期刊文献+
共找到109,034篇文章
< 1 2 250 >
每页显示 20 50 100
急性呼吸窘迫综合征患者血清sTM水平变化及对预后的预测价值 认领
1
作者 陈雯雯 叶嗣颖 陈桂蓝 《中国医药导报》 CAS 2021年第2期16-19,共4页
目的研究急性呼吸窘迫综合征(ARDS)患者血清可溶性血栓调节蛋白(sTM)水平变化及对预后的预测价值。方法以2018年12月-2019年12月武汉市第三医院收治的96例ARDS患者作为观察组,根据氧合指数(OI)分为轻度组(25例)、中度组(53例)和重度组(1... 目的研究急性呼吸窘迫综合征(ARDS)患者血清可溶性血栓调节蛋白(sTM)水平变化及对预后的预测价值。方法以2018年12月-2019年12月武汉市第三医院收治的96例ARDS患者作为观察组,根据氧合指数(OI)分为轻度组(25例)、中度组(53例)和重度组(18例)。根据患者28 d后生存情况分为生存组(46例)和死亡组(50例),另择同期入院的48名健康体检者为对照组。比较观察组和对照组、不同程度组ARDS患者、不同结局组患者血清sTM水平和急性生理与慢性健康评分Ⅱ(APACHEⅡ)的差异,分析血清sTM水平和APACHEⅡ评分的相关性,绘制ROC生存曲线分析血清sTM水平和APACHEⅡ评分对ARDS患者预后的预测价值。结果观察组血清sTM水平和APACHEⅡ评分均高于对照组,差异有统计学意义(P<0.05)。不同程度组ARDS患者血清sTM水平和APACHEⅡ评分比较,差异有统计学意义(P<0.05),且重度组各指标水平高于中度组和轻度组,中度组各指标水平高于轻度组,差异有统计学意义(P<0.05)。血清sTM水平与APACHEⅡ评分呈正相关(r=0.691,P<0.05)。生存组血清sTM水平和APACHEⅡ评分均显著低于死亡组,差异有统计学意义(P<0.05)。ROC曲线结果显示,血清sTM水平对ARDS患者预后的预测效能高于APACHEⅡ评分(P<0.05)。结论sTM可能参与ARDS的病情发展过程,且其水平变化可作为判断ARDS患者病情程度和预后的早期生物标志物。 展开更多
关键词 急性呼吸窘迫综合征 可溶性血栓调节蛋白 预后 变化
在线阅读 下载PDF
原发性甲状腺功能减退患者服用左旋甲状腺素前后心肌酶谱的变化对比分析 认领
2
作者 廖碧芝 《中国社区医师》 2021年第3期52-53,共2页
目的:分析左旋甲状腺素应用于原发性甲状腺功能减退患者的疗效及对心肌酶谱水平的影响。方法:2018年1月-2019年6月收治原发性甲状腺功能减退患者50例,均采用左旋甲状腺素治疗。比较患者治疗前后血清心肌酶谱及甲状腺功能各项指标水平。... 目的:分析左旋甲状腺素应用于原发性甲状腺功能减退患者的疗效及对心肌酶谱水平的影响。方法:2018年1月-2019年6月收治原发性甲状腺功能减退患者50例,均采用左旋甲状腺素治疗。比较患者治疗前后血清心肌酶谱及甲状腺功能各项指标水平。结果:观察组治疗后FT3、FT4水平(2.92±1.03)、(0.93±1.03)低于对照组(0.78±0.30)、(0.26±0.11),TSH水平(5.21±1.23)显著低于对照组(7.89±0.34);观察组治疗后AST(19.12±2.23)、CK(50.62±8.45)、CK-MB(5.25±2.13)、LDH(113.2±25.34)水平均低于对照组(23.81±2.23)、(58.21±8.26)、(6.56±2.31)、(130.5±20.32),差异有统计学意义(P<0.05)。结论:左旋甲状腺素应用于原发性甲状腺功能减退患者,有助于显著改善心肌损伤及甲状腺功能。 展开更多
关键词 原发性甲状腺功能减退 左旋甲状腺素 心肌酶谱
在线阅读 下载PDF
Development of a large-scale remote sensing ecological index in arid areas and its application in the Aral Sea Basin 认领
3
作者 WANG Jie LIU Dongwei +2 位作者 MA Jiali CHENG Yingnan WANG Lixin 《干旱区科学:英文版》 SCIE 2021年第1期40-55,共16页
The Aral Sea Basin in Central Asia is an important geographical environment unit in the center of Eurasia.It is of great significance to the ecological protection and sustainable development of Central Asia to carry o... The Aral Sea Basin in Central Asia is an important geographical environment unit in the center of Eurasia.It is of great significance to the ecological protection and sustainable development of Central Asia to carry out dynamic monitoring and effective evaluation of the eco-environmental quality of the Aral Sea Basin.In this study,the arid remote sensing ecological index(ARSEI)for large-scale arid areas was developed,which coupled the information of the greenness index,the salinity index,the humidity index,the heat index,and the land degradation index of arid areas.The ARSEI was used to monitor and evaluate the eco-environmental quality of the Aral Sea Basin from 2000 to 2019.The results show that the greenness index,the humidity index and the land degradation index had a positive impact on the quality of the ecological environment in the Aral Sea Basin,while the salinity index and the heat index exerted a negative impact on the quality of the ecological environment.The eco-environmental quality of the Aral Sea Basin demonstrated a trend of initial improvement,followed by deterioration,and finally further improvement.The spatial variation of these changes was significant.From 2000 to 2019,grassland and wasteland(saline alkali land and sandy land)in the central and western parts of the basin had the worst ecological environment quality.The areas with poor ecological environment quality are mainly distributed in rivers,wetlands,and cultivated land around lakes.During the period from 2000 to 2019,except for the surrounding areas of the Aral Sea,the ecological environment quality in other areas of the Aral Sea Basin has been improved in general.The correlation coefficients between the change in the eco-environmental quality and the heat index and between the change in the eco-environmental quality and the humidity index were–0.593 and 0.524,respectively.Climate conditions and human activities have led to different combinations of heat and humidity changes in the eco-environmental quality of the Aral Sea Basin.Howev 展开更多
关键词 eco-environmental quality arid remote sensing ecological index Moderate Resolution Imaging Spectroradiometer(MODIS) landscape changes remote sensing monitoring Central Asia
在线阅读 免费下载
Long-term variations in runoff of the Syr Darya River Basin under climate change and human activities 认领
4
作者 Sanim BISSENBAYEVA Jilili ABUDUWAILI +1 位作者 Assel SAPAROVA Toqeer AHMED 《干旱区科学:英文版》 SCIE 2021年第1期56-70,共15页
In this study,we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human a... In this study,we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff.The Syr Darya River,which is supplied by snow and glacier meltwater upstream,is an important freshwater source for Central Asia,as nearly half of the population is concentrated in this area.River runoff in this arid region is sensitive to climate change and human activities.Therefore,estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management.The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods,including the Pettitt change point test and Mann-Kendall trend tests.It was found that 8 out of 11 hydrological stations showed significant downward trends in river runof f.Change of river runoff variations occurred in the year around 1960.Moreover,during the study period(1930–2015),annual mean temperature,annual precipitation,and annual potential evapotranspiration in the river basin increased substantially.We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration.It was estimated that human activities accounted for over 82.6%–98.7%of the reduction in river runoff,mainly owing to water withdrawal for irrigation purpose.The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective. 展开更多
关键词 river runoff variations water resources management land use/land cover changes Mann-Kendall trend test hydrological sensitivity analysis Aral Sea Central Asia
在线阅读 免费下载
我国农村职业教育政策的变迁与启示——基于1949—2019年政策文本的分析 认领
5
作者 曲铁华 姚旖璇 《沈阳师范大学学报:社会科学版》 2021年第1期100-107,共8页
农村职业教育作为职业教育不可分割的重要组成部分,对于解决“三农”问题、消解城乡长期性二元结构等问题具有重要作用。从总的情况看,我国农村职业教育政策发展分为三个阶段:从以农业为重心的探索阶段(1949—1977年),到以农村为中心的... 农村职业教育作为职业教育不可分割的重要组成部分,对于解决“三农”问题、消解城乡长期性二元结构等问题具有重要作用。从总的情况看,我国农村职业教育政策发展分为三个阶段:从以农业为重心的探索阶段(1949—1977年),到以农村为中心的调整阶段(1978—2000年),再到以农民为核心的转型阶段(2001年至今)。其经验是:依靠农村职业教育政策确立农村职业教育地位;农村职业教育政策具有一定协调功能;依靠农村职业教育政策推动农村职业教育改革。其启示为:农村职业教育政策的制定要以农村职业教育自身发展规律为根本依据;以立法力度的加强为根本保障;以切合新时期发展需求为根本原则。 展开更多
关键词 农村职业教育 教育政策 变迁 文本分析
在线阅读 免费下载
急性白血病患者凝血与纤溶指标的变化研究 认领
6
作者 谭斌 李喜喜 董艳 《国际医药卫生导报》 2021年第1期101-103,共3页
目的探讨急性白血病患者凝血与纤溶指标的变化。方法选取2018年1月至2018年12月本院收治的急性白血病患者76例作为研究组,同时选取本院同期进行体检的健康人群76例作为对照组。比较两组人群一般资料、凝血与纤溶指标变化情况、急性髓细... 目的探讨急性白血病患者凝血与纤溶指标的变化。方法选取2018年1月至2018年12月本院收治的急性白血病患者76例作为研究组,同时选取本院同期进行体检的健康人群76例作为对照组。比较两组人群一般资料、凝血与纤溶指标变化情况、急性髓细胞白血病组、急性淋巴细胞白血病组、急性混合型白血病组凝血与纤溶指标变化情况。结果研究组D-D、FIB、APTT、PT指标分别为(6907.3±1628.5)ng/ml、(3.9±0.2)g/L、(36.4±2.7)s、(15.4±3.5)s,均高于对照组(136.2±45.1)ng/ml、(3.1±0.4)g/L、(33.4±2.3)s、(10.4±3.1)s,差异均有统计学意义(均P<0.05);急性淋巴细胞白血病组APTT、PT分别为(47.7±15.5)s、(19.4±5.8)s,均高于急性髓细胞白血病组(31.6±5.1)s、(13.5±2.9)s,急性混合型白血病组(31.8±7.3)s、(14.7±3.8)s,差异均有统计学意义(均P<0.05);急性髓细胞白血病组、急性混合型白血病组APTT、PT比较,差异均无统计学意义(均P>0.05);急性髓细胞白血病组D-D为(8245.2±1725.2)ng/ml,高于急性淋巴细胞白血病组(5861.7±1707.5)ng/ml,急性混合型白血病组(2058.3±364.3)ng/ml,差异有统计学意义(P<0.05);三组FIB相比,差异无统计学意义(P>0.05)。结论急性白血病患者处于纤溶亢进状态时存在出血倾向,对患者D-D、FIB、PT进行检测有利于判断患者是否存在出血倾向,还能对患者的预后进行判断。 展开更多
关键词 急性白血病 凝血 纤溶指标 变化 研究
在线阅读 下载PDF
新冠战“疫”中高职大学生思想状况的积极变化及原因探究——以某高职院校为例 认领
7
作者 秦娟华 陈蕊花 《北京工业职业技术学院学报》 2021年第1期70-73,共4页
为了准确把握高职大学生在抗击新冠肺炎疫情斗争中的思想变化,探索进一步做好高职院校思想政治工作的新途径和新方法,增强思想政治工作的针对性、实效性和吸引力、感染力,采取微信访谈等方式,对某高职院校学生进行深入调研,探索总结抗... 为了准确把握高职大学生在抗击新冠肺炎疫情斗争中的思想变化,探索进一步做好高职院校思想政治工作的新途径和新方法,增强思想政治工作的针对性、实效性和吸引力、感染力,采取微信访谈等方式,对某高职院校学生进行深入调研,探索总结抗击新冠肺炎疫情期间思想政治工作的成功实践经验,对进一步加强和改进高职院校思想政治工作提供参考借鉴。 展开更多
关键词 高职大学生 思想状况 新冠肺炎 变化 原因
在线阅读 下载PDF
文章速递国际食品法典农药残留限量标准的变迁及启示 认领
8
作者 郭伟锋 江东坡 《中国农业科技导报》 CAS CSCD 北大核心 2021年第2期115-122,共8页
在整理2008—2018年国际食品法典颁布的农药最大残留限量(maximum residue limits,MRLs)标准文件资料基础上,建立了完整的国际食品法典农药残留值数据库,并根据不同的产品种类,从法典MRLs标准的总体概况、条目数和农药种类3个方面分析... 在整理2008—2018年国际食品法典颁布的农药最大残留限量(maximum residue limits,MRLs)标准文件资料基础上,建立了完整的国际食品法典农药残留值数据库,并根据不同的产品种类,从法典MRLs标准的总体概况、条目数和农药种类3个方面分析了法典MRLs标准的变迁。结果显示,虽然法典MRLs标准在条目数和农药类别上呈逐年增加趋势,且主要变化集中在蔬菜、水果和哺乳动物产品三类产品上,但是法典MRLs标准的整体残留均值却在逐年上升。表明国际食品法典委员会(Codex Alimentarius Commission,CAC)虽然针对更多的产品和农药类别制定了更广泛的法典MRLs标准,且不同的产品及农药种类变动不同,但是法典MRLs标准在整体残留均值上有放宽趋势,即CAC正在放宽法典MRLs标准。我国要抓住CAC放宽法典MRLs标准的机会,加快对国内农药MRLs标准的制定和修订,减少因各国农药MRLs标准调整形成的技术贸易壁垒对我国农产品出口贸易带来的损失。这对完善我国食品标准体系,提高我国食品质量安全水平、扩大我国农产品出口和维护我国在国际农产品贸易中的合法权益具有十分重要的意义。 展开更多
关键词 国际食品法典委员会(CAC) 最大残留限量(MRLs)标准 变迁 启示
在线阅读 下载PDF
文章速递基于TB/T 2841—2019的铁路客车空气弹簧产品认证研究 认领
9
作者 李雪春 《铁道技术监督》 2021年第2期17-22,共6页
产品标准是影响产品认证的重要因素,是编制产品认证规则的基础。对比TB/T 2841—2019《铁路车辆空气弹簧》与TB/T 2841—2010/XG1—2011《铁道车辆空气弹簧》的主要技术变化,分析这些技术变化对铁路客车空气弹簧产品认证方案、认证规则... 产品标准是影响产品认证的重要因素,是编制产品认证规则的基础。对比TB/T 2841—2019《铁路车辆空气弹簧》与TB/T 2841—2010/XG1—2011《铁道车辆空气弹簧》的主要技术变化,分析这些技术变化对铁路客车空气弹簧产品认证方案、认证规则、检测方法与结果的影响,给出新版铁路客车空气弹簧认证规则调整方案。 展开更多
关键词 铁路客车 空气弹簧 行业标准 变更 认证方案 认证规则
在线阅读 下载PDF
文章速递The Challenges of Treating Acute Myocardial Infarction due to Variant Angina:Lesson from an Interesting Case 认领
10
作者 Wen-Yuan Ding Jia-Min Li +3 位作者 Fei Zheng Li-Li Wang Xin-Yi Wei Guo-Hua Li 《Cardiovascular Innovations and Applications》 2021年第1期213-218,共6页
Coronary artery spasm can cause recurrent variant angina with ST-segment elevation.The patient was asymptomatic with normal vitals and ECG was normal.We present a case associated with transient ST-segment elevation an... Coronary artery spasm can cause recurrent variant angina with ST-segment elevation.The patient was asymptomatic with normal vitals and ECG was normal.We present a case associated with transient ST-segment elevation and signifi-cant increase in troponin levels with non-critical lesion with normal CAG. 展开更多
关键词 Variant angina coronary spasm transient ST segment changes coronary angiography troponin levels calcium channel blockers
在线阅读 下载PDF
CT Scan of the Foot in Patients with Chronic Non-Healing Diabetic Foot Ulcer 认领
11
作者 M. Rubina Fathimaa Arcot Rekha 《临床医学病理报告(英文)》 2020年第11期335-342,共8页
<strong>Background:</strong> Diabetes mellitus is a chronic disease where there is an increased blood sugar level in the body which is either caused due to inability of the pancreas to secrete insulin or t... <strong>Background:</strong> Diabetes mellitus is a chronic disease where there is an increased blood sugar level in the body which is either caused due to inability of the pancreas to secrete insulin or the body’s inability to utilize it. The prevalence of diabetes mellitus is growing rapidly worldwide. Statistics show that in the year 2014, there were a total of 422 million cases of DM. Diabetes mellitus is a major cause of heart attacks, kidney failure, blindness and leg amputations. Diabetic foot ulcers are quite common and are estimated to affect nearly 15% of all diabetic patients during their lifetime. In long standing diabetic patients with chronic non-healing ulcers, bony changes or deformities are not uncommon. These bony changes can be identified using CT scans. <strong>Materials and Methods:</strong> An observational study was conducted on a total of 40 patients with chronic non-healing ulcer attending the surgery outpatient department of Saveetha Medical College, Chennai, Tamilnadu. The CT-scans of their foot were observed for deformities or bony changes. <strong>Results:</strong> Out of 40 patients, 67.5% were males and 32.5% were females. A maximum number of subjects fell under the age group of 51 - 60 years. The most common site of the ulcer was found to be in the plantar surface of big toe (53%). Among the 40 patients, 33 of them were found to have bony abnormalities on the CT scan of foot and no apparent changes were seen in the rest. Bone erosions (35%), osteopenic changes (22.5%), Charcot’s joint (2.5%), osteophyte formation (12.5) and reduced joint space (10%) were the predominant changes observed on the CT scans of the study population. 展开更多
关键词 Diabetic Foot Ulcer Bony Abnormalities CT Scan Bone Erosions Charcot’s Joint Osteophyte Formation Reduced Joint Space Osteopenic Changes Plantar Surface of Big Toe
在线阅读 免费下载
How to Heat a Planet? Impact of Anthropogenic Landscapes on Earth’s Albedo and Temperature 认领
12
作者 Mark Healey 《地球科学国际期刊(英文)》 2020年第6期420-457,共38页
Today anthropogenic climate change is underway and predicted future global temperatures vary significantly. However, the drivers of current climate change and their links to Earth’s natural glacial cycle have yet to ... Today anthropogenic climate change is underway and predicted future global temperatures vary significantly. However, the drivers of current climate change and their links to Earth’s natural glacial cycle have yet to be fully resolved. Currently, many on a local level understand, and are exposed to, the heat energy generated by what’s referred to as the urban heat island effect (UHI), whereby natural flora with higher albedos </span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> replaced by manmade urban areas with lower albedos. This heat effect is not constrained to these regions and all anthropogenic surfaces with lower albedos need to be studied and quantified as the accumulated additional heat energy (infrared energy) is trapped within Earth’s atmosphere and could affect the Earth on a planetary level. Deployed satellites have detected critical changes to Earth’s albedo to lower levels, however the cause and impact of these changes have yet to be fully understood and incorporated into Global Circulation models (GCMs). Here it’s shown that industrialization of anthropogenic landscape practices of the past century has displaced millions of square kilometres of naturally high albedo grasslands with lower albedo agricultural landscapes. Utilising a fundamental Energy Balance Model, (EBM) it’s demonstrated these specific changes have generated vast amounts of additional heat energy which is trapped by the atmosphere, transferred and stored within the oceans of the Earth as shown in <b></span></span></span><a href="file:///E:/360data/%E9%87%8D%E8%A6%81%E6%95%B0%E6%8D%AE/%E6%A1%8C%E9%9D%A2/%E7%A9%BA%E7%99%BD%E9%A1%B5.docx#F1"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><b><span style="font-family:Verdana;">Figure 1</span></b></span></span></a><span style="font-family:Verdana;"><span style 展开更多
关键词 Earth Albedo Anthropogenic Landscape Changes Heat Fluxes Earth’s Energy Budget Glacial Cycle Gaia Links
在线阅读 免费下载
Using MAN and Coastal AERONET Measurements to Assess the Suitability of MODIS C6.1 Aerosol Optical Depth for Monitoring Changes from Increased Arctic Shipping 认领
13
作者 Nicole Mölders Mariel Friberg 《大气污染开放期刊(英文)》 2020年第4期77-104,共28页
Collocated data of the moderate resolution imaging spectroradiometer (MO<span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS) Collection 6.1 aerosol o... Collocated data of the moderate resolution imaging spectroradiometer (MO<span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS) Collection 6.1 aerosol optical depths (AOD) at 3 km × 3 km north of 59.9</span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">N over ocean were assessed at 550 nm by aerosol robotic network (AERONET) data from coastal sites and marine aerosol network (MAN) data from vessels during June to October 2006 to 2018. Typically, MODIS AOD w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> higher at low and lower at high values than the AERONET AOD. Discrepancies were largest for sites where the Earth’s surface around the site is very heterogeneous (Canadian Archipelago, coast of Greenland). Due to the higher likelihood for sea-ice, MAN and MODIS AOD differed stronger west of Greenland and over the Beaufort Sea than at location in the Greenland and Norwegian Seas and Atlantic. MODIS AOD well captured the inter-seasonal variability found in the AERONET AOD data (R = 0.933). At all sites, MO</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS and AERONET AOD agreement improved as time progressed in the shipping season, hinting at errors in sea-ice vs. open water classification. Overall 75.3% of the MODIS AOD data fell within the limits of the error envelops of the AERONET/MAN AOD data with MAN ranging between 87.5% and 100%. Changes in both MODIS and AERONET mean AOD between two periods of same length (2006-2011, 2013-2018) were explainable by changes in emissions for all sites</span><span style="font-family:Verdana;">.</span> 展开更多
关键词 Aerosol Optical Depth over the Arctic Ocean MODIS Evaluation by AERONET and MAN Data Changes in Arctic Aerosol Optical Depth over the Ocean North of 59.9°N Arctic Shipping Season Aerosol Optical Depths
在线阅读 免费下载
Isotopic and Petrographic Evidence as a Proxy in Paleoclimatic Reconstructions from Flowstones in Southern Spain 认领
14
作者 Concepción Jiménez de Cisneros Antonio González-Ramón +2 位作者 Cristina Sequero Bartolomé Andreo Ian J. Fairchild 《地质学期刊(英文)》 2020年第6期597-611,共15页
Changes in the morphology and mineralogy of speleothems (flowstones) clearly respond to climate-related phenomena, such as drip rate variability and temperature-modulated cave ventilation. Detailed petrographic observ... Changes in the morphology and mineralogy of speleothems (flowstones) clearly respond to climate-related phenomena, such as drip rate variability and temperature-modulated cave ventilation. Detailed petrographic observations have been coupled with <em><em style="font-family:Verdana;white-space:normal;"><em style="font-family:Verdana;white-space:normal;">δ</em></em></em><sup style="font-family:Verdana;white-space:normal;">18</sup><span style="font-family:Verdana;white-space:normal;">O</span><sup></sup> and <span style="font-size:12px;font-family:Verdana;"><em>δ</em></span><span style="font-size:12px;font-family:Verdana;"><sup>13</sup>C values. Fabrics may show changes related to variations in supersaturation, drip rate or input of detrital particles or organic compounds. Fabrics formed under relatively constant and regular drips (columnar compact, open and elongated) show similar <em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C values, which are more negative than those of micrite and microsparite. The combination of internal microstratigraphy studies and isotopic data (<em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C) from two flowstones collected from two caves in the north of Almeria province (SE Spain), suggest a spectrum of environmental conditions ranging from wetter to drier periods. Both records constitute a very useful tool for screening and interpreting high-resolution paleoclimate reconstructions.</span> 展开更多
关键词 SPELEOTHEMS Flowstones Fabrics Isotopic Characterization CAVE Paleoclimatic Changes
在线阅读 免费下载
Genotoxic and Histopathological Effects of Water Pollution on <i>Clarias gariepinus</i>Fish at Fayoum Governorate, Egypt 认领
15
作者 Khalid H. Zaghloul Heba A. Mohamed +1 位作者 Abdulkareem M. Abdullatef Mohamed W. Khalil 《自然资源(英文)》 2020年第11期499-519,共21页
<span style="font-family:;" "=""><span style="font-family:Verdana;">Increasing land reclamation in El-Fayoum governorate has led to increase the amount of drainage water ... <span style="font-family:;" "=""><span style="font-family:Verdana;">Increasing land reclamation in El-Fayoum governorate has led to increase the amount of drainage water that discharged without prior treatments to two main drains, El-Wadi and El-Bats drainages loaded by salts and heavy metals. So, the present investigation aims to evaluate quality of water samples collected from a branch of the river Nile (El-Lahon canal) and the main drains (El-Bats and El-Wadi) at Fayoum governorate on some biomarkers of the Nile catfish;</span><i><span style="font-family:Verdana;">Clarias gariepinus</span></i><span style="font-family:Verdana;"> inhabiting the studied degradable aquatic habitats. Water and nighty fish samples colleted from the different studied sites of collection by the help of fishermen for physicochemical analyes of water and fish biochemical analyses and histopathological alteration. Results revealed highly significant differences at P ≤ 0.01 with the highest water ammonia, nitrite, heavy metals (Cu, Zn, Pb and Cd) and lowest dissolved oxygen content accompanied by metals bioaccumulation in vital organs of fish collected from the main drains (El-Bats and El-Wadi) in comparision with that collected from the studied branch of the river Nile. Higher bioaccumulation of the studied heavy metals in gills, liver, kidney and muscles of </span><i><span style="font-family:Verdana;">Clarias gariepinus </span></i><span style="font-family:Verdana;">collected from the main drains significant increase in serum glucose, liver and kidney functions, disturbance in protein profile of fish collected from the studied main drains than that of fish collected from the river Nile branch, El-Lahon that showed more or less normal values. Moreover, histopathological alterations in gills, liver, kidneys and clear DNA strand breaks in fish liver cells increased statistically in </span><i><span style="font-family:Verdana;">Clarias gariepinus </span></i><span style="font-family:Verdana;">collected from El-</span></span><span style="font 展开更多
关键词 Drainage Water CATFISH GENOTOXICITY Histopathology Biochemical Changes
在线阅读 免费下载
Impact of Land-Use Changes on Sediment Load and Capacity Reduction of Lake Ziway, Ethiopia 认领
16
作者 Tagese Kalsido Belete Berhanu 《自然资源(英文)》 2020年第11期530-542,共13页
<span style="font-family:Verdana;">Land-use change has been</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">... <span style="font-family:Verdana;">Land-use change has been</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">a factor that alters the hydrologic response of the watersheds leading to influencing on sediment yield changes. This study is mainly focusing on the assessment of the impacts of the land-use changes on sediment load and lake depth reduction on Lake Ziway, Ethiopia using an integrated approach of Remote Sensing (RS), GIS and SWAT model. ERDAS IMAGINE 14 model was used to generate land-use maps from Landsat TM, ETM+, and Ls8 acquired, in 1988, 2002 and 2015 as representative for the periods of (1988</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">1998), (1998</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2008) and (2008</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">2018), respectively. The maximum likelihood algorithm of supervised classification applied to classify the </span><span style="font-family:Verdana;">basin land-use into seven land-use classes. The SWAT hydrological model</span><span style="font-family:Verdana;"> with ArcGIS interface setup for the basin to evaluate the flow and sediment load with calibration and validation performance of the model range R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (0.71 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 0.89) and NSE (0.57 </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 0.87). As a result, the total average annual sediment yield from the sub-basins estimated as 3.59</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr, 4.36</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr, and 4.89</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ 展开更多
关键词 Land-Use Changes Watersheds Sediment Yield Lake Depth Lake Ziway Ethiopia
在线阅读 免费下载
Transient Stability Analysis of 33 KV Transmission Network of Egi Community, Nigeria 认领
17
作者 Promise Elechi Christopher Okwuchukwu Ahiakwo Ugochukwu Nureedin Okwu 《电力能源(英文)》 2020年第3期18-35,共18页
Transient analysis of 33 KV power transmission line stability of Egi communi-ty is considered in this research work with the aim of reducing the frequency of fault occurrence and voltage collapse in the network. The s... Transient analysis of 33 KV power transmission line stability of Egi communi-ty is considered in this research work with the aim of reducing the frequency of fault occurrence and voltage collapse in the network. The supply is taken from Egi generating station located at Total Nigeria Limited Gas Plant Obite at voltage level of 33 KV to Egi communities. This work focuses on the transient nature of network stability since transient fault is the most dangerous in elec-trical systems. The swinging of the generator rotor in the event of transient three-phase short circuit fault can be monitored by the circuit breakers and the protective relays which causes mal-functioning of the circuit breakers and pro-tective relays leading to abnormal behavior of the network. Therefore, data obtained from the power station were used as a case study of Independent Power Producer (IPP) in Nigeria. For investigation of the power angle, angular velocity, rotor angle differential changes, and angular velocity differential changes, an electrical transient analyzer tool was employed (ETap version 16.00) for circuit breaker and protective relay time setting of (0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60). The work used the Trapezoidal numerical technique for data analysis. The graphs were plotted using Matlab R2015a and the results obtained showed that when a symmetrical three-phase short circuit fault occur at one or any of the feeders, the fault must be cleared as quick as possible through the coordination of the circuit breakers and protective relays. For this research work, 17 cycles corresponding to relay time setting of t = 0.34 s were recommended and at each cycle, changes in time with respect to changes in rotor angle, angular velocity, rotor differential and angular velocity differential were calculated on the power network simultaneously. The results demonstrated that the Trapezoidal method is numerically stable, accurate and has faster respond time when compared to Modified Euler and swing equat 展开更多
关键词 ROTOR Angle Transient Stability SWING Equation ANGULAR Speed Differential Changes Trapezoidal RULE Fault CLEARING TIME Critical CLEARING TIME
在线阅读 免费下载
Principle for the Working of the Lithium-Ion Battery 认领
18
作者 Kai Wai Wong Wan Ki Chow 《现代物理(英文)》 2020年第11期1743-1750,共8页
The technological advances in Lithium-ion batteries have created many new applications, including electric vehicles. In this short note, we shall explain in simple terms the basic physics why and how it is possible to... The technological advances in Lithium-ion batteries have created many new applications, including electric vehicles. In this short note, we shall explain in simple terms the basic physics why and how it is possible to have high energy capacity in Lithium-ion batteries. However, heating has been a common problem and without appropriate design, they might give fire and explosion as reported. 展开更多
关键词 Effective Coulomb Potential for Atomic Orbitals Bohr Atomic Orbital Energies Changes Due to Space Dimensions Symmetries Change in Lithium Metal Ionized Valence Bands Binding
在线阅读 免费下载
Severe Hypokalemia ECG Changes Mimicking Those of Acute Coronary Syndrome (ACS) in Patient with Underlying Ischaemic Heart Disease: A Case Review 认领
19
作者 C. Sethuraman S. F. Mohd +3 位作者 S. Govindaraju W. J. Tiau N. D. Mohamad Farouk H. H. Che Hassan 《急诊医学(英文)》 2020年第2期53-58,共6页
<strong>Background:</strong> Hypokalemia is seen on regular basis in medical emergency. The definition of hypokalemia is serum potassium level below 3.5 mmol/L, meanwhile severe hypokalemia is serum potass... <strong>Background:</strong> Hypokalemia is seen on regular basis in medical emergency. The definition of hypokalemia is serum potassium level below 3.5 mmol/L, meanwhile severe hypokalemia is serum potassium level below 2.5 mmol/L [1]. Patient with hypokalemia can present with wide range of presentation including musculoskeletal complaints from numbness to acute paralysis. Severe hypokalemia has tendency to progress to intestinal paralysis and respiratory failure. In some cases of hypokalemia, cardiovascular system can also be affected causing cardiac arrhythmias and heart failure [2]. <strong>Aim:</strong> This case report is to highlight that severe hypokalaemia can present with ECG changes mimicking acute coronary syndrome (ACS) which was fully resolved with correction of potassium level. <strong>Methods:</strong> We report a case of 84 years old Chinese man with underlying triple vessel disease presented with generalised body weakness for 2 days. ECG on arrival noted changes suggestive of ACS with ST segment depression in lead V4-V6 with first degree heart block, however patient had no ischemic symptoms and the potassium level was severe low at 1.6 mmol/L (3.5 - 5.1 mmol/L). He was correctly not treated for ACS. <strong>Outcomes:</strong> Repeated ECG post fast intravenous potassium correction noted complete resolution of the ST segment depression and first degree heart block. Patient discharged well from hospital four days later with potassium level of 3.8 mmol/L. <strong>Conclusions:</strong> Severe hypokalemia with asymptomatic ECG of ACS changes can safely be treated as a single entity clinical emergency with good resolution and no complication after normalizing potassium level. 展开更多
关键词 HYPOKALEMIA ECG Changes Acute Coronary Syndrome (ACS) Ischaemic Heart Disease
在线阅读 免费下载
过去百年松嫩平原农田扩张的干旱效应 认领 被引量:1
20
作者 于万辉 张丽娟 +3 位作者 张宏文 姜蓝齐 张安康 潘涛 《地理学报:英文版》 SCIE CSCD 2020年第3期439-454,共16页
The effects of human activities on climate change are a significant area of research in the field of global environmental change.Land use and land cover change(LUCC)has a greater effect on climate than greenhouse gase... The effects of human activities on climate change are a significant area of research in the field of global environmental change.Land use and land cover change(LUCC)has a greater effect on climate than greenhouse gases,and the effect of farmland expansion on regional drought is particularly important.From the 1910s to the 2010s,cultivated land in Songnen Plain increased by 2.67 times,the area of cultivated land increased from 4.92×10^4 km^2 to 13.14×10^4 km^2,and its percentage of all land increased from 25%to 70%.This provides an opportunity to study the effects of the conversion of natural grassland to farmland on climate.In this study,the drought indices in Songnen Plain were evaluated from the 1910s to the 2010s,and the effect of farmland expansion on drought was investigated using statistical methods and the Weather Research and Forecasting Model based on UK’s Climatic Research Unit data.The resulting dryness index,Palmer drought severity index,and standardized precipitation index values indicated a significant drying trend in the study area from 1981 to 2010.This trend can be attributed to increases in maximum temperature and diurnal temperature range,which increased the degree of drought.Based on statistical analysis and simulation,the maximum temperature,diurnal temperature range,and sensible heat flux increased during the growing season in Songnen Plain over the past 100 years,while the minimum temperature and latent heat flux decreased.The findings indicate that farmland expansion caused a drying trend in Songnen Plain during the study period. 展开更多
关键词 drought effect farmland expansion centennial-scale changes Songnen Plain
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈