中华绒螯蟹人工育苗若干技术问题的探讨     

王波  张迎新  黄海英 《海洋科学进展》1997,(1)

本文对中华绒螯蟹亲蟹的选择、促产以及亲蟹培育、幼体培育、环境控制、饵料投喂及病害防治等技术进行了探讨．  相似文献   

青藏高原大骨节病流行区环境、食物及人群硒水平研究     

王婧  李海蓉  杨林生 《地理科学进展》2020,39(10):1677-1686

为了解青藏高原大骨节病流行区环境、食物及人群硒水平的分布现状,论文通过CNKI、Web of Science和Google Scholar等数据库检索收集了2000—2018年间发表的关于青藏高原大骨节病病区土壤、粮食、饮水及人发硒含量的文献,按拟定标准共筛选出33篇文献并提取有效数据进行统计分析。结果显示,青藏高原大骨节病病区自然环境总体仍处于低硒循环状态,其中耕作土壤、饮水平均硒含量分别为0.147 mg·kg^-1和0.54 μg·L^-1,高原自产青稞、小麦、糌粑平均含硒量分别为9.27、19.08、11.07 μg·kg^-1;而病区儿童整体硒营养水平较1990年以前有明显升高趋势,发硒平均含量为0.234 mg·kg^-1,已基本脱离硒缺乏状态(<0.20 mg·kg^-1);外源性大米的硒含量为43.29 μg·kg^-1;病区儿童发硒水平与土壤总硒含量无明显相关关系(r=0.125,P>0.05,N=23)。青藏高原大骨节病流行区儿童发硒水平与自然环境硒水平不一致的变化趋势提示,随着社会人文因素的干预,外源性硒的输入有所增加,并在一定程度上降低了病区人群对当地低硒环境的依赖性,这可能是青藏高原大骨节病病情稳定下降并得到有效控制的主要原因。  相似文献   

我国医学地理研究的主要进展和展望   总被引：11，自引：3，他引：11  

谭见安  李日邦 《地理学报》1990,45(2):186-201

简述了我国医学地理学的历史发展,60年代以来是我国医学地理发展最迅速的时期。特别在地方病、癌症等疾病的地理分布规律、地理流行特点、生态学特性、环境病因、病区环境改善和地理制图等方面取得了较显著的进展。并综合国内外的发展略述了医学地理的性质和任务。本文依医学地理的主要研究领域:疾病地理、健康地理、保健地理、医学地理制图等扼要地阐述了所获得的主要研究成果,其中有些受到国内外的广泛重视和关注。  相似文献   

Insights into the diversity,distribution and phylogeny of three ergasilid copepods (Hexanauplia: Ergasilidae) in lentic water bodies of the Morava river basin,Czech Republic     

《Limnologica》2021

Ergasilidae are a globally distributed group of copepods parasitising fish. Despite their common occurrence in European freshwaters, there is relatively little molecular data available. In this study, we recorded three ergasilid copepod species parasitising six fish species (families Cyprinidae, Percidae, Centrarchidae) in lentic water bodies along the River Morava in the Czech Republic: Ergasilus sieboldi infecting fish gills, Paraergasilus longidigitus infecting nasal cavities and Neoergasilus japonicus infecting fins. This represents a further occurrence of N. japonicus as a non-native European species, and the first report of P. longidigitusis from Central Europe waters. While strong niche selection potentially offers a free niche for each of these ergasilids in all hosts, parasite co-infections were relatively rare, with species distribution among hosts reflecting host preference. This study provides the first molecular data for E. sieboldi and P. longidigitus as native European ergasilid copepods. Phylogenetic analysis based on combined 18S and 28S rDNA showed a close relationship between P. longidigitus with other Paraergasilus species, supporting a monophyletic origin of this genus. The phylogenetic position of E. sieboldi was not clearly resolved, highlighting the need for more data and further intensive genetic investigations of other ergasilid species.  相似文献   

A stream-based Parasitic Model for implementing Mobile Digital Earth     

《International Journal of Digital Earth》2013,6(1):38-52

A Parasitic Model is proposed in this study for Digital Earth running on mobile phones through a mobile network. Because of mobile phones' limited capabilities in high-performance computing, rendering, storing, and networking (CRSN), these functions are accomplished by a superior host computer in this model. Rendered virtual scenes are compressed in a time-series as a data stream and are sent to the mobile phone through a mobile network, thus allowing Digital Earth to be operated on a mobile phone. This study examines a prototype and shows that a Mobile Digital Earth based on a Parasitic Model can achieve functionality beyond the mobile phone's actual hardware capabilities and can reduce network traffic. These results demonstrate quasi-real-time interactions, but with bandwidth increases in next-generation mobile networks such as 4G and 5G, there is potential for real-time interactions in the near future.  相似文献   

Variation in low food access areas due to data source inaccuracies     

《Applied geography (Sevenoaks, England)》2013

Several spatial measures of community food access identifying so called “food deserts” have been developed based on geospatial information and commercially-available, secondary data listings of food retail outlets. It is not known how data inaccuracies influence the designation of Census tracts as areas of low access. This study replicated the U.S. Department of Agriculture Economic Research Service (USDA ERS) food desert measure and the Centers for Disease Control and Prevention (CDC) non-healthier food retail tract measure in two secondary data sources (InfoUSA and Dun & Bradstreet) and reference data from an eight-county field census covering 169 Census tracts in South Carolina. For the USDA ERS food deserts measure accuracy statistics for secondary data sources were 94% concordance, 50–65% sensitivity, and 60–64% positive predictive value (PPV). Based on the CDC non-healthier food retail tracts both secondary data demonstrated 88–91% concordance, 80–86% sensitivity and 78–82% PPV. While inaccuracies in secondary data sources used to identify low food access areas may be acceptable for large-scale surveillance, verification with field work is advisable for local community efforts aimed at identifying and improving food access.  相似文献   

Soil geochemical parameters influencing the spatial distribution of anthrax in Northwest Minnesota,USA     

《Applied Geochemistry》2016

Bacillus anthracis is the pathogenic bacterium that causes anthrax, which dwells in soils as highly resilient endospores. B. anthracis spore viability in soil is dependent upon environmental conditions, but the soil properties necessary for spore survival are unclear. In this study we used a range of soil geochemical and physical parameters to predict the spatial distribution of B. anthracis in northwest Minnesota, where 64 cases of anthrax in livestock were reported from 2000 to 2013. Two modeling approaches at different spatial scales were used to identify the soil conditions most correlated to known anthrax cases using both statewide and locally collected soil data. Ecological niche models were constructed using the Maximum Entropy (Maxent) approach and included 11 soil parameters as environmental inputs and recorded anthrax cases as known presences. One ecological niche model used soil data and anthrax presences for the entire state while a second model used locally sampled soil data (n = 125) and a subset of anthrax presences, providing a test of spatial scale. In addition, simple logistic regression models using the localized soil data served as an independent measure of variable importance. Maxent model results indicate that at a statewide level, soil calcium and magnesium concentrations, soil pH, and sand content are the most important properties for predicting soil suitability for B. anthracis while at the local level, clay and sand content along with phosphorous and strontium concentrations are most important. These results also show that the spatial scale of analysis is important when considering soil parameters most important for B. anthracis spores. For example, at a broad scale, B. anthracis spores may require Ca-rich soils and an alkaline pH, but may also concentrate in microenvironments with high Sr concentrations. The study is also one of the first ecological niche models that demonstrates the major importance of soil texture for defining the ecological niche of B. anthracis. These results will help improve our understanding of the soil geochemical conditions most suitable for B. anthracis as well as more reliably identify areas where anthrax may be found to focus prevention and remediation efforts.  相似文献   

High-frequency parasitic modes of superconducting gravimeters     

Yuichi Imanishi 《Journal of Geodesy》2009,83(5):455-467

The superconducting gravimeter (SG) has a long-period instrumental noise called the parasitic mode at periods around 100 s, whose precise mechanism has not yet been identified. In this paper, another instrumental noise is detected at much higher frequencies by analyzing the high-rate gravity channel of two SGs in Japan. This is also a parasitic oscillation, characterized by frequencies on the order of 1 Hz and very high Q values. Detailed spectra indicate that the noise actually consists of two modes with small frequency separations. Based on a simple theory on the rotational motions of the superconducting sphere in the gravity sensor, the observed modes are tentatively identified as rotational oscillations of the sphere about two orthogonal axes in the horizontal plane. Interactions between the parasitic modes are investigated using the spectra acquired on an earthquake, to conclude that the low-frequency parasitic mode is likely to be a rotational motion of the sphere about the vertical axis.  相似文献   

对虾养殖防病新模式初步研究     

崇明  蔡生力  宋晓玲  杨丛海 《海洋科学》1995,19(2):42-47

设计了一个对虾养殖防病新模式，并进行了小规模试验，获得初步成功。在４个３０～４０ｍ＾２的露天水泥池中，各放入３ｃｍ的大苗５００～７００尾（每亩约１００００尾），经９０余天的养殖，对虾成活率８０％左右，个体１０ｃｍ，平均体重８０尾／ｋｇ，饵料系数约１．５。新模式的立足点是防病，特点是设置一蓄水沉淀池，用含氯消毒剂处理养殖用水，配备充气增氧设施，选择优质配饵，合理投喂，使各种水质理化因子及生物因子尽量  相似文献   

北黄海菲律宾蛤仔帕金虫汉行病害的研究   总被引：1，自引：0，他引：1  

梁玉波  张喜昌等 《海洋与湖沼》2001,32(5):502-511

2000年7月－11月，对我国北黄海沿岸滩涂增养殖的菲律宾蛤仔Ruditapes philippinarum大规模死亡进行了研究，并对病害暴发与温度、盐度的相关性进行了探讨。利用FTM培养和组织切片方法对病害流行海域的菲律宾蛤仔进行了检测。结果表明，蛤仔体内寄生了大量病原帕金虫Perkinsus sp，感染率为20％－100％，感染强度为3－3565936cell/ind或2－1670615cell/g组织。感染强度与蛤仔大小有关，个体越小，感染程度越轻。经感染试验，进一步确定了帕金虫大量繁殖是引起蛤仔大规模死亡的原因。病害始于7月下旬，止于10月下旬；最初暴发于庄河栗子房海域，尔后逐渐向东西两侧海域蔓延。病害暴发时要主要受温度影响，高于20℃易于暴发帕金虫病害；流行范围主要受盐度影响，盐度为20－32海域适宜帕金虫病害的流行。  相似文献