New species and new records of North America Pityophthorus (Coleoptera: Scolytidae), Part VI. The Lautus group

Four new species of Mexican Pityophthorus in the Lautus group are described: P. indefessus (Jalisco), P. inhabilis (Guerrero), P. tutulus (Veracruz), and P. vegrandis (Quintana Roo) and a new locality record is given for P. corruptus Wood.     

X-ray structures of two oxidation states of a flavin-nicotinamide biscoenzyme and models for flavin--nicotinamide interactions.

The flavin nicotinamide biscoenzymes Flox(-)--C3--Nic+ and H2Flred--C3--Nic+ assume extended conformations in the solid state. In both derivatives the nicotinamide and flavin groups associate through hydrogen bonding. The bending angle of the reduced flavin moiety is less than half that in any previously reported 1,5-dihydroflavin structure. This effect is apparently due to ring stacking interactions.     

New species and new records of North American Pityophthorus (Coleoptera: Scolytidae), Part V: the Juglandis group

Six new species of Pityophthorus from Mexico are described. The new species, all in the Scriptor group, are: atkinsoni, diminutivus, equihuai, thamnus, trunculus and zexmenivora . An additional locality record for P. coronarius Blackman is included. A new key to the 22 species included in the Scriptor group is presented.         

轿车车门断面设计的原则和方法

介绍了轿车车门断面设计的基本方法,探讨了控制断面的作用和设置原则．结合车门间隙、车门密封、车门运动校核及车门结构件连接等具体设计过程,分析了车门断面设计中需要考虑的控制要素,阐述了轿车车门断面设计的基本思路和程序．     

拯救动物刻不容缓

物种的衰降及灭绝一直是自然界生物进化的组成部分之一，它体现了优胜劣汰的物竞天择自然规律。但现今的物种灭绝除自然界生物进化因素以外，人类异常干扰因素更堪称是"杀手"、"'元凶"。通过检测海洋无脊椎动物化石样品表明，自然界的物种灭绝现象已持续发生演绎了数百万年之久，每年约有1－3种物种速灭绝厄运。但现今状况则令人颇为吃惊，据科学测算，现今自然界物种的灭绝率为1000种／年以上，占纯天然性物种灭绝率指数的1000倍，这还仅是一种保守估算所得值（按最低保守数估算所得值）。像距今6500万年以前的恐龙遭厄运那样，人类目前已…     

New species and records of North American Pityophthorus (Coleoptera: Scolytidae), Part IV: the Scriptor group

Six new species of Pityophthorus from Mexico are described. The new species, all in the Scriptor group, are: atkinsoni, diminutivus, equihuai, thamnus, trunculus and zexmenivora . An additional locality record for P. coronarius Blackman is included. A new key to the 22 species included in the Scriptor group is presented.         

Horizontal endosymbiont transmission in hydrothermal vent tubeworms

Transmission of obligate bacterial symbionts between generations is vital for the survival of the host. Although the larvae of certain hydrothermal vent tubeworms (Vestimentifera, Siboglinidae) are symbiont-free and possess a transient digestive system, these structures are lost during development, resulting in adult animals that are nutritionally dependent on their bacterial symbionts. Thus, each generation of tubeworms must be newly colonized with its specific symbiont. Here we present a model for tubeworm symbiont acquisition and the development of the symbiont-housing organ, the trophosome. Our data indicate that the bacterial symbionts colonize the developing tube of the settled larvae and enter the host through the skin, a process that continues through the early juvenile stages during which the trophosome is established from mesodermal tissue. In later juvenile stages we observed massive apoptosis of host epidermis, muscles and undifferentiated mesodermal tissue, which was coincident with the cessation of the colonization process. Characterizing the symbiont transmission process in this finely tuned mutualistic symbiosis provides another model of symbiont acquisition and additional insights into underlying mechanisms common to both pathogenic infections and beneficial host-symbiont interactions.     

Products of the major histocompatibility complex and their relationship to the immune response.

The genes of the major histocompatibility complex were first known for the part they played in transplant rejection. Recently, however, it has become clear that the products of that region have an important part to play in the control of the immune response, through their effects both on cooperative and on aggressive interactions between cells. It is now possible to guess at the mechanisms which may underly the association of some major histocompatibility antigens with disease.