排序方式: 共有70条查询结果,搜索用时 15 毫秒
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Harold Issadore Sharlin Stephen G. Brush Harold L. Burstyn Sandra Herbert Michael S. Mahoney Nathan Sivin 《Annals of science》2013,70(1):55-70
A great deal is known about the technical issues surrounding the introduction of Hugo De Vries's mutation theory and the subsequent development of the modern genetical theory of natural selection. But so far little has been done to relate these events to the wider issues of the time. This article suggests that extra-scientific factors played a significant role, and substantiates this by comparing De Vries's respect for the original Darwinian spirit with Thomas Hunt Morgan's use of the mutation theory as part of an attack on the whole philosophy of Darwinism. In particular, it is argued that Morgan's attitude was dictated by his moral objections to the picture of a world dominated by struggle. 相似文献
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Harold J. Egoscue 《西北部美国博物学家》2011,41(3)
Three specimens of Microdipodops megacephalus nasutus were captured in the Wassuk Mountains of western Mineral County, Nevada, which provide a second place of occurrence for the subspecies and a new altitudinal record of 2455 m for the genus. This is the first time this species has been found in the pinyon-juniper belt. 相似文献
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Harold J. Egoscue 《西北部美国博物学家》2011,37(1)
The sagebrush vole flea ( Megabothris clantoni princei Hubbard) is reported from Utah for the first time, based on collections made in Tooele County. Distribution of the flea Megabothris abantis in the Bonneville Basin is limited to the Oquirrh Mountains, where its presence appears to be determined by the occurrence of the western jumping mouse. 相似文献
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A study was made of the soil mites from under different vegetative types near a coal - burning power plant in the Yampa Valley near Hayden, Colorado. The following new species of oribatids were found: Zygoribatula apletosa n.sp., Multoribates haydeni n.sp., Paraphauloppia cordylinosa n.sp., Passalozetes moniles n.sp. 相似文献
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Van Fraassen, like Popper before him, assumes that confirmation and disconfirmation relations are logical relations and thus hold only among abstract items. This raises a problem about how experience, for Popper, and observables, for van Fraassen, enter into epistemic evaluations. Each philosopher offers a drastic proposal: Popper holds that basic statements are accepted by convention; van Fraassen introduces his “pragmatic tautology.” Another alternative is to reject the claim that all evaluative relations are logical relations. Ayer proposed this option in responding to Popper, as did Sosa in a different context. I argue that this option should be pursued and propose a line of research that the option suggests. 相似文献
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Campbell PJ Yachida S Mudie LJ Stephens PJ Pleasance ED Stebbings LA Morsberger LA Latimer C McLaren S Lin ML McBride DJ Varela I Nik-Zainal SA Leroy C Jia M Menzies A Butler AP Teague JW Griffin CA Burton J Swerdlow H Quail MA Stratton MR Iacobuzio-Donahue C Futreal PA 《Nature》2010,467(7319):1109-1113
Pancreatic cancer is an aggressive malignancy with a five-year mortality of 97-98%, usually due to widespread metastatic disease. Previous studies indicate that this disease has a complex genomic landscape, with frequent copy number changes and point mutations, but genomic rearrangements have not been characterized in detail. Despite the clinical importance of metastasis, there remain fundamental questions about the clonal structures of metastatic tumours, including phylogenetic relationships among metastases, the scale of ongoing parallel evolution in metastatic and primary sites, and how the tumour disseminates. Here we harness advances in DNA sequencing to annotate genomic rearrangements in 13 patients with pancreatic cancer and explore clonal relationships among metastases. We find that pancreatic cancer acquires rearrangements indicative of telomere dysfunction and abnormal cell-cycle control, namely dysregulated G1-to-S-phase transition with intact G2-M checkpoint. These initiate amplification of cancer genes and occur predominantly in early cancer development rather than the later stages of the disease. Genomic instability frequently persists after cancer dissemination, resulting in ongoing, parallel and even convergent evolution among different metastases. We find evidence that there is genetic heterogeneity among metastasis-initiating cells, that seeding metastasis may require driver mutations beyond those required for primary tumours, and that phylogenetic trees across metastases show organ-specific branches. These data attest to the richness of genetic variation in cancer, brought about by the tandem forces of genomic instability and evolutionary selection. 相似文献
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