Comparative study of the karyotypes of two Egyptian species of bats,Taphozous perforatus andTaphozous nudiventris (Chiroptera: Mammalia)

A detailed karyotypic analysis of two Egyptian species of bats,Taphozous perforatus andTaphozous nudiventris, was made on the basis of conventional data and G-band patterns. No detectable karyotypic difference was found between the two species (2n=42, F.N. 64). By comparison of G-band patterns, some differences between the two species were seen in the corresponding autosomal pairs. These results are reported for the first time in Egypt.     

Indoxyl derivatives of drug metabolites

Summary Indoxyl derivatives were detected as minor products among the urinary metabolites of two trial drugs, a benzodiazepine (GP 55 129) and a benzophenone (CGP 11 952). Their structures were elucidated by NMR and mass spectroscopy. Presumably, metabolites containing potential aldehyde functions react spontaneously with endogenous indoxyl. Such derivatives have not hitherto been encountered in drug metabolism.     

Nras loss induces metastatic conversion of Rb1-deficient neuroendocrine thyroid tumor

Mutations in the gene encoding the retinoblastoma tumor suppressor predispose humans and mice to tumor development. Here we have assessed the effect of Nras loss on tumor development in Rb1 heterozygous mice. Loss of one or two Nras alleles is shown to significantly reduce the severity of pituitary tumors arising in Rb1(+/-) animals by enhancing their differentiation. By contrast, C-cell thyroid adenomas occurring in Rb1(+/-) mice progress to metastatic medullary carcinomas after loss of Nras. In Rb1(+/-)Nras(+/-) animals, distant medullary thyroid carcinoma metastases are associated with loss of the remaining wild-type Nras allele. Loss of Nras in Rb1-deficient C cells results in elevated Ras homolog family A (RhoA) activity, and this is causally linked to the invasiveness and metastatic behavior of these cells. These findings suggest that the loss of the proto-oncogene Nras in certain cellular contexts can promote malignant tumor progression.     

新世纪图书馆员社会角色转换研究综述

就近几年图书馆界关于新世纪馆员意识转换及社会角色转换等方面的研究进行了综述，指出新时期的馆员要实现自我社会角色的转换，首先是要明确转换的必要性，然后采取有效的策略逐步地、系统地推进转换，才能取得较好的效果。     

Sound communication inNezara viridula (L.) (Heteroptera: Pentatomidae): Further evidence that signal transmission is substrate-borne

We investigated the sound communication associated with mating inNezara viridula (L.) to clarify conflicting reports on the medium through which acoustic signals are borne. Recordings made from virgin pairs ofN. viridula during precopulatory and compulatory behaviour have revealed that signals transmitted as vibrations through the substrate are a more likely means of communication than signals transmitted by a radiation of sound pressure waves through the air (at least in Australian populations). We present evidence (additional to that already in the literature) that air-borne acoustics are an unlikely mechanism of sexual communication in this species. Specifically, the recorded pulse train patterns showed no consistency or repeatability in relation to different stages of mating behaviour. In contrast, frequency spectrograms of substrate-borne signals reveal repeatable patterns that do correspond with the stage of mating behaviour.     

氧化物半导瓷中晶界势垒的起源

提出了一个关于氧化物半导瓷晶界势垒起源的新观点，认为晶界势垒起源于烧结过程中外界氧在晶界中的扩散，与材料的结构、化学缺陷、掺杂、外界气氛、烧结工艺、组成状态等有密切关系，并用此理论解释了许多实验现象。     

交织扩展Golay码编译码器实现方案的研究

论述了交织编码的工作原理，给出了一种交织扩展Ｇｏｌａｙ码的改进型软件设计方案，用ＴＭＳ３２０Ｃ２５实现了其编译码器并给出了模拟实验结果。实验结果表明，它能准确地纠正不大于７２比特位的差错；处理１２８×１２８×８比特位的一幅图像数据的运行时间为０．４１２ｓ．     

激光开槽、埋槽电极硅太阳电池

报道一种新颖的激光开槽、埋槽电极硅太阳电池的结构、工艺流程及其研制结果。在ＡＭ１．５，２５℃，１００ｍＷ／ｃｍ２的条件下，以面积为４５ｃｍ３的３６片硅片研制的硅太阳电池的输出参数的平均值为ＪＳＣ＝３６．１ｍＡ／ｃｍ２，Ｖ∞＝６３３ｍＶ，Ｆ．Ｆ．＝０．７９８，η＝１８．２３％，最后分析了种高性能硅太阳电池的设计特点。     

Development and function of T cells in mice rendered interleukin-2 deficient by gene targeting.

Interleukin-2 (IL-2) is a lymphocytotropic hormone which is thought to have a key role in the immune response of mammalian cells. It is produced by a subpopulation of activated T-lymphocytes and acts in vitro as the principal auto- and paracrine T-cell growth factor (for reviews see refs 1-3). IL-2 is, however, not the sole T-cell growth factor, nor does it act exclusively on T cells, also promoting growth of NK cells and differentiation of B cells. A role for IL-2 in T-cell development has been postulated but remains controversial. Here we test the requirement for IL-2 in vivo using IL-2-deficient mice generated by targeted recombination. We find that mice homozygous for the IL-2 gene mutation are normal with regard to thymocyte and peripheral T-cell subset composition, but that a dysregulation of the immune system is manifested by reduced polyclonal in vitro T-cell responses and by dramatic changes in the isotype levels of serum immunoglobulins.     

Aeromonas caviae: ecologic adaptation in the intestinal tract of infants coupled to adherence and enterotoxin production as factors in enteropathogenicity

Aeromonas caviae isolated from stools of diarrheic formula-fed infants and environmental sources produce acetic acid when grown in glucose broth, which is bactericidal (suicide phenomenon). A. caviae grows anaerobically in a minimal medium or under permissive conditions such as the intestinal tract of formula-fed infants. These isolates adhered to HEp-2 cells and produced a cytotoxic and a cytotonic enterotoxin which underscore their enteropathogenicity.