摘要:

AbstractBaSO4precipitation zones with membrane properties (“conditioned state”: characteristic values of membrane potential, non‐ohmic electric current‐voltage characteristic) are generated by interdiffusion of iso‐osmotic aqueous solutions of BaCl2and Na2SO4within cellophane skins. In the “conditioned state” they are found to be impermeable to glucose, sucrose, and raffinose. Osmotic differences of these substances between the bulk phases as well as osmotic differences of BaCl2and Na2SO4cause an osmotic volume flow across the precipitation zone from which the hydrodynamic permeability of the precipitation membrane imbedded within cellophane skin can be calculated. The hydrodynamic permeability of a cellophane skin containing a BaSO4precipitation zone in its “conditioned state” is smaller by a factor of more than 10 compared with that of an untreated cellophane skin. A precipitation zone looses its characteristic properties (“deconditioned state”) if the ions forming the precipitate (Ba++, SO4–) are removed from the bulk phases. This triggers changes of the properties of the surface of the BaSO4crystallites and Ostwald ripening processes set in. Such a precipitation zone becomes permeable to glucose, sucrose, and raffinose. In the “deconditioned state” the hydrodynamic permeability of precipitations zones approaches nearly the value of an untreated cellophane skin. Adding again Ba+ +and SO4–ions to the bulk phase regenerates the electrochemical and osmotic properties of the precipitation zone. Low angle scattering patterns of synchroton radiation of freeze dried cellulose skins containing a BaSO4precipitation zone in its “conditioned state” are analyzed in terms of a random structure model. It is found that the correlation length of local electron density fluctuations has a value of about 6 nm. This reflects the tight packing of BaSO4crystallites forming a precipitat

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950501

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe photochromic responses of mixed WO3– MoO3thin films subjecting to UV irradiation were investigated in reducing environments, and they were compared with those of WO3and MoO3thin films. It was found that the photochromism of mixed 92% WO 3 −8% MoO3thin film in ethanol vapor was significantly enhanced than that of WO3or MoO3. The associated change in the absorbance (ΔABS) of the mixed‐oxide film was about 1.5 times that of the WO3film, and about 2.7 times that of th

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950502

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

年代:1991

数据来源: WILEY

摘要:

AbstractMoO3thin films after irradiated with a UV light showed enhancement in electrochromism when compared to the non‐irradiated ones. It was found that the change in absorbance for the irradiated portion was as large as six times that of the non‐irradiated portion of a sample. This enhancement in electrochromism may be due to the differences in the electrical conductivity and film crystallinity between the irradiated and non‐irradiated sa

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950503

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe interaction of UHV cleaved FeS2(100) surfaces with adsorbed H2O as an electron donor and adsorbed Br2as an electron acceptor has been studied with LEED, LEISS, UPS, and XPS to simulate semiconductor/electrolyte interfaces in UHV. The (100) cleavage plane is characterized by a c(2 × 2) or p(√2 × 2)R 45° LEED pattern which is interpreted in terms of the unreconstructed FeS2surface. H2O is molecularly adsorbed at low temperatures (100 K) and desorbs completely at room temperature (RT). LEIS‐spectra taken at low coverages (<0.5 ML) suggest a preferential interaction with the Fe sites. Br2is ionosorbed at low coverages (<0.5 ML) as well interacting specifically with Fe‐sites. It is molecularly adsorbed at higher coverages. The ionosorbed part does not desorb at RT. The behavior of specific adsorption is related to the electronic nature of the band edges which are derived from Fe

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950504

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

年代:1991

数据来源: WILEY

摘要:

AbstractA new numerical algorythm was used to calculate the electrostatic interaction forces between regularly shaped particles bearing thin double‐layers immersed in an arbitrary electrolyte. Our numerical procedure enabled the solution of the nonlinear one‐dimensional Poisson‐Boltzmann (PB) equation in which the excluded volume effect is quantitatively considered for an arbitrary surface charge. Using these onedimensional solutions (parallel‐plate system) the electrostatic force of interaction between regularly shaped particles was calculated according to the modified Derjaguin summation method. Calculations were performed for plates and particles bearing dissimilar surface charge (heterointeractions) for simple electrolytes and electrolyte mixtures with constant charge and constant potential boundary conditions. From these solutions the range of validity of previously derived limiting analytical expressions was estimated. A significant role of trace amounts of higher valency electrolytes decreasing considerably the interaction force was co

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950505

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe electromagnetic response of a homogeneous, electrically small ellipsoid made of a general linear bianisotropic material immersed in a chiral fluid has been obtained.

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950506

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

年代:1991

数据来源: WILEY

摘要:

AbstractHigh‐pressure neutron diffraction measurements on liquid and fluid deuterium chloride are reported. Temperature and density were varied over a broad range involving pressures up to nearly 2000 bars. The employed high‐pressure equipment and the pressure cell are presented. Data evaluation up to the corrected structure factor is described. Several correction procedures for multiple scattering and self‐absorption and for inelastic scattering effects are discussed with regard to their applicability in the present case. The intramolecular structure is determined by fitting to the total differential cross section as well as to the separated intramolecular cross section. A separation of the intra‐ and the intermolecular contribution is done by means of Fourier transformation. The dependence of the intermolecular radial distribution function on temperature and density i

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950507

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

年代:1991

数据来源: WILEY

摘要:

AbstractAt 25°C the complex (dielectric) permittivity of the system tert.‐butanol/water has been measured as a function of frequencyv(3 MHz ≦v≦ 70 GHz) and mole fraction x (0 ≦ × ≦ 1). Different relaxation functions are fitted to the measured spectra. It is found that within the complete composition range an empirical function is appropriate, which is based on an unsymmetric continuous distribution of relaxation times. Other than expected on grounds of previous light scattering and ultrasonic absorption studies there are neither indications for the formation of microphases nor for special hydrophobic hydration effects. The parameters of the relaxation spectral function are discussed to yield information on the liquid structure and molecular motions of the mixtures. Comparison is made with further aqueous systems which had been measured over a wide composition range, in particular other alcohol/water mixtures but also aqueous solutions of nearly non‐dipolar quinoxaline and of dimet

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950508

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe dynamical behaviour of crown ether 18‐crown‐6 in water has been investigated over the whole concentration range by incoherent quasielastic neutron scattering using the high resolution backscattering spectrometer BSS1 and the time‐of‐flight instrument SV22 at the research reactor FRJ2 in Jülich. In addition we have determined the dynamic viscosities and the mass densities of this binary system. Evaluation of the neutron scattering data by use of appropriate diffusion models gives information about the temporal and spatial development of translational, rotational and conformational motion of 18‐crown‐6. The decrease of the measured dynamical quantities on addition of water up to a concentration of 50 mole‐% suggests the formation of a 1:1 crown ether‐water adduct. Addition of more water yields a rapid increase of the translational diffusion coefficient and a decrease

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950509

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

年代:1991

数据来源: WILEY

摘要:

AbstractAbsorption coefficients for the nitrate (NO3) radical in aqueous solution have been determined using multichannel optical absorption in the range λ = 540 – 760 nm. NO3radicals were generated by excimer laser photolysis of (NH4)2[Ce(NO3)6] at 351 nm. For the quantum yield of NO3formation from this process a value of ϕ(NO3) = (0.85 ± 0.09) has been determined using a Br−scavenging technique. With this value the absolute absorption coefficient of NO3at the maximum of its absorption at 635 nm was found as ϵ = (527 ± 105) l/mol · cm (base 10). Absorption coefficient data for the range 540–760 nm are presented in 2 nm intervals. The oscillator strength of the (0‐0) band transition near 665 nm has been calculated to be (1.6 ± 0.5) · 10−3in reasonable agreement with th

ISSN:0005-9021    

DOI:10.1002/bbpc.19910950510

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

年代:1991

数据来源: WILEY