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排序方式: 共有119条查询结果,搜索用时 31 毫秒
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Annick Vuissoz Michael Worobey Nancy Odegaard Michael Bunce Carlos A. Machado Niels Lynnerup Elizabeth E. Peacock M. Thomas P. Gilbert 《Journal of archaeological science》2007
We have investigated the survival of PCR-amplifiable mitochondrial and nuclear DNA in a small number of modern and medieval bovine leather samples. The results of this preliminary investigation demonstrate that, while no nuclear DNA can be PCR-amplified from any of the specimens, mitochondrial DNA can be amplified from all samples. To investigate this contrasting pattern of DNA survival further, we have vegetable-tanned cow skin in our own laboratory, and directly assayed the survival of PCR-amplifiable mitochondrial and nuclear DNA at each step of the process. The results indicate that nuclear DNA is reduced to sub-amplifiable levels as a result of the tanning baths, whereas amplifiable mitochondrial DNA survives the complete process. Our results suggest that old and archaeological bovine leather may represent a useful source of genetic information, although this information will most likely be limited to that which can be gained from mitochondrial DNA. 相似文献
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Under the leadership of Matteo Salvini, the Lega Nord has shifted away from its previous political identity as a voice for Italy’s north and has placed hostility towards the policies and institutions of the European Union (EU) at the heart of its rhetoric. Nowadays, the enemy is Rome no longer: it is Brussels, European institutions, and the threat to the national sovereignty posed by the EU. Borrowing from the Italian political philosopher Nicola Matteucci, we would describe Salvini’s Lega as a ‘populist insurgency’. That is to say, it is a populist party that marries the traditional populist evocation of the virtues of the people against the corrupt elites, with a pervasive glibness of analysis. 相似文献
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Gilbert J. Price Michael J. Tyler Bernard N. Cooke 《Alcheringa: An Australasian Journal of Paleontology》2013,37(1):171-182
Systematic collecting from fluvial late Pleistocene deposits from the Darling Downs, southeast Queensland, Australia, has led to the recovery of the first fossil frogs from the region, ail from the Myobatrachidae, a family of ground dwelling and burrowing frogs. The most common species recovered, Limnodynastes tasmaniensis, is extant on the Darling Downs. The fossil taxa include species whose extant populations inhabit arid zones(Limnodynastes sp. cf. L. spenceri), montane forests (Kyarranus spp.), and open woodlands (Neobatrachus sudelli), and indicate the existence of a mosaic of habitats during the Pleistocene. The absence of the Hylidae (tree frogs), a family common throughout the Darling Downs today, may be explained by a taphonomic bias that favours non-arboreal forms. Alternatively, hylids may have been rare or absent on the Darling Downs during the Pleistocene. 相似文献
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The provision of adequate primary health care in developing countries is often troublesome. The problem is to provide a sufficient number of facilities to be geographically accessible, yet few enough to be properly stocked and staffed. In many less developed countries accessibility problems are exacerbated by extensive rainy seasons in which travel is only possible on paved roads. Using the covering tour model we investigate the use of mobile facilities to resolve this dilemma in Suhum District, Ghana. The model minimizes a mobile facility's travel while serving all population centers within range of a feasible stop. Computational results show that in the rainy season the model cannot provide full coverage; over six percent of the population is beyond a covering distance of eight kilometers. In the dry season, 99 percent of the population can be served by a tour at a covering distance of seven kilometers.Beyond a distance of four kilometers, the dry season problem becomes a trade-off between the distance traveled by healthcare patrons and mobile facilities. These results illustrate the importance of flexibility of mobile systems: if accessibility cannot be provided in all seasons it may still be provided at favorable times of the year. 相似文献