Stabilization and characterization of colloidal gas aphron dispersions

Colloidal gas aphrons (CGAs) are finding increasing application in water processing, bioseparation, bubble-entrained floc flotation, separation of oil from sand, etc. This article proposes an effective method of encapsulation to stabilize the CGA bubbles with silicic sol solution for their characterization. The stabilized CGA bubbles can keep shapes and sizes for at least 12 h; even the bubbles smaller than 25 mum can also be stabilized and exist for very long times. Effects of concentration and pH of silicic sol solution on CGA stabilization were studied. The optimal ranges of concentration and pH of silicic sol solution are 0.15-0.25 mol/dm(3) and 7-10, respectively. The bubble distortion behavior in disturbance and size distribution of CGAs were examined by using the stabilization method and photographic techniques.     

Synergistic effects in mixed gas chromatographic stationary phases containing hepatkis(2.3.6-tri-O-pentyl)-β-cyclodextrin and AgNO3 or TINO3 in the separation of xylene isomers

Summary The gas chromatographic separation of xylene isomers using special mixed stationary phases consisting of heptakis(2.3.6-tri-O-pentyl)-β-CD-AgNO₃, heptakis (2.3.6-tri-O-pentyl)-β-CD-TINO₃ or bentone-34-AgNO₃ is investigated. The first two have positive synergistic effects for the separation of m, and p-xylene isomers, but negative synergistic effects for the m, and oisomers. The separation effects depend on temperature, mixing ratio and how mixing is accomplished.     

Photochemically catalyzed reaction of ochratoxin A with D- and L-cysteine

The photolysis (>300 nm) of ochratoxin A (OTA, N-[[(3R)-5-chloro-8-hydroxy-3-methyl-1-oxo-7-isochromanyl]carbonyl]-3-phenyl-L-alanine, 1) in the presence of excess (2 and 12 molar equiv) cysteine (CySH) has been investigated and found to yield sulfur adducts 5 and 6 that are characterized by liquid chromatography-mass spectrometry and 1H-NMR spectroscopy. The adduct 5 was ascribed to the Michael addition conjugate resulting from covalent attachment of CySH to the ochratoxin quinone (4) generated by photooxidation of OTA. This species was also formed by photolysis of a synthetic sample of the hydroquinone of OTA (ochratoxin hydroquinone, 3) in the presence of 12 equiv L-CySH. The conjugate 5 derived from photolysis of 3 with L-CySH was used for 1H-NMR analysis. The sulfur adduct 6 was the major species detected from covalent attachment of CySH to photoactivated OTA, and it resulted from direct displacement of the OTA Cl atom by CySH. The implications of the cysteinyl adducts to the in vivo toxicity of OTA are discussed, with particular emphasis given to conjugate 5, as products from the photooxidative pathway may be of relevance to the nephrotoxic properties of OTA.     

Metal-ligand bonding and rutile- versus CdI2-type structural preference in platinum dioxide and titanium dioxide

First principles electronic structure calculations were carried out to determine the relative stabilities of the rutile- and CdI₂-type structures of platinum dioxide (PtO₂) and titanium dioxide (TiO₂). The orbital interactions between the transition metal d- and oxygen p-orbitals were analyzed to gain insight into why PtO₂ has both the rutile- and CdI₂-type structures, but TiO₂ has only the rutile-type structure. The cause for the large difference in the c/a ratios of the CdI₂-type structures of TiO₂ and PtO₂ was examined.     

Nonlinear optical probe of biopolymer adsorption on colloidal particle surface: poly-L-lysine on polystyrene sulfate microspheres

A nonlinear optical technique--second harmonic generation (SHG)--has been applied to characterize the adsorption of poly-L-lysine on micrometer size polystyrene particles, whose surface is covered with negatively charged sulfonate groups, in aqueous solutions. Adsorption behavior of the biopolymer with two chain lengths (14 and 75 amino acid units; PL14 and PL75) has been examined. Centrifugation experiments were also performed to support the adsorption measurements made using SHG. The adsorption free energies of the two polymers PL75 and PL14 are determined as -16.57 and -14.40 kcal/mol, respectively. The small difference in the adsorption free energies of the two chain lengths, however, leads to dramatic difference in the concentration needed for saturated surface coverage: nearly 50 times higher concentration is needed for the smaller polymer. Under acidic colloidal conditions, polylysine is found to adsorb in a relatively flat conformation on the surface. The surface area that each polylysine molecule occupies is nearly 1 order of magnitude larger than the size of the molecule in its extended form. The low adsorption density is likely a result from Coulombic repulsion between the positive charges on the amino acid units of PL. The measurements demonstrate the utility of SHG as an efficient and sensitive experimental approach for measuring adsorption characteristics of bio/macromolecules on colloidal particles and define surface and colloidal conditions for achieving maximum surface coverage of a widely used biopolymer.     

242-260nm波长区CS2分子的多光子解离电离

在242－260nm波氏范围通过CS2分子的共振增强多光子电离（REMPI）获得了母体离子CS和碎片离子的分质量激发谱．在λ＜246.4nm区间，CS激发谱上呈现出来源于CS2双光子电离的弥散谱带,碎片离子激发谱的归属强烈提示多光子过程中有中性基电子态的CS和S（经由CS2的光解离）产生：（1）CS 的谱带主要来源于中性CS碎片经由单光子跃迁产生的（1＋1）共振增强电离，（2）除了部分S 的谱峰来自CS 的光解外，多数S 的锐谱峰来自中性S原子经由3p3（2D0）4p，3p3（4S0）np（n＝6，7，8）←3p43pJ（J＝2，1,0）双光子跃迁产生的（2＋1）共振增强电离．     

天祝煤MRF工艺热解焦油的组成分析

本文对天祝煤ＭＲＦ（ＭｕｔｉｓｔａｇｅＲｏｔａｒｙＦｕｒｎａｃｅ）热解焦油进行了常规及元素分析，了解其基本特性；用毛细管色谱分别对焦油各馏分进行了分析，共定性定量了１０３种化合物，酚类化合物以低级酚（苯酚、甲酚）为主，中性化合物为多烷基芳烃衍生物、脂肪族链状烷烃和烯烃。上述分析结果为从焦油中提取酚类化工原料或将其加工成各种燃料油的可行性提供了依据。     

Transient rheological behavior of lyotropic (acetyl)(ethyl)cellulose/m-cresol solutions

The chiroptical properties and transient rheological behavior of (acetyl)(ethyl)cellulose (AEC) m-cresol liquid crystalline solutions have been investigated. Chiroptical properties were manipulated through (i) increasing degree of acetylation of ethyl cellulose (EC), and (ii) blending AEC with EC. At the same average degree of acetylation (DA), the chiroptical properties of pure AEC were different from those of the EC/AEC mixtures. However, at the same DA, the AEC and mixed AEC/EC solutions showed similar steady state flow and oscillatory behaviors, but the transient behaviors were different. At high flow rates the mixed AEC/EC solutions exhibited double recoil after cessation of steady-state flow, whereas the AEC solutions showed double recoil only in the high DA AEC solutions. All solutions, pure and mixed, had the same stress relaxation behavior. Both pitch and handedness affected the transient behavior. After cessation of high shear rate flow, the rate of modulus evolution decreased with increasing pitch, and was faster in right-handed mesophases than in left-handed ones at a similar pitch.     

Theoretical study on the molecule C30H20: five carbon–carbon single bonds linking a dodecahedrane cage and a pentaprismane cage

Using geometry optimization and DFT method at the B3LYP/6-31G* level of theory for C₃₀H₂₀, an equilibrium geometry is identified that has the form of polyhedral hydrocarbon with five carbon–carbon single bonds linking a dodecahedrane cage and a pentaprismane cage. Thus, this molecule is a tri-cage molecule with two pentaprismane cages and one dodecahedrane cage. Vibrational frequencies and the infrared spectrum are computed at the same level of theory. The heat of formation for C₃₀H₂₀ has been estimated in this paper. The heat of formation of C₃₀H₂₀ as well as the vibrational analysis indicates that this molecule enjoys sufficient stability to allow for its experimental preparation.