Molecular characterisation of vitrinite in relation to natural hydrogen enrichment and depositional environment     

M. J. Iglesias  A. Jimnez  J. C. del Río  I. Surez-Ruiz 《Organic Geochemistry》2000,31(12)

The Py-GC/MS results of the study carried out on two groups of vitrinites (perhydrous and non-perhydrous) of different age and properties and on a trimaceralic coal associated with one of the perhydrous group are discussed. Such a study provides information about the effect of natural hydrogen enrichment on vitrinite structure at the molecular level. Moreover, the influence of the different conditions in the sedimentary environment on the chemical structure of the vitrinite is also discussed. This influence is inferred through differences in the distribution and relative amount of phenolic compounds found in the pyrolysates from two samples of two different coal-beds in the same basin but formed under different paleoenvironmental conditions. For vitrinites with a high H/C atomic ratio, despite having a strong perhydrous character, their pyrolysates exhibit the highly phenolic signature typical of lignin-derived material with only minor aliphatic compounds. Thus, the major chemical structural elements in these vitrinites are simple phenols with a high contribution of para alkyl-substituted derivatives. However, there is no parallel relationship between the evolution of the oxygenated functionalities and the reflectance values. From the results obtained a coalification pathway where hydrogenation processes predominate over thermal ones is proposed. The presence of resin-like substances and/or oils (which are two of the causes of natural hydrogen enrichment) in the molecular structure of vitrinites have, therefore, affected the normal evolution of the lignin and contributed to the special properties of this type of materials.  相似文献   

Molecular dynamics study of pressure-induced transformation of quartz-type GeO2     

T. Tsuchiya  T. Yamanaka  M. Matsui 《Physics and Chemistry of Minerals》2000,27(3):149-155

We simulated quartz-type GeO₂ and investigated its high-pressure transformation using the molecular dynamics (MD) simulation method with a model potential. The calculated results under hydrostatic compression indicated that a pressure-induced amorphization of quartz-type GeO₂ originated from the mechanical instability of the quartz lattice as, in previous theoretical studies of SiO₂. Furthermore, quartz-type GeO₂ directly transformed to a rutile-like structure with only subtle displacements of ions under σ _{x y} imposed shear stressed decompression. This is the first reproduction of the quartz-to-rutile transformation. A possible pathway of this transition is proposed in this study. Received: 14 April 1999 / Revised, accepted: 11 August 1999  相似文献   

基于线粒体CO1基因的DNA条形码在石首鱼科(Sciaenidae)鱼类系统分类中的应用   总被引：7，自引：1，他引：7  

柳淑芳  陈亮亮  戴芳群  庄志猛 《海洋与湖沼》2010,41(2):223-232

采用CO1基因特异扩增测序及与GenBank已有序列联配分析的方法,进行了石首鱼科19属30种鱼类75个CO1基因片段的序列比较和系统进化研究,结果表明,石首鱼科鱼类该片段的平均GC含量为48.3%,其中第2密码子位点含量最高(51%-58.4%,平均56.6%),第1密码子变化范围最大(27.6%-54.1%,平均44.9%),第3密码子差别较小(41.6%-43.6%,平均42.7%)。依据Kimura-2-parameter模型,30种石首鱼科鱼类种内遗传距离平均值为0.006,种间为0.210,种间遗传距离是种内的35倍;在分子系统树上,28个种(93.3%)可形成单系,18个属(94.7%)可聚为独立的分支;与形态学分类不同的是,由黑鳃梅童鱼(Collichthys lucidus)与棘头梅童鱼(C.niveatus)的遗传距离(0.004)推断二者遗传变异尚未达到种的分化水平,灰鳍彭纳石首鱼(Pennahia anea)与白姑鱼(Argyrosomus argentatus)的形态学特征相似性和条形码序列同源性都提示二者可能为同种异名,而红牙(Otolithes ruber)印度洋和南海两个地理群体间的遗传分化已经达到种的水平。本研究证明线粒体CO1基因可作为DNA条形码对石首鱼科鱼类进行有效的物种鉴定,亦可用于探讨石首鱼科的属、种分类单元系统发育问题。  相似文献   

The massive hot core associated with G31.41+0.31     

C. M. Walmsley  R. Cesaroni  L. Olmi  E. Churchwell  P. Hofner 《Astrophysics and Space Science》1995,224(1-2):173-175

We have used the IRAM Plateau de Bure Interferometer to observe the ground state and vibrationally excited lines of Methyl Cyanide towards the UCHII region G31.41+0.31. We also obtained a map of the continuum emission at a frequency of 110 GHz. We detect a hot molecular core in the emission both of methyl cyanide and of the 110 GHz continuum. We estimate a temperature of 200 K and a mass of 1000 M for this compact massive region. We also detect a velocity gradient or shift across the methyl cyanide core whose origin could be due to rotation.  相似文献   

无机材料在海洋药物分离分析中的应用     

张宇  谭振东  马亚鲁 《海洋技术学报》2007,26(3):81-84

综述了无机材料在海洋天然活性物质分离、分析中的应用,从材料的设计、分离机制、制备方法、表面的改性等方面初步的探讨了无机材料在活性物质分离、分析的应用前景和存在的问题。文中还介绍了一门新兴分离技术即分子印迹技术,它在分子识别中有着特殊的选择性。鉴于大孔树脂吸附技术的大规模应用和分离高效性,提出了我课题组正在研制的多孔陶瓷微球的应用背景和取得的工作成果。  相似文献   

海带浸泡液腐植质的分离及其性质     

纪明侯  张鸿声 《海洋与湖沼》1992,23(3):302-311

对海带综合利用生产中剩下的浓缩浸泡液所含腐植质进行了分离,并对分离出的腐植酸、富里酸和乙醇可溶物三级分做了化学表征和性质研究,包括三级分的得率、紫外和红外光谱分析,元素、官能团、氨基酸和总糖含量分析,分子量分布,以及它们对鱼卵生长和褐藻酸钠粘度的影响。  相似文献   

Levels and distributions of organic source tracers in air and roadside dust particles of Kuala Lumpur,Malaysia     

Nasr Yousef M. J. Omar  M. Radzi Bin Abas  Noorsaadah A. Rahman  Norhayati Mohd. Tahir  Ahmed I. Rushdi  Bernd R. T. Simoneit 《Environmental Geology》2007,52(8):1485-1500

The concentrations of n-alkanes, unresolved complex mixture (UCM), petroleum molecular markers, other tracers of cooking and burning emissions, and natural background in atmospheric particles and roadside dust particles were measured at eight locations in the city center and the suburbs of Kuala Lumpur, Malaysia. Atmospheric particles were collected using high-volume filtration (PM-10, GFF) over 24 h average periods. Road dusts were swept up, dried and sieved. Both types of samples were extracted with dichloromethane/methanol mixture (3:1 v/v) by ultrasonic agitation. The extracts were then fractionated by column chromatography and the alkanes subjected to gas chromatography–mass spectrometry (GC–MS). Total extracts were also analyzed directly by GC–MS after silylation. The molecular distributions of compounds as well as diagnostic geochemical ratios were determined in order to identify the sources of the organic compounds. Samples collected from a rural area and lubricating oils were also analyzed for comparisons. Anthropogenic and biogenic sources such as vehicular emissions, waxes of higher plants, food cooking operations, and biomass and domestic refuse burning processes contributed to the organic matter content of atmospheric and to lesser extent, roadside dust particles.  相似文献   

NaAlSi3O8熔体粒子扩散行为压力效应的分子动力学研究     

赵亚娟张毅刚  郭光军KeithREFSON 《岩石学报》2004,20(6):1461-1468

为了研究压力对钠长石成分熔体粒子微观扩散行为的影响，本文用分子动力学方法，探讨了2001．5K温度下，压力由50MPa上升到19862MPa的过程中，熔体的微观结构、粒子自扩散系数随压力的变化规律。研究表明，在升压过程中，低次配位体Al和Si向5次和6次配位体转变，Al的含量在15GPa达到极大值，而Si含量的极大值在20GPa仍未出现。Na的自扩散系数随压力升高单调下降，Al、Si和O的自扩散系数随压力升高先增后减，在8～10GPa左右达到极大值。网架形成粒子自扩散系数的极大值与Al和Si含量的极大值对应的压力点不一致。所有粒子的自扩散系数与它们与O之间键的寿命呈线性负相关。  相似文献   

The physical conditions in the BHR71 outflows     

Bérengère Parise  Arnaud Belloche  Silvia Leurini  Peter Schilke 《Astrophysics and Space Science》2008,313(1-3):73-76

Highly-collimated outflows are believed to be the earliest stage in outflow evolution, so their study is essential for understanding the processes driving outflows. The BHR71 Bok globule is known to harbour such a highly-collimated outflow, which is powered by a protostar belonging to a protobinary system. Using the APEX telescope on Chajnantor, we mapped the BHR71 highly-collimated outflow in CO(3-2), and observed several bright points of the outflow in the molecular transitions CO(4-3), CO(7-6), ¹³CO(3-2), C¹⁸O(3-2), CH₃OH(7-6) and H₂CO(4-3). We use an LVG code to characterise the temperature enhancements in these regions. These observations are particularly interesting for investigating the interaction of collimated outflows with the ambient molecular cloud. In our CO(3-2) map, the second outflow driven by IRS2, which is the second source of the binary system, is completely revealed and shown to be bipolar. We also measure temperature enhancements in the lobes. The CO and methanol LVG modelling points to temperatures between 30 and 50 K in the two lobes. The methanol emission in the southern lobe bright knot is barely resolved with the APEX single-dish. ALMA will thus be a central tool to study the shock chemistry in these regions.  相似文献   

Molecular clouds and star formation in the Magellanic Clouds and the Milky Way     

Akiko Kawamura 《Astrophysics and Space Science》2008,313(1-3):145-151

Star formation is a fundamental process that dominates the life-cycle of various matters in galaxies: Stars are formed in molecular clouds, and the formed stars often affect the surrounding materials strongly via their UV photons, stellar winds, and supernova explosions. It is therefore revealing the distribution and properties of molecular gas in a galaxy is crucial to investigate the star formation history and galaxy evolution. Recent progress in developing millimeter and sub-millimeter wave receiver systems has enabled us to rapidly increase our knowledge on molecular clouds. In this proceedings, the recent results from the surveys of the molecular clouds in the Milky Way and the Magellanic Clouds as well as the Galactic center as the most active regions in the Milky Way are presented. The high sensitivity with unrivaled high resolution of ALMA will play a key role in detecting denser gas that is tightly connected to star formation.  相似文献