检索结果-南通市图书馆

Threshold of climate extremes that impact vegetation productivity over the Tibetan Plateau

Science China Earth Sciences 2024年第6期67卷 1967-1977页

作者： Zhenggang PIAO Xiangyi LI Hao XU Kai WANG Shuchang TANG Fei KAN Songbai HONG College of Urban and Environmental Sciences Peking UniversityBeijing 100871China

Vegetation growth is adversely impacted by multiple climate extremes related to the water and thermal stress over the Tibetan Plateau(TP).However,it remains unknown at which stress level these climate extremes can trigger the abrupt shifts of vegetation response to climate extremes and result in the maximum vegetation response across TP.To fill this knowledge gap,we combined the hydrometeorological data and the satellite-derived vegetation index to detect two critical thresholds that determine the response of vegetation productivity to droughts,high-temperature extremes,and low-temperature extremes,respectively,during 2001-2018.Our results show that the response of vegetation productivity to droughts rapidly increases once crossing -1.41±0.6 standard deviation(σ)below the normal conditions of soil moisture.When crossing-2.98σ±0.9σ,vegetation productivity is maximum damaged by droughts.High-temperature extremes,which have the two thresholds of 1.34σ±0.4σand 2.31σ±0.4σover TP,are suggested to trigger the strong response of vegetation productivity at a milder stress level than low-temperature extremes(two thresholds:-1.44σ±0.5σand-2.53σ±0.8σ).Moreover,we found the compounded effects of soil moisture deficit in reducing the threshold values of both high-and low-temperature extremes.Based on the derived thresholds of climate extremes that impact vegetation productivity,Earth System Models project that southwestern TP and part of the northeastern TP will become the hotspots with a high exposure risk to climate extremes by 2100.This study deciphers the high-impact extreme climates using two important thresholds across TP,which advances the understanding of the vegetation response to different climate extremes and provides a paradigm for assessing the impacts of climate extremes on regional ecosystems.

关键词： Tibetan Plateau Climate extremes thresholds Vegetation productivity

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

Behavioral and neural auditory thresholds in a frog

引用

Current Zoology 2019年第3期65卷 333-341页

作者： Ryan C.TAYLOR Karin AKRE Walter WILCZYNSKI Michael J.RYAN Department of Integrative Biology University of Texas at Austin Austin TX USA Department of Biological Sciences Salisbury University Salisbury MD USA Smithsonian Tropical Research Institute Balboa Republic of Panama Neuroscience Institute and Center for Behavioral Neuroscience Georgia State University Atlanta GA USA

Vocalizations play a critical role in mate recognition and mate choice in a number of taxa, especially, but not limited to, orthopterans, frogs, and birds. But receivers can only recognize and prefer sounds that they can hear. Thus a fundamental question linking neurobiology and sexual selection asks-what is the threshold for detecting acoustic sexual displays? In this study, we use 3 methods to assess such thresholds in tdngara frogs: behavioral responses, auditory brainstem responsesz and multi unit electrophysiological recordi ngs from the midbrain.We show that thresholds are lowest for multiunit recordings (ca. 45 dB SPL), and then for behavioral responses (ca. 61 dB SPL), with auditory brainstem responses exhibiting the highest thresholds (ca. 71 dB SPL). We discuss why these estimates differ and why, as with other studies, it is unlikely that they should be the same. Although all of these studies estimate thresholds they are not measuring the same thresholds;behavioral thresholds are based on signal salienee whereas the 2 neural assays estimate physiological thresholds. All 3 estimates, however, make it clear that to have an appreciation for detection and salienee of acoustic signals we must listen to those signals through the ears of the receivers.

关键词： anurans auditory brainstem responses auditory thresholds mate choice Physalaemus pustulosus signal recog nition thresholds sexual selection tungara frogs vocalizations

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

Probabilistic rainfall thresholds in Chibo, India: estimation and validation using monitoring system

引用

Journal of Mountain Science 2019年第4期16卷 870-883页

作者： Abhirup DIKSHIT Neelima SATYAM Discipline of Civil Engineering Indian Institute of Technology Indore Simrol

The Himalayan region has been severely affected by landslides especially during the monsoons. In particular, Kalimpong region in Darjeeling Himalayas has recorded several landslides and has caused significant loss of life, property and agricultural land. The study region, Chibo has experienced several landslides in the past which were mainly debris and earth slide. Globally, several types of rainfall thresholds have been used to determine rainfall-induced landslide incidents. In this paper, probabilistic thresholds have been defined as it would provide a better understanding compared to deterministic thresholds which provide binary results, i.e., either landslide or no landslide for a particular rainfall event. Not much research has been carried out towards validation of rainfall thresholds using an effective and robust monitoring system. The thresholds are then validated using a reliable system utilizing Microelectromechanical Systems(MEMS) tilt sensor and volumetric water content sensor installed in the region. The system measures the tilt of the instrument which is installed at shallow depths and is ideal for an early warning system for shallow landslides. The change in observed tilt angles due to rainfall would give an understanding of the applicability of the probabilistic model. The probabilities determined using Bayes' theorem have been calculated using the rainfall parameters and landslide data in 2010-2016. The rainfall values were collected from an automatic rain gauge setup near the Chibo region. The probabilities were validated using the MEMS based monitoring system setup in Chibo for the monsoon season of 2017. This is the first attempt to determine probabilities and validate it with a robust and effective monitoring system in Darjeeling Himalayas. This study would help in developing an early warning system for regions where the installation of monitoring systems may not be feasible.

关键词： Early warning Probabilistic thresholds Kalimpong 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

Optimized energy thresholds in a spectral computed tomography scan for contrast agent imaging

引用

Nuclear Science and Techniques 2019年第3期30卷 15-27页

作者： Kai-Xin Huang Zhi Deng Xiao-Fei Xu Yu-Xiang Xing Department of Engineering Physics Tsinghua University Key Laboratory of Particle and Radiation Imaging Ministry of Education Tsinghua University

Spectral computed tomography(CT) based on photon counting detectors(PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefully selected, especially for K-edge imaging, which is an important spectral CT application. This paper presents a threshold selection method that yields better-quality images in K-edge imaging. The main idea is to optimize the energy thresholds ray-by-ray according to the targeted component coefficients, followed by obtaining an overall optimal energy threshold by frequency voting. A low-dose pre-scan is used in practical implementations to estimate the line integrals of the component coefficients for the basis functions. The variance of the decomposed component coefficients is then minimized using the Cramer–Rao lower bound method with respect to the energy thresholds. The optimal energy thresholds are then used to take a full scan and gain better image reconstruction with less noise than would be given by a full scan using the non-optimal energy thresholds. Simulations and practical experiments on imaging iodine and gadolinium solutions, which are commonly used as contrast agents in medical applications, were used to validate the method. The noise was significantly reduced with the same dose relative to the non-optimal energy thresholds in both simulations and in practical experiments.

关键词： Spectral CT Contrast agent imaging Cramer-Rao lower bound thresholds optimization Kedge

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

Impairment of extra-high frequency auditory thresholds in subjects with elevated levels of fasting blood glucose

引用

Journal of Otology 2018年第1期13卷 29-35页

作者： Anindya Das Ahmed Faisal Sumit Nazmul Ahsan Masashi Kato Nobutaka Ohgami Anwarul Azim Akhand Department of Genetic Engineering and Biotechnology University of Dhaka Dhaka Bangladesh BRAC James P Grant School of Public Health BRAC University Dhaka Bangladesh Department of Occupational and Environmental Health Nagoya University Graduate School of Medicine Nagoya Japan

This study was performed to assess whether there is an association between elevated Fasting Blood Glucose(FBG) and hearing impairment in Bangladeshi population. A total of 142 subjects(72 with elevated FBG; 70 control) were included in the study. The mean auditory thresholds of the control subjects at 1,4,8 and 12 kHz frequencies were 6.35 ± 0.35,10.07 ± 0.91,27.57 ± 1.82, 51.28 ± 3.01 dB SPL(decibel sound pressure level), respectively and that of the subjects with elevated FBG were 8.33 ± 0.66,14.37 ± 1.14, 38.96 土 2.23, and 71.11 ± 2.96 dB.respectively. The auditory thresholds of the subjects with elevated FBG were significantly(p 10 years) showed significantly(p thresholds at 8 and 12 kHz, but not at 1 and 4 kHz frequencies,compared to subjects with shorter duration of diabetes(≤10 years). In addition, based on the data of odds ratio, more acute impairment of hearing at the extra-high frequency was observed in diabetic subjects of both older(>40 years) and younger(<40 years) age groups compared to the respective controls. The binary logistic regression analysis showed a 5.79-fold increase in the odds of extra-high frequency hearing impairment in diabetic subjects after adjustment for age, gender and BMI. This study provides conclusive evidence that auditory threshold at an extra-high frequency could be a sensitive marker for hearing impairment in diabetic subjects.

关键词： Fasting blood glucose Hearing impairment Auditory thresholds Extra-high frequency

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

A STUDY ON thresholds IN THE CHANGE OF ALLUVIAL FAN AND DELTA OF THE HUANGHE RIVER, CHINA

引用

Chinese Geographical Science 1991年第3期1卷 68-77页

作者：曹银真

In the river systems, the environmental change always undergoes a process from quantitative to qualitative change. The upper limit of the qualitative change is called threshold. When the process reaches or goes beyond the limit, the original event series will be replaced by the other event series. Investigations show that the evolution of the Huanghe River alluvial fan and delta has also under gone a process from quantitative to qualitative change. The geometric forms in each process are roughly the same. This threshold of the geometric forms not only provides us a quantitative index for plotting the periodicity of the alluvial fan and delta, but also is of importance for estimation of the trend of natural environmental change.It is shown that there are three periodic alluvial fans of the Huanghe River since the middle Holocene and four periodic delta since 1855 A.D., the thresholds of their geometric forms are from 0.93 to 0.94 and from 1.2 to 1.21 respectively.The changing trend in the past and the

关键词： alluvial fan Huanghe River delta thresholds Breach and Changing Course

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

Muscle strength cut-offs for the detection of metabolic syndrome in a nonrepresentative sample of collegiate students from Colombia

引用

Journal of Sport and Health Science 2020年第3期9卷 283-290页

作者： Antonio Garcia-Hermoso Alejandra Tordecilla-Sanders Jorge Enrique Correa-Bautista Mark D.Peterson Mikel Izquierdo Aura Cristina Quino-ávila Carolina Sandoval-Cuellar Katherine González-Ruíz Robinson Ramíez-Vélez Physical Activity Sport and Health Sciences LaboratoryUniversity of Santiago de ChileSantiago de Chile 7500618Chile Center of Studies in Physical Activity Measurements School of Medicine and Health SciencesUniversidad del RosarioBogot a 111221Colombia Department of Physical Medicine and Rehabilitation University of MichiganAnn ArborMichigan 48109USA Department of Health Sciences Public University of NavarreCIBERFES(CB16/10/00315)Navarre 31009Spain CORPS Group Faculty of Health SciencesUniversity of BoyacáBoyac aTunja 153610Colombia Physical Exercise and Sports Research Group Manuela Beltrán UniversityBogot a 111221Colombia

Background: Evidence shows an association between grip strength and health;however, grip strength cut-offs for the detection of metabolic syndrome(MetS) in Latin American populations are scarce. The purpose of this study was to determine cut-offs of normalized grip strength(NGS)for the detection of MetS in a large nonrepresentative sample of a collegiate student population from Colombia.Methods: A total of 1795 volunteers(61.4% female;age = 20.68 ± 3.10 years, mean ± SD), ranging between 18 and 30 years of age participated in the study. Strength was estimated using a handheld dynamometer and normalized to body mass(handgrip strength(kg)/body mass(kg)). Anthropometrics, serum lipids indices, blood pressure, and fasting plasma glucose were measured. Body composition was measured by bioelectrical impedance analysis. MetS was defined as including ≥3 of the 5 metabolic abnormalities according to the International Diabetes Federation definition. A metabolic risk score was computed from the following components: waist circumference, triglycerides, high-density lipoprotein cholesterol, glucose, and systolic and diastolic blood pressure.Results: Receiver operating curve analysis showed significant discriminatory accuracy of NGS in identifying the thresholds and risk categories.Lower strength was associated with increased prevalence of MetS. In males, weak, intermediate, and strong NGS values at these points were0.615, respectively. In females, these cut-off points were 0.437, respectively.Conclusion: Our sex-specific cut-offs of NGS could be incorporated into a clinical setting for identifying college students at cardiometabolic disease risk.

关键词： Cardiometabolic risk Muscular fitness Receiver operating characteristic curve thresholds

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

Effect of Paired Associative Stimulation on Motor Cortex Excitability in Rats

引用

Current Medical Science 2018年第5期38卷 903-909页

作者： Xiang-yu ZHANG Yan-fang SUI Tie-cheng GUO Sai-hua WANG Yan HU Yin-shan LU Department of Rehabilitation Medicine Tongji HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430030China Department of Rehabilitation Medicine the 5th Hospital of Zhengzhou UniversityZhengzhou 470000China Department of Rehabilitation Medicine the 1st People's Hospital of HaikouHaikou 570208China Department of Rehabilitation Medicine the 1st Hospital of WuhanWuhan 430022China Department of Rehabilitation Medicine Zhongnan HospitalWuhan UniversityWuhan 430071China

Paired associative stimulation (PAS),combining transcranial magnetic stimulation (TMS) with electrical peripheral nerve stimulation (PNS) in pairs with an optimal interstimulus interval (ISI)in between,has been shown to influence the excitability of the motor cortex (MC)in humans.However,the underlying mechanisms remain unclear.This study was designed to explore an optimal protocol of PAS,which can modulate the excitability of MC in rats,and to investigate the underlying mechanisms. The resting motor thresholds (RMTs) of TMS-elicited motor evoked potentials (MEPs) recorded from the gastrocnemius muscle and the latency of P1 component of somatosensory evoked potentials (SEPs) induced by electrical tibial nerve stimulation were determined in male Sprague-Dawley rats (n=10).Sixty rats were then randomly divided into 3 groups:a PAS group (further divided into 10 subgroups at various ISIs calculated by using the latency of P1,n=5,respectively),a TMS (only)group (n=5)and a PNS (only)group (n=5).Ninety repetitions of PAS,TMS and PNS were administered to the rats in the 3 groups,respectively,at the frequency of 0.05 Hz and the intensity of TMS at 120% RMT and that of PNS at 6 mA.RMTs and motor evoked potentials'amplitude (MEPamp)were recorded before and immediately after the interventions.It was found that the MEPamp significantly decreased after PAS at ISI of 5 ms (P0.05).PAS at other ISis as well as the sole use of TMS and PNS induced no remarkable changes in MEPamp and RMT.In conclusion,PAS can influence motor cortex excitability in rats.Neither TMS alone nor PNS alone shows significant effect.

关键词： paired associative stimulation transcranial magnetic stimulation peripheral nerves electrical stimulation resting motor thresholds motor evoked potentials somatosensory evoked potentials

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

A Model to Estimate the Impact of thresholds and Caps on Coverage Levels in Community-Based Health Insurance Schemes in Low-Income Countries

引用

Health 2014年第9期6卷 822-835页

作者： Erika Binnendijk Ruth Koren David M. Dror Felsenstein Medical Research Center Sackler Faculty of Medicine Tel Aviv University Tel Aviv Israel Institute of Health Policy and Management Erasmus University Rotterdam Rotterdam The Netherlands Micro Insurance Academy New Delhi India

Background: Community-based health insurance (CBHI) schemes are increasingly implemented in low-income settings. These schemes limit the coverage they offer both by the types of care considered, and by applying thresholds and/or caps to costs reimbursed. The consequences of these thresholds and/or caps on insurance coverage have hitherto been usually ignored, for lack of data on the distributions of healthcare costs or understanding of their impact on effective coverage levels. This article describes a theoretical model to obtain the distributions even without data collection in the field, and demonstrates the quantitative impact of thresholds and/or caps on claim reimbursements. Methods: This model applies to applications on healthcare expenditures in low-income settings, following research methods examined in the Western world. We looked at hospitalizations and tests;we compared the simulated distributions to empirical data obtained through 11 household surveys conducted between 2008 and 2010 in rural locations (9 in India and 2 in Nepal). Results: We found that the shape of the distributions was very similar in all locations for both benefits, and could be represented by a model based on a lognormal distribution. The agreement between theoretical and empirical results was satisfactory (mostly within 10% difference). Conclusions: The model makes it possible to simulate the expected performance of the CBHI (represented by the percentage of costs or bills covered). The aim is to match costs with local levels of willingness-to-pay for health insurance. This model makes it possible to determine at the stage of package-design the optimal levels of thresholds and/or caps for each benefit-type included.

关键词： Distributions Healthcare Costs Community-Based Health Insurance Micro Health Insurance thresholds Caps

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

Probabilistic Rainfall thresholds for Landslide Episodes in the Sierra Norte De Puebla, Mexico

引用

Natural Resources 2017年第3期8卷 254-267页

作者： Alejandra González Ernesto Caetano Institute of Geography National Autonomous University of Mexico Mexico City Mexico

The Sierra Norte de Puebla, Mexico, has a record of hundreds of mass removal processes triggered by rainfall, where the intensity and duration of the rain are the main mechanisms. In order to determine threshold values for precipitation as a cause of a landslide, the prior, marginal and conditional probabilities were calculated. A Bayesian method was used for one-dimensional (precipitation intensity) and two-dimensional (precipitation intensity and duration) analysis. This suggested a high probability of mass movement when the precipitation exceeds 60 mm within ten days. A proposed warning system is based on classes in which the threshold is exceeded.

关键词： Processes of Mass Removal thresholds Probability Bayesian Method Sierra Norte De Puebla

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：