ISSN:0005-9021    

DOI:10.1002/bbpc.198400042

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.198400043

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractSilver films were electrochemically roughened by oxidation/reduction cycles in different solutions. — Aging of these films in contact with electrolyte solution was monitored for various potentials by means of double layer capacitance measurements. No specifically adsorbable species were present during the aging process. The surface flattening taking place is strongly dependent of the initial microstructure developed during the roughening cycle. — The influence of traces of dissolved oxygen as the main “impurity” was studied in detail. The capacitance/potential curves indicate a pH dependent adsorption/desorption of the superoxide ion O2−. The effect of this process on the mechanism of the O2‐reduction i

ISSN:0005-9021    

DOI:10.1002/bbpc.198400044

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractIt is shown that the transport properties of ion exchange membranes in hyperfiltration experiments with acetonitrile/water mixtures are determined by the selectivity of solvation of the counterions by the components of the mixture.

ISSN:0005-9021    

DOI:10.1002/bbpc.198400045

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractIn analogy to the internal oxidation of oxide solid solutions, the internal reduction of oxide solid solutions is investigated. The kinetics of internal reactions are formally analyzed, and it is shown experimentally that these reactions in the reduction mode do occur as predicted. In the case of internal reduction of transition metal oxide solid solutions of the type (A, B) O, often fast diffusion paths determine the evolution of the reaction morphology.

ISSN:0005-9021    

DOI:10.1002/bbpc.198400046

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe anodic oxidation of NH2OH on Pt in neutral and acid solutions was studied using CV, RRDE and Mass Spectroscopic Cyclic Voltammetry. Thus, thei/ϕ‐curves obtained could be correlated to the rates of formation of the gaseous products N2, N2OtNO and NO2. Three anodic waves were distinguished, each representing 2e‐processes as concluded from the products NOH, NO2−and NO3−belonging to the respective wave. NO is a side product formed by anodic oxidation of NOH within the raising part of the second wave. A detailed mechanism is proposed on the basis of these

ISSN:0005-9021    

DOI:10.1002/bbpc.198400047

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractChloroform is decomposed by irradiation with ultrasonic waves to yield a large number of products. The major products are various unsaturated compounds. Decomposition occurs only in the presence of a monoatomic‐ or diatomic gas. Free radicals and carbenes are postulated as intermediates of sonolysis which can only be scavenged by volatile additives such as O2or c‐hexene. In the presence of 10% c‐hexene, the rate of sonolysis of chloroform is increased and various additional products are formed. Pure c‐hexene is decomposed at a much lower rate than chloroform. The sonolysis of chloroform proceeds at a rate comparable to that o

ISSN:0005-9021    

DOI:10.1002/bbpc.198400048

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractQuantum yields for the direct trans → cis (Φl→c) and cis → trans (Φc→l,) photoisomerization of 4‐nitro‐,4,4′‐dinitro‐, and 4‐nitro‐4′‐methoxystilbene (NS, DNS, and NMS, respectively) were measured in solution at room temperature as a function of the concentration of quenchers (ferrocene, azulene, and oxygen). The results are in full agreement with a previously proposed reaction scheme for NMS, involving a triplet state as an intermediate in the trans → cis photoisomerization and both triplet and excited singlet states in the cis → trans photoisomerization. The branching ratios for decay of twisted configurations of the first excited singlet (1p*) and the lowest triplet (3p*) into the ground states and the yields for intersystem crossing from the first excited trans and cis singlet configurations to the lowest triplet state (Φliscand Φcisc, respectively) were determined. Φliscand Φciscare large (0.45–0.86) for NS and DNS and significantly smaller for NMS in polar solvents. Since the trans triplet state (3t*) is in thermal equilibrium with3p* it is this3t* ⇄3p* equilibrium which is accessible for the influence of triplet quenchers and solvent properties in the cis ⇄ trans photoisomerization. At room temperature oxygen quenches mainly3p* while at lower temperatures (between 0 and — 140°C) also3t* is quenched. The yields for the conversion1t*→1p* and for formation of 4a,4b‐dihydrophenanthrene (DHP) are small. From the kinetic analysis no indication was found for involvement of excited states of DHP in the ci

ISSN:0005-9021    

DOI:10.1002/bbpc.198400049

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractDecay of the lowest triplet state of 4‐nitro‐, 4,4′‐dinitro‐, and 4‐nitro‐4′‐methoxystilbene (NS, DNS, and NMS, respectively) was studied by nanosecond laser photolysis in solution at room temperature. The triplet decays predominantly via intersystem crossing at the twisted configuration followed by internal rotation into the cis or trans ground states. Rate constants for triplet decay were determined in various solvents as a function of the concentration of ferrocene, azulene, and oxygen. Quenching by azulene and ferrocene leads only to trans isomers whereas quenching by oxygen does not markedly shift the photostationary state are room temperature. The results support the assumption of an equilibrium between the planar trans configuration (3t*) and3p* and allows the estimation ofkpand the triplet equilibrium constantK5= k5/k−5= [3p*]/[3t*].K5shows a trend to decrease with increasing solvent polarity. For NS this corresponds to a shift of the3t* ⇄3p* equilibrium from — 75% of the3p* configuration in n‐pentane to ˜25% in methanol. This shift is explained by the greater stabilization of the planar3t* configuration by polar solvents in comparison to that of the less polar twisted3p* configuration. The solvent dependent change inkpis less pronounced, giving average values of 3.0 · 107and 1.7 · 107s

ISSN:0005-9021    

DOI:10.1002/bbpc.198400050

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractMembrane structure and crystal‐liquid crystal phase transition behaviors were investigated for the water system of totally artificial lipids with cationic or anionic head group and two alkyl chains. These artificial lipids formed multilamellar liposomes composed of a bimolecular layer. The phase transition temperature from gel to liquid crystalline lamellae decreased steadily to a limiting temperature with an increase in water concentration up to the lipid fraction of 0.80 — 0.85. This kind of phase diagram means that the artificial lipids have characteristics of both thermotropic and lyotropic mesomorphisms. For the cationic artificial lipid, the thickness of the bimolecular lamella in a gel state was shorter than a bimolecular length calculated on the assumption of planar zigzag conformation of the alkyl chains. This suggests that the hydrocarbon chains in a gel state are packed with the chain axes inclined at a certain angle to the lamellar surface. The diffusive permeability of the polymer/artificial lipid composite membranes to water or ions exhibits a distinct jump in the vicinity of the crystal‐liquid crystal phase transition temper

ISSN:0005-9021    

DOI:10.1002/bbpc.198400051

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY