The phase diagram of a series of poly(1,2‐octylene oxide)–poly(ethylene oxide) (POO–PEO) diblock copolymers is determined by small‐angle X‐ray scattering. The Flory–Huggins interaction parameter was measured by small‐angle neutron scattering. The phase diagram is highly asymmetric due to large conformational asymmetry that results from the hexyl side chains in the POO block. Non‐lamellar phases (hexagonal and gyroid) are observed near fPEO = 0.5, and the lamellar phase is observed for fPEO ≥ 0.5.
In this paper we show that an affine bijection f : T1→ T2 between two polyhedral complexes T1,T2 , both of which consist of a union of faces of two convex polyhedra P1 and P2 , necessarily respects the cell-complex structure of T1 and T2 inherited from P1 and P2 , respectively, provided f extends to an affine map from P1 into P2 . In addition, we present an application of this result within the area of T-theory to obtain a far-reaching generalization
of previous results regarding the equivalence of two distinct constructions of the phylogenetic tree associated to ``perfect'
(that is, treelike) distance data.
Received September 30, 1999, and in revised form February 25, 2000. Online publication May 15, 2000. 相似文献
In2the concept of a coherent decomposition of a finite metric is introduced and it is conjectured that every such metric can be decomposed into a coherent sum of prime metrics in a unique way. In this note we give a counterexample to this conjecture. 相似文献
The adsorption of Immunoglobulin G on a titanium dioxide (TiO(2)) electrode surface was investigated using (125)I radiolabeling and electrochemical impedance spectroscopy (EIS). (125)I radiolabeling was used to determine the extent of protein adsorption, while EIS was used to ascertain the effect of the adsorbed protein layer on the electrode double layer capacitance and electron transfer between the TiO(2) electrode and the electrolyte. The adsorbed amounts of Ig.G agreed well with previous results and showed approximately monolayer coverage. The amount of adsorbed protein increased when a positive potential was applied to the electrode, while the application of a negative potential resulted in a decrease. Exposure to solutions of Ig.G resulted in a decrease of the double layer capacitance (C) and an increase in the charge-transfer resistance (R(2)) at the electrode solution interface. As more Ig.G adsorbed onto the electrode surface, the extent of C and R(2) variation increased. These capacitance and charge-transfer resistance variations were attributed to the formation of a proteinaceous layer on the electrode surface during exposure. 相似文献
Lipase activity and stability was investigated in dialkylimidazolium and pyrrolidinium-based ionic liquids with a variety of anions including hexafluorophosphate, acetate, nitrate, methanesulfonate, trifluoroacetate, and trifluoromethylsulfonate. The initial rate of lipase-catalyzed transesterification of methyl methacrylate in these ionic liquids and several organic solvents was examined as well as the polytransesterification of divinyl adipate and 1,4-butanediol. Free lipase (Candida rugosa) catalyzed the transesterification of methyl methacrylate in 1-butyl-3-methylimidazolium hexafluorophosphate at a rate 1.5 times greater than in hexane. However, no detectable activity was observed in all the "hydrophilic" ionic liquids studied. Methods of enzyme stabilization including adsorption, PEG-modification, and immobilization in polyurethane foam were ineffective in improving enzymatic activity in the hydrophilic ionic liquids. Polytransesterifications performed in 1-butyl-3-methylimidazolium hexafluorophosphate using Novozym 435 produced polyesters with weight average molecular weights limited to 2900 Da due to precipitation of the polymer. Solvatochromic studies and partition coefficient measurements suggest that ionic liquids are more polar and hydrophilic than organic solvents such as hexane, acetonitrile, and tetrahydrofuran. Stability studies indicate that lipases exhibit greater stability in ionic liquids than in organic solvents including hexane. 相似文献
The adsorption of two model proteins, human serum albumin and immunoglobulin G, on a gold electrode surface was investigated using 125I radiolabeling and cyclic voltammetry (CV). 125I radiolabeling was used to determine the extent of protein adsorption, while CV was used to ascertain the effect of the adsorbed protein layer on the electron transfer between the gold electrode and an electroactive moiety in solution, namely, K3Fe(CN)6. The adsorbed amounts of HSA and IgG agreed well with previous results and showed approximately monolayer coverage. The amount of adsorbed protein increased when a positive potential (700 mV) was applied to the electrode, while the application of a negative potential (-800 mV) resulted in a decrease. When the solution pH was varied to alter the charge on the protein, the adsorption trends appeared to follow electrostatic interaction, namely, greater adsorption when the electrode and the protein possessed opposite charge and vice versa. The adsorbed protein layer had the effect of blocking the electron transfer. It was possible to correlate the degree of electron blocking with the amount of adsorbed protein to show that the greater the adsorption, the larger the blocking effect. Of the two proteins used, HSA proved to be more efficient at blocking the electron transfer. 相似文献