bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure, Hydrogen Bonds and Phase Transition in Ethylenediammonium Hexachlorometallates, [H3N(CH2)2NH3]2⊕ [XCI6]2⊖, X = Sn, Pb, Te, Pt. A 35Cl NQR and X‐ray Diffraction Study
Authors: Borchers Dirk , Weiss Alarich 
Published: July 2012

AbstractThe crystal structure and chemical bond of ethylenediammonium hexachlorometallates, [H3N(CH2)2NH3]2⊕ [XCl6]2⊖, X = Sn, Pb, Te, Pt, was studied by X‐ray diffraction and 35CI NQR. [H3N(CH2)2NH3]2⊕ [SnCl6]2⊖ crystallizes with the space group Ci1‐P1, Z = 1. The lattice constants are a = 704.4 pm, b = 711.2 pm, c = 743.7 pm, α = 67.537°, β = 65.341°, γ = 60.407°. The crystal structure was determined. It is described by a deformed CsCl‐type lattice and the hydrogen bonds NH … Cl cause a weak layer type solid. The compounds with X = Sn, Pb, Te, Pt are isotypic and the lattice constants are given. A three line 35CI NQR spectrum is observed for all compounds in the temperature range 77 ≤ T/K ≤ decomposition temperature, in agreement with the crystal structure. The hexachloroplatinate experiences a phase transition at T = 357.2 K, the high temperature phase I being of higher symmetry than P1. This shows up in the two line 35CI NQR spectrum in phase I. Isotope exchange H→D at the ammonium groups influences Tc and v(35CI) slightly, an observation, which favours the assumption of rather weak hydrogen bonds N·H…Cl.
Wet Salt Melts—A Reaction Medium Suitable for the Preparation of Metastable Oxides and Hydroxides?
Authors: Harms Gerd J. , Gunβer Walter 
Published: July 2012

AbstractSalt melts with a water content from 1 to 50 mole percent, representing systems between salt fluxes and hydrothermal solutions, have not been used for preparation purposes yet. We employed such systems with alkali nitrate and chloride as salt components on the preparation of hydrous gallium oxides. In this way besides α‐GaOOH and β‐Ga2O3, the metastable polymorphs α‐Ga2O3 and ε‐Ga2O3 as well as 5Ga2O3 · H2O and furthermore oxides with the β(2B)‐alumina and the spinel structure are formed. Composition and structure of the product phases are mainly ruled by temperature and molar salt/water ratio. With T < 450°C and pH2o < 10 bars the reaction conditions are rather mild compared with those of hydrothermal growth or flux growth, respectively. The mechanism of the hydrous oxide formation and the applicability of the new method to other oxide systems are discussed shortly.
Ionic Transport Across Porous Charged Membranes and the Goldman Constant Field Assumption
Authors: Pellicer J. , Mafé S. , Aguilella V. M. 
Published: July 2012

AbstractStarting from a simple theoretical model based on Nernst‐Planck flux equations and the Donnan equilibrium relationship, the ionic transport across a porous, charged membrane is analysed and conditions are given which make exact the so‐called “constant field assumption”. The validity of the reported results is later verified in the case of a well‐known problem: the ionic transport across a cation‐exchange membrane under bi‐ionic conditions.
Transport Properties of Liquids. V. Self Diffusion, Viscosity, and Mass Density of Ellipsoidal Shaped Molecules in the Pure Liquid Phase
Authors: Fischer Jens , Weiss Alarich 
Published: July 2012

AbstractFor ellipsoidal shaped molecules, disk like molecules, and spherical molecules (cycloalkanes, methylcyclosiloxanes, bi‐ and tricyclic alkanes, carboxylic acids, and aromates) the self diffusion coefficientD, the dynamical viscosity η, and the mass density ϱ were measured (280 ≤T/K ≤ 360).—Pulsed gradient high resolution1H NMR spin echo spectroscopy at a field of 4.78 T was applied for the measurements ofD(T). η was determined via a Ubbelohde viscosimeter and ρ via a vibrating densitometer.—The free volume theory of Cohen and Turnbull (CT) was extended to molecules of ellipsoidal shape. The extended CT model describes the self diffusion of the 23 compounds examined here in a satisfactory way. Experimental data forD(T), η(T), and ϱ(T) are described in the temperature range studied by appropriate polynomials, too. The activation energies of the transport processes are found from an Arrhenius type Ansatz. They are also discussed on hand of the hybrid equation of Macedo and Litovitz.
Electronic Structures of the Mono‐ and Tricarbonyl of Cu and Ag
Authors: Tse John S. 
Published: July 2012

AbstractAb initio molecular orbital calculations have been performed on the low lying states of the mono‐ and tri‐carbonyls of Cu and Ag. Linear monocarbonyls are found to have a 2Σ+ ground state with the unpaired electron residing mainly in a metal s orbital polarized away from the CO ligand. The tricarbonyls prefer a trigonal planar 2A″2 ground state with the unpaired spin population predominantly in a metal pz orbital. The alternative 2A'1 state where the single electron occupying the metal s orbital is slightly higher in energy. The energy difference between the 2A″2 and 2A'1 states are much smaller in Ag(CO)3 than they are in Cu(CO)3.
The Oscillatory Decomposition of H2O2 Monitored by the Potentiometric Method with Pt and Ag+/S2‐ Indicator Electrode
Authors: Anić S. , Kolar‐Anić L. J. 
Published: July 2012

AbstractThe oscillatory decomposition of hydrogen peroxide in the presence of potassium iodate and sulphuric acid is analysed potentiometrically with the aid of Pt and Ag+/S2‐ electrodes. Data pertaining to the concentration changes of iodide and hydrogen peroxide and to the oxido‐reduction evolution of the system in its various characteristic states are thus obtained. It is established that the concentration ratio of these two substances is approximately constant at the boundaries of the oscillatory range when the concentration of the hydrogen peroxide in the system exceeds the value necessary for regular oscillations. The rate constant of the disappearance of iodide in the system in the region of smooth catalysis is somewhat smaller than rate constant of the overall decomposition of the hydrogen peroxide.
Separation Mechanism of a Photoinduced Electron‐Hole Pair in Metal‐Loaded Semiconductor Powders
Authors: Nosaka Yoshio , Ishizuka Yutaka , Miyama Hajive 
Published: July 2012

AbstractPhotocatalytic activities of metal loaded CdS and p‐GaP semiconductor powders were measured for ammonia production from aqueous N−3 solution and hydrogen evolution from ethanol‐water mixture. The higher activity was obtained for the CdS loaded with the metal having a higher work function. On the other hand, the metal‐loading on p‐GaP powders showed a slight increase in the activity with loading lower work function metals. The numerical calculation for two‐dimensional Poisson equation shows that the electric field gradient is formed around the metal spots. This field gradient causes electrons to be captured by the metal, and holes to be collected on the semiconductor‐solution interface between the metal spots.
Preparation and Electrochemical Behaviour of Doped Manganese Dioxide
Authors: Bauer Jürgen , Buss Dieter H. , Glemser Oskar 
Published: July 2012

AbstractDoped manganese dioxides were prepared by homogeneous hydrolysis and oxidation of manganese(III)‐compounds. Three sets of conditions were employed: (a) oxidation and hydrolysis in acid medium, (b) oxidation and hydrolysis in basic medium, (c) oxidation in acid and hydrolysis in basic medium. Doping elements were Mg, Ca, Sr, Ba, Al, Fe, Ni, Zn. All precipitates were essentially amorphous. The discharge capacity of products from (a) varied between 44 and 48 mAh/g except for the Al‐doped product, which, as the number of cycles increases, displays a continuous improvement of capacity up to 65 mAh/g, producing a hard discharge curve. Products from (c) are remarkable with respect to both discharge capacity and cycle stability; the product doped with Ba had 91 mAh/g discharge capacity and this value remained constant for 320 cycles.
Diffusion of Hydrogen Defects in BaTiO3 Ceramics and SrTiO3 Single Crystals
Authors: Waser Rainer 
Published: July 2012

AbstractThe deuteron diffusion in acceptor‐doped barium titanate ceramics is studied as a function of the dopant concentration (0 to 1.0 mol% Ni) using a thermal desorption technique. The 0.1 mol% Ni‐doped sample shows a diffusion coefficient D = 290 cm2 s−1 · exp(‐151 kj mol−1/RT). The dopant concentration has only little influence on the deuteron diffusion rate in the temperature range considered (approx. 850 K. to 1150 K). The results are discussed with reference to the diffusion coefficient of oxygen vacancies. In addition, an IR spectroscopic study of the deuteron/proton exchange in SrTiO3 single crystals is reported. The hydrogen defect diffusion data obtained by this technique are compared to the results of the thermal desorption study.
Defect Structure and Transport Properties of Manganese Oxides: (III) Relaxation Kinetics of Manganosite (Mn1‐ΔO) in CO/CO2 Gas Mixtures
Authors: Franke P. , Dieckmann R. 
Published: July 2012

AbstractThe kinetics of point defect relaxation in manganosite after sudden changes of the oxygen activity in a surrounding CO/CO2 gas atmosphere have been studied by means of electrical conductivity measurements on single crystalline needle‐like samples at 1000°C. The results show that at very low oxygen activity the relaxation process is essentially controlled by diffusion processes in the bulk, but that at high oxygen activity the oxygen transfer at the manganosite/gas interface determines the kinetics.
A comparative study of anodic charge‐transfer kinetics at dark p‐type GaAs and at illuminated n‐type GaAs electrodes in aqueous and in mixed aqueous‐methanolic solutions
Authors: Lingier S. , Gomes W. P. , Cardon F. 
Published: July 2012

AbstractThe kinetics of the competition between the anodic decomposition of the dark p‐GaAs electrode and the anodic oxidation of TMPD have been studied in aqueous and in mixed aqueous‐methanolic medium by rotating ring‐disk voltammetry. The results were found to be qualitatively and quantitatively in agreement with those, previously obtained from an analogous study on the n‐GaAs photoanode, and confirm the conclusion that the mechanism depends on the medium. The latter point is further supported by the relationships between anodic current density, potential and TMPD concentration, observed at p‐GaAs. The accepted competition mechanisms allow to propose structures for the surface decomposition intermediates of GaAs involved. The value of the rate constant for the first decomposition step of GaAs is determined from current density‐potential and impedance measurements on p‐type electrodes and is discussed.
Composition dependent electronic conductivities and hall coefficients of mixed ionic‐electronic conductors. Part II: The high‐temperature phase of silver selenide
Authors: Sohège J. , Funke K. 
Published: July 2012

AbstractThe electronic conductivity, σe, and the Hall coefficient, RH, of the high‐temperature phase of silver selenide, β‐Ag2+δSe, are experimentally determined at temperatures T between 170° and 300° and at values of σ covering the entire stability range. The change of composition is achieved and monitored by in situ coulometric titration. The electronic transport data yield the following results. The conduction band is harmonic, whereas the valence band is anharmonic. Mobility and relaxation time of conduction‐band electrons vary with temperature as T−1 and with the electronic energy as ϵ−1/2. This is the behaviour normally assumed to be valid, if the relaxation is due to the scattering of electrons by acoustic phonons.
Solubility of hydrogen in Pd2Er5, Pd2Er3, PdEr, Pd4Er3, and Pd3Er: Thermodynamics of Pd —Er —H Systems
Authors: Ramaprabhu Sundara , Weiss Alarich 
Published: July 2012

AbstractThe solubility of hydrogen in the intermetallic compounds Pd2Er5, Pd2Er3, PdEr, Pd4Er3, and Pd3Er has been measured by the pressure reduction method in the ranges 1 ≤ P/mbar ≤ 1000 and 473 ≤ T/K ≤ 1148. The partial molar enthalpy of solution at infinite dilution (ΔH0H) and the partial molar excess entropy of solution at infinite dilution (ΔSE0H) have been determined from the α‐phase solubility isotherms. |H0H| is found to decrease with increase of palladium content in the following order: Pd2Er5(‐71.8 kJ ‐ mol−1), Pd2Er3 (–61.0 kJ ‐ mol−1), PdEr (‐18.9 kJ · mol−1), and Pd4Er3 (‐9.2 kJ · mol−1). In Pd3Er, however, ΔH0H is −45.1 kJ · mol−1. The extrapolation of ΔH0H, =f(xEr) in solid solution of erbium in palladium to xEr = 0.25 gives ΔH0H = –37.3 kJ · mol−1, whereas, ΔH0H = –45.1 kJ · mol−1 is observed in Pd3Er, indicating that the formation of the ordered structure results in an additional increase of exothermicity of hydrogen absorption reaction. The increase of exothermicity of hydrogen absorption in Pd3Er when compared to PdEr may be attributed to the smaller octahedral interstitial hole size. ΔSE0H is found to lie between −59.0 and −64.0 J · K−1 · mol−1. Pd2Er5, Pd2Er3, and PdEr show decomposition reactions by which erbium hydride and the next intermetallic compound in the Pd–Er phase diagram with less content of erbium are formed. The decomposition pressure at any temperature is found to increase with increase of palladium content, suggesting that the stability of the compounds increases with increase of palladium content at least till PdEr. The heats of formation of Pd2Er3 and Pd4Er3 have been obtained from the present work and compared with the calculated ones.
Crystallization of cold condensed silver chloride
Authors: Zuber Ralf , Weil Konrad G. 
Published: July 2012

AbstractUV/VIS spectroscopic studies with cold condensed silver chloride films are reported. During annealing of these films, an exciton band grows out of an initially contourless broad absorption edge. From the temperature dependence and from the time behavior of this absorption it is concluded, that the noncrystalline state of the chloride, which is formed during the condensation, is a metastable phase. The transition to the crystalline state is of an order > 1. A small red shift of the maximum of the exciton band during the transformation indicates that the crystalline nuclei grow during this process.
Biological applications of ultrafast laser methods
Authors: Hochstrasser R. M. 
Published: July 2012

AbstractIt becomes increasingly evident that pulsed laser methods will contribute greatly to understanding fundamental processes in biological systems. It is now possible to perform many types of electronic and vibrational spectroscopy on the femtosecond timescale. Such measurements provide new knowledge of molecular and protein motion, transient structures and of primary photoprocesses. —Research on understanding dynamical and structural properties involved in reactions of heme proteins with ligands will be reviewed with emphasis on the interplay between advances in laser methods and the gradual refinement of our picture of the operation of these proteins.
Laser microsurgery on pollen tubes
Authors: Schütze K. , Reiss H.‐D. , Becker H. , Monajembashi S. , Greulich K. O. 
Published: July 2012

AbstractThe high three dimensional and temporal resolution of a pulsed UV‐laser microbeam is used to manipulate subcellular structures in pollen tubes without destroying cell viability. A single pulse of about 1 μm diameter, focussed into the depth of the tube, stops immediately cytoplasmic streaming in a region of 50 μm around the irradiated spot. Calcium is released from intracellular stores within the irradiated area, as monitored by the fluorescence of the calcium sensitive dye quin‐2. The observed effects can be explained by a disruption of calcium storing organelles. The released calcium ions can depolymerize microfilaments and thus stop organelle movement. Furthermore, organelle zonation can be disturbed with a few laser pulses near the tip region. This may be due to the disturbance of the electric field, that is thought to maintain tube organization.
Optical trapping and manipulation of single living cells using infra‐red laser beams
Authors: Ashkin A. , Dziedzic J. M. 
Published: July 2012

AbstractIt is possible to make optical traps for small biological particles using the forces of radiation pressure from a single highly focused laser beam. Laser traps are localized to a few cubic μm and are capable of trapping particles from 10's of nm up to 10's of μm. With infrared laser beams of 1.06 μm wavelength, such traps are capable of confining and freely manipulating single living cells without optical damage. The trap was introduced into the viewing plane of a standard high resolution optical microscope with a high numerical aperture objective for combined trapping and viewing of cells and particles. The reproduction of E. coli bacteria and yeast cells was observed within the infra‐red trap, thus demonstrating damage free operation at power levels capable of moving cells at velocities of 100's of μm/ s in water. Manipulation of organelles within the interior of living plant and animal cells was also demonstrated. Separation of single cells from a collection of cells was accomplished. In addition to E. coli and yeast cells, the technique has been applied to red blood cells, protozoa, tobacco mosaic viruses, many varieties of motile bacteria, and plant cells. The ability to trap cells and organelles within cells having a wide variety of shapes and sizes under damage free conditions enhances the prospects for use of optical trapping techniques in the biological sciences.
Photodynamic therapy
Authors: Steiner R. , Rück A. , Schneckenburger H. 
Published: July 2012

AbstractIn the wide field of laser applications in medicine, the photodynamic therapy is a very fascinating method for cancer diagnosis and therapy. The essential part of this treatment is the photosensitizer used, its selectivity, toxicity and phototoxicity. The first photosensitizer has been haematoporphyrinderivative (HPD); meanwhile a lot of potential dyes have been tested and the run for the “ideal” sensitizer is still going on. Also the reaction mechanisms are probably different, and depend on the dye. The last step in the reaction is the creation of the reactive oxygen molecule, which destroys the tumor cell. The selectivity of this reaction, the higher concentration of the dye in the tumor (cells and the vascular system) compared to the normal tissue, considerably depends on the type of the tumor. Beside this, the parameters of laser irradiation for a successful treatment are very critical. Laser‐tissue interactions limit the applications up to now to special tumor types and tumor stages. Nevertheless, photodynamic therapy will become increasingly important in the future, also in combination with conventional techniques.
Polarization CARS spectroscopy, chiral molecules and magnetic field effects
Authors: Schneider F. W. , Brakel R. , Spiegel H. 
Published: July 2012

AbstractDue to the interference with the non‐resonant background conventional CARS has not yet become a routine method to obtain Raman spectra of fluoresceing biological molecules. The use of polarization CARS which completely eliminates the non‐resonant background signal is demonstrated for an absorbing substance, cytochrome c. CARS bands with a depolarization ratio equal to that of the non‐resonant background ( = 1/3) may not be observed in polarization CARS. We also investigate chiral molecules (( + )‐ and ( −)‐(1)‐phenylethylamine) by an optical homodyne method and phase sensitive detection (quarter wave plate) in order to measure Raman optical activity (ROA) in CARS. ROA arises from magnetic dipole and electric quadrupole interactions. We applied a magnetic field in order to induce ROA (MROA) in nonchiral molecules (β‐carotene and others). MROA may be a sensitive probe for properties of degenerate molecular states. Phase sensitive detection (CARS ellipsometry) has not yet produced any measurable effect of natural ROA or MROA in CARS within our detection limit of 2 · 10−4 rad at 1.6 Tesla for several molecules. Here we give quantitative conditions that have to be surpassed for the detection of ROA and MROA by CARS.
Tissue diagnostics using laser‐induced fluorescence
Authors: Andersson‐Engels S. , Ankerst J. , Brun A. , Elner Ar. , Gustafson A. , Johansson J. , Karlsson S.‐E. , Killander D. , Kjellén E. , Lindstedt E. , Montán S. , Salford L. G. , Simonsson B. , Stenram U. , Strömblad L.‐G. , Svanberg K. , Svanberg S. 
Published: July 2012

AbstractWe have performed extensive investigations of laser‐induced fluorescence in animal and human tissue aimed at instant tissue characterization. Autofluorescence, as well as specific fluorescence from HPD/DHE and other photosensitizers, has been utilized. The studies have been focused on the demarcation of malignant tumours and atheroscleortic plaques. A nitrogen laser or an excimer‐pumped dye laser was used to induce fluorescence, which was analysed with an intensified optical multichannel system. A fibre‐optic sensor system was developed for the clinical work. Multi‐colour fluorescence imaging has also been demonstrated along a line and equipment for two‐dimensional imaging is being constructed. Dimensionless spectroscopic functions, which are not affected by factors that are clinically uncontrollable have been employed for optimum tissue discrimination. The investigations have so far been performed in a time‐integrated mode, but time‐resolved studies are now being initiated to fully exploit the diagnostic power of tissue laser‐induced fluorescence. In addition to a presentation of our own work a brief review of tissue fluorescence studies performed by other groups is also given.
Laser mass analysis in biology
Authors: Spengler B. , Karas M. , Bahr U. , Hillenkamp F. 
Published: July 2012

AbstractSince the development of laser microprobe mass analysis, a large number of investigations have shown the versatility of the technique for biological and medical applications. The main advantages are high sensitivity and a spatial resolution in the μm‐range. Several approaches were used to test the possibility for a quantitative analysis, using internal standards. So far absolute quantification is in general not possible. Nearly all laser microanalysis investigations concerned the spatial distributions of elements (mainly metal ions) in a biological matrix. In a few cases the local organic composition was mapped by “fingerprinting”. Only in a small number of investigations could molecular constituents in the sampled microarea be observed and identified directly out of their native surroundings. Laser desorption/ionization (LDI) as an ionization method for mass spectrometric analysis of bioorganic substances on the other hand has proven to be a useful technique of its own. For ultraviolet‐LDI pioneering work has been done towards understanding of the processes of energy deposition and ion formation. As a result of this a matrix technique was developed, which now is able to generate intact molecular ions of proteins up to the 100000 dalton mass range and above.
Laser fluorescence microscopy of nuclear protein targeting by synthetic signal peptides
Authors: Fan H. , Peters R. , Lanford R. E. 
Published: July 2012

AbstractImmunoglobulin G was conjugated with synthetic peptides containing the nuclear localization sequence of the simian virus 40 T‐antigen. The peptide‐protein conjugates were injected into the cytoplasm of hepatoma cells. Nucleocytoplasmic transport of the conjugates was studied by both immunofluorescence staining of fixed cells and laser microfluorimetry of living cells. The results obtained by the two methods were compared and discussed with regard to previous studies of nucleocytoplasmic protein transport.