基于LESA体系的高标准基本农田建设时序研究

高标准基本农田建设地既要符合建设的内涵和要求,又要实际考虑研究区基础设施和社会经济条件.为了科学合理地进行综合评价和时序研究,论文以沈阳市沈北新区为例,借鉴美国土地评价与立地分析(LESA)思想,根据自身限制条件和耕地质量更新成果进行综合质量评价,自然质量因素选取有机质含量及土壤质地等,立地条件因素从基础设施条件和社会经济条件两方面选取,基础设施条件主要选取灌溉保证率,排水条件等,社会经济条件主要选取单位面积投入及农业技术人员投入等.在评价结果的基础上采用自然断点法与K-均值聚类法相结合的方法划分建设时序.结果表明,近期建设区占研究区的43.95%,主要进行农田基础设施建设,致力建设设施完备,高产稳产的现代化农田;中期建设区占研究区的25.01%,以提升自然质量为主导建设方向,建立协调发展的高产农田;远期建设区占研究区的31.04%,应全面展开建设,以提升农田综合质量达到高标准基本农田建设标准.     

诺卡氏菌株C-14-1中腈水解酶基因的鉴定、测序及分析

从腈纶废水中分离到高效降解多种污染物的诺卡氏菌株C-14—1,并对该菌中腈水解酶的基因进行鉴定和测序．利用红球菌中腈水解酶氨基酸保守区设计核苷酸引物,以菌株C-14—1的总DNA为模板,PCR扩增发现一条预期大小的DNA带．Southern杂交显示基因组中存在一个腈水解酶基因．进一步构建基因文库和菌落原位杂交,克隆到一个约4．5kb的DNA片段．DNA序列测定和分析表明,该DNA片段携带长度为1143bp的腈水解酶基因．比对分析表明,该基因与国际上发表的红球菌和诺卡氏菌中的腈水解酶基因高度相似．     

近江牡蛎等7种养殖鱼虾贝类参照基因b-肌动蛋白cDNA序列的克隆与比较分析

为进一步研究水产养殖动物功能基因的表达调控,采用RT-PCR及RACE法,分离、克隆了近江牡蛎(Crassostrea ariakensis)肝脏β-肌动蛋白基因cDNA全序列. 结果表明,近江牡蛎β-肌动蛋白基因cDNA全长1343bp,其中5′、3′非翻译区(UTR)分别长68bp、144bp,开放阅读框(ORF)为1131bp,编码376个氨基酸. 实验同时成功获得了中华圆田螺(Cipangopaludina cahayensis)、日本沼虾(Macrobrachium nipponensis)、斑鳢(Channa maculata)、胡子鲶(Clarias fuscus)、鳙鱼(Aristichthys nobilis)、鲮鱼(Cirrhinus molitorella)6种重要淡水养殖动物肝脏β-肌动蛋白基因cDNA的核心序列及氨基酸序列. 所获基因与其它动物类群的b-肌动蛋白基因氨基酸同源性高达96%以上,表明软体类、节肢类、鱼类、两栖类、鸟类和哺乳类等不同类群动物b-肌动蛋白基因在生物进化过程中高度保守. 系统发育分析显示软体类、节肢类、鱼类、两栖类、鸟类和哺乳类脊椎动物β-肌动蛋白分类与传统的分类基本一致.     

深海生物圈酵母菌的研究进展

从深海生物圈中酵母菌的来源状况、种类分布特征、研究方法等角度阐述了其最新进展,结合本课题组的相关研究,以便加强我们对深海生物圈中酵母菌的了解和认识,并提出开展该领域研究亟需解决的问题;希望本综述为开发利用深海酵母菌资源提供参考.     

高温菌的生理生化及其16S rDNA序列分析

利用高温菌耐热嗜热的特性和有机物好氧分解的基本原理,从厨余垃圾处理系统中分离筛选到6株在65℃能产生淀粉酶、脂肪酶、蛋白质酶及纤维素酶的高温高效菌种,并对其生理生化和16S rDNA进行了分析。结果表明:筛选出的6株高温菌,经鉴定都有芽孢,并具有兼氧性;对其进行16S rDNA区段序列测定显示,6株高温菌属于Geobacillus thermog lucosidasius菌种中的不同亚种;分离筛选出的高温菌经过2h的迟缓期后很快进入对数生长期,且持续时间较长,生长速度尤以HB6最快;6株高温菌株全部具有淀粉、纤维素、蛋白质降解活性,5株有脂肪降解活性。可见高温菌具有更高的有机物降解活性和更快的代谢速率,可提高有机物质的降解速率,缩短工艺运行时间,有利于工业化生产,在厨余资源化利用上具有广泛的应用前景。     

Generic event trees and probabilities for the release of different types of hazardous materials

To simplify quantitative risk analysis, the initiating events leading to loss of containment are normally described using generic hypotheses. For example, the following hypothesis is applied to the loss of containment from a storage tank: instantaneous release of the complete inventory, continuous release of the complete inventory in 10 min, and continuous release from a hole with a diameter of 10 mm. Once the initiating events have been specified, the corresponding event trees must be drawn to establish the sequences from each initiating event to the diverse final outcomes or accident scenarios, which will depend on the properties of the released material or on other specific factors. In this paper we propose, in a systematic way, a set of short generic event trees for the main loss of containment scenarios involving different types of hazardous materials. Even though most of them have been taken from the literature (BEVI Reference Manual), we have modified some of them, added the corresponding intermediate probabilities (immediate ignition, delayed ignition, flame front acceleration, etc.) obtained from a literature review and expert judgment, and associated the use of each event tree to the hazardous properties of the material (flammability, volatility and toxicity) and to its category according to EC labeling directives.     

基于灵敏度分析的斜拉桥拉索更换顺序研究

通过对部分换索桥梁换索顺序的调研,按照拉索不同的布置形式,总结了目前拉索更换所采用的主要顺序,并利用有限元分析方法对某双塔双索面斜拉桥进行了模拟换索,分析得到了偏于安全的换索顺序。通过拆单根索的弯曲应变能的变化,分析了斜拉桥换索的整体顺序。通过分析不同换索工况下的索力增量变化规律,包括单塔拆1根、双塔同侧索面对称拆4根、双塔不同侧索面反对称拆4根等3种工况,对拉索更换顺序进行了研究,并对其中的同侧索面和不同侧索面拆除4根拉索的工况进行了主梁线形的分析,建立了有限元模型。分析认为,斜拉桥拉索的更换宜从短索向长索反对称进行。     

Differences in soil nitrification and denitrification capacities following reclamation years of native desert soils to irrigated croplands in Hexi Corridor Region of Northwest China北大核心CSCD

Nitrogen (N) loss in irrigated croplands from coupled nitrification and denitrification shows considerable differences due to differences in soil properties and agricultural management practices. Previous research has demonstrated that soil physicochemical properties strongly affect nitrification and denitrification capacities of cropland soils. However, existing research on soil nitrification and denitrification following the conversion of native desert soils to irrigated croplands lacks long-term tracking and monitoring capabilities. Therefore, six types of reclamation years of irrigated croplands and uncultivated sandy land in the Hexi Corridor marginal oasis in northwestern China were selected for study, and the differences in soil nitrification and denitrification rates and physicochemical properties were studied over 42 sites in the desert-oasis ecotone derived from seven reclamation sequences, including the years of 0, 15, 30, 50, 80, 100, and 150. The results showed that the nitrification and denitrification rates of soil first increased and then decreased with the increase in reclamation years. The highest soil nitrification rate and denitrification rate were observed at 80 years of cultivation (101.4 μg g-1 d-1) and 100 years of cultivation (0.93 μg g-1 d-1), respectively. In addition, the soil nitrification and denitrification rates in the natural sandy land were significantly lower than those in the cultivated croplands (P < 0.05). There were significant correlations among soil nutrients, soil moisture, and soil particle size composition between the nitrification and denitrification rates (P < 0.05). Regression analysis showed that environmental variables accounted for 69.7% and 75.7% of the variation in nitrification and denitrification rates, respectively. Among them, organic matter content, pH, soil moisture, and NH4+-N content were the key factors affecting the change in soil denitrification rate, while organic matter content, NO3--N, pH, and clay content were the key factors affecting the change in soil denitrification rate. © 2022 Science Press. All rights reserved.     

自回归模型在井水埋深预测中的应用及改进

用时间序列分析方法建立井水埋深的预测模型时,首先采用差分的方法把季节性时间序列变成平稳时间序列,在此基础上,再用动态数据系统方法的传统F检验定阶法进行分析。由于样本的随机性可能过早地退出对模型的循环检验,从而不能找到合适的预测模型。笔者在用自回归模型建立井水预测模型的基础上,采用了一种改进的建模方法,提高了预测精度,并用实例进行了验证。     

SBR处理城市生活污水的试验研究

通过序批式活性污泥法 ( SBR)工艺处理城市生活污水的试验 ,研究了不同操作方式对处理效果的影响并得出最佳运行参数。当采用最佳操作方式运行时 ,COD、TP、TN的去除率分别为 90 % ,90 % ,75 %以上 ,出水能达到国家一级排放标准。