MI琼脂法同时检测环境水样中总大肠菌群和大肠埃希氏菌     

嵇志远  王维玮  文扬 《岩矿测试》2013,32(5):747-752

总大肠菌群和大肠埃希氏菌是表征环境水样中粪便污染的两个重要指标。对这两个指标的检测,传统的多管发酵法和滤膜法已经无法满足快速、准确的检测要求。而近年来能够快速测定的固定酶底物技术(DST)已经在国内开始运用,但是由于其检测成本较高,影响了其在基层实验室的推广,MI琼脂法的出现较好地弥补了这个缺陷。本文应用MI琼脂法检测环境水样中总大肠菌群和大肠埃希氏菌,对其方法性能进行了测试和研究,选择国家标准方法——远藤琼脂法作为比较对象,通过菌种加标回收试验比较MI琼脂法和远藤琼脂法的灵敏度差异,通过实际水样的检测验证MI琼脂法和国标法是否具有等效性。结果表明:使用MI琼脂法检测总大肠菌群和大肠埃希氏菌加标样品的平均回收率分别为89.2%和88.8%,分别高于远藤琼脂法的81.0%和81.2%,证明MI琼脂法的灵敏度高于远藤琼脂法。MI琼脂法和远藤琼脂法检测总大肠菌群和大肠埃希氏菌的相关系数分别为0.9627和0.9511,都具有显著相关性,且检测结果没有统计学意义上的差异,证明两种方法检测总大肠菌群和大肠埃希氏菌具有等效性。与国家标准方法相比,MI琼脂法具有灵敏度高、操作简便、检测周期短、检测成本低、可同时检测两个指标等优点,可以替代传统的滤膜法作为检测总大肠菌群和大肠埃希氏菌的新方法。  相似文献   

An objective prediction model for typhoon rainstorm using particle swarm optimization: neural network ensemble     

Hua-sheng Zhao  Long Jin  Ying Huang  Jian Jin 《Natural Hazards》2014,73(2):427-437

A nonlinear ensemble prediction model for typhoon rainstorm has been developed based on particle swarm optimization-neural network (PSO-NN). In this model, PSO algorithm is employed for optimizing the network structure and initial weight of the NN with creating multiple ensemble members. The model input of the ensemble member is the high correlated grid point factors selected from the rainfall forecast field of Japan Meteorological Agency numerical prediction products using the stepwise regression method, and the model output is the future 24 h rainfall forecast of the 89 stations. Results show that the objective prediction model is more accurate than the numerical prediction model which is directly interpolated into the stations, so it can better been implemented for the interpretation and application of numerical prediction products, indicating a potentially better operational weather prediction.  相似文献   

强震时空统计分析及InSAR同震形变场空间分布特征          下载免费PDF全文

卞畏畏  伍吉仓  张磊  高宇 《武汉大学学报(信息科学版)》2022,47(6):875-886

收集整理了全球1976年至2022年初的198个强震（Mw≥7.5）信息,统计分析了强震发生的时空分布、震源深度分布和强震发震类型占比,并结合公开发表的典型强震的合成孔径雷达干涉测量（interferometric synthetic aperture radar,InSAR）同震形变场图,分析了强震同震形变的空间分布特征。研究表明,强震空间分布呈条带状聚集,主要位于环太平洋地震带和喜马拉雅-地中海地震带,强震大多发生在各大板块交界处,与现代大地测量观测到的地壳强应变区域重合;强震时间分布存在活跃期和平静期交替出现的现象,1976―1992年为相对平静期,1992年至今为相对活跃期,强震发生频率有逐年增加趋势;在收集的全球198个强震中,发生在海洋中的强震占大多数,陆地强震仅有44个,且绝大多数强震属于逆冲断层地震,按震源深度统计,浅源强震最多且分布广泛,占比达81.3%;InSAR卫星对地观测新技术可以捕获强震的全域同震形变场,详细呈现强震同震形变的空间范围和分布特征,其中陆地强震同震形变波及的范围主要集中在发震断层两侧附近的条带状区域,离断层越远,形变衰减越快,而且形变关于断层呈不对称性。运用全球覆盖的InSAR和全球导航卫星系统地壳形变监测技术,拼接全球不同位置的活动断层形变信息片段,有可能揭示陆地强震的全周期孕震形变过程。  相似文献   

干旱区城市化与生态韧性耦合协调的时空格局演化分析——以宁夏为例          下载免费PDF全文

李苏  刘浩南 《干旱区地理》2022,45(4):1281-1290

快速城市化易引发各种生态问题,如何构建城市化与生态韧性的协调发展关系对于干旱区内陆城市的发展至关重要。结合遥感技术从韧性角度解读城市化与生态环境,以宁夏为研究区域,在构建城市化与生态韧性指数的基础上,运用耦合协调性和相对发展度模型对2005—2020年两者的耦合协调性进行研究。结果表明：（1） 宁夏城市化水平提升较快,以银川市为中心的沿黄城市群灯光璀璨,而宁夏南部呈现众多面积较小零星分布的灯光像元。（2） 宁夏生态韧性水平整体稳中有升。银川市生态韧性水平全区最高,吴忠市次之,石嘴山市、固原市和中卫市生态韧性水平则相对较低。（3） 宁夏城市化与生态韧性耦合协调性稳步提升,除银川市和石嘴山市外,其余各市均经历了不同程度的失调期。（4） 宁夏城市化和生态韧性的相对发展尚未达到理想上的等同。  相似文献   

赣江下游污染负荷与水质响应关系模型          下载免费PDF全文

周刚  黑鹏飞  雷坤  富国  乔飞 《水科学进展》2013,24(6):883-893

为了研究赣江下游入河污染物对河流水质的影响,建立了基于WASP（Water quality Analysis Simulation Program）模型富营养化原理和ELADI（Eulerian-Lagrangian Alternating Direction Implicit Method）有限差分方法的正交曲线平面二维水环境模型WESC2D（Two-Dimensional Water Environment Simulation Code）。模型采用基于双线性插值及亚网格技术的欧拉-拉格朗日方法求解对流项,在简单的浓度峰输运和赣江下游溶解氧变化过程算例检验的基础上,计算与分析了赣江下游入河排污口氨氮污染负荷与水质之间的动态响应关系。模拟与分析结果表明,WESC2D模型的计算结果与解析解吻合良好,有效地减少了欧拉-拉格朗日方法的数值耗散,并为赣江下游污染负荷与水质响应关系计算提供了重要工具。  相似文献   

沙漠化地区两种生态治理政策交易成本的比较研究     

樊胜岳  赵丹华  兰健  徐均 《中国沙漠》2013,33(4):1211-1216

本文将交易成本分析引入沙漠化地区生态治理政策分析过程,构建生态治理政策交易成本分析框架,确定交易成本计算方法,估算内蒙古乌审旗退耕还林政策执行期间的交易成本为每年4 931.92元·hm-2。其中,政府直接支付占交易成本的50.06%,农户支付占交易成本的46.86%,政府直接支付是退耕还林机会成本的118.75%。草原休牧政策执行期间的交易成本为每年906.07元·hm-2,政府直接支付占交易成本的12.86%,农户支付占交易成本的80.35%,政府直接支付是草原休牧机会成本的23.30%。退耕还林政策的政府支付与退耕还林的机会成本大致相同,因此该政策执行效果良好,并且实现了退耕还林地区的全面禁牧。草原休牧政策的政府支付达不到休牧机会成本的1/4,牧民利益受到损失,牧民偷牧率达到100%,致使草原休牧流于形式。生态治理政策的交易成本分析,将为不同生态治理政策的比较和绩效评价提供一个新的角度,具有重要意义。  相似文献   

海带渣资源化利用及在小球藻培养中的应用研究     

王铭  彭敏琳  许瑾  梁翠谊  向文洲  李涛 《海洋与湖沼》2022,53(1):96-105

海带渣是海带加工中的固体废弃物,将其资源化利用生产高附加值产品具有重要意义.文章以海带渣为原料,糖化液的总还原糖质量浓度、单糖组成和小球藻培养效果为主要评估指标,探究不同预处理方法对海带渣酶解的影响,以及海带渣资源化利用培养微藻工艺的可行性.结果 显示:(1)粗纤维和灰分是海带渣主要组成成分;(2)常温常压稀硫酸预处理...  相似文献   

Morphological responses in a meandering and island-braided reach of the Middle Yangtze River to the Three Gorges Reservoir impoundment     

《国际泥沙研究》2016,(2):131-138

Lateral migration is an important form of morphological changes on the Middle Yangtze River (MYR), particularly for the lower Jingjiang reach. The Three Gorges Reservoir (TGR) has substantially reduced sediment supply to the downstream river channels since its impoundment in June 2003. The scientific understanding of how decrease of sediment influences the processes of bank erosion and channel adjustments is complex and limited. In the present paper, the morphological responses in a typical meandering and island-braided river segment of the MYR to the filling of the TGR were investigated by a 3-D morphodynamic model. The potential of the 3-D model has been demonstrated by the observed data. The morphological evolutions in the Shishou bend during the first 12 years of the TGR impound-ment were predicted. The effects of the TGR operation on the planform evolutions in the study reach were analyzed based on the simulated results. Sediment load is decreased by 75%due to the early filling of the TGR. The magnitude of bed degradation with less sediment load due to the TGR operation is increased compared with the pre-dam situation. Qualitatively, the overall planform evolution trends in the Shishou bend after the TGR operation are similar to that without the TGR operation. The magnitude of lateral migration has been increased in some part of the channel bend, where the morphological response of the TGR operation exhibits more lateral migration rather than vertical degradation. Scouring at the bank toe enhances bank failure. Decrease of sediment load and weak bank anti-scour ability as well as the significant helical flow can be responsible for intensified bank erosion in the channel bend.  相似文献   

б-sharpen immersed boundary method(б-SIBM)—New method for solving the horizontal pressure-gradient force(PGF) problem of б-coordinate     

HEI PengFei  ZHOU Gang  JIA DongDong  YE YunTao  LEI Kun 《中国科学:地球科学(英文版)》2014,57(7):1681-1691

Althoughб-coordinate is one of the most popular methods used in marine and estuarine modeling,it has long suffered from the so-called"steep boundary problem",namely,the PGF problem.In this paper,a new method called the"б-sharpen immersed boundary method"(б-SIBM)is put forward.In this method,the virtual flat bottom boundary is creatively introduced in regions with the steep boundary and is taken as the boundary of numerical domain.By this,бHбx of numerical domain changes to be a controllable value and the steep bottom problem is then transformed to the non-conforming boundary problem,which is,in turn,solved by the SIBM.The accuracy and efficiency of theб-sharpen immersed boundary method(б-SIBM)has been showed by both comparative theoretical analysis and classical numerical tests.First,it is shown that theб-SIBM is more effective than the z-level method,in thatб-SIBM needs special treatment only in the steep section,but the z-level method needs the special treatment in each grid note.Second,it is superior to theб-method in that it is not restricted by the density distribution.This paper revisits the classical seamount numerical test used in numerous studies to prove the sigma errors of the pressure gradient force(PGFE)and their long-term effects on circulation.It can be seen that,as for the maximum erroneous velocity and kinetic energy,the value ofб-SIBM is much less than that of the z-level method and the traditionalб-method.sharpen immersed boundary method(SIBM),immersed boundary method(IBM),direct forcing method,б-coordinate,  相似文献   

Weak lensing of the CMB: extraction of lensing information from the trispectrum     

《New Astronomy》2003,8(3):231-253

We discuss the four-point correlation function, or the trispectrum in Fourier space, of CMB temperature and polarization anisotropies due to the weak gravitational lensing effect by intervening large scale structure. We discuss the squared temperature power spectrum as a probe of this trispectrum and, more importantly, as an observational approach to extracting the power spectrum of the deflection angle associated with the weak gravitational lensing effect on the CMB. We extend previous discussions on the trispectrum and associated weak lensing reconstruction from CMB data by calculating non-Gaussian noise contributions, beyond the previously discussed dominant Gaussian noise. Non-Gaussian noise contributions are generated by lensing itself and by the correlation between the lensing effect and other foreground secondary anisotropies in the CMB such as the Sunyaev–Zel’dovich (SZ) effect. When the SZ effect is removed from temperature maps using its spectral dependence, we find these additional non-Gaussian noise contributions to be an order of magnitude lower than the dominant Gaussian noise. If the noise-bias due to the dominant Gaussian part of the temperature squared power spectrum is removed, then these additional non-Gaussian contributions provide the limiting noise level for the lensing reconstruction. The temperature squared power spectrum allows a high signal-to-noise extraction of the lensing deflections and a confusion-free separation of the curl (or B-mode) polarization due to inflationary gravitational waves from that due to lensed gradient (or E-mode) polarization. The small angular scale temperature and polarization anisotropy measurements provide a novel approach to weak lensing studies, complementing the approach based on galaxy ellipticities.  相似文献