Bayesian testing for trend in a power model for clustered binary data

Developmental toxicity studies are widely used to investigate the potential risk of environmental hazards. In dose–response experiments, subjects are randomly allocated to groups receiving various dose levels. Tests for trend are then often applied to assess possible dose effects. Recent techniques for risk assessment in this area are based on fitting dose–response models. The complexity of such studies implies a number of non-trivial challenges for model development and the construction of dose-related trend tests, including the hierarchical structure of the data, litter effects inducing extra variation, the functional form of the dose–response curve, the adverse event at dam or at fetus level, the inference paradigm, etc. The purpose of this paper is to propose a Bayesian trend test based on a non-linear power model for the dose effect and using an appropriate model for clustered binary data. Our work is motivated by the analysis of developmental toxicity studies, in which the offspring of exposed and control rodents are examined for defects. Simulations show the performance of the method over a number of samples generated under typical experimental conditions.     

Sex ratio adjustment and maternal condition in two aphid species

We analyzed how offspring sex ratio varies with maternal condition in order to obtain evidence on the population structure in two aphid species with different life cycles. When fitness returns per unit investment differ for the production of daughters and sons, selection will favor an increasing investment into the sex with the higher returns. Therefore, the offspring sex ratios of individual mothers should become more biased towards the sex with the higher fitness returns as their condition or fecundity improves. The pattern of sex ratio adjustment we found in Uroleucon cirsii indicates local mate competition among males, while the pattern we found in Rhopalosiphum padi suggests local resource competition among sexual females. This might be the first evidence for local resource competition among females in an invertebrate species. Local mate competition means that fitness returns are limited by the availability of females as mates within local breeding groups, whereas local resource competition means that fitness returns are limited by the availability of resources for females competing within local groups. We discuss how the life cycles of both species fit to these hypotheses.

海洋纤毛虫实验生态学研究I：不同浓度葡萄糖对种群增长的影响

为揭示不同碳氮比对纤毛虫种群增长的影响以及纤毛虫对碳源和能量来源的选择性 ,利用实验生态学方法 ,对海水养殖水体中 3种常见的纤毛虫原生动物 :扇形游仆虫 (Euplotesvannus)、海洋尾丝虫 (Uronemamarinum)和巨大拟阿脑虫 (Paranophrysmagna)在牛肉浸膏及梯度浓度葡萄糖培养基中的种群增长过程进行了初步的探讨 .数据分析表明 ,在牛肉浸膏培养基中加入不同浓度的葡萄糖对于纤毛虫种群增长影响显著 ,其中在 0 .0 5 gL-1葡萄糖浓度的培养基中 3种纤毛虫种群增长最佳 (P <0 .0 5 ) ,而在 0 .4 gL-1浓度时纤毛虫的生长繁殖均受到高度抑制 (P <0 .0 5 ) .这一结果显示 ,不同C N比对纤毛虫的种群增长有着直接的影响 .图 3表 3参 10     

Robust benchmark dose determination based on profile score methods

We investigate several methods commonly used to obtain a benchmark dose and show that those based on full likelihood or profile likelihood methods might have severe shortcomings. We propose two new profile likelihood-based approaches which overcome these problems. Another contribution is the extension of the benchmark dose determination to non full likelihood models, such as quasi-likelihood, generalized estimating equations, which are widely used in settings such as developmental toxicity where clustered data are encountered. This widening of the scope of application is possible by the use of (robust) score statistics. Benchmark dose methods are applied to a data set from a developmental toxicity study.     

2种常规水稻Cd、Zn吸收与器官分配的生育期变化：品种、土壤和Cd处理的影响

Cd在土壤-作物-膳食食物链中的迁移是人类对环境Cd暴露及其健康风险的主要途径,而水稻是子粒Cd积累最强的大宗作物之一.采用全生育期淹水盆栽试验研究了2种常规水稻(高Cd吸收品种“苏香粳1号”和低Cd吸收品种“99-22”)在添加Cd(2mg·kg-1)和不添加Cd处理下对2种土壤(红沙泥田,乌栅土)中Cd、Zn的吸收及其生育期变化.结果表明:1)常规水稻对Cd、Zn的吸收积累受土壤、品种和外源Cd的影响.Cd处理、土壤、品种间的正交互作用(高Cd吸收品种植于高Cd处理且Cd有效性高的红壤中)使常规稻植株Cd/Zn比成数十倍提高,从而使子粒Cd/Zn比产生强烈升高;2)水稻对Cd、Zn的吸收强度因不同生育期而异,Cd吸收的主要时期是分蘖期和成熟期,而Zn吸收的主要时期则是分蘖期、抽穗期和灌浆期.在整个生育期中,水稻Cd吸收伴随着对Zn的排斥现象,这在高Cd吸收下尤为强烈;3)水稻各器官对Cd、Zn的吸收分配无论是同品种的生育期间抑或同生育期时的不同品种间均有显著差异.Cd积累量为根系>穗粒>茎叶,而Zn却表现为茎叶>根系、穗粒.观察到水稻吸收的Cd在生育后期向穗粒的强烈运移.相对于低Cd吸收品种来说,Cd向穗粒转运较强,而Zn的转运较弱是高Cd吸收品种子粒Cd积累强而Cd/Zn比高的植株因素.     

Male influence on sex allocation in the parasitoid wasp Nasonia vitripennis

Sex allocation is an important reproductive decision for parents. However, it is often assumed that females have substantial control over sex allocation decisions, and this is particularly true in haplodiploid insects, in which females apparently determine sex by deciding whether to fertilise an egg (and produce a diploid daughter) or not (and produce a haploid son). Mechanisms by which males may influence sex allocation are not so straightforward, and their potential influence on sex ratios has been somewhat neglected. Here, we test whether males influence offspring sex ratios in the parasitoid wasp Nasonia vitripennis. We show that some of the variation in observed sex ratios can be attributed to males when comparing the affect of male strain on sex ratio. We did not find among-male variation in sex ratio with a less powerful experiment using males from only one strain or an effect of male mating environment. Our data suggest that males can influence female sex ratios and contribute to the variation around the sex ratios optimal for females. However, the influence is not large, suggesting that females have more influence on sex allocation than do males. We conclude by considering whether male influences on sex ratio represent differences in male reproductive competence or deliberate attempts by males to increase their fitness by influencing daughter production.     

Individual sex ratios and offspring emergence patterns in a parasitoid wasp, Melittobia australica (Eulophidae), with superparasitism and lethal combat among sons

Since the mating of the parasitoid wasp Melittobia australica occurs on their eclosed hosts, the sex ratio is predicted to follow the local mate competition (LMC) theory. However, while LMC models predict that the sex ratio will increase from female-biased toward a 1:1 ratio with an increase in the number of foundresses, the observed female-biased sex ratios (1–5% males) show little increase in response to an increased foundress number. Lethal combat among adult males may serve as an explanation for this observed phenomenon. Using a microsatellite DNA marker, we first examined the individual sex ratio of two foundresses who had sequentially parasitized the same host. Both foundresses produced an extremely female-biased clutch and the sex ratios of the second foundress were only slightly less biased than that of the first. A small number of sons from both foundresses emerged at a constantly low rate over a prolonged period, resulting in a temporal mixture of emerging males derived from both the foundresses. Second, we conducted a one-on-one arena experiment to examine the combat level in relation to the relatedness of the opponents. Almost all the later-emerging males were killed by previously eclosed males irrespective of whether they were sibs or non-sibs. These results suggest that each foundress should not produce males in a single burst, but continue to produce male eggs at a constantly low rate in order to avoid the high mortality of her own sons by lethal male-male combat. This combat may be one of factors in explaining the extremely female-biased sex ratio even with an increasing foundress number.Communicated by R.F.A. Moritz     

天津市东郊污水处理厂生物脱氮工艺设计

天津市东郊污水处理厂是新建投产的一座大型城市污水处理厂，其设计处理能力为４０００００ｍ￣３／ｄ。该厂引进了国外先进设备和技术，６００００ｍ￣３／ｄ污水采用前置缺氧脱氮的Ａ／Ｏ工艺进行了深化处理。本文全面论述了Ａ／Ｏ工艺曝气他的设计，并就设计参数取值、池型设计、进出水形式，回流方式和缺氧区与好氧区的容积比等进行了分析探讨。     

室内废气污染的计算与分析

通过对吸油烟机抽吸风场有效强度矢量图的测量 ,给出了吸油烟机质量技术检验方法和油烟废气、燃气废气污染泄漏量的计算方法 ;对油烟、燃气废气在厨房的扩散与循环作了详细分析 ,并对国标提出几点建议。     

金属粉末烧结材料泊松比模型的探讨

分析了粉末烧结材料泊松比与屈服准则的关系 ,指出了泊松比Kuhn模型的等价假设 ,比较了几种泊松比模型的特点 ,提出了一种能反映致密过程中密度较大时泊松比增长率减缓的特点的箕舌线函数型泊松比模型。