Thermodynamic derivative properties and densities for hyperbaric gas condensates: SRK equation of state predictions versus Monte Carlo data

The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, a_ij, and three expressions of the crossed terms of the repulsive parameter, b_ij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of a_ij and b_ij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations.     

Differentiation between tracks and damages in SSNTD under the atomic force microscope

We have observed three-dimensional sponge-like structures as well as strips of connecting pits on the surface of the LR 115 detector after etching, which can be confused with the small tracks formed after short etching time. We have employed an atomic force microscope (AFM) to study these “damages” as well as genuine alpha tracks for short etching time. It was found that while the track and damage openings could be similar in size and shape, the depths for the damages were consistently smaller. Therefore, the depth of the pits will serve as a clear criterion to differentiate between tracks and other damages. The ability to discriminate between genuine tracks from other damages is most important for etching for short time intervals.     

Microenvironmental differences amongst micelles of various shapes and structures

Micelles of different amphiphiles adopt different shapes and internal packing arrangements in water, depending on their chemical structures and the conditions of the medium. Two microenvironmental features, namely the polarity and the microviscosity that the aggregate offers to a solubilized molecule, have been monitored using extrinsic fluorescence probes. While the differences between micelles of spherical and rod-like shapes are not always distinct, stacked micelles and peptide micelles offer distinctly lower polarity and higher microviscosity to solubilizates than the others.     

Retention,enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column

Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an ₁-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.     

Emission band shape probes of the mixed-valence excited state properties of polypyridyl-bridged bis-ruthenium(II) complexes

The absorption spectra and emission spectral band shapes of several polypyridine-ligand (PP) bridged bis-ruthenium(II) complexes imply that the Ru(II)/Ru(III) electronic coupling is weak in their lowest energy metal to ligand charge transfer (MLCT) excited states. Many of these PP-bridging ligands contain pyrazine moieties and the weak electronic coupling of the excited states contrasts to the strong electronic coupling inferred for the correlated mixed-valence ground states. Although the bimetallic complexes emit at significantly lower energy than their monometallic analogs, the vibronic contributions to their 77 K emission spectra are much stronger than expected based on comparison to the monometallic analogs (around twofold in some complexes) and this feature is characteristic of bimetallic complexes in which the mixed-valence excited states are electronically localized. The weaker excited state than ground state donor/acceptor electronic coupling in this class of complexes is attributed to PP-mediated super-exchange coupling in which the mediating orbital of the bridging ligand (PP-LUMO) is partly occupied in the MLCT excited states, but is unoccupied in the ground states; therefore, the vertical Ru(III)-PP⁻ (MLCT) energy is larger and the mixing coefficient smaller in these excited states than is found for Ru(II)-PP in the corresponding ground states.     

矿化剂浓度和温度对水热法合成氧化锌晶体形态的影响

采用水热法，通过改变矿化剂浓度和温度合成了具有不同形态的氧化锌晶体。在较低的温度(350℃)，填充度为35％。矿化剂KOH浓度小于2mol／L时，只合成了氧化锌微晶。当矿化剂KOH浓度大于3mol/L时，合成出多种形态氧化锌晶体，大的晶体达到几十到几百微米，小晶体仅几微米。当矿化剂KOH浓度从4mol／L增加到5mol／L时，晶体的大小没有明显改变。在高矿化剂条件下合成的晶体显露完整的晶面结构，主要显露柱面m{1010}、锥面p{1011}、负极面O面{0001}，有时也显露Zn面{0001}。晶体表面出现斑坑，显示出晶体的表面缺陷。在430℃，填充度为35％，矿化剂KOH浓度大于1．5moL／L时。合成了多种形态氧化锌晶体，大晶体有几十到几百微米，小晶体仅几微米。当矿化剂KOH浓度为2mol／L，KBr浓度为lmol/L时，最大晶体的长度达到1mm。矿化剂KOH浓度为4mol/L时，晶体没有增大。粒度较大的氧化锌晶体形状多为六棱锥体，显露柱面m{1010}、锥面p{1011}、负极面O面{0001}。晶体表面光滑，完整性好。质量高于350℃时合成的晶体。     

Computer Simulation of a 3-D Sensing System with Structured Illumination

A computer simulation system of three-dimensional sensing with structured illumination is presented. It includes the generation of deformed fringe patterns from 3-D shapes and the reconstruction of 3-D shapes, conversely. Some experimental results of the deformed fringe pattern and the reconstructed object shapes are presented. We have also discussed the effect of some major system parameters on the measurement results and considered how to correct these parameters according to the measurement result of the standard plane. Using this simulation system, the major system parameters: environmental conditions, measurement accuracy and algorithm evaluation of the 3-D shape measurement system based on PMP, FTP, SPM, etc., can be researched. © 1997 Elsevier Science Ltd. All rights reserved.     

Analytical predictions of shapes of laminar diffusion flames in microgravity and earth gravity

Flame shape is an important observed characteristic of flames that can be used to scale flame properties such as heat release rates and radiation. Flame shape is affected by fuel type, oxygen levels in the oxidiser, inverse burning and gravity. The objective of this study is to understand the effect of high oxygen concentrations, inverse burning, and gravity on the predictions of flame shapes. Flame shapes are obtained from recent analytical models and compared with experimental data for a number of inverse and normal ethane flame configurations with varying oxygen concentrations in the oxidiser and under earth gravity and microgravity conditions. The Roper flame shape model was extended to predict the complete flame shapes of laminar gas jet normal and inverse diffusion flames on round burners. The Spalding model was extended to inverse diffusion flames. The results show that the extended Roper model results in reasonable predictions for all microgravity and earth gravity flames except for enhanced oxygen normal diffusion flames under earth gravity conditions. The results also show trends towards cooler flames in microgravity that are in line with past experimental observations. Some key characteristics of the predicted flame shapes and parameters needed to describe the flame shape using the extended Roper model are discussed.     

Evaluation of in vitro,in silico antidiabetic and antioxidant potential of bioactivity based isolated “Pakistanine” from Berberis baluchistanica

Bioassay based fractionation of methanolic extract of Berberis baluchistanica (Berberidaceae), used traditionally for internal injuries, led to the isolation of known compounds (1–4). The structure of these compounds was elucidated by different spectroscopic analysis and available literature data. Antidiabetic and antioxidant potentials of B. baluchistanica fractions and isolated compounds were evaluated using in vitro alpha- amylase and DPPH assays. The isolated compounds were identified as obamegine (1), pakistanine (2), 8-oxyberberine (3) and baluchistine (4). Obamegine was reported from many other species of this genus but it is first time isolated from B. baluchistanica in present study. Moreover, in vitro pakistanine (2) was found as bioactive lead molecule for hypoglycemic (IC₅₀:40.26 µg/ml) and antioxidant (IC₅₀:14.15 µg/ml) activities compared to acarbose (IC₅₀:33.68 µg/ml) and ascorbic acid (IC₅₀:0.41 µg/ml). To the best of our knowledge, no previous data were available for these biological activities. Additionally, in silico antidiabetic and antioxidant activity of pakistanine against two proteins, α-amylase (-9.7 kcal/mol) and tyrosinase (-8.7 kcal/mol) are reported here for the first time. The molecular docking binding interactions authenticate and support the above-mentioned activities and are helpful in predicting the mechanism of action of pakistanine (2).