检索结果-南通市图书馆

Viscosity in water from first-principles and deep-neural-network simulations

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

npj Computational Materials 2022年第1期8卷 1318-1327页

作者： Cesare Malosso Linfeng Zhang Roberto car Stefano Baroni Davide Tisi SISSA—Scuola Internazionale Superiore di Studi Avanzati 34136TriesteItaly Program in Applied and Computational Mathematics Princeton UniversityPrincetonNJ08544USA DP Technology Beijing100080PR China Department of Chemistry Department of Physicsand Princeton Institute for the Science and Technology of MaterialsPrinceton UniversityPrincetonNJUSA CNR Istituto officina dei Materiali SISSA Unit34136TriesteItaly

We report on an extensive study of the viscosity of liquid water at near-ambient conditions,performed within the Green-Kubo theory of linear response and equilibrium ab initio molecular dynamics(AIMD),based on density-functional theory(DFT).In order to cope with the long simulation times necessary to achieve an acceptable statistical accuracy,our ab initio approach is enhanced with deep-neural-network potentials(NNP).This approach is first validated against AIMD results,obtained by using the Perdew–Burke–Ernzerhof(PBE)exchange-correlation functional and paying careful attention to crucial,yet often overlooked,aspects of the statistical data ***,we train a second NNP to a dataset generated from the Strongly Constrained and Appropriately Normed(SCAN)*** the error resulting from the imperfect prediction of the melting line is offset by referring the simulated temperature to the theoretical melting one,our SCAN predictions of the shear viscosity of water are in very good agreement with experiments.

关键词： viscosity Strongly ambient

Finite-Size Conformational Transitions: A Unifying Concept Underlying Chromosome Dynamics

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2014年第10期61卷 607-616页

作者： Bertrand R.caré Pascal carrivain Thierry Forné Jean-Marc Victor Annick Lesne Laboratoire de Physique Théorique de la Matière Condensée CNRS UMR 7600UPMC University Paris 06F-75005ParisFrance CNRS GDR 3536 UPMC University Paris 06F-75005ParisFrance Institut de Génétique Humaine CNRS UPR 1142 MontpellierFrance Institut de Génétique Moléculaire de Montpellier CNRS UMR 5535University of MontpellierMontpellierFrance Kavli Institute for Theoretical Physics China CAS

Investigating average thermodynamic quantities is not sufficient to understand conformational transitions of a finite-size polymer. We propose that such transitions are better described in terms of the probability distribution of some finite-size order parameter, and the evolution of this distribution as a control parameter varies. We demonstrate this claim for the coil-globule transition of a linear polymer and its mapping onto a two-state model. In a biological context, polymer models delineate the physical constraints experienced by the genome at different levels of organization,from DNA to chromatin to chromosome. We apply our finite-size approach to the formation of plectonemes in a DNA segment submitted to an applied torque and the ensuing helix-coil transition that can be numerically observed, with a coexistence of the helix and coil states in a range of parameters. Polymer models are also essential to analyze recent in vivo experiments providing the frequency of pairwise contacts between genomic loci. The probability distribution of these contacts yields quantitative information on the conformational fluctuations of chromosome regions. The changes observed in the shape of the distribution when the cell type or the physiological conditions vary may reveal an epigenetic modulation of the conformational constraints experienced by the chromosomes.

关键词： coil-globule transition helix-coil transition chromosome conformational capture two-state model

Inter-population variabilities in seed mass and germination of Panicum turgidum and Pennisetum divisum in the desert of Kuwait

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2020年第1期12卷 144-153页

作者： Arvind BHATT Narayana R BHAT Afaf AL-NASSER María M carÓN AndreaSANTo Kuwait Institute for Scientific Research Safat 24885Kuwait Laboratory of Botanical Research(LABIBo) Faculty of Natural SciencesNational University of Salta-CONICETSalta 4400Argentina Independent Researcher Selargius 09047Italy

Understanding variability in seed germination among populations is essential for planning an effective germplasm collection for restoration and conservation *** knowledge of germination and dormancy patterns among populations of desert grasses is crucial for determining the potential of the species and populations to be used for restoration and conservation as well as forage *** in seed germination of Panicum turgidum Forssk and Pennisetum divisum(Gmel.)*** the desert of Kuwait was evaluated in different populations in May *** of seed germination(25 seeds and 4 replicates)was conducted for each population at night/day temperatures of 15℃/20℃and 20℃/30℃under the following light condition:continuous darkness or 12 h/12 h light/*** showed that seed masses of both species strongly varied according to their seed provenances,and both species produced heavier seeds in population with a higher soil electrical *** germination percentage considerably varied between two species,and the variation in *** was greater(17%–49%)than that of ***(72%–93%).Germination percentage in *** was greater at high temperature(20℃/30℃)than at low temperature(15℃/20℃).However,temperature regimes had no effect on germination percentage of *** *** germination time of both species exhibited significant inter-population *** result is especially relevant to assure the selection of the best population of each species and the regeneration success of the *** this,inter-population variability also provides valuable information for enhancing our understanding of the mechanisms that regulate seed germination and how they might be related to seed provenance.

关键词： desert grass seed germination inter-population variability seed provenance seed dormancy

Coupling textural and stable-isotope variations in fluvial stromatolites:Comparison of Pleistocene and recent records in NE Spain

在线全文

学校读者我要写书评

暂无评论

Journal of Palaeogeography 2019年第2期8卷 150-169页

作者： C.Arenas M.C.osácar L.Auqué C.Sancho Department of Earth Sciences University of Zaragoza Geotransfer Group and Institute for Research on Environmental Sciences of Aragón(IUCA)

Textural and stable isotopic features of two middle Pleistocene fluvial stromatolite profiles are compared to a recent stromatolite,both formed in the River Piedra system(NE Spain),to test the reliability of climatic,hydrologic and depositional information derived from ancient *** Pleistocene stromatolites formed in a multi-domed,highly-inclined *** recent stromatolite also formed in a highly-inclined cascade of the River Piedra,the sedimentary conditions of which were periodically examined between the years 2000 and *** Pleistocene stromatolites are formed of an alternation of 1) thin large-crystal laminae(type A),with elongated crystals up to 1 mm long,and 2) thick small-crystal laminae(type B),consisting of cyanobacterial fan-and bushshaped *** textural and isotopic comparison with the recent stromatolite shows that each A–B couplet corresponds to one *** type-A laminae are comparable to the macrocrystalline laminae that occur in the cool-period deposits of the recent stromatolite,and the type-B laminae are comparable to the warm-period deposits of the recent *** temperatures(Tw),calculated from δ^(18)o_(calcite) and present measures of δ^(18)o_(water),were similar in the Pleistocene and recent specimens,and close to the measured river ***,the Pleistocene stromatolites formed not far from isotopic equilibrium,as did the recent *** Pleistocene δ^(18) o_(calcite) biannual oscillation is wider in amplitude than in the recent stromatolite,which suggests larger differences in Tw through the year in the Pleistocene than at *** Pleistocene δ^(13)C_(calcite) does not show any pattern;and the values are slightly higher than the recent *** co-evolution of δ^(18)o and δ^(13)C is parallel in the Pleistocene stromatolites,matching the recent stromatolite *** results and their comparison with other ancient examples prove that textural and isotopic features in ancient stromatolites

关键词： Tufa Recent and ancient stromatolites Stable isotopes Biotic and abiotic laminae Intra-annual and inter-annual water temperature variations

Landscape Planning: A History of Influential Ideas

在线全文

学校读者我要写书评

暂无评论

中国园林 2001年第6期 91-96页

作者： car Steinitz

Determination of thyreostats in bovine urine using ultra-high performance liquid chromatography-tandem mass spectrometry

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

色谱 2017年第10期35卷 1048-1054页

作者： Lech RoDZIEWICZ Jolanta MASLoWIECKA Anna SADoWSKA Halina car Laboratory of Chemical Examination of Foodstuffs Department of Veterinary Hygiene Department of Experimental Pharmacology Medical University of Bialystok

Five thyreostats(TSs),namely tapazole,thiouracil,methylthiouracil,propylthiouracil,and phenylthiouracil,were determined in bovine urine using ultra-high performance liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS)in positive electrospray ionization *** and clean-up were achieved using a ChemElut cartridge with tert-butyl methyl ether,without a derivatization *** was achieved on an Acquity UPLC SS T3 *** mobile phase was acetonitrile and water containing 0.2%(v/v)formic *** mass spectrometer was operated in multiple reaction monitoring *** samples were spiked with TS solution at levels corresponding to 5,10,15,and 20μg/*** accuracy(internal standard corrected)ranged from 92%to 107%,with a repeatability precision(relative standard deviation,RSD)less than 15%for all five *** RSDs within-laboratory reproducibility was less than 26%.The decision limits(CCα)and detection capabilities(CCβ)were obtained from a calibration curve and were in the ranges of 3.1-6.1μg/L and 4.0-7.4μg/L,*** CCαand CCβvalues were below the recommended concentration,which was set at 10μg/*** results show that the described method is suitable for the direct detection of TSs in bovine *** method can also be used to determine TSs in porcine urine.

关键词： ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) thyreostats (TSs) urine

Development　on　manufacturing　technology　of　railway　locomotive　and　rolling　stock　industry　in　China

在线全文

学校读者我要写书评

暂无评论

China Welding 1994年第2期3卷 151-156页

作者： WANG Kejia (China National Railway Locomotive and Rolling-Stock Industry Corporation (100844 ))SUN Shuangjin (Changchun Railway car Works)

This paper described progress and development on the welding technology and vehicle manufacture during last decade, which promoted the technical progress for development and creation a considerable variety of high qua... 详细信息

关键词： manufacturing Development railway technology industry

Proportional-integral-derivative control of nonlinear half-car electro-hydraulic suspension systems

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第6期14卷 401-416页

作者： John E. D. EKoRU Jimoh o. PEDRo School of Mechanical Aeronautical and Industrial Engineering University of the Witwatersrand Private Bag 03 WITS 2050 Johannesburg South Africa

This paper presents the development of a proportional-integral-derivative (PID)-based control method for application to active vehicle suspension systems (AVSS). This method uses an inner PID hydraulic actuator force control loop, in combination with an outer PID suspension travel control loop, to control a nonlinear half-car AVSS. Robustness to model uncertainty in the form of variation in suspension damping is tested, comparing performance of the AVSS with a passive vehicle suspension system (PVSS), with similar model parameters. Spectral analysis of suspension system model output data, obtained by performing a road input disturbance frequency sweep, provides frequency response plots for both nonlinear vehicle suspension systems and time domain vehicle responses to a sinusoidal road input disturbance on a smooth road. The results show the greater robustness of the AVSS over the PVSS to parametric uncertainty in the frequency and time domains.

关键词： Force control Proportional-integral-derivative (PID) control Nonlinear half-car Active vehicle suspension system (AVSS) Hydraulic actuator dynamics Model uncertainty

在线全文

学校读者我要写书评

暂无评论

塞萨洛尼基（希腊北部）场地效应的实验研究

世界地震译丛 1993年第2期24卷 46-56,68页

作者： car.,CFJ 刘冬金