Sequential establishment of stripe patterns in an expanding cell population

Periodic stripe patterns are ubiquitous in living organisms, yet the underlying developmental processes are complex and difficult to disentangle. We describe a synthetic genetic circuit that couples cell density and motility. This system enabled programmed Escherichia coli cells to form periodic stripes of high and low cell densities sequentially and autonomously. Theoretical and experimental analyses reveal that the spatial structure arises from a recurrent aggregation process at the front of the continuously expanding cell population. The number of stripes formed could be tuned by modulating the basal expression of a single gene. The results establish motility control as a simple route to establishing recurrent structures without requiring an extrinsic pacemaker.     

Social-ethical issues concerning the control strategy of animal diseases in the European Union: A survey

In 2004 a survey was conducted in the member states of the European Union designed to gain greater insight into the views on control strategies for foot and mouth disease, classical swine fever, and avian influenza with respect to the epidemiological, economic and social-ethical consequences of each of these animal diseases. This article presents the results of the social-ethical survey. A selection of stakeholders from each member state was asked to prioritize issues for the prevention and control of these diseases. A majority of stakeholders chose preventive measures as the preferred issue. An analysis was done to determine whether there were differences in views expressed by stakeholders from member states with a history of recent epidemics and ones without such a history, and whether there were regional differences. There were no differences between member states with or without a history of recent epidemics. There were indeed regional differences between the priority orders from Northern and Southern Europe on the one hand, and from Eastern Europe on the other. Nina E. Cohen is a biologist and is a researcher at the Wageningen University. She is specialized in societal and ethical issues in human–animal relationships. Her current research is focused on the social-ethical issues concerning the prevention and control of foot and mouth disease, classical swine fever and avian influenza. Marcel A.P.M. van Asseldonk has studied animal science. Currently he works at the Institute for Risk Management in Agriculture (IRMA) of the Wageningen University. He is specialized in the design and pricing of insurance policies and animal health funds for the main livestock epidemics. Elsbeth N. Stassen is a veterinarian and professor of Animals and Society at the Wageningen University. Elsbeth Stassen is specialized in animal health, animal welfare and human–animal relationships. She was a member of a governmental welfare committee during the avian influenza epidemic in the Netherlands in 2003.     

相关序列扩增多态性(SRAP)一种新的分子标记技术

SRAP是一种新的DNA分子标记,具有简便、稳定、中等产率和容易得到选择条带序列的特点。SRAP是一种基于PCR技术的新的分子标记技术,其利用独特的引物设计对ORFs进行扩增,上游引物长17bp,对外显子进行特异扩增,下游引物长18bp,对内含子区域、启动子区域进行特异扩增,因个体不同以及物种的内含子、启动子与间隔长度不等而产生多态性。扩增产物用变性的聚丙烯酰胺凝胶分离,然后用放射自显影检测。本文在阐述SRAP的原理和流程后,详细论述了SRAP标记目前在植物遗传图谱构建、遗传多样性、基因定位、比较基因组学、杂种优势预测等方面的研究进展及应用前景。     

农业水费调整对农业节水的影响

针对我国农业节水与农业水费的现状 ,分析了二者之间的关系。从理论上阐述了调整农业水费对促进我国农业节水事业进一步发展的重要作用 ,并利用水利经济原理推算出有利于农业节水发展的节水水价。     

景观破碎带GPSRTK监测理论、技术方法及空间模型

由于自然或人为作用形成的景观破碎带不仅影响景观的观赏价值 ,还会引起水土流失和破坏生物多样性 .因此 ,对城乡景观破碎带的定量监测不仅有学术意义 ,更有应用价值 .该项目通过对各类景观破碎带的GPSRTK技术定量监测建立各类景观破碎带的空间分布数学模型 ,并精确监测其地图 (投影 )面积、临空面积、土方体积及其变动 ,为治理景观破碎带提供基础信息 .     

The political ecology of dietary transitions: Changing production and consumption patterns in the Kolli Hills,India

Using a case study from the Kolli Hills, India, I suggest that political ecology provides a useful theoretical basis for considering localized dietary transitions in rural, agricultural communities in developing countries. By examining the reasons for the near-disappearance of local minor millets as staple foods in three small-farmer communities, I argue that an explicit, actor-oriented analysis allows for an integration of food issues with considerations of environmental circumstances, local aspirations, and labor concerns. That is, an agricultural shift that abandons minor millets as a food resource reflects environmental changes and household economic aspirations. Such an analysis has implications for the creation of practical food security projects through the recognition and incorporation of small-farmer experiences, voices, and priorities. This research was undertaken through ethnographic fieldwork, using semi-structured interviews and participant observation as the primary methods. Elizabeth Finnis obtained her PhD from McMaster University in Canada and is currently a post-doctoral fellow in the Department of Anthropology and the Centre for Society, Technology, and Development at McGill University.     

Explaining disparities in food safety compliance by food stores: does community matter?

This paper provides a conceptual framework to explain why disparities may exist in food safety code compliance by food stores in different neighborhoods. Explanations include market dynamics, community characteristics, retailer attributes, inspector characteristics, and enforcement approaches, and interactions among the factors. A preliminary and limited empirical test of some of these relationships in Detroit, Michigan shows a higher rate of food safety violations by stores in poorer neighborhoods and in neighborhoods with higher concentrations of African-American residents. Stores inspected by female inspectors also scored higher numbers of critical violations, suggesting a need for greater examination of the social relations associated with enforcement interactions in food safety studies.

Livelihood change,farming, and managing flood risk in the Lerma Valley,Mexico

In face of rising flood losses globally, the approach of “living with floods,” rather than relying on structural measures for flood control and prevention, is acquiring greater resonance in diverse socioeconomic contexts. In the Lerma Valley in the state of Mexico, rapid industrialization, population growth, and the declining value of agricultural products are driving livelihood and land use change, exposing increasing numbers of people to flooding. However, data collected in two case studies of farm communities affected by flooding in 2003 illustrate that the concept of flood as agricultural “hazard” has been relatively recently constructed through public intervention in river management and disaster compensation. While farming still represents subsistence value to rural households, increasingly rural communities are relying on non-farm income and alternative livelihood strategies. In this context, defining flooding in rural areas as a private hazard for which individuals are entitled to public protection may be counterproductive. A different approach, in which farmers’ long acceptance of periodic flooding is combined with valuing agricultural land for ecoservices, may enable a more sustainable future for the region’s population.