses implied by heavy quark symmetry is not spoiled by 1/mQ or QCD corrections. The mass-shift effect on K0*(1430) is discussed. © 2014 American Physical Society.

Yang F.L.,Lanzhou University | Ling L.,Hong Kong Baptist University
Engineering Analysis with Boundary Elements | Year: 2011

Over the last decade, there has been a considerable amount of new numerical methods being developed for solving the Cauchy problems of elliptic operators. In this paper, with some new classes of numerical experiments, we re-verify the conclusions in the review article [Wei T, Hon YC, Ling L. Method of fundamental solutions with regularization techniques for Cauchy problems of elliptic operators. Eng Anal Bound Elem 2007;31(4):37385.] concerning the effectiveness of solving Cauchy problems with the method of fundamental solutions. © 2011 Elsevier Ltd.

Jia Z.-X.,Lanzhou University | Luo Y.-C.,Lanzhou University | Wang Y.,Lanzhou University | Chen L.,Lanzhou University | And 2 more authors.
Chemistry - A European Journal | Year: 2012

Cascading like dominos: An efficient and highly enantioselective synthesis of 2,3,4-trisubstituted tetrahydroquinolines through cascade aza-Michael-Michael reactions was developed. Tetrahydroquinolines were obtained in excellent yields, high enantioselectivities, and good diastereoselectivities, and could be easily transformed into ring-fused tetrahydroquinolines (see scheme). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li J.,University of Insubria | Li J.,Lanzhou University | Gramatica P.,University of Insubria
Journal of Chemical Information and Modeling | Year: 2010

Computational tools, such as quantitative structure-activity relationship (QSAR), are highly useful as screening support for prioritization of substances of very high concern (SVHC). From the practical point of view, QSAR models should be effective to pick out more active rather than inactive compounds, expressed as sensitivity in classification works. This research investigates the classification of a big data set of endocrine-disrupting chemicals (EDCs)-androgen receptor (AR) antagonists, mainly aiming to improve the external sensitivity and to screen for potential AR binders. The kNN, lazy IB1, and ADTree methods and the consensus approach were used to build different models, which improve the sensitivity on external chemicals from 57.1% (literature) to 76.4%. Additionally, the models' predictive abilities were further validated on a blind collected data set (sensitivity: 85.7%). Then the proposed classifiers were used: (i) to distinguish a set of AR binders into antagonists and agonists; (ii) to screen a combined estrogen receptor binder database to find out possible chemicals that can bind to both AR and ER; and (iii) to virtually screen our in-house environmental chemical database. The in silico screening results suggest: (i) that some compounds can affect the normal endocrine system through a complex mechanism binding both to ER and AR; (ii) new EDCs, which are nonER binders, but can in silico bind to AR, are recognized; and (iii) about 20% of compounds in a big data set of environmental chemicals are predicted as new AR antagonists. The priority should be given to them to experimentally test the binding activities with AR. © 2010 American Chemical Society.

Wu Z.-X.,Lanzhou University | Holme P.,Umeå University | Holme P.,Sungkyunkwan University | Holme P.,University of Stockholm
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

In a recent work, Schneider proposed a new measure for network robustness and investigated optimal networks with respect to this quantity. For networks with a power-law degree distribution, the optimized networks have an onion structure-high-degree vertices forming a core with radially decreasing degrees and an over-representation of edges within the same radial layer. In this paper we relate the onion structure to graphs with good expander properties (another characterization of robust network) and argue that networks of skewed degree distributions with large spectral gaps (and thus good expander properties) are typically onion structured. Furthermore, we propose a generative algorithm producing synthetic scale-free networks with onion structure, circumventing the optimization procedure of Schneider We validate the robustness of our generated networks against malicious attacks and random removals. © 2011 American Physical Society.

Jin Z.,Institute of Geology | Cunningham D.,University of Leicester | Hongyi C.,Lanzhou University
Journal of Asian Earth Sciences | Year: 2010

Cenozoic sedimentary deposits in central-southern Ningxia province, NW China are an important record of Tertiary tectonic events along the evolving Qinghai-Tibetan Plateau's northeast margin. Shortly after the onset of the Indo-Eurasia collision to the south, a thrust belt and adjoining foreland basin began to form during 40-30. Ma. The Eocene Sikouzi Formation developed in a distal setting to this basin, in normal fault-bound basins that may have formed in a forebulge setting. Subsequent deposition of the Oligocene Qingshuiying Formation occurred during a phase of apparently less intense tectonism and the previous underfilled foreland basin became overfilled. During the Early Miocene, contractional deformation was mainly distributed to the west of the Liupan Shan. This resulted in deformation of the Qingshuiying Formation as indicated by an unconformity with the overlying Miocene Hongliugou Formation. The unconformity occurs proximal to the Haiyuan Fault suggesting that the Haiyuan Fault may have begun movement in the Early Miocene. In the Late Miocene, thrusting occurred west of the southern Helan Shan and an unconformity developed between the Hongliugou and Qingshuiying Formations proximal to the the Cha-Gu Fault. Relationships between the Miocene stratigraphy and major faults in the region imply that during the Late Miocene the deformation front of the Qinghai-Tibetan Plateau had migrated to the Cha-Gu Fault along the western Ordos Margin, and the Xiang Shan was uplifted. Central-southern Ningxia was then incorporated into the northeast propagating thrust wedge. The driving force for NE propagation of the thrust wedge was most likely pronounced uplift of the northeastern plateau at the same time. Analysis of the sedimentary record coupled with consideration of the topographic evolution of the region suggests that the evolving fold-and-thrust belt experienced both forward-breaking fold-and-thrust belt development, and out-of-sequence fault displacements as the thrust wedge evolved and the foreland basin became compartmentalised. The documented sedimentary facies and structural relationship also place constraints on the Miocene-Recent evolution of the Yellow River and its tributaries. © 2010 Elsevier Ltd.

Xie Q.,Lanzhou University | Li J.,Lanzhou University | Tian Q.,China Academy of Engineering Physics | Shi R.,Lanzhou University
Journal of Materials Chemistry | Year: 2012

A novel, facile, green and template-free approach was developed for the fabrication of amorphous zinc citrate yolk-shell microspheres and crystalline ZnO yolk-shell nanospheres. In this approach, the amorphous zinc citrate yolk-shell microspheres were prepared through a single chemical reaction at low temperature (90 °C) and with room temperature ageing. The zinc citrate yolk-shell microspheres have an average size of about 1.25 μm. The average diameter of the inner cores and the average thickness of the outer shells are 500 nm and 150 nm, respectively. The effect of ageing time on the morphology of the zinc citrate microstructures was analysed. As the ageing time increases from 0 to 12 h, the zinc citrate microstructure transforms from a solid microsphere through a yolk-shell microsphere to a hollow microsphere. The ZnO solid nanospheres, yolk-shell nanospheres and hollow nanospheres can be prepared via the perfect morphology inheritance of the zinc citrate solid microspheres, yolk-shell microspheres and hollow microspheres, by calcination at 600 °C for 2 h. The ZnO yolk-shell nanospheres show the largest visible emission and the highest photocatalytic activity. © 2012 The Royal Society of Chemistry.

Ye L.,Wuhan University | Deng K.,South-Central University for Nationalities | Xu F.,Lanzhou University | Tian L.,Wuhan University | And 2 more authors.
Physical Chemistry Chemical Physics | Year: 2012

Black BiOCl with oxygen vacancies was prepared by UV light irradiation with Ar blowing. The as-prepared black BiOCl sample showed 20 times higher visible light photocatalytic activity than white BiOCl for RhB degradation. The trapping experiment showed that the superoxide radical () and holes (h+) were the main active species in aqueous solution under visible light irradiation.

Guo H.,Xidian University | Xie Q.-Y.,Lanzhou University | Fu C.-E.,Xi'an Jiaotong University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Localization of a spin-1/2 fermion on the braneworld is an important and interesting problem. It is well known that a five-dimensional free massless fermion Ψ minimally coupled to gravity cannot be localized on the Randall-Sundrum braneworld. In order to trap such a fermion, the coupling between the fermion and bulk scalar fields should be introduced. In this paper, localization and quasilocalization of a bulk fermion on the thick braneworld generated by two scalar fields (a kink scalar φ and a dilaton scalar π) are investigated. Two types of couplings between the fermion and two scalars are considered. One coupling is the usual Yukawa coupling -ηΨ¯φΨ between the fermion and kink scalar, another one is λΨ¯ΓM∂Mπγ5Ψ between the fermion and dilaton scalar. The left-chiral fermion zero mode can be localized on the brane, and both the left- and right-chiral fermion massive Kaluza-Klein modes may be localized or quasilocalized. Hence the four-dimensional massless left-chiral fermion and massive Dirac fermions, whose lifetime is infinite or finite, can be obtained on the brane. © 2015 American Physical Society.

Chen Z.-S.,Lanzhou University | Duan X.-H.,Xi'an Jiaotong University | Zhou P.-X.,Lanzhou University | Ali S.,Lanzhou University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2012

Take two: α-Diazocarbonyl compounds display a diverse pattern of reactivity upon palladium-catalyzed reaction with esters. Esters bearing an alkynyl group on the carbonyl carbon atom lead to two different C-C bonds at the same carbon atom in a single operation through decarboxylation and migratory insertion, whereas aromatic and benzylic acid derivatives afford aromatic and benzylic esters bearing an O-substituted quaternary carbon center. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bulleri F.,University of Pisa | Xiao S.,Lanzhou University | Maggi E.,University of Pisa | Benedetti-Cecchi L.,University of Pisa
Oikos | Year: 2014

The mechanisms regulating switches in species interactions along gradients of stress are yet to be fully elucidated. In particular, the role of temporal variability in environmental severity or consumer pressure has been not explored either empirically or theoretically. Here, through a spatially explicit model (i.e. a two-dimensional lattice), we show that variations in the temporal variance of environmental stress can be as important as those in the mean intensity in regulating the spatial distribution and coexistence range of species differing in their relative competitive ability and tolerance to stress, as well as the direction and magnitude of their interactions. In addition, our simulations suggest that enhanced temporal fluctuations in environmental stressors can enhance absolute levels of stress perceived by interacting species. This study shows that tests including both the mean and temporal variance of environmental stress will be key to forecast changes in species interactions under different scenarios of climate change. © 2013 The Authors.

Dorji T.,Norwegian University of Life Sciences | Dorji T.,Tibet Agriculture and Animal Husbandry College | Totland o,Norwegian University of Life Sciences | Moe S.R.,Norwegian University of Life Sciences | And 3 more authors.
Global Change Biology | Year: 2013

Global climate change is predicted to have large impacts on the phenology and reproduction of alpine plants, which will have important implications for plant demography and community interactions, trophic dynamics, ecosystem energy balance, and human livelihoods. In this article we report results of a 3-year, fully factorial experimental study exploring how warming, snow addition, and their combination affect reproductive phenology, effort, and success of four alpine plant species belonging to three different life forms in a semiarid, alpine meadow ecosystem on the central Tibetan Plateau. Our results indicate that warming and snow addition change reproductive phenology and success, but responses are not uniform across species. Moreover, traits associated with resource acquisition, such as rooting depth and life history (early vs. late flowering), mediate plant phenology, and reproductive responses to changing climatic conditions. Specifically, we found that warming delayed the reproductive phenology and decreased number of inflorescences of Kobresia pygmaea C. B. Clarke, a shallow-rooted, early-flowering plant, which may be mainly constrained by upper-soil moisture availability. Because K. pygmaea is the dominant species in the alpine meadow ecosystem, these results may have important implications for ecosystem dynamics and for pastoralists and wildlife in the region. © 2012 Blackwell Publishing Ltd.

Zhao Z.-G.,Lanzhou University | Huang S.-Q.,Wuhan University
International Journal of Plant Sciences | Year: 2013

Premise of research. In flowers that are specialized, floral traits often differentiate in association with pollinator shifts. However, in species of generalized pollination, the role of pollinators in local population differentiation of floral traits is difficult to test. A crucial line of evidence is to contrast the direction and strength of pollinator selection among populations. Methodology. Variation in floral traits and pollinator assemblages was investigated in two populations of a generalist-pollinated herb, Trollius ranunculoides (Ranunculaceae), to detect the potential role of pollinators in floral differentiation. Pivotal results. The alpine population was visited more by flies, and the subalpine population was visited more by bees. Flower manipulations suggested that large flowers were more attractive to both bees and flies, while more petals were favored only by nectar-feeding flies. Compared to the subalpine population, plants in the alpine population had more petals per flower but smaller flowers where flies were predominant pollinators. Flower differences appeared to be genetically maintained in a common garden. Phenotypic selection analysis indicated stronger selection on petal number in the alpine population and oppositely more intense selection on flower diameter in the subalpine population, in accordance with the preferences of local pollinator assemblages. Conclusions. Heritability in floral traits, differences in local pollinator assemblages, and corresponding differences in phenotypic selection are together consistent with the view of pollinator-mediated selection on floral differentiation in T. ranunculoides. © 2013 by The University of Chicago. All rights reserved.

Liao Z.-C.,Lanzhou University | Yang Z.-Y.,Lanzhou University | Li Y.,Wuhan University | Wang B.-D.,Lanzhou University | Zhou Q.-X.,Lanzhou University
Dyes and Pigments | Year: 2013

A highly selective and sensitive fluorescent turn-on chemosensor methyl pyrazinylketone benzoyl hydrazone (MPBH) was synthesized by a facile one-step Schiff base reaction. MPBH which owns a quite simple structure showed a high selectivity for Al3+ over other metal ions in ethanol. Due to the formation of a 1:1 complex between MPBH and the aluminum ions, a significant fluorescence enhancement with a turn-on ratio over 800-fold was achieved. The detection limit of MPBH for Al3+ reached at 10-7 M level. © 2012 Elsevier Ltd. All rights reserved.

Xiao S.,Lanzhou University | Zobel M.,University of Tartu | Szava-Kovats R.,University of Tartu | Partel M.,University of Tartu
Global Ecology and Biogeography | Year: 2010

Aim The diversity-productivity relationship is a controversial issue in ecology. Diversity is sometimes seen to increase with productivity but a unimodal relationship has often been reported. Competitive exclusion was cited initially to account for the decrease of diversity at high productivity. Subsequently, the roles of evolutionary history (species pool size) and dispersal rate have been acknowledged.We explore how the effects of species pool, dispersal and competition combine to produce different diversity-productivity relationships. Methods We use a series of simulations with a spatially explicit, individual-based model. Following empirical expectations, we used four scenarios to characterize species pool size along the productivity gradient (uniformly low and high, linear increase and unimodal). Similarly, the dispersal rate varied along the productivity gradient (uniformly low and high, and unimodal). We considered both neutral communities and communities with competitive exclusion. Results and main conclusions Our model predicts that competitive interactions will result in unimodal diversity-productivity relationships. The model often predicts unimodal patterns in neutral communities as well, although the decline in richness at high productivity is less than in competing communities. A positive diversity-productivity relationship is simulated for neutral communities when the species pool size increases with productivity and the dispersal rate is high. This scenario is probably more widespread in nature than the others since positive diversity-productivity relationships have been observed more frequently than previously expected, especially in the tropics and for woody species. Our simulated effects of species pool, dispersal and competition on diversity patterns can be linked to empirical observations to uncover mechanisms behind the diversity-productivity relationship. © 2010 Blackwell Publishing Ltd.

Zhao C.,Lanzhou University | Zhao C.,China Academy of Engineering Physics | Guan X.,Lanzhou University | Liu X.,Lanzhou University | Zhang H.,Lanzhou University
Journal of Chromatography A | Year: 2012

A molecularly imprinted polymer was synthesized by ultrasonic irradiation, with attapulgite as matrix using β-naphthol as the template molecule, acryloyl-β-cyclodextrin as the functional monomer, and N,N-methylenebiacrylamide as the cross-linking agent, respectively. The imprinted polymer was characterized by infrared spectroscopy and transmission electron microscopy. Compared to polymers prepared by traditional heat sources, the molecularly imprinted polymer synthesized by ultrasonic irradiation had better selectivity and faster adsorption kinetics to estriol, estradiol, estrone and diethylstilbestrol. Using the imprinted polymer as the packing material for on-line solid-phase extraction, the above four estrogens in milk samples were concentrated and analyzed. The limits of detection for these estrogens were in the range of 1-8ngg -1 and reproducibility were less than 5.1% as RSDs (n=6) with milk samples spiked at 100 and 1000ngg -1 of each analyte. © 2012.

Qiao J.,Lanzhou University | Qiao J.,Clausthal University of Technology | Adams J.,Clausthal University of Technology | Johannsmann D.,Clausthal University of Technology
Langmuir | Year: 2012

Investigating the process of film drying from aqueous dispersions containing a polymer latex as well as halloysite nanotubes (HNTs), we found that composite films could be formed without cracking under conditions where films of the pure polymer would always crack. Scanning electron micrographs showed that the HNTs were well dispersed and, further, that the distribution of fiber orientations was close to isotropic. The pendulum hardness of films formed from acrylate dispersions strongly increased upon addition of the inorganic phase. The pencil hardness, on the other hand, was poor, which presumably goes back to insufficient coupling between the organic and the inorganic phase. All films were white in appearance. For fiber concentrations higher than 10 vol %, the final films were porous. © 2012 American Chemical Society.

Wei S.-W.,Lanzhou University | Liu Y.-X.,Lanzhou University | Fu C.-E.,Xi'an Jiaotong University
Advances in High Energy Physics | Year: 2015

The null geodesics and gravitational lensing in a nonsingular spacetime are investigated. According to the nature of the null geodesics, the spacetime is divided into several cases. In the weak deflection limit, we find the influence of the nonsingularity parameter q on the positions and magnifications of the images is negligible. In the strong deflection limit, the coefficients and observables for the gravitational lensing in a nonsingular black hole background and a weakly nonsingular spacetime are obtained. Comparing these results, we find that, in a weakly nonsingular spacetime, the relativistic images have smaller angular position and relative magnification but larger angular separation than those of a nonsingular black hole. These results might offer a way to probe the spacetime nonsingularity parameter and put a bound on it by the astronomical instruments in the near future. © 2015 Shao-Wen Wei et al.

Fu Q.,University of Washington | Fu Q.,Lanzhou University | Manabe S.,Princeton University | Johanson C.M.,University of Washington
Geophysical Research Letters | Year: 2011

IPCC (Intergovernmental Panel on Climate Change) AR4 (Fourth Assessment Report) GCMs (General Circulation Models) predict a tropical tropospheric warming that increases with height, reaches its maximum at ∼200 hPa, and decreases to zero near the tropical tropopause. This study examines the GCM-predicted maximum warming in the tropical upper troposphere using satellite MSU (microwave sounding unit)-derived deep-layer temperatures in the tropical upper-and lower-middle troposphere for 1979-2010. While satellite MSU/AMSU observations generally support GCM results with tropical deep-layer tropospheric warming faster than surface, it is evident that the AR4 GCMs exaggerate the increase in static stability between tropical middle and upper troposphere during the last three decades. Copyright 2011 by the American Geophysical Union.

Wei J.,Xi'an Jiaotong University | Xue D.,Lanzhou University
Applied Surface Science | Year: 2011

In this paper, we show that the leakage current properties of BiFeO 3 (BFO) thin films have been greatly improved by Zr-doping. In contrast, the magnetic properties of Zr-doped BFO films are affected as a weak ferromagnetism. Beyond the double-exchange interactions arising from the creation of Fe2+, we propose another simple model considering the replacement of the magnetically active Fe3+, time to time, by a non-active Zr4+, which is expected to induce a local ferromagnetic coupling rather than an antiferromagnetic one. © 2011 Elsevier B.V. All rights reserved.

Zhou A.-X.,Lanzhou University | Mao L.-L.,Lanzhou University | Wang G.-W.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Chemical Communications | Year: 2014

The first Cu(i)-catalyzed cross-coupling reaction by hydrogen (H 2) removal for the stereoselective synthesis of 3-phosphoindoles is reported. Going beyond the oxidative dehydrogenative coupling reactions reported recently, this reaction completely omits the oxidant and base, producing hydrogen (H2) as the only byproduct. © the Partner Organisations 2014.

Wang B.,Lanzhou University | Hai J.,Lanzhou University | Liu Z.,Lanzhou University | Wang Q.,Lanzhou University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2010

(Figure Presented) Rh-odin's masterpiece: Coupling N-(rhodamine-6G)lactam- ethylenediamine to Fe3O4 nanoparticles through a polyethylene glycol chain renders the rhodamine unit more water soluble and useful for sensitive and selective detection of FeIII at the 2 ppb level in water. This sensitivity is also demonstrated in HeLa cells, thus indicating potential applications of this detection method in biological systems. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lu B.,Lanzhou University | Lu B.,Henan University of Science and Technology | Xu A.,Henan University of Science and Technology | Wang J.,Henan Normal University
Green Chemistry | Year: 2014

As a kind of promising solvents, ionic liquids (ILs) have been used to dissolve cellulose and great progress has been made in recent years. However, the dissolution mechanism, especially the role of cations of ILs in the dissolution of cellulose, is still in debate. In this work, 13 kinds of ILs with a fixed anion [CH3COO]- but varied cationic backbones and alkyl chains have been prepared and characterized. The solubilities of cellulose in these ILs were measured at different temperatures. This allowed us to systematically study the effect of cationic structures on the cellulose dissolution at a given temperature. In order to investigate the dissolution mechanism, Kamlet-Taft parameters of these ILs in the temperature range from 25 to 65 °C and 13C NMR spectra of 1-benzyl-3-methylimidazolium acetate ([phC1mim][CH3COO]) + cellulose systems at 90 °C were also determined. It was found that acidic protons on the heterocyclic rings of the cations are essential for the dissolution of cellulose in the ILs, but the van der Waals interaction of cation with cellulose is not important. These protons may form C-H⋯O hydrogen bonds with hydroxyl and ether oxygen of cellulose to increase cellulose solubility. Cations of the ILs may also decrease cellulose solubility by strong interaction with anions or steric hindrance effect of large size group in their alkyl chains. These interactions together with strong O-H⋯O hydrogen bonds between the anion and hydroxyl protons of cellulose resulted in the disruption of the inter- and intra-molecular hydrogen bonds and thus effective dissolution of cellulose. © 2014 The Royal Society of Chemistry.

Qian B.,CAS Lanzhou Institute of Chemical Physics | Shi D.,CAS Lanzhou Institute of Chemical Physics | Yang L.,CAS Lanzhou Institute of Chemical Physics | Huang H.,CAS Lanzhou Institute of Chemical Physics | Huang H.,Lanzhou University
Advanced Synthesis and Catalysis | Year: 2012

The Lewis acid-catalyzed conjugate addition of 2-alkylazaarenes to methylenemalononitriles through sp 3 C-H bond functionalization has been developed, which provides an efficient and reliable method for incorporation of the nitrile group into the heterocycles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Qin H.-H.,Lanzhou University | Cakoni F.,University of Delaware
Inverse Problems | Year: 2011

In this paper, we consider the inverse scattering problem of recovering the shape of a perfectly conducting cavity from one source and several measurements placed on a curve inside the cavity. Under restrictive assumptions on the size of the cavity, a uniqueness theorem for finitely many excitations is given. Based on a system of nonlinear and ill-posed integral equations for the unknown boundary, we apply a regularized Newton iterative approach to find the boundary. We present the mathematical foundation of the method and give several numerical examples to show the viability of the method. © 2011 IOP Publishing Ltd.

Fan Z.,CAS Lanzhou Institute of Chemical Physics | Liu B.,Lanzhou University | Wang J.,CAS Lanzhou Institute of Chemical Physics | Zhang S.,Lanzhou University | And 4 more authors.
Advanced Functional Materials | Year: 2014

Avoiding wound infection and retaining an appropriate level of moisture around woundz are major challenges in wound care management. Therefore, designing hydrogels with desired antibacterial performance and good water-maintaining ability is of particular significance to promote the development of wound dressing. Thus a series of hydrogels are prepared by crosslinking of Ag/graphene composites with acrylic acid and N,N'-methylene bisacrylamide at different mass ratios. The antibacterial performance and accelerated wound-healing ability of hydrogel are systematically evaluated with the aim of attaining a novel and effective wound dressing. The as-prepared hydrogel with the optimal Ag to graphene mass ratio of 5:1 (Ag5G1) exhibits stronger antibacterial abilities than other hydrogels. Meanwhile, Ag5G1 hydrogel exhibits excellent biocompatibility, high swelling ratio, and good extensibility. More importantly, in vivo experiments indicate that Ag5G1 hydrogel can significantly accelerate the healing rate of artificial wounds in rats, and histological examination reveals that it helps to successfully reconstruct intact and thickened epidermis during 15 day of healing of impaired wounds. In one word, the present approach can shed new light on designing of antibacterial material like Ag/graphene composite hydrogel with promising applications in wound dressing. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zheng Y.,CAS Lanzhou Institute of Chemical Physics | Zheng Y.,Lanzhou University | Wang A.,CAS Lanzhou Institute of Chemical Physics
European Polymer Journal | Year: 2015

Hydrogels are 3D networks of polymer chains that are crosslinked via either physical or chemical bonds. A strong repulsive force is generated among those abundant functional groups with the same charge, which enables the hydrogels to be initially applied as the superabsorbent materials. Recent studies have found that the hydrogel adsorbents show superhigh adsorption capacities, fast adsorption rate, wide pH-independence, easy regeneration and reusable ability, by which the hydrogels are given the appellation "superadsorbent". The limitations of traditional bulk hydrogel make granular hydrogel have received much attention in recent years. Therefore, the purpose of this review is to organize the scattered available information on the focus of polymerization strategies for the formation of granular hydrogels, with the scope limited to the crosslinked hydrogels via polymerization using one or more vinyl monomers. Furthermore, some of the important applications of hydrogel as the superadsorbents for removing various pollutants since 2000 are summarized and discussed, regardless of its form in either bulk or granular. An extensive list of hydrogel adsorbents has been compiled and selected studies with adsorption capacities for heavy metals including radioactive and rare earth metals, dyes and eutrophic substances as available in the literature are presented, with the key advancements of this type of novel adsorbents are briefly addressed. The facile synthesis and energy savings offer them a lot of promising benefits for commercial purposes in the future. © 2015 Elsevier Ltd.

Mu B.,CAS Lanzhou Institute of Chemical Physics | Liu P.,Lanzhou University | Wang A.,CAS Lanzhou Institute of Chemical Physics
Electrochimica Acta | Year: 2013

The polyaniline (PAn)/carbon black (CB) hybrid hollow microspheres have been prepared by the layer-by-layer assembly technique alternately adsorbing of PAn and CB onto the polystyrene sulfonate microsphere templates after etching the templates by dialysis. The hollow structure of the obtained hybrid hollow microspheres was characterized by transmission electron microscopy, which indicated that the external diameter of the hollow microspheres was about 3.0 μm. When the hybrid hollow microsphere were used as the electrode material for supercapacitors, the results showed that the specific capacitance increased with the increase in the adsorption numbers of PAn and CB, which was as high as 532 F g-1 at a charge-discharge current density of 10 mA cm -2 in 1.0 M H2SO4 electrolyte after alternately adsorbing of PAn and CB six times. © 2012 Elsevier Ltd. All rights reserved.

Li Y.-M.,Lanzhou University | Wei X.-H.,Lanzhou University | Li X.-A.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Chemical Communications | Year: 2013

A novel metal-free oxidative carbonitration of alkenes by a nitration and C-H functionalization cascade process has been developed. This methodology provides an efficient way to construct valuable nitro-containing oxindoles. © 2013 The Royal Society of Chemistry.

Ye Q.,CAS Lanzhou Institute of Chemical Physics | Ye Q.,Lanzhou University | Wang X.,CAS Lanzhou Institute of Chemical Physics | Li S.,Lanzhou University | Zhou F.,CAS Lanzhou Institute of Chemical Physics
Macromolecules | Year: 2010

A novel strategy is reported to produce low surface energy poly(pentadecafluorooctyl-5-norbornene-2-carboxylate) brushes (PNCA-F 15) on surfaces of variable metals and metallic oxides. PNCA-F 15 brushes are grafted from biomimic catecholic initiator via surface-initiated ring-opening metathesis polymerization at ambient conditions. The biomimic catecholic initiator can assemble on a variety of substrates, such as Ti(TiO2), Al(Al2O3), steel, Au, Cu, Ag, and Zn, and on both nanoparticles and planar substrates, allowing successful grafting of low surface energy polymer brushes from these substrates. The polymer brush modified substances were characterized by thermogravimetric analysis, X-ray photoelectron spectroscopy, water contact angle measurements, and atomic force microscopy. The PNCA-F15 brushes grow progressly with time with highly uniform surface coverage. Very uniform polymer layer with the thickness 11 nm is obtained after 2 h polymerization at 0.25 M monomer concentration. Thermogravimetric analysis shows the grafting amount of PNCA-F15 is 39.3% (2 h). Upon grafting on rough surfaces, e.g., electrochemically anodized alumina and titania, superhydrophobicity and superoleophobicity in particular can be achieved; e.g., the PNCA-F15 grafted rough TiO2 nanotubes films exhibit static water contact angle of 170°. © 2010 American Chemical Society.

Jin J.,CAS Lanzhou Institute of Chemical Physics | Jin J.,University of Chinese Academy of Sciences | Fu X.,CAS Lanzhou Institute of Chemical Physics | Fu X.,Lanzhou University | And 6 more authors.
ACS Nano | Year: 2013

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, I pa/Ipc = 1.38 at a scan rate of 50 mV s-1). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO]2+/[VO2] + couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO]2+/[VO 2]+ couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity. © 2013 American Chemical Society.

Long S.,University of Kentucky | Zhou P.,Lanzhou University | Parkin S.,University of Kentucky | Li T.,Purdue University
Crystal Growth and Design | Year: 2014

Carboxylic acid-acid hydrogen-bonding dimer and acid-pyridine hydrogen-bonding motif are two competing supramolecular synthons that a molecule possessing both carboxylic acid and pyridine functional groups could form in the solid state. Their coexistence has been observed but for the molecules with the molar ratio of carboxylic acid and pyridine groups being greater than 1:1. In this crystal engineering study, 2-[phenyl(propyl)amino]nicotinic acid with a 1:1 molar ratio of these two functional groups was discovered to have two polymorphs, in which one consists of unique hydrogen-bonded tetramer units bearing both acid-acid and acid-pyridine hydrogen-bonding motifs, while the other is composed of acid-pyridine hydrogen-bonded chains. Quantum mechanical calculations were employed to unravel the essence of the coexistence of the two vying counterparts as well as the origins of the tetramer and chain structures. © 2013 American Chemical Society.

Li C.-C.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Organic Letters | Year: 2015

(Figure Presented) The first rhodium(I)-catalyzed difunctionalization of arylacrylamides to synthesize oxindoles is developed, and it does not require the assistance of an oxidant. This method provides an efficient approach to generate various useful functionalized oxindoles, some of which cannot be easily accessed by previous approaches. © 2015 American Chemical Society.

Wu Z.-X.,Lanzhou University | Yang H.-X.,Fuzhou University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We study the evolution of cooperation in the evolutionary spatial prisoner's dilemma game (PDG) and snowdrift game (SG), within which a fraction α of the payoffs of each player gained from direct game interactions is shared equally by the immediate neighbors. The magnitude of the parameter α therefore characterizes the degree of the relatedness among the neighboring players. By means of extensive Monte Carlo simulations as well as an extended mean-field approximation method, we trace the frequency of cooperation in the stationary state. We find that plugging into relatedness can significantly promote the evolution of cooperation in the context of both studied games. Unexpectedly, cooperation can be more readily established in the spatial PDG than that in the spatial SG, given that the degree of relatedness and the cost-to-benefit ratio of mutual cooperation are properly formulated. The relevance of our model with the stakeholder theory is also briefly discussed. © 2014 American Physical Society.

Niu F.,Lanzhou University | Liu J.-M.,Lanzhou University | Tao L.-M.,CAS Lanzhou Institute of Chemical Physics | Wang W.,Lanzhou University | And 2 more authors.
Journal of Materials Chemistry A | Year: 2013

Nitrogen and silica co-doped graphene nanosheets (NSi-GNS) have been prepared via high-temperature annealing of N and Si-containing graphene oxide-ionic liquid (GO-IL) composite. As a p-type semiconductor, the as-synthesized NSi-GNS shows excellent NO2 gas sensing ability with high response value. © 2013 The Royal Society of Chemistry.

Xu A.,Lanzhou University | Wang J.,Henan Normal University | Wang H.,Henan Normal University
Green Chemistry | Year: 2010

Cellulose is the most abundant biorenewable and biodegradable resource on the earth. However, the extent of its application is limited due to its inefficient dissolution in solvents. Thus, the development of new cellulose solvents continues to be an active area of investigation. In this work, a series of ionic liquids (ILs) have been synthesized by coupling the 1-N-butyl-3-methylimidazolium cation [C4mim]+ with the Brønsted basic anions [CH3COO]-, [HSCH 2COO]-, [HCOO]-, [(C6H 5]COO]-, [H2NCH2COO]-, [HOCH2COO]-, [CH3CHOHCOO]- and [N(CN)2]-. The solubilities of microcrystalline cellulose (MCC) in these ionic liquids were determined as a function of temperature. The effect of the anion structure on the solubility of cellulose has been estimated, and investigated by 1H NMR and a solvatochromic UV/vis probe. It was found that the solubility of cellulose increases almost linearly with increasing hydrogen bond accepting ability of anions in the ionic liquids. At the same time, novel [C4mim][CH3COO]/lithium salt (LiCl, LiBr, LiAc, LiNO3, or LiClO4) solvent systems have been developed by adding 1.0 wt% of lithium salt into [C4mim][CH 3COO]. It was shown that the addition of lithium salts significantly increased the solubility of the cellulose. This observation was studied by 13C NMR spectra, and the results suggested that the enhanced solubility of cellulose originated from the disruption of the intermolecular hydrogen bond, O(6)H⋯O(3) owing to the interaction of Li+ with the hydroxyl oxygen O(3) of cellulose. Furthermore, the cellulose materials regenerated from the ionic liquids were characterized by scanning electron micrograph, thermogravimetric analysis and Fourier transform infrared spectroscopy, and the degree of polymerization of the original and regenerated cellulose materials was also determined. Good thermal stability was found for the regenerated cellulose. It is expected that the above information is useful for the design of novel ionic liquids and ionic liquid-based solvent systems for cellulose. © 2010 The Royal Society of Chemistry.

Yang B.,Lanzhou University | Yang T.-T.,Lanzhou University | Li X.-A.,Lanzhou University | Wang J.-J.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2013

A novel and selective method of simple copper-salt catalyzed phosphonation of α-amino carbonyl compounds to afford imidoylphosphonates is reported. This reaction system has a broad reaction scope. The convenient and environmentally benign process makes this protocol very attractive. © 2013 American Chemical Society.

Du P.,Lanzhou University | Zeng J.,Lanzhou University | Mu B.,CAS Lanzhou Institute of Chemical Physics | Liu P.,Lanzhou University
Molecular Pharmaceutics | Year: 2013

Well-defined biocompatible magnetic and molecular dual-targeting polyelectrolyte hybrid hollow microspheres have been accomplished via the layer-by-layer (LbL) self-assembly technique. The hybrid shell was fabricated by the electrostatic interaction between the polyelectrolyte cation, chitosan (CS), and the hybrid anion, citrate modified ferroferric oxide nanoparticles (Fe3O4-CA), onto the uniform polystyrene sulfonate microsphere templates. Then the magnetic hybrid core/shell composite particles were modified with a linear, functional poly(ethylene glycol) (PEG) monoterminated with a biotargeting molecule (folic acid (FA)). Afterward the dual targeting hybrid hollow microspheres were obtained after etching the templates by dialysis. The dual targeting hybrid hollow microspheres exhibit exciting pH response and stability in high salt-concentration media. Their pH-dependent controlled release of the drug molecule (anticancer drug, doxorubicin (DOX)) was also investigated in different human body fluids. As expected, the cell viability of the HepG2 cells which decreased more rapidly was treated by the FA modified hybrid hollow microspheres rather than the unmodified one in the in vitro study. The dual-targeting hybrid hollow microspheres demonstrate selective killing of the tumor cells. The precise magnetic and molecular targeting properties and pH-dependent controlled release offers promise for cancer treatment. © 2013 American Chemical Society.

Li Y.-M.,Lanzhou University | Sun M.,Lanzhou University | Wang H.-L.,Lanzhou University | Tian Q.-P.,Lanzhou University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2013

Silver screen: The AgNO3-catalyzed carbon phosphorylation of alkenes occurs by an alkene addition/cyclization cascade. Ag+ reacts with Ph2P(O)H to form the crucial active intermediate 1, which promotes the reaction. This method requires a cheap, nontoxic silver salt as the catalyst and substrates for the transformation are simple and readily accessible. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li X.-A.,Lanzhou University | Wang H.-L.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Organic Letters | Year: 2013

A novel method has been developed for the synthesis of substituted N-methylacridones from 2-(N-methyl-N-phenylamino)benzaldehydes via dehydrogenative cyclization. This transformation involves two primary processes: the aldehyde first coordinates with Sc(OTf)3 and induces the aromatic electrophilic substitution (SEAr) reaction to form the active intermediate N-methyl-acridin-9-ol, which is then quickly oxidized in situ to afford the acridones. Furthermore, the procedure involved is both environmental friendly and atom efficient; H2O is the only byproduct in this reaction. © 2013 American Chemical Society.

Li X.,Lanzhou University | Yang L.,Lanzhou University | Li Y.,Lanzhou University | Ye Z.,Beijing Institute of Technology | He A.,Lanzhou University
Journal of Environmental Engineering (United States) | Year: 2012

Batch adsorption experiments were conducted using environment-friendly prepared chelating ethylenediaminetetraacetic sodium modified polystyrene-based (PS-EDTA) resins as an adsorbent to adsorb Cd2+ from aqueous system in which experimental parameters were studied including solution pH, adsorbent dose, contact time, initial metal concentration and temperature. The Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherm models were employed to analyze the experimental data among which Freundlich isotherm model was found to be suitable for Cd2+ adsorption. In addition, Cd2+ adsorption on PS-EDTA resins fitted well to the pseudo-second-order kinetic model. Intraparticle diffusion studies revealed that surface adsorption and intraparticle diffusion were both involved in the adsorption of Cd2+ ions. Thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were calculated and indicated that adsorption of Cd2+ ions onto PS-EDTA resins was a spontaneous and endothermic process. The effects of various salts and coexisting heavy metal ions on Cd2+ ions adsorption were also investigated. Moreover, the results from the sequential adsorption-desorption cycles showed that PS-EDTA resins held good reusability and this could be a potential application in the fixed-bed continuous-flow column for the removal of heavy metals. © 2012 American Society of Civil Engineers.

Li H.,Lanzhou University | Yang M.,CAS Lanzhou Institute of Chemical Physics | Pu Q.,Lanzhou University
Microporous and Mesoporous Materials | Year: 2012

A mesoporous silica SBA-15-supported palladium with spindle-like nitrogen donor groups, 1,4-diaza-bicyclo[2.2.2]octane, has been successfully prepared and applied for homocoupling of terminal alkynes. The catalyst exhibited very high activity for terminal alkynes carrying various substitution groups, yields ranging from 70% to 94%, with a significant advantage that air acted as the oxidant. It also showed good reusability, could be easily recovered through filtration and washing, and reused at least five times with virtually no evident loss of catalytic performance. Furthermore, it was also proved to be an effective and air-stable heterogeneous catalyst for Suzuki coupling of aryl halides (X = I, Br) with arylboronic acids. The catalyst was systematically characterized by elemental analysis, X-ray photoelectron spectroscopy, high-resolution transmission electron microscope, nitrogen physical adsorption, Brunauer-Emmett-Teller method and X-ray powder diffraction. The analyses indicated that the mesoporous structure of the materials was retained during the immobilization process. © 2011 Elsevier Inc. All rights reserved.

Yang D.,Lanzhou University | Wang L.,Lanzhou University | Han F.,Lanzhou University | Zhao D.,Lanzhou University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2013

α, β, γ: The title method employs a Mg/L catalyst, which is well suited for the selective γ deprotonation and activation of linear α,β-unsaturated ketones for reaction with nitroalkenes. The reaction leads to a series of optically active cyclohexene ring systems bearing multiple functional groups, systems which are not easily accessible using other methodologies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xi P.,Brown University | Xi P.,Lanzhou University | Cheng K.,Brown University | Sun X.,Brown University | And 2 more authors.
Chemical Communications | Year: 2012

Magnetic 8 nm Fe 3O 4 nanoparticles (NPs) were synthesized and modified with dopamine (DPA) and polyethylene glycol (PEG) diacid. The water soluble Fe 3O 4-DPA-PEG NPs were then conjugated with the fluorescent Eu(iii) complex of tris(dibenzoylmethane)-5- amino-1,10-phenanthroline (BMAP), giving an Fe 3O 4-DPA-PEG- BMAP-Eu NP conjugate. The conjugate was both colloidally and chemically stable in phosphate buffered solutions and could be used as a probe for magnetic resonance and fluorescent imaging. © 2012 The Royal Society of Chemistry.

Cui X.,CAS Lanzhou Institute of Chemical Physics | Cui X.,Lanzhou University | Deng Y.,CAS Lanzhou Institute of Chemical Physics | Shi F.,CAS Lanzhou Institute of Chemical Physics
ACS Catalysis | Year: 2013

As the sustainable and promising hydrogen source, here, glycerol was directly used as the hydrogen source for the reductive amination of alcohol using nitrobenzene as the starting material. The amination of alcohols, especially aliphatic alcohols with different structures, was realized, and mono- or disubstituted amines were synthesized with excellent yields. The reaction mechanism was also explored. © 2013 American Chemical Society.

Guo S.,CAS Lanzhou Institute of Chemical Physics | Qian B.,CAS Lanzhou Institute of Chemical Physics | Xie Y.,CAS Lanzhou Institute of Chemical Physics | Xia C.,CAS Lanzhou Institute of Chemical Physics | And 2 more authors.
Organic Letters | Year: 2011

An efficient and conceptually new method for oxidative amination of azoles with tertiary amines via copper-catalyzed C-H and C-N bond activation has been developed. This protocol can be performed in the absence of external base and only requires atmospheric oxygen as oxidant. The catalyst system is very simple and efficient, which opens a new way for using tertiary amines as nitrogen group sources for C-N bond formation reactions. © 2011 American Chemical Society.

Elston R.G.,University of Nevada, Reno | Guanghui D.,Lanzhou University | Dongju Z.,Lanzhou University
Quaternary International | Year: 2011

Intensification technologies used in late Pleistocene northern China include microblades, milling stones and pottery, all of which have been implicated in development of agriculture in northern China, perhaps influenced by the harsh climate of the Younger Dryas. This paper examines the adaptive function of these technologies in the context of late Pleistocene climate and environment. It is proposed that microlithic technology was a tool of mobile foragers focused on hunting, and the initial use of pottery was probably connected to bone grease production. Only milling stones were initially a plant-oriented intensification technology, but their sparse, episodic appearance in the late Pleistocene did not lead to persistent intensification involved in the development of agriculture. It was only after the Younger Dryas in the context of improved Holocene climate and greater primary productivity that these three technologies converged with changes in mobility to become part of the agricultural revolution in northern China. © 2011 Elsevier Ltd and INQUA.

Yang L.,CAS Lanzhou Institute of Chemical Physics | Qian B.,CAS Lanzhou Institute of Chemical Physics | Huang H.,CAS Lanzhou Institute of Chemical Physics | Huang H.,Lanzhou University
Chemistry - A European Journal | Year: 2012

Acid test: With a Brønsted acid as the solvent, the rhodium-catalyzed direct addition of aryl C-H bonds to α,β- unsaturated ketones was realized under mild reaction conditions (see scheme). The acid may assist by interceding in the conflict of the two proton-transfer events and averting the substrate inhibition involved in this type of C-H addition reaction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang Y.-F.,University of Hong Kong | Feng Y.-Y.,East China University of Science and Technology | Ma X.,Lanzhou University | Gu J.-D.,University of Hong Kong
Applied Microbiology and Biotechnology | Year: 2013

Mangrove wetlands are an important ecosystem in tropical and subtropical regions, and the sediments may contain both oxic and anoxic zones. In this study, ammonia/ ammonium-oxidizing prokaryotes (AOPs) in yellow and black sediments with vegetation and non-vegetated sediments in a mangrove wetland of subtropical Hong Kong were investigated in winter and summer. The phylogenetic diversity of anammox bacterial 16S rRNA genes and archaeal and bacterial amoA genes (encoding ammonia monooxygenase alpha-subunit) were analyzed using PCR amplification and denaturing gradient gel electrophoresis to reveal their community structures. Quantitative PCR was also used to detect their gene abundances. The results showed that seasonality had little effect, but sediment type had a noticeable influence on the community structures and abundances of anammox bacteria. For ammoniaoxidizing archaea (AOA), seasonality had a small effect on their community structures, but a significant effect on their abundances: AOA amoA genes were significantly higher in winter than in summer. In winter, the vegetated yellow sediments had lower AOA amoA genes than the other types of sediments, but in summer, the vegetated yellow sediments had higher AOA amoA genes than the other types of sediments. Sediment type had no apparent effect on AOA community structures in winter. In summer, however, the vegetated yellow sediments showed obviously different AOA community structures from the other types of sediments. For ammonia-oxidizing bacteria (AOB), seasonality had a significant effect on their community structures and abundances: AOB amoA genes in winter were apparently higher than in summer, and AOB community structures were different between winter and summer. Sediment type had little effect on AOB community structures, but had a noticeable effect on the abundances: AOB amoA genes of the vegetated yellow sediments were obviously lower than the black ones in both seasons. This study has demonstrated that seasonality and sediment type affected community structures and abundances of AOPs differently in oxic and anoxic sediments of the mangrove wetland. © The Author(s) 2012. This article is published with open access at

Hu R.-B.,Lanzhou University | Zhang H.,Lanzhou University | Zhang X.-Y.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Chemical Communications | Year: 2014

Palladium-catalyzed arylation of (diisopropylphosphoryl)biphenyl skeleton derivatives by the P(O)R2 directed C-H functionalization was reported. The related products were obtained in high regioselectivity and good functional group tolerance was observed. This reaction provided a new and efficient pathway for the synthesis of polyaromatic monophosphorus ligands. This journal is © The Royal Society of Chemistry.

Zhang H.,Lanzhou University | Hu R.-B.,Lanzhou University | Zhang X.-Y.,Lanzhou University | Li S.-X.,Lanzhou University | And 2 more authors.
Chemical Communications | Year: 2014

A novel and efficient Pd-catalyzed C-H acetoxylation is described. The approach uses R2(O)P as a directing group to synthesize various substituted 2′-phosphorylbiphenyl-2-OAc compounds. Notably, the reaction exhibits smooth operation under mild conditions and shows good functional group tolerance. Products are obtained with high selectivity and yields. This journal is © the Partner Organisations 2014.

Wei X.-H.,Lanzhou University | Li Y.-M.,Lanzhou University | Zhou A.-X.,Lanzhou University | Yang T.-T.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2013

A novel and inexpensive method of nontoxic, silver-salt-catalyzed carboazidation of arylacrylamides to afford corresponding azide oxindoles is reported. This reaction system exhibits great functional group tolerance. All products form a crucial skeleton for the synthesis of various indole alkaloids. © 2013 American Chemical Society.

Zhang H.-Y.,Lanzhou University | Yi H.-M.,Lanzhou University | Wang G.-W.,Lanzhou University | Yang B.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2013

A novel R2(O)P-directed Pd(II)-catalyzed C-H hydroxylation to synthesize various substituted 2′-phosphorylbiphenyl-2-ol compounds is described. Notably, the reaction operates under mild conditions and shows good functional group tolerance, high selectivity, and yield. © 2013 American Chemical Society.

Yang H.-X.,Fuzhou University | Wu Z.-X.,Lanzhou University | Wang B.-H.,Hefei University of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

The interplay between traffic dynamics and epidemic spreading on complex networks has received increasing attention in recent years. However, the control of traffic-driven epidemic spreading remains to be a challenging problem. In this Brief Report, we propose a method to suppress traffic-driven epidemic outbreak by properly removing some edges in a network. We find that the epidemic threshold can be enhanced by the targeted cutting of links among large-degree nodes or edges with the largest algorithmic betweenness. In contrast, the epidemic threshold will be reduced by the random edge removal. These findings are robust with respect to traffic-flow conditions, network structures, and routing strategies. Moreover, we find that the shutdown of targeted edges can effectively release traffic load passing through large-degree nodes, rendering a relatively low probability of infection to these nodes. © 2013 American Physical Society.

Wang B.,University of New South Wales | Wang B.,Lanzhou University | Yu A.B.,University of New South Wales
AIChE Journal | Year: 2010

The motion of solid particles and the "fish-hook" phenomenon in an industrial classifying hydrocyclone of body diameter 355 mm is studied by a computational fluid dynamics model. In the model, the turbulent flow of gas and liquid is modeled using the Reynolds Stress Model, and the interface between the liquid and air core is modeled using the volume of fluid multiphase model. The outcomes are then applied in the simulation of particle flow described by the stochastic Lagrangian model. The results are analyzed in terms of velocity and force field in the cyclone. It is shown that the pressure gradient force plays an important role in particle separation, and it balances the centrifugal force on particles in the radial direction in hydrocyclones. As particle size decreases, the effect of drag force whose direction varies increases sharply. As a result, particles have an apparent fluctuating velocity. Some particles pass the locus of zero vertical velocity (LZVV) and join the upward flow and have a certain moving orbit. The moving orbit of particles in the upward flow becomes wider as their size decreases. When the size is below a critical value, the moving orbit is even beyond the LZVV. Some fine particles would recircuit between the downward and upward flows, resulting in a relatively high separation efficiency and the "fish-hook" effect. Numerical experiments were also extended to study the effects of cyclone size and liquid viscosity. The results suggest that the mechanisms identified are valid, although they are quantitatively different. © 2009 American Institute of Chemical Engineers.

Zhu L.,Lanzhou University | Liu P.,Lanzhou University | Wang A.,CAS Lanzhou Institute of Chemical Physics
Industrial and Engineering Chemistry Research | Year: 2014

Attapulgite/poly(acrylic acid) nanocomposite (ATP/PAA) hydrogels with high clay content of around 90% have been synthesized by a novel surface-initiated redox radical solution polymerization of acrylic acid (AA) with the 3-aminopropyltriethoxysilane (APTES) modified attapulgite nanorods (ATP-NH 2) as initiator and the 3-methacryloxypropyltrimethoxysilane (MPTMS) modified attapulgite nanorods (ATP-Cî - C) as cross-linker. High inorganic-content nanocomposite (ATP/PAA) hydrogel with a three-dimensional network structure was obtained via the linkage of the different functional attapulgite nanorods with the grafted poly(acrylic acid) (PAA) chains. Both the two kinds of the functional attapulgite nanorods acted as the cross-linking sites in the nanocomposite hydrogel. Due to its unique structure, a remarkably high adsorption capacity of the cationic dye (methylene blue (MB)) of 308.0 mg/g was achieved when the ATP/PAA nanocomposite hydrogel was used as the adsorbent for water treatment. © 2014 American Chemical Society.

Wang H.-L.,Lanzhou University | Hu R.-B.,Lanzhou University | Zhang H.,Lanzhou University | Zhou A.-X.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2013

The Pd(II)-catalyzed Ph2(O)P-directed C-H olefination to synthesize alkene-phosphine compounds is reported. In contrast to previous examples of various directing groups that guide selective C-H activation, the Ph2(O)P group not only acts as the directing group but also serves to construct the alkene-phosphine ligands. The monoprotected amino acid (MPAA) ligand Ac-Leu-OH is found to promote this reaction in a significant manner. © 2013 American Chemical Society.

Wang G.-W.,Lanzhou University | Zhou A.-X.,Lanzhou University | Wang J.-J.,Lanzhou University | Hu R.-B.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2013

The first Pd(II)-catalyzed C-H addition to isatins by direct sp 2/sp3 C-H bond activation for the construction of 3-substituted-3-hydroxy-2-oxindoles is reported. The bidentate nitrogen ligands were found to promote this reaction. Specifically, the preliminary bioassay indicated that 3-(5-chlorobenzoxazole)-3-hydroxy-N-benzyl-2-oxindole (2w) is a new inhibitor of human kidney cancer and hepatocellular carcinoma cells. Moreover, this reaction system exhibits great functional group tolerance and requires no directing group, extra base, or additives. © 2013 American Chemical Society.

He Y.-T.,Lanzhou University | Li L.-H.,Lanzhou University | Yang Y.-F.,Lanzhou University | Zhou Z.-Z.,Lanzhou University | And 4 more authors.
Organic Letters | Year: 2014

A novel and highly practical reaction for the copper-catalyzed intermolecular cyanotrifluoromethylation of alkenes is presented here. This methodology provides a general and straightforward way to synthesize a variety of useful CF3-containing nitriles, which can be used for further preparation of pharmaceutically and agrochemically important compounds in synthetic organic chemistry. © 2013 American Chemical Society.

Yang J.-L.,Lanzhou University | Shi Y.-P.,Lanzhou University | Shi Y.-P.,CAS Lanzhou Institute of Chemical Physics
Phytochemistry | Year: 2012

Cycloartane-type triterpenoids (1-3), seven sesquiterpenoids (7-13), and five previously reported secondary metabolites, including three cycloartane-type triterpenoids (4-6) and two sesquiterpenoids (14 and 15), were isolated from the resinous exudates of Commiphora opobalsamum. Their structures were elucidated by extensive spectroscopic analysis, including UV, IR, NMR, and MS, and comparison with literature data. The structures of 1, 3, and 7 were confirmed by single-crystal X-ray diffraction analysis. The absolute configuration of 1 was interpreted by the incorporation of CHCl3 (crystallization solvent) in the crystal and that of 10 was determined by the CD exciton chirality method. Compound 12 represents the first example of a 12-norcadinane-type sesquiterpenoid. Furthermore, compounds 1, 3, 7, and 10-14 were evaluated for cytotoxicity against HeLa and HepG2 cell lines. © 2011 Elsevier Ltd. All rights reserved.

Xia X.-F.,Lanzhou University | Zhang L.-L.,Lanzhou University | Song X.-R.,Lanzhou University | Liu X.-Y.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2012

A novel copper-catalyzed oxidative cyclization of enynes and in situ formed enynes leading to 4-carbonyl-quinolines by using dioxygen as an oxygen source has been developed. © 2012 American Chemical Society.

Ye W.,Lanzhou University | Chen Y.,Lanzhou University | Zhou F.,CAS Lanzhou Institute of Chemical Physics | Wang C.,Lanzhou University | Li Y.,Key Laboratory of Digestive System Tumors
Journal of Materials Chemistry | Year: 2012

Although Al has a lower redox potential [Al 3+/Al, -1.67 V vs. SHE] than most metallic ions, metal galvanic replacement reactions on pure aluminum foil can be hardly observed because of the existence of the thin layer of aluminum oxide, In this work, we develop a facile, economical and general approach to achieve large-scale production of silver and gold dendrites as well as other metal hierarchical micro/nanostructures (Cu, Pt, Pd, Ni, Co and Zn) on commercial aluminum foil in the presence of NaF or NH 4F. Studies of the galvanic replacement reaction by open circuit potential-time (OCP-t) measurements demonstrate that fluoride plays an important role in etching the alumina layer and thus induces the continuous proceeding of the galvanic replacement reaction. The synthesis process is carried out at room temperature and without any templates, surfactants, or special reagents. The obtained silver and gold dendrites show significantly enhanced SERS signals of a self-assembled monolayer of 2-naphthalenethiol and 4-mercaptobenzoic acid, and also could effectively catalyze the reduction reaction of 4-nitrophenol and 2-nitrophenol at room temperature. © 2012 The Royal Society of Chemistry.

Wei X.-H.,Lanzhou University | Wang G.-W.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Chemical Communications | Year: 2015

A new method for the synthesis of chiral α-amino acid derivatives by enantioselective C-H arylation of N-aryl glycine esters with aryl boric acids in the presence of a chiral Pd(ii)-catalyst has been developed. This work successfully integrates the direct C-H oxidation with asymmetric arylation and exhibits excellent enantioselectivity. This journal is © The Royal Society of Chemistry 2015.

Yang C.,Lanzhou University | Liu P.,Lanzhou University | Wang T.,CAS Lanzhou Institute of Chemical Physics
ACS Applied Materials and Interfaces | Year: 2011

The well-defined core-shell carbon black/polypyrrole (CB/PPy) nanocomposites were prepared via the in situ chemical oxidative polymerization of pyrrole from the surfaces of the carbon black (CB) nanoparticles, with poly(2-hydroxy-3-(methacryloyloxy) propane-1-sulfonate) (PHMAS) as both the surfactant and the dopant. The nanocomposites exhibited the high conductivity at room temperature and the weakly temperature dependence of conductivity from 283 to 423 K. When the core-shell CB/PPy nanocomposites were used as the electrode materials for the supercapacitors, the maximum discharge capacity of 366 F/g was achieved, after being corrected for the weight percentage of the PPy phase at the current density of 5 mA/cm2 in 1.0 M NaNO3 electrolyte solution. © 2011 American Chemical Society.

Qian B.,CAS Lanzhou Institute of Chemical Physics | Xie P.,CAS Lanzhou Institute of Chemical Physics | Xie Y.,CAS Lanzhou Institute of Chemical Physics | Huang H.,CAS Lanzhou Institute of Chemical Physics | Huang H.,Lanzhou University
Organic Letters | Year: 2011

A novel iron-catalyzed alkenylation of 2-substituted azaarenes through sp3 C-H bond activation has been developed. A favorable E2-elimination is proposed as a key step to cleavage of C-H and C-N bonds for the construction of a C=C bond in high stereoselectivity. This transformation represents an efficient way to synthesize 2-alkenylated azaarenes from simple starting materials. © 2011 American Chemical Society.

Wang Y.,CAS Lanzhou Institute of Chemical Physics | Wang Y.,University of Chinese Academy of Sciences | Lu X.,Lanzhou University | Liu Y.,Lanzhou University | Deng Y.,CAS Lanzhou Institute of Chemical Physics
Electrochemistry Communications | Year: 2013

The electroreduction of oxygen was firstly studied on Ag/Co 3O4-C in alkaline media prepared by depositing Ag on Co3O4 modified carbon (Co3O4-C). The Ag/Co3O4-C composite not only displayed relatively large electrochemical active surface area (ESA), high catalytic activity towards oxygen reduction reaction (ORR), but also exhibited good methanol tolerance and stability in alkaline media. Ag/Co3O4-C could be a valuable catalyst for ORR and be applied to alkaline fuel cells and metal-air batteries. © 2013 Elsevier B.V.

Liu L.,Southern Medical University | Deng X.,Southern Medical University | Chen X.,Lanzhou University
Journal of Chromatography A | Year: 2010

An analytical strategy micelle to trapping solution stacking (MSS) was developed in acidic buffer in micellar electrokinetic chromatography (MEKC). The stacking mechanism is based on the transport, release, capturing of molecules bound to micelle carriers that are made to collapse into trapping solution (TS) to serve as the medium to contain and stacking the analytes. Tetrandrine and fangchinoline were selected as model mixture using sodium dodecyl sulfate (SDS) micelles as carrier to demonstrate this stacking method. The experiments by MSS-MEKC were carried out and further compared with those by normal MEKC. The results reveal that 113-123-fold improvements in the detection sensitivity was obtained for the analytes, and separation and determination of tetrandrine and fangchinoline in Stephaniae tetrandrae S. Moore and Fengtongan capsules were finished under optimum conditions using the sample matrix containing 8.0 mM SDS and TS containing 50 mM H3PO4-55% (v/v) ethanol. © 2009 Elsevier B.V. All rights reserved.

Wang G.-W.,Lanzhou University | Zhou A.-X.,Lanzhou University | Li S.-X.,Lanzhou University | Yang S.-D.,Lanzhou University | Yang S.-D.,CAS Lanzhou Institute of Chemical Physics
Organic Letters | Year: 2014

A palladium-catalyzed allylic C-H arylation reaction with electron-deficient arenes with high regio- and stereoselectivity is reported. This work represents the first successful use of 1,1′-bi-2-naphthol as the ancillary ligand in allylic C-H activation, which is the key factor for chemoselectivity. Furthermore, high selectivity allylic C-H acetoxylation and amination were also successfully achieved under the same catalytic system. © 2014 American Chemical Society.

Li H.,CAS Lanzhou Institute of Chemical Physics | Yang M.,CAS Lanzhou Institute of Chemical Physics | Qi Y.,CAS Lanzhou Institute of Chemical Physics | Xue J.,Lanzhou University
European Journal of Organic Chemistry | Year: 2011

The carbonylative Suzuki cross-coupling reactions of boronic acids with aryl iodides catalyzed by Pd2(dba)3 as a ligand-free catalyst under atmospheric pressure of carbon monoxide has been firstly developed. Under mild reaction conditions, a broad range of aryl/heteroaryl iodides and aryl/heteroaryl boronic acids were selectively coupled to afford the corresponding diaryl ketones in good to excellent yields at low catalyst loadings (0.05 to 2 mol-%). Moreover, the catalyst can also be recycled. The carbonylative Suzuki cross-coupling reactions of boronic acids with aryl iodides catalyzed by Pd2(dba)3 as a ligand-free catalyst under an atmosphere of carbon monoxide has been developed. A broad range of aryl/heteroaryl iodides and aryl/heteroaryl boronic acids were selectively coupled to afford the corresponding diaryl ketones in good to excellent yields. The catalyst can also be recycled. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Duan H.,Massachusetts Institute of Technology | Duan H.,Lanzhou University | Berggren K.K.,Massachusetts Institute of Technology
Nano Letters | Year: 2010

We demonstrated a new nanoassembly strategy based on capillary force-induced cohesion of high-aspect ratio nanostructures made by electron-beam lithography. Using this strategy, ordered complex pattern were fabricated from individual nanostructures at the 10 nm length scale. This method enables the formation of complex designed networks from a sparse array of nanostructures, suggesting a number of potential applications in fabrication of nanodevices, nanopatterning, and fluid-flow investigations. © 2010 American Chemical Society.

Ling X.,University of Science and Technology Beijing | Xie L.,University of Science and Technology Beijing | Fang Y.,University of Science and Technology Beijing | Xu H.,CAS Beijing National Laboratory for Molecular | And 6 more authors.
Nano Letters | Year: 2010

Graphene is a monolayer of carbon atoms packed into a two-dimensional (2D) honeycomb crystal structure, which is a special material with many excellent properties. In the present study, we will discuss the possibility that graphene can be used as a substrate for enhancing Raman signals of adsorbed molecules. Here, phthalocyanine (Pc), rhodamine 6G (R6G), protoporphyin IX (PPP), and crystal violet (CV), which are popular molecules widely used as a Raman probe, are deposited equally on graphene and a SiO2/Si substrate using vacuum evaporation or solution soaking. By comparing the Raman signals of molecules on monolayer graphene and on a SiO2Si substrate, we observed that the intensities of the Raman signals on monolayer graphene are much stronger than on a SiO2/Si substrate, indicating a clear Raman enhancement effect on the surface of monolayer graphene. For solution soaking, the Raman signals of the molecules are visible even though the concentration is low to 10-8 mol/L or less. What's more interesting, the enhanced efficiencies are quite different on monolayer, few-layer, multilayer graphene, graphite, and highly ordered pyrolytic graphite (HOPG). The Raman signals of molecules on multilayer graphene are even weaker than on a SiO2/Si substrate, and the signals are even invisible on graphite and HOPG. Taking the Raman signals on the SiO2/Si substrate as a reference. Raman enhancement factors on the surface of monolayer graphene can be obtained using Raman Intensity ratios. The Raman enhancement factors are quite different for different peaks, changing from 2 to 17. Furthermore, we found that the Raman enhancement factors can be distinguished through three classes that correspond to the symmetry of vibrations of the molecule. We attribute this enhancement to the charge transfer between graphene and the molecules, which result in a chemical enhancement. This is a new phenomenon for graphene that will expand the application of graphene to microanalysis and is good for studying the basic properties of both graphene and SERS. © 2010 American Chemical Society.

Lu B.,Hunan University | Lu B.,Lanzhou University | Li X.,Lanzhou University | Wang T.,Hunan University | And 2 more authors.
Journal of Materials Chemistry A | Year: 2013

The hybrid structure of nanoparticle-decorated nanotubes has the advantage of both large specific surface areas of nanoparticles and anisotropic properties of nanotubes, which is desirable for many applications. In this study, WO 3 nanoparticles decorated on highly porous TiO2 nanotubes along both internal and external sidewalls (WO3@TiO 2@WO3 heterostructures) were synthesized through emulsion electrospinning, thermal evaporation, and thermal annealing. The WO 3@TiO2@WO3 heterostructures had large specific surface areas, high porous structure and excellent interface (between WO 3 nanoparticles and TiO2 nanotubes). Three other samples, TiO2 nanofibers, TiO2 nanotubes, and TiO2 nanofibers decorated by WO3 nanoparticles, were prepared in order to compare with the WO3@TiO2@WO3 heterostructures for photocatalysis with both UV and visible light irradiation. The new material (WO3@TiO2@WO3 heterostructures) had a wide range of light absorption and demonstrated the best photocatalytic performance. The possible growth mechanism and reasons for high photocatalysis are discussed in detail. © 2013 The Royal Society of Chemistry.

Zhang H.-F.,Anhui University | Yang Z.,University of Electronic Science and Technology of China | Wu Z.-X.,Lanzhou University | Wang B.-H.,Hefei University of Technology | Zhou T.,University of Electronic Science and Technology of China
Scientific Reports | Year: 2013

Facing the threats of infectious diseases, we take various actions to protect ourselves, but few studies considered an evolving system with competing strategies. In view of that, we propose an evolutionary epidemic model coupled with human behaviors, where individuals have three strategies: vaccination, self-protection and laissez faire, and could adjust their strategies according to their neighbors' strategies and payoffs at the beginning of each new season of epidemic spreading. We found a counter-intuitive phenomenon analogous to the well-known Braess's Paradox, namely a better condition may lead to worse performance. Specifically speaking, increasing the successful rate of self-protection does not necessarily reduce the epidemic size or improve the system payoff. The range and degree of the Braess's Paradox are sensitive to both the parameters characterizing the epidemic spreading and the strategy payoff, while the existence of the Braess's Paradox is insensitive to the network topologies. This phenomenon can be well explained by a mean-field approximation. Our study demonstrates an important fact that a better condition for individuals may yield a worse outcome for the society.

Fu Q.,University of Washington | Fu Q.,Lanzhou University | Solomon S.,National Oceanic and Atmospheric Administration | Lin P.,University of Washington
Atmospheric Chemistry and Physics | Year: 2010

This study examines the seasonality of tropical lower-stratospheric temperature trends using the Microwave Sounding Unit lower-stratospheric channel (T4) for 1980-2008. We present evidence that this seasonality is largely a response to changes in the Brewer-Dobson circulation (BDC) driven by extratropical wave forcing. We show how the tropical T4 trend can be used as an indicator of changes in the BDC, and find that the BDC is strengthening for 1980-2008 in June-November related to the Southern Hemisphere (SH) and in December-February to the Northern Hemisphere (NH). In marked contrast, we find that the BDC is weakening in March-May, apparently because of a weakening of its northern cell. The novel observational evidence on the seasonal dependence of the BDC trends presented in this study has important implications for the understanding of climate change in the stratosphere as well as testing climate model simulations. © Author(s) 2010.

Fan J.-H.,Hunan University | Wei W.-T.,Hunan University | Zhou M.-B.,Hunan University | Song R.-J.,Hunan University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2014

The oxidative interception of various σ-alkyl palladium(II) intermediates with additional reagents for the difunctionalization of alkenes is an important research area. A new palladium-catalyzed oxidative difunctionalization reaction of alkenes with α-carbonyl alkyl bromides is described, in which the σ-alkyl palladium(II) intermediate is generated through a Heck insertion and trapped using an aryl C(sp2)-H bond. This method can be applied to various α-carbonyl alkyl bromides, including primary, secondary, and tertiary α-bromoalkyl esters, ketones, and amides. Indolinone synthesis: A new palladium-catalyzed oxidative difunctionalization reaction of N-arylalkenes with primary, secondary, and tertiary α-carbonyl alkyl bromides proceeds through a radical process and provides indolin-2-ones in moderate to excellent yields. The reaction is initiated by a Heck insertion followed by interception of the σ-alkyl palladium(II) intermediate with aryl C(sp2)-H bonds. dppe=1,2-bis(diphenylphosphino)ethane. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hu M.,Hunan University | Song R.-J.,Hunan University | Li J.-H.,Hunan University | Li J.-H.,Lanzhou University
Angewandte Chemie - International Edition | Year: 2015

A new metal-free radical 5-exo-dig cyclization of phenol-linked 1,6-enynes with O2, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), and tBuONO is described. With this general method, carbonylated benzofurans can be accessed through incorporation of two oxygen atoms into the product from O2 and TEMPO through dioxygen activation and oxidative cleavage of the N-O bond, respectively. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

Zhou M.-B.,Hunan University | Song R.-J.,Hunan University | Wang C.-Y.,Hunan University | Li J.-H.,Hunan University | Li J.-H.,Lanzhou University
Angewandte Chemie - International Edition | Year: 2013

Silver forges the ring: A new and practical silver-catalyzed [5+2] cycloaddition method has been developed for the synthesis of azepines through the formation of four new chemical bonds between a γ-amino ketone and an alkyne in one step. This method provides a new hetero-[5+2] cycloaddition strategy for the construction of seven-membered ring systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang Y.,Hunan University | Zhou M.-B.,Hunan University | Ouyang X.-H.,Hunan University | Pi R.,Hunan University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2015

A rhodium(III)-catalyzed [3+2]/[5+2] annulation of 4-aryl 1-tosyl-1,2,3-triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7-cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp2)-H functionalization, and [3+2]/[5+2] annulation. A quantum leap in complexity: A general strategy based on rhodium(III) azavinyl carbene intermediates was established for the oxidative [3+2]/[5+2] annulation of 4-aryl 1-tosyl-1,2,3-triazoles with alkynes. This general method provided densely functionalized indeno[1,7-cd]azepine architectures with excellent selectivity through the functionalization of two C(sp2)-H bonds (see scheme; Cp∗=pentamethylcyclopentadienyl, Ts= p-toluenesulfonyl). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liu Y.,Hunan University | Zhang J.-L.,Hunan University | Song R.-J.,Hunan University | Qian P.-C.,Hunan University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2014

Here we describe the one-pot construction of the pyrrolo[4,3,2-de] quinolinone scaffold by a cascade nitration/cyclization sequence of 1,7-enynes with tBuONO and H2O. The cascade proceeds through alkene nitration, 1,7-enyne 6-exo-trig cyclization, C-H nitrations, and redox cyclization, and exhibits excellent functional group tolerance. The mechanism was investigated using in situ high-resolution mass spectrometry (HR-MS). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wu Z.-X.,Lanzhou University | Rong Z.,University of Electronic Science and Technology of China | Rong Z.,Hong Kong Polytechnic University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We study the evolution of cooperation in spatial prisoner's dilemma games with and without extortion by adopting the aspiration-driven strategy updating rule. We focus explicitly on how the strategy updating manner (whether synchronous or asynchronous) and also the introduction of extortion strategy affect the collective outcome of the games. By means of Monte Carlo simulations as well as dynamical cluster techniques, we find that the involvement of extortioners facilitates the boom of cooperators in the population (and whom can always dominate the population if the temptation to defect is not too large) for both synchronous and asynchronous strategy updating, in stark contrast to the other case, where cooperation is promoted for an intermediate aspiration level with synchronous strategy updating, but is remarkably inhibited if the strategy updating is implemented asynchronously. We explain the results by configurational analysis and find that the presence of extortion leads to the checkerboard-like ordering of cooperators and extortioners, which enable cooperators to prevail in the population with both strategy updating manners. Moreover, extortion itself is evolutionary stable, and therefore acts as the incubator for the evolution of cooperation. © 2014 American Physical Society.

Cui P.,Lanzhou University | Tang M.,University of Electronic Science and Technology of China | Wu Z.-X.,Lanzhou University
Scientific Reports | Year: 2014

Recent empirical studies have confirmed the key roles of complex contagion mechanisms such as memory, social reinforcement, and decay effects in information diffusion and behavior spreading. Inspired by this fact, we here propose a new agent-based model to capture the whole picture of the joint action of the three mechanisms in information spreading, by quantifying the complex contagion mechanisms as stickiness and persistence, and carry out extensive simulations of the model on various networks. By numerical simulations as well as theoretical analysis, we find that the stickiness of the message determines the critical dynamics of message diffusion on tree-like networks, whereas the persistence plays a decisive role on dense regular lattices. In either network, the greater persistence can effectively make the message more invasive. Of particular interest is that our research results renew our previous knowledge that messages can spread broader in networks with large clustering, which turns out to be only true when they can inform a non-zero fraction of the population in the limit of large system size. © 2014 Macmillan Publishers Limited. All rights reserved.

Zhou M.-B.,Hunan University | Song R.-J.,Hunan University | Li J.-H.,Hunan University | Li J.-H.,Lanzhou University
Angewandte Chemie - International Edition | Year: 2014

A practical method for the synthesis of azepine derivatives, a typical seven-membered heterocyclic ring system, was developed and involves the use of hexafluoroantimonic acid to catalyze a formal [3+2+2] cycloaddition of aziridines with two alkynes. This method was applicable to two of the same or different terminal alkynes for the [3+2+2] cycloaddition with unactivated aziridines, and furnished the corresponding azepine derivatives in good yields with good levels of chemo- and regioselectivity. The mechanism was also discussed according to the results of the in situ HRMS and 1H NMR analysis. Superacid powers: The title reaction of unactivated aziridines with two of the same or different terminal alkyne components has been developed, thus opening a new access to seven-membered heterocyclic ring systems. This transformation is experimentally simple while furnishing azepine derivatives in good yields (up to 78%) with good levels of chemo- and regioselectivity. Ts= 4-toluenesulfonyl. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang B.,Lanzhou University | Wang B.,Dalian University of Technology | Tu Y.Q.,Lanzhou University
Accounts of Chemical Research | Year: 2011

Quaternary carbon stereocenters are found in a broad range of organic compounds, including important bioactive natural products and medicinal agents. Given their ubiquity and the significant synthetic challenges they present, quaternary carbon stereocenters have long attracted great interest from synthetic organic chemists. Numerous efforts have been devoted to their construction, leading to a spectrum of strategies for creating stereogenic quaternary carbon centers. In this context, the semipinacol rearrangement has proven successful. In this extension of the pinacol rearrangement, the 1,2-carbon-to-carbon migration in a 1,2-diol has been expanded to include leaving groups other than the hydroxyl group.Over the past decade, our laboratory has explored the semipinacol rearrangement strategy for the stereoselective construction of quaternary carbon stereocenters. We have investigated various substrates, including 2,3-epoxy alcohols (also termed α-hydroxy epoxides), 2,3-aziridino alcohols, and allylic alcohols. Several promoters that effect the semipinacol rearrangement have been identified, including Lewis acids based on Al, Sm, B, Zn, and Ti for the rearrangement of α-hydroxy epoxides and 2,3-aziridino alcohols; cationic halogen species for the rearrangement of allylic alcohols; and cinchona alkaloids and chiral phosphoric acid for the asymmetric semipinacol rearrangement. Our research efforts have led to a series of valuable synthetic methods, including (1) a tandem semipinacol rearrangement and Meerwein-Ponndorf-Verley reduction, (2) a tandem semipinacol rearrangement and Tishchenko reaction, (3) a tandem semipinacol rearrangement with either an allylation or a propargylation, (4) a tandem semipinacol rearrangement and Schmidt reaction, (5) a semipinacol rearrangement of 2,3-aziridino alcohols, (6) a semipinacol rearrangement of allylic alcohols induced by halogen cation, (7) a tandem aziridination and semipinacol rearrangement of allylic alcohols, and (8) asymmetric semipinacol rearrangements with chiral organic catalysts. One hallmark of these reactions is the creation of stereogenic quaternary carbon centers with high levels of stereocontrol. In this Account, we describe the development of these synthetically useful methodologies and their successful application to the total syntheses of natural products.Our results demonstrate that the semipinacol rearrangement of carefully designed substrates constitutes an efficient approach to the stereoselective construction of quaternary carbon centers. These reactions have produced a broad array of useful compounds that lend themselves to further elaboration. Furthermore, the total synthesis of a series of alkaloids, with significant bioactivity and intriguing molecular architecture, was achieved through these semipinacol rearrangement strategies, highlighting their synthetic value. © 2011 American Chemical Society.

Zhang B.-X.,Lanzhou University | Gao H.,Lanzhou University | Li X.-L.,CAS Shanghai Institute of Applied Physics
New Journal of Chemistry | Year: 2014

Strong blue luminescence and water-soluble nitrogen (N) and sulfur (S) co-doped graphene quantum dots (NS-GQDs) were fabricated via a one-step hydrothermal method using oxidized graphene. Ammonia and powdered S were selected as the source of N and S, respectively. The results indicated that both N and S atoms were successfully incorporated into the sp2-hybridized carbon framework of graphene. Under the excitation of 365 nm, the maximum emission intensity could be obtained with a 1 : 1.2 atomic ratio of N/S. The as-prepared NS-GQDs exhibited brighter luminescence compared with N-doped graphene quantum dots (N-GQDs). S-doping plays an important role in enhancing the emission intensity of NS-GQDs. In addition, the luminescence was exceptionally resistant to high salt concentration. Because of these virtues, there are extensive potential applications for NS-GQDs in bio-imaging, solar cells, and ion detection. © the Partner Organisations 2014.

Duan H.,Massachusetts Institute of Technology | Duan H.,Lanzhou University | Yang J.K.W.,Institute of Materials Research and Engineering of Singapore | Berggren K.K.,Massachusetts Institute of Technology
Small | Year: 2011

Capillary-force-induced collapse of high-aspect-ratio (HAR) micro- and nanostructures is common in the evaporation-drying process and a number of applications based on the collapse have been proposed. However, the collapse of small HAR structures is usually uncontrollable, which has prevented it from being used in engineering applications. Here, the collapse of 10-nm-scale structures is separately controlled through engineering an asymmetric cross section, curvature, and tilt in the structures prior to collapse. It is shown that this deterministic-collapse approach can be used to create linear structures from collapsed pillars and planar rectangular structures from collapsed fencelike linear structures, and can further be used to create small gaps by controlling the collapse of nearby structures. These techniques could be used to improve the performance of beam-based lithography methods for certain types of patterns by increasing throughput and resolution, reducing the proximity effect, and reducing irradiation damage. In addition, this controlled-collapse concept provides a possible platform with which to study mechanical behavior at the 10-nm scale. Random collapse is a common phenomenon in high-aspect-ratio (HAR) nanostructures. Methods to control such collapse by using capillary force during the evaporation-drying process are proposed. Controlled collapse is realized by introducing a slightly asymmetric cross section, curvature, and tilt to the nanostructures. With this technique, sub- 10-nm-gap arrays are fabricated from HAR structures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Feng S.,Lanzhou University | Feng S.,University of Nebraska - Lincoln | Feng S.,University of Arkansas | Fu Q.,Lanzhou University | Fu Q.,University of Washington
Atmospheric Chemistry and Physics | Year: 2013

Global drylands encompassing hyper-arid, arid, semiarid, and dry subhumid areas cover about 41 percent of the earth's terrestrial surface and are home to more than a third of the world's population. By analyzing observations for 1948-2008 and climate model simulations for 1948-2100, we show that global drylands have expanded in the last sixty years and will continue to expand in the 21st∼century. By the end of this century, the world's drylands (under a high greenhouse gas emission scenario) are projected to be 5.8 × 106 km2 (or 10%) larger than in the 1961-1990 climatology. The major expansion of arid regions will occur over southwest North America, the northern fringe of Africa, southern Africa, and Australia, while major expansions of semiarid regions will occur over the north side of the Mediterranean, southern Africa, and North and South America. The global dryland expansions will increase the population affected by water scarcity and land degradations. © Author(s) 2013.

Saunders R.W.,University of Leeds | Dhomse S.,University of Leeds | Tian W.S.,Lanzhou University | Chipperfield M.P.,University of Leeds | Plane J.M.C.,University of Leeds
Atmospheric Chemistry and Physics | Year: 2012

Nano-sized meteoric smoke particles (MSPs) with iron-magnesium silicate compositions, formed in the upper mesosphere as a result of meteoric ablation, may remove sulphuric acid from the gas-phase above 40 km and may also affect the composition and behaviour of supercooled H 2SO 4-H 2O droplets in the global stratospheric aerosol (Junge) layer. This study describes a time-resolved spectroscopic analysis of the evolution of the ferric (Fe 3+) ion originating from amorphous ferrous (Fe 2+)-based silicate powders dissolved in varying Wt % sulphuric acid (30-75 %) solutions over a temperature range of 223-295 K. Complete dissolution of the particles was observed under all conditions. The first-order rate coefficient for dissolution decreases at higher Wt % and lower temperature, which is consistent with the increased solution viscosity limiting diffusion of H 2SO 4 to the particle surfaces. Dissolution under stratospheric conditions should take less than a week, and is much faster than the dissolution of crystalline Fe 2+ compounds. The chemistry climate model UMSLIMCAT (based on the UKMO I Unified Model) was then used to study the transport of MSPs through the middle atmosphere. A series of model experiments were performed with different uptake coefficients. Setting the concentration of 1.5 nm radius MSPs at 80 km to 3000 cm -3 (based on rocket-borne charged particle measurements), the model matches the reported Wt % Fe values of 0.5-1.0 in Junge layer sulphate particles, and the MSP optical extinction between 40 and 75 km measured by a satellite-borne spectrometer, if the global meteoric input rate is about 20 tonnes per day. The model indicates that an uptake coefficient 0.01 is required to account for the observed two orders of magnitude depletion of H 2SO 4 vapour above 40 km. © 2012 Author(s).

Cheon H.,Cleveland Clinic | Yang J.,Cleveland Clinic | Yang J.,Lanzhou University | Stark G.R.,Cleveland Clinic
Journal of Interferon and Cytokine Research | Year: 2011

The signal transducers and activators of transcription (STAT)1 and STAT3 genes are specifically activated by phosphorylated STATs 1 and 3, respectively, resulting in large and prolonged increases in the levels of unphosphorylated STATs (U-STATs) in response to interferons (for STAT1) or ligands that activate gp130, such as IL-6 (for STAT3). U-STATs 1 and 3 are transcription factors that drive gene expression by mechanisms distinct from those used by phosphorylated STATs. U-STAT3 drives expression of many proteins not induced by phospho-STAT3, including several that are important in tumorigenesis. U-STAT1 prolongs and increases expression of a subset of proteins induced initially in response to phospho-STAT1, leading to antiviral and immune responses that are long-lived. U-STAT1 levels are also high in some cancers, and the protein products of genes induced by U-STAT1 enhance resistance to DNA damage. Therefore, interferons not only drive short-term expression of proteins that inhibit growth and promote apoptosis and immune surveillance, but also promote long-term expression of proteins that facilitate tumor survival. © Copyright 2011, Mary Ann Liebert, Inc. 2011.

Si M.S.,Indiana State University | Si M.S.,Lanzhou University | Zhang G.P.,Indiana State University
Journal of Physics Condensed Matter | Year: 2010

For nearly a decade, it has been a mystery why the small average number of photons absorbed per atom from an ultrashort laser pulse is able to induce a strong magnetization within a few hundred femtoseconds. Here we resolve this mystery by directly computing the number of photons per atom layer by layer as the light wave propagates inside the sample. We find that for all the 24 experiments considered here, each atom has more than one photon. The so-called photon shortage does not exist. By plotting the relative demagnetization change versus the number of photons absorbed per atom, we show that, depending on the experimental condition, 0.1 photon can induce about 4%-72% spin moment change. Our perturbation theory reveals that the demagnetization depends linearly on the amplitude of the laser field. In addition, we find that the transition frequency of a sample may also play a role in magnetization processes. As long as the intensity is not zero, the intensity of the laser field only affects the matching range of the transition frequencies, but not whether the demagnetization can happen or not. © 2010 IOP Publishing Ltd.

Che J.,Nanchang Institute of Technology | Wang J.,Lanzhou University | Tang Y.,Nanchang Institute of Technology
Applied Soft Computing Journal | Year: 2012

This paper presents an optimal training subset for support vector regression (SVR) under deregulated power, which has a distinct advantage over SVR based on the full training set, since it solves the problem of large sample memory complexity O(N 2) and prevents over-fitting during unbalanced data regression. To compute the proposed optimal training subset, an approximation convexity optimization framework is constructed through coupling a penalty term for the size of the optimal training subset to the mean absolute percentage error (MAPE) for the full training set prediction. Furthermore, a special method for finding the approximate solution of the optimization goal function is introduced, which enables us to extract maximum information from the full training set and increases the overall prediction accuracy. The applicability and superiority of the presented algorithm are shown by the half-hourly electric load data (48 data points per day) experiments in New South Wales under three different sample sizes. Especially, the benefit of the developed methods for large data sets is demonstrated by the significantly less CPU running time. © 2012 Elsevier B.V. All rights reserved.

Yang X.,General Hospital of Lanzhou | Li X.,Lanzhou University | Ren J.,Lanzhou University | Ren J.,Evergreen Wellness Center
Anti-Cancer Agents in Medicinal Chemistry | Year: 2014

Resveratrol (3, 5, 4'-trihydroxy-trans-stilbene, RVT), a stilbenoid, polyphenol phytochemical present in berries, grape, peanuts and wine. It has been suggested as a major contributor to "French Paradox" that reduces the mortality from coronary heart disease (CHD) by consuming RVT in red wine even in some of French population with a high-fat intake. With extensive research, it has been found that RVT is a versatile and pleiotropic agent, it not only possesses cardiovascular-protective benefits by its powerful antioxidant capacity, anti-inflammatory, regulating metabolism and anti-aging effects, but also has strong anti-tumor activities through inhibiting tumor cell proliferation, inducing cell apoptosis, promoting tumor cell differentiation, preventing tumor invasion and metastasis, and further moderating the host immune system to kill tumor cells. This review will focus on RVT's anti-tumor activity and tumor prevention potential including: the anti-tumor spectrum in vitro and in vivo; molecular targets and signal pathways involving RVT anti-tumor mechanisms; evidences from clinical trial for its bioavailability, dosage, toxicity and benefit in humans; and its prospective including its analog, deviations, and combinative chemotherapy. © 2014 Bentham Science Publishers.

Jin H.,Lanzhou University | Jin H.,Texas A&M University | Nasiri S.L.,Texas A&M University
Journal of Applied Meteorology and Climatology | Year: 2014

Atmospheric Infrared Sounder (AIRS) infrared-based cloud-thermodynamic-phase retrievals are evaluated using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) cloud thermodynamic phase. The AIRS cloud phase is derived from spectral information contained within the 8-12-mm window, and CALIPSO provides coincident pixel-scale observations of cloud phase using the depolarization capability of the 532-nm channel. Comparisons are performed between the AIRS and CALIPSO cloud-phase observations for single-layer (48.5% of all clouds), heterogeneous-layer (45.9%), and multilayered (5.6%) clouds. The AIRS ice phase is in agreement with CALIPSO for more than 90% of coincident observations globally, with the largest discrepancies found in high latitudes and multilayered clouds. AIRS water phase generally follows CALIPSO spatial patterns, but the frequency is lower by about a factor of 2. The ice and water phases of AIRS both show misclassifications about1%of the time when compared with CALIPSO. Not all clouds demonstrate strong phase signatures in the AIRS spectrum, which leads AIRS to classify unknown phase to around 10% of CALIPSO's ice clouds and 60% of CALIPSO's water clouds. This study shows that the algorithm is capable of detecting ice clouds within the AIRS field of view and can be used as the first step in further retrievals of ice-cloud optical thickness and effective particle size. © 2014 American Meteorological Society.

Mao Z.,CAS Dalian Institute of Chemical Physics | Wang Z.,Lanzhou University | Xu Z.,CAS Dalian Institute of Chemical Physics | Xu Z.,Lanzhou University | And 3 more authors.
Organic Letters | Year: 2012

Cu(OAc)2-mediated dehydrogenative cross-coupling between two heteroarenes has been realized in the absence of any other additive. A mechanism involving a formal Cu(II) to Cu(0) route by convergent disproportionation of the copper mediator is proposed and has been evidenced by copper mirror formation during the reaction. This synthetic protocol provides a concise and "green" access to unsymmetrical biheteroarenes bearing structural motifs of substantial utility in organic synthesis. © 2012 American Chemical Society.

Zhang H.,Lanzhou University | Gilbert B.,University of Toronto | Zhang X.,Lanzhou University | Zhou S.,Lanzhou University
Oikos | Year: 2013

Community assembly is a dynamic progression that reflects the interaction of several processes functioning at multiple scales. Understanding how these processes work in communities at different successional stages is important for identifying when regional or local processes are more important for community assembly, and for developing effective preservation and restoration strategies. We examined community assembly using a chronosequence of sub-alpine meadows in Qinghai-Tibetan Plateau that range from 'natural' (never farmed), to those that have been protected from agricultural exploitation for 1 to 10 years. We tested for shifts in species and traits among meadows and also for changes in environmental and spatial correlates of species distributions within meadows. We found that species richness increased and species composition returned to natural conditions within ten years of protection. These changes coincided with shifts in species traits; abundant species had high seed mass and specific leaf area in late-successional meadows, whereas the opposite occurred in early-successional meadows. Despite these shifts among meadows of different ages, spatial distributions of species within meadows did not change - when associated with abiotic variables, these spatial patterns reflected changes in soil pH and nitrogen. There was also no consistent change in the relative importance of environmental and spatial correlates of species distributions within meadows. These trends indicate that local processes of community assembly are similar within meadows even when species in those meadows differ. We conclude that successional change is a large-scale process that alters the species pool and resulting suite of traits that are present within meadows. As a result, regional planning that incorporates successional age should be the focus for the conservation of diversity in this area. In contrast, local processes work within the constraints of the species pool set by successional age, producing consistent patterns within meadows of different ages. © 2012 The Authors. Oikos © 2012 Nordic Society Oikos.

Mao Z.,Lanzhou University | Mao Z.,CAS Dalian Institute of Chemical Physics | Jia Y.,Lanzhou University | Xu Z.,CAS Dalian Institute of Chemical Physics | Wang R.,Lanzhou University
Advanced Synthesis and Catalysis | Year: 2012

The highly diastereo- and enantioselective relay cascade Michael/Michael/Henry reaction catalyzed by combination of readily available diphenylprolinol silyl ether and the quinine thiourea in a one-pot fashion has been developed. Up to 70% yield and up to >99% enantioselectivity of the single major isomer were obtained from the cascade reactions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bao X.,Lanzhou University | Zhang H.,Lanzhou University | Royer G.,Ecole des Mines de Nantes | Li J.,Lanzhou University | Li J.,CAS Lanzhou Institute of Modern Physics
Nuclear Physics A | Year: 2014

A systematic calculation of α decay half-lives is presented for even-even nuclei between Te and Z = 118 isotopes. The potential energy governing α decay has been determined within a liquid drop model including proximity effects between the α particle and the daughter nucleus and taking into account the experimental Q value. The α decay half-lives have been deduced from the WKB barrier penetration probability. The α decay half-lives obtained agree reasonably well with the experimental data. © 2013.

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.

Xu H.,Northwest University, China | Xu H.,Lanzhou University | Fan L.-L.,Northwest University, China
European Journal of Medicinal Chemistry | Year: 2011

A series of novel indole[1,2-c]-1,2,4-benzotriazine derivatives were obtained by a modified Sandmeyer reaction in the presence of tert-butylnitrite (t-BuONO). As compared with hymexazol, a commercially available agricultural fungicide, at the concentration of 50 μg/mL, two indole[1,2-c]-1,2,4- benzotriazines, 5h and 5k, exhibited the more promising and pronounced antifungal activities in vitro against five phytopathogenic fungi. It clearly demonstrated that introduction of appropriate substituents on the indolyl ring of indole[1,2-c]-1,2,4-benzotriazine (5a) would lead to the more potent derivatives.

Zhou Y.-C.,Lanzhou University | Zhang H.-L.,Lanzhou University | Deng W.-Q.,CAS Dalian Institute of Chemical Physics
Nanotechnology | Year: 2013

Doping a graphene sheet with different atoms is a promising method for tuning its electronic properties. We report a first-principle investigation on the electronic properties of N, B, S, Al, Si or P doped graphene. It is revealed that the doped graphene can show an interesting physical regularity, which can be described by a simple 3N rule: a doped graphene has a zero gap or a neglectable gap at the Dirac point when its primitive cell is 3N × 3N (N is an integer), otherwise there is a gap tunable by the dopant concentration. This unique 3N rule provides a useful guideline for the design of doped graphene for electronic applications. © 2013 IOP Publishing Ltd.

Mao Z.,CAS Dalian Institute of Chemical Physics | Huang F.,CAS Dalian Institute of Chemical Physics | Yu H.,Anshan Normal University | Chen J.,CAS Dalian Institute of Chemical Physics | And 3 more authors.
Chemistry - A European Journal | Year: 2014

The functionalization of internal olefins has been a challenging task in organic synthesis. Efficient CuII-catalyzed trifluoromethylation of internal olefins, that is, α-oxoketene dithioacetals, has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent. The push-pull effect from the polarized olefin substrates facilitates the internal olefinic C-H trifluoromethylation. Cyclic and acyclic dithioalkyl α-oxoketene acetals were used as the substrates and various substituents were tolerated. The internal olefinic C-H bond cleavage was not involved in the rate-determining step, and a mechanism that involves radicals is proposed based on a TEMPO-quenching experiment of the trifluoromethylation reaction. Further derivatization of the resultant CF 3 olefins led to multifunctionalized tetrasubstituted CF3 olefins and trifluoromethylated N-heterocycles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhou W.-C.,Lanzhou University | Zhang Q.-B.,Fudan University | Qiao L.,University of Sydney
World Journal of Gastroenterology | Year: 2014

Liver cirrhosis is the final pathological result of various chronic liver diseases, and fibrosis is the precursor of cirrhosis. Many types of cells, cytokines and miRNAs are involved in the initiation and progression of liver fibrosis and cirrhosis. Activation of hepatic stellate cells (HSCs) is a pivotal event in fibrosis. Defenestration and capillarization of liver sinusoidal endothelial cells are major contributing factors to hepatic dysfunction in liver cirrhosis. Activated Kupffer cells destroy hepatocytes and stimulate the activation of HSCs. Repeated cycles of apoptosis and regeneration of hepatocytes contribute to pathogenesis of cirrhosis. At the molecular level, many cytokines are involved in mediation of signaling pathways that regulate activation of HSCs and fibrogenesis. Recently, miRNAs as a post-transcriptional regulator have been found to play a key role in fibrosis and cirrhosis. Robust animal models of liver fibrosis and cirrhosis, as well as the recently identified critical cellular and molecular factors involved in the development of liver fibrosis and cirrhosis will facilitate the development of more effective therapeutic approaches for these conditions. © 2014 Baishideng Publishing Group Inc. All rights reserved.

Zhang X.,Northwest University, China | Cao Y.,Northwest University, China | Yu S.,Northwest University, China | Yang F.,Northwest University, China | Xi P.,Lanzhou University
Biosensors and Bioelectronics | Year: 2013

Carbon-supported PdNi nanoparticles (PdNi/C) were synthesized using a novel synthetic route, and characterized by transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The overall metallic content (Pd+Ni) was 10% (w/w) and uniformly distributed in the carbon black (90%) matrix. The electrocatalytic performance of the PdNi/C modified glassy carbon electrode (GCE) was investigated for ascorbic acid (AA) oxidation, and showed better catalytic activity than an equal amount of commercially available palladium carbon catalyst. The oxidation potential of AA was negatively shifted to -0.05V. The biosensor tolerated a wide linear concentration range for AA, from 1.0×10-5M to 1.8×10-3M (R=0.9973), with a detection limit of 0.5μM (S/N=3). Our results demonstrate that PdNi/C nanomaterials have excellent AA sensing capability, including a fast response time, high reproducibility and stability, with great promise in the quantification of AA in real samples. These qualities make the Pd-based bimetallic catalysts promising candidates for amperometric sensing. © 2013 Elsevier B.V.

Xu H.,Northwest University, China | Xu H.,Lanzhou University | Fan L.-L.,Northwest University, China
European Journal of Medicinal Chemistry | Year: 2011

A series of new 5,6-dihydro-indolo[1,2-a]quinoxaline derivatives has been prepared in moderate to excellent yields from 2-(indol-1-yl)phenylamines with aromatic aldehydes by an efficient and economical iron-catalyzed Pictet-Spengler reaction. Meanwhile, as compared with hymexazol, a commercially available agricultural fungicide at the concentration of 50 μg/mL, some 5,6-dihydro-indolo[1,2-a]quinoxalines exhibited promising antifungal activities in vitro against the phytopathogenic fungi, and might be considered as novel promising lead candidates for further design and synthesis of agricultural fungicides. © 2011 Elsevier Masson SAS. All rights reserved.

Zhao J.,Northwest University, China | Yang D.,Northwest University, China | Zhao Y.,Northwest University, China | Yang X.-J.,Northwest University, China | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2014

A tetrakis(bisurea)-decorated tetraphenylethene (TPE) ligand (L 2) was designed, which, upon coordination with phosphate ions, displays fluorescence "turn-on" over a wide concentration range, from dilute to concentrated solutions and to the solid state. The fluorescence enhancement can be attributed to the restriction of the intramolecular rotation of TPE by anion coordination. The crystal structure of the A4L 2 (A=anion) complex of L2 with monohydrogen phosphate provides direct evidence for the coordination mode of the anion. This "anion-coordination-induced emission" (ACIE) is another approach for fluorescence turn-on in addition to aggregation-induced emission (AIE). Phosphate ions in a bind: The tetrakis(bisurea)-decorated tetraphenylethene (TPE) displays fluorescence "turn-on" over a wide concentration range upon phosphate coordination. The fluorescence enhancement can be attributed to the restriction of the intramolecular rotation of TPE by anion coordination. This "anion-coordination-induced emission" (ACIE) is another approach for fluorescence turn-on. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Duan J.-W.,Lanzhou University | Hu G.,Soochow University of China | Qiu W.-Y.,Lanzhou University
Match | Year: 2014

DNA cages are kind of artificial polyhedra that are interlinked and interlocked with DNA double-strands. A simple formula to calculate genus of DNA cages is presented here. The formula connects some topological properties of DNA cages, including component number μ, crossing number c and Seifert circle number s. It shows that no matter the way of DNA strands interlinked, the genus is a constant which only depends on the component number of the underlying polyhedral graph. Our study demonstrates that, the genus is an essential topological aspect of DNA polyhedra, which provides a novel classification and a design principle for DNA cages.

Wang X.,Lanzhou University | Doherty S.J.,University of Washington | Huang J.,Lanzhou University
Journal of Geophysical Research: Atmospheres | Year: 2013

Black carbon (BC), organic carbon (OC), and mineral dust (MD) are the most important light-absorbing particulate impurities in snow. A field campaign was conducted in January and February 2010 to measure light-absorbing particles in snow across northern China. About 400 snow samples were collected at 46 sites in six provinces. A spectrophotometer was used to separate snow particulate absorption by BC and non-BC constituents, based on the different spectral dependences of their light absorption. Light absorption by MD is due to iron oxides, so iron concentration was determined by chemical analysis. Using assumed mass absorption efficiencies for BC, OC, and iron, the fractional contribution of each to total absorption was estimated. BC is a product of combustion and iron is associated with MD, but OC in snow can be associated with either combustion products deposited to snow or from soil mixed into snow. The lowest concentrations of BC were in the remote northeast on the border of Siberia, with a median concentration in surface snow of 117 ng g-1. South of this, in the industrial northeast, the median snow BC concentration was 1220 ng g-1. In the northeast, snow particulate light absorption was dominated by BC. Across the grassland of Inner Mongolia, OC, likely mostly from local soil, dominates light absorption, with median BC concentrations of 340 ng g-1 responsible for only about one third of total particulate light absorption. In the Qilian Mountains, at the northern boundary of the Tibetan Plateau, snow particulate light absorption is dominated by local soil and desert dust. ©2012. American Geophysical Union. All Rights Reserved.

Lin P.,University of Washington | Fu Q.,University of Washington | Fu Q.,Lanzhou University
Journal of Geophysical Research: Atmospheres | Year: 2013

We analyzed the changes of simulated Brewer-Dobson circulation (BDC) for 1960-2099 from 12 chemistry climate models participating the Chemistry-Climate Model Validation activity phase 2 (CCMVal-2). We decomposed the BDC into transition, shallow, and deep branches with vertical extent of 100-70, 70-30, and above 30 hPa, respectively. Models consistently simulate the acceleration in all three BDC branches over 140 years, but the acceleration rate of the deep branches is much smaller. The acceleration rate of the transition and shallow branches in general shows weak seasonal or hemispheric dependence and increases with time, consistent with the continuous and homogeneous increase of greenhouse gas concentrations. The trend magnitudes of shallow and transition branches differ from model to model, which are found to be associated with the simulated changes in subtropical jets and tropical upper tropospheric temperature. The acceleration of the deep branch is also a response to the increase of greenhouse gas concentrations but is modulated by the changes in ozone concentrations. The effect of ozone changes is particularly prominent in the southern deep branch during austral summer: almost all models simulated strong significant acceleration during the ozone depletion era, weak deceleration during the ozone recovery era, and near-zero trends during the stable ozone era. However, the ozone effect is less evident in other seasons and in other branches. © 2012 American Geophysical Union. All Rights Reserved.

Ren W.,Soochow University of China | Liu J.,Soochow University of China | Chen L.,Soochow University of China | Wan X.,Soochow University of China | Wan X.,Lanzhou University
Advanced Synthesis and Catalysis | Year: 2010

Using a catalytic system of the (cymene)ruthenium dichloride dimer, [Ru(cymene)Cl2]2, (0.001 mol%) and iodine (10 mol%), a variety of alkynes bearing different functional groups were oxidized with tert-butyl hydroperoxide (TBHP; 70% solution in water) under mild conditions to give 1,2diketones in good to excellent yields. Two noteworthy features of the method are the extremely high catalyst productivity (TON up to 420,000) and scale-up to 1 mol. Preliminary mechanism investigations showed that iodonium ion and water were involved in the transformation. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gao F.,Lanzhou University | Liao Q.,CAS Beijing National Laboratory for Molecular | Xu Z.-Z.,Lanzhou University | Yue Y.-H.,Lanzhou University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2010

Low In, high out: Single crystals of a thiomethyl-terminated oligo(phenylene vinylene) exhibit unique photonic properties including strong anisotropic solidstate fluorescence (see depicted optical and fluorescence micrographs; arrows: polarization direction), high quantum yield, large two-photon absorption cross section, and stimulated emission, which make it a candidate for opto-electronic applications such as upconversion lasing. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Zhang F.,Henan University | Liu B.,Lanzhou University
Journal of Alloys and Compounds | Year: 2012

The red-emitting phosphors Ca 3Gd 7(SiO 4) 5(PO 4)O 2:Eu 3+ were synthesized and their photoluminescence properties under near-ultraviolet (NUV) light excitation were investigated. The results indicate that Ca 3Gd 7(SiO 4) 5(PO 4)O 2:Eu 3+ can be effectively excited by 393 nm which matches with the emission wavelength of NUV chips for white light emitting diodes (LED). These phosphors present an intensity red emission with maximum at 614 nm. Among them, the optimal sample has high emission intensity and exhibits small thermal-quenching property, which indicates that it can be potentially applied in NUV InGaN-based LEDs. © 2012 Elsevier B.V. All rights reserved.

Sun Y.,Lanzhou University | Wang A.,Ludong University | Wan D.,Lanzhou University | Wang Q.,Lanzhou University | Liu J.,Lanzhou University
Molecular Phylogenetics and Evolution | Year: 2012

In this study, we examined diversification history of Rheum and tested the hypothesis that morphological traits related to plant 'body-plans' evolved in parallel in this genus. We sequenced eight chloroplast DNA fragments (representing more than 8000. bps of the sequence for each species) of 34 species from the genus and 13 species from closely related genera. Phylogenetic analyses indicate that all species of Rheum form a monophyletic lineage sister to the two-species genus Oxyria, indicating that radiative diversifications have occurred in its evolutionary history. Our dating analyses further suggest that these radiations largely coincided with the extensive uplifts of the Qinghai-Tibetan Plateau (QTP). Ancestral state reconstruction and likelihood sensitivity tests strongly indicate that both decumbent and 'glasshouse-like' body-plan traits evolved in parallel in different clades. Our findings highlight the importance of the uplift of the QTP in promoting species diversification and the parallel evolution of morphological traits that are putatively adaptive during such an evolutionary history. © 2012 Elsevier Inc.

Zhang G.,Nanjing University of Science and Technology | Zhang G.,Lanzhou University | Ma Y.,Lanzhou University | Cheng G.,Nanjing University of Science and Technology | And 2 more authors.
Organic Letters | Year: 2014

A novel combined metal-free "CN" source from trimethylsilyl azide and 1,2-dichloroethane has been developed and successfully applied to copper-catalyzed oxidative cyanation of α-C-H tertiary amines for the synthesis of C1-cyanation tetrahydroisoquinoline derivatives with good to excellent yields for the first time. © 2014 American Chemical Society.

Sun Y.,Lanzhou University | Liu X.,Lanzhou University | Matsuki T.,Tokyo Kasei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

In this work, we study the newly observed DJ(3000) and DJ*(3000) through the analysis of mass spectrum and calculation of the corresponding two-body strong decay behaviors. Our results show that D J(3000) and DJ*(3000) are explained as the 2P(1+) and 2P03 states in the D meson family, respectively, which is supported by the calculated masses of these two states and their decay behaviors. As a byproduct, the decay behaviors of 3S01, 3S13, 2D(2-), 2D13, 2D ′(2-), 2D33, 2P′(1+), 2P23, 1F(3+), 1F23, 1F′(3+), and 1F43 states are also given, which will be helpful to further experimentally study mixings of these D mesons, too. © 2013 American Physical Society.

Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Lanzhou Institute of Modern Physics | Liu X.,Lanzhou University | Matsuki T.,Tokyo Kasei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Being stimulated by the recent BESIII observation of a charged charmoniumlike structure Zc(3900), in this work we study the distributions of the J/ψπ± and π+π - invariant mass spectra of the Y(4260) →π+π-J/ψ decay by the initial-single-pion- emission mechanism, where the interference effects of the initial-single-pion- emission mechanism with two other decay modes are also taken into account. The obtained dΓ(Y(4260)→π+π-J/ψ)/dm J/ψπ± and dΓ(Y(4260) →π+π-J/ψ)/dmπ +π- marvelously agree with the BESIII data to reproduce the Zc(3900) structure. © 2013 American Physical Society.

Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Lanzhou Institute of Modern Physics | Liu X.,Lanzhou University | Matsuki T.,Tokyo Kasei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Studying the hidden-charm dipion decays of the charmoniumlike state Y(4360), we show that there exist charged charmoniumlike structures near DD̄* and D*D̄* thresholds in the J/ψπ+, ψ(2S)π+, and hc(1P) π+ invariant mass spectra of the corresponding hidden-charm dipion decays of Y(4360) using the initial single pion emission mechanism. We suggest further experimental study on these predicted charged enhancement structures, especially by BESIII, Belle, and the forthcoming BelleII. © 2013 American Physical Society.

Zhang J.,Lanzhou University | Zhang J.,University of Cologne | Shao Y.,University of Cologne | Huang N.,Lanzhou University
Atmospheric Chemistry and Physics | Year: 2014

In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from PDA (particle dynamics analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and thus the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure dust deposition velocities for different particle sizes, wind speeds and surface conditions. For sticky-smooth wood and water surfaces, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire data set is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable data set of dust deposition velocities is obtained, which is valuable for the development and validation of dust deposition schemes. © 2014 Author(s).

Liu J.-W.,Lanzhou University | Yang Y.,CAS Beijing National Laboratory for Molecular | Chen C.-F.,CAS Beijing National Laboratory for Molecular | Ma J.-T.,Lanzhou University
Langmuir | Year: 2010

Two novel low-molecular-weight organogelators (LMOGs) 1 and 2 composed of an anthraquinone unit, a hydrazide group, and long alkyl chains were synthesized. They could form stable gels in wide tested solvents. Chloroalkanes and aromatic solvents tend, to result in transparent gels, while alcohol and other solvents yield opaque gels. The FT-IR, PXRD, and 1H NMR spectral studies revealed that hydrogen bonding and π-π interactions were the main driving forces for formation of the gels. Although the hydrazide unit and the anthraquinone group were connected by the σ-bond, the chloroform gel. of 1 could be changed into a red solution upon the addition of anion (F-, AcO-, and H2PO4 -) due to the disruption of the intermolecular hydrogen-bondings. Moreover, the red color clearly faded at once and the solution regelated upon the addition of methanol. The results indicated that 1 and 2 as smart anion-responsive gel might provide the basis for the development of nonfluid systems for sensing anion with the naked eye. © 2010 American Chemical Society.

Thorsen T.J.,University of Washington | Fu Q.,University of Washington | Fu Q.,Lanzhou University
Journal of Atmospheric and Oceanic Technology | Year: 2015

A feature detection and extinction retrieval (FEX) algorithm for the Atmospheric Radiation Measurement Program's (ARM) Raman lidar (RL) has been developed. Presented here is Part II of the FEX algorithm: the retrieval of cloud and aerosol extinction profiles. The directly retrieved extinction profiles using the Raman method are supplemented by other retrieval methods developed for elastic backscatter lidars. Portions of features where the extinction-to-backscatter ratios (i.e., lidar ratios) can be obtained are used to infer the lidar ratios for the regions where no such estimate can be made. When neither directly retrieved nor an inferred value can be determined, a climatological lidar ratio is used. This best-estimate approach results in the need to use climatological lidar ratios for less than about 5% of features, except for thin cirrus at the ARM tropical western Pacific Darwin site, where above 12 km, about 20% of clouds use a climatological lidar ratio. A classification of feature type is made, guided by the atmosphere's thermodynamic state and the feature's scattering properties: lidar ratio, backscatter, and depolarization. The contribution of multiple scattering is explicitly considered for each of the ARM RL channels. A comparison between aerosol optical depth from FEX and that from collocated sun photometers over multiple years at two ARM sites shows an agreement (in terms of bias error) of about -0.3% to -4.3% (relative to the sun photometer). © 2015 American Meteorological Society.

Zhang R.,Lanzhou University | Hegg D.A.,University of Washington | Huang J.,Lanzhou University | Fu Q.,Lanzhou University | Fu Q.,University of Washington
Atmospheric Chemistry and Physics | Year: 2013

Seasonal snow samples obtained at 46 sites in 6 provinces of China in January and February 2010 were analyzed for a suite of chemical species and these data are combined with previously determined concentrations of insoluble light-absorbing particles (ILAP), including all particles that absorb light in the 650-700 nm wavelength interval. The ILAP, together with 14 other analytes, are used as input to a positive matrix factorization (PMF) receptor model to explore the sources of ILAP in the snow. The PMF analysis for ILAP sources is augmented with backward trajectory cluster analysis and the geographic locations of major source areas for the three source types. The two analyses are consistent and indicate that three factors/sources were responsible for the measured light absorption of snow: a soil dust source, an industrial pollution source, and a biomass and/or biofuel burning source. Soil dust was the main source of the ILAP, accounting for ∼53% of ILAP on average. © 2013 Author(s).

Li L.-L.,Nanjing University | Liu K.-P.,Nanjing University | Liu K.-P.,Lanzhou University | Yang G.-H.,Nanjing University | And 3 more authors.
Advanced Functional Materials | Year: 2011

A novel strategy is reported for the fabrication of poly(diallyldimethylammonium chloride) (PDDA)-protected graphene-CdSe (P-GR-CdSe) composites. An advanced electrogenerated chemiluminescence (ECL) immunosensor is proposed for the sensitive detection of human IgG (HIgG) by using the as-prepared P-GR-CdSe composites. The P-GR-CdSe composite film shows high ECL intensity, good electronic conductivity, fast response, and satisfactory stability, all of which holds great promise for the fabrication of ECL biosensors with improved sensitivity. After two successive steps of amplification via the conjugation of PDDA and gold nanoparticles (GNPs) in the film, high ECL intensity is observed. The ECL immunosensor has an extremely sensitive response to HIgG in a linear range of 0.02-2000 pg mL-1 with a detection limit of 0.005 pg mL-1. The proposed sensor exhibits high specificity, good reproducibility, and long-term stability, and may become a promising technique for protein detection. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xu Z.,CAS Beijing National Laboratory for Molecular | Xu Z.,University of Chinese Academy of Sciences | Liao Q.,CAS Beijing National Laboratory for Molecular | Shi Q.,CAS Beijing National Laboratory for Molecular | And 3 more authors.
Advanced Materials | Year: 2012

Low-threshold nanolasers based on slab nanocrystals (SNCs) of highly emissive H-aggregated organic semiconductors are reported. A lasing threshold as low as 100 nJ cm-2 is achieved in a high-quality (cavity quality factor â1000) Fabry-Pérot cavity constituted by the two lateral-faces of SNCs at the wavelength scale. Moreover, the laser light generated in the ultrasmall radial cavity of SNCs can propagate along its length up to hundreds of micrometers, making them attractive building blocks for miniaturized photonic circuits. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xingcai L.,Ningxia University | Xingcai L.,Lanzhou University | Beidou Z.,Lanzhou University
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2013

This paper presents a charged coated sphere model to discuss the effect of an inhomogeneous dust particle on the propagation of the electromagnetic wave. The calculated results show that the extinction efficiency increases with the increase in surface charge density (and the increase in charge-mass ratio); and it first increases then decreases with the increase of the charge distributed angle, and a maximum value appeared when the charge distributed angle is 110°. In addition, when the core is the scattering medium and the shell is the absorbing medium, its attenuation efficiency is larger when the core is the absorbing medium but the shell is the scattering medium; and with the increase of the geometry size ratio of the particle's core-shell, the extinction efficiency of the former decreases but that of the latter increases. © 2013 Elsevier Ltd.

Chen D.-Y.,Lanzhou University | Chen D.-Y.,CAS Lanzhou Institute of Modern Physics | Liu X.,Lanzhou University | Matsuki T.,Tokyo Kasei University
Physical Review Letters | Year: 2013

We propose the initial single chiral particle emission mechanism, with which the hidden-charm dikaon decays of higher charmonia and charmoniumlike states are studied. Calculating the distributions of differential decay width, we obtain the line shape of the J/ψK+ invariant mass spectrum of ψi→J/ψK+K-, where ψi=ψ(4415), Y(4660), and ψ(4790). Our numerical results show that there exist enhancement structures with both hidden-charm and open-strange channels, which are near the DD̄s*/D *D̄s and D*D̄s*/ D̄*Ds* thresholds. These charged charmoniumlike structures predicted in this Letter can be accessible in future experiments, especially BESIII, BelleII, and SuperB. © 2013 American Physical Society.

Liu J.-W.,CAS Institute of Chemistry | Liu J.-W.,Lanzhou University | Ma J.-T.,Lanzhou University | Chen C.-F.,CAS Institute of Chemistry
Tetrahedron | Year: 2011

A new class of efficient low-molecular-weight gelators composed of a 2-substituted anthraquinone and a hydrazide subunit were synthesized, and the structure-property relationships with respect to their gelation abilities in organic solvents were investigated. The toluene gels showed exceptional thermal stability. Interestingly, it was also found that the ultrasound radiation could promote 1b-e to form a stable organogels instead of precipitates in polar solvent, and the ultrasound could remarkably induce changes of the morphology of the assembly in pyridine. Moreover, the reversible gel to sol phase transition could be achieved by adding TFA and TEA. The gelators 1b-e further showed selective gelation of aromatic solvents or chloroalkanes from their mixtures with water. © 2010 Elsevier Ltd. All rights reserved.

Liu Z.,Soochow University of China | Zhang J.,Soochow University of China | Chen S.,Soochow University of China | Shi E.,Soochow University of China | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2012

A radical solution: A Bu 4NI/tert-butyl hydroperoxide (TBHP) catalyzed synthesis of amides through a cross-coupling reaction between acyl and aminyl radicals is described. This method involves the combination of aldehyde C-H bond functionalization and decarbonylation of N,N-disubstituted formamides (see scheme). The cross-coupling is metal-free, has a wide substrate scope, operational simplicity, and gives high yields on scale-up. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cui N.,Lanzhou University | Wu W.,Lanzhou University | Zhao Y.,CAS Beijing National Laboratory for Molecular | Bai S.,Lanzhou University | And 3 more authors.
Nano Letters | Year: 2012

Nanogenerator has been a very important energy harvesting technology through directly deforming piezoelectric material. Here, we report a new magnetic force driven contactless nanogenerator (CLNG), which avoids the direct contact between nanogenerator and mechanical movement source. The CLNG can harvest the mechanical movement energy in a noncontact mode to generate electricity. Their output voltage and current can be as large as 3.2 V and 50 nA, respectively, which is large enough to power up a liquid crystal display. We also demonstrate a means by which a magnetic sensor can be built. © 2012 American Chemical Society.

Zhang H.F.,Lanzhou University | Royer G.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Li J.Q.,CAS Lanzhou Institute of Modern Physics
Physical Review C - Nuclear Physics | Year: 2011

A study of the assault frequency and preformation factor of the α-decay description is performed from the experimental α-decay constant and the penetration probabilities calculated from the generalized liquid-drop model (GLDM) potential barriers. To determine the assault frequency a quantum-mechanical method using a harmonic oscillator is introduced and leads to values of around 1021 s-1, similar to the ones calculated within the classical method. The preformation probability is around 10 -1-10-2. The results for even-even Po isotopes are discussed for illustration. While the assault frequency presents only a shallow minimum in the vicinity of the magic neutron number 126, the preformation factor and mainly the penetrability probability diminish strongly around N=126. © 2011 American Physical Society.

Chen S.,Soochow University of China | Xu Y.,Soochow University of China | Wan X.,Soochow University of China | Wan X.,Lanzhou University
Organic Letters | Year: 2011

A new N-sulfonyl formamidine synthesis was developed via NaI-catalyzed direct condensation of sulfonamide and formamide. The green methodology is featured by high atom economy, easily available starting materials, the lack of need for a transition-metal catalyst, no requirement of hazardous reagent, operational simplicity, and good tolerance with diverse functional groups. Mechanistic studies suggest that the protocol proceeds based upon in situ generated TsN•NaI. © 2011 American Chemical Society.

Liu K.,Nanjing University | Liu K.,Lanzhou University | Zhang J.-J.,Nanjing University | Wang C.,Lanzhou University | Zhu J.-J.,Nanjing University
Biosensors and Bioelectronics | Year: 2011

A sensitive electrochemical immunosensor with graphene-assisted signal amplification has been developed. In order to construct the base of the immunosensor, a novel hybrid architecture was initially fabricated by combining poly (diallyldimethylammonium chloride) functionalized graphene nanosheets (PDDA-G) and gold nanoparticles (AuNPs) via a simple sonication-induced assembly. The formed hybrid architecture provided an effective matrix for antibody immobilization with good stability and bioactivity. Subsequently, a smart, multilabel, and graphene-based nanoprobe that contains gold nanoparticles functionalized exfoliated graphene oxide and horseradish peroxidase-secondary antibodies was designed for constructing a novel sandwiched electrochemical immunosensor. Enhanced sensitivity was obtained by combining the advantages of high-binding capability and excellent electrical conductivity of hybrid architecture with the multilabel signal amplification. On the basis of the dual signal amplification strategy of graphene-based architecture and the multilabel, the immunosensor displayed excellent analytical performance for the detection of human IgG (HIgG) range from 0.1 to 200. ng/mL with a detection limit of 0.05. ng/mL at 3. σ. Moreover, the proposed method showed good precision, acceptable stability and reproducibility, and could be used for the detection of HIgG in real samples. Therefore, the present strategy definitely paves a way for the wide application of graphene in clinical research. © 2011 Elsevier B.V.

Liu K.,Nanjing University | Liu K.,Lanzhou University | Zhang J.-J.,Nanjing University | Cheng F.-F.,Nanjing University | And 3 more authors.
Journal of Materials Chemistry | Year: 2011

A green and facile method for the preparation of gelatin functionalized graphene nanosheets (gelatin-GNS) was reported by using gelatin as a reducing reagent. Meanwhile, the gelatin also played an important role as a functionalized reagent to prevent the aggregation of the graphene nanosheets. The obtained biocompatible gelatin-GNS exhibited excellent stability in water and various physiological fluids including, cellular growth media as well as serum which were critical prerequisites for biomedicine application of graphene. Cellular toxicity test suggested that the gelatin-GNS was nontoxic for MCF-7 cells, even at a high concentration of 200 μg mL-1. Furthermore, the anticancer drug was loaded onto the gelatin-GNS at a high loading capacity via physisorption for cellular imaging and drug delivery. The doxorubicin/gelatin-GNS composite exhibited a high toxicity to kill MCF-7 cells and experienced a gelatin-mediated sustained release in vitro, which has the potential advantage of increasing the therapeutic efficacy. Therefore, the gelatin-GNS could be selected as an ideal drug carrier to be applied in biomedicine studies. © The Royal Society of Chemistry 2011.

Fu Q.,University of Washington | Fu Q.,Lanzhou University | Lin P.,University of Washington
Journal of Climate | Year: 2011

One pronounced feature in observed latitudinal dependence of lower-stratospheric temperature trends is the enhanced cooling near 308 latitude in both hemispheres. The observed phenomenon has not, to date, been explained in the literature. This study shows that the enhanced cooling is a direct response of the lower-stratospheric temperature to the poleward shift of subtropical jets. Furthermore, this enhanced lower-stratospheric cooling can be used to quantify the poleward shift of subtropical jets. Using the lower-stratospheric temperatures observed by satellite-borne microwave sounding units, it is shown that the subtropical jets have shifted poleward by 0.6° ± 0.1° and 1.0° ± 0.3° latitude in the Southern and Northern Hemispheres, respectively, in last 30 years since 1979, indicating a widening of tropical belt by 1.6° ± 0.4° latitude. © 2011 American Meteorological Society.

Ma J.-X.,Lanzhou University | Ma J.-X.,Ningxia University | Huang X.-F.,Lanzhou University | Song X.-Q.,Lanzhou University | And 2 more authors.
Chemistry - A European Journal | Year: 2013

Framework-isomeric three-dimensional (3D) Cd-Ln heterometallic metal-organic frameworks (HMOFs), {[Ln2(ODA)6Cd 3(H2O)6]×6 H2O}n (Ln=Gd (1 a) and Tb (1 b), ODA=oxydiacetic acid) and {[Cd(H2O) 6]×[Ln2(ODA)6Cd2]×H 2O}n (Ln=Gd (2 a), Tb (2 b)), with neutral and anionic pores, respectively, were designed based on a lanthanide metalloligand strategy and synthesized by using a stepwise assembly and a hydrothermal method. Luminescence studies revealed that 1 b and 2 b can act as luminescent metal-organic frameworks and their light-emitting properties can be modulated by small guest molecules and the manganese counterion, respectively. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liu K.,Lanzhou University | Liu K.,Nanjing University | Zhang J.,Nanjing University | Yang G.,Nanjing University | And 2 more authors.
Electrochemistry Communications | Year: 2010

The functionalized graphene nanosheets (PDDA-G) with poly(diallyldimethylammonium chloride) (PDDA) were synthesized and used to combine with room temperature ionic liquid (RTIL). The resulting RTIL/PDDA-G composite displayed an enhanced capability for the immobilization of hemoglobin to realize its direct electrochemistry. Moreover, the RTIL/PDDA-G based biosensor exhibited excellent electrocatalytic activity for the detection of nitrate with a wide linear range from 0.2 to 32.6 μM and a low detection limit of 0.04 μM at 3σ. This work opens a new way to functionalized graphene nanosheets with good biocompatibility and solubility in biosensors. © 2010 Elsevier B.V. All rights reserved.

Po-Chedley S.,University of Washington | Fu Q.,University of Washington | Fu Q.,Lanzhou University
Environmental Research Letters | Year: 2012

Recent studies have examined tropical upper tropospheric warming by comparing coupled atmosphere-ocean global circulation model (GCM) simulations from Phase 3 of the Coupled Model Intercomparison Project (CMIP3) with satellite and radiosonde observations of warming in the tropical upper troposphere relative to the lower-middle troposphere. These studies showed that models tended to overestimate increases in static stability between the upper and lower-middle troposphere. We revisit this issue using atmospheric GCMs with prescribed historical sea surface temperatures (SSTs) and coupled atmosphere-ocean GCMs that participated in the latest model intercomparison project, CMIP5. It is demonstrated that even with historical SSTs as a boundary condition, most atmospheric models exhibit excessive tropical upper tropospheric warming relative to the lower-middle troposphere as compared with satellite-borne microwave sounding unit measurements. It is also shown that the results from CMIP5 coupled atmosphere-ocean GCMs are similar to findings from CMIP3 coupled GCMs. The apparent model-observational difference for tropical upper tropospheric warming represents an important problem, but it is not clear whether the difference is a result of common biases in GCMs, biases in observational datasets, or both. © 2012 IOP Publishing Ltd.

Sun Z.-F.,Lanzhou University | Yu J.-S.,Lanzhou University | Liu X.,Lanzhou University | Matsuki T.,Tokyo Kasei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We study three charmed resonances, D(2550), D(2610), and D(2760), newly observed by the BABAR Collaboration, utilizing the mass spectra and investigating the strong decays. Our calculation indicates that D(2610) is an admixture of 2S13 and 1D13 with JP=1⊃-. D(2760) can be explained as either the orthogonal partner of D(2610) or 1D33. Our estimate of the decay width for D(2550), assuming it as 2S01, is far below the experimental value. The decay behavior of the remaining two 1D charmed mesons, i.e., D23 and D21 (JP=2⊃-) states, is predicted, which will help future experimental search for these missing D-wave charmed mesons. © 2010 The American Physical Society.

Xu H.,Lanzhou University | Chen Y.,CAS Beijing National Laboratory for Molecular | Zhang J.,CAS Beijing National Laboratory for Molecular | Zhang H.,Lanzhou University
Small | Year: 2012

The hysteresis effect is a common problem in graphene field-effect transistors (FETs). Usually, the external doping to graphene is considered to be responsible for the hysteresis behavior, but is not yet clearly understood. By monitoring the doping of graphene and the hysteresis in graphene FETs under different atmospheres using in situ Raman spectroscopy, it is confirmed that the electrochemical doping of O2/H2O redox couple to graphene is responsible for the hysteresis effect. In addition, Raman spectra of graphene on SiO2 substrate show stronger doping than that suspended, which indicates that SiO2 substrate plays an important role in the doping of graphene. Herein it is proposed that the doping species (H 2O and O2) are bounded at the interface of graphene/SiO2 substrate by hydrogen-bonds with the silanol groups on SiO2 substrate. The dynamic equilibrium process of the charge-transfer between H2O/O2 redox couple and graphene under electrical field modulation is carefully analyzed using Marcus-Gerischer theory. This work provides a clear view to the mechanism of the hysteresis effect, and is of benefit to a reliable design to suppress the hysteresis in graphene FETs. Electrochemical doping of the O2/H2O redox couple to graphene occurring at the interface of graphene/SiO2 substrate is proven responsible for the origin of the hysteresis effect in graphene electrical field transistors. Marcus-Gerischer theory is used to explain the charge-transfer mechanism between the O2/H2O redox couple and graphene, and to analyze their dynamic equilibrium process under electrical field effect. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Huang A.,Leibniz University of Hanover | Dou W.,Lanzhou University | Caro J.,Leibniz University of Hanover
Journal of the American Chemical Society | Year: 2010

A novel covalent functionalization strategy was developed to prepare reproducible ZIF-90 molecular sieve membranes by using 3- aminopropyltriethoxysilane as a covalent linker between the ZIF-90 layer and Al2O3 support via imines condensation. The ZIF-90 membranes show high thermal and hydrothermal stabilities, and they allow the separation of hydrogen from larger gases by molecular sieving. © 2010 American Chemical Society.

Liu X.-H.,CAS Institute of Chemistry | Liu X.-H.,Chinese Academy of Sciences | Guan C.-Z.,CAS Institute of Chemistry | Guan C.-Z.,Chinese Academy of Sciences | And 5 more authors.
Journal of the American Chemical Society | Year: 2013

Surface covalent organic frameworks (SCOFs), featured by atomic thick sheet with covalently bonded organic building units, are promised to possess unique properties associated with reduced dimensionality, well-defined in-plane structure, and tunable functionality. Although a great deal of effort has been made to obtain SCOFs with different linkages and building blocks via both "top-down" exfoliation and "bottom-up" surface synthesis approaches, the obtained SCOFs generally suffer a low crystallinity, which impedes the understanding of intrinsic properties of the materials. Herein, we demonstrate a self-limiting solid-vapor interface reaction strategy to fabricate highly ordered SCOFs. The coupling reaction is tailored to take place at the solid-vapor interface by introducing one precursor via vaporization to the surface preloaded with the other precursor. Following this strategy, highly ordered honeycomb SCOFs with imine linkage are obtained. The controlled formation of SCOFs in our study shows the possibility of a rational design and synthesis of SCOFs with desired functionality. © 2013 American Chemical Society.

Fu Q.,Lanzhou University | Fu Q.,University of Washington | Feng S.,University of Arkansas
Journal of Geophysical Research B: Solid Earth | Year: 2014

The dryness of terrestrial climate can be measured by the ratio of annual precipitation (P) to potential evapotranspiration (PET), where the latter represents the evaporative demand of the atmosphere, which depends on the surface air temperature, relative humidity, wind speed, and available energy. This study examines how the terrestrial mean aridity responds to global warming in terms of P/PET using the Coupled Model Intercomparison Project phase 5 transient CO2 increase to 2×CO2 simulations. We show that the (percentage) increase (rate) in P averaged over land is ∼1.7%/°C ocean mean surface air temperature increase, while the increase in PET is 5.3%/°C, leading to a decrease in P/PET (i.e., a drier terrestrial climate) by ∼3.4%/°C. Noting a similar rate of percentage increase in P over land to that in evaporation (E) over ocean,we propose a framework for examining the change in P/PET, in which we compare the change in PET over land and E over ocean, both expressed using the Penman-Monteith formula. We show that a drier terrestrial climate is caused by (i) enhanced land warming relative to the ocean, (ii) a decrease in relative humidity over land but an increase over ocean, (iii) part of increase in net downward surface radiation going into the deep ocean, and (iv) different responses of PET over land and E over ocean for given changes in atmospheric conditions (largely associated with changes in temperatures). The relative contributions to the change in terrestrial mean aridity from these four factors are about 35%, 35%, 15%, and 15%, respectively. The slight slowdown of the surface wind over both land and ocean has little impact on the terrestrial mean aridity. ©2014. American Geophysical Union. All Rights Reserved.

Huang X.-F.,Lanzhou University | Ma J.-X.,Ningxia University | Liu W.-S.,Lanzhou University
Inorganic Chemistry | Year: 2014

On the basis of lanthanide metalloligands, [Ln(ODA)3] 3- (H2ODA = oxydiacetic acid), three series of d-f heterometallic metal-organic frameworks, {[Co(H2O) 6]·[Ln2(ODA)6Co2] ·6H2O}n [1; Ln = Gd (1a), Dy (1b), and Er (1c)], {[Ln2(ODA)6Cd3(H2O) 6]·mH2O}n [2; Ln = Pr (2a), Nd (2b), Sm (2c), Eu (2d), and Dy (2e), m = 9, 6, or 3], and {[Cd(H2O) 6]·[Ln2(ODA)6Cd2] ·mH2O}n [3; Ln = Dy (3a), Ho (3b), Er (3c), Tm (3d), and Lu (3e), m = 6 or 12], were designed and synthesized by a solvent volatilization and hydrothermal method. Magnetic investigation of 1 reveals the ferromagnetic interactions between the metal ions. In 2, LnIII ions occupied the inversion centers, which are confirmed by the fact that the emission intensity ratio of 5D0 → 7F 1 to 5D0 → 7F2 of the EuIII ion is much more than 3 in 2d. It is worth noting that, in 2d, the intensity ratio I(5D0→7F 1)/I(5D0→7F2) could decrease significantly upon the introduction of different hydrophilic guest molecules, which implies that the luminescent properties of 2d have a strong dependence on the geometry of the first coordination sphere of the Eu III ion. © 2014 American Chemical Society.

Su Y.,Lanzhou University | Su Y.,Ningxia University | Tu Y.-Q.,Lanzhou University | Gu P.,Ningxia University
Organic Letters | Year: 2014

The asymmetric transfer hydrogenation of racemic β-azidocyclopropane carboxylates has been explored. Ru-TsDPEN B is found to be a good catalyst for the formation of enantioenriched γ-lactones through a four-step sequence of azide reduction/cyclopropane ring cleavage/ketone transfer hydrogenation/lactonization, and the enantiomeric excess of the lactones was up to 94%. © 2014 American Chemical Society.

Xu H.,CAS Beijing National Laboratory for Molecular | Xu H.,Lanzhou University | Xie L.,CAS Beijing National Laboratory for Molecular | Zhang H.,Lanzhou University | Zhang J.,CAS Beijing National Laboratory for Molecular
ACS Nano | Year: 2011

We studied the modulation of Raman scattering intensities of molecules on graphene by tuning the graphene Fermi level with electrical field effect (EFE). A series of metal phthalocyanine (M-Pc) molecules (M = Mn, Fe, Co, Ni, Cu, Zn), which have different molecular energy levels, were used as probe molecules. The Raman intensities of all these M-Pc molecules become weaker when the graphene Fermi level is up-shifted by applying a positive gate voltage, while they become stronger when the graphene Fermi level is down-shifted by applying a negative gate voltage. However, this Raman intensity modulation only occurs when applying the gate voltage with a fast sweep rate, while it is nearly absent when applying the gate voltage with a slow sweep rate, which is likely due to the arising of the hysteresis effect in the graphene EFE. In addition, the Raman modulation ability for M-Pc molecules with smaller energy gaps is larger than that with larger energy gaps due to the difference in the energy alignment between graphene and these M-Pc molecules. Furthermore, this modulation shows the greatest one on single-layer graphene and mainly comes from the first layer of molecules which are in direct contact with graphene. The Raman modulation of molecules in GERS with the EFE suggests that the Raman enhancement for GERS occurs through a chemical enhancement mechanism. © 2011 American Chemical Society.

Xu H.,Lanzhou University | Liu X.,Lanzhou University | Matsuki T.,Tokyo Kasei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Using the effective Lagrangian approach, we study the decay behavior of the newly observed B(5970) meson, which is assigned as the 2S13 state in the B meson family. A more important prediction is the detailed information of the partial and total decay widths of B(2S01), Bs(2S01), and Bs(2S13) as the spin and strange partners of B(5970), which can be tested in future experimental searches for these missing states. © 2014 American Physical Society.

China has a long tradition of agriculture production. Millet crops including foxtail millet and broomcorn millet were firstly domesticated in north China, thereafter the development of millet-based agriculture (also called "rain-fed" agriculture) provided important foundation for the emergence of ancient Chinese civilization, which might have also exerted unprecedented impact on natural environments. Previous studies revealed that the Yangtse River valley of south China and the Yellow River valley of north China were the original center of rice agriculture and rain-fed agriculture respectively. The history for the development of rain-fed agriculture during Neolithic period has been intensively concerned, for the central north China was the cradle for the origin of ancient Chinese civilization in early 4th Millennium BP (Before present). Archaeologists summarized the timeline for the development of rain-fed agriculture in Neolithic China, based on archaeobotanical evidences, while the space variation in this process has not been adequately studied, the spatial-temporal intensification and expansion of rain-fed agriculture in Neolithic Age remains blurring. Whether human behaviors of slash-and-burn cultivation had significantly and extensively affected their surrounding environments after the emergence of intensive rain-fed agriculture, has also not been well understood, due to the lack of interdisciplinary studies, for example, the cross-over studies between archaeology and earth sciences. The issue is valuable for the discussion of the hot argument of "Anthropocene", which is nominated as a new geological epoch. Some scholars argue for an onset of Anthropocene between 1945-1964 AD, when intensive atmospheric nuclear testing resulted in peak values of 14C that is widely recorded in tree rings and sediments, while other scholars argued its beginning may be traced back to the early Holocene. This latter argument is related to the beginnings of significant landscape modification through the development and spread of agricultural practices in old world since 10,000 BP. In an article coauthored by Guanghui Dong, Shanjia Zhang, Yishi Yang, Jianhui Chen and Fahu Chen, scholars at MOE Key Laboratory of Western China's Environmental System, Lanzhou University, the intensification and expansion of agriculture during Neolithic Age in northern China and its imprints in paleo-environmental records has been detected, based on the comparative analysis of multidisciplinary evidences. These five scholars reviews the results of archaeobotanical and dating studies, and carbon isotope analysis of human bones from Neolithic sites and compares them with black carbon content from palaeoenvironment records in northern China. Based on these works, they conclude that millet cultivation was an auxiliary subsistence strategy in northern China from 10,000 to 7000 BP with hunting-gathering the primary subsistence strategy, the earliest millet-cultivation might have emerged in eastern Inner Mongolia post 7700 BP. Millet cultivation transited from a secondary strategy to become dominant in the Guanzhong area of north-central China during 7000-6000 BP, and probably facilitated the development of early Yangshao culture in the middle reaches of the Yellow River valley. Intensive millet-based agriculture emerged and widely expanded across the Yellow River valley in northern China during 6000-4000 BP. This promoted rapid population growth and cultural evolution in the late Neolithic period, and was key in the subsequent emergence of the ancient Chinese civilization. The temporal-spatial variation of black carbon (EC-soot) corresponds well with the intensification and expansion of millet-based agriculture during Neolithic period, suggesting intensive millet agriculture production activities exerted evident impact on fire frequency in northern China. This work provides a valuable case study for understanding the temporal and spatial development of millet agriculture, and human-environment interactions in northern China during Neolithic period from an Anthropocene perspective. This research was funded by "Strategic Priority Research Program of the Chinese Academy of Sciences (XDA05130601), the National Natural Science Foundation of China (41271218), and Fundamental Research Funds for the Central Universities (lzujbky-2015-k09). See the article: Dong G H, Zhang S J, Yang Y S, Chen J H, Chen F H. Agricultural intensification and its impact on environment during Neolithic Age in northern China (in Chinese). Chin. Sci. Bull., 2016, 61: 2913-2925, doi: 10.1360/N972016-00547. This article was published online in the Chinese Science Bulletin, by Science China Press, (http://engine. ).

Zhang G.,Lanzhou University | Wang S.,Lanzhou University | Ma Y.,Lanzhou University | Kong W.,Lanzhou University | And 2 more authors.
Advanced Synthesis and Catalysis | Year: 2013

A metal-free intramolecular oxidative cross-coupling reaction for the constructing Csp3-Csp3 bonds mediated by 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) under mild conditions was realized for the first time. This novel strategy provides a simple, efficient, and environmentally friendly access to diverse ring-fused tetrahydroquinoline derivatives. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen Y.,Lanzhou University | Chen Y.,Korea Institute of Science and Technology | Park S.-K.,Korea Institute of Science and Technology | Ma Y.,Lanzhou University | Ala R.,Korea Institute of Science and Technology
IEEE Transactions on Neural Networks | Year: 2011

An automatic parameter setting method of a simplified pulse coupled neural network (SPCNN) is proposed here. Our method successfully determines all the adjustable parameters in SPCNN and does not need any training and trials as required by previous methods. In order to achieve this goal, we try to derive the general formulae of dynamic threshold and internal activity of the SPCNN according to the dynamic properties of neurons, and then deduce the sub-intensity range expression of each segment based on the general formulae. Besides, we extract information from an input image, such as the standard deviation and the optimal histogram threshold of the image, and attempt to build a direct relation between the dynamic properties of neurons and the static properties of each input image. Finally, the experimental segmentation results of the gray natural images from the Berkeley Segmentation Dataset, rather than synthetic images, prove the validity and efficiency of our proposed automatic parameter setting method of SPCNN. © 2011 IEEE.

Aboudi J.,Tel Aviv University | Zheng X.,Lanzhou University | Jin K.,Lanzhou University
International Journal of Engineering Science | Year: 2014

A micromechanical analysis is offered for the prediction of the effective behavior and internal field distribution of multiphase magnetostrictive composites. The analysis is based on the homogenization technique for periodic composites. The nonlinear coupled constitutive relations of the monolithic magnetostrictive have been recently established at room and elevated temperatures and verified by comparisons with experimental results. Due to the nonlinearity of these constitutive equations, the micromechanical method is based on an incremental procedure which provides the instantaneous magneto-thermo-elastic concentrations tensors that relate the local field to the externally applied loading. In addition, the analysis provides the instantaneous effective tangent tensors as well as the macroscopic constitutive equations which govern the current global behavior of the magnetostrictive composite. The present analysis provides an efficient tool for analyzing magnetostrictive composites with continuous and arbitrary inclusion phases. Results present a parametric study of the effect of applied pre-stresses, elevated temperatures and magnetostrictive phase geometry and volume fraction on a magnetostrictive/epoxy composite response that is subjected to external magnetic field. The distributions of the induced magnetostrictions in the constituents are shown in various circumstances. © 2014 Elsevier Ltd. All rights reserved.

Chen Q.,Lanzhou University | Liang J.,Lanzhou University | Wang S.,Lanzhou University | Wang D.,Lanzhou University | And 2 more authors.
Chemical Communications | Year: 2013

The first organocatalytic Michael-cyclization cascade reaction between isothiocyanato oxindoles and unsaturated pyrazolones has been developed. The multicyclic spiro[oxindole/thiobutyrolactam/pyrazolone] core structures containing three contiguous stereogenic centers, including two spiro quaternary centers, were prepared with excellent diastereo- (up to >20:1) and enantioselectivities (up to 99% ee). This journal is © The Royal Society of Chemistry 2013.

Wang L.,Lanzhou University | Shi X.-M.,Lanzhou University | Dong W.-P.,Lanzhou University | Zhu L.-P.,Lanzhou University | And 2 more authors.
Chemical Communications | Year: 2013

Highly functionalized spiro[γ-butyrolactone-pyrrolidin-3,3′- oxindole] tricyclic skeletons were delivered successfully with high optical purity using an effective yet simple procedure. © 2013 The Royal Society of Chemistry.

Yang Y.,CAS Shanghai Institute of Organic Chemistry | Fu X.,CAS Shanghai Institute of Organic Chemistry | Chen J.,CAS Shanghai Institute of Organic Chemistry | Zhai H.,CAS Shanghai Institute of Organic Chemistry | Zhai H.,Lanzhou University
Angewandte Chemie - International Edition | Year: 2012

As easy as ABCD: (-)-Jiadifenin was synthesized in eighteen reaction steps from 1-[(E)-(4′-bromo-2′-butenyl)oxy]-4-methoxybenzene. Key features of this synthesis include: 1) Ireland-Claisen rearrangement to produce the two contiguous quaternary centers at C5 and C6 simultaneously, 2) intramolecular Pauson-Khand reaction (IMPKR) to concurrently construct the A and B rings, and 3) [2+2] photo-cycloaddition to generate the all-carbon quaternary center at C9. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen J.,CAS Shanghai Institute of Organic Chemistry | Gao P.,CAS Shanghai Institute of Organic Chemistry | Yu F.,CAS Shanghai Institute of Organic Chemistry | Yang Y.,CAS Shanghai Institute of Organic Chemistry | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2012

An efficient total synthesis of (±)-merrilactoneA has been accomplished, featuring: 1)a Johnson-Claisen rearrangement and the subsequent deprotection-lactonization to generate the Aring, 2)an intramolecular hetero-Pauson-Khand reaction to construct the B and Drings, and 3)a vinylogous Mukaiyama-Michael reaction and reductive carbonyl-alkene coupling to assemble the Cring. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cao Y.,Lanzhou University | Jiang X.,Lanzhou University | Liu L.,Lanzhou University | Shen F.,Lanzhou University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2011

A-spiro-ing: The title reaction of α-isothiocyanato imides and methyleneindolinones has been realized for the first time using 1 as the catalyst. This newly developed synthetic method provides a simple, efficient, and environmentally friendly way to access, in an enantioselective manner, densely functionalized spirooxindoles having three contiguous stereogenic centers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lin L.,Lanzhou University | Zhang J.,Lanzhou University | Ma X.,Lanzhou University | Fu X.,Lanzhou University | And 2 more authors.
Organic Letters | Year: 2011

Bifunctional 3, 3'-Ph 2-BINOL-Mg catalyzed direct asymmetric vinylogous Michael addition