Patterns of Genetic Diversity and Its Loss in Mammalian Populations

Abstract:  Policy aimed at conserving biodiversity has focused on species diversity. Loss of genetic diversity, however, can affect population persistence, evolutionary potential, and individual fitness. Although mammals are a well-studied taxonomic group, a comprehensive assessment of mammalian genetic diversity based on modern molecular markers is lacking. We examined published microsatellite data from populations of 108 mammalian species to evaluate background patterns of genetic variability across taxa and body masses. We tested for loss of genetic diversity at the population level by asking whether populations that experienced demographic threats exhibited lower levels of genetic diversity. We also evaluated the effect of ascertainment bias (a reduction in variability when microsatellite primers are transferred across species) on our assessment of genetic diversity. Heterozygosity did not vary with body mass across species ranging in size from shrews to whales. Differences across taxonomic groupings were noted at the highest level, between populations of marsupial and placental mammals. We documented consistently lower heterozygosity, however, in populations that had experienced demographic threats across a wide range of mammalian species. We also documented a significant ( p = 0.01) reduction in heterozygosity as a result of ascertainment bias. Our results suggest that populations of both rare and common mammals are currently losing genetic diversity and that conservation efforts focused above the population level may fail to protect the breadth of persisting genetic diversity. Conservation policy makers may need to focus their efforts below the species level to stem further losses of genetic resources.     

活性污泥法的多变量最优控制Ⅱ.限制有机物(BOD)的排放总量

着重研究了有限制有机物排放总量时，使其运行费用最低的最优周期控制问题。通过增加新的状态变量和用补偿函数法，将本课题的有约束条件问题化为无约束条件问题，并提出了最优长参数的动态搜索法来修改传统的梯度法，从而较完善地解决了多变量最优周期控制的计算问题。     

原子吸收光谱在石化领域的应用

简述了近十几年来原子吸收光谱在我国石油化学工业领域的应用及进展，全文分原油及其加工产品，化工物品，催化剂添加剂等几类样品阐述。     

离子交换树脂吸附Cd(Ⅱ)和Pb(Ⅱ)的研究

采用静态法和动态法对阳离子交换树脂吸附Cd(Ⅱ)、Pb(Ⅱ)的行为进行了研究。考察了pH值、流速、吸附时间等条件对吸附效果的影响,优化了树脂洗脱再生的最佳条件。实验结果表明,732型强酸阳离子交换树脂能够有效地吸附废水中的Cd(Ⅱ)和Pb(Ⅱ)。对比两种交换方式,动态法具有操作简单、效率高、可连续运行等特点,具有较高的实用价值。     

GC／MS法定量测定工业废水中半挥发性有机物

采用ＧＣ／ＭＳ方法定量测定工业废水中半挥发性有机物。研究了试样预富集方法，采用不同的预富集方法，对茶，二氢苊及苯并（ａ）芘等７种物质进行富集的结果表明，采用Ｎ２吹与Ｋ－Ｄ浓缩相结合的方法，优于其他方法，其回收率与美国ＥＰＡ－６２５方法的数据相近，回收率在９２％以上，研究了定量测定条件，以２，２′－二氟联苯为内标物质，测定不同浓度的半挥发性ＥＰＡ标准样品的响应因子Ｄ≤２５％。测定了上海焦化厂工业放心     

土壤中铅的平台石墨炉原子吸收法测定

采用悬浮液进样,以平台石墨炉原子吸收法直接测定土壤中的铅。通过180目筛孔的土壤样,可均匀、稳定地悬浮于0.2％(W/V)琼脂液中。方法的相对标准偏差为1.2％～5％;回收率为93％～110％;进样10μl ,检出限为21.4pg。与火焰原子吸收法对照,两者测定结果相吻合。     

Preparation of high resolution chromosomes from amniotic fluid cells

A relatively simple method of obtaining high resolution chromosomes from amniotic fluid cells is described. The elongated chromosomes are achieved by adding ethidium bromide (5μg/ml) to the culture 4 1/2 hours before harvesting and the high resolution banding can be produced by usual banding procedures.     

土壤样品中铅和镉的微波消解法研究

利用微机控制的微波－聚四氟乙烯高压溶出装置，对土壤样品中的铅和镉两种重金属的消解进行了研究，结果表明，微波消解法具有较为满意的准确度与精密度，制样效率大大提高。     

石墨炉原子吸收光谱法测定海水中的三丁基锡

本文采用石墨炉原子吸收光谱法（ＧＦＡＡＳ）测定海水甲苯抽提液中的三丁基锡。文中考察了１４种基体改进剂对灵敏度的影响，选出了能显著提高测定灵敏度的Ｃａ－Ｃｒ基体改进剂，以０．５／０．１ｍｇ／ｍｌ的浓度比例对８个实样进行了测定，其相对标准偏差（ＲＳＤ）为３％，其特征浓度为７ｐｇ，回收率在８８％￣１０４％之间，成功地应用于近海沉积物对三丁基锡吸附规律的研究。     

Direct hydride derivatization of methyl- and ethylmercury chlorides in aqueous solution with KBH4

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