华南玄武岩红土化过程中微量元素地球化学

广东、海南的玄武岩．在强烈的红土化过程中．元素在红土剖面中发生迁移和残留、贫化和富集。根据红土化过程中元素的地球化学性状，将元素划分为活泼元素和不活泼元素两大类。并首次采用了元素它集因子这个概念来探讨红土化过程中微量元素的地球化学行为。最后讨论了红土化过程小金的表生富集作用。     

First-trimester diagnosis of an unusual case of α-mannosidosis

Chorionic villi obtained in the first trimester from a pregnancy at risk for α-mannosidosis were shown to have reduced α-mannosidase (EC 3.2.1.24) activity. The pregnancy was terminated and subsequent enzyme studies of the fetal tissues were consistent with the diagnosis of α-mannosidosis. Like the enzyme in the child's fibroblast, α-mannosidase of the chorionic villi from a pregnancy at risk for α-mannosidosis was activated by high substrate concentration and by Zn^{2 +}, and displayed a K_m value two-fold higher than normal. Our results confirm that chorionic villi can be used for early prenatal diagnosis of α-mannosidosis.     

Biological and economic optima in a tropical grazing ecosystem in Australia

Our aim in this study was to identify the economically optimal level of use of resources for a grazing system in tropical Australia and to compare it with the biological optimum. Grazing management trials were conducted in the Ord River irrigation area of north-western Australia. Biologists at the Commonwealth Scientific and Industrial Research Organization provided the biological data. The liveweight gains of Kimberley shorthorn steers were recorded, after a 1-year fattening period, for different grazing management strategies. Five different stocking rates were used on irrigated pangola grass (Digitaria decumbens) fertilized with nitrogen at five different rates. All other were applied at fixed, non-limiting levels.The results of the trials were modelled by a liveweight gain production function. This production function was used in an income simulation model to identify economically optimal (profit maximizing) stocking rates. This was done in two stages. First, a base analysis was undertaken on the basis o the economic conditions prevailing in September 1987. Second, sensitivity analysis was applied to the results of the base analysis. The parameters varied were the rate of interest, store cattle prices, finished cattle prices, transport costs and the length of the planning horizon.The biological optimum, when defined as maximum liveweight gain ha⁻¹, corresponds to a much higher intensity of use of resources than the economic optimum, and yields substantially lower profits or higher losses. These discrepancies increase when economic conditions worsen, or when the planning horizon of graziers is decreased from 50 to 10 years. Therefore, the adoption of the biological optimum cannot result in an econonomically stable grazing system in the medium to long term, when it is highly likely that economic parameters will fluctuate. The economic stability of the system is increased, but is still quite weak, if the economically optimal input combination is utilized. It was not possible to determine whether this economic optimum would result in long-term ecological stability because the relevant data were not collected during the trials.The relevance of management recommendations made to graziers and land administrators would be increased if these recommendations were based on an analysis of both the economic and the ecological stability of grazing systems over the medium to long term. We show in the last part of this study how this could be accomplished.     

Prenatal diagnosis of cystinosis utilizing chorionic villus sampling

The prenatal diagnosis of cystinosis is currently based on the increased amount of free-cystine present in amniotic fluid cells. Amniocyte cultures must be grown for at least 2 weeks to obtain sufficient cells for such measurements. Thus, the diagnosis cannot be made until close to 20 weeks gestational age by this method. We report a case in which chorionic villi were used for direct cystine measurement resulting in the in utero diagnosis of cystinosis at 9 weeks gestational age. The diagnosis was confirmed by the study of cultured chorionic villus cells, and of the 10-week abortus.     

Molecular cytogenetic characterization of marker chromosomes found at prenatal diagnosis

The nature and origin of two de novo small marker chromosomes found at prenatal diagnosis were determined by fluorescence in situ hybridization using chromosome centromere-specific probes and chromosome-specific plasmid libraries. One marker was found in a mosaic state and was shown to be an i(18p). The second marker was characterized as an inv dup(22). We conclude that molecular cytogenetic analysis contributes to the identification of marker chromosomes and therefore facilitates genetic counselling and decision-making for the parents.     

浅谈推行清洁生产的必要性及技术方法

清洁生产是世界各国推进可持续发展所采用的一项基本策略，是《中国21世纪议程》提出的工业、交通、能源等实现可持续发展的核心战略措施。本文简要论述了清洁生产的内涵、大力推行清洁生产的必要性、实现清洁生产的技术方法。     

在污染条件下生物的生态效应

主要就污染物对动物、植物及人体健康的危害，以及在污染条件下生物的适应与进化作一综述。     

长江中下游海相三叠系膏盐层与铜(金)、铁矿床

长江中下游海相三叠系膏盖层中含有很大比例的大、中型铜（金）、铁、多金属矿床。膏盐层不仅是铜（金）、铁矿床的主要赋矿层位之一，而且是部分成矿金属的矿源层；膏盐层还为燕山期岩浆提供部分钠质、钾质及挥发组分，影响岩浆演化的方向，改变了含矿流体的性质；另外，从岩体和矿床中金属硫化物中流同位素重硫成分的增高，说明在成者、成矿过程中，膏盐层是硫的供应者之一。因此膏盐层与铜（金）、铁、多金属矿床之间存在着特殊的成因联系。     

排污许可证交易的理论与实践

排污许可证交易是市场经济体制下控制污染的有效措施。本文对排污许可证交易的基本理论、排污许可证交易的优点、排污许可证交易的可行性、排污许可证的交易方式、排污许可证的交易程序、初始排污权分配、交易资金的使用等问题进行了探讨。     

Predator odour and its impact on male fertility and reproduction in Phodopus campbelli hamsters

 This study investigated the influence of cat urine odour in suppressing development and fertility in Campbell's hamster males. Exposure to this odour from postnatal day 11 until day 45 (sexual maturation) resulted in reduced sex organ weights, reduced testosterone levels and in an increase in abnormalities of the synaptonemal complex in both sex chromosomes and autosomes. Subsequent breeding experiments revealed a significant decrease in litter size. All these data indicate a severe effect of predator odour on the breeding success of potential prey species. It is assumed that these effects are caused by the sulphurous compounds in the urine; however, the underlying mechanisms are not yet known. Received: 31 January 2000 / Accepted in revised form: 6 June 2000