Genome sequence of the radioresistant bacterium Deinococcus radiodurans R1

The complete genome sequence of the radiation-resistant bacterium Deinococcus radiodurans R1 is composed of two chromosomes (2,648,638 and 412,348 base pairs), a megaplasmid (177,466 base pairs), and a small plasmid (45,704 base pairs), yielding a total genome of 3,284, 156 base pairs. Multiple components distributed on the chromosomes and megaplasmid that contribute to the ability of D. radiodurans to survive under conditions of starvation, oxidative stress, and high amounts of DNA damage were identified. Deinococcus radiodurans represents an organism in which all systems for DNA repair, DNA damage export, desiccation and starvation recovery, and genetic redundancy are present in one cell.     

Conformationally controlled chemistry: excited-state dynamics dictate ground-state reaction

Ion imaging reveals distinct photodissociation dynamics for propanal cations initially prepared in either the cis or gauche conformation, even though these isomers differ only slightly in energy and face a small interconversion barrier. The product kinetic energy distributions for the hydrogen atom elimination channels are bimodal, and the two peaks are readily assigned to propanoyl cation or hydroxyallyl cation coproducts. Ab initio multiple spawning dynamical calculations suggest that distinct ultrafast dynamics in the excited state deposit each conformer in isolated regions of the ground-state potential energy surface, and, from these distinct regions, conformer interconversion does not effectively compete with dissociation.     

固结快剪条件下细粒土抗剪强度指标影响因素分析研究

在实际工程中细粒土有着广泛的应用,其抗剪强度指标受多种因素影响,变化复杂,不易准确确定。本文在实际调查的基础上,考虑了孔隙比、含水率、塑性指数等3种主要因素对抗剪强度指标的影响。在固结快剪的条件下,利用正交设计的方法优化试验方案进行细粒土抗剪强度指标影响因素的研究。根据试验结果,分析了抗剪强度指标对各因素的敏感性;并利用多元回归的方法建立了粘聚力和内摩擦角与孔隙比、塑性指数、含水率等3个因素的回归方程,为细粒土抗剪强度指标的合理确定提供了一定的理论支持。     

Monochromatic electron photoemission from diamondoid monolayers

We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low-kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flat-panel displays.     

Stability and structure of MgSiO3 perovskite to 2300-kilometer depth in Earth's mantle

Unexplained features have been observed seismically near the middle (approximately 1700-kilometer depth) and bottom of the Earth's lower mantle, and these could have important implications for the dynamics and evolution of the planet. (Mg,Fe)SiO3 perovskite is expected to be the dominant mineral in the deep mantle, but experimental results are discrepant regarding its stability and structure. Here we report in situ x-ray diffraction observations of (Mg,Fe)SiO3 perovskite at conditions (50 to 106 gigapascals, 1600 to 2400 kelvin) close to a mantle geotherm from three different starting materials, (Mg0.9Fe0.1)SiO enstatite, MgSiO3 glass, and an MgO+SiO2 mixture. Our results confirm the stability of (Mg,Fe)SiO3 perovskite to at least 2300-kilometer depth in the mantle. However, diffraction patterns above 83 gigapascals and 1700 kelvin (1900-kilometer depth) cannot presently rule out a possible transformation from Pbnm perovskite to one of three other possible perovskite structures with space group P2(1)/m, Pmmn, or P4(2)/nmc.     

秸秆处理技术的最新进展:挑战与解决方案

秸秆作为一种农业副产品已被认为是一种潜在生物质资源。然而,露天焚烧秸秆仍是世界许多地区的主要手段,这造成资源浪费和空气污染。近年来已经开发了许多用于从秸秆中回收能源和资源的技术,由于其经济可行性和生态友好性质,该生物学方法引起了越来越多的研究兴趣。然而,在生物加工过程之前对秸秆进行预处理是必不可少的,并且在很大程度上决定了过程的可行性、经济可行性和环境可持续性。因此,本综述试图对当前的秸秆预处理技术和管理实践进行重要而全面的分析。主要提出了结合微生物降解和酶促水解的综合生物过程,并阐述了其与未来大规模秸秆处理相关的潜在利益、局限性和挑战,并展望了前景和方向。     

对中专《家畜内科学》教材中某些问题的商榷

由云南省畜牧兽医学校沈俊杰同志主编的全国中等农业学校教材《家畜内科学》（第二版）,是在第一版的基础上,经过修订重新编写而成。对原书章节作了适当调整,对内容进行了修改和补充,删去了临床上不常见的疾病和国家已公布淘汰的兽用药品,并吸取了国内外的一些新的先进经验和技术。本书内容扼要,重点突出,叙述精练,反映了我国现代家畜内科学的水平。从目前情况来看,这是一本较好的全国通用《家畜内科学》中专教材。但我们在使用过程中,也发现了其中的某些不足,今冒昧提出,与全国同行的兽医教师商讨,其目的是为了不断提高兽医教…     

High prevalence of Toxoplasma gondii in a commercial flock of chickens in Israel, and public health implications of free-range farming

Little is known of the prevalence of Toxoplasma gondii in commercially raised chickens. In the present study, the prevalence of T. gondii in 96 free-range chickens (Gallus domesticus) from a commercial farm in Israel was assessed. Blood, heart, and brain from each chicken were examined for T. gondii infection. Antibodies to T. gondii, assayed with the modified agglutination test (MAT > or = 1:5), were found in 45 of the 96 chickens. Hearts and brains of seropositive (MAT > or = 1:5) chickens were bioassayed in mice. Additionally, hearts and brains of 51 seronegative (MAT < 1:5) chickens were bioassayed in two T. gondii-free cats. T. gondii was isolated from 19 of the 45 (42.2%) seropositive chickens by bioassay in mice. Both the cats fed tissues pooled from seronegative chickens shed T. gondii oocysts. Tachyzoites and tissue cysts of all 21 isolates of T. gondii from chickens were avirulent for mice. Seventeen of the 19 isolates genotyped were found to be type II, and 2 were type III. Understanding of the sources of infection on such farms could be the key to the development of better prevention strategies.