山西小麦"纬海"气候区划与瓦尔特气候图的分析应用

针对前人在作物生态分区上普遍采用包括纬度和海拔在内尽可能多的气候因子进行分区研究所存在的繁琐缺点,根据山西南北纬度差异大、多山海拔差异大的地貌特点,仅以纬度和海拔为依据,进行了小麦"纬海"气候区划.结果表明,以纬度和海拔为依据的分区结果与前人多因子分区结果一致,纬度和海拔与温、光、水等7个气候因子之间存在密切的回归关系,除海拔与年降水量之间的决定系数外,决定系数均达到显著或极显著水平.在小麦"纬海"区划的基础上,又对每个区的主要气候特征采用瓦尔特水热关联图进行了补充分析,做到宏观分区简便、微观分析细微而特征突出,二者结合,有利于指导生产之用.     

On the interpretation of test sensitivity in the two-test two-population problem: Assumptions matter

Bayesian analyses of diagnostic test accuracy often require the assumption of constant test accuracy among populations to ensure model identifiability. In a prior study (Toft, N., Jørgensen, E., Højsgaard, S., 2005. Diagnosing diagnostic tests: evaluating the assumptions underlying the estimation of sensitivity and specificity in the absence of a gold standard. Prev. Vet. Med. 68, 19–33), the sensitivity estimate from a two-test two-population model was shown to be weighted toward the population with the higher prevalence of infection. In the present study, we provided analytical formulae that give insight into the effect of assuming constant sensitivity when this assumption was false. To further investigate the effect of failure of the assumption of constant sensitivity, we also simulated several data sets under the assumption that the first test's sensitivity varied in the two populations. Bayesian conditional independence models that presumed constant sensitivities were implemented in WinBUGS and posterior estimates (mean and 95% probability intervals) were evaluated based on the known true values of the parameters. Findings from the Bayesian analyses of several scenarios indicated that the posterior mean was a good estimate of the weighted mean of the sensitivities in the two populations, when one test was perfectly specific. When neither test was perfectly specific, the Bayesian posterior mean for test 1 sensitivity was either greater than the larger of the two true sensitivities, or smaller than both, and estimates of prevalence and the second test's specificity were incorrect. The implication is that estimates of some parameters will be biased if test sensitivities are not constant across populations. Without a perfectly specific test, and if the assumption of constant sensitivity fails, the only solution we are aware of would involve incorporating prior information on at least two parameters.     

五四时期惠特曼诗歌体式对安徽诗人的影响——以胡适为核心的研究考察

美国著名诗人和评论家惠特曼提倡平民使用的“口语入诗”和“自由体式”契合了安徽诗歌革命和新诗发展的内在要求,从理论创作层面和创作实践层面给安徽诗人带来诗歌创作的灵感。胡适、蒋光慈、田间为代表的安徽诗人对惠特曼口语入诗的借鉴和模仿激发了安徽现代诗歌体式进一步向平民化方向转变,而自由体诗歌的引入则给安徽诗歌界带来不小的震动,对安徽古典诗歌产生一股强大的冲击力,为安徽诗歌的新变开拓了一条有效的路径。     

Mechanisms of bush encroachment and its inter-connection with rangeland degradation in semi-arid African ecosystems: a review

Many studies show that semi-arid rangelands throughout the world have been rapidly converted from a grassland state to a bush encroachment state during the past 50 years. Bush encroachment includes the spread of local woody species and/or incursion of woody species introduced from other ecosystems into semi-arid savannas and grassland ecosystems. Rangeland degradation due to bush encroachment causes several challenges, affecting the production of livestock and pastoral people livelihoods in most parts of Africa. Scientists have long been attempting to develop schematic and mathematical theories to explain the observed phenomenon of bush encroachment, and several theories were proposed and developed. The well-regarded theories include:(1) Walter's two-layer model,(2) Moir's one-layer model,(3) state-and-transition theory,(4) equilibrium theory,(5) disequilibrium theory, and(6) non-equilibrium theory. Within those theories, the most frequently-indicated driving factors that explain bush encroachment include over-grazing, availability of soil nutrient and moisture, elevated CO2 levels, frequency and intensity of fire, spread of seeds of woody species by livestock and wild animals. It should be stressed that couplings and interactions among diverse driving factors are more often at work in determining the condition of bush encroachment. To summarize, the effort in managing semi-arid ecosystems needs critical knowledge to understand the cause-effect relationships of underlying factors through integrated approach. Therefore, future research on encroachment of woody plants should be multi-discipline oriented and multi-partnership involved.     

沃益多生物菌剂在有机水稻上的应用效果

研究了沃益多生物菌剂在贺兰县有机水稻上的应用效果。结果表明:增施沃益多复合微生物菌剂,可使水稻返青早,生根快,实现早生快发;能促进水稻分蘖和生长;增产效果显著,并实现增收,为大面积推广应用提供科学依据。