Molecular characterizations of oxytetracycline resistant bacteria and their resistance genes from mariculture waters of China   总被引：1，自引：0，他引：1  

Dang H  Zhang X  Song L  Chang Y  Yang G 《Marine pollution bulletin》2006,52(11):1494-1503

Oxytetracycline-resistant bacteria were isolated from a mariculture farm in China, and accounted for 32.23% and 5.63% of the total culturable microbes of the sea cucumber and the sea urchin rearing waters respectively. Marine vibrios, especially strains related to Vibrio splendidus or V. tasmaniensis, were the most abundant resistant isolates. For oxytetracycline resistance, tet(A), tet(B) and tet(D) genes were detected in both sea cucumber and sea urchin rearing ponds. The dominant resistance type for V. tasmaniensis-like strains was the combination of both tet(A) and tet(B) genes, while the major resistance type for V. splendidus-like strains was a single tet(D) gene. Most of the sea cucumber tet-positive isolates harbored a chloramphenicol-resistance gene, either cat IV or cat II, while only a few sea urchin tet-positive isolates harbored a cat gene, actually cat IV. The coexistence of tet and cat genes in the strains isolated from the mariculture farm studied was helpful in explaining some of the multi-resistance mechanisms.  相似文献   

陕北侏罗纪煤田地下水保护对策与开采利用方案 研究          下载免费PDF全文

党学亚  张茂省  董英  顾小凡 《地学前缘》2010,17(6):200-207

矿山开采活动中地下水与生态环境保护是需要综合利用多学科思想与理论解决的难题,仅从采矿工程学角度难以解决根本问题。文中从生态水文地质学的角度,针对陕北采煤安全必须疏排水和陕北能源基地建设亟须水资源支撑的现状,提出了通过充分地利用煤田地下水满足强劲用水需求来保护水资源的对策,并从矿区水文地质结构、地下水循环条件出发,根据矿区植被生态风险区划、采煤影响地下水区划,提出了建立保护矿山水资源的采煤秩序、不同阶段地下水保护与开发利用区划以及矿山掘进过程中保护性开采地下水的水源地布局规划原则与建设方案。  相似文献   

Assignment of groundwater level at the wastewater collecting pipe for a landfill groundwater simulation: utilization of the two-dimensional saturated–unsaturated groundwater numerical model     

Thuong Huyen Dang  Kenji Jinno  Atsushi Tsutsumi 《Environmental Earth Sciences》2010,60(8):1575-1582

In order to understand the effects of a landfill operation on groundwater flow behavior, a 2D horizontal groundwater simulation model was carried out. The model saved the memory of computer and time consumption, comparing it with the 3D groundwater flow model. However, the greatest difficulty is the assignment of the collecting pipe boundary at the study site. Therefore, a 2D vertical model was applied to calculate the change of the groundwater table above the collecting pipe. This paper focuses on examining the validation of the assignment of the collecting pipe boundary by applying the results of the 2D vertical model. The 2D horizontal model was coupled with the recharge model to solve the partial differential equation of groundwater flow. The finite difference method and iterative successive over relaxation were applied. The drainage volume of leachate collection was summed up in the whole landfill site and compared with the average volume of treated wastewater. The study demonstrated that the results of the 2D vertical model validated and can be applied to the 2D horizontal groundwater flow simulation.  相似文献   

Onset of the summer monsoon over the southern Vietnam and its predictability   总被引：1，自引：0，他引：1  

Xuan Thanh Pham  Bernard Fontaine  Nathalie Philippon 《Theoretical and Applied Climatology》2010,99(1-2):105-113

The summer monsoon onset over southern Vietnam is determined through a new criterion based on both in situ daily rainfall at six selected stations provided by the Institute of Meteorology and Hydrology, Vietnam, and the zonal component of the wind at 1,000 hPa from the National Center for Environmental Prediction/Department of Energy Reanalysis 2. Over the period 1979–2004, the summer monsoon onset mean date is on 12 May, with a standard deviation of 11.6 days. The temporal and spatial structures of the atmospheric conditions prevailing during the onset period are detailed. Clear changes are seen in the zonal wind (strengthened over the Bay of Bengal and changed from negative to positive over South Vietnam) and in convection (deeper), in association with an intensification of the meridional gradients of sea level pressure at 1,000 hPa and of moist static energy at 2 m over Southeast Asia. The predictability of onset dates is then assessed. Cross-validated hindcasts based upon four predictors linked to robust signals in the atmospheric dynamics are then provided. They are highly significant when compared to observations (56% of common variance). Basically, late (early) onsets are preceded in March–April by higher (lower) sea level pressure over the East China Sea, stronger (weaker) southeasterly winds over southern Vietnam, decreasing (increasing) deep convection over the Bay of Bengal, and the reverse situation over Indonesia (120–140°E, 0–10°S).  相似文献   

Experimental and numerical behaviour of reinforced mortar plates subjected to accelerated corrosion     

Quang Thanh Nguyen  Sabine Caré  Yves Berthaud  Alain Millard  Frédéric Ragueneau 《国际地质力学数值与分析法杂志》2011,35(10):1141-1159

Most reinforced concrete structures are damaged due to corrosion of reinforcements in concrete. In normal conditions the pH near the reinforcements is around 12–13 which means that steel is in a passive state. But aggressive species, such as chloride ions or carbon dioxide, may penetrate into concrete and promote active corrosion. As a consequence (hydro)oxides are produced leading to degradation of concrete structures. For instance cracking of the concrete is generated due to the pressure induced by rust. In this paper, we study the inception and the propagation of cracking on reinforced mortar plates with rebars located either in the middle or at the corner. Additional experiments have been performed on cylindrical specimens to determine the local effect of rust pressure at the interface rust/mortar. The specimens have been subjected to imposed current density in order to enhance the corrosion and digital image intercorrelation has been used to determine displacement fields. The experiments have been compared to numerical modelling. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

个旧锡矿33号矿群地质特征与其外围找矿方向   总被引：1，自引：1，他引：1  

秦德先  田毓龙  朱大明  陈宗全  党玉涛  童祥  李玉新  武俊德 《矿物学报》2001,21(4):591-595

个旧锡矿区是老矿区，开采历史悠久，目前资源紧张，急需开展找矿增储研究。33号矿群是近年新勘查的矿体，以接触交代矿床为主，经工程揭露，现已探明一定锡储量，目前矿山生产急需向外围找矿，以期扩大储量，但苦于找矿工程方向不清。我们通过对隐伏花岗岩体形态，锡、铜的矿化强度模型，地表地球化学结合地质研究，指出33号矿群的北东，芦塘坝断裂与炸药库断裂交截部位附近为最有利的找矿空间。  相似文献   

GIS在中国粮食单产空间变化研究中的应用   总被引：8，自引：0，他引：8  

党安荣  阎守邕  王世新 《地理科学》1999,19(3):205-210

依据１９８５与１９９４年两个年份的分县粮食生产统计数据,运用ＧＩＳ为分析手段,从空间变化特征、变化成因及变化趋势三个方面,着重对１９８４年以来我国粮食单产的空间变化进行了定量研究。结果表明：在过去十年里,我国粮食单产增长占绝对优势,其中北方地区增产强度较大、南方地区下滑现象明显;生产条件的改善对北方粮食单产的增长有重要作用,比较利益的驱使导致南方粮食单产下滑。  相似文献   

The subsurface transport of heat and moisture and its effect on the environment: A numerical model   总被引：2，自引：0，他引：2  

Takashi Asaeda  Vu Thanh Ca 《Boundary-Layer Meteorology》1993,65(1-2):159-179

A numerical model was developed to study the transport of heat and vapor under the surface of bare soil and soil covered by some materials such as asphalt and concrete under no rainfall conditions. The computational results provide a good match with the experimental data. The results show that the transport of water vapor inside the soil has an important effect on the subsurface distribution of temperature, especially for bare soil. Because of evaporation, the temperature of bare soil is much lower than that under covered surfaces throughout the day and the temperature of the surface covered by asphalt is extremely high-higher than the atmospheric temperature even at night. An increase of thickness of the covering material further increases the temperature and heat stored under surfaces. The stored heat is released to the atmosphere at night, contributing to environmental effects such as the urban heat island.  相似文献   

五台山腹地早前寒武纪变质岩中白云母的初步研究     

党修鹏 《矿物岩石》1993,13(2):1-8

五台山早前寒武纪变质岩中的白云母属二八面体的2M型多型变体,其中五台群中的白云母为富含绿鳞石分子的普通白云母,滹沱群为多硅白云母。通过对这些白云母化学成分和b_0值测定,确定五台群变质条件属中低压相系,滹沱群属中高压相系。五台群绿片岩相的变质压力为0.3—0.5 GPa,滹沱群为0.5—0.6 GPa。基于白云母成分和b_0值的研究,对划分变质级别、变质类型;确定变质作用期次;进行地层对比和构造分析等方面是可行的。  相似文献   

柴达木盆地西部地区古近纪与新近纪沉积相   总被引：21，自引：8，他引：21       下载免费PDF全文

党玉琪  尹成明  赵东升 《古地理学报》2004,6(3):297-306

利用数十口井的电性、岩性及分析化验资料，将柴达木盆地西部地区古近纪与新近纪沉积相划分为七种相和亚相：洪积锥、水下冲积扇、河道和泛滥平原、滨湖、浅湖、较深湖和三角洲。沉积相的空间展布概括起来分为三大带：（1）阿尔金山前西段陡坡带洪积锥-水下冲积扇-扇三角洲-河道和泛滥平原-湖相 (2)阿尔金山前中段陡坡带洪积锥-水下冲积扇-湖相；（3）昆仑山前洪积锥-河道和泛滥平原-三角洲相。沉积相不仅影响着碎屑岩的成分和结构，而且也影响其物性与含油性。由洪积锥到水下冲积扇，到河道和泛滥平原，到三角洲，到湖相，石英和胶结物含量逐渐升高，岩屑和杂基含量逐渐降低，分选及磨圆变好，颗粒的粒级变细。浅层以河道和泛滥平原及三角洲相的物性最好，深层以三角洲相的物性最好，次为冲积扇，湖相最差。碎屑岩的油气富集以河道、泛滥平原和三角洲相最好，滨浅湖相油气富集最差。  相似文献