bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Properties of Liquid Metals
Authors: Güntherodt H.‐J. 
Published: September 2012

AbstractThe magnetic susceptibility of liquid metals and their alloys is reviewed and discussed in terms of current theories. For liquid simple metals the susceptibility is interpreted in terms of the free‐electron model. The magnetic properties of transition and rare earth metals can be explained by taking into account the itinerant d‐electrons and the localized f‐electrons, respectively. The present state of the magnetic properties of non‐metallic fluids having metallic constituents is reported. In such systems the magnetic susceptibility gives information on the pseudogap or helps to elucidate the ionic character.
Wechselwirkungen zwischen lokalisierten magnetischen Zuständen in flüssigen Cu  Al  Fe‐Legierungen
Authors: Pantasis Anastasios , Wachtel Ernst 
Published: September 2012

AbstractEs wird über Messungen der magnetischen Suszeptibilität an flüssigen Legierungen des Systems Cu  Al mit Fe‐Zusätzen berichtet. Während auf der Kupferseite auch bei sehr geringen Fe‐Zusätzen (weniger als 1 At.‐ %) ein Curie‐Weiss‐ähnliches Verhalten zu beobachten ist, zeigen die aluminiumreichen Legierungen einen verstärkten Pauli‐Paramagnetismus. Der Übergang von dem “magnetischen” zu dem “nichtmagnetischen” Verhalten verschiebt sich von 42 At.‐ % Al bei 5 At.‐ % Fe zu 58 At.‐ % Al bei 14 At.‐ % Fe. Bei geringen Eisenkonzentrationen läßt sich das magnetische Verhalten der kupferreichen Cu  Al  Fe‐Legierungen mit dem Anderson‐Modell für lokalisierte Momente beschreiben. Bei einer Zunahme der Eisenkonzentration tritt neben der s‐d‐Wechselwirkung zwischen den lokalisierten d‐Elektronen des T‐Metallatoms und den Leitelektronen noch eine Wechselwirkung zwischen den lokalisierten Zuständen auf. Diese Wechselwirkung kann sowohl einen indirekten (RKKY) als auch einen direkten Kopplungs‐Charakter haben. Durch eine Erweiterung des Anderson‐Modelles für den Fall konzentrierter Legierungen lassen sich auch diese Kopplungseffekte weitgehend erfassen und interpretieren.
Thermodynamische Untersuchungen der Struktur flüssiger binärer Legierungen am System Quecksilber‐Thallium
Authors: Sommer Ferdinand 
Published: September 2012

AbstractMit Hilfe der EMK‐Methode konnten die Konzentrationsfluktuationen 〈(Δc)2〉 für flüssige Quecksilber‐Thallium‐Legierungen bei Temperaturen zwischen 25 und 80°C und im Konzentrationsbereich 0 < CT1 < 0,45 direkt bestimmt werden. Die Resultate zeigen eine Hg3 Tl‐Verbindungstendenz. Aus den partiellen Strukturfaktoren aij(0) ergab sich eine bevorzugte Quecksilber‐Thallium‐Nachbarschaft mit einem Maximum bei 26 At.‐% Tl.
The Metal‐Nonmetal Transition in Liquid Semiconductors
Authors: Ten Bosch A. , Morán‐López J. L. , Bennemann K. H. 
Published: September 2012

AbstractWe approach the problem of the metal‐non‐metal transition in simple metal alloys from a chemical point of view and discuss the appearance of a gap in the electronic density of states in terms of covalency and ionicity as suggested by Pauling, Philips and others. In a simple model, we show that for sufficiently large splitting of the two pure component bands, and therefore for large differences in Pauling electronegativity, an energy gap appears in the electronic spectrum, leading to semiconductor behaviour at intermediary concentrations. The alloy electronic density of states is calculated with the truncated continued fraction method and the importance of charge transfer and short‐range order is emphasized.
Metal‐Nonmetal Transition in Metal‐Ammonia Solutions
Authors: Breitschwerdt K. G. , Radscheit H. 
Published: September 2012

AbstractThe properties of metal‐ammonia solutions in the concentration range of the metal‐nonmetal transition between 0.1 and 10 mol percent metal (MPM) are discussed. The high‐frequency electrical properties show a number of characteristic features in this intermediate concentration range, such as additional dielectric relaxations at about 0.1 MPM and 0.7 MPM for LiNH3 and NaNH3, respectively, and a resonance‐like behavior at about 1.0 MPM and 1.5 MPM for LiNH3 and NaNH3, respectively. For both LiNH3 and NaNH3 the real part of the high‐frequency dielectric function changes to large negative values around 2.5 MPM, indicating a transition to metallic behavior at high frequencies. The high‐frequency properties, which are also discussed in terms of electron conductivity, are explained quantitatively as a function of concentration, temperature, and frequency using a model of polaron hopping. The metal‐nonmetal transition is related to structural changes in the solutions which lead to phase separations in LiNH3 and NaNH3 at lower temperatures. The structural properties of the solutions are investigated using sound velocity and ultrasonic attenuation data. Concentration and temperature dependence of the ultrasonic attenuation in LiNH3 and NaNH3 can be described quantitatively in terms of structural fluctuation.
The Membrane/Water Partition Coefficients of Ions: Electrostatic Calculations of Dielectric Heterogeneity
Authors: Anderson J. E. , Pusch W. 
Published: September 2012

AbstractA continuum electrostatic calculation explores dielectric heterogeneity in membranes and its influence on ion sorption. The spherical shell model of Ullman is used. A transition in predicted sorption behaviour occurs as b, the mean ionic radius, becomes comparable with L, the size of dielectric domains. Since the finite size of molecules establishes a lower limit of L ˜ b, it is likely that no membrane is a strictly homogeneous dielectric from the standpoint of ion sorption. The calculation predicts that changing the dielectric domain size between 5 · 10−8 and 20 · 10−8 cm has a drastic effect on ion sorption. Objections which can arise from the very special nature of Ullman's model are discussed.
Electroluminescence at Semiconductor Electrodes Caused by Hole Injection from Electrolytes
Authors: Pettinger B. , Schöppel H.‐R. , Gerischer H. 
Published: September 2012

AbstractLight emission from semiconductors has been studied at semiconductor‐electrolyte interfaces, caused by minority carrier injection from the electrolyte at n‐type specimen of SnO2, ZnO, CdS, GaP, and GaAs. Species of very high electron affinity are normally required in order to inject holes into the deep lying valence band of SnO2, ZnO, CdS, and GaP, but such species are not stable in aqueous solution. The short living species SO˙4 and OH˙ were found to have a long enough lifetime to inject holes into these materials when they are generated at the surface by an electrochemical reaction. The luminescence spectra caused by such hole injection have been studied. One can conclude from the spectral distribution of the emitted light that surface states play an important role in this radiative recombination. The quantum efficiency of light emission is in the order of 10−4 or below and depends on the voltage applied. The influence of the energy position of the electronic states of the radicals and of the band edges of the semiconductors on luminescence intensity is analyzed.
Statistisch thermodynamische Berechnungen der Festkörpereigenschaften von Argon
Authors: Hebgen W. , Schäfer Kl. , Schramm B. 
Published: September 2012

AbstractIn der vorliegenden Arbeit wird gezeigt, wie aus dem zwischenmolekularen Paarpotential zweier Molekeln in der Gasphase auf die thermischen, mechanischen und kalorischen Eigenschaften der kondensierten Materie geschlossen werden kann. Die Berechnungen werden für Argon durchgeführt, da dessen zwischenmolekulares Potential kugelsymmetrisch ist und Quanteneffekte bei den Messungen makroskopischer Größen vernachlässigbar sind.
Reorientational Motions in Crystalline (CH3)3NHCl, Studied by Raman Spectroscopy
Authors: Schlaak M. , Couzi M. , Huong P. V. 
Published: September 2012

AbstractThe IR and Raman vibrational spectra of crystalline (CH3)3NH+X− (X = Cl, Br, I) are recorded. A complete assignment of the measured frequencies to the internal vibrational modes of the (CH3)3NH+ cation in the three compounds is obtained. Above the phase transition of (CH3)3NH+ Cl− (at 308 K) a reorientational motion of the cation around its threefold axis is deduced from the Raman spectrum. This motion is studied by a line shape analysis of the degenerate νCN(E) vibration. A rotational diffusion constant D∥ = (0.38 ± 0.05) · 1012 sec−1 is deduced in agreement with quasielastic neutron scattering results.
Differential Thermal Analysis (DTA) under High Pressure VI: Phase Transitions of Some Liquid Crystals up to 3 kbar
Authors: Spratte W. , Schneider G. M. 
Published: September 2012

AbstractWith a high pressure DTA apparatus previously described the phase transition temperatures solid/nematic (melting temperatures) and nematic/liquid isotropic (clearing temperatures) of the liquid crystals MBBA, EBBA, PBBA, PEBAB, PAA, and PAP were measured as a function of pressure up to 3 kbar and in the temperature range 273 K to 550 K. For PBBA the pressure dependence of the transition temperature smectic/nematic was additionally determined.For all compounds rising pressure causes an increase of the transition temperatures as well as an extension of the nematic range (especially for PAA and PEBAB). According to the thermal pretreatment two different melting curves were found for MBBA, EBBA and PEBAB separating the nematic liquid from a stable and a metastable solid phase respectively. The melting curves diverge slightly for MBBA and EBBA: for PEBAB, however, an intersection point can be extrapolated at about 2600 bar and 450 K.From the peak areas at atmospheric pressure the transition enthalpies ΔHand from these the transition entropies ΔSwere determined. Using these values and the slopes of the experimentalT(p)transition curves the volume changes ΔVaccompanying the transitions solid/nematic, smectic/nematic and nematic/liquid isotropic respectively were calculated from the Clausius‐Clapeyron equation. The ΔH, ΔSand ΔVvalues thus obtained are discussed and compared with the literature data available.
Photo‐Induced Oxydation of Carbonate Ions by Duroquinone, a Pathway of Oxygen Evolution from Water by Visible Light
Authors: Scheerer R. , Grätzel M. 
Published: September 2012

AbstractThe oxydation of carbonate, CO32‐, by triplet state duroquinone (DQT) was studied in aqueous micellar solutions of dodecyltrimethyl‐ammoniumchloride (DTAC) using laser photolysis technique. The primary step involves transfer of an electron from CO32‐ located in the micellar Stern layer to DQT residing in the interior of the micelle. This proceeds at an extremely rapid rate the reaction being completed within the 15 ns duration of the laser pulse. CO3− anion radicals formed in this redox process subsequently reduce duroquinone according to

with a rate constant of 2 ‐ 109 M−1 s−1 pulse radiolysis results substantiate the occurance of such an electron transfer process. The decomposition of CO3 leads to formation of oxygen and carbonate.
Molecular Dynamics Calculations for Liquid Neon and Methane
Authors: Hoheisel Claus 
Published: September 2012

AbstractMolecular dynamics calculations with 256 and 864 particles were performed for liquid methane, neon and for comparison also argon. Empirically determined Lennard‐Jones (12–6) potentials, theoretical Kim‐Gordon potentials and for neon the ‘best’ experimental pair‐potential were used as effective pair‐potentials.The known experimentally measured self‐diffusion coefficients and pair‐distribution functions were reproduced satisfactorily by the molecular dynamics calculations on methane between 95 and 170 K, on neon between 25 and 45 K and for argon in the region of 95 and 130 K. The Kim‐Gordon potential leads to the best agreement with experiment.Compressibility factors were only preliminarily calculated for high densities, they do not agree with the experimental data.
Rate Measurements for the Reactions H + NO2 → OH + NO and H + NOCl → HCl + NO by Lyman‐α Fluorescence
Authors: Wagner H. Gg. , Welzbacher U. , Zellner R. 
Published: September 2012

AbstractRate constants for the reactions of hydrogen atoms with NO2 (k2) and NOCl (k2) have been determined in a discharge flow system using the detection of H atoms by Lyman‐α resonance fluorescence. From temperature dependent measurements in the range T = 240 – 460 K the Arrhenius expressions (in units of cm3/mol · s)k1 = (4.3 ± 1.8) 1014 exp(–4.2 ± 0.7 kJ mol−1/RT) and k2 = (4.6 ± 1.2) 1013 exp(–3.8 ± 0.6 kJ mor−1/RT) could be obtained.
Temporal and Spatial Structures in Chemical Instabilities
Authors: Ross John 
Published: September 2012

AbstractWe discuss the formation of temporal and spatial structures in chemical systems far from equilibrium by means of the occurrence of instabilities. Multiple stationary states, hysteresis and oscillations of chemical species are cases of temporal structures and some simple models and experiments serve as examples. Chemical reactions and diffusion combine to yield macroscopic spatial structures such as periodic precipitation phenomena (Liesegang rings), chemical waves, and cooperative effects in fields of localized instabilities. We conclude with the close analogies between certain instability phenomena and the kinetic phase transitions.
Information, Memory and Statistical Theories of Elementary Chemical Reactions
Authors: Quack M. , Troe J. 
Published: September 2012

AbstractThe dissipation of information in collisions involving strongly bound intermediates is considered. A quantitative measure for the memory μ in such collisions is introduced. It is shown that the memory is important even for strong coupling situations where statistical theories may be valid. The relationship between various statistical theories for product state distributions, like phase space theory and the statistical adiabatic channel model, and the “prior distributions” in the information theoretic approach is discussed. The microcanonical equilibrium distribution is found to be theoretically unsatisfactory as a reference distribution. We propose replacing it by another distribution without memory and without dynamical constraints apart from angular momentum conservation. The concepts are illustrated with several simple model calculations for atom‐diatomic molecule collisions. The question of linear surprisal plots is discussed briefly.
Phänotypische Information von Nukleinsäuren: Die Initiationssignale für die RNA‐Replikation durch die Qβ‐Replikase
Authors: Küppers Bernd 
Published: September 2012

AbstractAn Viren lassen sich besonders gut die grundlegenden molekulargenetischen Prozesse wie Replikation, Transkription und Translation einschließlich deren Regulation untersuchen. Verhältnismäßig einfach aufgebaut sind die RNA‐haltigen Viren des Bakterienstammes Escherichia coli.Dic RNA‐Phagen besitzen eine bemerkenswerte Eigenschaft. Sie induzieren in der Wirtszelle jeweils eine RNA‐abhängige RNA‐Polymerase (Replikase), die spezifisch hinsichtlich der Replikation ihrer homologen RNA ist. Das RNA‐Replikationssystem des Bakteriophagen Qβ kann man isolieren und in vitro untersuchen.Mit Hilfe von synthetischen Nukleinsäuren läßt sich zeigen: Jedes Oligo‐ bzw. Polynukleotid, das eine 3′‐terminale CCC‐Sequenz und darüber hinaus eine zweite CCC‐Sequenz in eine definierte räumliche Anordnung zur Qβ‐Replikase bringen kann, dient als aktive Matrize für die Synthese einer komplementären Nukleinsäure.Durch entsprechende chemische Modifikationen kann man nunmehr Qβ‐inaktive Nukleinsäuren in Qβ‐aktive RNA‐Matrizen umwandeln. Damit besitzt man ein Verfahren für eine allgemeine RNA‐abhängige RNA‐Synthese.
Technische Informations‐Speicher
Authors: Kaufmann Hans 
Published: September 2012

AbstractDie wichtigsten Eigenschaften der Speicher für die Daten‐Verarbeitung sind Speicher‐Kapazität und Zugriffszeit; ihre Kenngrößen überdecken Bereiche von mehr als 10 Zehner‐Potenzen. Diese Speicher, die in sehr verschiedenen Technologien realisiert werden, kann man in grober Unterscheidung erfassen als Schnell‐Speicher (Zugriffszeit unter 1 Mikrosekunde, Kapazitäten bis zu wenigen Megabyte und Kosten von mehr als 1 Pf./bit) und als Massen‐Speicher (Zugriffszeiten über 1 Millisekunde, Kapazitäten über 30 Megabyte und Kosten von weniger als 1/100 Pf./bit). Die Schnell‐Speicher werden heute vollständig in Halbleiter‐Technologie verwirklicht: Stand und Zukunft werden dargestellt: dabei hat man zu erwarten, daß die Speicher‐Dichte auch weiterhin sehr erheblich ansteigen wird: Hand in Hand damit gehen die Bemühungen um die Herabsetzung des Leistungsbedarfs. Die Massen‐Speicher sind noch immer Magnetschicht‐Speicher; hier wird über den Stand berichtet und eine Darstellung der anderen technologischen Möglichkeiten gegeben.
Energiebedarf der molekularen Informationsübertragung
Authors: De Maeyer Leo C. M. 
Published: September 2012

AbstractTechnische Kommunikationssysteme verwenden in der Regel zeitlich diskontinuierliche oder modulierte Energieflüsse als informationsübertragende Signale. Für den Kommunikationsprozeß stellt sich die Frage, unter welchen Bedingungen ein maximaler Informationsfluß bei vorgegebenen Eigenschaften des Signalflusses bzw. des gesamten, einen Detektor erreichenden Energieflusses erreicht werden kann. Die optimale Ausnutzung eines vorhandenen Übertragungskanals ist eine Kernfrage der technischen Nachrichtenübertragung: sie führt zum Problem der Nachrichtenkodierung.Die chemische Spezifizität molekularer Wechselwirkungen und die Verkettung chemischer Umwandlungsprozesse im biologischen Be‐reich besitzen den Charakter eines molekularen Kommunikationssystems. Für die theoretische Untersuchung solcher Systeme stellt sich zunächst die Aufgabe, einfache Modelle zu definieren und die evtl. vorhandene Analogie mit den bereits eingehend untersuchten informations theoretischen Konzepten der Nachrichtentechnik zu analysieren.Die Frage nach dem grundsätzlichen Energiebedarf informationsübertragender Wechselwirkungen wird in der klassischen Informations‐theorie nicht gestellt. Sie hat jedoch für ein molekulares Kommunikationssystem eine besondere Bedeutung: hier steht das Problem des optimalen Ühertragungskanals für einen Informationsfluß vorgegebener Kodierung im Vordergrund. Es wird gezeigt, unter welchen Bedingungen der bei einem informationsübertragenden Prozeß entstehende Informationsgewinn mit prinzipiell dissipativem Energieaustausch verknüpft ist.
Model Orientation Dependent Pair Distribution Functions Describing the Association of Simple Carboxylic Acids and of Ethanol in Aqueous Solution
Authors: Hertz H. G. , Tutsch R. 
Published: September 2012

AbstractNuclear magnetic relaxation rates of the CH proton of formic acid and of the methyl and methylen protons of acetic, propionic, and butyric acid and of ethanol are reported. All these substances are dissolved in water (D2O) and the organic molecules are such that the hydrogen nuclei whose relaxation is not studied are deuterons. The corresponding deuteron relaxation rates (in H2O) have also been measured and the results are converted to yield the proton intramolecular relaxation rates and the intermolecular relaxation rates. Lastly, intermolecular proton relaxation rates which are caused by the interaction with protons in other groups have been measured. All these data are given as a function of the acid mole fraction x2. From these experimental results first coordination numbers of the acids with respect to the acid and closest distances of approach between the various hydrocarbon groups have been derived. Model molecular pair distribution functions have been constructed which show that propionic acid and butyric acid molecules undergo a change in the relative pair configuration as more and more water is added such that a side by side configuration of the hydrocarbon rests is produced. In the ethanol water mixture the structural change is the reverse one and here no hydrophobic association is observable.
An Investigation of the Structure of Acetic Acid and the Mixture Acetic Acid/CCI4 by the Nuclear Magnetic Relaxation Method
Authors: Berg V. , Hertz H. G. , Tutsch R. 
Published: September 2012

AbstractIntermolecular proton magnetic relaxation rates of the methyl and hydroxyl group of acetic acid involving the magnetic interaction among the various groups are reported. The data are given as a function of the mole fraction in the mixture acetic acid/CCI4. From these experimental results model atomic pair distribution functions and model molecular pair distribution functions are derived. It is shown that in the pure acid OH and CH3 never approach closely towards one another. At mole fractions x2 ≤ 0.3 the classical dimer can be observed which, however, appears in a more or less folded form.
Fluid Mixtures at High Pressure. Phase Separation and Critical Phenomena in Binary Mixtures of a Polar Component with Supercritical Carbon Dioxide, Ethane, and Ethene up to 1000 Bar.
Authors: Alwani Ziad , Schneider Gerhard M. 
Published: September 2012

AbstractIn order to study the polarity effect on the critical phase behaviour of fluid binary systems the critical temperatures of binary mixtures of carbon dioxide, ethane, ethene, hexane, or 1‐hexene with a second component of very different polarity such as methanol, 2‐hexanol, 2‐octanol, 2,5‐hexanediol, nitromethane, N,N‐dimethylformamide, or N‐methylacetamide were determined as a function of pressure up to 1000 bar. The critical p(T) curves obtained exhibit a whole pattern of different transition types between liquid‐gas, liquid‐liquid, and gas‐gas equilibria; they are compared with data for other systems taken from the literature.The results verify a previous hypothesis that there are continuous transitions between liquid‐gas, liquid‐liquid, and gas‐gas critical phenomena in fluid binary mixtures at high pressures. The measurements are of interest for fluid extraction and supercritical fluid chromatography (SFC).
Fluid Mixtures at High Pressures. Computer Calculations of the Phase Equilibria and the Critical Phenomena in Fluid Binary Mixtures from the Redlich‐Kwong Equation of State
Authors: Deiters U. , Schneider G. M. 
Published: September 2012

AbstractUsing the Redlich‐Kwong equation of state (RK‐equation) thermodynamic relations are derived from which the phase equilibria and the critical phenomena in fluid binary systems can be calculated at high pressures.From these relations p‐T diagrams and p‐x diagrams are calculated for binary mixtures with components differing considerably in structure, molecular size and/or polarity (80K to 500 K; up to 3 kbar); quadratic mixing rules are assumed for the two parameters of the RK‐equation. All kinds of phase equilibria and critical phenomena hitherto known can be represented in reasonably good agreement with experimental data.
The Molecular Structure of Allenes and Ketenes VII [1] 13CH Nuclear Spin‐Spin Couplings in Monosubstituted Allenes
Authors: Runge W. , Kosbahn W. 
Published: September 2012

AbstractFrom high‐resolution 13C‐NMR spectra direct and long‐range (up to four‐bond) carbon‐proton coupling constants of allenes have been obtained. Relative signs of the coupling constants have been determined relating them to the (absolute) signs of couplings in selected model compounds.The substituent effects on the coupling constants are discussed in terms of empirical correlations with other molecular properties of allenes or usual substituent increments, and on the basis of the independent‐electron MO treatment of the Fermi contact term using CNDO/S wave functions.Spin density information via π‐type conjugation plays an important role for many kinds of carbon‐proton couplings in allenes.
Eine unbekannte Magnetfeldabhängigkeit des Faradayeffekts
Authors: v. Löwis Michael 
Published: September 2012

AbstractIm Faradayspektrum von Benzol, Anthracen und Naphthalin wurde ein Anteil entdeckt, dessen Vorzeichen unabhängig von der Magnetfeldrichtung ist (parallel oder antiparallel zum Lichtstrahl). Dieser Anteil hängt ebenfalls linear von der Magnetfeldstärke ab. Er läßt sich experimentell vom feldrichtungsabhängigen Effekt abtrennen. In der Theorie des Faradayeffekts existiert ein Term, auf den der feldrichtungsunabhängige Effekt zurückgeführt werden kann.