Subset threshold autoregression

We develop in this paper an efficient way to select the best subset threshold autoregressive model. The proposed method uses a stochastic search idea. Differing from most conventional approaches, our method does not require us to fix the delay or the threshold parameters in advance. By adopting the Markov chain Monte Carlo techniques, we can identify the best subset model from a very large of number of possible models, and at the same time estimate the unknown parameters. A simulation experiment shows that the method is very effective. In its application to the US unemployment rate, the stochastic search method successfully selects lag one as the time delay and five best models from more than 4000 choices. Copyright © 2003 John Wiley & Sons, Ltd.     

过路黄克隆生长对光照强度的反应

利用遮阳网产生光照梯度，以研究光照强度对克隆植物过路黄(Lysimachia christinae)形态特征和生物量分配的影响．结果表明：1)匍匐茎节间长度随光照强度的减弱而增大，遮荫明显增加过路黄的分枝角度，分枝强度没有对光强发生显著反应．遮荫使叶柄变长，而根长则变短．2)随光照强度的减弱，叶柄生物量逐渐增大；遮荫降低了叶生物量、根生物量、总生物量、根生物量比和地下生物量／地上生物量．3)在遮荫条件下，一级匍匐茎基部分株的叶生物量和分株总生物量显著大于顶部分株，而根冠比则相反．根的生物量在各分株间无显著差异．在不遮荫条件下，仅匍匐茎基部分株的叶生物量大于顶部分株，其它的生物量指标在各分株间无显著差异．在分株水平，分株的根冠比不受光强的影响．总之，过路黄的克隆生长在基株和分株水平都对光强作出了明显的反应，而且这种反应具有等级性．     

森林火灾的烟尘危害及烟呛救护

论述了森林火灾发生的条件及在燃烧过程中产生的烟尘危害，针对防火队员进行救护教育要求，在扑救森林火灾过程中扑火人员应密切注视火势，在遇到各种紧急情况时，学会避险和突围，必要时采取自救措施，把扑火人员的伤亡降到最低限度。     

工业毒物对女工生殖危害的调查研究

为了解工业毒物对女工的生殖危害,对重庆市的制药、农药、化工、机械4种行业中的6个企业的已婚女工进行问卷调查.结果表明:接触组女工出现月经经期异常、周期异常、经期不适以及妊娠并发症的阳性率均显著高于对照组(P<0 05).接触组阴道炎、盆腔炎、宫颈炎患病率均高于对照组(P<0 05).接触组中工龄大于10a的妇科肿瘤发生率明显高于对照组(P<0 05).认为工业毒物可能致妇科疾病和妇科肿瘤.     

Sol-Gel水热偶合法制备纳米AlOOH的晶相转变

以日本理学3015 X射线衍射仪研究了Sol-Gel 水热偶合法制备纳米AlOOH的晶相转变.(1) 在pH3.5、时间5 h、温度低于130 ℃时,主要生成三水铝;当温度高于130 ℃且升高至150 ℃时,三水铝完全转化为AlOOH;(2) 在pH3.5、温度150 ℃、时间小于3 h时,物相以三水铝和AlOOH共存,随时间延长至5 h,三水铝完全转化为AlOOH;(3) 在反应温度150 ℃、时间5 h、pH＞8.0时,三水铝的含量随pH的增大而增加,pH＜6.0才能转化为AlOOH .     

Anaerobic ammonium oxidation by anammox bacteria in the Black Sea

The availability of fixed inorganic nitrogen (nitrate, nitrite and ammonium) limits primary productivity in many oceanic regions. The conversion of nitrate to N2 by heterotrophic bacteria (denitrification) is believed to be the only important sink for fixed inorganic nitrogen in the ocean. Here we provide evidence for bacteria that anaerobically oxidize ammonium with nitrite to N2 in the world's largest anoxic basin, the Black Sea. Phylogenetic analysis of 16S ribosomal RNA gene sequences shows that these bacteria are related to members of the order Planctomycetales performing the anammox (anaerobic ammonium oxidation) process in ammonium-removing bioreactors. Nutrient profiles, fluorescently labelled RNA probes, 15N tracer experiments and the distribution of specific 'ladderane' membrane lipids indicate that ammonium diffusing upwards from the anoxic deep water is consumed by anammox bacteria below the oxic zone. This is the first time that anammox bacteria have been identified and directly linked to the removal of fixed inorganic nitrogen in the environment. The widespread occurrence of ammonium consumption in suboxic marine settings indicates that anammox might be important in the oceanic nitrogen cycle.     

A general model for ontogenetic growth.

Several equations have been proposed to describe ontogenetic growth trajectories for organisms justified primarily on the goodness of fit rather than on any biological mechanism. Here, we derive a general quantitative model based on fundamental principles for the allocation of metabolic energy between maintenance of existing tissue and the production of new biomass. We thus predict the parameters governing growth curves from basic cellular properties and derive a single parameterless universal curve that describes the growth of many diverse species. The model provides the basis for deriving allometric relationships for growth rates and the timing of life history events.     

The response of cyclic 3',5'-AMP and cyclic 3',5'-GMP phosphodiesterases to experimental diabetes

Alloxan diabetes caused a decrease in cyclic AMP phosphodiesterase in all affected rat tissues. Cyclic GMP phosphodiesterase activity was, however, decreased in adipose and liver, but increased increased in heart and uterus.