检索结果-南通市图书馆

基于改进遥感生态指数的青藏公路那(曲)安(多)段生态环境评估及驱动机制分析

在线全文

学校读者我要写书评

暂无评论

环境科学 2024年第3期45卷 1586-1597页

作者：傅楷翔贾国栋余新晓王旭北京林业大学水土保持学院北京100083 北京林业大学水土保持国家林业和草原局重点实验室北京100083

青藏公路沿线生态环境是西藏地区生态文明建设的重要组成部分,目前研究青藏高原独特的地理环境普遍存在数据获取困难、时效性过低及未考虑研究区独特的“高寒盐碱”环境状况等问题.基于GEE平台及研究区独特地理环境,对遥感生态指数(RSEI... 详细信息

青藏公路沿线生态环境是西藏地区生态文明建设的重要组成部分,目前研究青藏高原独特的地理环境普遍存在数据获取困难、时效性过低及未考虑研究区独特的“高寒盐碱”环境状况等问题.基于GEE平台及研究区独特地理环境,对遥感生态指数(RSEI)进行改进,采用主成分分析法构建一种新的适用于高寒盐碱地区的盐碱遥感生态指数(SRSEI)作为生态环境质量评价指标,利用Arc GIS 10.3平台、地理探测器等方法在多时空尺度下分析青藏公路那曲至安多段沿线生态环境质量空间分布格局与时间变异趋势,并探究自然和人为等8个控制因子对SRSEI时空变化的驱动机制.结果表明:(1)相较于RSEI,SRSEI对植被更加敏感,对植被稀疏和盐碱化严重地区的分辨能力更强,适合高寒盐碱区生态质量评价.(2)研究区生态环境质量空间尺度上存在明显的地理分异性,生态质量较差的区域主要集中在北部安多县城,质量等级为优和良地区主要分布在中西部和东南部那曲地区;时间尺度上32年间研究区生态环境整体呈改善趋势,中西部和东南部植被覆盖度明显增加,对生态环境有很强的改善作用,改善面积1 425.98 km^(2),占比99.82%.SRSEI均值为0.49,总体呈波动上升趋势,平均增幅为0.015 7 a^(-1).(3)土地利用方式是研究区生态环境质量变化中驱动力最大的影响因子,多年份平均q值0.1576,环境因子的影响力较低;多因子交互结果显示,研究区的生态环境现状是多重因素共同作用的结果,所有因子在交互作用下均有协同增强的作用,且人为因素的影响力在逐步上升,植被净初级生产力(NPP)和土地利用方式交互作用是研究区生态环境质量的主要交互控制因子.该研究可为那曲至安多段沿线生态环境保护和可持续发展提供理论依据.

关键词：生态环境质量遥感生态指数(RSEI) 地理探测器 GEE平台青藏公路沿线

一种利用对抗样本提高抽取式阅读理解模型效果的方法

在线全文

学校读者我要写书评

暂无评论

四川大学学报（自然科学版） 2024年第2期61卷 40-48页

作者：何东于晓昕叶子铭于中华陈黎四川大学计算机学院成都610065

抽取式阅读理解是自然语言处理的重要任务,需要机器在阅读理解自然语言文本的基础上,从中抽取给定问题的答案(输入文本中的片段),并在问题不可回答时拒绝回答.这种不可回答情况的存在使机器阅读理解更具有挑战性,特别是在输入文本含有... 详细信息

抽取式阅读理解是自然语言处理的重要任务,需要机器在阅读理解自然语言文本的基础上,从中抽取给定问题的答案(输入文本中的片段),并在问题不可回答时拒绝回答.这种不可回答情况的存在使机器阅读理解更具有挑战性,特别是在输入文本含有似是而非文本片段时,现有模型很容易将这样的片段混淆为问题答案,进而错误判断问题的可回答性.为了进一步提高抽取式机器阅读理解模型的效果,本文将SQuAD 2.0数据集中的似是而非答案看成对抗样本,将其既作为答案文本片段抽取的正例,也作为问题可回答性的负例,在现有模型答案交叉熵损失的基础上增加排序损失.在SQuAD 2.0上进行的实验表明,本文方法可以提高现有模型的阅读理解能力,明显提升可回答性判断及答案文本片段抽取的效果.

关键词：阅读理解不可回答问题对抗样本

Light-Regulated Stomatal Aperture in Arabidopsis

在线全文

学校读者我要写书评

暂无评论

Molecular Plant 2012年第3期5卷 566-572页

作者： Chen Chen yu-Guo xiao xin Li in Ni Department of Plant Biology University of Minnesota Saint Paul MN 55108 USA

The stomatal pores of plant leaves, situated in the epidermis and surrounded by a pair of guard cells, allow CO2 uptake for photosynthesis and water loss through transpiration. Blue light is one of the dominant environmental signals that control stomatal movements in leaves of plants in a natural environment. This blue light response is mediated by blue/UV A light-absorbing phototropins （phots） and cryptochromes （crys）. Red/far-red light-absorbing phytochromes （phys） also play a role in the control of stomatal aperture. The signaling components that link the perception of light signals to the stomatal opening response are largely unknown. This review discusses a few newly discovered nuclear genes, their function with respect to the phot-, cry-, and phy-mediated signal transduction cascades, and possible involve- ment of circadian clock.

关键词： circadian clock cryptochromes phototropins phytochromes light signaling stomata

Successful resuscitation after fatal carbon dioxide embolism during laparoscopic nephrectomy

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

Chinese Medical Journal 2014年第15期127卷 2863-2864页

作者： yu xin Fang xiao Fang Xiangming Department of Anaesthesiology the First Affiliated Hospital of Zhejiang University Hangzhou Zhejiang 310012 China

Laparoscopic nephrectomy （LN） is a less invasive surgical option for patients with renal ***,it may be complicated with disastrous CO2 embolism,which is rare but a life-threatening ***,we present a case of lethal CO2 embolism during ***,the complication was detected early and managed *** case and literature review all revealed that gas embolism must be considered as a possible cause of sudden cardiocirculatory failure during LN;rapid diagnosis and definitive intervention can decrease fatality from such an *** mechanisms of CO2 embolism and the potential ways of handling such an event are also ***：laparoscopic nephrectomy; gas embolism; transesophageal echocardiography

关键词： laparoscopic nephrectomy gas embolism transesophageal echocardiography

Expression and immunoreactivity of HCV/HBV epitopes

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2005年第41期11卷 6440-6444页

作者： xin-yu Xiong xiao Liu yuan-Ding Chen Institute of Medical Biology Chinese Academy of Medical Sciences and Peking Union Medical College Kunming 650118 Yunnan Province China

AIM： To develop the epitope-based vaccines to prevent Hepatitis C virus （HCV）/Hepatitis B virus （HBV） infections. METHODS： The HCV core epitopes C1 STNPKPQRKTKRNTNRRPQD （residuals aa2-21） and C2 VKFPGGGQIVGGVYLLPRR （residuals aa22-40）, envelope epitope E GHRMAWDMMMNWSP （residuals aa315-328） and HBsAg epitope S CTTPAQGNSMFPSCCCTKPTDGNC （residuals aa124-147） were displayed in five different sites of the flock house virus capsid protein as a vector, and expressed in E. coli cells （pET-3 system）. Immunoreactivity of the epitopes with anti-HCV and anti-HBV antibodies in the serum from hepatitis C and hepatitis B patients were determined. RESULTS： The expressed chimedc protein carrying the HCV epitopes C1, C2, E （two times）, L3C1-I2E-L1C2- L2E could react with anti-HCV antibodies. The expressed chimeric protein carrying the HBV epitopes S, I3S could react with anti-HBs antibodies. The expressed chimeric proteins carrying the HCV epitopes C1, C2, E plus HBV epitope S, L3C1-I2E-L1C2-L2E-I3S could react with anti- HCV and anti-HBs antibodies. CONCLUSION： These epitopes have highly specific and sensitive immunoreaction and are useful in the development of epitope-based vaccines.

关键词： HCV HBV Epitope-based vaccine Recombinant Xmmunoreactivity

Phenomenological study of the anisotropic quark matter in the two-flavor Nambu–Jona–Lasinio model

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

Nuclear Science and Techniques 2022年第11期33卷 170-190页

作者： He-Xia Zhang yu-xin xiao Jin-Wen Kang Ben-Wei Zhang Key Laboratory of Quark and Lepton Physics(MOE)and Institute of Particle Physics Central China Normal UniversityWuhan 430079China Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum MatterSouth China Normal UniversityGuangzhou 510006China

With the two-flavor Nambu–Jona–Lasinio (NJL) model, we carried out a phenomenological study on the chiral phase structure, mesonic properties, and transport properties of momentum-space anisotropic quark matter. To calculate the transport coefficients we utilized the kinetic theory in the relaxation time approximation, where the momentum anisotropy is embedded in the estimation of both the distribution function and relaxation time. It was shown that an increase in the anisotropy parameterξmay result in a catalysis of chiral symmetry breaking. The critical endpoint(CEP) is shifted to lower temperatures and larger quark chemical potentials asξincreases, and the impact of momentum anisotropy on the CEP temperature is almost the same as that on the quark chemical potential of the CEP. The meson masses and the associated decay widths also exhibit a significant ξ dependence. It was observed that the temperature behavior of the scaled shear viscosity η/T~3 and scaled electrical conductivity σ/T exhibited a similar dip structure, with the minima of both η/T~3 and σ/T shifting toward higher temperatures with increasing ξ. Furthermore,we demonstrated that the Seebeck coefficient S decreases when the temperature rises and its sign is positive, indicating that the dominant carriers for converting the temperature gradient to the electric field are up-quarks. The Seebeck coefficient S is significantly enhanced with a largeξfor a temperature below the critical temperature.

关键词： Heavy-ion collision Momentum anisotropy NJL model Chiral phase transition Transport coefficient Quark matter

Impact of vegetation restoration on hydrological processes in the middle reaches of the Yellow River,China

在线全文

学校读者我要写书评

暂无评论

Forestry Studies in China 2009年第4期11卷 209-218页

作者： xin Zhong-bao yu xin-xiao Key Laboratory of Soil and Water Conservation and Desertification Combating of the Ministry of Education Beijing Forest Univer-sity 100083 P. R. China

Sediment discharge from the Yellow River originates mainly from the drainage area between Hekouzhen and Longmen, i.e., the Helong area. Spatial-temporal variations of the vegetation cover in this area during the 1981-2007 period have been investigated using GIMMS and SPOT VGT NDVI data. We have also analyzed the interannual variations in vegetation cover and changes in annual runoff and sediment discharge, the consequences from precipitation change and the Grain for Green Project （GGP）. The results show that vegetation cover of the Helong area has increased during the 1981-2007 period. The northwestern part the Helong area, where the flat sandy lands are covered by grass, has experienced the largest increase. The region where the vegetation cover has declined is largely found in the southern and southeastern Helong area, which is a gullied hilly area or forested. Although precipitation was relatively low during the 1999-2007 period, the vegetation cover showed a significant increase in the Helong area, due to the implementation of the GGP. During this period, the most significant improvement in the vegetation cover occurred mainly in the gullied hilly areas of the Loess Plateau, such as the drainage basins of the Kuyehe and Tuweihe rivers and the middle and lower reaches of the Wudinghe and Yanhe rivers. A comparison of the average annual maximum NDVI between the earlier （1998-2002） stage and the next five years （2003-2007） of the GGP indicates that the areas with increases of 10% and 20% in NDVI account for 72.5% and 36.4% of the total area, respectively. Interannual variation of annual runoff and sediment discharge shows a declining trend, especially since the 1980s, when the decrease became very obvious. Compared with the 1950-1969 period, the average runoff during the 1980-2007 period was reduced by 34.8 × 10^8 m3 and the sediment discharge by 6.4 ×10^8 t, accounting for 49.4% and 64.9% of that in the 1950-1969 period, respectively. There is a positive correlati

关键词： middle reaches of the Yellow River Hekouzhen to Longmen area (Helong area) vegetation restoration Grain forGreen Project (GGP) runoff and sediment

A new phenylethanoid glycoside from Rabdosia lophanthoides(Buch.-*** ***) Hara.

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2009年第4期20卷 453-455页

作者： Wei Sheng Feng xin yu Zang xiao Ke Zheng Yan Zhi Wang Henan College of Traditional Chinese Medicine Zhengzhou 450008 China

A new phenylethanoid glycoside, 3-hydroxy-4-methoxy-β-phenylethoxy-O-α-L-rhamnopyranosyl-（1 → 3）-2-O-acetyl-O-β-D- glucopyranoside, named lophanthoside A, was isolated from Rabdosia lophanthoides （Buch.-*** ***... 详细信息

关键词： Rabdosia lophanthoides Lophanthoside A Phenylethanoid glycoside

Searching for Variable Stars in and around Open Clusters

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2002年第6期2卷 481-486页

作者： yu xin, xiao-Bin Zhang and Li-Cai DengNational Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 National Astronomical Observatories Chinese Academy of Sciences

We present a snapshot-of our recent results of a variable star survey in 1 degree fields around three open clusters: NGC 188, NGC 7789 and M67. A total number of 39 variable stars are newly discovered, including 22 W ... 详细信息

关键词： open clusters : individual : NGC 188, NGC 7789 and M67 stars : variables