Population biology of infectious diseases: Part II.

In the first part of this two-part article (Nature 280, 361--367), mathematical models of directly transmitted microparasitic infections were developed, taking explicit account of the dynamics of the host population. The discussion is now extended to both microparasites (viruses, bacteria and protozoa) and macroparasites (helminths and arthropods), transmitted either directly or indirectly via one or more intermediate hosts. Consideration is given to the relation between the ecology and evolution of the transmission processes and the overall dynamics, and to the mechanisms that can produce cyclic patterns, or multiple stable states, in the levels of infection in the host population.     

厦门海域面状前吻吸虫流行病学的调查研究

报告了在厦门海域面状前吻吸虫Prosorhynchus facilis (Ozaki,1924)Eckmann,1932流行病学的调查研究结果,指出其第一中间宿主——寻氏肌蛤Musculus senhousei的感染具有明显的季节性变化,而终未宿主则具有明显的宿主特异性。     

Schistosoma mansoni shares a protective oligosaccharide epitope with freshwater and marine snails

The expression of similar antigenic determinants by trematode parasites and their intermediate (invertebrate) or definitive (vertebrate) hosts has been previously reported. Studies of experimental and human infection by the parasite Schistosoma mansoni have revealed the strong immunogenicity of a surface antigen with a relative molecular mass (Mr) 38,000 (38K). Here we provide evidence that the important protective epitope of the 38K molecule is expressed by the uninfected intermediate host of S. mansoni, Biomphalaria glabrata and is synthesized both by the mollusc and by the parasite throughout its life cycle, thus confirming our original hypothesis. Deglycosylation experiments indicate that the protective epitope is an oligosaccharide and in B. glabrata, is associated with a 90K component. Analysis of soluble extracts from different freshwater mollusc species shows that the same protective epitope is found in schistosome as well as in non-schistosome hosts. Moreover, it was also found on the haemocyanin of the keyhole limpet (Megathura crenulata), a carrier protein widely used in immunological studies.     

导线贯通金属腔体电磁辐射耦合电流的计算方法

为研究电磁波辐射条件下电力系统中细贯通导线引入的电磁干扰问题,提出了一种利用等效电压元思想求解细导线耦合电流的新方法,推导出金属腔体加载贯通导线时线上电流分布的估算公式,分析了耦合电流分布规律.结果表明,贯通导线对入射电磁波具有频率选择特性,贯通导线的电长度为半波长整数倍时,贯通导线上电流谐振,谐振时线上耦合电流波峰数为n,而后采用信号发生器、电流探头等设备建立了含细贯通导线金属腔体电磁耦合实验平台,通过开展贯通导线连续波电磁辐射效应实验验证了该方法的有效性.      

考虑次网格水文过程的区域气候水文耦合方法

针对气候-水文耦合模型采用的计算网格较粗,不能很好地描述小尺度陆面水文过程的不足,以美国萨斯奎那西支子流域为研究区域,构建了考虑水力传导度和降雨次网格空间非均匀性的区域气候-水文耦合模型,从而在较粗的计算网格中描述较细的小尺度次网格水文过程.数值模拟结果表明,考虑次网格水文过程的耦合模型精度更高,模拟径流过程与实测过程拟合更好,并且提高了模型对水文物理过程的代表性.     

我国叶槽绦虫一新记录属(绦虫纲:四叶目)

报道检获于厦门海域赤虹(Dasyatis akajei)肠道中的四叶目叶槽科蔷薇属叶枕蔷薇绦虫Rhodobothrium pulvinatum Linton 1889，经鉴定比较。为我国鱼类绦虫属的新记录．本次共剖检赤虹46尾．阳性2尾．感染率为4．3％。感染强度为5～7条／尾．并对所获虫体进行了描述．     

竞争模型下连续发酵的最优控制问题

发酵法生产合生元的工业过程中,通过培养曲霉与酵母菌两个微生物,使其代谢产物达到最大值.本文将底物的补充速度看作是一个控制变量的控制函数,底物流出速度看做另一个控制变量的控制函数,在原monod动力学模型的基础上,提出了一个新的发酵模型,并对模型进行了数值模拟,解决了发酵的最优控制问题.     

并行网络中不同标注下的入侵特征阀值确定

传统入侵特征阈值确定方法通常通过敏感信息边界矢量确定,不适于环境复杂的并行网络,对多跳入侵的检测性能不佳。为此,提出一种新的并行网络中不同标注下的入侵特征阀值确定方法。介绍了并行网络体系结构,其主要包括嗅探器、主机、数据库、从动机和集群信道。对抗原信号进行描述,通过求出成熟环境抗原值对抗原异常度信息进行描述,构建异常度关联模型。利用指标集参数阈值的参考指标集和宿主属性对其进行训练,不停改变参数个数与入侵特征阈值,获取和抗原有关的关联规则;从而得到并行网络中不同标注下的入侵特征阈值。实验结果表明,采用所提方法确定的入侵特征阈值能够准确实现并行网络的入侵检测,且阈值确定效率高。     

基于改进 FA 算法与不完全 Beta 函数的图像增强技术

针对传统计算机在复杂图像信息分析以及后期处理不达预期的问题,提出了利用改进原始的萤火虫算法 (FA)在不完全 Beta 函数上动态寻优调整灰度曲线的光电图像增强新策略。 新策略主要从算法角度出发改进传统 FA 算法,针对原有的吸引度容易造成局部最优等问题引入新吸引度公式、针对算法陷入局部震荡添加自扰动和克 服陷入局部最优的迭代检测环节,改进完成的新算法(Firefly Algorithm Growth,FAG)结合非完全 Beta 函数动态寻 找最优值下的图像灰度曲线。 将改进的 FAG 与 FA 新老算法在四种常见基准函数上进行对比实验测试他们的性 能,结果显示改良 FAG 算法在性能上更优;在改良 FAG 结合非完全 Beta 与 FA 结合非完全 Beta 增强同一图像的 实验中加入直方图算法增强图像作为对照组,综合结果显示改进后的新策略更胜一筹。 综合结果显示群智能算法 在结合图像处理手段来达到图像增强的目的上具有很好的应用价值,新策略在低对比度条件下的光电图像实现了 有效的增强。     

玉米对MDMV的抗性与PO和SOD活性的关系

研究了不同抗性玉米人工接种DMDV后1周内的PO和SOD活性变化及其同工酶谱组成。结果表明：玉米感染MDMV后,PO活性发生明显变化,无论是抗、感品种PO活性比对照多有提高。但抗、感器种之间、接毒与对照之间比较,夏、秋两季采样测定结果不尽相同,尚难发现明显的特征性差异。抗、感品种、接毒与对照之间PO酶谱有差异,抗病品种的健康叶片带纹多、颜色重,而感病品种带纹少、颜色浅;抗病品种的接毒叶片比对照酶带加重或增添新酶带。抗病品种SOD活性的本底水平高于感病品种,接毒后SOD活性比健康对照提高但不明显,而感病品种SOD活性比健康对照提高明显,且活性逐渐增强。     

基于汉明码与从属像素补偿的半色调图像信息隐藏

提出了一种以半色调图像为载体的基于汉明码与从属像素补偿的信息隐藏方法. 将载体半色调图像像素分为主像素和从属像素, 主像素用来承载秘密信息, 从属像素作为主像素的补偿位, 通过从属像素的修改来避免隐写图像视觉效果下降. 与此同时, 主、从像素一一对应的配对方式简化了从属像素的选择, 提高了图像像素的利用率.在信息嵌入的过程中引入汉明码, 既提高了嵌入率, 又降低了原始像素的修改比例. 通过实验对比分析可以看出, 本方法在嵌入率和隐写图像的视觉效果上均超过了已有的半色调图像隐写方法.     

Gametocytogenesis by malaria parasites in continuous culture

Asexual proliferation of malaria parasites proceeds by multiplication of the parasites within red cells. Following rupture of the host cells the released merozoites re-invade other red cells. On re-invasion, a proportion of merozoites become, not asexual parasites but gametocytes, the sexual stages infective to the mosquito vectors. Conversion of asexual parasites to gametocytes occurs not only during natural infections but also in continuous in vitro culture as reported first by Trager and Jensen and by others. We showed previously that the proportion of early intra-erythrocytic stages (ring stages) of Plasmodium falciparum which developed into gametocytes in culture was influenced by culture conditions. Gametocyte formation was rare in conditions supporting rapid proliferation but frequent when parasite densisites were static. We now show that nearly 100% of ring stages develop into gametocytes in response to 1mM cyclic AMP in static cultures whereas in rapidly growing cultures few rings become gametocytes in response to cyclic AMP.     

Cleanliness of Ti-bearing Al-killed ultra-low-carbon steel during different heating processes

During the production of Ti-bearing Al-killed ultra-low-carbon (ULC) steel, two different heating processes were used when the converter tapping temperature or the molten steel temperature in the Ruhrstahl-Heraeus (RH) process was low:heating by Al addition during the RH decarburization process and final deoxidation at the end of the RH decarburization process (process-I), and increasing the oxygen content at the end of RH decarburization, heating and final deoxidation by one-time Al addition (process-Ⅱ). Temperature increases of 10℃ by different processes were studied; the results showed that the two heating processes could achieve the same heating effect. The T.[O] content in the slab and the refining process was better controlled by process-I than by process-Ⅱ. Statistical analysis of inclusions showed that the numbers of inclusions in the slab obtained by process-I were substantially less than those in the slab obtained by process-Ⅱ. For process-I, the Al₂O₃ inclusions produced by Al added to induce heating were substantially removed at the end of decarburization. The amounts of inclusions were substantially greater for process-Ⅱ than for process-I at different refining stages because of the higher dissolved oxygen concentration in process-Ⅱ. Industrial test results showed that process-I was more beneficial for improving the cleanliness of molten steel.     

一种分层的软件过程执行机制的研究

选择不同的过程执行机制会对软件过程支持的灵活性产生影响,两种传统的过程执行机制———前摄式和反应式存在模型复杂性和执行灵活性之间的矛盾.借鉴了Alf Inge Wanget al.所提出的基于组织中过程执行主体分层支持的思想,提出了一种分层过程机制,该机制将软件过程分为两个层次,底层是具有流程稳定的子过程,采用前摄式机制支持,而高层是易于变化的过程,则用反应式机制支持,通过过程片段将两层过程统一在一个过程模型中既增加了过程执行的灵活性,又降低了过程模型的复杂性.为了说明该过程机制的实践有效性,分析了一个案例所发生的“例程”、“并发”、“反馈”和“等待”的各种情况并且阐述了在CPMS系统中应用分层机制对上述情况的解决方案.     

钝化304不锈钢单晶在硫酸含氯介质中的孔蚀

采用交流阻抗技术,研究钝化304不锈钢单晶体在pH1.0,0.25mol/lNa_2SO_4含氯介质中的孔蚀行为。对孔蚀过程中的阻抗频谱特征进行了分析,提出孔蚀的发生和发展过程中都有复合物(MOHC1)形成。复合物进一步吸附更多的氯离子,导致溶解反应发生。并提出一个孔蚀的的反应机理模型,它与304不锈钢多晶体在硫酸含氯介质中的孔蚀机理没有本质的差别。     

Incremental frequent tree-structured pattern mining from semi-structured data

The paper studies the problem of incremental pattern mining from semi-structrued data. When a new dataset is added into the original dataset, it is difficult for existing pattern mining algorithms to incrementally update the mined results. To solve the problem, an incremental pattern mining algorithm based on the rightmost expansion technique is proposed here to improve the mining performance by utilizing the original mining results and information obtained in the previous mining process. To improve the efficiency, the algorithm adopts a pruning technique by using the frequent pattern expansion forest obtained in mining processes. Comparative experiments with different volume of initial datasets, incremental datasets and different minimum support thresholds demonstrate that the algorithm has a great improvement in the efficiency compared with that of non-incremental pattern mining algorithm.     

TiO2对合成渣中Fe2O3还原发泡过程的影响

研究了不同条件下TiO2和Fe2O3在合成渣中被碳还原时的发泡过程．计算了该发泡过程的发泡系数、消泡系数、平均发泡寿命、发泡强度和消泡过程开始的时间．用熔渣发泡参数定量地讨论了温度、TiO2加入量和初渣中TiC的含量对熔渣发泡过程的影响，发现当初渣中TiC的含量和TiO2加入量较多时，在发泡时会产生二次发泡现象．     

A rhoptry-protein-associated mechanism of clonal phenotypic variation in rodent malaria

The recognition and invasion of host cells are mediated by components of the apical complex of the ookinete, sporozoite and merozoite stages of Plasmodium parasites. The paired rhoptries (organelles involved in host-cell recognition) in the apical complex contain many proteins of as-yet unknown function. In the rodent malaria agent P. yoelii yoelii, a multigene family codes for merozoite rhoptry proteins of relative molecular mass 235,000 (p235 proteins); these proteins are thought to determine the subset of erythrocytes that the parasites invade. Further support for this idea came from the identification of a region in p235 with weak but significant homology to reticulocyte-binding protein-2 of P. vivax and the demonstration that at least one p235 member binds to the erythrocyte surface membrane. Here, using single, micromanipulated P.y.yoelii parasites, we describe a new mechanism of gene expression by which the merozoites originating from a single schizont each express a distinct member of this multigene family. We propose that this new type of clonal phenotypic variation provides the parasite with a survival strategy in the mammalian host; this strategy contributes to the observed chronicity of malarial infections. This phenomenon is genetically and functionally distinct from classical antigenic variation, which is mediated by the var multigene family of P. falciparum.     

On the Mathematical Nature of Wireless Broadcast Trees

Trees are arguably one of the most important data structures widely used in information theory and computing science. Different numbers of intermediate nodes in wireless broadcast trees may exert great impacts on the energy consumption of individual nodes, which are typically equipped with a limited power supply in a wireless sensor network; this limitation may eventually determine how long the given wireless sensor network can last. Thus, obtaining a deep understanding of the mathematical nature of wireless broadcast trees is of great importance. In this paper, we give new proof of Cayley's well-known theorem for counting labeled trees. A distinct feature of this proof is that we purely use combinatorial structures instead of constructing a bijection between two kinds of labeled trees, which is in contrast to all existing proofs. Another contribution of this work is the presentation of a new theorem on trees based on the number of intermediate nodes in the tree. To the best of our knowledge,this work is the first to present a tree enumeration theorem based on the number of intermediate nodes in the tree.