检索结果-南通市图书馆

Galaxy formation in the reionization epoch as hinted by WideField Camera 3 observations of the Hubble Ultra Deep Field

引用

Research in Astronomy and Astrophysics 2010年第9期10卷 867-904页

作者： Hao-jing Yan Rogier A. Windhorst Nimish E Hathi Seth H. Cohen Russell E.Ryan Robert W. O＇Connell patrick j. McCarthy Center for Cosmology and AstroParticle Physics The Ohio State University 191 West Woodruff Avenue Columbus OH 43210 USA School of Earth and Space Exploration Arizona State University Tempe AZ 85287 USA Department of Physics ＆ Astronomy University of California Riverside CA 92521 USA Department of Physics University of California One Shields Avenue Davis CA 95616 USA Astronomy Department University of Virginia P.O. Box 3818 Charlottesville VA 22903 USA Observatories of the Carnegie Institution of Washington 813 Santa Barbara Street Pasadena CA 91101 USA

We present a large sample of candidate galaxies at z ≈ 7 - 10, selected in the Hubble Ultra Deep Field using the new observations of the Wide Field Camera 3 that was recently installed on the Hubble Space Telescope. Our sample is composed of 20 z850-dropouts （four new discoveries）, 15 Y105-dropouts （nine new discoveries） and 20 j125-dropouts （all new discoveries）. The surface densities of the Z850-dropouts are close to what was predicted by earlier studies, however, those of the Y105- and j125-dropouts are quite unexpected. While no Y105- or j125-dropouts have been found at AB ≤ 28.0 mag, their surface densities seem to increase sharply at fainter levels. While some of these candidates seem to be close to foreground galaxies and thus could possibly be gravitationally lensed, the overall surface densities after excluding such cases are still much higher than what would be expected if the luminosity function does not evolve from z ～ 7 to 10. Motivated by such steep increases, we tentatively propose a set of Schechter function parameters to describe the luminosity functions at z ≈8 and 10. As compared to their counterpart at z ≈ 7, here L^＊ decreases by a factor of ～ 6.5 and Ф^＊ increases by a factor of 17-90. Although such parameters are not yet demanded by the existing observations, they are allowed and seem to agree with the data better than other alternatives. If these luminosity functions are still valid beyond our current detection limit, this would imply a sudden emergence of a large number of low-luminosity galaxies when looking back in time to z ≈ 10, which, while seemingly exotic, would naturally fit in the picture of the cosmic hydrogen reionization. These early galaxies could easily account for the ionizing photon budget required by the reionization, and they would imply that the global star formation rate density might start from a very high value at z ≈ 10, rapidly reach the minimum at z≈ 7, and start to rise again towards z ≈ 6. In this scenario, the maj

关键词： cosmology observations -- cosmology early universe -- galaxies evolution -- galaxies luminosity function, mass function -- infrared galaxies

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Active learning for accelerated design of layered materials

引用

npj Computational Materials 2018年第1期4卷 54-62页

作者： Lindsay Bassman Pankaj Rajak Rajiv K.Kalia Aiichiro Nakano Fei Sha jifeng Sun David j.Singh Muratahan Aykol patrick Huck Kristin Persson Priya Vashishta Collaboratory for Advanced Computing and Simulations University of Southern CaliforniaLos AngelesCA 90089USA Department of Physics and Astronomy University of Southern CaliforniaLos AngelesCA 90089USA Department of Chemical Engineering and Material Science University of Southern CaliforniaLos AngelesCA 90089USA Department of Computer Science University of Southern CaliforniaLos AngelesCA 90089USA Department of Biological Sciences University of Southern CaliforniaLos AngelesCA 90089USA Department of Physics and Astronomy University of MissouriColumbiaMO 65211-7010USA Lawrence Berkeley National Laboratory 1 Cyclotron RoadBerkeleyCA 94720USA

Hetero-structures made from vertically stacked monolayers of transition metal dichalcogenides hold great potential for optoelectronic and thermoelectric *** of the optimal layered material for specific applications necessitates the estimation of key material properties,such as electronic band structure and thermal transport ***,screening of material properties via brute force ab initio calculations of the entire material structure space exceeds the limits of current computing ***,the functional dependence of material properties on the structures is often complicated,making simplistic statistical procedures for prediction difficult to employ without large amounts of data ***,we present a Gaussian process regression model,which predicts material properties of an input hetero-structure,as well as an active learning model based on Bayesian optimization,which can efficiently discover the optimal hetero-structure using a minimal number of ab initio *** electronic band gap,conduction/valence band dispersions,and thermoelectric performance are used as representative material properties for prediction and *** Materials Project platform is used for electronic structure computation,while the BoltzTraP code is used to compute thermoelectric *** optimization is shown to significantly reduce the computational cost of discovering the optimal structure when compared with finding an optimal structure by building a regression model to predict material *** models can be used for predictions with respect to any material property and our software,including data preparation code based on the Python Materials Genomics(PyMatGen)library as well as python-based machine learning code,is available open source.

关键词： Active Python python

来源：

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

Molecular Cloning, Expression and Characterization of Ribokinase of Leishmania major

引用

Acta Biochimica et Biophysica Sinica 2007年第6期39卷 462-466页

作者： patrick. O. j. OGBUNUDE Nadia LAMOUR Michael P. BARRETT Department of Medical Biochemistry University of Nigeria Enugu 1000004 Nigeria Department of Biochemistry and Massey Cancer Center Virginia Commonwealth University Richmond 23298-0614 USA Institute of Biomedical and Life Sciences Division of Infection and Immunity Joseph Black Building University of Glasgow Glasgow G12 8QQ UK

Ribokinase （EC 2.***.7.15） from Leishmania major was cloned, sequenced and overexpressed in Escherichia coli. The gene expressed an active enzyme that had comparable activity to the same enzyme studied in E. coli. It specifically phosphorylated D-ribose. Under defined conditions, the Km for the substrates D-ribose and ATP were 0.3±0.04 mM and 0.2±0.02mM, respectively. The turnover numbers of the enzyme for the substrates were 10.8s-1and 10.2 s-1, respectively. The enzyme product ribose 5-phosphate inhibited the phosphorylation of D-ribose with an apparent Kiof 0.4 mM, which is close to the Km（0.3mM） of Dribose, suggesting that it might play a role in regulating flux through the enzyme.

关键词： Leishmania major D-ribose ribokinase molecular cloning

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Advanced non-alcoholic steatohepatitis cirrhosis: A high-risk population for pre-liver transplant portal vein thrombosis

引用

World journal of Hepatology 2017年第3期9卷 139-146页

作者： jonathan G Stine Curtis K Argo Shawn j Pelletier Daniel G Maluf Stephen H Caldwell patrick G Northup Division of Gastroenterology and Hepatology Department of Medicine Center for the Study of Coagulation Disorders in Liver Disease University of Virginia Division of Transplant Department of Surgery University of Virginia

AIMTo examine if liver transplant recipients with high-risk non-alcoholic steatohepatitis (NASH) are at increased risk for pre-transplant portal venous thrombosis. METHODSData on all liver transplants in the United States from February 2002 through September 2014 were analyzed. Recipients were sorted into three distinct groups: High-risk (age > 60, body mass index > 30 kg/m2, hypertension and diabetes), low-risk and non-NASH cirrhosis. Multivariable logistic regression models were constructed. RESULTSThirty-five thousand and seventy-two candidates underwent liver transplantation and of those organ recipients, 465 were transplanted for high-risk and 2775 for low-risk NASH. Two thousand six hundred and twenty-six (7.5%) recipients had pre-transplant portal vein thrombosis; 66 (14.2%) of the high-risk NASH group had portal vein thrombosis vs 328 (11.8%) of the low-risk NASH group. In general, all NASH recipients were less likely to be male or African American and more likely to be obese. In adjusted multivariable regression analyses, high-risk recipients had the greatest risk of pre-transplant portal vein thrombosis with OR = 2.11 (95%CI: 1.60-2.76, P CONCLUSIONLiver transplant candidates with high-risk NASH are at the greatest risk for portal vein thrombosis development prior to transplantation. These candidates may benefit from interventions to decrease their likelihood of clot formation and resultant downstream hepatic decompensating events. Prospective study is needed.

关键词： Liver transplantation Non-alcoholic fatty liver disease Portal hypertension Hepatology Coagulopathy

来源：

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

Effects of human disturbance on liana community diversity and structure in a tropical rainforest, Malaysia: implication for conservation

引用

journal of Plant Ecology 2012年第4期5卷 391-399页

作者： patrick Addo-Fordjour Zakaria B.Rahmad A.M.S.Shahrul School of Biological Sciences Universiti Sains MalaysiaPenangMalaysia

Aim Due to the important role of lianas in the functioning of forest ecosystem,knowledge of the factors that affect them are important in the management of ***,there are conflicting reports on the response of liana communities to disturbance,calling for more research in the *** present study was carried out to investigate the response of liana diversity and structure to human disturbance within two major forests in the Penang National Park,*** study also looked at the implication of the findings for *** A total of 15 40×40-m^(2)(or 40-m×40-m)plots each were randomly located across a range of habitats in a primary forest and disturbed secondary *** with diameter at breast height≥10 cm were examined for lianas with diameter≥2 *** lianas and trees were enumerated and compared between the two *** and structural variables of lianas were compared between the two forests using the t-test *** abundance was also compared between the two forests with t-test,while linear regression analysis was run to determine the effects of tree abundance on liana *** Findings A total of 46 liana species belonging to 27 genera and 15 families were identified in the *** disturbance significantly reduced liana species richness and species diversity in the secondary *** abundance remained the same in both forests whereas liana basal area was;7 times higher in the primary *** and hook climbers were significantly more abundant in the primary and secondary forest,*** diameter lianas were more abundant in the primary forest compared with the secondary *** diameter distribution of most families in the primary forest followed the inverted j-shaped curve whereas only a few of the families in the secondary forest did *** abundance was significantly higher in the primary *** abundance of lianas significantly depended on tree abundance in all the f

关键词： climbing mechanism conservation liana diversity and structure human disturbance

来源：

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

Synthesis of tetraarylmethanes:1897–2022

引用

Green Synthesis and Catalysis 2023年第4期4卷 273-292页

作者： Lai Chen jingqian Huo jinlin Zhang judith N.Currano Haixing Guan patrick j.Walsh jianyou Mao College of Plant Protection Hebei Agricultural UniversityBaoding 071000China Department of Chemistry University of PennsylvaniaPennsylvania 19104-6323United States Experimental Center Shandong Provincial Key Laboratory of Traditional Chinese Medicine for Basic ResearchKey Laboratory of Traditional Chinese Medicine Classical TheoryMinistry of EducationShandong University of Traditional Chinese MedicineJinan 250355China Technical Institute of Fluorochemistry(TIF) State Key Laboratory of Materials Oriented Chemical Engineering(MCE)School of Chemistry and Molecular EngineeringNanjing Tech UniversityNanjing 211816China

Tetraarylmethanes(TAMs)contain a carbon atom bound to four aryl *** have found diverse applications in chemistry,materials science,chemical biology and medicinal chemistry because of their unique 3-dimensional *** a reflection of the high demand for TAMs,over 32,000 unique TAMs have been *** distinct structures of TAMs and the crowded nature of the central carbon atom require different strategies for their *** we present the first review on the synthesis of TAMs,from classical approaches to modern methods,including enantioselective syntheses of *** provide a critical evaluation of methods and highlight important directions for future research into the synthesis of this aesthetically pleasing and very useful class of spherical structures.

关键词： Tetraarylmethane Tetraphenylmethane Cross-coupling Palladium Radicals Fridel-crafts Quaternary carbons

来源：

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

Spatial isolation and genetic differentiation in naturally fragmented plant populations of the Swiss Alps

引用

journal of Plant Ecology 2008年第3期1卷 149-159页

作者： patrick Kuss AndreaRPluess Hafdı´s HannaÆgisdottir jurg Stocklin Institute of Botany University of BaselSchonbeinstrasse 6CH-4056BaselSwitzerland Institute of Plant Sciences University of BernAltenbergrain21CH-3013BernSwitzerland Institute for Terrestrial Ecosystems Ecosystem ManagementETH ZurichUniversitatstrasse 168092 ZurichSwitzerland

The effect of anthropogenic landscape fragmentation on the genetic diversity and adaptive potential of plant populations is a major issue in conservation ***,little is known about the partitioning of genetic diversity in alpine species,which occur in naturally fragmented ***,we investigate molecular patterns of three alpine plants(Epilobium fleischeri,Geum reptans and Campanula thyrsoides)across Switzerland and ask whether spatial isolation has led to high levels of population differentiation,increasing over distance,and a decrease of within-population *** further hypothesize that the contrasting potential for long-distance dispersal(LDD)of seed in these species will considerably influence and explain diversity *** For each study species,we sampled 20–23 individuals from each of 20–32 populations across entire *** applied Random Amplified Polymorphic Dimorphism markers to assess genetic diversity within(Nei’s expected heterozygosity,He;percentage of polymorphic bands,Pp)and among(analysis of molecular variance,Ust)populations and correlated population size and altitude with within-population *** patterns of genetic relatedness were investigated using Mantel tests and standardized major axis regression as well as unweighted pair group method with arithmetic mean cluster analyses and Monmonier’s *** avoid known biases,we standardized the numbers of populations,individuals and markers using multiple random *** modelled LDD with a high alpine wind data set using the terminal velocity and height of seed release as key ***,we assessed a number of important life-history traits and factors that potentially influence genetic diversity partitioning(*** system,longevity and population size).Important findings For all three species,we found a significant isolation-by-distance relationship but only a moderately high differentiation among populations(Ust:22.7

关键词： Campanula thyrsoides Epilobium fleischeri Geum reptans isolation by distance molecular diversity

来源：

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

Parallel personal measurements of diesel engine exhaust and crystalline silica using dual sampling port

引用

International journal of Mining Science and Technology 2020年第3期30卷 313-319页

作者： Alan Fleck Caroline Couture Virginie Cabelguen patrick Eddy Ryan Ross Thuot Guillaume Lachapelle Hugo Coulombe Maximilien Debia Department of Environmental and Occupational Health University of MontrealMontreal H3T 1A8Canada Health and Safety Agnico Eagle MinesToronto M5C 2Y7Canada Health and Safety Westwood Mine(IAMGOLD)Preissac J0Y 2E0Canada

Diesel engine exhaust(DEE) and crystalline silica exposures occur simultaneously in the mining industry,and occupational sampling campaigns can be time-and cost-consuming. The authors evaluated a dualport system for simultaneous sampling of DEE and crystalline silica in laboratory and field *** tests evaluated the operation of pumps during 8 h sampling and the intensity of the flow variation for various filter loading conditions and for different modes of operation. Field validation was performed in an underground mine. Pumps operated in constant flow or constant pressure *** in constant flow mode showed that when the flowrate increased on one side of the system, it decreased on the opposite side according to the loading intensity. Tests in constant pressure mode showed that flowrates systematically decreased when using loaded cassettes. However, the higher the backpressure setting, the lower the flow variation was. Flow variations during field tests were generally within the acceptable ±5% range. However, significant flow variations were identified in higher concentrations. A significant negative correlation was found between flowrate variation and total carbon concentration. While the majority of tests support the use of the dual-port for evaluating concomitant exposures, results highlight the possibility of filter overloading as a cause of flowrate changes.

关键词： Crystalline silica Diesel engine exhaust Dual-port Mining Monitoring

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Regulation of Resource Partitioning Coordinates Nitrogen and Rhizobia Responses and Autoregulation of Modulation in Medicago tmncatula

引用

Molecular Plant 2019年第6期12卷 833-846页

作者： Beatriz Lagunas Mingkee Achom Roxanna Bonyadi-Pour Alonso j.Pardal Bethany L.Richmond Chrysi Sergaki Saul Vazquez patrick Schafer Sascha Ott john Hammond Miriam L.Gifford School of Life Sciences University of Warwick Coventry CV4 7AL UK Department of Computer Science University of Warwick Coventry CV4 7AL UK Gateway Building Sutton Bonington Campus University of Nottingham Sutton Bonington LE12 5RD UK School of Agriculture Policy and Development University of Reading Reading RG6 6AH UK Southern Cross Plant Science Southern Cross University Lismore NSW 2480 Australia

Understanding how plants respond to nitrogen in their environment is crucial for determining how they use it and how the nitrogen use affects other processes related to plant growth and development. Under nitrogen limitation the activity and affinity of uptake systems is increased in roots, and lateral root formation is regulated in order to adapt to low nitrogen levels and scavenge from the soil. Plants in the legume family can form associations with rhizobial nitrogen-fixing bacteria, and this association is tightly regulated by nitrogen levels. The effect of nitrogen on nodulation has been extensively investigated, but the effects of nodulation on plant nitrogen responses remain largely unclear. In this study, we integrated molecular and phenotypic data in the legume Medicago truncatula and determined that genes controlling nitrogen influx are differently expressed depending on whether plants are mock or rhizobia inoculated. We found that a functional autoregulation of nodulation pathway is required for roots to perceive, take up, and mobilize nitrogen as well as for normal root development. Our results together revealed that autoregulation of nodulation, root development, and the location of nitrogen are processes balanced by the whole plant system as part of a resource-partitioning mechanism.

关键词： Nitrogen transport Medicago root system architecture transcriptomics autoregulation of nodulation rhizobia

来源：

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

Regulation of cellular anabolism by mTOR:or how I learned to stop worrying and love translation

引用

Sports Medicine and Health Science 2020年第4期2卷 195-201页

作者： j.William Deaver Sara Mata López patrick j.Ryan Peter P.Nghiem Steven E.Riechman james D.Fluckey Department of Health and Kinesiology 107 Gilchrist Building2929 Research ParkwayTexas A&M UniversityCollege StationTXUSA Department of Veterinary Integrative Biosciences 402 Raymond Stotzer Pkwy Building 2Texas A&M UniversityCollege StationTXUSA

The process and regulation of cellular metabolism are extremely complex and accomplished through multiple signalling pathways that operate in parallel,and often experience significant overlap in upstream and downstream a signal *** this complexity,single pathway or even single protein activations are commonly used to extrapolate broad characterizations of cellular ***,multiple routes for peptide-chain translation initiation exist,some of which may be either exclusive or overlapping depending on the state and environment of the *** it may be highly impractical to account for every aspect of metabolic regulation and permutation of mRNA translation,it is important to acknowledge that investigations relating to these pathways are often incomplete and not necessarily indicative of the overall metabolic *** becomes urgent when considering the role that cellular anabolism plays in both healthy cellular functions and the aetiology of several disease's altered *** review describes recent advances in the understanding of cellular metabolic regulation,with specific focus given to the complexity of‘downstream’mRNA translation initiation through both mTOR-dependent and mTOR-independent signallings.

关键词： Anabolism Translation Protein synthesis Cap-dependent translation Cap-independent translation

来源：

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

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：