Otavipithecus namibiensis, first Miocene hominoid from southern Africa.

We report here the discovery of a Miocene hominoid from Berg Aukas, Namibia, the first known from the African continent south of equatorial East Africa. This represents a major range extension of Miocene Hominoidea in Africa to latitude 20 degrees S. The holotype, a right mandibular corpus preserving the crowns of the P4-M3, partial crown and root of the P3, partial root of the canine, alveoli for all four incisors, and partial alveolus for the left canine, was found during paleontological explorations of karst-fill breccias in the Otavi region of northern Namibia. The mandible has unique characteristics that differentiate it from other middle Miocene hominoids of Africa and Eurasia and represents the only fossil evidence documenting a pre-australopithecine stage of hominoid evolution in southern Africa. Faunal analyses indicate that the breccia block containing the specimen accumulated during the latter part of the middle Miocene, about 13 +/- 1 Myr. Fauna from other breccia blocks at Berg Aukas are of diverse ages, including the earlier part of the middle Miocene, the upper Miocene, Plio-Pleistocene and Holocene.     

Fusarium solani cutinase is a lipolytic enzyme with a catalytic serine accessible to solvent.

Lipases belong to a class of esterases whose activity on triglycerides is greatly enhanced at lipid-water interfaces. This phenomenon, called interfacial activation, has a structural explanation: a hydrophobic lid, which at rest covers the catalytic site, is displaced on substrate or inhibitor binding and probably interacts with the lipid matrix. Fusarium solani pisi cutinase belongs to a group of homologous enzymes of relative molecular mass 22-25K (ref. 7) capable of degrading cutin, the insoluble lipid-polyester matrix covering the surface of plants, and hydrolysing triglycerides. Cutinases differ from classical lipases in that they do not exhibit interfacial activation; they are active on soluble as well as on emulsified triglycerides. Cutinases therefore establish a bridge between esterases and lipases. We report here the three-dimensional structure of a recombinant cutinase from F. solani pisi, expressed in Escherichia coli. Cutinase is an alpha-beta protein; the active site is composed of the triad Ser 120, His 188 and Asp 175. Unlike other lipases, the catalytic serine is not buried under surface loops, but is accessible to solvent. This could explain why cutinase does not display interfacial activation.     

Tumour necrosis factor alpha restores granulomas and induces parasite egg-laying in schistosome-infected SCID mice.

Schistosomiasis (bilharzia) is a parasitic disease caused by several species of schistosome worms (blood flukes). The key pathogenic event in this disease is the formation of granulomas around schistosome eggs trapped in portal venules of the liver. Granulomas are a distinctive form of chronic inflammation characterized by localized aggregation of activated macrophages around an inciting stimulus. Each granuloma evolves to form a fibrous scar; in schistosomiasis, the result is widespread hepatic fibrosis and portal hypertension. To identify the specific immune signal molecules necessary for granuloma formation, we studied schistosome infections in severe combined immunodeficient (SCID) mice, which have normal macrophages but lack functional B or T lymphocytes. Here we report that the immunoregulatory cytokine tumour necrosis factor alpha is necessary and sufficient to reconstitute granuloma formation in schistosome-infected SCID mice. Moreover, we find that the parasitic worms require tumour necrosis factor alpha for egg-laying and for excretion of eggs from the host. The implication of this latter result is that the parasite has adapted so successfully to its host that it uses a host-derived immunoregulatory protein as a signal for replication and transmission.     

Rapid switching to multiple antigenic and adhesive phenotypes in malaria.

Adhesion of parasitized erythrocytes to post-capillary venular endothelium or uninfected red cells is strongly implicated in the pathogenesis of severe Plasmodium falciparum malaria. Neoantigens at the infected red-cell surface adhere to a variety of host receptors, demonstrate serological diversity in field isolates and may also be a target of the host-protective immune response. Here we use sequential cloning of P. falciparum by micromanipulation to investigate the ability of a parasite to switch antigenic and cytoadherence phenotypes. Our data show that antigens at the parasitized cell surface undergo clonal variation in vitro in the absence of immune pressure at the rate of 2% per generation with concomitant modulations of the adhesive phenotype. A clone has the potential to switch at high frequency to a variety of antigenic and adhesive phenotypes, including a new type of cytoadherence behaviour, 'auto-agglutination' of infected erythrocytes. This rapid appearance of antigenic and functional heterogeneity has important implications for pathogenesis and acquired immunity.     

锁相环直流调速系统及其稳定性分析

本文给出了一个在传统转速电流双闭环基础上增加锁相环路构成的直流调速系统。该系统具有稳定性好,稳态精度高,调速范围宽的优点。文中给出了系统的稳定性分析及参数设计方法。     

杂多酸荷移跃迁盐系列研究（Ⅰ）—Keggin结构杂多酸的荷移跃迁盐的合成和表征

利用电解结晶法合成了Ｋｅｇｇｉｎ结构杂多酸荷移跃迁盐（ＢＥＤＴ－ＴＴＦ）８［ＰＭｏ３ＮｂＷ８Ｏ４０］．Ｘ－射线衍射测定为单斜晶系．晶胞参数ａ＝１４．２０（０）×１０（－８）ｃｍ；ｂ＝４３．３９（０）×１０（－８）ｃｍ；ｃ＝１３．５５（６）×１０（－８）ｃｍ；β＝９１°；Ｖ＝８．３５３×１０（－２１）ｃｍ３．该化合物具半导体性质。σｒ．ｔ＝３．７×１０（－２）Ｓｃｍ（－１）．ＥＡ＝１６０ｍｅＶ．变温磁化率测定表明其为Ｓｐｉｎ－Ｐｅｉｅｒｌｓ体系．     

黑曲霉胞外葡萄糖淀粉酶的纯化及特性

黑曲霉（Ａｓｐｅｒｇｉｌｌｕｓｎｉｇｅｒ７２８）的粗酶液，经硫酸铵沉淀，ＳｅｐｈａｄｅｘＧ－２５柱凝胶过滤脱盐，ＤＥＡＥ－Ｔｏｙｏｐｅａｒｌ离子交换柱层析和ＳｅｐｈａｃｒｙＳ－１００凝胶层析纯化，经ＰＡＧＥ鉴定为一条带ＳＤＳ凝胶电泳测定分子量为７００００．金属离子Ｆｅ３＋对该酶有一定的抑制作用，该酶的等电点为３．７，最适ｐＨ为４，最适温度为６０℃．Ｅ２８０１％为１５．７２，Ｋｍ值为０．１１２×１０－３ｍ．     

木槿（Hibiscus syriacusL.）耐盐变异体的选择

木槿愈伤组织耐盐细胞系是在含ＮａＣｌ的培养基上通过屡代选择产生的，在无盐培养其中进行几代继代培养后的愈伤组织，由其分化的芽以及脱分化增殖的愈伤组织均表现了耐盐性，木槿耐盐细胞由于对ＮａＣｌ的反应比未经选择的细胞积累了更多的Ｎ＾＋，Ｋ＾＋，而且细胞体积较小。     

建筑火灾综合模拟评估在大空间建筑火灾中的初步应用

运用火灾规律双重性理论，探讨建筑火灾综合模拟评估的理论框架，以影院会堂类大空间建筑为例，运用一些可调试的模拟方法、统计分析及其模型，给出在火灾评估具体环节和应用程式上的一定程度的量化描述．实现火灾综合模拟评估理论模型的可操作性，使更进一步准确和方便地估算建筑火灾对人员、财产造成危害的几率，和判断这种危害的发生具备了初步的可能．