期刊文献+
共找到10,323篇文章
< 1 2 250 >
每页显示 20 50 100
Two-dimensional numerical simulation of sediment transport usingimproved critical shear stress methods 预览
1
作者 Zhiyong Feng Guangming Tan +3 位作者 Junqiang Xia Caiwen Shu Peng Chen Ran Yi 《国际泥沙研究:英文版》 SCIE 2020年第1期15-26,共12页
Research on the critical shear stresses for erosion and deposition for cohesive sediment has attracted substantial attention from both engineering and theoretical viewpoints due to their importance in sediment transpo... Research on the critical shear stresses for erosion and deposition for cohesive sediment has attracted substantial attention from both engineering and theoretical viewpoints due to their importance in sediment transport theory.Previous studies have proposed a large number of empirical and semiempirical methods to estimate the critical erosion and deposition shear stress,but comparative analyses and validation of the existing methods are still lacking,leaving questions regarding the applicability ranges of the methods.The current paper evaluates the performance and applicability range of five critical erosion shear stress methods derived from different hypotheses on sediment transport for flume experiments and natural tidal rivers using a process-based model.In addition,the effect of the critical deposition shear stress on sediment transport is investigated.The results show that the different critical erosion shear stress methods yield distinctly different prediction results,and their performance and applicability ranges are discussed by comparing their predictions with measured sediment concentrations from the Shenzhen River and measured geometric changes from the Partheniades'flume experiment.The hiding and exposure effect has been recognized as a crucial factor in the incipient motion of sediment on nonuniform beds.A sensitivity analysis of selective deposition and continuous deposition justifies the existence of the critical deposition shear stress.The current study highlights the performance and applicability ranges of the existing critical shear stress methods in sediment transport modeling for uniform and nonuniform beds,which will enrich understanding of the underlying mechanisms of erosion and deposition of cohesive sediment. 展开更多
关键词 Cohesive sediment Critical shear stress Hiding and exposure effect Numerical modeling Shenzhen river
在线阅读 下载PDF
Exposure of the Population of Ngaoundere-Cameroon to Ionizing Radiation Related to Medical Diagnosis in 2018 预览
2
作者 Mathurin Neossi Guena Baudouin Djoumessi Nanfack Joseph Gonsu Fotsing 《放射学期刊(英文)》 2019年第2期125-138,共14页
Background: Medical applications are the main source of exposure to ionizing radiation of human origin. Our objective was to determine the data on exposure to ionizing radiation of medical origin of the population of ... Background: Medical applications are the main source of exposure to ionizing radiation of human origin. Our objective was to determine the data on exposure to ionizing radiation of medical origin of the population of Ngaoundéré in 2018. Methodology: It was a cross-sectional descriptive study conducted within a period of one year, in the different hospitals of Ngaoundéré, with a functional medical imaging service. The variables studied were age, sex, type of examination, anatomical region and effective dose. The statistical analysis was performed using the Microsoft Office 2016 software, Sphinx V5;the effective dosage was calculated using the Internet Dose calculation Module. Results: In 2018, 4136 diagnostic acts using ionizing radiation were carried out;it concerned only conventional radiology with an average of 0.02 per capita. The total collective dose received by the population was 8300 mSv, and an average dose of 0.040 mSv per inhabitant. The proportion of the population that has actually benefited from a conventional radiology examination is 2.07%, an individual effective average dose of 2 mSv. The most frequent acts involved the thorax, limbs, spine and pelvis with respectively 53.9%;19.6%;14.3% and 6.7%. Acts involving the spine, pelvis and hip, skull and abdomen contributed to the majority of the collective effective dose respectively with 45.75%, 25.96%, 10.53% and 8.84%. The age group performing most exams in men is 25 to 49 and 25 to 54 in women;the number of acts is higher among men 2457 (59.4%) acts compared to women 1679 (40.6%) acts. The collective dose per sex is higher among women with 4487.22 mSv (54.06%) compared to men with 3812.98 mSv (45.94%). Conclusion: Only 2.07% of population of Ngaoundere benefited from a conventional radiology examination in 2018 with an individual effective average dose of 2 mSv. The annual per capita number of acts is 0.02 and annual per capita effective dose is 0.040 mSv in Ngaoundéré in 2018. 展开更多
关键词 EXPOSURE Ionizing Radiation CONVENTIONAL RADIOLOGY City of Ngaoundéré 2018
在线阅读 免费下载
上海市嘉定区35253例狂犬病暴露病例流行病学分析 预览
3
作者 张英 印庆华 杨玲玲 《中国临床医学》 2019年第2期315-317,共3页
狂犬病是由狂犬病病毒感染引起的一种动物源性传染病,临床大多表现为特异性恐风、恐水、咽肌痉挛、进行性瘫痪等症状。近年来,狂犬病报告死亡数一直位居我国法定报告传染病前列,给人们生命健康带来了严重威胁[1]。狂犬病一旦发病,病死率... 狂犬病是由狂犬病病毒感染引起的一种动物源性传染病,临床大多表现为特异性恐风、恐水、咽肌痉挛、进行性瘫痪等症状。近年来,狂犬病报告死亡数一直位居我国法定报告传染病前列,给人们生命健康带来了严重威胁[1]。狂犬病一旦发病,病死率达100%,目前尚无有效治疗该病的方法[2]。目前,印度和我国狂犬病报告发病数仍居全球前2位[3],我国狂犬病每10年出现1个小流行周期,20年左右出现1个大流行周期。1990—2007年是中国狂犬病第3个大流行周期,发病率呈先下降后上升的倒抛物线趋势,2008—2014年再行走低[4]。第3次疫情高峰后,我国采取了一系列措施,取得了较为显著的防治效果[5]。本研究对上海市嘉定区2017—2018年35 253名狂犬病暴露就诊人群的暴露特征及暴露后预防(post-exposure prophylaxis,PEP)处置情况进行分析,以便采取更有效地防控措施,以避免或降低狂犬病发生的风险。 展开更多
关键词 狂犬病 暴露 免疫接种 流行病学 暴露后预防
在线阅读 免费下载
Power Stripping of Asbestos-Containing Insulation from Electrical Cable 预览
4
作者 Charles L. Blake Giffe T. Johnson Raymond D. Harbison 《职业病与环境医学(英文)》 2019年第3期65-74,共10页
Efforts to recycle copper from electrical conductors have led to the development of specialized machines, which automatically remove insulating covers from wires and cable products. In the past, certain wire and cable... Efforts to recycle copper from electrical conductors have led to the development of specialized machines, which automatically remove insulating covers from wires and cable products. In the past, certain wire and cable products were insulated using chrysotile asbestos. This research was undertaken to determine the asbestos fiber exposure risks associated with power stripping machinery to remove asbestos-containing insulation materials from electrical wire or cable. A Rigby Machinery, Inc., Model 4H electric powered wire/cable insulation stripping machine was acquired along with approximately 42 m of asbestos insulated cable. During two separate, but nearly identical, test sessions, a laborer used the wire stripper to remove the asbestos-containing insulation from the subject cable. This work took place within a closed metal building with a total interior volume of 2500 m3. Industrial hygiene personal and area air samples were collected for airborne fibers throughout all wire stripping periods. Collected air samples were analyzed using phase contract microscopy (PCM) and transmission microscopy (TEM). The results of analysis using PCM for personal samples (n = 3) taken during periods of continuous cable stripping activity showed test period airborne fiber exposures ranging from 0.034 to 0.068 (mean 0.056 f/cc). Follow-up analysis of these personal samples using TEM indicated asbestos adjusted PCM exposures ranging from 0.017 to 0.045 (mean 0.033 f/cc). Area air samples taken at distances ranging from 2 to 9 meters from the wire stripper (n = 16) showed asbestos adjusted PCM concentrations ranging from less than 0.0001 to 0.041 f/cc (mean 0.007 f/cc). The process of power stripping asbestos-containing insulation from electrical wires and cables can cause exposure to airborne asbestos fibers. However, the levels of such exposure are not expected to exceed the current occupational exposure limits for asbestos of 0.1 f/cc as an 8-hr TWA or 1.0 f/cc averaged over a 30-minute exposure period. 展开更多
关键词 Asbestos Exposure Insulating COVERS POWER STRIPPING ELECTRICAL Wire CHRYSOTILE Asbestos Asbestos Fibers Asbestos-Related Disease Asbestos-Containing Material
在线阅读 免费下载
Evaluation of Asbestos Exposure Associated with Research Laboratories 预览
5
作者 Ediberto Garcia Daniel Newfang +2 位作者 Jayme Coyle Giffe T. Johnson Raymond D. Harbison 《职业病与环境医学(英文)》 2019年第1期13-20,共8页
Asbestos containing materials (ACM) have been used for decades in research laboratory products including gloves, tong sleeves, Transite board, and other materials. These materials typically contain chrysotile asbestos... Asbestos containing materials (ACM) have been used for decades in research laboratory products including gloves, tong sleeves, Transite board, and other materials. These materials typically contain chrysotile asbestos with concentrations ranging up to 80%. The objective of this research was to evaluate asbestos exposure from gloves, tong sleeves, and Transite board with simulated laboratory use. An environmental chamber was used to simulate laboratory application of the products. Bulk samples of various products were tested before and after use. Personal breathing zone air samples as well as one cumulative air sample were collected during testing and followed the National Institute for Occupational Safety and Health (NIOSH) 7400/7402 methodologies. Phase contrast microscopy (PCM) and transmission electron microscopy (TEM) were used for sample analyses. Analysis of air samples using PCM, showed airborne fiber concentrations as high as 0.058 f/cc during use of tongs fitted with asbestos sleeves. Further analysis using TEM showed that the highest airborne fiber concentration was 0.0036 f/cc. Manipulation of Transite board resulted in 8-hour time-weighted-average (TWA) asbestos levels as high as 0.02 f/cc. Testing of various asbestos containing materials used in research laboratories indicate low potential for asbestos fiber exposures. 展开更多
关键词 Asbestos EXPOSURE Research LABORATORIES Transite Board Tong Sleeves GLOVES CHRYSOTILE Asbestos Laboratory Products Asbestos-Related Disease Asbestos-Containing Material
在线阅读 免费下载
Electromagnetic Radiation Exposure from Nearby Cellular Base Stations in the Gaza Strip, Palestine: A Concern for Public Health 预览
6
作者 Samir Yassin Mohammed Musleh Samer Abuzerr 《生物科学与医学(英文)》 2019年第4期46-59,共14页
The widespread mobile station’s antennas and the continued increase in the number of mobile phones users throughout the Gaza strip causing great panic in the population relating the debate overexposure to electromagn... The widespread mobile station’s antennas and the continued increase in the number of mobile phones users throughout the Gaza strip causing great panic in the population relating the debate overexposure to electromagnetic radiation EMR emitted from the antennas of mobile base stations. Therefore, this study was conducted to measure the levels of electromagnetic radiation emitted from the antennas of cellular base stations in Gaza governorate as well as to evaluate the citizen’s awareness and practices regarding potential health risks and mitigation methods of exposure to electromagnetic radiation emitted from cellular base stations, respectively. Fifty cellular base stations out of 197 stations were selected depending on the criteria of selecting one site per kilometer using Global Positioning System (GPS). Electromagnetic power density, electric field strength, and the magnetic field strength emitted from cellular base stations were measured using Narda-550. Assessment tool for observation was used to collect operational information of each station. A structured questionnaire with four-level Likert rating scale was used to survey 384 mobile phone users from the areas surrounding the selected cellular base stations. The results showed that the electromagnetic radiation levels of all stations were low and less than the national and international acceptable limits. Furthermore, the awareness of participant about health risks that could result from exposure to electromagnetic radiation emitted from cellular base stations and mobile phones was low. Nevertheless, the participant’s practices in mitigating the adverse impacts of electromagnetic radiation emitted from cellular base stations and mobile phones on their health were good. 展开更多
关键词 ANTENNAS CELLULAR Base Stations Exposure ELECTROMAGNETIC Radiation GAZA Strip Public Health Power Density
在线阅读 免费下载
室内空气甲醛污染相关问题研究进展
7
作者 梁雪松 殷明杰 +2 位作者 刘晓秋 道书润 赵瑞 《中国公共卫生管理》 2019年第3期343-348,共6页
室内空气甲醛污染问题已成为全球的公共卫生问题,受到各国的重视和人们的普遍关注。此文以近年知网和Pubmed等数据库研究报道为基础,对室内空气甲醛污染相关报道情况进行分析,从室内空气中甲醛的危害、室内空气中甲醛的来源与暴露和室... 室内空气甲醛污染问题已成为全球的公共卫生问题,受到各国的重视和人们的普遍关注。此文以近年知网和Pubmed等数据库研究报道为基础,对室内空气甲醛污染相关报道情况进行分析,从室内空气中甲醛的危害、室内空气中甲醛的来源与暴露和室内空气中甲醛去除方法三个方面进行综述。对甲醛危害方面主要就甲醛致癌、导致白血病、导致过敏及其他毒性四个方面进行总结;在甲醛来源与暴露方面就家居装修、室内气体燃烧不完全和职业暴露等几方面对文献进行梳理;在甲醛消除方面主要总结吸附剂吸附法、光催化方法和植物吸附法等方法,为室内空气甲醛污染的防治提供借鉴。 展开更多
关键词 室内空气 环境卫生 空气污染 污染物 甲醛 毒性 暴露 空气净化
Preparation of Molecularly Imprinted Composites Initiated by Hemin/Graphene Hybrid Nanosheets and Its Application in Detection of Sulfamethoxazole 预览
8
作者 Shao-fei GUO Xiao-yu CHEN +4 位作者 Peng WANG Cheng CHEN Rui-hua PAN Yue-tao LING Yi-zhu TANG 《当代医学科学(英文)》 SCIE CAS 2019年第1期159-165,共7页
Molecularly imprinted polymers(MIPs)exhibit high selectivity resulting from imprinted cavities and superior performance from functional materials,which have attracted much attention in many fields.However,the combinat... Molecularly imprinted polymers(MIPs)exhibit high selectivity resulting from imprinted cavities and superior performance from functional materials,which have attracted much attention in many fields.However,the combination of MIPs film and functional materials is a great challenge.In this study,hemin/graphene hybrid nanosheets(H-GNs)were used to initiate the imprinted polymerization by catalyzing the generation of free radicals.Thus,MIPs using sulfamethoxazole as the template was directly prepared on the surface of H-GNs without any film modification.Most importantly,the template could be absorbed on the H-GNs to enhance the number of imprinted sites per unit surface area,which could improve the selectivity of MIPs film.Thus,the composites could exhibit high adsorption capacity(29.4 mg/g),imprinting factor(4.2)and excellent conductivity,which were modified on the surface of electrode for rapid,selective and sensitive detection of sulfamethoxazole in food and serum samples.The linear range was changed from 5μg/kg to 1 mg/g and the limit of detection was 1.2μg/kg.This sensor was free from interference caused by analogues of sulfamethoxazole,which provides a novel insight for the preparation of MIPs-based sensor and its application in food safety monitoring and human exposure study. 展开更多
关键词 MIP/H-GNs COMPOSITES SULFAMETHOXAZOLE nano enzyme-mediated polymerization sensor DIETARY exposure
在线阅读 下载PDF
Exposures to temperature beyond threshold disproportionately reduce vegetation growth in the northern hemisphere
9
作者 Xiuchen Wu Weichao Guo +13 位作者 Hongyan Liu Xiaoyan Li Changhui Peng Craig D.Allen Cicheng Zhang Pei Wang Tingting Pei Yujun Ma Yuhong Tian Zhaoliang Song Wenquan Zhu Yang Wang Zongshan Li Deliang Chen 《国家科学评论:英文版》 CSCD 2019年第4期786-795,共10页
In recent decades,terrestrial vegetation in the northern hemisphere(NH)has been exposed to warming and more extremely high temperatures.However,the consequences of these changes for terrestrial vegetation growth remai... In recent decades,terrestrial vegetation in the northern hemisphere(NH)has been exposed to warming and more extremely high temperatures.However,the consequences of these changes for terrestrial vegetation growth remain poorly quantifed and understood.By examining a satellite-based vegetation index,tree-ring measurements and land-surface model simulations,we discovered a consistent convex patern in the responses of vegetation growth to temperature exposure(TE)for forest,shrub and grass in both the temperate(30°-50°N)and boreal(50°-70°N)NH during the period of 1982-2012.Te response of vegetation growth to TE for the three vegetation types in both the temperate and boreal NH increased convergently with increasing temperature,until vegetation type-dependent temperature thresholds were reached.A TE beyond these temperature thresholds resulted in disproportionately weak positive or even strong negative responses.Vegetation growth in the boreal NH was more vulnerable to extremely high-temperature events than vegetation growth in the temporal NH.Te non-linear responses discovered here provide new insights into the dynamics of northern terrestrial ecosystems in a warmer world. 展开更多
关键词 TEMPERATURE exposure vegetation growth EXTREMELY high TEMPERATURE non-linear response TEMPERATE and BOREAL northern HEMISPHERE
X射线床旁摄片场所电离辐射水平和防护效果研究
10
作者 陈飚 陈春晖 +2 位作者 高林峰 姚杰 肖虹 《中国辐射卫生》 2019年第2期135-138,共4页
目的研究X射线床旁摄片场所电离辐射水平和采取干预措施后的防护效果,为管理部门进一步制订管理标准提供依据。方法在上海市9个区随机抽取12家医疗机构的15台X射线床旁摄影机,模拟日常病房开展床旁摄影的场景,对观察点X射线周围剂量当... 目的研究X射线床旁摄片场所电离辐射水平和采取干预措施后的防护效果,为管理部门进一步制订管理标准提供依据。方法在上海市9个区随机抽取12家医疗机构的15台X射线床旁摄影机,模拟日常病房开展床旁摄影的场景,对观察点X射线周围剂量当量率进行检测和评估。结果在本研究所关注的范围内,床旁摄片场所X射线周围剂量当量率均超过本底值;不同设备(包括同型号但使用环境不同的设备)在相近的常规曝光条件产生的散射线剂量率差异较大,无防护屏场所的X射线周围剂量当量率在3.9 μSv/h至5 800 μSv/h之间;使用防护屏场所的X射线周围剂量当量率在0.095 μSv/h至22.1 μSv/h之间,明显低于无屏风的场所,铅当量高的防护屏具有更好的防护效果。结论不同型号的X射线床旁摄片机,自身防护性能差异较大,导致工作场所放射防护剂量的差别,购置防护性能好的设备、小心使用、做好维护保养工作等是降低X射线剂量的重要保障;开展床旁摄片时应当尽量疏散毗邻床位的病人、医务人员、探视家属等公众,对无法疏散的公众,建议使用便捷且实用的移动式防护屏。 展开更多
关键词 X射线 床旁摄片 剂量率 曝光
Historical Trajectories of Disaster Risk in Dominica
11
作者 Jenni Barclay Emily Wilkinson +8 位作者 Carole S.White Clare Shelton Johanna Forster Roger Few Irene Lorenzoni George Woolhouse Claire Jowitt Harriette Stone Lennox Honychurch 《国际灾害风险科学学报:英文版》 CSCD 2019年第2期149-165,共17页
The calamitous consequences of 2017 Hurricane Maria for the Caribbean island of Dominica highlighted the acute and increasing susceptibility of the region to disasters. Despite increasing international attention to di... The calamitous consequences of 2017 Hurricane Maria for the Caribbean island of Dominica highlighted the acute and increasing susceptibility of the region to disasters. Despite increasing international attention to disaster risk reduction, recovery from hazard events can be especially lengthy and difficult for small island developing states. In this article, we build on existing understandings of disaster risk as a physical and social condition, showing that historical processes are fundamental to understanding how conditions of risk emerge and persist over time. We take an integrated approach to analyzing the drivers of risk accumulation, using the example of Dominica, where processes set in motion during the colonial period have shaped the location of people and assets, the degree to which they might be harmed, the societal repercussions of that harm and the prospects for recovery. We focus on the underlying economic vulnerabilities and physical exposure to hazards created by agricultural, economic, and social practices, and successive disaster responses that have constrained recovery. Uncovering these historical drivers and persistent issues, elucidates lessons for pursuing a more resilient development trajectory, including through the promotion of economic restructuring and diversification, and land reform. 展开更多
关键词 DOMINICA HISTORICAL trajectories Natural hazards RESILIENCE Risk EXPOSURE Small ISLAND developing STATES
谈局部厚铜板的制作流程 预览
12
作者 蒋华 张宏 +2 位作者 何艳球 张亚锋 郭宇 《印制电路信息》 2019年第10期51-56,共6页
局部厚铜板在生产过程中,需要重点管控局部厚铜板的蚀刻深度、半固化片(PP)开窗尺寸设计及残胶、底片曝光的吸真空度及压合失压、缺胶、铜箔起皱等问题。文章主要通过对局部厚铜板的生产流程进行研究,并总结出一种能适合此类型板批量生... 局部厚铜板在生产过程中,需要重点管控局部厚铜板的蚀刻深度、半固化片(PP)开窗尺寸设计及残胶、底片曝光的吸真空度及压合失压、缺胶、铜箔起皱等问题。文章主要通过对局部厚铜板的生产流程进行研究,并总结出一种能适合此类型板批量生产的制作流程。 展开更多
关键词 局部厚铜 控深蚀刻 压合 曝光 汽车板
在线阅读 下载PDF
E-noise: An increasingly relevant health risk
13
作者 Chun-song Hu Tengiz Tkebuchava 《结合医学学报:英文版》 CAS CSCD 2019年第5期311-314,共4页
This article briefly reviews and discusses the current status of major non-communicable diseases(m NCDs), definition of e-noise, its possible link as a risk factor for cardiovascular diseases and other m NCDs, and pro... This article briefly reviews and discusses the current status of major non-communicable diseases(m NCDs), definition of e-noise, its possible link as a risk factor for cardiovascular diseases and other m NCDs, and proposes possible mechanisms and hypotheses on that link, and how to control e-noise in the future. E-noise is defined as signal from electronic products and instruments that emit radiation and electromagnetic fields. It includes not only the acoustic but also non-acoustic noise. Just like road traffic and aircraft noises, e-noise may not only lead to hearing loss and health problems such as fatigue,stress, irritability, headache, and insomnia, but may also endanger cardiovascular health and result in hypertension, ischemic heart disease(myocardial infarction), arrhythmia(atrial fibrillation) and stroke;brain and metabolic problems such as obesity and diabetes;mental and cognitive impairment;as well as changing of humans’ long-evolved cortisol and circadian rhythms after long-term exposure. Even shortterm exposure to excessive e-noise may lead to heightened stress responses and low quality of life. In conclusion, e-noise is a potential danger in our world, and further studies are needed of its effects on mechanisms of aging, disease, and human health. 展开更多
关键词 ENVIRONMENT E-noise Healthrisk LIFESTYLE LONG-TERM EXPOSURE
Rapid Urban Land Expansion in Earthquake-Prone Areas of China
14
作者 Qingxu Huang Shiting Meng +2 位作者 Chunyang He Yinyin Dou Qiang Zhang 《国际灾害风险科学学报:英文版》 CSCD 2019年第1期43-56,共14页
A timely understanding of urban expansion in earthquake-prone areas is crucial for earthquake risk assessment and urban planning for earthquake mitigation.However, a comprehensive evaluation of urban expansion in eart... A timely understanding of urban expansion in earthquake-prone areas is crucial for earthquake risk assessment and urban planning for earthquake mitigation.However, a comprehensive evaluation of urban expansion in earthquake-prone areas is lacking in China, especially in the context of rapid urbanization. Based on time series urban land data and seismic ground-motion parameter zonation maps, this study analyzed urban expansion in the most seismically hazardous areas(MSHAs) of China from1992 to 2015 on the national, regional, and city scales. The results show that urban land area in the MSHAs expanded by 6767 km~2 from 1992 to 2015, with a gain of 350%.Specifically, the increase in urban land area of small cities in the MSHAs of western China during this period was the fastest, 6.24 times greater than that at the national level. In terms of spatial patterns, the urban land patches in the MSHAs in 2015 were more fragmented than those in 1992 on all scales. The percentage of change in the number of patches and the landscape shape index of the urban land patches of small cities in the MSHAs of western China were the highest across all cities. Therefore, we believe that special attention should be paid to the cities in the MSHAs that exhibit the most rapid increases in both urban land area and fragmentation, especially the small cities in western China. It is imperative to integrate earthquake mitigation into the urban planning of these cities. 展开更多
关键词 China MOST seismically hazardous areas SEISMIC HAZARD exposure URBANIZATION URBAN expansion URBAN SUSTAINABILITY
Socio-ecological vulnerability to climate change/variability in central rift valley,Ethiopia 预览
15
作者 Zenebe MEKONNEN Teshale WOLDEAMANUEL Habtemariam KASSA 《气候变化研究进展:英文版》 CSCD 2019年第1期9-20,共12页
Climate change/variability and environmental degradation have increased in the central rift valley of Ethiopia,which in turn making the people inhabiting in that ecosystem more vulnerable to the impacts.The purposes o... Climate change/variability and environmental degradation have increased in the central rift valley of Ethiopia,which in turn making the people inhabiting in that ecosystem more vulnerable to the impacts.The purposes of this study were to assess the vulnerability of households andagro-ecosystems to climate change and environmental degradation and the factors determining vulnerabilities in the central rift valley,Ethiopia.Data were collected between November 2014 and May 2015 by interviewing 355 respondents.This has been supplemented with focus group discussions and key informant interviews.The indicator and matrix methods were used to describe socio-ecological vulnerabilities.The resultsshowed that about 9%of the respondents were highly vulnerable to climate change/variability,and environmental degradation.Households in the lowland have the largest proportion of high vulnerable households(60%),while households in highland have the largest proportion of low vulnerable households(30%).In the lowland agro-ecology,the adaptive capacity component has contributed the largest share to household's vulnerability index to the impacts of climate change/variability and environmental degradation.The sensitivity component has higer contribution in highland agro-ecology and the exposure component in the midland agro-ecology.There were variations of income deviation between agro-ecologies that lead to variation in vulnerability of households.Household vulnerability index has shown a very light negative correlation with livelihood diversification index.The poorest households with little share of the total income distribution and with low livelihood diversity index,were the most vulnerable.The results showed that the highest exposure index on ecosystem functions and agricultural performance were in the lowland agro-ecology.This study highlighted the need to assess the social and ecological vulnerabilities in integrated approach as singling out one from the other is difficult.That is,social vulnerability impacts ecological vulnerabi 展开更多
关键词 Adaptive capacity VULNERABILITY EXPOSURE IMPACTS ECOSYSTEM services Sensitivity
在线阅读 下载PDF
Behavioral Abnormality along with NMDAR-related CREB Suppression in Rat Hippocampus after Shortwave Exposure 预览
16
作者 YU Chao BAI Yan Xin +10 位作者 XU Xin Ping GAO Ya Bing HAO Yan Hui WANG Hui TAN Sheng Zhi LI Wen Chao ZHANG Jing YAO Bin Wei DONG Ji ZHAO Li PENG Rui Yun 《生物医学与环境科学:英文版》 SCIE CAS CSCD 2019年第3期189-198,共10页
Objective To estimate the detrimental effects of shortwave exposure on rat hippocampal structure and function and explore the underlying mechanisms. Methods One hundred Wistar rats were randomly divided into four grou... Objective To estimate the detrimental effects of shortwave exposure on rat hippocampal structure and function and explore the underlying mechanisms. Methods One hundred Wistar rats were randomly divided into four groups (25 rats per group) and exposed to 27 MHz continuous shortwave at a power density of 5, 10, or 30 mW/cm2 for 6 min once only or underwent sham exposure for the control. The spatial learning and memory, electroencephalogram (EEG), hippocampal structure and Nissl bodies were analysed. Furthermore, the expressions of N-methyl-D-aspartate receptor (NMDAR) subunits (NR1, NR2A, and NR2B), cAMP responsive element-binding protein (CREB) and phosphorylated CREB (p-CREB) in hippocampal tissue were analysed on 1, 7, and 14 days after exposure. Results The rats in the 10 and 30 mW/cm2 groups had poor learning and memory, disrupted EEG oscillations, and injured hippocampal structures, including hippocampal neurons degeneration, mitochondria cavitation and blood capillaries swelling. The Nissl body content was also reduced in the exposure groups. Moreover, the hippocampal tissue in the 30 mW/cm2 group had increased expressions of NR2A and NR2B and decreased levels of CREB and p-CREB. Conclusion Shortwave exposure (27 MHz, with an average power density of 10 and 30 mW/cm2) impaired rats' spatial learning and memory and caused a series of dose-dependent pathophysiological changes. Moreover, NMDAR-related CREB pathway suppression might be involved in shortwave-induced structural and functional impairments in the rat hippocampus. 展开更多
关键词 Shortwave exposure Learning and memory HIPPOCAMPUS NMDAR CREB
在线阅读 下载PDF
Die in pieces:How Drosophila sheds light on neurite degeneration and clearance
17
作者 Maria L.Sapar Chun Han 《遗传学报:英文版》 SCIE CAS CSCD 2019年第4期187-199,共13页
Dendrites and axons are delicate neuronal membrane extensions that undergo degeneration after physical injuries. In neurodegenerative diseases, they often degenerate prior to neuronal death. Understanding the mechanis... Dendrites and axons are delicate neuronal membrane extensions that undergo degeneration after physical injuries. In neurodegenerative diseases, they often degenerate prior to neuronal death. Understanding the mechanisms of neurite degeneration has been an intense focus of neurobiology research in the last two decades. As a result, many discoveries have been made in the molecular pathways that lead to neurite degeneration and the cell-cell interactions responsible for the subsequent clearance of neuronal debris. Drosophila melanogaster has served as a prime in vivo model system for identifying and characterizing the key molecular players in neurite degeneration, thanks to its genetic tractability and easy access to its nervous system. The knowledge learned in the fly provided targets and fuel for studies in other model systems that have further enhanced our understanding of neurodegeneration. In this review, we will introduce the experimental systems developed in Drosophila to investigate injuryinduced neurite degeneration, and then discuss the biological pathways that drive degeneration. We will also cover what is known about the mechanisms of how phagocytes recognize and clear degenerating neurites, and how recent findings in this area enhance our understanding of neurodegenerative disease pathology. 展开更多
关键词 DROSOPHILA NEURITE DEGENERATION Axon Dendrite Wallerian DEGENERATION PHAGOCYTE PHAGOCYTOSIS PS exposure Injury assay
云南省先天性心脏病相关危险因素的病例对照研究 预览
18
作者 陈志松 李振 +1 位作者 曾永利 喻卓 《中国临床医学》 2019年第2期181-186,共6页
目的:分析云南省先天性心脏病(congenital heart diseases,CHD)发生的危险因素。方法:选择2017年1月至2018年1月在昆明医科大学第一附属医院经心脏彩超、心血管影像学检查确诊并住院治疗的1~10岁CHD患儿作为病例组。另选择同期在儿科住... 目的:分析云南省先天性心脏病(congenital heart diseases,CHD)发生的危险因素。方法:选择2017年1月至2018年1月在昆明医科大学第一附属医院经心脏彩超、心血管影像学检查确诊并住院治疗的1~10岁CHD患儿作为病例组。另选择同期在儿科住院部、门诊排除CHD和(或)其他先天性疾病的1~10岁儿童作为对照组。对照组母亲孕时年龄、孕期长短与病例组相近。与两组母亲进行面对面问卷访谈,调查家庭情况、居住环境、生活习惯、工作环境、妊娠史、疾病及服药史、负性生活事件及精神状态、饮食营养状况等内容,并进行单因素及多因素logistic回归分析。结果:单因素分析结果显示,母亲孕早期被动吸烟、孕早期接触农药、不良妊娠史、孕前患慢性病、孕早期感冒、孕早期发热、孕早期经历负性生活事件、孕早期服用解热镇痛药物、孕早期服用抗生素是CHD发生的危险因素(P<0.05)。多因素logistic回归分析表明,母亲孕早期被动吸烟(OR=2.26,95%CI 1.12~4.58)、不良妊娠史(OR=2.73,95%CI 1.31~5.69)、孕早期感冒(OR=4.33,95%CI 2.15~8.70)、孕早期经历负性生活事件(OR=2.14,95%CI 1.06~4.32)是CHD发生的主要危险因素;孕期常食用蛋肉鱼虾(OR=0.35,95%CI 0.15~0.79)、孕前及孕期补充叶酸、维生素及微量元素(OR=0.32,95%CI 0.16~0.64)是减少CHD发生的保护性因素(P<0.05)。结论:母亲孕前及孕期加强蛋白质、维生素、微量元素等合理搭配,同时减少烟雾暴露,减少感冒、负性生活事件及不良妊娠的发生,对预防和降低子代CHD的发生有重要意义。 展开更多
关键词 先天性心脏病 危险因素 暴露 病例对照研究
在线阅读 免费下载
Toxicity and mechanisms of action of titanium dioxide nanoparticles in living organisms
19
作者 Jing Hou Luyao Wang +4 位作者 Chunjie Wang Songlin Zhang Haiqiang Liu Shiguo Li Xiangke Wang 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第1期40-53,共14页
Titanium dioxide nanoparticles(TiO2 NPs) are one of the most widely used nanomaterials in the consumer products, agriculture, and energy sectors. Their large demand and widespread applications will inevitably cause da... Titanium dioxide nanoparticles(TiO2 NPs) are one of the most widely used nanomaterials in the consumer products, agriculture, and energy sectors. Their large demand and widespread applications will inevitably cause damage to organisms and ecosystems. A better understanding of TiO2 NP toxicity in living organisms may promote risk assessment and safe use practices of these nanomaterials. This review summarizes the toxic effects of TiO2 NPs on multiple taxa of microorganisms, algae, plants, invertebrates, and vertebrates. The mechanism of TiO2 NP toxicity to organisms can be outlined in three aspects: The Reactive Oxygen Species(ROS)produced by TiO2 NPs following the induction of electron–hole pairs; cell wall damage and lipid peroxidation of the cell membrane caused by NP-cell attachment by electrostatic force owing to the large surface area of TiO2 NPs; and TiO2 NP attachment to intracellular organelles and biological macromolecules following damage to the cell membranes. 展开更多
关键词 TiO2 nanoparticles PARTICLE size EXPOSURE OXIDATIVE stress LIVING ORGANISMS
一种低使用成本的高精度曝光和测量技术
20
作者 周畅 徐兵 朱岳彬 《光电子技术》 CAS 北大核心 2019年第3期210-214,共5页
提出了一种使用小尺寸MASK(光罩)的高精度曝光技术,能够实现1.5μm分辨率,几乎可以忽略的MASK成本。同时以曝光控制技术为基础,提出了一种快速进行TP/OL/CD精确测量的技术,为降低国产设备的测量使用成本提供了研究方向,同时提高了国产... 提出了一种使用小尺寸MASK(光罩)的高精度曝光技术,能够实现1.5μm分辨率,几乎可以忽略的MASK成本。同时以曝光控制技术为基础,提出了一种快速进行TP/OL/CD精确测量的技术,为降低国产设备的测量使用成本提供了研究方向,同时提高了国产屏的性价比,可大幅降低单点测量时间和测量成本。 展开更多
关键词 曝光 长寸 测量 光罩 精度 成本
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈