证明嵌入式系统设计的UML-B规约

本书介绍了贯穿整个模块系统设计方法论的系统性质形式证法。该方法沦将子系统的共同验证与虚拟系统部件的系统精化和复用性相结合，通过规约的形式与非形式方法相结合，由UML和B语言来完成。这样就允许通过经证明的子系统的合成来验证系统规约（对于接口则给予某些特别的注意，符合VSIA／SLIF方法）。将B语言与C、VHDL和SystemC语言相连。将通过构造校正设计的过程扩展到较低的单片系统开发阶段。因此证明嵌入式软件产品是与证明硬件产品相配套的。书中开发了用于从UML和B语言产生代码的原型工具，现有的B语言验证工具被拓展成支持IP的再使用，这部是根据VSIA的推荐。书中所涉及的方法论及工具是通过开发三个工业应用来验证的，即无线移动终端、建立在HIPERLAN／2协议基础上的电信单片系统、以及汽车的防碰撞组件。     

Conformational change and protein-protein interactions of the fusion protein of Semliki Forest virus

Fusion of biological membranes is mediated by specific lipid-interacting proteins that induce the formation and expansion of an initial fusion pore. Here we report the crystal structure of the ectodomain of the Semliki Forest virus fusion glycoprotein E1 in its low-pH-induced trimeric form. E1 adopts a folded-back conformation that, in the final post-fusion form of the full-length protein, would bring the fusion peptide loop and the transmembrane anchor to the same end of a stable protein rod. The observed conformation of the fusion peptide loop is compatible with interactions only with the outer leaflet of the lipid bilayer. Crystal contacts between fusion peptide loops of adjacent E1 trimers, together with electron microscopy observations, suggest that in an early step of membrane fusion, an intermediate assembly of five trimers creates two opposing nipple-like deformations in the viral and target membranes, leading to formation of the fusion pore.     

Microscopic artificial swimmers

Microorganisms such as bacteria and many eukaryotic cells propel themselves with hair-like structures known as flagella, which can exhibit a variety of structures and movement patterns. For example, bacterial flagella are helically shaped and driven at their bases by a reversible rotary engine, which rotates the attached flagellum to give a motion similar to that of a corkscrew. In contrast, eukaryotic cells use flagella that resemble elastic rods and exhibit a beating motion: internally generated stresses give rise to a series of bends that propagate towards the tip. In contrast to this variety of swimming strategies encountered in nature, a controlled swimming motion of artificial micrometre-sized structures has not yet been realized. Here we show that a linear chain of colloidal magnetic particles linked by DNA and attached to a red blood cell can act as a flexible artificial flagellum. The filament aligns with an external uniform magnetic field and is readily actuated by oscillating a transverse field. We find that the actuation induces a beating pattern that propels the structure, and that the external fields can be adjusted to control the velocity and the direction of motion.     

Insect behaviour: arboreal ants build traps to capture prey

To meet their need for nitrogen in the restricted foraging environment provided by their host plants, some arboreal ants deploy group ambush tactics in order to capture flying and jumping prey that might otherwise escape. Here we show that the ant Allomerus decemarticulatus uses hair from the host plant's stem, which it cuts and binds together with a purpose-grown fungal mycelium, to build a spongy 'galleried' platform for trapping much larger insects. Ants beneath the platform reach through the holes and immobilize the prey, which is then stretched, transported and carved up by a swarm of nestmates. To our knowledge, the collective creation of a trap as a predatory strategy has not been described before in ants.     

Mutations in PCSK9 cause autosomal dominant hypercholesterolemia

Autosomal dominant hypercholesterolemia (ADH; OMIM144400), a risk factor for coronary heart disease, is characterized by an increase in low-density lipoprotein cholesterol levels that is associated with mutations in the genes LDLR (encoding low-density lipoprotein receptor) or APOB (encoding apolipoprotein B). We mapped a third locus associated with ADH, HCHOLA3 at 1p32, and now report two mutations in the gene PCSK9 (encoding proprotein convertase subtilisin/kexin type 9) that cause ADH. PCSK9 encodes NARC-1 (neural apoptosis regulated convertase), a newly identified human subtilase that is highly expressed in the liver and contributes to cholesterol homeostasis.     

ER-phagosome fusion defines an MHC class I cross-presentation compartment in dendritic cells

Induction of cytotoxic T-cell immunity requires the phagocytosis of pathogens, virus-infected or dead tumour cells by dendritic cells. Peptides derived from phagocytosed antigens are then presented to CD8+ T lymphocytes on major histocompatibility complex (MHC) class I molecules, a process called "cross-presentation". After phagocytosis, antigens are exported into the cytosol and degraded by the proteasome. The resulting peptides are thought to be translocated into the lumen of the endoplasmic reticulum (ER) by specific transporters associated with antigen presentation (TAP), and loaded onto MHC class I molecules by a complex "loading machinery" (which includes tapasin, calreticulin and Erp57). Here we show that soon after or during formation, phagosomes fuse with the ER. After antigen export to the cytosol and degradation by the proteasome, peptides are translocated by TAP into the lumen of the same phagosomes, before loading on phagosomal MHC class I molecules. Therefore, cross-presentation in dendritic cells occurs in a specialized, self-sufficient, ER-phagosome mix compartment.     

La relativité générale à l'étiage: 1925–1955

Sans résumé     

De l'influence de la gravitation sur la propagation de la lumière en théorie newtonienne. L'archéologie des trous noirs

Sans résumé Présenté par J. D. North     

Thrombocytes et thrombopathies

Summary Preliminary results of a statistical survey of electron micrographs of thrombocytes from 15 patients with haemorrhagic diathesis are reported. The possible significance of ultrastructural changes in relation to factor 3 activity and metabolism deficiency are discussed.