吸附制冷系统中吸附床的传热传质分析及结构设计

对化学吸附制冷系统中吸附剂颗粒之间以及整个吸附床的传热传质特性进行了分析，并总结了目前国内外强化吸附床传热传质性能的主要措施和方法．分析比较了两种用于化学吸附制冷的典型吸附床结构，在此基础上设计了一种新型的吸附床．     

肌肉自发振动过程中结合几率与化学反应速率的变化

定量分析肌球蛋白与肌动蛋白丝的结合几率及相关化学反应的速率常数,对于准确掌握肌肉收缩的内在机制具有非常重要的意义.以肌肉自发振动的实验结果为依据,从振动过程所满足的动力学方程出发,推导出结合几率与肌丝滑行速度及肌节长度之间的定量关系,并求得化学反应速率随肌肉收缩的速度变化而改变的数学规律.结果显示,结合几率的基准值由溶液中主要化学成分的浓度决定;结合几率的变化值与肌肉收缩的速度成正比,与肌节长度成反比;而化学反应速率随收缩速度按指数规律变化.上述结果与实验值基本一致.     

DNA deletions and clonal mutations drive premature aging in mitochondrial mutator mice

Mitochondrial DNA (mtDNA) mutations are thought to have a causal role in many age-related pathologies. Here we identify mtDNA deletions as a driving force behind the premature aging phenotype of mitochondrial mutator mice, and provide evidence for a homology-directed DNA repair mechanism in mitochondria that is directly linked to the formation of mtDNA deletions. In addition, our results demonstrate that the rate at which mtDNA mutations reach phenotypic expression differs markedly among tissues, which may be an important factor in determining the tolerance of a tissue to random mitochondrial mutagenesis.     

Magnification of light from many distant quasars by gravitational lenses

Exceptionally bright quasars with redshifts up to z = 6.28 have recently been discovered. Quasars are thought to be powered by the accretion of gas onto supermassive black holes at the centres of galaxies. Their maximum (Eddington) luminosity depends on the mass of the black hole, and the brighter quasars are inferred to have black holes with masses of more than a few billion solar masses. The existence of such massive black holes poses a challenge to models for the formation of structures in the early Universe, as it requires their formation within one billion years of the Big Bang. Here we show that up to one-third of known quasars with z approximately equal to 6 will have had their observed flux magnified by a factor of ten or more, as a consequence of gravitational lensing by galaxies along the line of sight. The inferred abundance of quasar host galaxies, as well as the luminosity density provided by the quasars, has therefore been substantially overestimated.     

Spectral signature of cosmological infall of gas around the first quasars

Recent observations have shown that, only a billion years after the Big Bang, the Universe was already lit up by bright quasars fuelled by the infall of gas onto supermassive black holes. The masses of these early black holes are inferred from their luminosities to be >10(9) solar masses (M(O)), which is a difficult theoretical challenge to explain. Like nearby quasars, the early objects could have formed in the central cores of massive host galaxies. The formation of these hosts could be explained if, like local large galaxies, they were assembled gravitationally inside massive (> 10(12) M(O)) haloes of dark matter. There has hitherto been no observational evidence for the presence of these massive hosts or their surrounding haloes. Here we show that the cosmic gas surrounding each halo must respond to its strong gravitational pull, where absorption by the infalling hydrogen produces a distinct spectral signature. That signature can be seen in recent data.     

The formation of the first low-mass stars from gas with low carbon and oxygen abundances

The first stars in the Universe are predicted to have been much more massive than the Sun. Gravitational condensation, accompanied by cooling of the primordial gas via molecular hydrogen, yields a minimum fragmentation scale of a few hundred solar masses. Numerical simulations indicate that once a gas clump acquires this mass it undergoes a slow, quasi-hydrostatic contraction without further fragmentation; lower-mass stars cannot form. Here we show that as soon as the primordial gas--left over from the Big Bang--is enriched by elements ejected from supernovae to a carbon or oxygen abundance as small as approximately 0.01-0.1 per cent of that found in the Sun, cooling by singly ionized carbon or neutral oxygen can lead to the formation of low-mass stars by allowing cloud fragmentation to smaller clumps. This mechanism naturally accommodates the recent discovery of solar-mass stars with unusually low iron abundances (10(-5.3) solar) but with relatively high (10(-1.3) solar) carbon abundance. The critical abundances that we derive can be used to identify those metal-poor stars in our Galaxy with elemental patterns imprinted by the first supernovae. We also find that the minimum stellar mass at early epochs is partially regulated by the temperature of the cosmic microwave background.     

青海省唐古特铁线莲指纹图谱的构建

[目的]建立青海省唐古特铁线莲中齐墩果酸成分HPLC指纹图谱,为其质量控制提供方法学依据.[方法]采用HPLC法建立唐古特铁线莲中齐墩果酸指纹图谱,标示其共有峰与特征峰,进行相似度评价.[结果]通过对10批唐古特铁线莲药材的测定,标定15个共有峰和12个非共有峰,建立了测试样品的HPLC指纹图谱.[结论]该方法准确、稳定、可靠,可用于唐古特铁线莲的质量研究和评价.