bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absorption Spectra and Fluorescence Behaviour of Benzopyrylium Compounds
Authors: Haucke Günter , Czerney Peter , Igney Constance , Hartmann Horst 
Published: July 2012

AbstractAbsorption and fluorescence data of a wide variety of substituted flavylium salts and their 2‐naphthyl substituted derivatives in two solvents of different polarity are studied with respect to the influence of the flexibility of the chromophoric system both in their ground and excited states. The experimental results are in accordance with the assumption that for typical non‐bridged 2‐aryl substituted benzopyrylium salts electronic transitions occur from a distribution of non‐planar conformations of the ground state conformers to the excited state ones, which in solution tend to relax to a more planar thermically equilibrated geometry, although fluorescence rate constant data indicate that also fluorescence may originate from somewhat twisted conformations. A polar solvent supports the tendency of certain substituted molecules to occur in the excited state in a non‐fluorescent twisted configuration (TICT state). As the consequence, many flexible donor substituted benzopyrylium salts exhibit a strong decrease of their fluorescence quantum yield in polar solvents.
Kinetics of Reactions of Hydroxyl Radicals with a Series of Aliphatic Aldehydes
Authors: Dóbé S. , Khachatryan L. A. , Bérces T. 
Published: July 2012

AbstractThe kinetics of reactions of hydroxyl radical with acetaldehyde and its alkyl and halogen substituted derivatives has been investigated in the temperature range 298 – 520 K with the discharge flow/resonance fluorescence technique. The following reactions were studied and Arrhanius parameters were obtained (the preexponential factors are given in 1012 cm3 mol−1 s−1, the activation energies in kJ mol−1 units):(1) OH + CF3CHO	A = 7 (assumed;)	E = 5.9(2) OH + CCl3CHO	A = 7.1 ± 1.5	E = 5.0 ± 0.8(3) OH + CH3CHO	A = 5.1 ± 1.1	E = −1.7 ± 0.7(4) OH + (CH3)2CHCHO	A = 9.5 ± 3.0	E = −2.6 ± 1.2(5) OH + (CH3)4CCHO	A = 8 ± 4	E = −3.4 ± 1.7
Vanadia Layers Supported on Titania — an FTIR and Raman Investigation
Authors: Schraml M. , Fluhr W. , Wokaun A. , Baiker A. 
Published: July 2012

AbstractThe structure of monolayers and multilayers of V2O5 supported on TiO2 has been investigated by laser Raman spectroscopy. For the catalyst prepared by a single impregnation, disordered polymeric arrays of sixfold‐coordinated vanadium ions are detected. Second impregnation increases the number of Vv centers anchored on the support but does not create new types of structure in detectable amounts. In the third impregnation step additional layers of V2O5 are immobilized on top of the first layer, as evidenced by characteristic Raman bands at ∼996 cm−1 and 285 cm−1. The intensity of these bands from higher layers increases after the fourth impregnation; at this stage the highest specific activity of the supported catalyst for selective catalytic reduction of NO is achieved. The above conclusions are confirmed by FTIR measurements, which reveal structural differences between the vanadia species immobilized in the first and subsequent layers.
The Surface‐vacancy Bonded H2O Molecule on an Alkali Halide (100) Crystal Face and a Model of the Stimulated Contact Charging in the Electrostatic Potash Salt Processing
Authors: Ernst Lajos 
Published: July 2012

AbstractIn the electrostatic processing of raw potash salt the mutual contact charging of its components is an important step. — The contact charging may be component‐selectively stimulated by, mainly, organic acid additives, added to the salt in concentrations of 10 ppm‐s under conditions of well‐defined relative humidity of the ambient air. This technology was developed purely empirically and the mechanism of the stimulated contact charging is as yet unknown. — In the present work some light will be shed onto this mechanism. Results for the contact charging of NaCl versus KCl and versus some metals, stimulated by one of the most frequently used additives, salicylic acid, have been considered. Based on photoemission data from water adsorbed on alkali halide (100) crystal faces, it is suggested that H2O molecules, bonded in surface cation vacancies may have a role in the additive‐induced stimulation of the contact charging. On a NaCl(100) face they may capture the proton from the salicylic acid molecules forming vacancy‐trapped H3O+ ions, with their charge screened by the lattice and quasi‐free salicylate ions. The ionization energy of the latter is so small that their surplus electron may be injected readily into any of the possible contact partners. — The model describes the essential features of the contact charging stimulation of the electrostatic salt processing. The component‐selectivity is as yet not understood, however, the model supplies useful hints related to its possible causes.
Fluids in the Gravitational Field Exact Treatment of One Dimensional Systems
Authors: Schröer W. 
Published: July 2012

AbstractPartition functions and thermodynamic functions for fluids in one‐dimensional model systems interacting with a gravitational field are investigated. The intermolecular potential is chosen in a manner that only next‐neighbour particles interact, which allows for an exact evaluation of the partition function using elementary methods. The local contributions to the thermodynamic functions are determined by the local pressure. The variation of the Gibbs potential and the density as functions of the height, may show a point of inflexion as real two phase systems. This is discussed for rigid particles interacting with a square well potential, and allowed to assume two states of different lengths.
Solution Non‐Randomness and the W‐Shape Concentration Dependence of CEp for Hexafluorobenzene and Chloronaphthalene in Hydrocarbons
Authors: Andreoli‐Ball L. , Costas M. , Patterson D. , Rubio R. G. , Masegosa R. M. , Caceres M. 
Published: July 2012

AbstractExcess heat capacities, CEp have been obtained through the concentration range at 25°C for five sets of systems of type An + B: hexafluorobenzene + 2,2,4‐trimethylpentanc and 2,2,4,4,6,8,8‐heptamethylnonane; hexafluorobenzene + cyclohexane (10° W) and dicyclohexyl (W); 1‐chloronaphthalene + 2,2‐dimethylbutane, 2,2,4‐trimethylpentane (W) and 2,2,4,4,6,8,8‐heptamethylncnane (W), 1‐chloronaphthalene + n‐hexadecane; 1‐chloronaphthalene + cyclohexane and dicyclohexyl (15°, W). For the systems indicated, CEp has a W‐shape, i.e., two minima separated by a maximum or two changes of sign of the curvature. The W‐shape does not occur for hexafluorobenzene + cyclohexane at 25° but appears at 10°. Temperature and molecular size act on CEp through the degree of solution non‐randomness as indicated by GE and the concentration‐concentration correlation function, Scc which is a good predictor for the W‐shape and of the concentration at which the maximum appears. The W‐shape corresponds to an Scc value greater than 0.7 and GE > 800 J mol−1, the temperature being within 100 K of the UCST.
Calculation of Thermodynamic Properties of Binary Fluid Mixtures to High Temperatures and High Pressures
Authors: Heilig M. , Franck E. U. 
Published: July 2012

AbstractAn equation of state is presented, which permits prediction of binodal phase equilibrium surfaces and critical curves to 2000 bar and higher for binary fluid systems of partners, which differ significantly in molecular size and polarity. The procedure is an extension and improvement of an equation suggested earlier by Christoforakos and Franck. The equation of state consists of a hard body repulsion term and an additive pertubation term, which takes care of the attractive molecular interaction. For the repulsion, a Carnahan‐Starling‐One‐Fluid (CSOF) expression or suitable extensions are used, which are discussed. The attractive term uses square well potentials. Pairwise three‐body interaction as with second and third virial coefficients is introduced with a Padbapproximant (SWPA). The result is a satisfactory improvement for the calculation of the three‐dimensional binodal surface even for unsymmetric systems like water‐hexane. Critical curves and binodal surfaces, calculated and experimental, to 2500 bar and 400°C are shown for H2O‐N2, H2O ‐ CO2 and H2O ‐hexane: The necessary parameters are given. Extension to three‐phase equilibria and to ternary and quaternary systems is possible.
Induced Smectic Phases and Demixing in Mixtures of Alkanes and Other Nonmesogenic Compounds with Alkyloxy‐ and Alkyl‐cyanobiphenyls
Authors: Heuer H. , Kneppe H. , Schneider F. 
Published: July 2012

AbstractDemixing / Liquid Crystals / Phase Diagrams / Smectic Phasesn‐Heptyloxy‐ and n‐heptylcyanobiphenyl show induced smectic phases in mixtures with n‐alkanes, n‐alcohols, and n‐alkylbenzenes. Alkyloxycyanobiphenyls with shorter alkyl chains (hexyl and pentyl homologues) show miscibility gaps with an upper consolution temperature in mixtures with alkanes. It is obvious that demixing and induction of smectic phases are related processes and we believe, therefore, that the induction of smectic phases in these mixtures is a microscopical demixing in polar and non‐polar layers. X‐ray measurements in heptyloxycyanobiphenyl/tridecane mixtures support this idea.
Proteinadsorption auf alkylsubstituierten Oberflächen
Authors: Jennissen Herbert P. 
Published: July 2012

AbstractWhen confronted with the chromatographic separation of proteins one often has to cope with a large number of parameters which have either been set by the producer or oneself and which in many cases are only poorly understood. Therefore in this paper some of the fundamentals involved in the mechanism of protein adsorption on alkyl‐substituted gel surfaces will be treated. Although a large number of papers have been published on protein adsorption there is no general theory on the adsorption mechanism. The possibility of synthesizing surfaces for adsorption in a controlled way on hydrophilic gels has become feasible after the introduction of affinity chromatography. Since this technique has allowed the elucidation of a number of general mechanistic principles involved in the protein adsorption process and the corresponding sorption kinetics these results will be primarily discussed here.
Operational Modes of Chromatographic Separation Processes
Authors: Antia Firoz D. , Horváth Csaba 
Published: July 2012

AbstractAn overview of the three major operational modes of chromatography — frontal, elution and displacement — is presented with emphasis on their application to the preparative purification of biopolymers. The theoretical basis of the techniques is discussed and some of their features are illustrated with the help of computer simulated chromatograms.
The System Acetone — Water — Glycerol and its Application in Liquid‐Liquid Extraction of Proteins
Authors: Hampe Manfred J. , Schermuly Wolfgang 
Published: July 2012

AbstractAcetone and glycerol are only partially miscible at room temperature. Addition of up to 50 mole‐% water is allowed without removing the miscibility gap. By varying the water content, the polarities of the raffinate and extract phases can be adjusted to favorite conditions for the extraction of proteins. Short settling and coalescence times result from both rather high density differences and a relative high interfacial tension of up to 7 mN/m. Thus, the system can be handled in common extraction columns, which is an important process design aspect. Recovery of proteins from both phases is very simple, as this liquid‐liquid extraction system does not contain polymers of a molecular weight similar to the proteins. Distribution equilibria of peroxidase, alk. phosphatase and oxytocin will be given.
Selection of Solvents for Extractive Fermentations
Authors: Müller U. , Träger M. , Onken U. 
Published: July 2012

AbstractProduct yield in fermentation processes is often limited by product inhibition or degradation. This may be avoided by extracting the product from the broth during the fermentation. Solvents to be used in these extractive fermentations must be selective for the product and nontoxic for the microorganisms. The procedure of solvent selection is exemplified for the case of formation of cycloheximide by Streptomyces griseus. It is shown that substituted polyglycols, in particular alkylphenol polyethoxylates, are well suited to the requirements of extractive fermentations of antibiotics. In order to prevent foaming the polyglycolether chain of the molecule should contain a few propoxy groups.
Chromatographic Purification of Proteins — Support from Physico‐Chemical Research
Authors: Jagschies Günter 
Published: July 2012

AbstractOn the molecular level, physical chemistry can contribute a lot to the better understanding and easier planning of chromatographic purification steps for biological substances. Particularly in the complex situation faced in the development of purification sequences for proteins, good strategic advice is required to cut down both time and costs needed to optimize results. This article relates some results from physical chemistry to a commercial application situation, and asks for further engagement to produce even more user‐friendly results for the applicative work with chromatography.
Membrane and Adsorption Processes in the Purification of the Human Pancreatic Secretory Trypsin Inhibitor (hPSTI)
Authors: Paulsen J. , Kroner K. H. , Schütte H. , Szardenings M. , Hustedt H. 
Published: July 2012

AbstractThis paper describes a process for the purification of hPSTI from a recombinant Escherichia coli. The E. coli strain carries the hPSTI‐gene on a multicopy plasmid with the ompA‐leader‐sequence, which results in the secretion of hPSTI into the medium. The separation of the cells and the prepurification were carried out either by ultrafiltration alone, by a combination of cross‐flow microfiltration and ultrafiltration, or by a combination of flocculation and ultrafiltration. The ultrafiltration was followed by three chromatographic steps. After the final purification step hPSTI was homogeneous as judged by SDS‐PAGE (silver stain). Process scale up should be relatively simple.
Der Einfluß des Basismaterials auf die chromatographischen Eigenschaften
Authors: Eisenbeiß F. 
Published: July 2012

AbstractFor certain classes of solutes, especially for basic nitrogen compounds, an unfavorable retention behaviour is observed on alkyl‐silica stationary phases. The adsorption isotherms of such solutes are nonlinear, even at extremely low concentrations, resulting in tailing peaks and concentration dependent residence times of the peak maxima. — During the separation of biological active solutes, such chemically modified silica stationary phases can lead to unspecific interactions or irreversible adsorptions, e.g. of Proteins. — To overcome such unfavorable retention characteristics pretreatment of the silica material with alkalies and/or “end‐capping” of the alkyl silica material have been proposed. — In our work on the development of chromatographic adsorbents we first studied the influence of the silica base material in reversed phase chromatography with alkyl‐modified silicas and basic solutes. We found that the abnormal retention effects can not sufficiently be explained by the effects described in literature of e.g. unreacted silanol groups. An influence of the homogeneity of the silica surface (energetically) was found to be dominant with respect to an undisturbed retention behaviour of the related chemically modified products and compound‐products.
Use of Pervaporation in the Continuous Fermentation of Acetone, Butanol, and Ethanol
Authors: Gudernatsch W. , Mucha H. , Hofmann Th. , Strathmann H. , Chmiel H. 
Published: July 2012

AbstractThe fermentation of organic solvents represents an alternative to the petrochemical production of raw materials for the chemical industry. Because of today's low oil prices, there is no economic incentive to run a biotechnical process for the production of such substances. In near future, however, this situation will be altered in favour of biotechnology by the rising costs of crude oil. At present, new membrane separation processes are available which promise a high optimization potential for bioprocesses. The economics of such bioprocesses may considerably be enhanced by continuous production and selective product removal. — The membrane separation process pervaporation is able to enrich acetone, butanol and ethanol with respect to water. The selectivity of this process bases mainly on the superposition of the thermodynamic liquid‐vapour selectivity, the chemical affinity selectivity, and the kinetic diffusional selectivity of the polymeric materials used. Therefore, the membranes are homogeneous solution‐diffusion membranes. — Pervaporation has a property which is of special interest for a direct coupling to the fermentor: the liquid to be separated is not stressed in any chemical, thermal or mechanical way. This is not the case for all alternative separation processes. — The technical feasibility of this process combination has been demonstrated in continuous fermentation runs. An economical analysis leads to the conclusion that in particular high transmembrane fluxes lower the capital investment costs. Therefore, composite hollow fiber membranes with transmembrane fluxes in the range of 2 kg/(m2 h) and sufficient selectivities have been prepared and characterized.
Study of the Vapour of the Cr ‐ Ge, Cr ‐ Sn, and Cr ‐ Pb Systems: Vapour Composition and Dissociation Energy of the Intermetallic Molecules CrGe, CrGe2, CrSn, and CrPb
Authors: Hilpert K. , Ruthardt K. 
Published: July 2012

AbstractThe equilibrium vapour of the systems Cr ‐ Ge, Cr ‐ Sn, and Cr ‐ Pb was investigated by using Knudsen effusion mass spectrometry in the temperature ranges of 1609 ‐ 1808 K, 1409 ‐ 1641 K, and 1526 ‐ 1745 K, respectively. The gaseous heteronuclear diatomic species CrM (M = Ge, Sn, Pb) were observed in each case in addition to the species Cr, Cr2, Gen, (n = 1 – 9), Sn, (i = 1–5), and Pb, (j = 1 – 4). CrGe2 was the only heteronuclear species detected as being larger than the dimer. The appearance potentials of the ions CrGe+ and CrSn+ were determined by ionization efficiency measurements as 6.71 ± 0.02 and 6.31 ± 0.02 V, respectively. The enthalpy changes of the following dissociation and pressure‐independent isomolecular exchange reactions were evaluated according to the second‐ and third‐law methods:
equation image
The enthalpy of dissociation of the dimer M2 obtained in this work agrees excellently with the values from the literature thereby demonstrating the accuracy of the measurements. The following enthalpies of dissociation and bond energies result for the diatomic heteronuclear species and for CrGe2 in kJ mol−1:
equation image
The different values are discussed.
Thermodynamic Analysis of Extraction of MgCl2, CaCl2, BaCl2, and ZnCl2 by n‐Octanol at 298.15 K
Authors: Manzurola Emanuel , Apelblat Alexander 
Published: July 2012

AbstractPartition of MgCl2, CaCl2, BaCl2, CuCl2, ZnCl2 and water between the aqueous phase and n‐octanol at 298.15 K was considered. Extraction of the chlorides is represented by the formation of partially dissociated complexes in the organic phase. The equilibrium constant for the formation of MgCl2(H2O)6(ROH)6 is 1.0·10−5 mol−1 kg; 6.3·10−7 mol−1 kg for CaCl2(H2O)5(ROH)5; 3.1·10−5 mol−1 kg for CuCl2(H2O)4(ROH)2 and 4.1 · 10−3 mol−1 kg for ZnCl2(H2O)3(ROH)3. No detectable quantities for BaCl2 are extracted by n‐octanol. Activities of n‐octanol in the organic phase were evaluated by numerical integration of the Gibbs‐Duhem equation in the ternary systems.
Photoluminescence as an In‐Situ Technique to Determine Solid State and Surface Properties of Semiconductors in an Electrochemical Cell — Application of the “Dead Layer Model”
Authors: Smandek Bernhard , Chmiel Gerd , Gerischer Heinz 
Published: July 2012

AbstractThe quenching of the luminescence anodic of the flat band potential UFB is discussed in terms of the “dead layer” model. Properties of the bulk of the semiconductor can be deduced in this model. Near UFB, the potential dependence can only be explained, if the diffusion of minority carriers and surface recombination is properly taken into account. The relation between photoluminescence and photocurrent is discussed in the framework of this model. As examples, photoluminescence (PL) intensity and photocurrents at n‐GaP, n‐GaAs, n‐CdSe and n‐TiO2 semiconductor electrodes in dependence of the bias were measured in aqueous electrolytes. Absorption coefficients and the rate of surface recombination are derived.
Investigation of Time‐Resolved Molecular Chemiluminescence from SrO(A'1 Π, A1Σ+ ‐ X1Σ+) and Atomic Emission from Sr(53P1 ‐ 51S0) Following Pulsed Dye‐Laser Generation of Sr(53PJ) in the Presence of CO2
Authors: Husain David , Roberts Gareth 
Published: July 2012

AbstractWe present a kinetic study of chemiluminescence from SrO(A1Σ+ ‐ X1Σ+) and SrO(A'1 Π ‐ X1Σ+) following pulsed dye‐laser generation of Sr(5s5p(3PJ)), 1.807 eV above the 5s2(1S0) ground state, in the presence of CO2. This required complementary investigation of the time‐dependence of both the atomic emission profiles at the resonance wavelength of λ = 689.3 nm (Sr(5s5p(3P1)) Σ Sr(5s2(1S0)) + hv) and at wavelengths of various vibronic transitions within the A—X and A'— X band systems of SrO, together with the determination of the quantitative relationship between these using the appropriate time‐dependent equations for atomic and molecular emission. Decay profiles for Sr(53PJ) in the presence of CO2 across the temperature range T = 675—1100 K showed clear exponential decay behaviour, yielding the absolute second order rate constant for total collisional removal of the excited atoms of k1 = (4.7 ± 2.8) Σ 10−10 exp(‐ 33.3 ± 9.9 kJ mol−1 /RT) cm3 molecule −1 s−1. At elevated temperatures, the Arrhenius plot for the removal of Sr(53PJ) displayed upward curvature which is shown to be sensibly consistent with the removal of this atomic state by product SrO(X1Σ+). Chemiluminescence from transitions involving Δv sequences within SrO(A1Σ+ ‐ X1Σ+) and within the v = 0 progression of SrO(A'1Π ‐ X1Σ+) was monitored and analysed across the temperature range 900–1100 K. These molecular chemiluminescence profiles exhibited clear bi‐exponential behaviour which, when compared with the single exponential profiles for Sr(53PJ), were quantitatively shown to be consistent with the E—(E, V) transfer processes: Sr(53PJ) + SrO(X1Σ+) → SrO(A1Σ+, A'1Π, v' = n) + Sr(51S0). Vibrational excitation by this mechanism was observed up to the maximum energetically allowed by the relevant E ‐ (E, V) process. A ‐ X and A'‐ X chemiluminescence was shown to provide kinetic spectroscopic markers in the time‐domain for Sr(53PJ). Estimated vibrational temperatures within SrO(A'1II) indicated some measure of vibrational excitation accompanying energy transfer. The temperature variation of the SrO(A ‐ X) and SrO(A'‐X) emission intensity was demonstrated to be consistent with thermodynamic data for atomic strontium.
Reorientational Motions and Self‐Diffusion of Ions in (NH4)3[InF6] and (NH4)3[GaF6] Crystals as Studied by 1H and 19F Nuclear Magnetic Resonance and Electrical Conductivity Experiments
Authors: Sasaki Ayako , Furukawa Yoshihiro , Nakamura Daiyu 
Published: July 2012

AbstractThe spin‐lattice relaxation time T1 and the NMR second moment M2 of 1H and 19F nuclei were determined at various temperatures above 77 K for (NH4)3[InF6] and (NH4)3[GaF6] crystals. From the fact that small M2 values observed for both nuclei from fairly low temperatures, it is concluded that the reorientational motions of NH4+ cations and complex anions are activated even below and near room temperatures, respectively, in addition to the onset of translational self‐diffusion of the cations at higher temperatures. The motional parameters of both cations and complex anions in (NH4)3[InF6] crystals were estimated from the analysis of the temperature dependence of T1 observed for both nuclei. The occurrence of ionic self‐diffusion was confirmed by electrical conductivity measurements and the activation energy for the motion was evaluated as 38 and 37–41 kJ mol−1 for the high temperature cubic phase of (NH4)3[InF6] and (NH4)3[GaF6], respectively.