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Epigenetic control of meiotic recombination in plants

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Science China(Life Sciences) 2015年第3期58卷 223-231页

作者： YELINA Natasha DIAZ Patrick LAMBING christophe HENDERSON Ian R. Department of Plant Sciences University of Cambridge

Meiotic recombination is a deeply conserved process within eukaryotes that has a profound effect on patterns of natural genetic variation. During meiosis homologous chromosomes pair and undergo DNA double strand breaks generated by the Spo11 endonuclease. These breaks can be repaired as crossovers that result in reciprocal exchange between chromosomes. The frequency of recombination along chromosomes is highly variable, for example, crossovers are rarely observed in heterochromatin and the centromeric regions. Recent work in plants has shown that crossover hotspots occur in gene promoters and are associated with specific chromatin modifications, including H2 A.Z. Meiotic chromosomes are also organized in loop-base arrays connected to an underlying chromosome axis, which likely interacts with chromatin to organize patterns of ***, epigenetic information exerts a major influence on patterns of meiotic recombination along chromosomes, genetic variation within populations and evolution of plant genomes.

关键词： meiosis recombination epigenetic crossover chromatin

NumericalMethods for Balance Laws with Space Dependent Flux:Application to Radiotherapy Dose Calculation

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Communications in Computational Physics 2011年第10期10卷 1184-1210页

作者： christophe Berthon Martin Frank Celine Sarazin Rodolphe Turpault Universite de Nantes Laboratoire de Mathematiques Jean LerayUMR66292 rue de la HoussiniereBP 9220844322 Nantes Cedex 3France RWTH Aachen University MathematicsCenter for Computational Engineering ScienceSchinkelstrasse 252062 AachenGermany

The present work is concerned with the derivation of numerical methods to approximate the radiation dose in external beam *** address this issue,we consider a moment approximation of radiative transfer,closed by an entropy minimization *** model under consideration is governed by a system of hyperbolic equations in conservation form supplemented by source *** main difficulty coming from the numerical approximation of this system is an explicit space dependence in the flux ***,this dependence will be seen to be stiff and specific numerical strategiesmust be derived in order to obtain the needed accuracy.A first approach is developed considering the 1D case,where a judicious change of variables allows to eliminate the space dependence in the flux *** is not possible in *** therefore reinterpret the 1D scheme as a scheme on two meshes,and generalize this to 2D by alternating transformations between separate *** call this procedure projection *** numerical experiments,coming from medical physics,illustrate the potential applicability of the developed method.

关键词： Radiotherapy hyperbolic system of conservation laws source term approximations finite volume methods

Patterns of climber distribution in temperate forests of the Americas

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Journal of Plant Ecology 2016年第6期9卷 724-733页

作者： Annik Schnitzler Javier Amigo Brack Hale christophe Schnitzler Laboratoire Interdisciplinaire des Environnements Continentaux(LIEC) UMR 7360 Universitéde LorraineMetzFrance Laboratorio de Botánica Facultad de FarmaciaUniversidad de Santiago de CompostelaA CoruñaSpain Franklin University Switzerland SorengoSwitzerland Facultédes Sciences du Sport UnistraUniversitéde StrasbourgStrasbourgFrance

Aims and Methods We propose a standard protocol at the landscape to continental scale for examining to what extent the range of ecological conditions found in temperate latitudes explains the variations in climber species richness and *** protocol was tested in forests of the two *** data set included 151 climber *** selected four categorical traits and grouped these species into six clusters with regard to these *** records of American forests were first gathered into alliances,second combined with bioclimatic indices(rainfall,temperature,continentality).We obtained a total of 59 vegetational units in which we calculated values of climber species richness and proportion of *** units were ultimately gathered into five forest formations(characterized by leaf longevity).Wetlands and uplands were considered *** Findings Our results emphasize clear trends in large-scale patterns of climber distribution,independently of *** species richness(in particular woody climbers)peaks in moist and warm upland forests with oceanic climates,and where conifers are *** flooded areas,climber richness is also very high and peaks in seasonally flooded large *** ecological conditions of frost,dryness or lack of nutrients,climber species richness,abundance and trait diversity decline,resulting in the dominance of small,twining and deciduous life traits.

关键词： American forest bioclimatic indices climber life traits standart protocol species richness

A high-resolution clay mineralogical record in the northern South China Sea since the Last Glacial Maximum,and its time series provenance analysis

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Chinese Science Bulletin 2010年第35期55卷 4058-4068页

作者： LIU ZhiFei LI XiaJing COLIN christophe GE HuangMin State Key Laboratory of Marine Geology Tongji University Shanghai 200092 China Laboratoire IDES UMR 8148 CNRS Universit~ de Paris XI Orsay 91405 France

High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea(SCS) covering the period since the Last Glacial Maximum shows that illite(29%-48%),smectite(14%-45%),chlorite(17%-28%),and minor kaolinite(6%-14%) comprise the clay mineral assemblage,and that time series variation does not present glacial-interglacial *** analysis indicates three end-member sources:almost all smectite derives from Luzon,all kaolinite is sourced from the Pearl River,and illite and chlorite originate from both the Pearl River and *** comparing clay mineral compositions in surface sediments from the three major source areas and of the SCS,we reconstructed a time series of clay mineral contribution from the major provenances to the northern slope of the SCS using the linear separation method for illite *** were three stages of provenance change.(1) During 24.1-17.5 ka BP,contributions from Taiwan and Luzon were similar(30%-40%),while that from the Pearl River was only 25%.(2) During 17.5-14.0 ka BP,the contribution from Luzon decreased rapidly to 20%-25%,while that from Taiwan increased to 35% from an average of 25% at 18 ka BP,and that from the Pearl River increased largely to 40%.(3) During the Holocene,differences in contributions from the three major provenances increased:the contribution from Luzon increased slightly and then remained at 27%-35%,that from Taiwan increased rapidly and then remained at 55%-60%,and that from the Pearl River decreased to 15%.The change in clay mineral contributions from different provenances is influenced mainly by clay mineral production,monsoon rainfall denudation,oceanic current transport,and sea-level change.

关键词：粘土矿物南海北部时间序列高分辨率中国海末次盛冰期 Sea 珠江源

Representation of A15 composition and T_C in internal-Sn Nb_3Sn superconducting strands

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Science China(Technological Sciences) 2010年第11期53卷 3020-3026页

作者： Andre SULPICE Jean-Louis SOUBEYROUX christophe VERWAERDE Gia Ky HOANG NEEL/CNRS-UJF ALSTOM 3 bis avenue des 3 Chenes 90018 Belfort France

Four sets of mono-element (ME) and two kinds of multifilament (MF) internal-Sn Nb3Sn superconducting strands were designed and fabricated through RRP method in which different compoment ratios, various composite configurations and some third element alloying were arranged. All the strand samples underwent a 210°C/50 h + 340°C/25 h thermal duration for Cu-Sn alloying. After that A15 phase formation heat treatment (HT) was applied for which the ME samples were chosen at three reaction temperatures of 675°C, 700°C and 725°C for 100 h and 200 h while the MF samples at four temperatures of 650°C, 675°C, 700°C and 725°C for 128 h and 200 h. The heat-treated samples were examined for A15 phase composition distribution by X-ray EDS. SQUID magnetization measurement was used to determine critical temperature TC. The obtained results demonstrate that for fully-reacted internal-Sn Nb3Sn superconductors the A15 phase composition and the intrinsic property TC are determined by the diffusion and solid state reaction mechanism and are independent of the factors including HT temperature, strand composite component and configuration arrangement, and the third element addition within the experimental range.

关键词： internal-Sn Nb3Sn strands A15 phase composition phase formation heat treatment composite configuration and design third element alloying

A high-order SPH method by introducing inverse kernels

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Chinese Journal of Aeronautics 2017年第1期30卷 1-14页

作者： Fang Le Marongiu Jean christophe Leduc Julien Amicarelli Andrea Caro Joёlleb LMP Ecole centrale de Pekin Beihang University Co-Innovation Center for Advanced Aero-Engine 100083 Beijing China LMFA Ecole centrale de Lyon 69130 Ecully BP 163 France Laboratoire International Associe Beihang University 100083 Beijing China ANDRITZ HYDRO AG Rue des Deux-Gares 6 1800 Vevey Switzerland

The smoothed particle hydrodynamics（SPH） method is usually expected to be an efficient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by introducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square（LS） and Moving-Least-Square（MLS） methods. Then detailed analysis in spectral space is presented for people to better understand this method. Finally we show three test examples to verify the method behavior.

关键词： Consistency High-order method Inverse method Numerical dissipation Numerical instability Smoothed particle hydrodynamics

Improving metal reflectors by suppressing surface plasmon polaritons: a priori calculation of the internal reflectance of a solar cell

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Light(Science & Applications) 2013年第1期2卷 32-37页

作者： Zachary C Holman Stefaan De Wolf christophe Ballif Swiss Federal Institute of Technology Lausanne(EPFL)Institute of Microengineering(IMT)Photovoltaics and Thin-Film Electronics LaboratoryCH-2000 NeuchaˆtelSwitzerland

Imperfect internal reflectance of near-bandgap light reduces the performance of all solar cells,and becomes increasingly detrimental as absorbers become *** consider light incident on the silicon/dielectric/metal structure at the back of rear-passivated crystalline silicon solar cells with surface textures that are large enough for geometric *** calculating the absorbance in the metal as a function of the angle of incidence,we discover three results that are important for understanding and improving rear reflectors in many types of solar ***,significant parasitic absorption occurs in the metal layer in two cases:s-and p-polarized propagating modes(near-normal angles of incidence)when the dielectric thickness is adjusted to cause destructive interference of the reflected beams,and p-polarized evanescent modes(angles of incidence above the semiconductor/dielectric critical angle)that excite surface plasmon polaritons at the metal ***,the latter loss dominates;a well-designed rear dielectric passivation layer must suppress the penetration of evanescent waves to the ***,when used as an input in a simple analytical model,the average rear internal reflectance calculated by assuming a Lambertian angular distribution of light accurately predicts the total reflectance and absorbance of a solar cell.

关键词： light trapping photovoltaics plasmon silicon solar cell

Chaos in DNA evolution

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International Journal of Biomathematics 2016年第5期9卷 199-215页

作者： Jacques M. Bahi christophe Guyeux Antoine Perasso Institut FEMTO-ST Universitg Bourgogne Franche-Comtd 25000 Besancon France UMR Chrono-Environnement Universite Bourgogne Franche-Comte 25000 Besancon France

In this paper, we explain why the chaotic mutation （CM） model of J. M. Bahi and C. Michel （2008） simulates the genes mutations over time with good accuracy. It is firstly shown that the CM model is a truly chaotic one, as it is defined by Devaney. Then, it is established that mutations occurring in genes mutations have indeed a same chaotic dynamic, thus making relevant the use of chaotic models for genomes evolution. Transposition and inversion dynamics are finally investigated.

关键词： Genomes evolution models mutations inversions transpositions mathema- tical topology Devaney's chaos.

A Two-Step Algorithm to Estimate Variable Importance for Multi-State Data:An Application to COVID-19

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Computer Modeling in Engineering & Sciences 2023年第6期135卷 2047-2064页

作者： Behnaz Alafchi Leili Tapak Hassan Doosti christophe Chesneau Ghodratollah Roshanaei Department of Biostatistics School of Public HealthModeling of Noncommunicable Diseases Research CenterHamadan University of Medical SciencesHamadanIran School of Mathematical and Physical Sciences Macquarie UniversitySydneyAustralia Department of Mathematics LMNOUniversity of Caen-NormandieCaenFrance

Survival data with amulti-state structure are frequently observed in follow-up *** analytic approach based on a multi-state model(MSM)should be used in longitudinal health studies in which a patient experiences a sequence of clinical progression *** main objective in the MSM framework is variable selection,where attempts are made to identify the risk factors associated with the transition hazard rates or probabilities of disease *** usual variable selection methods,including stepwise and penalized methods,do not provide information about the importance of *** this context,we present a two-step algorithm to evaluate the importance of variables formulti-state *** differentmachine learning approaches(randomforest,gradient boosting,and neural network)as themost widely usedmethods are considered to estimate the variable importance in order to identify the factors affecting disease progression and rank these factors according to their *** performance of our proposed methods is validated by simulation and applied to the COVID-19 data *** results revealed that the proposed two-stage method has promising performance for estimating variable importance.

关键词： Multi-state data deviance residual martingale residual gradient boosting randomforest neural network variable importance variable selection