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1.
To search natural compounds having inhibitory effect on bacterial growth is important, particularly in view of growing multidrug resistant (MDR) strains of bacterial pathogens. Like other bacterial pathogens, MDR Vibrio cholerae, the causative agent of diarrheal disease cholera, is becoming a great concern. As an approach of searching new antimicrobial agents, here, we show that anethole, a well-studied natural component of sweet fennel and star anise seeds, could potentially inhibit the growth of MDR O1 El Tor biotype, the ongoing 7th cholera pandemic variant strains of toxigenic V. cholerae. The minimum inhibitory concentration (MIC) of anethole against diverse O1 El Tor biotype strains is evaluated as 200 µg/ml. Moreover, the effect of anethole is bactericidal and exerts rapid-killing action on V. cholerae cells. This study is the first report which demonstrates that anethole, purified from natural compound, is a potent inhibitor of growth of toxigenic V. cholerae. Our data suggest that anethole could be a potential antimicrobial drug candidate, particularly against MDR V. cholerae mediated infections.  相似文献   
2.
为了揭示赤道中、东太平洋海温的冷暖交替异常变化特征,以及它对长治市降水量和气温的影响,笔者根据1961年以来长治市11个县站的降水和气温资料,分析1961年以来长治市年降水量和气温的变化趋势,研究了厄尔尼诺事件/拉尼娜事件的发生和变化,以及厄尔尼诺/拉尼娜事件对长治市年降水量和年平均气温以及旱涝灾害的影响。结果表明:(1)1961—2014年分别有15次ElNino事件和14次LaNina事件发生,发生概率分别为0.28和0.26;暖事件发生强度要大于冷事件发生的强度。(2)厄尔尼诺事件主要发生在春夏季,结束于秋冬季;拉尼娜事件主要发生在春—秋季,结束于春冬季。(3)长治市年降水异常年份均出现在厄尔尼诺/拉尼娜事件发生年或结束年,且厄尔尼诺开始年和结束年所对应的气候异常相反。(4)长治市年平均气温的高低与拉尼娜年有较好的对应关系。(5)长治市大旱大涝与厄尔尼诺/拉尼娜事件有极其密切的关系。  相似文献   
3.
本文根据我国西北不同地区近50年来气象观测资料,研究了该区沙尘暴活动特点及其与气候变化的关系。结果表明:近五十年来我国西北沙尘暴发生总体呈波动减小趋势,这主要与新疆和内蒙古等沙源区向暖湿方向发展有关,而1999—2002年沙尘暴活动增强的主要原因是降水减少和气温升高。气候要素中的降水量变化与沙尘暴的发生有着极其密切的关系,二者呈明显的负相关;气温的高低也与沙尘暴的发生呈负相关,但没有与降水量的关系明显。在沙尘暴多发的60—70年代,沙尘暴日数减少与春季降水量的增加关系密切;而在80—90年代,冬干气候对沙尘暴日数增加作用明显。在沙尘暴多发的60—70年代,拉尼娜年对沙尘暴日数有明显的减少作用;相反,在沙尘暴较少的80—90年代,厄尔尼诺年对沙尘暴日数有明显的增加作用。  相似文献   
4.
Phosphite has been shown to suppress some diseases in different plant species but disease control in rice has not been investigated. In 2012/13 and 2013/14 potassium phosphite was sprayed at 1775 g ha−1 and 3550 g ha−1 in field plots of rice in Uruguay to determine if phosphite alone or in combination with label rates of a mixed strobilurin and triazole fungicide could be used to effectively control stem rot and aggregate sheath spot in irrigated rice. Six treatments consisting of different combinations of potassium phosphite alone or with a fungicide and an unsprayed control were assayed in one application at late-boot to early-heading. Phosphite alone in single and double rate slightly reduced severity and incidence of stem rot and produced a small yield increase over the unsprayed control. Fungicide at a 50% label rate with phosphite reduced stem rot severity and incidence to a similar level as the fungicide alone applied at the label rate. Disease severity was reduced by approximately 25% and incidence by 17–20% when compared with untreated control. Yield increase was 5% for both treatments over the unsprayed control. Fungicide combined with phosphite at single and double rates reduced stem rot severity by 40–45% and incidence by 34–38% when compared with untreated control, with yield increased by 10% over the unsprayed control and 5% over plots treated with a fungicide. These results indicate that a single application of potassium phosphite combined with fungicide can be used efficiently to manage of rice stem diseases.  相似文献   
5.
Long-term monitoring of physical and biological parameters is essential for understanding the effects of El Niño on bird populations, particularly for small or declining populations. We examined the biological effects of El Niño activity from 1965 to 2004 using instrumental sea-surface temperatures from the Galápagos Islands and 20 years of census counts of the Galápagos penguin. Between 1965 and 2004, nine El Niño events were recorded of which two were strong and seven were weak. The two strong El Niño events of 1982-1983 and 1997-1998 were followed by crashes of 77% and 65% of the penguin population, respectively. The evidence suggests that the increased frequency of weak El Niño events limits population recovery. The 2004 penguin population is estimated to be at less than 50% of that prior to the strong 1982-1983 El Niño event. We discuss the biological effects of increased El Niño intensity and frequency within the context of a 6000-year record of El Niño influence and in the light of increasing anthropogenic threats operating after 1535, when the Archipelago was discovered by Europeans.  相似文献   
6.
Larval and early juvenile fishes were sampled from the eastern Bering Sea (EBS) shelf during summer from 1996 to 2000. Data from these collections were used to examine spatial and temporal patterns in species assemblage structure and abundance. Cluster analyses based on Bray–Curtis dissimilarity coefficients were used to group species and stations according to similar abundance and species composition. Ordination techniques were used to verify groupings, and a non‐parametric stepwise procedure using a Spearman correlation coefficient (BIO‐ENV) was used to relate groupings to predominant environmental variables. These approaches revealed a pattern of station groupings that were generally related to bathymetry in 1996, 1997, 1999, and 2000, although no obvious relationship to geographic boundaries was observed in 1998. Significant differences in species associations were observed in 1997 and 1998, and depressions in abundance were also noted among many species between 1997 and 1999. A regional, full primitive equation model was used to simulate float trajectories on the EBS shelf in each year to better relate fish distributional observations to prevailing current patterns. Model results indicated general variations in flow in several years, although 1998 stood out with stronger northeast flow than in any of the other years examined. Observed disruptions of larval and early juvenile fish assemblages could be related to the strong El‐Niño event of 1997–98 in the EBS. If this idea is confirmed, our study suggests that larval and juvenile fish are sensitive and respond relatively quickly (1–2 yr) to environmental perturbations, and as such, may be timely indicators of environmental change.  相似文献   
7.
厄尔尼诺/拉尼娜事件对青海湖周边地区气候的影响   总被引:2,自引:0,他引:2  
根据1961年来青海湖周边地区的气温和降水量资料,结合小波分析和ENSO事件的发生与变化,研究了1961年来青海湖周边气温与降水的变化趋势,以及厄尔尼诺/拉尼娜事件对该区气温、降水量以及旱涝灾害的影响.结果表明,1961年来青海湖周边地区的年降水量呈波动上升趋势,西部最显著,年降水量以8.73 mm/10 a的速率增加.该地区的年平均气温呈波动上升趋势,平均气温增温率接近或明显高于全国平均水平.1988-2010年多年平均气温比1961-1987年增加更显著.小波分析显示,青海湖周边地区降水变化周期约为3,7和17a,气温变化的周期约为3,7和29 a.不同研究区域的降水量和气温变化与ENSO事件相关性不同.研究数据表明,青海湖周边地区厄尔尼诺年发生涝灾多于旱灾,而拉尼娜年多发生旱灾.1961-2009年青海湖水位总体趋势在下降,2005年后出现回升,流域降水量对湖水位的年变化有显著影响.  相似文献   
8.
利用常规观测资料,分析2009/2010年内蒙古冬季低温的特征。并通过对欧亚地区大气环流、影响我国的冷空气活动、北极涛动指数和EI Nino年内蒙古冬季气温的分析,探讨此次低温的气候成因。结果表明:此次冬季低温是内蒙古自1986年以来范围最广、时间最长、强度最大的一次冬季低温。强降温的同时,还伴随着强降雪和大风沙尘天气。地面西伯利亚高压偏强、850 hPa内蒙古北侧偏北气流偏强、500 hPa位势高度场偏低、东亚大槽位置偏西偏强以及强冷空气活动频繁是造成此次低温的主要原因。此次低温还与北极涛动指数负异常和EI Nino事件有关。  相似文献   
9.
福建省马尾松毛虫发生与ENSO事件的关系   总被引:4,自引:1,他引:4  
以1971~1991年(反)厄尔尼诺事件、南方涛动指数及福建省马尾松毛虫发生程度的资料为基础,探讨它们之间的关系,揭示这种关系产生的内在机制,并建立福建省马尾松毛虫发生预测预报模型.结果表明:福建省马尾松毛虫发生与(反)厄尔尼诺事件年、南方涛动指数总和变动异常年有显著关联;所建立模型精度达83.33%,可以对马尾松毛虫发生、气候异常起监测作用.  相似文献   
10.
鲐鱼(Scomber japonicus)是中上层经济鱼类,也是我国近海重要的捕捞对象,其资源分布受不同尺度气候和海洋环境变化的显著影响。本文根据2005-2016年7-9月中国远洋渔业数据中心提供的我国东海鲐鱼捕捞数据,结合关键因子海表面温度(sea surface temperature,SST),计算各年鲐鱼渔场经纬度重心,量化鲐鱼渔场重心的时空变化。进一步分析了捕捞努力量在经度、纬度以及SST上的分布规律,并基于聚类法筛选出代表年份评估异常气候事件对鲐鱼渔场内SST及渔场重心时空分布的影响。研究结果显示,鲐鱼渔场重心具有显著的年际和月间变化,7-9月渔场逐渐向东北方向移动,且主要分布在SST为25~28°C范围内。聚类分析将各月份渔场重心分为四类,其中2007和2015年渔场分布具有显著差异。此外,鲐鱼渔场内SST与尼诺指数具有显著的正相关关系,且代表年份2007和2015年分别对应拉尼娜事件和厄尔尼诺事件,当拉尼娜事件发生时,渔场内SST上升,渔场重心逐渐北移;而厄尔尼诺事件发生时,渔场内SST下降,渔场重心主要分布在南部海域。研究表明,中国东海鲐鱼渔场时空分布受到厄尔尼诺和拉尼娜调控的海表温度变化的显著影响。  相似文献   
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