Isotopic analyses of nitrogenous compounds from the Murchison meteorite: ammonia, amines, amino acids, and polar hydrocarbons

The combined volatile bases (ammonia, aliphatic amines, and possibly other bases), ammonia, amino acids, and polar hydrocarbons were prepared from the Murchison meteorite for isotopic analyses. The volatile bases were obtained by cryogenic transfer after acid-hydrolysis of a hot-water extract and analyzed by combined gas chromatography-mass spectrometry of pentafluoropropionyl derivatives. The aliphatic amines present in this preparation comprise a mixture that includes both primary and secondary isomers through C5 at a total concentration of > or = 100 nmoles g-1. As commonly observed for meteoritic organic compounds, almost all isomers through C5 are present, and the concentrations within homologous series decrease with increasing chain length. Ammonia was chromatographically separated from the other volatile bases and found at a concentration of 1.1-1.3 micromoles g-1 meteorite. The ammonia analyzed includes contributions from ammonium salts and the hydrolysis of extractable organic compounds, e.g., carboxamides. Stable isotope analyses showed the volatile bases to be substantially enriched in the heavier isotopes, relative to comparable terrestrial compounds delta D < or = +1221%; delta 13C = +22%; delta 15N = +93%). Ammonia, per se, was found to have a somewhat lower delta 15N value (+69%) than the total volatile bases; consequently, a higher delta 15N (>93%) can be inferred for the other bases, which include the amines. Solvent-extractable polar hydrocarbons obtained separately were found to be enriched in 15N (delta 15N = +104%). Total amino acids, prepared from a hydrolyzed hot-water extract by cation exchange chromatography, gave a delta 15N of +94%, a value in good agreement with that obtained previously. Nitrogen isotopic data are also given for amino acid fractions separated chromatographically. The delta 15N values of the Murchison soluble organic compounds analyzed to date fall within a rather narrow range (delta 15N = +94 +/- 8%), an observation consistent with their formation, or formation of their precursors, by interstellar chemistry.     

星系形态分类的研究进展

传统的哈勃星系形态分类法可以很好地对近邻的亮星系进行分类,但对低面亮度星系、矮椭球星系、矮旋涡星系以及高红移星系等都已无能为力。德沃古勒分类系统、叶凯士分类系统和范登伯分类系统是在哈勃分类法的基础上进行了发展和细化,利用光的中心聚集度或光度级等作为星系形态分类的参数。模型化分类系统试图定量地测量星系形态参数,但需要假定星系面亮度分布满足一定的形式,如r~(1/4)律、指数律等。最近几年,又有一些学者提出了非模型化分类系统,给出了若干个可以直接测量星系形态的结构参数,如:聚集度指数C、非对称指数A、簇聚指数S、基尼系数G及矩指数M_(20)。这些参数可以反映星系的形成历史、恒星形成、与其他星系的相互作用、已经发生或正在进行的并合活动等。它们不仅可以有效地给出近邻星系的分类特性,还能用于测量高红移星系的形态。该文介绍了不同的星系形态分类方法,比较了各类方法的优点和不足。在此基础上,最后介绍了基于非模型化分类系统的星系形态分类的研究进展。     

地方病高发区成井用胶质水泥浆的试验研究

通过地方病高发区成井用胶质水泥浆的试验研究，以普通水泥和膨润土为基本材料，同时添加改善材料性能的外加剂，研制了一种用于高砷、高氟、高矿化度地区水井成井的止水材料，具有流动性好、抗渗性高、不收缩、完全无毒、价格低廉等特点，特别是其高抗渗性和不收缩性非常适合地方病区成井时隔离劣质含水层，保证优质含水层与劣质含水层互不串通、不渗漏、不污染。     

日冕电子加速的诊断—多频射电高时间分辨率观测结果

一个太阳耀斑约含数千个微耀斑［１］，每个微耀斑以热的，低频波和加速粒子的形式释放能量。耀斑期间大部分能量的释放是通过电子加速转移的结果，然而电子加速是在耀斑前相开始，并在整个耀斑持续期间继续保持。在耀斑发展的不同相期间伴有各种各样的射电辐射现象（及其它波段共生现象），多波段射电观测和比较可以给出有关电子加速过程和耀斑自身发展的重要信息，尤其可检测加速开始的时间和频率部位（目前仍为太阳物理的前沿）。微耀斑能量的瞬时释放可能是引起不同类型快速精细结构的原因，射电毫秒级尖峰辐射是起因于连续能量释放的证据，其辐射源位于或靠近能量释放区［２］，公认射电辐射的快速结构是日冕电子束的特征信号［３，４］，所以今后使用高时间和高频率分辨率的宽带频谱仪同时观测可详细地探测加速过程，从而对预耀斑的加热和初始能量释放，耀斑的逐步建立和演化都具有重要意义。本文介绍几个典型事件，包括射电尖峰脉冲辐射，类尖峰辐射和短时标漂移结构     

Far-infrared Detection of C3 in Sagittarius B2 and IRC +10216

We report on the detection of nine lines of the nu2 bending mode of triatomic carbon, C3, in the direction of Sagittarius B2. The R(4) and R(2) lines of C3 have been also detected in the carbon-rich star IRC +10216. The abundances of C3 in the direction of Sgr B2 and IRC +10216 are approximately 3x10-8 and approximately 10-6, respectively. In Sgr B2 we have also detected the 23-12 line of NH with an abundance of a few times 10-9. Polyatomic molecules will have a weak contribution from their pure rotational spectrum to the emission/absorption in the far-infrared. We suggest, however, that they could be, through their low-lying vibrational bending modes, the dominant carriers of emission/absorption in the spectrum of bright far-infrared sources.     

Small-scale Gradients and Large-scale Diffusion of Charged Particles in the Heliospheric Magnetic Field

We present a simple spin-evolution model that predicts that rapidly rotating accreting neutron stars will be confined mainly to a narrow range of spin frequencies: P=1.5-5 ms. This is in agreement with current observations of neutron stars in both the low-mass X-ray binaries and the millisecond radio pulsars. The main ingredients in the model are (1) the instability of r-modes above a critical spin rate, (2) the thermal runaway that is due to the heat released as viscous damping mechanisms counteract the r-mode growth, and (3) a revised estimate of the strength of the dissipation that is due to the presence of a viscous boundary layer at the base of the crust in an old and relatively cold neutron star. We discuss the gravitational waves that are radiated during the brief r-mode-driven spin-down phase. We also briefly touch on how the new estimates affect the predicted initial spin periods of hot young neutron stars.