LiBr溶液从低浓度到高浓度的分子动力学模拟

在 L i Br与水的物质量比分别为 1∶ 64、1∶ 32、1∶ 16、1∶ 8、1∶ 4和 1∶ 3的情况下 ,对 L i Br溶液从低温到高温的分子动力学模拟进行了研究。随浓度增加 ,锂离子的水合数量呈减少趋势但同时又从 L i+- Br-接触离子对的数量增加中得到补偿 ,而 L i离子的第一配位壳层的配位数量保持不变。在高浓度 Li Br溶液中 ,Br- O之间的距离有所增加 ,Br-- O的径向分布的形状更趋于非对称 ,从而很好地确定了 Br离子水合壳层 L i+- Br-接触离子对可以在更稀的溶液中产生 ,但随浓度增加而增加。L i+- Br-距离明显短于溶液中 Li离子与 Br离子的离子半径之和 ,也短于 L i Br晶体中两者离子半径之和。高浓度溶液中水分子的结构几乎被破坏 ,水分子间的氢键明显增加 ,但没有消失。对 L i+、Br-和水的扩数系数计算值与实验值进行了比较     

Acidic polar compounds in petroleum: a new analytical methodology and applications as molecular migration indices

A new method for analysis of acidic polar compounds, is described and discussed. It allows the simultaneous quantification of carboxylic acids, phenols and carbazoles and combines accuracy with a short turnaround time, a requirement strictly necessary for industrial applications. Routinely use of this methodology (more than 50 applications in many different sedimentary basins) has supplied many important pieces of information about oil origin, maturity, biodegradation and, in particular, has allowed to define a molecular migration index (MMI), based on relative abundance of phenol and alkyl phenols. The combination of well-established geochemical tools focused on saturated and aromatic fractions (such as biomarkers, compound specific isotope ratio analysis, and GC fingerprinting) with this methodology results in the definition of an integrated interpretative sequence. This last enhances the quality of interpretations through cross-checks and permits a better exploitation of oil samples by using also their less explored fraction, i.e. the polar compounds. Application results of this methodology are only shortly mentioned in this paper, which is mainly focused on analytical aspects. The results will be more extensively discussed in a future publication.     

赤潮叉角藻18SrDNA和ITS区序列测定与分析

采用PCR及克隆测序的方法，对1998年引发渤海赤潮的叉角藻18SrRNAadldey DNAITS区（Internal Transcribed Spacer Regions)进行了序列测定与分析。并通过因特网从国际分子生物学数据库中获取甲藻另外15个种的18rDNA序列，以Tetrahymena corlissi作为类群，分别采用Neighbor-Joining和Fitch方法构建甲藻较为一致和可靠的进化树图，探讨具有高度多样性和在分类上争议较多的甲藻各类群之间的形态与分子进化关系。结果表明，Prorocentrum(有2个简单的壳板）出现得较早，而大多数多甲藻目（覆盖着多个壳板）、裸甲藻目（大多数不具壳板）和膝沟藻目的成员较晚出现。另外，对叉角藻ITS区的分析表明，ITS区为高变区，是良好的分子标记，可用于叉角藻快速鉴定的专一性核酸分子探针的研制。     

柳珊瑚分子系统发育学的研究进展

珊瑚分子系统发育学研究始于90年代初,用于柳珊瑚分子系统学研究的主要分子标记是线粒体DNA和核糖体RNA。本文在重点介绍了柳珊瑚种群遗传多样性和柳珊瑚种上阶元系统发育学两方面的研究进展和所取得研究成果的同时,也讨论了珊瑚虫纲的系统发生关系。最后在简单引述了柳珊瑚分子系统发育学同传统形态分类学方法之间关系的同时,也对柳珊瑚分子系统发育学今后的重点研究方向做了预测。     

A novel high-resolution small ion spectrometer to study ion nucleation of aerosols in ambient indoor and outdoor air

An electrically based ion spectrometer is described, capable of measuring particle sizes and mobilities from molecular ions (small ions) to aerosol particles across a size range of 0.4 to 30 nm in diameter. It consists of a single cylindrical capacitor divided into three electrically insulated sections. The current arriving at the central section is measured by an electrometer and represents the ion flux over a known range of mobilities determined by the applied voltage. The applied voltage is scanned in steps to measure the ion fluxes over a large number of overlapping mobility ranges. The recorded signal and the response function of the instrument are unfolded using a maximum entropy procedure to give a high-resolution measured mobility spectrum. The maximum entropy approach offers a considerable improvement over traditional aspiration collectors and can approach the resolution of a drift tube system. In this way, the spectrometer successfully overcomes the diffusion limit to small ion resolution. Illustrative spectra are shown, demonstrating for the first time the presence of some resolved structure within the small ion spectrum at the highest mobilities. It is demonstrated that the actual mobility spectrum of small ions falls in the range 0.8–2.0 × 10⁻⁴ m² V⁻¹ s⁻¹. This represents a narrower range than that previously measured which is attributed to improved spectral resolution in the present work.     

Total and pyrogenic carbon stocks in black spruce forest floors from eastern Canada

Pyrogenic carbon (PyC), a by-product of recurrent boreal wildfires, is an important component of the global soil C pool, although precise assessment of boreal PyC stock is scarce. The overall objective of this study was to estimate total C stock and PyC stock in forest floors of Eastern Canada boreal forests. We also investigated the environmental conditions controlling the stocks and characterized the composition of the forest floor layers. Forest floor samples were collected from mesic black spruce sites recently affected by fire (3–5 yr) and analyzed using elemental analysis and solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy. PyC content was further estimated using a molecular mixing model. Total C stock in forest floors averaged 5.7 ± 2.9 kg C/m² and PyC stock 0.6 ± 0.3 kg C/m². Total stock varied with position in the landscape, with a greater accumulation of organic material on northern aspects and lower slope positions. In addition, total stock was significantly higher in spruce-dominated forest floors than stands where jack pine was present. The PyC stock was significantly related to the atomic H/C ratio (R² 0.84) of the different organic layers. ¹³C NMR spectroscopy revealed a large increase in aromatic carbon in the deepest forest floor layer (humified H horizon) at the organic-mineral soil interface. The majority of the PyC stock was located in this horizon and had been formed during past high severity fires rather than during the most recent fire event.     

暗云L1211的C~（18）O（J＝1－0）分子发射谱线的观测

本文作者首次对暗云Ｌ１２１１的Ｃ~（１８）Ｏ（Ｊ＝１－０）分子发射谱线进行了观测，发现了暗云Ｌ１２１１致密核的Ｃ~（１８）Ｏ（Ｊ＝１－０）的宽翼发射谱线和它的结构，得到了核区Ｃ~（１８）Ｏ（Ｊ＝１－０）分子的谱线轮廓图、强度分布图、速度分段积分等高图、速度位置图。     

Aliphatic alkanes and polycyclic aromatic hydrocarbons in atmospheric PM10 aerosols from Baoji, China: Implications for coal burning

Normal alkanes and PAHs in atmospheric PM₁₀ aerosols collected during 2008 winter and spring in Baoji, a mid-scale inland city of China, were determined on a molecular level. Concentrations of n-alkanes ranged from 232 to 3583 ng/m³ with an average of 1733 ng/m³ in winter and from 124 to 1160 ng/m³ with an average of 449 ng/m³ in spring, while PAHs in the PM₁₀ samples were 594 ± 405 and 128 ± 82 ng/m³ in the two seasons. Molecular compositions showed that CPI (odd/even) values of n-alkanes were close to unity for all the samples especially in winter, and diagnostic ratios of PAHs (e.g., Phe/(Phe + Ant), CPAH/ΣPAHs and IcdP/(IcdP + BghiP)) were found similar to those in coal burning smoke with a strong linear relationship (R² ≥ 0.85) between PAHs and fossil fuel derived n-alkanes, demonstrating that coal burning is the main source of n-alkanes and PAHs in the city, especially in winter due to house heating. Concentrations of the determined compounds in Baoji are much higher than those in Chinese mega-cities, suggesting that air pollution in small cities in the country is more serious and need more attention.     

CaCO3生物矿化的研究进展——有机质的控制作用

生物CaCO₃是自然界分布最广泛的一类生物矿物,其组成除了无机相的CaCO₃外,还含有少量的有机质,包括水可溶(SM)和水不可溶有机质(IM),SM富含阴离子基团,是控制CaCO₃结晶的重要因素之一。通过有机—无机界面分子识别,有机质选择性地与CaCO₃晶体特定方向的面网相互作用,从而对CaCO₃的生长、形貌、多型及结晶学定向等产生明显的控制作用。有机—无机界面的分子识别机制包括静电、晶格几何匹配和立体化学互补等。仿生矿化的研究为进一步深入了解生物矿化的机理及制造高级复合材料提供了新的方法。     

Enzymatic release of amino acids from different humic substances

Humic substances isolated from water, sediment, and soil were characterized by applying elemental analysis, spectroscopic analysis, and gelchromatographic molecular size distribution. In addition, the amounts and pattern of enzymatically released amino acids were determined. Depending on the origin of the humic substances, the percentage of released amino acid nitrogen related to the total nitrogen was in the range of 0.4 to 26.7%. The samples particularly differed in the content of leucine und tyrosine. The total amount of released amino acids was compared with the results obtained from the other characterization methods. This approach indicated that humic substances with a high content of hydrolysable amino acids had high N/C and O/C ratios and low molecular sizes. Beside this, the absorption of these substances in the UV and visible wavelength range was quite low, while the measured ratios of SAK(254)/SAK(436) showed high values. This work leads to the conclusion that the extent of enzymatically releasable amino acids is not only dependant on the nitrogen content of humic substances. Other physical and chemical properties have to be considered for the understanding of the results obtained by the described biochemical characterization method.