Determination of gas-oil miscibility conditions by interfacial tension measurements

Processes that inject gases such as carbon dioxide and natural gas have long been and still continue to be used for recovering crude oil from petroleum reservoirs. It is well known that the interfacial tension between the injected gas and the crude oil has a major influence on the efficiency of displacement of oil by gas. When the injected gas becomes miscible with the crude oil, which means that there is no interface between the injected and displaced phases or the interfacial tension between them is zero, the oil is displaced with maximum efficiency, resulting in high recoveries. This paper presents experimental measurements of interfacial tension between crude oil and natural gases (using a computerized drop shape analysis technique) as a function of pressure and gas composition at the temperature of the reservoir from which the crude oil was obtained. The point of zero interfacial tension was then identified from these measurements by extrapolation of data to determine minimum miscibility pressure (MMP) and minimum miscibility composition (MMC). The gas-oil miscibility conditions thus obtained from interfacial tension measurements have been compared with the more conventional techniques using slim-tube tests and rising-bubble apparatus as well as predictive correlations and visual observations. The miscibility pressures obtained from the new VIT technique were 3-5% higher than those from visual observations and agreed well with the slim-tube results as well as with the correlations at enrichment levels greater than 30 mol% C2+ in the injected gas stream. The rising bubble apparatus yielded significantly higher MMPs. This study demonstrates that the VIT technique is rapid, reproducible, and quantitative, in addition to providing visual evidence of gas-oil miscibility.     

Dimeric iron n-confused porphyrin complexes

A dimeric iron N-confused porphyrin, [Fe(NCTPP)]2 was obtained from the anaerobic reaction of Fe(NCTPP)Br with NaSePh while under aerobic conditions a hydroxo bridged iron dimer with Na bridging the outer-N atoms was obtained and oxygenation occurred on the inner core pyrrolic carbon to form a novel ONCTPP porphyrinic ring.     

Electrochemical genosensing properties of gold nanoparticle–carbon nanotube hybrid

We have investigated the electrochemical genosensing properties of gold nanoparticle–carbon nanotube hybrid. Thiolated oligonucleotide probes and mercaptohexanol were self-assembled onto the Au–CNT hybrid. The hybridization events of target oligonucleotides are monitored using electrochemical impedance spectroscopy, cyclic voltammetry and a.c. voltammetry techniques. A redox-active mediator is used to detect the oxidation of guanine residues. The as-fabricated genosensor is able to differentiate between complementary and mismatched hybridizations, relying on the oxidation current of the guanine residues mediated via .     

Specific heat and Lindemann-like parameter of metallic clusters: mono- and polyvalent metals

The Brownian-type molecular dynamics simulation is revisited and applied to study the thermal and geometric properties of four mono- and two polyvalent metallic clusters. For the thermal property, we report the specific heat at constant volume CV and study the solid-liquid-like transition by scrutinizing its characteristic. For the geometric property, we calculate the root mean square relative bond-length fluctuation delta as a function of increasing temperature. The thermal change in delta reflects the movement of atoms and hence is a relevant parameter in understanding the phase transition in clusters. The simulated results for the CV of alkali and aluminum clusters whose ground state structures exhibit icosahedral symmetry generally show one phase transition. In contrast, the tetravalent lead is quite often seen to exhibit two phase transitions, a premelting process followed by a progressive melting. In connection with the premelting scenario, it is found here that those (magic number) clusters identified to be of lesser stability (among other stable ones) according to the second energy difference are clusters showing a greater possibility of undergoing premelting process. This energy criterion applies to aluminum clusters nAl=28 and 38. To delve further into the thermal behavior of clusters, we have analyzed also the thermal variation of deltaT and attempted to correlate it with CV(T). It turns out that the premelting (if exist) and melting temperatures of the smaller size clusters (n less, similar 50) extracted from CV do not always agree quantitatively with that deduced from delta.     

水热合成CdS纳米晶体的形貌控制研究

研究了水热合成CdS纳米晶体形貌的化学控制，选择不同的络合试剂为模板,研究其对水热合成CdS纳米晶体形貌的影响.实验发现若以络合试剂乙二胺、甲胺为模板时，产品CdS晶体的形貌分别为（20～30） nm×（200～600） nm和（40～50） nm×（200～600） nm尺寸的纳米棒;而以络合试剂吡啶、 氨为模板时，产品CdS晶体的形貌分别为平均尺寸约30 nm和20 nm的纳米颗粒.用XRD、TEM、XPS、PL和Raman光谱等技术对所得CdS纳米棒进行了表征.同时对水热合成CdS纳米晶体形貌的模板控制机制进行了探讨，提出了一种水热合成CdS纳米棒的络合物结构诱导生长机理.     

Synthesis of 6（E）—Geranylgeraniol—19—oic Acid

Facile synthesis of 6(E)-geranylgeraniol-19-oic acid 1,a naturally occurring alicyclic diterpene acid, by a Horner-Wadsworth-Emmons olefination of two readily available fragments 2 and 3,is described.     

Separation and determination of some stereoisomers by capillary gel electrophoresis with cyclodextrin incorporated in polyacrylamide gel

Capillary gel electrophoresis (CGE) was successfully applied to the separation of optically active isomers and position isomers by incorporating a suitable cyclodextrin chiral selector in polyacrylamide gel. A commercially available ß-cyclodextrin (ß-CD) was used for enantioselectivity towards o-, m- and p-nitrobenzoic acid, o-, m- and p-hydroxybenzoic acid, o-, m- and p-toluic acid and the optical isomers of dansyl-D,L-leucine and R,S-1,1-binaphthyl-2,2-dihydrogenphosphate. Especially the effect of organic solvents, such as acetonitrile, methanol, dimethylsulphoxide and others were examined in detail. The resolution varied to some extent with the addition of the organic solvent to the polyacrylamide gel and the running buffer solution. The possible mechanism has also been discussed. In addition, quantitative aspects of the separation of stereoisomers using CGE have been studied, showing that both the resolution and accuracy of the determinations were affected by the ratio of the enantiomers.     

凝胶型聚合物电解质的电导率与温度的关系

凝胶型聚合物电解质的电导率与温度的关系孙晓光，林云青，齐力，景遐斌，王佛松（中国科学院长春应用化学研究所长春１３００２２）关键词凝胶电解质，离子电导率，活化能无定形聚合物电解质电导与温度的依赖关系一般可用Ｖｏｇｅｌ－Ｔａｍｍａｎ－Ｆｕｌｃｈｅｒｃ（Ｖ...     

激光拉曼光谱在高分子中的应用

论述了激光拉曼光谱对高分子结构、结晶形态和表征,反应动力学过程和取向的研究,还介绍了纵向声学模、共振、高温高压、光波导和付里叶拉曼光谱在高分子研究中的最新进展。