Review of the methods used for isolating pharmaceutical lead compounds from traditional medicinal plants

The possibility of finding new medicines from natural sources is one of the more commonly cited reasons for preserving biodiversity, and employing indigenous knowledge of traditional healing remedies greatly increases the likelihood of discovering these hidden medicinal compounds. The main difficulties in using natural products as a source for pharmaceutical lead compounds involve separating the plethora of compounds from the original extract, as well as the gamble of time and money invested in an activity that may not yield a novel compound. However, while these difficulties exist, the potential of natural products still far outweighs the limitations of the simple structures and known modes of action of synthetic lead compounds. As such, the production of novel medicines, particularly for cancer and human immunodeficiency virus (HIV) treatments as well as the inhibition of antibiotic-resistant bacteria, now requires the utilization of natural products. This paper provides a review of the current methods used in elucidating pharmaceutical lead compounds from natural sources, focusing on plant samples in particular.     

发动机的绿色化学设计

发动机绿色化学设计以发动机化学设计概念和发动机化学反应器模型为基础,旨在实现发动机材料选择、能源利用和环境效应之间的最佳综合效益．发动机燃料系统绿色化学设计的范畴包括：汽油无铅化与汽油抗磨性,柴油低硫化与柴油润滑性,生态燃料与生态摩擦学,汽油机沉积物与汽油清净剂,柴油机颗粒（碳烟）与消烟助燃剂． 发动机润滑系统绿色化学设计的范畴包括：润滑油和添加剂与排放催化转化,润滑剂生物降解性与生物降解润滑剂,润滑油使用与质量监控． 发动机燃料／润滑系统材料绿色化学设计的范畴包括：催化助燃／补燃作用,低散热发动机高温润滑,发动机机械与化学材料制造． 发动机绿色效应的实现取决于发动机诸系统绿色化学设计问题的解决程度．     

大气化学模式的数值计算方法

大气化学模式计算的一个重要研究热点是如何快速精确地对相互关联的非线性常微分方程组(ODES)进行数值积分求解。由于大气中各物种寿命长短相差很大,导致ODE_s具有了很强的刚性,因而在数值求算过程中存在着计算精度和计算效率的平衡问题。笔者介绍了当前几种常见的大气化学模式的计算方法,包括GEAR,QSSA(MQSSA),Y&B(MY&B),RADM,LSODE,SMVGEAR,小参数法,Gong and Cho及TWOSTEP等,并结合当前本领域内的部分研究成果对一些重要的方法进行了比较和分析。      

喜马拉雅山中段北坡对流层中上部大气降水化学的高程分布特征

1997年夏季在希夏邦马峰北坡达索普冰川区(28°33′N,85°44′E)海拔5800m～7000m区间对4次降雪过程进行了系统的采样工作,目的是认识全球偏远地区对流层中上部大气成分的高程分布特征.达索普冰川区夏季4次降水中,局地大陆性气团降水SO₄^2-、NO₃^-、Ca²⁺和Mg²⁺之间存在显著的正相关性,而海洋性气团降水4种离子之间的相关性变化较大,说明在夏季低尘埃阶段大气中各种离子的主导来源处在短期的(如数天)变化中.这种离子主导来源的变化同时也影响了降水中离子的高程分布特征.总体上达索普冰川区夏季降水中NO₃^-、Ca²⁺、Mg²⁺浓度随海拔的升高呈减小趋势,SO₄^2-浓度则为增大趋势.     

Spatial patterns of tungsten and cobalt in surface dust of Fallon,Nevada

Spatial patterns of tungsten and cobalt are described for surface dust of Fallon, Nevada, where a cluster of childhood leukemia has been ongoing since 1997. In earlier research, airborne tungsten and cobalt was shown to be elevated in total suspended particulates in Fallon. To fine-tune the spatial patterns of tungsten and cobalt deposition in Fallon, surface dust was collected in a grid pattern within as well as outside of Fallon to establish background concentrations of metals. In surface dust, tungsten and cobalt show sharp peaks (934 ppm and 98 ppm, respectively) within Fallon just north of highway 50 and west of highway 95. These two peaks overlap spatially, and given the grid pattern used for collecting surface dust, the source area of these two airborne metals can be pinpointed to the vicinity of hard-metal industry located north of highway 50 and west of highway 95. Fallon is distinctive in west central Nevada because of high airborne tungsten and cobalt particulates, and given its cluster of childhood leukemia, it stands to reason that additional biomedical research is in order to test directly the leukogenicity of combined airborne tungsten and cobalt particulates.     

Ca~(2+)对煤中含氮活性基团阻化效应研究

为揭示CaCl2抑制煤炭自燃发生的机理,提高阻化效果,采用Gaussian03软件包,对Ca2+与煤中含N活性基团形成的配位体的结构及分子前沿轨道、稳定化能、自然键轨道和净电荷布居、电荷转移进行系统研究。结果表明,Ca2+能够与煤中含N活性基团形成二配体、三配体及四配体配合物,形成四配体的稳定化能与前沿轨道能级能隙差较大,说明四配体配合物最为稳定,而且形成配合物后,煤含N活性结构中的-NH2基团对前沿轨道的贡献大大减少,同时轨道能级大幅增加,增加了煤活性结构的稳定性,提高了煤活性结构的抗氧化性。     

Glacier Variability (1967‐2006) in the Teton Range,Wyoming, United States1

Edmunds, Jake, Glenn Tootle, Greg Kerr, Ramesh Sivanpillai, and Larry Pochop, 2011. Glacier Variability (1967‐2006) in the Teton Range, Wyoming, United States. Journal of the American Water Resources Association (JAWRA) 48(1): 187‐196. DOI: 10.1111/j.1752‐1688.2011.00607.x Abstract: Glacier area and volume changes were quantified through the use of historical aerial photographs in Wyoming’s Teton Range. Glacier area changes in the Teton Range were estimated for three glaciers using unrectified aerial photography from 1967 to 2006. The total surface area of the three glaciers was 0.53 km² in 1967 and 0.40 km² in 2006, a decrease of 25% during the 39‐year period. The smallest glacier, Teepe, experienced the greatest area loss (60 ± 3%), whereas the largest glacier, Teton Glacier, lost 17 ± 3% of the 1967 area. For the current research, aerial photography from 1967 to 2002 was used to estimate glacier volume loss using stereoscopy techniques. The aerial photographs provide a finer resolution when compared with other datasets including satellite imagery (e.g., Landsat). Volume loss for the three glaciers was estimated to be 3.20 ± 0.46 million cubic meters over the period of 1967 to 2002. In assessing the primary climatic driver of the glacier ice loss, observed summer (June, July, and August) temperature data showed a statistically significant increase in temperatures when comparing the period of study (1968 to 2006) with historical temperatures from 1911 to 1967. When comparing spring (April 1st Snow Water Equivalent) snowpack for the period of study with historical records beginning in 1931, a significant difference in snowpack was not observed.     

三种铜缓蚀剂抗H2S腐蚀性能研究

研究了BTA,MBI,MBT等3种铜缓蚀剂在H2S环境中的缓蚀性能,采用量子化学研究方法对实验结果进行了分析,研究了苯三唑在铜表面所形成的配合物保护膜的稳定性。结果表明,MBT抗H2S腐蚀性能较差,BTA是铜及其合金在H2S环境中理想的接触缓蚀剂和气相缓蚀剂。     

雅鲁藏布江河水氢氧同位素时空变化特征

为揭示流域内水汽循环过程变化规律、揭示河水稳定同位素与气象要素及海拔之间的关系,2018年先后采集雅鲁藏布江干流丰、平、枯,水期水样90个,对河水的氢氧同位素组成进行了分析.结果表明：利用δ¹⁸O与纬度和海拔定量关系模型研究了雅江流域降水氢氧同位素空间变化特征,发现降水中δ¹⁸O值变化呈现东西部（雅江上、下游）高中部（雅江中游）低的趋势;建立了雅江丰、平、枯水期河水氢氧同位素方程,研究发现δD与δ¹⁸O的线性方程斜率低于中国大气降水线,河水δD与δ¹⁸O有一定的季节性特征,其受大气降水的影响较大,且丰水期较平水期以及枯水期相比更为明显;雅江河水中δ¹⁸O空间特征表现为,从上游至下游整体表现出先降低再升高的变化趋势.南北空间上表现为河水δD-δ¹⁸O从南至北逐步增高的趋势.δD-δ¹⁸O值与海拔高度具有较弱的负相关关系;受地表蒸发分馏、降水云团迁移以及流域岩石风化的影响,雅江河水d值季节性、空间性变化明显.     

黄土区典型小流域矿物化学风化及碳汇效应

黄土中蕴含了巨大的碳库,黄土中碳的转移对区域乃至全球碳循环具有重要影响。本文选择山西省临县一典型黄土小流域青凉寺沟流域进行调查分析,研究黄土水的化学特征及离子来源,分析黄土矿物的溶蚀过程及碳汇效应,并利用正演模型和水化学方法估算不同矿物的离子贡献比例及流域碳汇通量。结果发现,研究区黄土化学成分的含量由高到低依次为SiO_2、Al_2O_3、CaO、Fe_2O_3、MgO、K_2O、Na_2O,表现出贫SiO_2、Fe_2O_3,富CaO、MgO的特点;黄土水的pH呈中性偏碱,阴离子主要以HCO_3~-为主,阳离子以Na~+为主,水化学类型为重碳酸-钠型(HCO_3~--Na~+),水化学组成与黄土的化学组成相对应;流域内不同端元离子来源贡献计算结果表明,大气沉降、人类输入、蒸发盐矿物、硅酸盐矿物和碳酸盐矿物化学风化贡献的溶解物质分别占总溶解物质的1. 66%、6. 32%、10. 38%、62. 23%、19. 31%;黄土区长时间的水-矿物作用是硅酸盐矿物溶解贡献占主导的主要原因,阳离子置换反应、土壤-盐分浸出与蒸发以及人类输入对硅酸盐矿物溶解也有一定的贡献;受黄土区相对低温少雨的影响,黄土矿物的平均化学风化速率较低,为9. 31 t/(km~2·a),低于全球岩石的化学风化速率平均值36 t/(km~2·a),但是其消耗大气CO_2的速率较高,约为6. 34 t CO_2/(km2·a),明显高于同纬度三川河岩溶流域的碳汇速率(5. 28 t CO_2/(km~2·a));利用水化学径流法计算的青凉寺沟黄土小流域的矿物化学风化的大气CO_2消耗量为0. 18×10~4t/a,为中国黄土区大气CO_2消耗量的估算提供基础数据。