Synopsis of the life cycles of Digenea (Platyhelminthes) from lagoons of the northern coast of the western Mediterranean

The present document reports on the large amount of data relating to digenean parasites recorded from or known to be present in various hosts in lagoons of the northern coast of the western Mediterranean, which has been compiled from the literature of more than a century. In these lagoons, at least 72 nominal species of digeneans have been recorded. This total corresponds to approximately 12% of the 584 “marine” digenean species reported for Europe. Data are provided on the life cycles of 56 digenean species. The life cycle has been totally elucidated for 44 species (25 from fish, 19 from birds), and partly for the other 12 species (seven from fish, five from birds). This means that the life cycle is known for 61.1% of the recorded fauna (44/72) and partly for 16.7%, but remains unknown for 22.2%, making it, in this respect, one of the best understood digenean marine faunas in the world. In addition, a checklist is provided dealing with the cercarial and metacercarial forms recorded from lagoons of the northern coast of the western Mediterranean, which have been described only on the basis of characters of these larval stages and which remain without demonstrated links to a corresponding sexual adult stage in a vertebrate.     

一个定理证明的商榷

指出关于生化反应中微分方程权限环存在性的一个证明中的错误，重新给出了证明。     

细胞冷冻损伤机理的几个假说

本文对细胞冷冻损伤机理的几个假说作了简要介绍．     

On the Gracefulness of the Digraphs n·Cm＊

A digraph D（V, E） is said to be graceful if there exists an injection f ： V（G） →{0, 1,... , ｜E｜} such that the induced function f＇ ： E（G） --~ {1, 2,… , ｜E｜} which is defined by f＇ （u, v） = [f（v） - f（u）] （rood ｜E｜＋ 1） for every directed edge （u, v） is a bijection. Here, f is called a graceful labeling （graceful numbering） of D（V, E）, while f＇ is called the induced edge＇s graceful labeling of D. In this paper we discuss the gracefulness of the digraph n- Cm and prove that n. Cm is a graceful digraph for m = 15, 17 and even     

线性多部门经济系统的经济周期问题

利用线性多部门经济系统的投入矩阵的特征值和特征向量的性质来研究宏观经济系统的经济周期问题 ,并提出了经济周期的长度与系统开放程度成正相关关系。从中我们得出 :要以最佳状态发展经济就是合理有效地利用经济周期规律。     

冰冻干燥法保存花粉的研究

本文采用冰冻干燥法对白菜、泡桐、木香花的花粉进行处理,室温保存30～45天,花粉保持较高的生命活力。     

基于遗传算法BP网络的冻结方案优化设计

多圈管冻结方案设计与优化是深井冻结法凿井的一项关键技术,现今的理论和实践尚未成熟和完善,为此提出了基于遗传算法优化BP网络结构进行多圈管冻结方案的优化设计算法,将该算法求解的多圈管冻结设计方案与原方案进行了比较分析,表明了这种算法达到了较好的优化设计效果,为多圈管冻结方案设计及其优化提供了重要参考。     

Seasonal prediction of European cereal prices: good forecasts using bad models?

Because of their natural adherence to the climate and pronounced seasonal cycles, prices of field crops constitute an interesting field for exploring seasonal time series models. We consider quarterly prices of two major cereals: barley and wheat. Using traditional in‐sample fit and moving‐window techniques, we investigate whether seasonality is deterministic or unit‐root stochastic and whether seasonal cycles have converged over time. We find that seasonal cycles in the data are mainly deterministic and that evidence on common cycles across countries differs for the two commodities. Out‐of‐sample prediction experiments, however, yield a ranking with respect to accuracy that does not match the statistical in‐sample evidence. Parametric bootstrap experiments establish that the observed mismatch is indeed an inherent and systematic feature. Copyright © 2008 John Wiley & Sons, Ltd.     

冻融循环和氯盐侵蚀作用下钢筋与混凝土的粘结性能

为了研究冻融循环和氯盐侵蚀两种因素对钢筋与混凝土粘结性能的影响,本文设计了光圆钢筋和螺纹钢筋两种钢筋混凝土试件,对其在三种不同冻融次数（15次、25次、50次）和三种不同浓度（3.5%、7%、10%）氯盐溶液条件下进行试验,探讨钢筋混凝土试件试验后的粘结性能退化规律。结果表明：光圆钢筋试件表现为拔出破坏,螺纹钢筋试件表现为劈裂破坏,当冻融循环次数较少时,钢筋与混凝土之间的粘结性能随着氯盐侵蚀程度的增加略有提高,当冻融循环次数大于等于25次时,粘结性能随氯盐浓度的增加而变差,冻融破坏程度不同,钢筋与混凝土粘结性能随氯盐浓度大小变化的敏感程度不同。最后根据试验结果拟合出冻融氯盐侵蚀后试件的粘结强度—滑移本构关系。     

变管径冻结管对地铁联络通道冻结温度场的影响分析

在地铁联络通道的冻结法的设计与施工中,冻结管通常为倾斜放射布置。这导致联络通道不同横截面冻结管间距不同,最终引起冻结温度场的不均匀发展。以郑州地铁5号线联络通道为背景,在冻结管内盐水流量不变的情况下,对现行冻结管的尺寸做出调整,通过改变冻结管尺寸来改变管内的盐水在不同位置的流速,从而改变冻结管不同截面的对流换热系数,使联络通道的冻结温度场得到均匀发展。利用ADINA数值分析软件对联络通道冻结法设计建立三维模型,分析改变管径后,整个冻结过程中联络通道各个截面温度场的发展情况。结果表明,在同一冻结工程中,联络通道各个截面的冻结壁厚度及冻结平均温度趋于一致,且冻土交圈完成的时间得到了缩短,这表明通过改变冻结管的尺寸能够显著改善冻结温度场的不均匀发展问题。