基于MATLAB的BP神经网络模型在漠阳江水质评价中的应用研究

为提高水质评价的准确性,基于MATLAB及人工神经网络理论,采用误差反向传播的BP算法建立漠阳江水质评价模型,充分利用神经网络的非线性映射特性,取7项常规地表水水质评价指标对漠阳江水质进行评价,并将BP神经网络评价结果与单因子评价法及综合指数法的评价结果进行比较,网络运行结果表明一致效果良好.同时较传统的水质评价方法,该网络具有较高的识别精度,提高了水质评价等级的准确性,使评价的结果更具有科学性.     

Ammonium-dependent regulation of aerobic methane-consuming bacteria in landfill cover soil by leachate irrigation

The impacts of landfill leachate irrigation on methane oxidation activities and methane-consuming bacteria populations were studied by incubation of landfill cover soils with leachate and (NH₄)₂SO₄ solution at different ammonium concentrations. The community structures and abundances of methane-oxidizing bacteria (MOB) and ammonia-oxidizing bacteria (AOB) were examined by PCRDGGE and real-time PCR. Compared with the pure (NH₄)₂SO₄ solution, leachate addition was found to have a positive effect on methane oxidation activity. In terms of the irrigation amount, ammonium in leachate was responsible for the actual inhibition of leachate. The extent of inhibitory effect mainly depended on its ammonium concentration. The suppression of the predominant methaneconsuming bacteria, type I MOB, was responsible for the decreased methane oxidation activity by ammonium inhibition. Methaneconsuming bacteria responded diversely in abundance to ammonium. The abundance of type I MOB decreased by fivefold; type II MOB showed stimulation response of fivefold magnification upon the first addition but lessened to be lower than the original level after the second addition; the amount of AOB was stimulated to increase for 20-30 times gradually. Accumulated nitrate from nitrification strengthened the ammonium inhibition on type I and type II MOB, as a result, repetitive irrigation was unfavorable for methane oxidation.     

基于农村信用体系建设的涉农经济组织和农户信用提升研究

我国涉农经济组织和农户的信用存在一些难以规避的缺陷,导致农业贷款难的困境。本文从涉农经济组织和农户信用道德建设,信用制度与法律建设,产权制度,信用环境,信用标准及信用等级评定,信用组织创新,征信和信用担保中介服务市场,农村信用管理等八个方面阐述了农村信用体系建设的基本思路,并讨论了涉农经济组织和农户的信用提升问题。     

基于CI指数的祁东县干旱特征分析

利用衡阳市祁东县气象站1960~2013年逐日平均气温、降水观测数据,计算综合气象干旱指数。以国家标准《气象干旱等级GB/T20481~2006》为依据划分不同干旱等级、计算干旱日数、干旱强度等,在此基础上统计干旱日的年、年代际统计并作了线性分析,并为应对干旱提出了自己的建议:祁东县干旱日每年均有出现,但不同强度干旱日发生频率不同,在全球变暖大背景下,干旱日等级越高,其增幅愈明显;祁东县的平均干旱过程数为2.5次/a,一年出现2次干旱过程几率最大,无旱过程的几率为9.3%;在统计年干旱强度时,选用持续时间最长的一次有较好代表性。近54a来,干旱强度年变化可分为三高两低,目前处于干旱强度较高期;祁东县大部分年份有季节性干旱,单季旱以秋旱为主,在双季干旱中,夏秋连旱居多,历史上夏秋冬连旱出现了三次;为了应对日趋严重的干旱,需增强人们的防旱抗灾意识、加大水利设置投入、推广节水农业和提高干旱监测预警能力。     

Abundance patterns and foraging activity of ant communities in abandoned,organic and commercial apple orchards in Northern California

The abundance patterns of ant communities were monitored with pitfall traps during 14 weeks in four northern California, dry farmed, apple orchards: an abandoned orchard undisturbed for 25 years, two ‘organically’ managed orchards, one with a cover crop of bell beans (Vicia faba) and grasses and the other kept clean of cover by discing, and a ‘commercial’ clean cultivated orchard sprayed with organophosphate insecticides. Six species of ants coexisted in the abandoned orchard, whereas only two species were found in the managed orchards. In both the organic and sprayed, clean cultivated systems, ants were more abundant in the orchard edges than in the vegetation-free centers. This trend was not apparent in the abandoned or organic cover orchards, where plant diversity in the center was similar to that of the edges. Ant predation on potato tuberworm larvae, Phthorimaea operculella, artificially placed on the orchard floor, declined with the intensity of management and vegetational simplication. A higher incidence of larval removal occurred in the edges than in the centers of the clean cultivated orchards. No noticeable populations of ants were detected on the trees in any of the orchards. Increased vegetational diversity and lack of disturbance appeared to affect ant locomotory activity and foraging efficiency by creating preferred sheltering and feeding sites.     

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The Science of Nature -     

Prenatal diagnosis of endocardial fibroelastosis

In a case of fetal heart failure caused by endocardial fibroelastosis, prenatal echocardiography clearly demonstrated; a thickened endocardium. We therefore suggest that an abnormal endocardium may be detected in utero by ultrasound, thus representing an important clue in the differential diagnosis of fetal nonimmune hydrops and in the evaluation of pregnancies at risk for endocardial fibroelastosis.     

Evaluation of inorganic pyrophosphate in amniotic fluid as a mode of prenatal diagnosis of osteogenesis imperfecta

Using a modified procedure by Solomons and Styner (1969), an evaluation of inorganic pyrophosphate (PPi) was performed on the amniotic fluid of two fetuses at risk for osteogenesis imperfecta (OI) at 14½ weeks gestation. The parents of both cases had a previous child with OI, Type II. The normal control group at 14–16 weeks gestation had PPi values ranging from 22.0–59.2 ug/100 ml, with a mean of 38.6±9.51 ug/100 ml. In each at-risk fetus, the amniotic fluid PPi value was within normal range. The first baby was born phenotypically normal at term. Intrauterine radiographic and fetal sonograms were done on the second fetus at approximately 19 weeks gestation. Both showed evidence of OI, Type II. The pregnancy was terminated at 21 weeks. Radiologic studies of the aborted fetus were consistent with OI, Type II. Our results indicate that the evaluation of PPi levels in amniotic fluid is not the method of choice for prenatal diagnosis of IO.