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排序方式: 共有1212条查询结果,搜索用时 359 毫秒
211.
212.
Hazel A. Jackson Lawrence Percival-Alwyn Camilla Ryan Mohammed F. Albeshr Luca Venturi Hernán E. Morales Thomas C. Mathers Jonathan Cocker Samuel A. Speak Gonzalo G. Accinelli Tom Barker Darren Heavens Faye Willman Deborah Dawson Lauren Ward Vikash Tatayah Nicholas Zuël Richard Young Lianne Concannon Harriet Whitford Bernardo Clavijo Nancy Bunbury Kevin M. Tyler Kevin Ruhomaun Molly K. Grace Michael W. Bruford Carl G. Jones Simon Tollington Diana J. Bell Jim J. Groombridge Matt Clark Cock Van Oosterhout 《Conservation biology》2022,36(4):e13918
The pink pigeon (Nesoenas mayeri) is an endemic species of Mauritius that has made a remarkable recovery after a severe population bottleneck in the 1970s to early 1990s. Prior to this bottleneck, an ex situ population was established from which captive-bred individuals were released into free-living subpopulations to increase population size and genetic variation. This conservation rescue led to rapid population recovery to 400–480 individuals, and the species was twice downlisted on the International Union for the Conservation of Nature (IUCN) Red List. We analyzed the impacts of the bottleneck and genetic rescue on neutral genetic variation during and after population recovery (1993–2008) with restriction site-associated sequencing, microsatellite analyses, and quantitative genetic analysis of studbook data of 1112 birds from zoos in Europe and the United States. We used computer simulations to study the predicted changes in genetic variation and population viability from the past into the future. Genetic variation declined rapidly, despite the population rebound, and the effective population size was approximately an order of magnitude smaller than census size. The species carried a high genetic load of circa 15 lethal equivalents for longevity. Our computer simulations predicted continued inbreeding will likely result in increased expression of deleterious mutations (i.e., a high realized load) and severe inbreeding depression. Without continued conservation actions, it is likely that the pink pigeon will go extinct in the wild within 100 years. Conservation rescue of the pink pigeon has been instrumental in the recovery of the free-living population. However, further genetic rescue with captive-bred birds from zoos is required to recover lost variation, reduce expression of harmful deleterious variation, and prevent extinction. The use of genomics and modeling data can inform IUCN assessments of the viability and extinction risk of species, and it helps in assessments of the conservation dependency of populations. 相似文献
213.
为解决煤矿瓦斯有效抽采半径难以快速准确确定的问题,采用基于Adam算法优化DNN(深度神经网络)方法来预测瓦斯抽采半径。查阅文献共收集已得到验证的970组数据集,每组数据选取煤层瓦斯初始渗透率、钻孔直径、抽采时间、地应力、煤层初始瓦斯压力作为预测模型的5个特征量,有效抽采半径作为目标输出值。接着预测模型进行不断学习和训练,最终训练得到1个最优的瓦斯有效抽采半径预测模型。利用训练好的最优预测模型结合Python语言开发出计算有效抽采半径的软件,并使用该软件在四季春煤矿和鹤煤六矿进行有效抽采半径预测的工程实例研究,验证该软件预测抽采半径的实用性和准确性。研究结果表明:通过使用开发的软件,可快速且较准确地计算出矿井瓦斯有效抽采半径,可为暂不具备现场测试条件的矿井抽采设计提供一定的参考依据。 相似文献
214.
松毛虫遗传多样性研究中AFLP反应体系的建立 总被引:1,自引:0,他引:1
以油松毛虫为材料,对T4 DNA连接酶不同用量、预扩增中的Mg~(2+)浓度、dNTP浓度、引物浓度以及选择性扩增巾的预扩增产物稀释倍数、Mg2~(2+) 浓度、dNTP浓度、引物浓度和Taq酶浓度进行了比较分析.最终建立了适合松毛虫的AFLP反应体系.用优化的AFLP反应体系,以油松毛虫、赤松毛虫和马尾松毛虫为材料筛选引物,从81对引物组合中筛选出10对多态性高的引物组合.图9参17 相似文献
215.
岳克东 《中国环境管理干部学院学报》2001,(Z1)
密码技术是实现网络安全的关键技术之一,本文首先介绍密码技术的基本概念,然后着重讨论建立密码防护体系的基本思想和密码防护体系,加密算法,并详细探讨了密钥的管理方法和密码技术的应用。 相似文献
216.
Assessment of GM Crops in Commercial Agriculture 总被引:1,自引:0,他引:1
The caliber of recent discourse regarding geneticallymodified organisms (GMOs) has suffered from a lack of consensuson terminology, from the scarcity of evidence upon which toassess risk to health and to the environment, and from valuedifferences between proponents and opponents of GMOs. Towardsaddressing these issues, we present the thesis that GM should bedefined as the forcible insertion of DNA into a host genome,irrespective of the source of the DNA, and exclusive ofconventional or mutation breeding.Some defenders of the commercial use of GMOs have referred to thescientific work of GMO critics as ``junk science.' Such a claim isfalse and misleading, given that many papers critical of both theutility and safety of GMOs have been published in peer reviewedjournals by respected scientists. In contrast, there is a dearthof peer reviewed work to substantiate the frequently heardassertions of either safety or utility in GMOs. The polarity,which now characterizes much of the public discourse on GMOs,reflects not simply scientific disagreement, but alsodisagreement in underlying value assumptions. Value differencesstrongly affect the assessment of both benefit and harm fromGMOs.The concept of substantial equivalence occupies a pivotalposition in the GMO risk assessment process that is used in bothCanada and the US. A GMO judged to be substantially equivalent toa conventional product – as have all submissions to date – ispresumed to be safe enough for commercialization. The conclusionof safety – from both human health and environmental perspectives– should be based on scientific evidence, corroborated by actualexperimentation. However, regulators infer safety largely fromassumptions-based reasoning, with little or no experimentalvalidation. The judgement of safety because of substantialequivalence is a dubious argument by analogy. 相似文献
217.
Wei‐Han Liu Miguel A. Medina Wayne Thomann Warren T. Piver Timothy L. Jacobs 《Journal of the American Water Resources Association》2000,36(6):1335-1348
ABSTRACT: Using a genetic algorithm (GA), optimal intermittent pumping schedules were established to simulate pump‐and‐treat remediation of a contaminated aquifer with known hydraulic limitations and a water miscible contaminant, located within the Duke Forest in Durham, North Carolina. The objectives of the optimization model were to minimize total costs, minimize health risks, and maximize the amount of contaminant removed from the aquifer. Stochastic ground water and contaminant transport models were required to provide estimates of contaminant concentrations at pumping wells. Optimization model simulations defined a tradeoff curve between the pumping cost and the amount of contaminant extracted from the aquifer. For this specific aquifer/miscible contaminant combination, the model simulations indicated that pump‐and‐treat remediation using intermittent pumping schedules for each pumping well produced significant reductions in predicted contaminant concentrations and associated health risks at a reasonable cost, after a remediation time of two years. 相似文献
218.
Philipp Balzer Klaus Peter Rippe Peter Schaber 《Journal of Agricultural and Environmental Ethics》2000,13(1-2):7-27
The 1992 incorporation of an article by referendum in the Swiss Constitution mandating that the federal government issue regulations
on the use of genetic material that take into account the dignity of nonhuman organism raises philosophical questions about
how we should understand what is meant by “the dignity of nonhuman animals,” and about what sort of moral demands arise from
recognizing this dignity with respect to their genetic engineering. The first step in determining what is meant is to clarify
the difference between dignity when applied to humans and when applied to nonhumans. Several conceptions of human dignity
should be rejected in favor of a fourth conception: the right not to be degraded. This right implies that those who have it
have the cognitive capacities that are prerequisite for self-respect. In the case of nonhuman organisms that lack this capacity,
respecting their dignity requires the recognition that their inherent value, which is tied to their abilities to pursue their
own good, be respected. This value is not absolute, as it is in the case of humans, so it does not prohibit breeding manipulations
that make organisms more useful to humans. But it does restrict morally how sentient animals can be used. In regard to genetic
engineering, this conception requires that animals be allowed the uninhibited development of species specific functions, a
position shared by Holland and Attfield, as opposed to the Original Purpose conception proposed by Fox and the Integrity of
the Genetic Make-up position proposed by Rolston. The inherent value conception of dignity, as here defended, is what is meant
in the Swiss Constitution article.
This paper is a slightly revised version of a paper that had been published in German in 1998 (“Menschenwürde vs. Würde der
Kreatur,” Freiburg i.Br.). 相似文献
219.
Christian J. Peters 《Journal of Agricultural and Environmental Ethics》2000,13(3-4):313-327
The use of genetic engineering inagriculture has been the source of much debate. Todate, arguments have focused most strongly on thepotential human health risks, the flow of geneticmaterial to related species, and ecologicalconsequences. Little attention appears to have beengiven to a more fundamental concern, namely, who willbe the beneficiaries of this technology? Given the prevalence of chronic hunger and thestark economics of farming, it is arguable thatfarmers and the hungry should be the mainbeneficiaries of agricultural research. However, theapplication of genetic engineering appears unlikely tobenefit either of these two groups. This technology islargely controlled by the private sector, and itscontinued development hinges on its profitability.Thus, the only likely beneficiaries of the applicationof genetic engineering in agriculture are companieswith the capacity to use it. 相似文献
220.