Lake Mahega: a mesothermic, sulphato-chloride lake in western Uganda

In May, 1971, Lake Mahega had pronounced mesothermy (40.W C at one metre). Solar heating of a bloom of baeteria and the blue-green alga, Synechococcus bacillaris Butch., probably caused the high temperature. A total ionic concentration gradient increasing from 192,600 mg 1itre-1 at the surface to 415,200 mg•litre- 1 at three metres stabilized the thermally inverted water. Nearly equal amounts of chloride and sulphate accounted for about 90% of the anionic composition. Sodium was the major cation. Crystals or the triple salt, northupite (Na2 CO3. MgCO3. NaCl) and of thenardite (Na2SO4) were mixed with the surface sediment. We believe it is possible that primary northupite depnsition is occurring. Lake Mahega is also the first mesothermic, sulphato-chloride lake reported for East Africa.

On the ecology and explorations of the fisheries of an East African rift valley lake, Part 1: On the bionomics and population structure of Tilapia nilotica Linnaeus 1757 in Lake Baringo, Kenya

An ecological survey of the fisheries of Lake Baringo, Kenya was carried out between August, 1972 and August, 1973. The bionomics and population structure of T. nilotica is described. Sampling was done with multifilament gillnets of graded mesh sizes from 51 mm to 178 mm in approximately 12.5 mm increments. The Lake was divided into three sampling and ecologically different zones - the south, central and north zones. The size range of T. nilotica of both sexes caught was between 5 and 27 cm (mode 16 cm) with a mean length of 16.07 cm. For all the collections, males dominated (55.3%) and a higher proportion of males were caught in January, August and November. The smallest mature male and female was 9 and 10 cm respectively. Males grow faster and mature at larger sizes than females. 50% of all males and females mature at 17.4 and 16:4 cm respectively. The periods of intense spawning were between August and October and January to April. The Tilapia were feeding best in central and north zones and the feeding intensity was reduced in January. Two endoparasites Contracaecum sp. and Clinostomum sp. were isolated from the Tilapia. The "condition" of the fish was better in the north than in the other two zones.

中国角蟾亚科十一种的同工酶电泳研究(英文)

本文用同工酶电泳的方法分析了中国产角蟾亚科3属11种,共13个地理种群样本,以探讨它们的遗传多样性及系统关系。用于分析的酶共14种,由24个基因位点编码。经过酶带的分析和计算,得出了每个种群样本在每个基因位点上的等位基因频率（见表3）。根据基因频率的分布,计算得出了各种群样本的基因多样性指数——平均杂合率（H）（见表4）,结果表明,角蟾亚科的H值平均值为0.18, 在两栖动物中是属于很高的遗传多样性水平,根据基因频率的分布,计算了所有种群样本间的Nei’s遗传距（见表5）,并通过类平均法（UPGMA）重建了进化树（dendrogram）。分析结果支持将拟角蟾属（Ophryophryne）从角蟾属（Megophrys）中分出为独立属的观点;但是对短腿蟾属（Brachytarsophrys）是否为独立属提出了疑问。在角蟾属（Mesophrys）中,可以明显地看出3个组,它们中的种间亲缘关系比较近,这3个组分别是:①白颌大角蟾（M.lateralis）、大花角蟾（M.giganticus）和长肢角蟾（M.longipes）;②粗皮角蟾（M.palpebralespinneosa）、淡肩角蟾（M.boettgeri）...

艾滋病的传播与生殖道局部免疫

艾滋病的传播与生殖道局部免疫贲昆龙（中国科学院昆明动物研究所，昆明６５０２２３）引起人类艾滋病的人类免疫缺陷病毒（ＨＩＶ）可通过性交、血液、母婴和哺乳等方式传播，性交是主要的传播途径。据推测，全世界已感染ＨＩＶ的１，０００多万成年人当中，７５％是通过...

云南兔(Lepus comus)的染色体研究

用染色体分带技术分析表明云南兔2n=48, 常染色体中有6对中着丝点染色体、5对亚中着丝 点染色体、10对亚端着丝粒染色体和2对端着丝粒染色体。x染色体为一较大的亚中着丝粒染色体。c-带核型中, Nos.9,14,16,20染色体着丝粒c-带呈阴性, 而13,15,18呈很弱的阳性 。图版1表2参22(邓琳珠)

Reinforcement learning for parameter estimation in statistical spoken dialogue systems

Reinforcement techniques have been successfully used to maximise the expected cumulative reward of statistical dialogue systems. Typically, reinforcement learning is used to estimate the parameters of a dialogue policy which selects the system's responses based on the inferred dialogue state. However, the inference of the dialogue state itself depends on a dialogue model which describes the expected behaviour of a user when interacting with the system. Ideally the parameters of this dialogue model should be also optimised to maximise the expected cumulative reward. This article presents two novel reinforcement algorithms for learning the parameters of a dialogue model. First, the Natural Belief Critic algorithm is designed to optimise the model parameters while the policy is kept fixed. This algorithm is suitable, for example, in systems using a handcrafted policy, perhaps prescribed by other design considerations. Second, the Natural Actor and Belief Critic algorithm jointly optimises both the model and the policy parameters. The algorithms are evaluated on a statistical dialogue system modelled as a Partially Observable Markov Decision Process in a tourist information domain. The evaluation is performed with a user simulator and with real users. The experiments indicate that model parameters estimated to maximise the expected reward function provide improved performance compared to the baseline handcrafted parameters. © 2011 Elsevier Ltd. All rights reserved.

温度对烟蚜茧蜂发育、生殖的影响

烟蚜茧蜂发育速率与温度的关系符合逻辑斯蒂曲线,即25℃从卵至羽化所需历期最短(10.67d),30℃发育历期稍有延长(11.6d)。卵至羽化的发育起点温度为3.3℃,有效积温为266.0日度。烟蚜茧蜂雌蜂羽化当天即可产卵,在产卵期的前4天产出总卵量的90%(15-30℃);在6:30-22:30产出总卵量的80%。温度>25℃对烟蚜茧蜂雌蜂的寿命、生殖力,以及对僵蚜体重和羽化率均造成显著的负影响。烟蚜茧蜂雌蜂的寿命、性比、生殖力及僵蚜的体重和羽化率均在20℃时达最佳,结合发育历期的结果,认为该蜂大规模人工繁殖和释放的最佳温度范围是20-25℃。就研究结果在生物防治中的应用也进行了讨论。

Sleeping sites of black-and-white snub-nosed monkeys (Rhinopithecus bieti) at Baima Snow Mountain, China

Data on sleeping sites of a group of black-and-white snub-nosed monkeys Rhinopithecus bieti (Colobinae, Primates) were collected between April-July and September-December 2001 to try to determine the factors affecting site selection at Nanren (99 degrees