bluuebunny/crossref_metadata_2025_split huggingface dataset:
p, T-Dependence of Self Diffusion in Mixtures of Hexane/Ethanol and Hexane/Dimethylether
Authors: Heinrich-Schramm A. , Price W. E. , Lüdemann H.-D. 
Published: February 2015

Abstract
Self-diffusion in ethanol/hexane and dimethylether/hexane mixtures of various compositions has been measured at 215-350 K and up to 200 MPa. Qualitative analysis of the results indicates that, as expected, hydrogen bonding retards the self-diffusion of ethanol in the mixture, especially at the low temperatures. Dimethylether shows a slight effect of dipole-dipole interactions on the self-diffu­sion, as seen by a higher ΔE* value than for the alkane. However there is no significant difference in the pressure dependence for both mixtures. This is shown by considering the ratio of the two diffusion coefficients, which suggests that, contrary to what is observed for pure alcohols, pressure has little effect upon the hydrogen bonding of ethanol in the mixture. In additon, there is surprisingly little concentration dependence on the ratios for either mixture.
Stability of (Ni1_xLix)(Li1–yNiy)02Ordered Solid Solution
Authors: Massarotti V. , Capsoni D. , Bini M. 
Published: February 2015

Abstract
The stability of ordered solid solutions (OSS) with LiNiO2 structure has been studied in a wide range of the lithium cationic fraction (0.22< xt < 0.42). The OSS is obtained from the reactive system Ni0/Li2CO3 at 800 °C starting with high nominal lithium content (xt = 0.5). By analysis of the decrease of x, observed after annealing, during which evaporation and a contact reaction occurs, structure-composition relationships can be obtained.
The transformation of the ordered phase, due to a cation exchange process, is observed for xt < 0.31 by accurate X-Ray powder pattern analysis (Rietveld method). By increasing the annealing time (decreasing lithium content), the data can be explained on the basis of progressive formation of the simple solid solution (SSS) with only one cation site and halved c axis value. The variations of structural parameters during the transformation are compared with those reported in the literature. The coherence domains of the OSS become smaller and the phase percentage decreases, while the SSS percentage increases. The rate of such a process can be well described on the basis of a two dimensional diffusion mechanism.
2 D 31P Exchange NMR: A new Approach for a Direct Probing of the Connectivities of Qn Units in Glasses
Authors: Born R. , Feike M. , Jäger C. , Spiess H. W. 
Published: February 2015

Abstract
Recently, 31P two-dimensional (2D) NMR has been proposed as a powerful tool for direct investigations of the connectivities between the Qn units in glasses, i.e. the medium-range order. In this paper, the principles of these experiments and applications to both polycrystalline Mg2P2O7 and a Na2O-P205 glass are demonstrated, including a theoretical description and modelling of the polarization transfer between the two inequivalent phosphorus sites in the magnesium pyrophosphate.
A New Weak Field Double Resonance NMR Spectrometer
Authors: Akay Cengiz , Yalçiner Aytaç 
Published: February 2015

Abstract
Weak field NMR and double resonance spectrometers are mostly homemade. In this work, some electronic units of such a spectrometer operating at 1.437 mT were designed and realized by includ­ing new integrated circuits: an audio generator, digital sweep generator, digital additional field and delay unit, Quartz generator, NMR detector(Q-meter), AF-narrowband amplifier, phase shifter and phase sensitive detector.
On the Use of Pulsed Field Gradients in a High-Field NMR Spectrometer to Study Restricted Diffusion in Zeolites
Authors: Kärger J. , Bär N.-K. , Heink W. , Pfeifer H. , Seiffert G. 
Published: February 2015

Abstract
A probe system is described which allows the application of magnetic field gradient pulses with amplitudes up to 24 T/m for self-diffusion measurements by means of a PFG NMR spectrometer operating at a proton resonance frequency of 400 MHz. It is demonstrated that PFG NMR measurements in the high field of a superconducting magnet necessitate precautions which are of minor relevance for measurements with iron magnets. Taking advantage of the large gradient intensity and the high sensitivity in signal detection of the described system, attenuation patterns of the NMR spin echo are observed for the first time that represent the PFG NMR analogue of the diffraction pattern of a sphere.
Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals
Authors: Grabke H. J. , Siegers M. , Tolpygo V. K. 
Published: February 2015

Abstract
Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides.
Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher.
All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.
The Structural and Dynamic Properties of some Transition Metal Aqua Cations: Results from Neutron Scattering
Authors: Neilson G. W. , Ansell S. , Wilson J. 
Published: February 2015

Abstract
The following paper comprises a survey of the role neutron scattering methods have played to help understand the origins of the diverse properties of electrolyte solutions which contain transition metal cations. It is seen how neutron diffraction and isotopic substitution is able to resolve the local structure around contrasting ions, such as Cr3+ , Ni2+, Fe3+ , Fe2+, Cu2+, without recourse to sophisticated modelling procedures. Quasielastic neutron scattering (QNS) provides insight into the dynamics of the protons in solution. The results enable one to distinguish between cations whose water molecules are coordinated on time scales larger than 5 x 10-9 s, shorter than 10-10s, or intermediate between those two limits. QNS also provides information on the existence of a second relatively short-lived hydration shell distinct from the bulk water.
A Raman Study of Alcoholic Lithium Perchlorate Solutions in the Glassy State
Authors: Kanno H. , Honshoh M. , Yamauchi S. 
Published: February 2015

Abstract
Raman spectra of alcoholic lithium Perchlorate solutions (alcohol = methanol and ethanol) were measured as a function of LiClO4 concentration. The Raman band due to nearly free hydrogen bonds shows peculiar concentration dependences: (1) its frequency shifts with LiClO4 concentration in contrast to alcoholic LiX solutions (X = CI and Br), in which the Raman band due to solvated halide ions shows little frequency change with LiX concentration, and (2) the half band width shows anomalous changes with LiX concentration.
Non-ionized LiClO4 species in alcohol coupled with the changes of solution structure are the major cause for this peculiar behavior.
The Structure of Hydroxylamine – Water Mixtures
Authors: Vizoso Sergi , Rode Bernd M. 
Published: February 2015

Abstract
Monte Carlo simulations have been carried our for 5, 25, 50, and 75 weight% aqueous solutions of hydroxylamine. Changes in the microstructure of the solutions have been evaluated by means of radial and angular distribution functions, coordination number distributions and pair energy anal­ysis. The structure of liquid hydroxylamine is strongly altered by even small amounts of water, whereas water clusters similar to the pure water are maintained up to higher NH2OH concentra­tions. The structural entities in the mixtures are determined by hydrogen bonding and electrostatic arrangement of ligands.
Raman Spectral Studies of Aqueous Acidic Pyrazine Solutions
Authors: Brolo Alexandre G. , Irish Donald E. 
Published: February 2015

Abstract
Raman spectra of aqueous pyrazine have been investigated in acidic media: HCl from pH = 4 up to 11 M; HCLO4 from 0.1 M to 12 M; H2SO4 form 0.1 M to 18 M. From observation of the shifts of the bands from neutral solutions, it has been possible to identify bands uniquely characteristic of unprotonated pyrazine and its two protonated forms. The diprotonated form was only observed for high concentrations of HCLO4 and H2SO4. From bandfitting of the spectral contours it has been possible to construct the species distribution diagram and estimate the pK values. Raman bands of the three species have been identified and assigned. The results are used to explain an unassigned band at 1235 cm-1, reported by several authors, in SERS from pyrazine on silver and gold electrodes.
Raman Spectroscopic Study of the Ion Association of Lithium Sulfate Aqueous Solutions
Authors: Rull Fernando 
Published: February 2015

Abstract
A Raman spectroscopic study of Li2SO4 aqueous solutions as function of concentration and temperature was performed. The dynamic properties of the sulfate ions were studied by a band profile analysis of their internal modes using Fourier transform methods. This analysis reveals the perturbation of the SO4
-2 vibrations due to ionic interactions. From the v1 (SO4
-2) band profile the spectroscopic ionic association constant was calculated in the range from 5 to 80 °C. The large difference found between the values thus obtained for the association constant and the values obtained from macroscopic measurements is interpreted, assuming that Raman spectra reflect only the short-range forces acting on the ions. Using the Bjerrum equation to calculate the contribution for the long-range forces, good agreement is found between the spectroscopic and macroscopic results.
Effects of Pressure, Temperature, and Concentration on the Viscosity of Aqueous Ammonium Bromide Solution
Authors: Yoshimura Yukihiro , Sawamura Seiji , Taniguchi Yoshihiro 
Published: February 2015

Abstract
The viscosity of aqueous ammonium bromide solutions is measured at 0.1-1.0 mol kg-1, 278.2-323.2 K, and 0.1-375 MPa, using a high-pressure rolling-ball viscometer. The activation energy (Ev) for viscous flow and Jones-Dole's B coefficient are estimated. Ev against pressure yields a concave curve with a minimum and B yields a convex one with a maximum. These phenomena are attributed to pressure, temperature, and concentration effects on the water-structure.
Bose -Einstein Condensation and Condensate Tunneling
Authors: Grossmann Siegfried , Holthaus Martin 
Published: February 2015

Abstract
We consider Bose-Einstein condensation in a small cube and describe effects induced by the con­ finement. We also sketch an analogue of the Josephson effect for neutral particles, which can be realized when two almost degenerate states in a double well potential are occupied by a macroscopic number of Bosons. PACS number: 05.30.Jp
Computer Simulation of a Simple Model for Rotational Moment Fluctuations in an Associating Liquid
Authors: Köhne H.-G. , Stockhausen M. 
Published: February 2015

Abstract
With regard to the interpretation of dielectric relaxation spectra of associating liquids such as alcohols, a two state model for the rotational tumbling motion of a dipole is considered: The moment (of constant magnitude) is assumed to undergo stochastic tumbling during a "free" state, alternating with an "associated" state where for a certain residence time the rotational motion can be neglected. One particle autocorrelation functions according to that model are calculated numerically. In any case, they can well be described as sum of (at most) two exponentials. The corresponding parameters are given as function of "association" probability and residence time
Thermodynamic Excess Functions for Quasiternary Solid Solutions of Type M(X,Y,Z) I. The System Pb (S,Te,Se)
Authors: Leute Volkmar 
Published: February 2015

Abstract The excess free enthalpy of quasiternary systems of type M (X, Y, Z) with two sublattices, a mixed one (X, Y,Z) and a pure one (M), will be described in two ways: (1) by the interaction parameters of the three subregularly treated quasibinary subsystems and by one ternary parameter, and (2) by the cluster energies of 10 pyramidal clusters.
It is shown that, for the spinodal miscibility gap in the special system Pb (S, Te, Se), both versions yield satisfying accordance of experiments and calculated results
2H and 14N NMR Studies of the Dynamics in the Incommensurate Phases of Betaine Calciumchloride Dihydrate
Authors: Häcker U. , Michel D. , Hölzer K.-P. , Petersson J. 
Published: February 2015

Abstract

2H and 14N NMR spin-lattice relaxation rates were measured in the structurally incommensurately (IC) modulated phases of deuterated and undeuterated betaine calciumchloride dihydrate, respectively. The results are related to the elementary excitations of these phases. The presence of low-frequency phase fluctuations of the modulation wave leads to higher spin-lattice relaxation rates compared with the high-temperature normal phase and the commensurate (C) phases. The corresponding "phason" contributions are found to be nearly constant in the whole IC phases. In the IC phases near the transitions to the C phases the relaxation rates decrease due to the formation of the soliton lattice. This interpretation is in agreement with the results of previous dielectric measurements
Deuteron NMR Spectra of ND4 Tunneling at Low Frequenciesin (ND4)2SnBr6
Authors: Lalowicz Z.T. , Serafin R. , Punkkinen M. , Vuorimäki A. H. , Ylinen E. E. 
Published: February 2015

Abstract
Deuteron NMR spectra of slowly tunneling ND4
+ ions are analysed. Spectra are calculated as functions of the tunneling parameters which are the tunneling frequencies about the symmetry axes C2 and C3 of the tetrahedral ion. The structure and splittings within the ground torsional level (GTL) are obtained by fitting the spectra of (ND4)2SnBr6. Comparison with the GTL structure obtained before for NH4
+ in the same compound gives the isotope reduction factor of the tunneling frequency about 200.
XPS Investigations on Solid and Vacuum Deposited, Oxidized and Non-oxidized Palladium
Authors: Kintrup Jürgen , Züchner Harald 
Published: February 2015

Abstract
X-ray photoelectron spectroscopy (XPS) has been carried out to study the reaction of differently prepared palladium samples (solid and film Pd) with atmospheric oxygen. A careful curve fitting of the measured Pd-3d5/2 peak allows to separate the Pd-3d5/2 peak for Pd in surface PdO from the dominant Pd-3d5/2 peak of the non-oxidized bulk palladium and to determine the chemical shift of the "oxidized" Pa line with high accuracy. Differences in the chemical shifts for the surface PdO on solid and film palladium are explained by a different charging caused by the photoelectric effect in XPS measurements. The smaller charging effect observed for film palladium as compared to solid palladium indicates a stronger oxygen bonding to the (rougher) film palladium. The strong Pd-O bonding seems to be an essential reason for the reduced hydrogen-permeability of film palladium compared to solid palladium
Enhanced Sensitivity of Zero -Field NMR Spectroscopy at High Magnetic Fields
Authors: Ernst H. , Fechtelkor M. , Fenzke D. , Freude D. , Knorr B. , Kolley H. , Pfeifer H. 
Published: February 2015

Abstract
After reviewing the basic principles of zero-field NMR spectroscopy at high magnetic fields (ZFHF NMR) as introduced by Robert Tycko, a 2-dimensional extension of this method is described which enhances its sensitivity by at least one order of magnitude. The essential point is a combination of the original pulse program including sample rotation with a Carr-Purcell pulse sequence during the acquisition time. Experimental results are given for the proton resonance of meta-C6H2D4 dissolved in C6D6 at 245 K
Depolymerization Kinetics of Glass-Forming Chalcogenide Melts. Coherence TYansfer NMR Studies of Phosphorus Selenide
Authors: Maxwell Robert , Erickson Hans , Eckert Hellmut 
Published: February 2015

Abstract
The kinetics of the depolymerization of a glass-forming phosphorus selenide melt containing 48 at.% phosphorus have been studied using one- and two-dimensional coherence transfer spectroscopic methods. The depolymerization leads to the creation of molecular P4Se3. Two-dimensional spectroscopy indicates that these units are in slow exchange with the residual polymeric matrix, and corresponding rate constants are extracted from temperature dependent one-dimensional coherence transfer experiments. The results are quantitatively consistent with previous temperature-dependent NMR lineshape studies, yielding an activation energy of 109 kJ/mol
Dynamic Behaviour of Tetramethylethylene Diamine (TMEDA) Ligands in Solid Organolithium Compounds: A Variable Temperature 13C and I5N CP/MAS NMR Study
Authors: Baumann Wolfgang , Oprunenko Yuri , Günther Harald 
Published: February 2015

Abstract
The dynamic behaviour of tetramethylethylene diamine (TMEDA) ligands in three organometallic complexes, dimeric phenyllithium, [Li(tmeda)μ-Ph]2 (1), lithium cyclopentadienide, [Li(tmeda)]C5H5 (2), and dilithium naphthalendiide, trans-[Li(tmeda)]2C10H8 (3), has been studied by CP/MAS 13C and 15N as well as 7Li MAS NMR spectroscopy of powdered samples. Two dynamic processes with free activation enthalpies of 40 and 68 kJ mol-1, respectively, were detected for 1. The first one can be assigned to ring inversion of the five-membered Li-TMEDA rings, while the second is caused by a complete rotation of the TMEDA ligands or a ring inversion of the central four-membered C-Li-C-Li metallacycle. Fast rotation of the ligands on the NMR time scale was found for 2, while 3 shows 180° ring flips of the Li-TMEDA groups, which are characterized by an energy barrier ΔG" (317) of 64 kJ mol-1
Polarizabilities of Isolated Silicon Clusters
Authors: Schäfer R. , Woenckhaus J. , Becker J. A. , Hensel F. 
Published: February 2015

The static electric polarizabilities a of silicon clusters with up to 60 atoms have been measured employing a mass selective molecular beam deflection method. The polarizability per atom αN = α/N of the SiN-clusters has been investigated for Si11 and the size ranges N = 14-28, 22-34, 28-44, 34-50, 41 -58, and 42-68. The results show that the polarizability per atom decreases from N = 11 until a minimum at N≥28 is reached. The polarizability per atom increases for N > 28, passes through a maximum at N≈36 and finally converges between N≈50-70 against the value αN =1.9Å3. If the model of a homogeneous dielectric sphere is applied to the larger clusters one calculates that the value αN =1.9Å3 corresponds to a dielectric constant of ε = 3.2. This value is significantly smaller than the dielectric constant of bulk silicon εb = 11.8.
The present paper focuses on the maximum in the polarizability at N≈36. This effect is discussed with special emphasis to recent Car-Parinello calculations which have predicted cage-like silicon structures that enclose a core of several highly coordinated atoms. This structure suggests an improved dielectric sphere model where the core is represented by a smaller sphere with its own dielectric constant εc. It is shown within this model that the observed maximum in polarizability is due to a significant enhancement of the core dielectric constant to a value of εc ≈50. This enhancement is related by means of a simple model to the effect that silicon becomes metallic under high pressure
The Phase Diagram of the Quasiternary System (Sn, Pb) (S,Te)
Authors: Leute Volkmar , Brinkmann S. , Linnenbrink J. , Schmidtke H. M. 
Published: February 2015

Abstract
The phase diagram of the quasiternary system (Snt Pb1-k)(S,Te1-l) for 900 K is determined by X-ray diffraction and by electron microprobe analysis. Moreover, the free enthalpy faces g(k, I) for the phases with cubic rocksalt structure (cub) or with the orthorhombic SnS structure (orh) are calculated from the interaction parameters and from the orh → cub transition data of the 4 quasibinary subsystems.
The interaction parameters are also used to calculate the termodynamic factor for interdiffusion along quasibinary sections through the phase square and to calculate the energies of four-particle clusters. By application of the cluster model one obtains information on the local environment of the mixing particles and on the cluster processes that have effect upon interdiffusion
Helium Atom Scattering from CF4, CF3Cl, CF2Cl2 and CFCl3 in Crossed Molecular Bejams
Authors: Gebauer Christian , Klein Olaf , Schmidt Ralf , Seidel Wolfhart 
Published: February 2015

Abstract
Differential cross sections have been measured by scattering He atoms from CFnCl4-n (1≤n≤4) in crossed molecular beams. The damping of the diffraction oscillations was used to extract interaction potentials for these molecules which range from nearly isotropic to rather anisotropic. Macroscopic binary parameters, as second virial coefficients, diffusion coefficients and viscosities were calculated from these potentials
Differential Thermal Analysis and Dielectric Studies on 2-Methyl-2-Nitro-Propane under High Pressure
Authors: Büsing D. , Jenau M. , Reuter J. , Würflinger A. , Tamarit J. Li. 
Published: February 2015

Abstract
Differential thermal analysis and dielectric studies under pressures up to 300 MPa and temperatures of about 200 to 350 K have been performed on 2-methyl-2-nitro-propane (TBN). TBN displays an orientationally disordered phase (ODIC), solid I, and two non-plastic phases, solids II and III. The coexistence region of the plastic phase I increases with increasing pressure, whereas the low-temperature phase II apparently vanishes at a triple point I, II, III, above 300 MPa. The static permittivity increases on freezing, characterizing the solid I as an ODIC phase. In the frame of the Kirkwood-Onsager-Fröhlich theory the g-factor is about unity, discounting specific dielectric correlations. The dielectric behaviour of TBN is similar to previously studied related compounds, such as 2-chloro-2-methyl-propane or 2-brome- 2-methyl-propane
p, T Dependence of the Self Diffusion Coefficients and Densities in Liquid Silicone Oils
Authors: Thern A. , Lüdemann H.-D. 
Published: February 2015

Abstract
Self diffusion coefficients and densities from a series of commercial silicones have been studied in the temperature range between 290 and 410 K at pressures up to 200 MPa. The densities are fitted to a modified Tait equation. The self diffusion coefficients are discussed in terms of the rough hard sphere model and tested against the Rouse-model.