Interactions between octyl-β-D-glucoside and α-amino acids or small peptides

The interactions between octyl--D-glucoside and glycine in water have been investigated by surface tension, viscosity, and density measurements. The results show that the -amino acid causes an unexpected lowering of the critical micellar concentration of octyl--D-glucoside. Such a finding has been interpreted in temss of dipole-dipole interactions between the hydrophilic site of the surfactant and the peptidic cosluttes. From three to seven amino acid molecules have been estimated to be coordinated with each glucoside unity in the micellar state. The research has been extended to glycine oligopeptides and L-lysine. The latter compound has effects similar to those observed with glycine whereas diglycine and triglycine show weaker effects on the micellization process.     

On three conjectures by K. E. Shuler

Some fifteen years ago, Shuler formulated three conjectures relating to the large-time asymptotic properties of a nearest-neighbor random walk on ² that is allowed to make horizontal steps everywhere but vertical steps only on a random fraction of the columns. We give a proof of his conjectures for the situation where the column distribution is stationary and satisfies a certain mixing codition. We also prove a strong form of scaling to anisotropic Brownian motion as well as a local limit theorem. The main ingredient of the proofs is a large-deviation estimate for the number of visits to a random set made by a simple random walk on . We briefly discuss extensions to higher dimension and to other types of random walk.Dedicated to Prof. K. E. Shuler on the occasion of his 70th birthday, celebrated at a Symposium in his honor on July 13, 1992, at the University of California at San Diego, La Jolla, California.     

Crosslinking of vinyl‐terminated biphenyl and naphthalene side‐chain liquid‐crystalline poly(epichlorohydrin) derivatives

We performed the crosslinking of vinyl‐terminated biphenyl and naphthalene side‐chain liquid‐crystalline polyethers using peroxide‐type initiators with and without the addition of tertiary amine promoters. The crosslinking temperatures were chosen in the range of mesophase stability to allow the mesophase order to be frozen. The biphenyl derivatives, with a high isotropization temperature, were crosslinked to a large extent. This led to anisotropic thermosets. To crosslink naphthalene derivatives, amine promoters were needed, but degrees of crosslinking were lower, and anisotropic elastomers were obtained. Crosslinking processes were studied by differential scanning calorimetry, polarized optical microscopy, and Fourier transform infrared spectroscopy. The nature of the frozen mesophase was confirmed by X‐ray diffraction studies on mechanically oriented samples. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2237–2244, 2002     

Effect of microcrystallite preparation conditions on the formation of colloid crystals of cellulose

Stable colloidal suspensions of cellulose microcrystallites may be prepared from filter paper by sulfuric acid hydrolysis. Above a critical concentration, the suspensions form a chiral nematic ordered phase, or colloid crystal. The preparation conditions govern the properties of the individual cellulose microcrystallites, and hence the liquid crystalline phase separation of the cellulose suspensions. The particle properties and the phase separation of the suspensions were strongly dependent on the hydrolysis temperature and time, and on the intensity of the ultrasonic irradiation used to disperse the particles. The particle size of the microcrystallites was characterized with transmission electron microscopy and photon correlation spectroscopy. The surface charge was determined by conductometric titration. It was possible to fractionate the microcrystallites by size using the partitioning between isotropic and liquid crystalline phases; the longer microcrystallites migrate to the liquid crystalline phase     

Diffusion properties of cyclodextrins in aqueous solution at 25°C

Diffusion, density, and viscosity data are collected for the systems -cyclodextrin and -cyclodextrin in water. Frictional coefficients were computed with the help of literature activity data and a qualitative discussion of their concentration dependence was attempted.     

不同类型聚合物溶液对采油残余油的作用机理研究

通过实验测定了HPAM溶液和黄原胶溶液的流变性、在多孔介质中的流变性和残余阻力系数 ,计算了衰竭层效应 .用不同的浓度和注入速度进行了驱油实验 .提出聚合物分子缠结作用的增强不仅引起表观粘度增加或衰竭层厚度降低 ,而且使平行于油水界面的拉动残余油的力增加 ,从而使残余油饱和度降低 ,采收率提高 .随浓度增加 ,HPAM溶液的表观粘度和残余阻力系数增加 ,衰竭层厚度减小 ;黄原胶溶液的浓度高于缠结浓度时 ,衰竭层厚度和表观粘度变化不大 .注入速度增加时 ,两种聚合物溶液的衰竭层厚度均降低 ,HPAM溶液的残余阻力系数不变 ,粘弹性增加 ;而黄原胶溶液的残余阻力系数下降 .不同浓度和注入速度情况下两种聚合物溶液的驱油结果证实了文中提出的聚合物分子缠结作用和衰竭层效应对残余油的作用机理 .分子结构的不同是造成两种聚合物溶液在多孔介质中渗流规律和对残余油作用机理的差别的根本原因 .     

Enzymatic bleaching of organosolv sugarcane bagasse pulps with recombinant xylanase of the fungus Humicola grisea and with commercial cartazyme HS xylanase

Organosolv (ethanol/water and acetosolv) pulps were treated with Humicola grisea var. thermoidea and compared with Cartazyme HS xylanase-treated pulp. The ethanol/water pulps treated with H. grisea had the same viscosity as unbleached pulps (8 cP). Ethanol/water pulps treated with Cartazyme had higher viscosity than H. grisea-treated pulps (12 cP). Acetosolv pulps treated with H. grisea and Cartazyme presented a reduction in viscosity; however, the pulps treated with H. grisea had a lower reduction in viscosity than Cartazyme-treated pulps. Ethanol/water pulps treated with H. grisea had a 23% reduction in kappa number in 4 and 8 h of treatment, compared with the unbleached pulps. Cartazyme-treated pulps had a kappa number similar to that of the control pulps for 4 h of treatment. Extending the treatment time to 12 h resulted in a reduction of 33%. The acetosolv pulp treated with H. grisea had a kappa number reduced to 23% in 4 h. Cartazyme treatment resulted in a reduction of 55 and 44% in kappa number for 4 and 8 h of treatment, respectively, when compared with control pulp. Extending the treatment time to 12 h decreased the kappa number 72%. Fourier transform infrared spectra and principal component analysis showed differences among unbleached, H. grisea-treated, and Cartazyme-treated pulps.     

PBT／PET共混体系的协同效应

ＰＢＴ、ＰＥＴ具有良好相容性，且两种聚合物分子链间存在相互作用，它们的共混体系在熔体降温结晶过程中以及溶液中均表现出协同效应。虽然ＰＢＴ、ＰＥＴ在共混体系中各自形成晶区，但熔体降温结果过程中只能观察到一个结晶放热峰，当ＰＢＴ／ＰＥＴ共混物中两组份分子链段数目相近时，熔体降温结晶峰温较低，峰形变宽，共混体系的结晶程度降低在溶液中两组份分子链段数目相近时，共混物特性粘度（η）值最大，分子链的均方根末端     

Densities,Ultrasonic Speeds,Viscosities and Refractive Indices of Binary Mixtures of Benzene with Benzyl Alcohol,Benzonitrile, Benzoyl Chloride and Chlorobenzene at 303.15 K

Densities,ρ, ultrasonic speeds, u, viscosities,η, and refractive indices, n, of pure benzene, benzyl alcohol (BA), benzonitrile (BN), benzoyl chloride (BC), chlorobenzene (CB) and their thirty six binary mixtures, with benzene as common component, were measured at 303.15 K over the entire mole fraction range. From these experimental data the values of deviations in ultrasonic speed, △u, isentropic compressibility, △k_s,excess acoustic impedance, Z^E, deviation in viscosity, Dh, and excess Gibbs free energy of activation of viscous flow, G^*E, and partial molar isentropic compressibility, Kφ,2⁰ of BA, BN, BC and CB in benzene were computed. The variation of these derived functions with composition of the mixtures suggested the increased cohesion (molecular order) in the solution and that interaction (A-B)＞(A-A) or (B-B).Moreover, theoretical prediction of ultrasonic speed, viscosity and refractive index of all the four binary mixtures was made on the basis of empirical and semi-empirical relations by using the experimental values of the pure components. Comparison of theoretical results with the experimental values was made in order to assess the suitability of these relations in reproducing the experimental values of u, η and n. Also, molecular radii of pure liquids and the average molecular radii of binary mixtures were evaluated using the corresponding refractive indices of pure liquids and binary mixtures. The average molecular radii of binary mixtures were found to be additive with respect to mole fraction of the pure component.     

Surface viscoelasticity of phospholipid monolayers at the air/water interface

The surface viscoelastic properties of monolayers of two phospholipids DPPC (L--dipalmitoylphosphatidylcholine) and DMPE (L--dimyristoylphosphatidyl-ethanolamin), at the air-water interface have been investigated. Two techniques were used for the investigation. One involved use of an interfacial shear rheometer (torsion pendulum apparatus ISR1), to provide measurements of the shear viscosity _s as a function of surface pressure, and the second, a modified LB trough with an oscillating barrier to generate periodie dilation and compression so as to measure the dilational elastic modulusE as a function of surface area.Results indicate a strong dependence of _s andE upon monolayer phases. This suggests that the viscoelastic relaxation of monolayers can be understood as molecular rearrangements, domain exchange and molecular reorientations between different monolayer states.