ISSN:0005-9021    

DOI:10.1002/bbpc.19840880102

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

年代:1984

数据来源: WILEY

摘要:

AbstractA new technique is presented which allows the gaseous and volatile products of electrochemical reactions to be measured quantitatively and with high sensitivity. The equipment consists of the electrochemical cell, the membrane inlet system and the mass spectrometer. Products being formed at the porous working electrode are sucked through the porous membrane into the ion source of the mass spectrometer. The mass intensity detected is proportional to the corresponding faradaic current. A rate of formation of 5 · 10−11mol s−1can well be measured. The rise time of the mass intensity is short enough to allow it to be quantitatively correlated to the faradaic current even at variing electrode potential. This is utilized in mass spectroscopic cyclic voltammetry. The feasibility of the method is descr

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880103

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe adsorption and oxidation of CO on porous Pt‐electrodes was studied with Differential Electrochemical Mass Spectroscopy (DEMS). The following results were obtained:1. When CO is removed from the solution after adsorption has taken place, the adsorbed species mainly occupies two Pt‐sites. It is oxidized within two peaks at 0.52 and 0.73 V giving CO2thereby consuming 2 electrons. No evidence of “reduced CO” was found independent of the adsorption potential.2. When CO is present in the solution, a physisorbed species reversibly bound to one Pt‐site covers about 60% of the electrode surface. It is oxidatively desorbed

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880104

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

年代:1984

数据来源: WILEY

摘要:

AbstractIncorporation of iron (a few percent) into RuS2(ΔEG= 1.85 eV) changes the energy gap to ΔEG= 1.1 eV. The resulting n‐type compound, which can approximately be described by “Ru1‐xFexS2”, is able to evolve oxygen and chlorine from aqueous electrolytes utilizing visible and near infrared light under energy gain with high quantum efficiency (23% to 60%). — Oxygen and chlorine evolution, mediated by infrared light, is found clearly below the respective redox potentials. Under such conditions of energy conversion the electrode does not indicate signs of photocorrosion. At more extreme electrode potentials traces of a ruthenium tetroxide species are observed — Attempts are made to correlate the (inhomogeneous) distribution of iron in Ru1‐xFexS2electrodes with photocurrent spectra and scanning laser spot current patterns. — Experiments show that the electrode surface is subject to chemical changes during the photoreaction with water. They are investigated by means of capacity measurements, dynamic current voltage sweeps, and systematical variations of redox potentials in the electrolyte. — A model is presented which accounts for the role of iron in this compound and which explains its photoelectrochemical advantages co

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880105

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

年代:1984

数据来源: WILEY

摘要:

AbstractSpectral sensitization process was examined by measuring the fluorescence intensities and the photocurrents caused by rhodamine B esterically bound with the surface species of SnO2. It was found that about 20% of its fluorescence intensity were reduced by the Sn02 substrate, and this value was well coincident with the maximum quantum efficiency of the sensitized photocurrent. From the results the charge transfer mechanism of supersensitization is discussed.

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880106

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe investigation of the native DNA structure of various sources with the help of X‐ray diffraction techniques of fibres reveals a striking similarity of the structural dimensions of all DNAs. Contrary to these results sequence analysis of the nucleotide bases demonstrates the uniqueness of the vast majority of domains even within the DNA of a single species. In this paper we will demonstrate that there is a possibility to characterize the different DNAs by the help of differential adiabatic scanning calorimetry. The heat capacity as a function of temperature is unique for each DNA and can serve to identify the particular DNA and can help to group the eucariotic, procariotic and the viral DNAs. This will be shown for eleven different DNA

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880107

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe optical constants of chlorobenzene between 1500 and 600 cm−1have been determined with the help of ATR spectroscopy in the temperature range between — 30 and + 80°C. — The observed decrease of the integral intensity with temperature can be explained by the change of density and lokal field. The increase of the band half‐width is a result of faster molecular motion. Form and intensity of the band near 900 cm−1are temperature insensitive. — The temperature dependence of the refractive index in regions with negligible absorption has to be explained by the combined influence of density and change of lokal field with density. Even after taking due account of this effect the real and imaginary parts of the molecular polarizability remain temperature dependent within the

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880108

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

年代:1984

数据来源: WILEY

摘要:

AbstractNew, absolute measurements of the thermal conductivity of liquid n‐hexane and n‐octane are reported. The measurements have been carried out within the temperature range 34—90°C and over the pressure range 1.8 — 640 MPa in a transient hot‐wire instrument. It is estimated that the experimental data have an uncertainty of ±0.3%. The density dependence of the thermal conductivity of n‐hexane and n‐octane may be satisfactorily represented by means of an equation whose form is based upon an heuristic modification of the Enskog theory for transport processes in dense fluids. The optimum correlations for n‐hexane and n‐octane are slightly different from those which have been found to be universal among normal alkanes with an odd number of carbon atoms. This behaviour is predominantly attributable to the superior accuracy of the present experimental data, resulting from an improved treatment of radiative heat transport

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880109

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

年代:1984

数据来源: WILEY

摘要:

AbstractEvaporation of the compounds Mg5Hg3(s), Mg2Hg(s), Mg5Hg2(s), and Mg3Hg(s) was studied using a Knudsen cell‐mass spectrometer system. They evaporate according to the equations2 Mg5Hg3(s) ⇄ Hg(g) + 5 Mg2Hg(s), (1)5 Mg5Hg(s) ⇄ Hg(g) + 2 Mg5Hg2(s), (2)3 Mg5Hg2(s) ⇄ Hg(g) + 5 Mg3Hg(s), and (3)Mg3Hg(s) ⇄ Hg(g) + 3 MgHg(s) (4)The Hg partial pressures of Eqs. (1) to (4) arelog(pPa) = (4973.1 ± 60.3) K/T + (9.886 ± 0.12) (440 ‐ 540 K),log(pPa) = (6605.6 ± 69.1) K/T + (10.91 ± 0.11) (499 ‐ 7110 K),log(pPa) = (7118.3 ± 116.5) K/T + (10.91 ± 0.19) (548 ‐ 9890 K), andlog(pPa) = (7502.3 ± 58.8) K/T + (11.29 ± 0.10) (525 ‐ 695 K).The enthalpy changes of reactions Eqs. (1) to (4) were determined by the second and third law method. Formation enthalpies in kJ mol−1at 298 K were obtained as –60.5 ± 4.3 (MgHg2), –56.4 ± 1.7 (MgHg), –217.1 ± 7.3 (Mg5Hg3), –79.8 ± 2.8 (Mg2Hg), –166.0 ± 6.8 (Mg5Hg2), and –84.2 ± 4.0 (Mg3Hg) for the compounds given in parentheses. Gibbs energies of formation of these compounds are

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880110

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

年代:1984

数据来源: WILEY

摘要:

AbstractOn light absorption in the long wavelength1La‐band 9‐alkyl‐substituted anthracenes in fluid solutions isomerise with low quantum yield (about 0.016 at 300 K) to the 9,10‐Dewarisomer, provided the substituent is sufficiently spacefilling (t‐butyl or t‐pentyl). On increasing the viscosity and/or reducing the temperature the quantum yield of this valence isomerisation decreases while the quantum yield of fluorescence and the vibrational structure of the fluorescence emission increases. From spectroscopic, caloric and kinetic data an energy diagram of the ground and first excited states is constructed for this photo‐ and thermoreversible reaction in which the folding along the 9,10‐axis of the anthracene sceleton serves as the main reaction coordinate. Steric interaction of the bulky substituent effects a folding of the anthracene sceleton along the 9,10‐axis already in the ground state, which was confirmed by an X‐ray analysis. Thereby a transition from the excited state to a hypersurface is facilitated on which a transformation in low yield to the Dewarisomer and mainly to the start

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880111

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

年代:1984

数据来源: WILEY