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161.

Background  

Although capable to evolve, viruses are generally considered non-living entities because they are acellular and devoid of metabolism. However, the recent publication of the genome sequence of the Mimivirus, a giant virus that parasitises amoebas, strengthened the idea that viruses should be included in the tree of life. In fact, the first phylogenetic analyses of a few Mimivirus genes that are also present in cellular lineages suggested that it could define an independent branch in the tree of life in addition to the three domains, Bacteria, Archaea and Eucarya.  相似文献   
162.

Background  

Overlapped genes originate by a) loss of a stop codon among contiguous genes coded in different frames; b) shift to an upstream initiation codon of one of the contiguous genes; or c) by overprinting, whereby a novel open reading frame originates through point mutation inside an existing gene. Although overlapped genes are common in viruses, it is not clear whether overprinting has led to new genes in prokaryotes.  相似文献   
163.
Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes. Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen pollution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NOx emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen. Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.  相似文献   
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The new EU-regulations on organic farming (1804/1999) are also influencing the animal welfare. A lot of positive regulations is to find, but also regulations that seen to mind more about the general public and customer and their view on organic farming, than the health and welfare of the animals.The paper specially focus on the impact of the regulations and the recommendations that phytotherapeutic essences and homeopathic products take precedence over the so called chemically-synthesised allopatic veterinary medical products, and that the use of the same is prohibited for preventive treatments. Key questions here are the lack of scientific evidence concerning homeopathy in animals, and that Swedish veterinarians are not allowed to work with homeopathy.Differences in interpretation of the regulations between animal owners and veterinarians will also be discussed. What is a disease that needs treatment? Who is to decide about the treatment? Parasitic infections are discussed as an illustrative example.Other consequences of the regulations concerning the animal welfare are problems in certain geographical zones, for instance subarctic areas where necessary crops are impossible to grow.Animal transports and splitting mother-offspring are briefly discussed as future problems to be handled in the regulations, and the paper ends by presenting the need of regulated herd health control programs in organic husbandry, which can detect and focus on welfare and production problems. The organic movement is not static, and must not be so.  相似文献   
166.
Medication is an important focus area in organic animal husbandry. The combination of goals relating to improved animal welfare and reduced use of chemicals in general creates a common wish to reduce medication. Based on data from current Danish research projects in organic dairy farming, one specific organic medication pattern or policy cannot be described. The disease treatment pattern is influenced by many factors, e.g. the interaction with colleagues, veterinarians and agricultural advisors. No significant difference could be found with regard to incidence of mastitis treatments or somatic cell counts in 27 organic and 57 conventional herds. A marked tendency to shorter treatment periods in relation to mastitis treatments was described for organic farms in comparison with conventional farms (1.9 days versus 3.2 days (5 organic and 7 conventional herds)). In a study of development of health advisory service in organic herds, the dialogue between farmer, veterinarian and agricultural cattle advisor changed the treatment pattern markedly during a period of 6 months. Among important future challenges for veterinarians in organic farming is pointed at the constructive, open, and critical interaction with the single organic farmer as well as the organic animal husbandry system in general.  相似文献   
167.
THE interaction between the cell surface and the substratum is very important in determining several characteristics of cells growing in tissue culture. Transformed cells are less adherent to the substratum than untransformed cells1 and this reduced interaction with the substratum may be responsible for abnormal properties such as the loss of contact or density dependent inhibition of growth2 and the ability to form colonies in agar and to grow in suspension culture.  相似文献   
168.
For most of the twentieth century the state was not a major part of the anthropological toolkit. Despite significant archaeologically driven work on evolution and state formation, most socio-cultural anthropologists have viewed the state with empiricist scepticism, populist hostility, or ethnographic indifference. Typically, state-theory has been left to other disciplines, such as political science and sociology. Since the end of the cold war there has been a greatly increased interest in the state among anthropologists. Philip Abrams, Michael Herzfeld, and Akhil Gupta, who coined the phrase “ethnography of the state”, have been particularly important to this development. However, there remains no serious engagement with the body of state-theory generated, over the last century, by political activists, scientists, sociologists, and anthropologists. It will be argued that this has allowed for the growth of an unproblematised orthodoxy around an ethnographically informed variant of classic American pluralist state-theory. This orthodoxy has hobbled the understanding and explanation of complex political phenomena, led to confusion between hypotheses and conclusions, and tied parts of the discipline to a partisan political project that remains largely un-interrogated. This essay seeks to provide context and clarification on state-theory as a step towards discussion of anthropology’s contemporary engagement with the state and broader questions of political action and social change.  相似文献   
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