bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopic and Electrochemical Behavior of Polypyrrole Films Incorporating Methylene Blue, and Their Enhancement in Electrochromism
Authors: Amemiya T. , Itoh K. , Fujishima A. 
Published: July 2012

AbstractA cationic dye methylene blue (M. B.) was incorporated into polypyrrole (P. P.) films in the course of electrochemical polymerization of pyrrole from aqueous solution containing pyrrole, methylene blue and KCl. The films obtained were blue in color. Absorption bands of M. B. incorporated into P. P. films were broadened compared with those of M. B. in water or in a solution of pyrrole monomer. Methylene Blue incorporated into P. P. films is probably aggregated and is nearly in solid state. Molar absorption coefficient (ϵ) for M. B. incorporated into P.P. films was about half the value of ϵ for M.B. in aqueous solution. The concentration of M.B. incorporated into P.P. films was ca. 0.42—0.49 mol dm−3, while the original concentration of M.B. was ca. 1 mmol dm−3. Methylene Blue was concentrated by a factor of 420–490. The colors of the film changed reversibly to blue by oxidation and to transparent yellow by reduction. The color change was more remarkable than that of P.P. film itself. This is because M.B. was reduced to form leuco M.B. (colorless material) and was reoxidized to form M.B. The response time of color changes between blue and transparent yellow was ca. 2 s.
A Comparative Study of the Solubility and Thermodynamics of Hydrogen in Pd1‐xREx (RE = Dy, Gd, Sm, and Y; x = 0.05 and 0.08) Solid Solution Alloys
Authors: Ramaprabhu Sundara , Rajalakshmi Natarajan , Weiss Alarich 
Published: July 2012

AbstractPressure‐composition‐temperature absorption isotherms have been determined for the Pd1‐xREx (RE = Dy, Gd, Sm, and Y; x = 0.05 and 0.08) solid solution face centered cubic alloys in the pressure and temperature ranges 2 ≦ P(H2)/mbar ≦ 1000 and 473 ≦ T/K ≦ 873 using the manometric method. The partial molar enthalpy of solution of hydrogen at infinite dilution (ΔH̄0H) becomes more exothermic with increasing content of RE. The partial molar excess entropy of hydrogen solution at infinite dilution (ΔS̄E.0H) decreases with xRE. A correlation of the atomic diameter (dRE) of the substituting rare‐earth metals when in solution in palladium with ΔH̄0H and with the metal‐hydrogen interaction shows that the increase in the exothermicity of the Pd1‐xREx solid solution alloys is due to the lattice expansion and an attractive metal‐hydrogen interaction. From the correlation of ΔH̄0H with dRE of Pd1‐xREx (x = 0.05 and 0.075), ΔH̄0H of Pd1‐xREx (RE = Yb, Ho, and Eu; x = 0.05 and 0.075) solid solution alloys have been predicted. The dependence of ΔH̄0H of the “expanded” and “contracted” Pd1‐xMx alloys on the size of the octahedral interstitial hole sites (rh) occupied by hydrogen atoms is discussed.
A SANS Study of High Pressure Phase Transitions in Model Biomembranes
Authors: Winter R. , Pilgrim W.‐C. 
Published: July 2012

AbstractThe phase behaviour and thermotropic and barotropic phase transitions of different model biomembranes (DPPC, DMPC, DEPC and POPC*)), which consist of different hydrocarbon chain length and degree of unsaturation, have been investigated by small‐angle neutron scattering (SANS) as a function of temperature and pressure up to about 65°C and 3 kbar, respectively. A pressure induced structural phase transition from a liquid‐crystalline to a gel state is observed for the whole temperature range studied. The pressure of this transition increases with increasing temperature with a slope dTm/dP of about 21°C/kbar, which is common for all the different lipids investigated. The SANS experiments indicate that the effect of the two trans double bonds in DEPC and the cis double bond in the sn‐2 hydrocarbon chain of POPC enhances the conformational disorder in the hydrocarbon chains not only in the liquid‐crystalline, but also in the gel state. For DEPC and POPC the prefered structural conformation in the gel state is probably not tilted as it is in the gel state of the saturated phospholipids DMPC and DPPC. Only for DPPC multilamellar vesicles, an additional gel phase at higher pressures has been observed, which can be ascribed to an interdigitation of the hydrocarbon chains of opposing chains in the lipid bilayer system.
Incision‐Excision DNA Repair Model: A Theoretical Analysis of the Effect of Enzyme Concentrations on DNA Repair
Authors: Bhat Ramachandra , Rao Saligrama C. Subba 
Published: July 2012

AbstractRelationships between the concentration of exonuclease, DNA polymerase, and DNA ligase participating in the DNA incision‐excision repair pathway have been derived by applying steady state conditions to concentration of the species of interest. The analysis utilizes concentrations of damage excised, gapped DNA (DNAm—n) and gap filled unligated DNA (DNAm) at the steady state as the parameters to measure the extent of DNA repair. The concentrations of DNAm—n and DNAm have been expressed in terms of experimentally determinable constants such as Km, catalytic constants for the enzymes, enzyme, and substrate DNA concentrations, making it possible to verify the theoretical predictions. The analysis predicts a low ratio of exonuclease to polymerase to observe any significant repair activity, a conclusion consistent with in vitro observation of Hamilton et al. (1974) that significant DNA repair is observed when exonuclease: polymerase ratio is 0.5. The analyis predicts fairly large concentrations of DNA ligase to minimize DNAm concentration at the steady state. Under specific conditions, reversal of ligation has been predicted and has been suggested as a possible mechanism of initiation of multi‐centered DNA replication in eukaryotes. This suggestion has been substantiated by experimental demonstration that DNA nicked in the presence of DNA ligase and AMP is substrate for M. Luteus DNA polymerase but not for T4 DNA polymerase, suggesting that adenylated DNA intermediate is formed and only cleaved by 5′—3′ exonuclease which is present in vivo, and has been isolated and characterized. The relationships have been numerically evaluated for different enzyme concentrations using derived and literature values for the constants. The potential application of these results for in vitro introduction of “errors” into DNA has been indicated.
A Study of Ternary Geometrical Models
Authors: Chou Kuo‐Chih , Austin Chang Y. 
Published: July 2012

AbstractThe ternary geometrical model has been summarized, and a general formula has been presented for calculating the ternary Gibbs free energy of mixing in terms of three binary systems. This formula is applicable to any ternary model, including previous models and the many new models presented in this paper. A new nomenclature system is suggested for distinguishing all kinds of models which is very simple and convenient both for use and memory. Finally, the limiting activity coefficient of the third component in a binary solution is discussed in terms of various models.
Acid‐Base Properties of N,N‐bis‐(2‐hydroxyethyl) Glycine (Bicine) Buffers in Sea Water at Different Temperatures
Authors: El‐Harakany A. A. , Sadek H. , Taha A. A. , Khadr A. M. 
Published: July 2012

AbstractThe dissociation constant of bicinium ion in seven synthetic sea water samples at five temperatures from 25 to 45°C have been determined by emf measurements of cell:Pt, H2 (g, 1 atm)/bicine HCl (m1)bicine(m2) in SW/AgCl, Ag.The standard potentials in sea water media were determined in similar cells containing HCl. It is noticed that the pK values show small variation with temperature at a fixed salinity, and increase with incrasing the salinity of the medium up to 35%0 S. The associated the thermodynamic functions ΔG0, ΔS0 and ΔC0p for the dissociation process have been evaluated from the variation of the dissociation constant with temperature. The results are attributable to solute‐solvent interactions.
Streaming Potential Across Nafion Membranes
Authors: Scibona Giancarlo , Botrê Francesco , Botrê Claudio , Fabiani Claudio , Croce Fausto 
Published: July 2012

AbstractMembranes / Nonequilibrium Phenomena / Streaming Potential / Thermodynamics / Transport PropertiesThe streaming potential Δϕ which arises between the uni‐univalent electrolyte solutions of the same concentration separated by nafion 125 membrane in the presence of a pressure difference ΔPapplied across the membrane has been studied. Different electrolytes have been studied, namely NaCl, LiOH, NaOH, KOH and CsOH. — The quantity Δϕ/ΔPincreases in the order Li > Na > K > Cs. According to the non‐equilibrium thermodynamic theories the ratio (Δϕ/ΔP)/Jv/I), withJv (volume flow)/I(electrical current flow) the electroosmotic quantity, approaches unit.
Electrolyte and Water Osmotic Flow Coefficients in Nafion Membranes
Authors: Scibona Giancarlo , Radatti Nunzia , Botrê Claudio , Botrê Francesco , Gavelli Giorgio 
Published: July 2012

AbstractThe isothermal transport coefficients describing the NaCl, volume and water osmotic flows across Nafion membranes are studied. These transport coefficients and others already reported are used to obtain the Lij phenomenological coefficients related to the flows of ions and water in the membrane.
Ionic Mobilities at Infinite Dilution: Structural Aspects
Authors: Kessler Y. M. , Kumeev R. S. , Vaisman I. I. , Lyalina R. B. , Bratishko R. H. 
Published: July 2012

AbstractEmpirical correlations between ionic mobilities and parameters characteristic of the solvent molecules motions for a variety of single ions and 1‐1 electrolytes at infinite dilution in 19 one‐component solvents and 8 aqueous‐nonaqueous mixed solvents are found, presented and discussed. The parameters are the self‐diffusion coefficient, the dipole relaxation time, the rotational correlation time of various NMR vectors, and the residence time of solvent molecules in the first ion solvation shell. The residual friction coefficients are considered in a more theoretical vein.
Side Reactions in Electroless Copper Solutions with Formaldehyde as Reducing Agent
Authors: van Meerakker J. E. A. M. , Scholtens E. 
Published: July 2012

AbstractIn alkaline electroless copper solutions with formaldehyde as reducing agent, side reactions between formaldehyde and hydroxide occur. In solutions of formaldehyde and sodium hydroxide below 70°C the only reaction found is the Cannizzaro reaction. The rate constant of this reaction was determined at different temperatures, yielding an activation energy of 87 kJ·mol−1. An increase of Na+ concentration leads to an increase of the rate of this reaction. The nature of the anion had no effect. Above 70°C a second reaction proceeds: aldol condensation. Oxygen suppletion inhibits the aldol condensation. Analyses of continuously operating electroless copper solutions showed that the kinetics found in alkaline HCHO solutions could be applied directly to real plating solutions.
Efficient Singlet Energy Migration in Amorphous Copolymer Film Having No Excimer Forming Site: Poly[2‐(9‐carbazolyl)ethyl methacrylate‐co‐methyl methacrylate]
Authors: Ohmori Satoru , Ito Shinzaburo , Yamamoto Masahide 
Published: July 2012

AbstractEnergy Transfer / Fluorescence / PolymersSinglet energy migration in the solid state for the homopolymer of 2‐(9‐carbazolyl)ethyl methacrylate and the copolymers with methyl methacrylate was investigated using perylene as an acceptor molecule. In this system, the carbazole (Cz) chromophore is dispersed uniformly even in the homopolymer and a deep trap is not formed. The fluorescence spectra and their decays were measured for these samples and the energy migration was analyzed on the basis of three models, i.e., random hopping model, Smoluchowski diffusion model, and Yokota‐Tanimoto (Y‐T) Padé model. Among these models, the Y‐T Padé model gave the most reliable diffusion coefficient. The diffusion coefficient was obtained in a wide range of carbazole concentrations from 0.14 to 4.4 mol/l and we obtained the following conclusions.1. The energy diffusion coefficient D is proportional to [Cz]4/3 as predicted from the Förster mechanism even for the samples of Cz concentration higher than 1 mol/l.2. At a low temperature, the energy migration rate becomes slow owing to shallow traps. The activation energy in a low temperature region is about 4 kJ/mol.3. Fast energy migration (D = 2.0·10−4 cm2/s) was found for the polymers whose concentration of Cz‐chromophore is high, but do not form excimer.
Collision‐Induced Intersystem Crossing in CH2 (ã 1A1): A Quantitative Analysis Using the Mixed‐State Model
Authors: Bley U. , Koch M. , Temps F. , Wagner H. Gg. 
Published: July 2012

AbstractThe mechanism of collision‐induced intersystem crossing (ISC) in CH2 from the ã 1A1 first excited singlet to the X̃ 3B1, triplet ground electronic state, CH2 (ã) + M → CH2 (X̃) + M, is investigated. Collisional ISC rate constants are calculated for four selected collider gases, M = He, Ar, N2, and CH4, using the “mixed‐state” model of Freed and Gelbart. The most important triplet‐perturbed rotational levels in the ã‐state are identified from the spectroscopic data reported in the literature. The rates of rotational relaxation processes, which according to the model effectively govern the collision‐induced ISC, are determined by studying the collision broadening of CH2 (X̃) Far Infrared Laser Magnetic Resonance (FIR‐LMR) transitions. The collisional ISC rate constants for CH2 in the ortho nuclear spin modification are calculated to be kISC = 1.4 · 1012, 4.0 · 1012, 7.8 · 1012, and 6.6 · 1012 cm3&sol;mol · s for M = He, Ar, N2, and CH4, respectively. The results are in good agreement with published experimental rate constants.
An Investigation of the Reaction Between CH3 Radicals and Acetaldehyde‐d4 at High Temperatures
Authors: Klatt M. , Wagner H. Gg. 
Published: July 2012

AbstractThe reaction between CH3 radicals and acetaldehyde‐d4 was investigated behind incident shock waves at temperatures between 1050 and 1190 K and total densities about 2 · 1−6 mol cm−3. — The consumption of CH3 was followed by time‐resolved UV‐absorption measurements at λ = 216.5 nm. The measurements were carried out with perdeuterated acetaldehyde. — A rate constant of 1.1 · 1011 cm3 mole−1 s−1 for the reactionCH3 + CD3 → CH3 + CD3CO	(1)at temperatures around 1100 K was determined.
Radiationless Deactivation of the Fluorescent State of 9‐Methoxyanthracene and of Related meso‐Substituted Anthracenes
Authors: Schoof Sabine , Güsten Hans 
Published: July 2012

AbstractThe temperature dependence of the fluorescence quantum yield, the fluorescence decay time, and the triplet‐triplet absorption spectrum of 9‐methoxyanthracene have been measured in n‐heptane. The sum of the fluorescence quantum yield and the quantum yield for intersystem crossing of 9‐methoxyanthracene and two partially deuterated 9‐methoxyanthracenes at room temperature is only ∼0.60. While the fluorescence quantum yield in methyl methacrylate has nearly the same value as in n‐heptane, the fluorescence quantum yield is twice as high in the rigid matrix of PMMA. When passing from fluid solutions to the PMMA matrix, a dramatic increase in the fluorescence quantum yield can be demonstrated for the following meso‐substituted anthracenes: 9.‐tert.butyl‐, 9‐cyano, 10‐tert.butyl‐ and 9‐cyano,10‐methoxyanthracene. Anthracene, 9‐chloro‐ and 9‐phenylanthracene do not show neither this matrix effect nor an anomalous temperature dependence on the fluorescence quantum yield in solution. — The anomalous temperature dependence of the fluorescence quantum yield and fluorescence decay time and the increase in fluorescence quantum yield in the rigid PMMA matrix of 9‐methoxy‐and some meso‐substituted anthracenes indicate that at moderate temperatures a very fast S1→ S0internal conversion is operative which competes with intersystem crossing.
Transient SANS Studies on p‐Tetrafluorethylen (p‐TFE)
Authors: Baumann J. , Kalus J. , Neubauer G. , Hoffmann H. , Ibel K. 
Published: July 2012

AbstractTime dependent anisotropic small‐angle neutron scattering (SANS) patterns of p‐TFE fibrilles are presented. In the experiment the fibrilles were exposed to a parallel AC‐electric field in which the on and off cycle time had been adjusted to the orientation time of the fibrilles. The time resolution of the experiment was 40 ms. By an analysis of the time evolution of the SANS pattern relaxation times for alignment τ1 and randomisation τ2 were deduced. Both times, being equal within the error bars, are around 150 ns. The scattering curve for the fibrilles could only be fitted with the assumption of considerable polydispersity of their diameter.
Absolute Measurements of the Thermal Conductivity of Some Aqueous Chloride Salt Solutions
Authors: Assael M. J. , Charitidou E. , Stassis J. Ch. , Wakeham W. A. 
Published: July 2012

AbstractNew absolute measurements of the thermal conductivity of aqueous NaCl, KCl and CaCl2 solutions are presented. The concentrations studied were 10% and 20% by weight of NaCl and KCl, and 10, 20 and 30% by weight of CaCl2. The measurements were performed in a transient hot‐wire apparatus employing two thin tantalum wires coated with an anodic tantalum pentoxide insulation layer. The temperature range examined was 290 to 345 K and the pressure was atmospheric. The uncertainty of the measurements is estimated to be ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. — Existing correlations for the thermal conductivity of aqueous inorganic salt solutions are also examined. The measurements have been used to develop a simple consistent correlative and predictive scheme that allows the correlation of the thermal conductivity of these solutions with an uncertainty of ±0.7% and the prediction of the thermal conductivity to high pressures with an uncertainty of ±2.5%.
Acid‐Base‐Titration of a System Subdivided by a Semipermeable Membrane
Authors: Schlögl Reinhard W. 
Published: July 2012

AbstractThe theory of acid‐base‐titration is extended to systems subdivided into two compartments by a semipermeable membrane. Equal temperature of the outer phases, as well as ideal solutions are assumed. The membrane shall be impermeable to the ions constituting the “precipitation membrane”. It is shown that a neutral salt can adequately titrate the system.
Morphology of Paraphenylenediamine‐Aniline Conducting Copolymers
Authors: Mailhé‐Randolph C , McEvoy A. J. 
Published: July 2012

AbstractElectrooxidation of aniline on conductive substrates, in an aqueous chloride electrolyte at low pH, produces adherent polyaniline (PANI) films. In the initial stage of polymerization the films exhibit a uniform globular microstructure which evolves to a fibrous deposit for thicker films. Although paraphenylenediamine (PPDA) itself does not electropolymerise to give a well defined electroactive film, in small admixtures it can modify dramatically the morphology of the copolymer with aniline. PPDA evidently promoted nucleation and cross‐linking during the electropolymerisation. Electrochemical characteristics and SEM micrographs of the doped PANI films are presented.
A Study on the 79Br Nuclear Quadrupole Spin‐Lattice Relaxation Times Affected by the Soft Acoustic Mode in Anilinium Bromide Crystals
Authors: Horiuchi Keizo , Nakamura Daiyu 
Published: July 2012

AbstractThe nuclear quadrupole spin‐lattice relaxation time T1Q, spin‐spin relaxation time T2Q, and NQR linewidth of 79Br in anilinium bromide were determined at various temperatures between 100 and 445 K. An unusual temperature variation of T1Q was observed over a wide range of temperature far below and also above the phase transition already reported, in addition to the normal temperature dependence (T−11Q α T2) due to lattice vibrations activated in crystals. The mechanism of the occurrence of the T1Q anomaly observed is explained in terms of the soft acoustic mode already reported to exist.
A New HeNe‐Laser Excitable Fluorescent Surfactant Probe
Authors: Kessler Manfred A. , Wolfbeis Otto S. 
Published: July 2012

AbstractThe fluorescence properties of four carbocyanine‐type probes which can be excited by the HeNe‐laser are investigated. Their fluorescence emission is red shifted and drastically enhanced in solutions of non‐ionic and cationic detergents at above the critical micellar concentration (CMC) as a result of the adsorption of the dye at the surface of the micelles. Since, at the same time, the absorption band is also shifted towards the 633 nm line, a drastic enhancement of the absorbance is also observed upon micellization. The most proper dye (2a) provides a fivefold increase of the 633 nm absorption in micellar solution of Triton X100 as compared to detergent solutions of below the CMC. It is shown that the CMC can be determined from the emission data of detergent solutions. The experimental data obtained with probe 2a are in agreement with the published values for a cationic, a neutral, and an anionic model detergent. The dyes (in particular 2a) are therefore considered as new useful probes for a sensitive determination of the CMC by laser fluorescence spectroscopy.
Structural Properties of Proteins as a Basis for Separation
Authors: Belfort Georges 
Published: July 2012

AbstractAs more and purer complex pharmacological proteins such as factor VIII, erythropoietin, colony stimulating factors, human growth factors, interferons, interleukins, monoclonal antibodies, and plasminogen activators need to be produced, increasing attention will be devoted to their recovery. In this brief review we focus on the molecular properties of proteins that are commonly exploited for their bioseparation. A formalism is then presented illustrating how structure (primary through quartenary) defines the properties of a protein and hence establishes the dominant interactions that determine the most appropriate group of separation processes that need to be considered for the recovery of the desired protein. A detailed example is used to illustrate this for electrostatic interactions during the adsorption of ribonuclease A onto mica. The paper concludes with the assertion that recombinant DNA techniques will play an increasingly important role in protein separations. These methods are already being used to increase the concentration and purity of a desired heterologous protein. Excretion of foreign proteins from the cytoplasmic space of E. coli into the medium is now a reality. Polypeptide marker fusion systems have also been used to facilitate excretion, purification, and identification of a desired protein. Clearly, combining rDNA techniques with biospecific affinity interactions augurs well for the future of efficient and highly selective separation processes.
Bioseparations, Especially by Hollow Fibers
Authors: Cussler E. L. 
Published: July 2012

AbstractDownstream processing in biotechnology is best idealized as a four step process: removal of insolubles, isolation, purification, and polishing. The first and last steps are relatively easily achieved; the isolation and purification steps include most of the potential problems. While purification has often been presumed the most difficult, isolation may involve the greatest cost, presumably because it involves getting a small volume of concentrate from a large volume of feed. Both purification and isolation can sometimes use hollow fibers for extraction and chromatography.