bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarized Absorption Spectra of Tetracyanoplatinate(II) Single Crystals
Authors: Tuszynski W. , Gliemann G.
Published: July 2012

Polarized single crystal absorption spectra of Mx[Pt(CN)4]·nH2O with M = Na, Sr, Ca, Ba, Mg at T = 10 K and 300 K are reported. From structural details of the spectra the energetic order of the low lying excited electronic states can be established.
Transfer of Multicomplexed Ions Across the Interface Between two Immiscible Electrolyte Solutions I; Fe(II, III), Ni(II) and Zn(II) Ions Complexed by Bidentate Nitrogen Bases
Authors: Homolka Daniel , Wendt Hartmut
Published: July 2012

Transfer from water to nitrobenzene of Iron(II) and (III), Ni(II) and Zn(II) complexed in the aqueous phase by one, two and three molecules of o‐phenanthroline and o,o'‐bipyridine was investigated using cyclic voltammetry. The kinetically inert complexes of Fe(II), Fe(III) and Ni(II) are keeping their ligand‐metal bonds intact and are transferred reversibly from water into nitrobenzene. The uncomplexed metal ions are not transferred within the voltage range limited by transfer of the ions of the aqueous and nonaqueous supporting electrolyte. Ease of phase‐transfer is greatly enhanced by complexation with the organic ligand and successive addition of the first, second and third bidentate nitrogen base changes the Gibb's transfer enthalpy of the Ni(II) by approximately equal amounts (ΔΔG° ≈ − 37 kJ/Mol;). The molecular structure of the complex ligand bears only a minor but clearly discernible influence on the Gibb's transfer enthalpies as demonstrated for Ni(II)‐phenanthroline and bipyridine complexes. Comparative investigation of phase transfer of Fe(II)‐and Fe(III)‐trisphenanthroline complexes reveals that due to higher charge of the Fe(III)‐complexes they are more strongly solvated in aqueous solution and hence less easily extracted into nitrobenzene than Fe(II)‐ complexes. Voltammograms for transfer of complexed zinc ions which form kinetically (fast) labile complexes in water as well as in nitrobenzene are to a great deal determined by fast homogeneous kinetics. ‐ In particular mono‐ and bicomplexed zinc ions (ZnL2+ and ZnL2+2) undergo rapid disproportionation with preferential formation of triscomplexed zinc (ZnL2+3) in the nonaqueous phase. Diffusion coefficients of differently complexed species in water are determined and show a shift to lower values with increasing degree of complexation.
Defect Structure and Transport Properties of Manganese Oxides: (II) The Nonstoichiometry of Hausmannite (Mn3δO4)
Authors: Keller M. , Dieckmann R.
Published: July 2012

The deviation from stoichiometry δ in hausmannite (Mn3δO4) has been thermogravimetrically studied as a function of oxygen activity between 1000 and 1130°C for the low temperature phase (α‐Mn3δO4) and between 1200 and 1350°C for the high temperature phase (ß‐Mn3δO4). A cation deficit is observed at high oxygen activities and a cation excess at low oxygen activities. In the temperature range investigated, it is concluded that the dominant defect species in both phases are cation vacancies at high oxygen activities and manganese interstitials at low oxygen activities. In addition, based on the present nonstoichiometry data, the phase diagram of the maganese‐oxygen
Thermodynamik fester Fe ‐Ni Legierungen: Massenspektrometrische Bestimmung der thermodynamischen Mischungseffekte und Berechnung des Schmelzdiagramms
Authors: Tomiska J. , Neckel A.
Published: July 2012

Thermodynamic investigations on solid Fe‐Ni alloys (f.c.c.‐phase) have been performed by means of a mass spectrometer in combination with a high temperature Knudsen cell unit. The “Algebraic Intensity‐Ratio”‐method (A.I.R.) has been applied for determing the thermodynamic excess functions. The molar excess Gibbs energies GE, the molar heats of mixing HE, and the molar excess entropies SE are negative over the whole range of composition. At 1623 K the minimum value of GE is ‐2350 J/mol (57.6 at % Ni), the minimum value of HE is ‐3950 J/mol (63.6 at % Ni), and the minimum value of SE is ‐1.04 J/mol K (70.2 at % Ni). The thermodynamic activities aj show slight negative deviations from Raoult's law. Using the results of this work, the thermodynamic results from mass spectrometric studies on liquid Fe ‐Ni alloys, and literature data for the enthalpies and heat capacities of Fe and Ni the phase diagram has been redetermined, using a generally applicable procedure for the calculation of the equilibrium compositions of coexisting phases. The applied procedure is based upon the generalized Newton method for the numerical solution of equations.
Zweidimensionale Modellnetzwerke
Authors: Rehage H. , Veyssié M.
Published: July 2012

We have studied the tensio‐active properties of acrylate diesters at the oil‐water interface. Measurements of the interfacial tension indicate that the molecules are subsequently adsorbed at the interface. The amphiphatic compounds in the monolayer can be polymerized and cross‐linked by UV irradiation. The gelation process of the two‐dimensional system has been studied by measuring the shear mechanical properties. We observed a clear transition from a viscous solution to a cross‐linked gel state. The two‐dimensional films behave like rubber elastic systems. The elasticity depends strongly on the concentration of the cross‐linking agent. The polymerisation of mixed films of monoacrylates and diacrylates can be used to built up two‐dimensional structures with defined rheological properties.
Ordnugszustände in binären Systemen aus Poly(vinylidenfluorid) und Poly(vinylfluorid)
Authors: Vonneguth K. , Trafara G. , Hummel D. O.
Published: July 2012

Binary systems of poly(vinylidene fluoride) (PVDF) and poly(vinyl fluoride) (PVF) have been studied by differential scanning calorimetry and X‐ray diffraction. The polymers were prepared by 60Co‐γ‐inducted bulk polymerization at 273 K. The increase of the glass transition temperature of PVDF in binary systems with low concentrations of PVF can be explained by a partial miscibility of the components in the non‐crystalline state. In the same way the higher thermal stability of PVF in the binary systems up to temperatures of 30 K above the melting point of PVF can be explained. PVDF and PVF crystallize separately. There is no indication of the formation of mixed crystals of the two polymers. On the other hand, the crystallization of PVDF is influenced by the presence of PVF.
Liquid‐Liquid Phase Separation in Multicomponent Polymer Systems. XXIV. Thermodynamics of Polymer Blends
Authors: Koningsveld R. , Kleintjens L. A. , Leblans‐Vinck A. M.
Published: July 2012

Within its own scope the classic Flory‐Huggins‐Staverman theory for macromolecular systems can easily be extended so as to deal with lower consolute miscibility behaviour as such, as well as in combination with upper consolute miscibility in the same system. A further improvement is achieved if the different numbers of nearest‐neighbour contacts the various repeat units and molecules can make are accounted for. Strong bimodality of lower consolute cloudpoint curves seems to call for the introduction of free‐volume terms. Some consequences of such bulk mixture terms are discussed briefly.
Eine Apparatur zur Bestimmung von Tieftemperatur‐Flüssigkeits‐Dampf‐Gleichgewichten und Messungen im System N2‐NO
Authors: Scheunemann U. , Wagner H. Gg.
Published: July 2012

A new apparatus for the measurement of low temperature vapour‐liquid equilibrium data is described. The vapour recirculation method is used for the mixture to reach equilibrium in a cell equipped with glass windows. Samples of both phases can be withdrawn and analysed with high precision by optical absorption in the UV‐region. Measurements were made for the system nitrogen‐nitric oxide along three isotherms between 113 and 120 K. The area test showed thermodynamic consistency of the data. The deviations of the mixtures from ideality are large, caused by dimerization of the NO in the liquid. The maximum excess Gibbs energy is about 500 J/mol.
An Orbital Fragmentation of Static Dipole Polarizabilities of Atoms of the First Three Rows. Ground State and Valence State Properties
Authors: Schmidt Peter C. , Böhm Michael C. , Weiss Alarich
Published: July 2012

Within an ensemble averaged variant of the local density approximation (LDA) a computational framework is developed that allows for a straightforward orbital resolution of atomic static dipole polarizabilities α˜D. The accuracy of the method as well as its computational expenditure are roughly comparable with numerical coupled Hartree‐Fock (CHF) variants. The calculated values for the ground state configurations of the atomic species of the first three rows (LiF, NaCl, KBr) are in good agreement with the results of recently published highly sophisticated theoretical calculations based on LCAO‐type expansions (e.g. PNO‐CEPA) and are also close to precise experimental data (Li, Na, K, Ca). The employed ensemble formalism within LDA allows for the introduction of one‐electron contributions to the total atomic polarizabilities that span the full width from pure atomic orbitals as one‐electron basis to any desired hybrid state. It is shown that the orbital increments to α˜D an be expressed into the form of simple linear relations as a function of the hybridization of the one‐electron wave function. Mean static dipole polarizability increments α˜D the corresponding m = 0 components into the direction of the electric field α˜D(m = 0) as well as m = ± 1 components in the plane perpendicular to the external point charge α0,D(m = ± 1) are tabulated. The relevant numbers depend on the type of the atom and (weakly) on the electronic configuration. Ground state configurations and valence states have been analyzed. The α0,D elements increase linearly with increasing p admixtures in the corresponding hybrid function. The gradient expressing this dependence is largest for the diffuse atoms on the left side of the periodic system. The employed resolution of the α0,D values and the averaging procedure leading to “ensemble states” are a prerequisite for the adaption of the present one‐electron increments in molecular or solid‐state calculations of static dipole polarizabilities on the basis of an atoms‐in‐molecule approach.
On the Order‐Disorder Phase Transition of Anilinium Halides. 127I‐NQR Investigation of the Anilinium Iodides C6H5NHI⊖, C6H5NDI⊖, C6D5NHI⊖, and C6D5NDI⊖. Dilatometric Studies on Anilinium Bromide and Anilinium Iodide Single Crystals
Authors: Feeder Gerhard , Weiss Alarich
Published: July 2012

127I‐NQR measurements in the range 77 ≤ T/K ≤ 520 are reported for anilinium iodides C6H5NH⊕3I⊖, C6H5ND⊕3I⊖, C6D5NH⊕3I⊖, and C6D5ND⊕3I⊖. The compound undergoes a ferroelastic phase transition at 240.3 K (C6H5NH⊕3I⊖). The transition temperature changes to 233.6 K (C6H5ND⊕3I⊖) and to 233.4 K (C6D5ND⊕3I⊖) by deuteration. The NQR parameters are thereby influenced too. At 293 K the −NH⊕3 group deuteration influences e2ϕzzQh−1 and η much stronger than the ring deuteration, whereas at 77 K these effects are of comparable magnitude.—The thermal expansion coefficients were measured for C6H5NH⊕3X⊕, X = Br, I, from 120 K to 300 K. by dilatometry and by X‐ray diffraction. In C6H5NH⊕3Br⊖ the three linear expansion coefficients are increasing over the whole temperature range studied, whereas in C6H5NH⊕3I⊖ α[010] increases and both, α[100] and α[001], decrease with increasing temperature. On hand of the known crystal structures the ferroelastic phase transition in the anilinium halides is discussed. The basic mechanism of the transition is the same for C6H5NH⊕3I⊖ and C6H5NH⊕3Br⊖. Freezing in of the −NH⊕3 group hindered rotation is the main process governing the phase transitions, but motions of the phenyl ring are of influence, too.
Topological Aspects of the (1 × 1) ⇌ “Hexagonal” Phase Transition on Pt(100)
Authors: Hösier W. , Ritter E. , Behm R. J.
Published: July 2012

We have investigated the (1 × 1) ⇌ “hexagonal” phase transition on Pt(100) by Scanning Tunneling Microscopy with special emphasis on the density change of the topmost Pt layer correlated to this process. It was found that in both directions extra atoms are accommodated in monolayered islands on top of the flat substrate. The size of the islands mainly depends on the transition temperature, from 25 Å at 375 K to 100 Å at 550 K, which is explained by a stability increase of these islands with increasing size, in agreement with thermodynamic arguments over interface tension.
Structures and Phase Transitions in Physisorption: Molecular‐Axis Orientational Ordering in Nitrogen and Carbon Monoxide Monolayers on Graphite
Authors: Fain Samuel C.
Published: July 2012

Molecular axis‐orientational ordering occurs at temperatures below 40 K for monolayers of molecular nitrogen and carbon monoxide physisorbed on the graphite basal plane. The method by which the type of structure has been inferred from the symmetries observed in low‐energy electron diffraction (LEED) measurements is briefly reviewed. The information available about the molecular‐axis orientational order‐disorder transitions from LEED, neutron diffraction, X‐ray diffraction, and heat capacity measurements is reviewed and qualitatively compared with theoretical expectations.
Wetting Phenomena at Domain Boundaries
Authors: Selke Walter
Published: July 2012

Interfaces between the three physically distinct, but equivalent domains in the (3 × 1) phase of lattice gas models for the adsorbate systems O/Pd(110) and H/Fe(110) are studied. At the wetting transition, the interface or wall between two domains decomposes into two walls of a different type separated by a macroscopically thick region of the third domain. Using mainly Monte Carlo techniques, the characteristic walls are identified and wetting transition lines are determined for phase diagrams in the coverage‐temperature plane.
Phase Transitions in Adsorption Layers on bcc(110) Surfaces: S and O on Mo(110)
Authors: Witt W. , Bauer E.
Published: July 2012

The adsorption of sulfur on Mo(110) was studied by a combination of low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and work function change (ΔΦ) measurements using very fine coverage increments. The evolution of the structures with coverage θ was found to be quite different from that formerly reported for S/Mo(110): discrete commensurate structures exist only for θ ≤ 1/2, whereas for θ > 1/2 a continuous series of incommensurate structures is interrupted by narrow regions of commensurate structures similar to those reported for S/W(110). Thus the “high symmetry hypothesis” is no longer applicable for the interpretation of the structures of S/Mo(110). High resolution LEED diffractometry was used for detailed studies of the S and O/Mo(110)‐p(2 × 2)→(1 × 1) transition. For O this is a single continuous order‐disorder transition contrary to S for which the transition occurs in two steps: a continuous order‐order transition from the p(2 × 2) to a two domain (4 × 1) structure which is followed by an order‐disorder transition. For both adsorbates critical exponents β(θ) and phase diagrams were derived from the data. Finally the kinetics of the domain growth were investigated for S/Mo(110)—p(2 × 2). The time dependence of the average domain size L holds the predicted power law L(t) ∼ tx; x depends on θ. For the ideal p(2 × 2)‐structure x(θ = 1/4) = 0.36 ± 0.03, which is close to the predicted value for Kawasaki dynamics x = 1/3.
Zeolite Supported Iron Oxide as Catalyst or Catalyst Precursor for Hydrocarbon Conversion Reactions
Authors: Bein Thomas , Helen Mia , Jacobs Peter A.
Published: July 2012

When NaY saturated at room temperature with iron pentacarbonyl, is oxidized at room temperature in a very diluted oxygen flow, a zeolite encaged Fe2O3‐phase is obtained as shown by Mössbauer spectroscopy, electron microscopy and X‐ray diffraction. This catalyst contains 10% by weight of iron and serves as a good precursor of a Fischer‐Tropsch (F.T.) catalyst. Unfortunately, the Fe2O3 phase is unstable under F.T. conditions, since it is shown that the iron phase migrates out of the zeolite matrix during reaction.—This encaged iron oxide phase can be hydrogen reduced giving finely dispersed and zeolite encaged iron, as is shown by physical and chemical methods. This system is a stable and active hydrogenolysis catalyst. Its selectivity is influenced by both particle size and support effects.
Interactions of Hydrophobia Layer Silicates with Alcohol‐Benzene Mixtures I. Adsorption Isotherms
Authors: Dékány I. , Szántó F. , Weiss Armin , Lagaly G.
Published: July 2012

A model isotherm is developed that describes the adsorption of methanol and benzene from methanol‐benzene mixtures throughout the whole concentration range (molar fraction of methanol from x1 = 0 to x1 = 1). The clay mineral montmorillonite is used as an adsorbent. The silicate layers are made hydrophobia by exchanging the inorganic gegen ions by alkylammonium ions CncH2nc + 1 NH3+ (nc = 10—18). With increasing alkyl chain length (increasing hydrophobicity) the amounts of benzene adsorbed (ns2) increase, whereas those of methanol (ns1) remain constant. The adsorption potential η1 of methanol decreases and that of benzene (ζ2) increases with the alkyl chain length. The difference η2—η1 changes from positive to negative at nc = 16. Besides the influence of the alkyl chain length, the shape of the excess isotherms and the azeotropic compositions are mainly determined by the bulk‐phase activities.
The Observed and Calculated Vibrational Spectra of DL‐methionine in the Study of the Solid State Phase Transition
Authors: Grunenberg Alfons , Bougeard Daniel
Published: July 2012

The ir and Raman spectra of α and β‐DL‐methionine and three isotopomers have been recorded and assigned with the help of normal coordinate analyses. The vibrational intensities of three conformers (χ1 = gauche II; χ2 = trans; χ3 = gauche I, trans, and gauche II) have been calculated for the free molecule with a MNDO program including a finite field perturbation. Except for the vibrations including the S atom, the CO−2 and NH+3 group the calculations agree with experimental data and confirm the change of χ3 from trans to gauche I at the 326 K transition. The lattice vibrations confirm the conservation of the overall structure of the double layers through the transition.
Defects and Cation Diffusion in Magnetite (VI): Point Defect Relaxation and Correlation in Cation Tracer Diffusion
Authors: Dieckmann R. , Schmalzried H.
Published: July 2012

Chemical diffusion coefficients have been derived from experiments on the point defect relaxation in magnetite. Based on data from preceding studies on the nonstoichiometry of magnetite and on the iron tracer diffusion of this oxide, the chemical diffusion coefficients are analyzed with regard to elementary diffusion processes and the correlated motion of tracer cations.
Cationic Motions Involving Self‐Diffusion and Structural Phase Transitions in Solid Dimethyl‐ and Trimethylammonium Nitrates as Studied by Differential Thermal Analysis and 1H NMR Techniques
Authors: Ishida Hiroyuki , Ikeda Ryuichi , Nakamura Daiyu
Published: July 2012

Differential thermal analysis and the temperature dependence of broad‐line 1H NMR absorptions and of 1H spin‐lattice relaxation times in both laboratory and rotating frames were observed for (CH3)2NH2NO3, (CH3)ND2NO3, and (CH3)3NHNO3. A solid‐solid phase transition was located at 297 K for (CH3)2NH2NO3. while two phase transitions at 359 and 407 K were found for (CH3)3NHNO3. The 1H spin‐lattice relaxation times in the laboratory frame at different Larmor frequencies and those in the rotating frame at the rf field of 8 G observed for the above salts were analyzed by referring to the 1H NMR second moments determined. The motional parameters of the cations in each solid phase of the salts were evaluated by a fitting calculation to the relaxation times observed. In the highest‐temperature solid phase of (CH3)3NHNO3, the cation was found to perform self‐diffusion as well as overall rotation with the relatively low activation energy of 29 kJ mol−1. The motions of the cations in each newly found solid phase are characterized.
In Situ Studies of Intercalation Reactions Via Nuclear Quadrupole Interactions
Authors: Butz T. , Lerf A.
Published: July 2012

We report on the in situ measurement of the nuclear quadrupole interaction of radioactive 181Ta labels in 2H‐TaS2 during (i) electrochemical intercalation of lithium, hydrated potassium, hydrogen and (ii) thermal intercalation of indium (at 670 K), gallium (850 K), and the eutectic In0.17Ga0.83 (300 K!). The measurements were performed by time differential perturbed angular correlation (TDPAC) on the 133–482 keV γ‐γ‐cascade in 181Ta. Information on the reaction pathways, on non‐equilibrium phenomena and their equilibration, on intercalate mobilities, and on the thermal stability of the compounds is presented.
Zur Stabilität olivinischer Silikate im Sauerstoffpotentialgradienten. II. Das Kobaltsilikat Co2SiO4
Authors: Brinkmann U. , Laqua W.
Published: July 2012

The decomposition of Co2SiO4 in oxygen potential gradients is studied at T = 1.600 K. The critical ratio of the two oxygen partial pressures, at which the compound can be found decomposed into CoO and SiO2, depends strongly on the location of the acting oxygen potential field within the single phase region of Co2SiO4. The results can be explained by po2‐dependent Co‐ and Si‐diffusivities via vacancies and interstitials respectively.
Chemical Diffusion in CuInS2 in the Temperature Range of 20°C to 100°C
Authors: Kleinfeld M. , Wiemhöfer H.‐D.
Published: July 2012

Measurements of steady state current voltage relation and transient resistance with point electrodes on CuInS2 showed effects of ionic mobility at low temperature due to mobile copper ions. From the form of the steady state current voltage relation it was concluded that increasing copper concentration leads to a change from p‐ to n‐type conduction in CuInS2 at the contact with the point electrode. From transient measurements, chemical diffusion coefficients of copper were derived which increase with decreasing electrical conductivity of CuInS2. At 20°C, 1.1 · 10−7 cm2/s was measured on a sample with a conductivity of 0.64 (Ω cm)−1, another sample with 21 (Ω cm)−1 gave 2.1 · 10−1 cm2/s.
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

The 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

Salt 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

Starting 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

For 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

Ab 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

The 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

Photocatalytic 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

Doped 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

The 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

The 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

The 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

The 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

The 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

UV/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

It 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

The 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

It 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

In 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

Due 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

We 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

Since 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

Immunoglobulin 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.
IR Spectroscopic Investigations During Oscillations of the CO/NO and the CO/O2 Reaction on Pt and Pd Catalysts II: Palladium
Authors: Schüth F. , Wicke E.
Published: July 2012

Based on previous work [1–3] oscillations of the CO/O2 reaction on Pd catalysts were reinvestigated with an improved equipment [4]. This allowed analysis of the PdLCO band which was found to oscillate in phase with the absorbance in the BCO band region. A model developed earlier could essentially be confirmed: The oscillations are driven by a CO induced transformation of the 2 × 2 oxygen adstructure to a (√3 × √3)R30° structure. Oscillations were also observed on evaporated Pd films and analyzed by means of IR spectroscopy. The behaviour of these specimen resembles strongly that of supported materials. —Oscillations of the CO/NO reaction on Pd were observed for the first time; they occurred at NO/CO ratios between 0.5 and 2 at temperatures around 600 K. The most prominent feature of this reaction is the low coverage of the Pd surface with molecular species under oscillatory conditions. By means of IR spectroscopy oscillations of NCO bands, counterphase to the reaction rate oscillations were observed, as well as small amplitude oscillations of the COad bands in phase with the reaction rate. These findings, together with results of kinetic investigations, led to a thermokinetic model involving blocking of the Pd surface with Nad and reactivation by desorption of N2. A simplified theoretical analysis revealed the generation of oscillations in such a model. —By measurements on catalyst disks (wafers) spatial inhomogeneities of the reaction rate over the disk surface were detected which might be responsible for the occurrence of chaotic behaviour.
Photochemical production of peroxy radicals and their interaction with aromatic alcohols
Authors: Paál‐Lukács Julia , Gál Dezsö , Butovskaya Galina , Agabekov V. E.
Published: July 2012

The reaction between 1‐phenylethyl peroxy radicals and 1‐phenyl ethanol, benzyl alcohol and cumyl alcohol has been studied at T = 55°C. The rate coefficients of the hydrogen abstraction reactions for the three alcohols are 18.7 ± 2.7, 17.8 ± 1.9 and 4.8 ± 0.5 M−1 8−1, respectively. In the case of 1‐phenyl ethanol experiments were carried out at T = 25 and 40°C as well, resulting in rate coefficients of 7.3 ± 0.7 and 10.5 ± 0.9 M−1 s−1, while the energy of activation — taking into consideration also the data of Hajdu et al. — was 27.7 ± 0.5 kJ mol−1.
Chemical exchange and raman line broadening III. A comment to [1]
Authors: Strehlow H.
Published: July 2012

The question of whether the integrated intensities of vibrational spectra are changed due to fast chemical reactions [2] or whether they are not [1] is discussed theoretically and experimentally.