The yohkoh mission for high-energy solar physics

The Japanese Yohkoh satellite is now in orbit observing the sun with a set of x-ray imagers and x-ray and gamma-ray spectrometers. The data from this successful mission provide new information on solar flares and the sun's corona. This paper discusses the Yohkoh observations and presents a sample of the first scientific results from the mission.     

水稻抽穗期茎鞘中储存的可用性糖与籽粒充实的关系

用抽穗期茎鞘中可用性糖（可溶性糖＋淀粉）的累积量与颖花数之比，即糖花比表示灌浆始期每朵颖花具有的物质积累。一般抽穗期糖花比高的品种（组合），灌浆初期籽粒中的ＩＡＡ和ＡＴＰ含量、ＡＴＰ酶活性、谷粒充实率和千粒重亦高，它们之间呈极显著正相关。增加抽穗期的糖花比，灌浆初期的籽粒生理活性和谷粒充实率提高，抽穗期糖花比减小，结果则相反。表明抽穗期茎鞘中储存的可用性糖不仅是籽粒灌浆物质的一部分，而且对提高灌浆初期籽粒库的活性、启动和促进籽粒灌浆起重要作用。     

Imaging quasiparticle interference in Bi2Sr2CaCu2O8+delta

Scanning tunneling spectroscopy of the high-Tc superconductor Bi2Sr2CaCu2O8+delta reveals weak, incommensurate, spatial modulations in the tunneling conductance. Images of these energy-dependent modulations are Fourier analyzed to yield the dispersion of their wavevectors. Comparison of the dispersions with photoemission spectroscopy data indicates that quasiparticle interference, due to elastic scattering between characteristic regions of momentum-space, provides a consistent explanation for the conductance modulations, without appeal to another order parameter. These results refocus attention on quasiparticle scattering processes as potential explanations for other incommensurate phenomena in the cuprates. The momentum-resolved tunneling spectroscopy demonstrated here also provides a new technique with which to study quasiparticles in correlated materials.     

CD95/CD95 ligand interactions on epithelial cells in host defense to Pseudomonas aeruginosa

Pseudomonas aeruginosa causes severe infections, particularly of the lung, that are life threatening. Here, we show that P. aeruginosa infection induces apoptosis of lung epithelial cells by activation of the endogenous CD95/CD95 ligand system. Deficiency of CD95 or CD95 ligand on epithelial cells prevented apoptosis of lung epithelial cells in vivo as well as in vitro. The importance of CD95/CD95 ligand-mediated lung epithelial cell apoptosis was demonstrated by the rapid development of sepsis in CD95- or CD95 ligand-deficient mice, but not in normal mice, after P. aeruginosa infection.     

Translating biomolecular recognition into nanomechanics

We report the specific transduction, via surface stress changes, of DNA hybridization and receptor-ligand binding into a direct nanomechanical response of microfabricated cantilevers. Cantilevers in an array were functionalized with a selection of biomolecules. The differential deflection of the cantilevers was found to provide a true molecular recognition signal despite large nonspecific responses of individual cantilevers. Hybridization of complementary oligonucleotides shows that a single base mismatch between two 12-mer oligonucleotides is clearly detectable. Similar experiments on protein A-immunoglobulin interactions demonstrate the wide-ranging applicability of nanomechanical transduction to detect biomolecular recognition.     

A predator unmasked: life cycle of Bdellovibrio bacteriovorus from a genomic perspective

Predatory bacteria remain molecularly enigmatic, despite their presence in many microbial communities. Here we report the complete genome of Bdellovibrio bacteriovorus HD100, a predatory Gram-negative bacterium that invades and consumes other Gram-negative bacteria. Its surprisingly large genome shows no evidence of recent gene transfer from its prey. A plethora of paralogous gene families coding for enzymes, such as hydrolases and transporters, are used throughout the life cycle of B. bacteriovorus for prey entry, prey killing, and the uptake of complex molecules.     

Hepatic drug metabolism in rats: impairment in a dirty environment

Reduction of aniline hydroxylase activity, ethylmorphine N-dementhylase activity, and cytochrome P-450 content occurred in hepatic microsomes of rats kept under dirty conditions, defined as accumulation for 1 week of urine and feces in pans under the wire mesh cages. In comparison with rats that had urine and feces removed twice daily from such pans, rats kept over Kimpak bedding or over Litter Green, changed twice daily, also showed reduced drug-metabolizing activity in hepatic microsomes, but to a lesser degree than the dirty rats. Placement of a filter top on cages for 1 week also decreased drug-metabolizing activity. These experiments suggest that the relative cleanliness of an animal's environment can influence hepatic microsomal drug metabolism.     

9个苹果新品种在榆林南部丘陵沟壑区的引种表现

为进一步筛选适宜榆林南部丘陵沟壑区栽植的优质苹果新品种,试验以长富2号为对照,通过对烟富系列、响富、瑞阳、瑞雪、维纳斯·黄金、秦脆、玉华早富等9个中晚熟苹果品种的主要性状进行观察记录,并对其进行分析研究。结果表明：烟富10、烟富6、响富、秦脆四个中晚熟红色品种和维纳斯·黄金、瑞雪两个晚熟黄色品种适宜于榆林南部丘陵沟壑区栽植。     

磁性液体光透射变化的场致开关效应

通过研究磁性液体在平行于激光照射方向具有不同梯度的外磁场作用下,其光透射率随时间的变化情况,进一步研究了其在平行于光方向磁场作用下的开关效应,并从理论上定性地分析了导致这种现象的内在因素,讨论了微粒链的形成以及链在磁性液体内部的微观运动情况.