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1.
淮河流域近50年来气候变化及突变分析   总被引:1,自引:0,他引:1  
基于淮河流域1961~2015年的主要气象数据,采用趋势分析、M-K检验和R/S方法,对淮河流域的气温、降水和日照时数3个要素的时间序列进行趋势分析和突变点检验,结果显示:1淮河流域多年平均气温在时间上呈现明显突变上升趋势,其中大部分站点气温突变出现在20世纪90年代;流域南部的气温上升程度高于北部地区;从整个流域的Hurst指数分析来看,未来淮河流域的年平均气温仍将持续升高,但上升程度不显著。2淮河流域的年降水量在时间上呈现一定的减少趋势,并且发生多次降水突变现象;各站点的降水量变化不大,但均出现多次突变情况;从Hurst指数来看,流域未来的年平均降水量有上升趋势。3流域的年平均日照时数呈现下降趋势,但变化并不显著;各站点均出现明显的日照时数下降现象;从Hurst指数来看,流域未来的日照时数将继续下降。  相似文献   

2.
横穿Lambert冰川流域和沿该流域东侧中山站-DomeA断面考察现场观测结果显示,该流域东、西两侧降水量的空间分布明显不同,东侧符合从海岸内向陆不断减小的普遍规律,西侧最大降水量在距海岸300-500km区域,东侧平均积累速率较西侧高。冰芯研究提出,过去50年来温度和降水变化呈现相反趋势:东侧温度和降水都为升高;西侧降水明显降低,温度虽有降低迹象,但变化不明显。海岸带考察站温度记录以及南极地区水汽传输模拟研究也得出谷地两侧的温度和降水有很大差异。在100-200年时间尺度上,其差异虽有所减弱,但Lambert冰川流域仍然比较独特。因此,可以认为Lambert冰种谷地是东南极洲重要的气候分界线。  相似文献   

3.
本文以辽宁省彰武风沙区雨养耕地为研究对象开展了针对衣作物增产的培肥地力研究。试验结果表明:风沙区雨养耕地土壤养分本底含量较低,有机质、速效氮、速效磷、速效钾平均含量分别为10.4g/kg、54.8mg/kg、7.3mg/kg、92.0mg/kg。增施氮、磷肥对作物产量无明显的增产效果,但增施钾肥增产效果明显。说明在目前的施肥水平下,氮、磷养分已不是作物产量增加的主要限制因子,而土壤中有效钾含量的下降已经上升为主要限制因子。沙区农业生产应加大有机肥的投入,调整氮、磷、钾肥的施用比例。  相似文献   

4.
摘要:目的提取弓形虫体外细胞共培养上清,并研究上清对人急性单核细胞白血病细胞THP-1增殖及凋亡的影响。方法收集对数生长期的THP-1细胞以5X10^7/ml细胞浓度接种于不同培养瓶中,对照组加入含10%胎牛血清的RPMll640,实验组加入相同体积不同数量(2×10^7/ml、4X10^7/ml、8×10^7/m1)弓形虫速殖子培养上清,采用四甲基氮噻唑蓝(MTY)法检测吸光度(A490值)并计算THP-1细胞增殖抑制率;倒置显微镜下观察细胞形态变化;Annexin-V-FITC/PI染色细胞后上流式细胞仪检测各个时间点细胞凋亡率变化,以Western印迹方法分析凋亡相关蛋白Bax、Bcl-2的表达或活性。结果MTY法检测结果弓形虫培养上清呈时间剂量依赖性抑制THP-1细胞株增殖,倒置显微镜下观察处理组细胞有发泡现象和凋亡小体出现。流式细胞仪检测弓形虫感染后的THP-1细胞凋亡率较对照组有升高趋势(P〈0.05),呈量效依赖性,Westernblot检测刚地弓形虫培养上清作用于THP-l细胞48h后实验组的Bax、Bcl-2蛋白表达较对照组的比值分别有明显的升高与降低(P〈0.05)。结论刚地弓形虫速殖子培养上清对体外培养THP-l细胞增殖有明显的抑制作用,并可诱导THP-1细胞凋亡。  相似文献   

5.
目的调查分析我院20ff6~2010年临床分离的革兰阴性菌对碳青霉烯类抗生素的耐药性。方法采用纸片扩散法进行抗菌药物敏感实验,采用WHONET5.4软件及SPSS13.0软件进行数据分析。结果大肠埃希菌和肺炎克雷伯菌对亚胺培南和美罗培南的耐药率呈上升趋势,但最高不超过4.5%。铜绿假单胞菌对亚胺培南的耐药率2006年和2007年监测显示为21.3%和41%。2008年达到44.8%,在2009年下降为12.4%,但2010年爽迅速增加到30.1%。鲍曼不动杆菌对亚胺培南耐药率的逐年上升更为显著,从2006年9.1%上升到2010年的68%,差异具有统计学意义(P〈0.01)。嗜麦芽窄食单胞菌对碳青霉烯类抗生素天然耐药,2006年对亚胺培南耐药率为30%,但自2007年起就增加到80.8%,最高达100%。结论肠杆菌科细菌对碳青霉烯类敏感性高,近年耐药率有上升趋势。铜绿假单胞菌和鲍曼不动杆菌对碳青霉烯类耐药率高,尤其是鲍曼不动杆菌的分离率逐年增加,耐药形势严峻。临床应合理使用抗生素,减少多重耐药株的产生。  相似文献   

6.
采用活性粉末混凝土和聚苯乙烯材料研制了具有与天然砂岩相似孔隙分布特征和物理力学性质的孔隙体模型,通过不同孔隙率模型的SHPB冲击实验和CT扫描实验观察和分析了孔隙体中应力波的传播特性以及传播过程中内部孔隙和固体介质的变化.研究表明:1)孔隙率显著影响应力波的传播特征.相同应变率时,孔隙率越大,反射波幅越大、波峰越多、透射波幅越小;孔隙率降至5%时反射波接近于单峰;应变率越高上述现象越明显;2)孔隙体的能量耗散率WJ/W1随孔隙率增加而线性增加,WJ/W1对应变率较敏感;3)应力波传播性质和能量耗散行为的差异与孔隙的演化机制有关.孔隙率低于10%时内部机制表现为固体介质破裂或形成新孔隙,应力波能量主要被消耗形成新开裂面或新孔隙,原有孔隙变形不大.此过程中应变率对改变孔隙形状的作用不明显;孔隙率高于15%时孔隙演化机制与应变率有关,低应变率时仍以固体介质开裂或形成新孔隙为主,但新增开裂面或新孔隙的数量相对较少;高应变率时内部结构变化同时存在固体介质开裂和孔隙变形两种机制,其中孔隙变形占较大比例,应力波能量大部分被消耗于孔隙变形,表明只有在高孔隙率和高应变率条件下内部孔隙才会发生明显的变形.孔隙离心率e可以较好地刻画应力波作用下孔隙的变形.  相似文献   

7.
目的研究刚地弓形虫RH株感染对BALB/c小鼠学习记忆行为的影响及可能机制。方法将72只周龄、大小相近的雄性BALB/c小鼠采用随机数字表分为生理盐水对照组与不同数量(3×10^3/ml、3×10^4/ml、3×10^5/m1)弓形虫RH株感染组,每组18只。于感染第5周从每组各随机抽取6只分别进行高架十字迷宫实验、旷场实验及强迫游泳实验,观察各组小鼠在实验中情绪行为变化。并记录各项指标进行统计分析。结果在高架迷宫试验与旷场实验中,3×10^3/ml弓形虫感染组小鼠与生理盐水对照组小鼠比较,各项行为学指标无明显差异。在3×10^4/ml、3×10^5/ml弓形虫感染组小鼠与对照组小鼠比较出现明显降低(P〈0.05).以3×10^5/ml感染组最为明显,其小鼠运动活力(0E+cE)、进入开放臂次数比例(OE%)、开放臂停留时间比例(OT%)小鼠爬行总格数、中央格在总格数中比例分别为11.08±2.12、28.73±0.59%、25.62±2.33%、32.30±17.26、2.42±0.65%。在强迫游泳试验中,各弓形虫感染组小鼠游泳的静止时间均高于对照组小鼠(P〈0.05),3×10^5/ml感染组静止时间最长,达226.6±1.9S。结论刚地弓形虫RH株感染可引起小鼠情绪行为改变,具有焦虑抑郁倾向。  相似文献   

8.
将棕榈油的提取物作为添加剂,分别以0.2%,0.4%和0.6%的体积比例加入基础汽油(辛烷值93的市售汽油)、已知成分汽油、乙醇汽油和甲醇汽油中,采用城市路况车用典型发动机转速2000r/min负荷特性下的台架试验,并对基础汽油中添加0.6%的添加剂油品进行道路试验,对加剂前后的汽油机燃油经济性和排放性进行了比较分析.结果表明:对于基础油和已知成分汽油,分别添加0.4%和0.2%比例的添加剂,其节油效果最大分别达到8.1%和10.2%;醇类汽油燃油消耗率高于纯汽油,E10和M10汽油分别比基础油的质量燃油消耗率高出3.1%和3.9%;在0.6%的添加比例下,M10和M20汽油燃油消耗率平均降低约为3.7%;道路试验平均节油约7.0%.同时通过定容燃烧弹、缸内燃烧过程分析、同步辐射以及高温摩擦试验等手段,从燃烧特性和摩擦学的角度初步探讨了这种生物基添加剂的节油机理.试验结果反映使用添加剂后可以提高最大缸内压力和增大燃烧放热率、改善排放,并且能够大幅度的降低摩擦系数.  相似文献   

9.
分别配制了Bi含量为90,100和110mole%的前驱体,在Pt/Ti/SiO2/Si衬底上制备Bi3.4Ce0.6Ti3O12薄膜,研究前驱体中Bi含量对其微观结构和铁电性能的影响.前驱体中Bi含量增加可以有效地改善薄膜的结晶性能和表面形貌.对Pt/Bi3.4Ce0.6Ti3O12/Pt电容结构进行电学性能测量,发现Bi过量10%的前驱体制备的Bi3.4Ce0.6Ti3O12薄膜具有较好的性能:室温下,在测试频率1kHz时,其介电常数为172,介电损耗为0.033;在测试电场为600kV/cm时,其剩余极化值(2Pr)和矫顽电场(2Ec)分别达到67.1gC/cm^2和299.7kV/cm;同时还表现出良好的抗疲劳特性和绝缘性能.  相似文献   

10.
通过塔里木河流域天山山区中部和西南部山区11个气象站以及开都-孔雀河、阿克苏河、喀什和叶尔羌绿洲共18个气象站的气象数据,对比分析了塔里木河流域山区和绿洲在1960-2006年间潜在蒸散发变化的不同趋势及气象因子的不同影响,并根据潜在蒸散发与山区降水、绿洲耗水之间的相互关系,分析了山区和绿洲潜在蒸散发变化趋势不同的原因.塔里木河流域山区和绿洲都具有潜在蒸散发下降的趋势,且潜在蒸散发的下降主要表现在其空气动力学项的减小,但绿洲潜在蒸散发的下降趋势明显强于山区.山区辐射和风速下降对潜在蒸散发的影响最为显著,而绿洲风速下降的影响最为显著.基于蒸散发互补相关理论分析发现,塔里木河流域山区和绿洲潜在蒸散发的下降分别与降水和绿洲耗水的增加紧密联系,反映了自然因素变化和人类活动对潜在蒸散发的不同影响.  相似文献   

11.
This paper is concerned primarily with the evaluation and comparison of objective and subjective weather forecasts. Operational forecasts of three weather elements are considered: (1) probability forecasts of precipitation occurrence, (2) categorical (i.e. non-probabilistic) forecasts of maximum and minimum temperatures and (3) categorical forecasts of cloud amount. The objective forecasts are prepared by numerical-statistical procedures, whereas the subjective forecasts are based on the judgements of individual forecasters. In formulating the latter, the forecasters consult information from a variety of sources, including the objective forecasts themselves. The precipitation probability forecasts are found to be both reliable and skilful, and evaluation of the temperature/cloud amount forecasts reveals that they are quite accurate/skilful. Comparison of the objective and subjective forecasts of precipitation occurrence indicates that the latter are generally more skilful than the former for shorter lead times (e.g. 12–24 hours), whereas the two types of forecasts are of approximately equal skill for longer lead times (e.g. 36–48 hours). Similar results are obtained for the maximum and minimum temperature forecasts. Objective cloud amount forecasts are more skilful than subjective cloud amount forecasts for all lead times. Examination of trends in performance over the last decade reveals that both types of forecasts for all three elements increased in skill (or accuracy) over the period, with improvements in objective forecasts equalling or exceeding improvements in subjective forecasts. The role and impact of the objective forecasts in the subjective weather forecasting process are discussed in some detail. The need to conduct controlled experiments and other studies of this process, with particular reference to the assimilation of information from different sources, is emphasized. Important characteristics of the forecasting system in meteorology are identified, and they are used to describe similarities and differences between weather forecasting and forecasting in other fields. Acquisition of some of these characteristics may be beneficial to other forecasting systems.  相似文献   

12.
Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.  相似文献   

13.
Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.  相似文献   

14.
Temperature changes are known to affect the social and environmental determinants of health in various ways. Consequently, excess deaths as a result of extreme weather conditions may increase over the coming decades because of climate change. In this paper, the relationship between trends in mortality and trends in temperature change (as a proxy) is investigated using annual data and for specified (warm and cold) periods during the year in the UK. A thoughtful statistical analysis is implemented and a new stochastic, central mortality rate model is proposed. The new model encompasses the good features of the Lee and Carter (Journal of the American Statistical Association, 1992, 87: 659–671) model and its recent extensions, and for the very first time includes an exogenous factor which is a temperature‐related factor. The new model is shown to provide a significantly better‐fitting performance and more interpretable forecasts. An illustrative example of pricing a life insurance product is provided and discussed.  相似文献   

15.
The hedging of weather risks has become extremely relevant in recent years, promoting the diffusion of weather‐derivative contracts. The pricing of such contracts requires the development of appropriate models for the prediction of the underlying weather variables. Within this framework, a commonly used specification is the ARFIMA‐GARCH. We provide a generalization of such a model, introducing time‐varying memory coefficients. Our model satisfies the empirical evidence of the changing memory level observed in average temperature series, and provides useful improvements in the forecasting, simulation, and pricing issues related to weather derivatives. We present an application related to the forecast and simulation of a temperature index density, which is then used for the pricing of weather options. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

16.
Density forecasts for weather variables are useful for the many industries exposed to weather risk. Weather ensemble predictions are generated from atmospheric models and consist of multiple future scenarios for a weather variable. The distribution of the scenarios can be used as a density forecast, which is needed for pricing weather derivatives. We consider one to 10‐day‐ahead density forecasts provided by temperature ensemble predictions. More specifically, we evaluate forecasts of the mean and quantiles of the density. The mean of the ensemble scenarios is the most accurate forecast for the mean of the density. We use quantile regression to debias the quantiles of the distribution of the ensemble scenarios. The resultant quantile forecasts compare favourably with those from a GARCH model. These results indicate the strong potential for the use of ensemble prediction in temperature density forecasting. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

17.
Using temperature-sensitive radio-telemeters chronically implanted in the abdomens of 8 fetal lambs and their mothers, we measured body temperature changes induced by parturition. Maternal body temperature rose at 0.70±0.06 °C/hour (mean±SEM) in the final stages of labour. Fetal body temperature also rose, but at a significantly lower rate, 0.45±0.06 °C/hour (p<0.05). The fetus appears to be protected from excessive hyperthermia during the birth process.  相似文献   

18.
Summary Diacylglycerol (DG) and triacylglycerol (TG) levels in rat lung tissue were determined from day 17 of gestation to day 10 post partum and studied in parallel with ultrastructural differentiation. The DG level, although rather low at all measured stages, rose significantly between days 17 and 19 and at birth. TG level increased steadily during the whole studied period and especially between days 17 and 19 and at birth. In DG as well as in TG, saturated fatty acids were predominant. The rising of TG levels paralleled the appearance and accumulation of lipid vacuoles in mesodermal cells lying in contact with type II cells. The possible role of these cells is discussed.  相似文献   

19.
J Romá  B Soria 《Experientia》1984,40(4):378-380
This report describes the effects of short treatments with isonicotinic acid hydrazide (isoniazid), 300 mg/kg/day, on conduction velocity in the rat tail dorsal nerve trunk. After 6 days of continuous treatment, conduction velocity falls significantly for measurements made at 35 degrees C. After 10 days it falls significantly at both 25 degrees C and 35 degrees C. This appears to be the first electrophysiological corroboration of the early neuropathological changes recently observed in isoniazid treated rats and seems to provide evidence that the temperature at which the experiments are made is important in determining conduction velocity changes.  相似文献   

20.
This study investigates the effect of the gamma-aminobutyric acid (GABAB) agonist, baclofen, on amygdala kindling in adult rats. Baclofen has been reported to be anticonvulsant in a variety of seizure models and prevents kindling in immature rats. These experiments describe the effects of baclofen (2, 5 and 10 mg/kg, i.p.) on the afterdischarge threshold and kindling rate. Baclofen, 10 mg/kg, significantly increased the afterdischarge threshold in the amygdala. Baclofen at 5 and 10 mg/kg, retarded the rate of kindling as measured by the number of stimuli required to advance to subsequent seizure stages. These results suggest that baclofen may decrease the local excitability of the amygdala and retard the rate of seizure spread (or generalization) throughout the brain. Baclofen, acting at GABAB receptors exerts an anticonvulsant effect on amygdala kindling in these experiments.  相似文献   

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