bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stoffbestand und Entwicklung des äußeren Erdkörpers
Authors: Wedepohl Karl Hans 
Published: March 2014

AbstractThe three major units of the earth are the core, the mantle and the crust. The material of the earth's mantle and core originated 4.6 billion years ago from condensation products of solar gases. The continental crust is on the average 40 km thick and varies in composition and age (≤ 3.8 · 109 years) while the present oceanic crust is about 7 km thick, composed mainly of basalt and less than 200 million years old. The renewal and the growth of the oceanic crust from partial melting of peridotites in the upper mantle is observable in the basaltic magmatism at mid‐ocean ridges and in the drift of the continents (˜ cm per year). The crustal growth is compensated by subduction of crustal plates into the mantle at some continental margins such as in the Circum‐Pacific. The oceanic basalts gain water through reactions with sea water and lose this during subduction (at about 900°C) to the overlying mantle materials (peridotites). Partial melting of mantle materials (and differentiation of primary melts) results in the formation of basaltic, andesitic or other magmas and contributes substantially to the growth of the continents. This direct or indirect origin of andesitic magmas from water containing peridotites is explained on the base of melting experiments and partition data of trace elements between melts and their potential source rocks. The majority of minerals in magmatic rocks are not stable under earth's surface conditions. They react with the degassing products of the earth's mantle (H2O, CO2, SO2, HCl) and with photochemically produced oxygen to form weathering and sedimentary minerals (OH containing silicates, CaCO3, CaSO4, NaCl etc.). Erosion, water transport and sedimentation control the material balance of elements near the earth's surface. The original sediments which contain water and other specific compounds are buried with time in deeper and warmer crustal levels. Their minerals reequilibrate at increasingly higher temperatures and pressures. Finally at 600–700°C, depending on the availability of water, they partially melt to form granitic magmas. The difference in density between the source rocks and the melts causes the uprise of granitic magmas. This process results in a chemical fractionation between the lower and the upper continental crust over long geologic time. – Summarizing the important observations of this report, water has controlled major processes in the outer shells of the earth.
Hydrothermal Solutions
Authors: Tödheide K. 
Published: March 2014

AbstractA survey is given of recent results on the properties of pure water and binary and ternary mixtures at high temperatures and high pressures with emphasis on the geochemically important systems H2O‐CO2, H2O‐NaCl, and H2O‐CO2‐NaCl. Among the properties discussed are phase diagrams,PVTxdata, thermodynamic and transport properties, dielectric constant, electrical conductivity, and ionic equilibria. Concepts for predictive calculations of thermodynamic properties are briefly described.
Physical and Chemical Changes in Natural Fluids in Hydrothermal Processes and Mineral Deposition, Studied with Fluid Inclusions
Authors: Weisbrod Alain 
Published: March 2014

AbstractThe part played by the fluid phase(s) in most geological processes is of primary importance. These fluids have been often trapped in usually microscopic “fluid inclusions” which are considered as good samples of the natural solutions that once “wet” the rocks, with a few exceptions that can be easily detected. Once it has been trapped, the bulk composition and the bulk density of the inclusion fluid remain constant. – The major purpose of a fluid inclusion study is to determine the nature and the physical and chemical properties of the trapped fluids, and then to fit these properties with relevant geochemical processes. This is largely obtained by microthermometry, which consists in measuring the temperature of all the phase transitions observed in the inclusions when heated from −150°C to 700°C or more. Because fluid inclusions are assumed to be isochemical‐isochore univariant systems in the TPVX space, the microthermometry data can be interpreted in terms of chemical composition and molar volume. These data can be completed by other analytical techniques, such as bulk chemical analyses and Raman Microprobe analyses. – The first example presented in this paper deals with the postmagmatic hydrothermal alteration of a pegmatite. Because of the density‐composition constraints derived from fluid inclusions study, the TP cooling path of the fluid can be estimated with a fairly good accuracy between 500 and 200°C. Taking into account this result and the bulk chemical analyses (Cl, Na, K, Mg, Ca), it is possible to calculate the whole mass transfer and the water/rock ratio all over the evolution. – The second example, very briefly summarized, concerns fluid unmixing in porphyry copper type deposits. Such a process yields highly saline brines of moderate density and diluted vapour with low density. It is responsible of part of the mineral deposition, as a consequence of the supersaturation of the “boiling” liquid with respect to chalcopyrite. – The last example is related to the fluid evolution in a tin and tungsten deposit associated with a shallow granitic intrusion from Central Morocco. It is shown, mainly from fluid inclusion study, that the original fluid composition (70% water, 24% CO2, 5% N2, 1% CH4, traces of C2H6 and H2S) is changed by mixing with a slightly saline (5 wt% NaCl) aqueous solution. The composition of the volatile part (relative amounts of CO2, N2, CH4) has been analyzed by Raman spectroscopy. – Ore deposition occurred during this mixing process. Because of the lack of accurate experimental data on the system H2O – CO2 – N2 – (CH4) – NaCl, the TP conditions of the evolution cannot be accurately estimated, and using the system H2O – CO2 – NaCl as an approximation yields irrelevant results. This last example clearly shows why the availability of relevant experimental data on the C – O – H – N electrolytes systems is crucial for geochemists that deal with the fluid‐rocks interactions.
Raman Spectra of Hydrothermal Solutions of CO2 and KHCO3 at High Temperatures and Pressures
Authors: Kruse R. , Franck E. U. 
Published: March 2014

AbstractRaman spectra of H2O – CO2 mixtures (3 mol‐% CO2) and of 2 molal aqueous KHCO3 solutions have been measured to 300°C and 2000 bar, thus covering a range of geochemical interest. A high temperature, high pressure, corrosion resistant Raman cell with sapphire windows and auxiliary equipment is described. The C – OH stretching vibration υ5(A′) at 1017 cm−1 is particularly characteristic of H2CO3 and HCO3− species. Its frequency and intensity decrease with temperature. H2O – CO2 mixtures at room temperature and about 1000 bar show a small but distinct band at 1017 cm−1 which is considered as indicating the formation of 2 to 3 percent of carbonic acid from the dissolved CO2. This is in qualitative agreement with a reaction volume of −12 cm3 mol−1 for the hydration process.
Preparation and Some Properties of a New Solid Sodium‐Ammonia Compound Na(NH3)3
Authors: Winter R. , Schindewolf U. 
Published: March 2014

AbstractThe preparation of solid Na(NH3)3 from sodium ammonia solutions is described. The very slow rate of formation (even in the presence of nuclei for crystallization) is attributed to a high energy and entropy of activation, other factors contributing to it. This new blue compound crystallizes in a primitive cubic structure with a lattice constant of 5.1 Å; it is probably isotype with AuCu3. Thermodynamic data indicate that its stability with respect to decay into metallic sodium and liquid ammonia (or a concentrated sodium ammonia solution) decreases with decreasing temperature (ΔH0 und ΔS0 of formation from sodium and liquid ammonia being positive); however by fast cooling in liquid nitrogen it can be stored as a metastable state. In this state the compound is diamagnetic (perhaps antiferromagnetic) and has the conduction behavior of a semiconductor.
NMR Study of Molecular Motion and Rotational Tunnelling in Co(NH3)6Cl3
Authors: Germer Hildegard , Müller‐Warmuth W. 
Published: March 2014

AbstractMolecular motions in hexammine cobalt chloride have been studied over a wide range of temperatures using wide‐line and pulsed 1H NMR techniques. From five well‐defined plateaus in the temperature dependence of the second moment and from four relaxation peaks information about various rotational processes has been obtained on the basis of the known crystal structure. Assignment of the data has been made to the one‐dimensional rotation or tunnelling of NH3 groups (activation energies 5.6 and 11 kJ/mol), respectively) and to the three‐dimensional rotation of four nonequivalent Co(NH3)3+6 octahedra (activation energies 19, 34, 41, and 47 kJ/mol, respectively). Rotational tunnelling of NH3 groups is discussed in some detail.
Electrotransport in Molten Tl – Te Alloys
Authors: Nakamura Yoshio , Kitazawa Yukiharu , Shimoji Mitsuo 
Published: March 2014

AbstractThe electrotransport in molten Tl – Te alloys has been studied at 500°C. The effective charge, electric mobility and diffusion coefficient of Tl have been determined for compositions TlTe2, TlTe, and Tl2Te. Tl atoms migrate always to the cathode and the observed effective charge is the largest at the composition Tl2Te, in reasonable agreement with the electrical and thermodynamic properties of this system.
Aerosole
Authors: Wagner P. E. 
Published: March 2014

AbstractThe term aerosol designates a suspension of solid or liquid particles in a gas. The properties of aerosols have been investigated by many authors. The dynamics of aerosol particles is influenced by the interactions with the ambient gas, which are dependent on the Knudsennumber (mean free path of the gas molecules/particles radius). Presently many investigations are in progress dealing with diffusion and coagulation in ultrafine aerosols and the influence of electrical and van der Waals forces. For many applications the scattering of light by aerosol particles is important, which depends on the particle size parameter (particle circumference/light wavelength). Formation and evolution in time of aerosol particles are influenced by condensation processes. Particularly heterogeneous nucleation on ultrafine particles and homogeneous nucleation are presently investigated by many authors. Besides the investigations of the physico‐chemical properties of aerosols, a number of aerosol measuring techniques have been developed, which are of great practical importance particularly in view of the increasing problem of atmospheric air pollution.
Disperse Festkörper als Katalysatoren
Authors: Mroß W. D. 
Published: March 2014

AbstractThe activity of a catalyst increases as the degree of dispersion of the active component increases. In the case of supported catalysts it is possible to achieve dispersion right down to single active atoms. On the other hand, the smallest individual units of pure substances which can be obtained are generally 1 — 10 nm crystals. These finely dispersed systems can be stabilized by admixture with just small quantities of foreign substances. At temperatures above 600°C certain metal catalysts are capable of undergoing spontaneous dispersion under reaction conditions. — The degree of dispersion and the specificity of a catalyst are interrelated in a complex manner. Certain so‐called demanding reactions proceed most readily on finely dispersed systems (with low‐indexed crystallographic faces), others on coarsely dispersed active components (with predominantly highly‐indexed faces). — Although the selectivity of reactions taking place on model catalysts frequently correlates with the degree of dispersion, such a relationship has only seldom been observed in the case of technical catalysts.
Light Induced Viscosity Changes and Phase Transitions in Aqueous CTAB‐Solutions Containing Aromatic Molecules
Authors: Wolff Thomas , von Bünau Günther 
Published: March 2014

AbstractDynamic viscosities of aqueous solutions containing 0.25 M cetyltrimethylammonium bromide (CTAB) and small amounts of several aromatic compounds (anthracene, 9‐methylanthracene, 9,10‐dimethylanthracene, 9‐anthracene carboxylic acid, phenanthrene, 1‐methylphenanthrene, pyrene, fluorene, N‐methyldiphenylamine, naphthalene, 1‐methylnaphthalene, 2‐methylnaphthalene, acenaphthylene) were measured. Some compounds (9‐methylanthracene, 9‐anthracene carboxylic acid, phenanthrene, 1‐methylphenanthrene, pyrene, N‐methyldiphenylamine, naphthalene, 1‐methylnaphthalene, 2‐methylnaphthalene, acenaphthylene) enhance the viscosity of the CTAB‐solution while the others do not. A few of these Theologically effective substances (9‐methylanthracene, 9‐anthracene carboxylic acid, N‐methyldiphenylamine, acenaphthylene) can be converted photochemically to ineffective ones and vice versa. The influence of these substances on the position of the phase transition point isotropic solution/lyotropic liquid crystal was studied. Phase transition temperatures are altered upon addition of certain substances. Photochemical transformation of some additives may trigger the phase transition in both directions.
Fluorescent Dye in Soap Lamella as a Probe of the Electrical Potential
Authors: Fromherz Peter , Kotulla Reinhard 
Published: March 2014

AbstractThe electrical potential in a thin soap film stabilized by tetradecyltrimethylammoniumbromide is determined by a fluorescent dye. The fluorescence intensity exhibits a “beating” pattern as a function of the thickness of the lamella. This pattern is assigned to the interference of the exciting light and of the emitted light. The quantitative evaluation proves the localization of the dye in the surface layers of the lamella. The pH‐dependent fluorescence of the dye indicates a surface potential of 175 mV, corresponding to a dissociation degree of the ionic surfactant of 0.5. This potential is distinctly higher than the values determined on the basis of the DLVO‐theory.
Analysis of the Pathways for Cis ⇄ Trans Photoisomerization of 4‐Nitro‐,4,4′‐Dinitro‐, and 4‐Nitro‐4′‐methoxystilbene in Solution. XII1
Authors: Görner Helmut 
Published: March 2014

AbstractQuantum yields for the direct trans → cis (Φl→c) and cis → trans (Φc→l,) photoisomerization of 4‐nitro‐,4,4′‐dinitro‐, and 4‐nitro‐4′‐methoxystilbene (NS, DNS, and NMS, respectively) were measured in solution at room temperature as a function of the concentration of quenchers (ferrocene, azulene, and oxygen). The results are in full agreement with a previously proposed reaction scheme for NMS, involving a triplet state as an intermediate in the trans → cis photoisomerization and both triplet and excited singlet states in the cis → trans photoisomerization. The branching ratios for decay of twisted configurations of the first excited singlet (1p*) and the lowest triplet (3p*) into the ground states and the yields for intersystem crossing from the first excited trans and cis singlet configurations to the lowest triplet state (Φlisc and Φcisc, respectively) were determined. Φlisc and Φcisc are large (0.45–0.86) for NS and DNS and significantly smaller for NMS in polar solvents. Since the trans triplet state (3t*) is in thermal equilibrium with 3p* it is this 3t* ⇄ 3p* equilibrium which is accessible for the influence of triplet quenchers and solvent properties in the cis ⇄ trans photoisomerization. At room temperature oxygen quenches mainly 3p* while at lower temperatures (between 0 and — 140°C) also3t* is quenched. The yields for the conversion 1t* → 1p* and for formation of 4a,4b‐dihydrophenanthrene (DHP) are small. From the kinetic analysis no indication was found for involvement of excited states of DHP in the cis → trans photoisomerization of 4‐nitrostilbenes.
Study of a Binary Critical Mixture of 2,6‐Dimethyl Pyridine/Water: Measurements of Static and Dynamic Light Scattering and Specific Heat Near the Lower Critical Point
Authors: Jungk M. , Belkoura L. , Woermann D. , Würz U. 
Published: March 2014

AbstractStatic and dynamic light scattering experiments are reported for the system 2,6‐dimethyl pyridine/water to determine the critical amplitude ζo of local concentration fluctuations and the critical amplitude Ωo of the characteristic frequency ΩD to scale ultrasound absorption data. It is found: ζo = (2.7 ± 0.2) · 10−8 cm and Ωo/π = 2.9 GHz. Measurements of the temperature dependence of specific heat capacity at constant pressure lead to a critical amplitude A = (0.183 ± 0.002) J g−1 K−1. The two scale factor universality is tested by combining the values of ζ0 and A as well as the values of ζ0 and τ*0 and B* (B*: critical amplitude of the coexistence curve, τ*0 critical amplitude of turbidity). The two ratios of the critical amplitudes calculated from the experimental data are higher by about 15% than the highest theoretical predicted value.
Ion‐Solvent Interactions in Water‐Acetamide Mixtures from Volume Data
Authors: Woldan Marian 
Published: March 2014

AbstractDensities of solutions of NaCl, NaI, KCl, KBr and CsI in mixtures of water + acetamide have been measured at 348.15 K using the magnetic float densimeter. The apparent molal volumes of the electrolytes calculated from the experimental data were extrapolated to infinite dilution by means of the Masson equation. The ionic partial molal volumes of alkali‐metal and halide ions have been estimated. The partial molal volumes of transfer of ions from water to water‐acetamide mixtures were separated into the two components: V̄0elect(tr) and V̄0disord(tr). The effect of acetamide and temperature on V̄0elect(tr) and V̄0disord(tr) in the temperature range 298.15 — 348.15 K is discussed.
Thermodynamics of Non‐Isothermal Coadsorption Processes
Authors: Keller J. U. 
Published: March 2014

AbstractPhysical adsorption processes from a multi‐component fluid phase to the internal, inert surface of a single pellet of an adsorbens are considered. — Using the formalism of a generalized thermodynamics of irreversible processes, originally development by Meixner, a set of differential and algebraic equations is established from which the masses of the various components of the adsorbate and its temperature can be calculated. Numerical examples referring to adsorption/desorption processes of an ideal gas mixture of N2/CO2 on active coal “Aerosorb LR4” are given and discussed. It is demonstrated that considerable differences between a non‐isothermal coadsorption process and its isothermal approximation can occur. Finally, we consider a pressure‐swing adsorption‐desorption process for removing CO2 from a mixture of N2/CO2. Within an optimization procedure for the process it turns out that thermal effects can be essential if not decisive for the performance of the process.
Static Dielectric Constant and Density of Supercritical Methane‐Methanol‐Mixtures to 200 MPa
Authors: Diguet R. , Deul R. , Franck E. U. 
Published: March 2014

AbstractThe static dielectric constant (permittivity), ε, and the molar volume of supercritical, homogeneous mixtures of methane and methanol were measured at 323 K and 398 K from 50 to 200 MPa over the whole composition range between pure methane and pure methanol. Both quantities were determined simultaneously with the same samples in one autoclave which served as high pressure dilatometer and capacitor. At 398 K and 200 MPa ε increases from 1.53 (methane) to 23.2 (methanol). The measured mixture ε‐values are always below the linear interpolation line. Excess volumes of the mixtures are negative. At constant composition and temperature, ε always increases linearly with increasing density. With the Onsager‐Kirkwood‐Fröhlich relation, dielectric correlation factors, g, have been derived. At constant T and P the g‐values as function of composition give an s‐shaped curve from methane (g = 1) to methanol (g ≈ 2.6). This polar‐nonpolar supercritical combination is one of the very few systems for which the dielectric behaviour in dependence of temperature, total density and the complete concentration range could be studied.
Photochemistry of semiconductor colloids. 17. Strong luminescing CdS and CdS‐Ag2S particles
Authors: Spanhel L. , Weller H. , Fojtik A. , Henglein A. 
Published: March 2014

AbstractThe luminescence of colloidal CdS in solutions containing sodium polyphosphate as stabilizer is activated by the addition of either Ag(ClO4) or colloidal Ag2S. The degree of activation depends on how strongly the CdS and Ag2S particles are attached to each other, and this attachment is controlled by the concentration of polyphosphate and added divalent metal ions which bind to polyphosphate. The CdS fluorescence in these solutions can be excited by light of wavelengths longer than the wavelength of the absorption edge of CdS. The results are explained in terms of an interfacial region in which anion vacancies and incorporated silver centers, which deliver electrons into the conduction band of CdS upon illumination with photon energies less than the bandgap energy of CdS, are present. The preparation of Q‐CdS sols which fluoresce with quantum yields close to 100% is also described. Strong fluorescence occurs when defect sites, at which radiationless recombination takes place, are blocked.
The analysis of the small‐signal AC‐response of bovine enamel membranes
Authors: Scholberg H. P. F. , Borggreven J. M. P. M. , Driessens F. C. M. , Schoonman J. 
Published: March 2014

AbstractThe ion permeability of bovine enamel membranes can be estimated from impedance spectroscopy. In this study the 6‐parameter model, a previously proposed operational description of the frequency dependence of the impedance of an enamel membrane is compared with a model which uses a Constant‐Phase‐Angle (CPA) element, and which is proposed as an onset to a more mechanistic description of enamel impedance spectra The model using the CPA element is shown to be a valid description for the measured impedance data. The parameter values for R0 and ωmax (the angular measuring‐frequency where the imaginary part of the membrane‐impedance is maximal) obtained using this model, confirm that these parameters can be employed as predictors for bovine enamel permeability.
Theory of scaling for fluctuations in thermal explosion conditions
Authors: Fernandez Ariel 
Published: March 2014

AbstractWe demonstrate that fluctuations in the transient bimodality regime for gaseous thermal explosions scale with the inverse of an effective size parameter Ω. The ratio between this parameter and the volume V is obtained analytically for a nonturbulent heat conduction regime. We show that as the system departs from the laminar flow limit towards a turbulent regime, the fluctuations are enhanced since Ω decreases. We also prove that as V tends to zero, the ratio Ω/V tends to one, an intuitively expected result. The theory is inspired and confirmed by experiments on the decomposition of ethyl azide. Within the induction period, we use a corrected parabolic approximation for the potential determining the drift term in the Fokker‐Planck equation. The maximum occurs at the ignition temperature. The correction arises from size effects (Ω/V ≠ 1) due to an inhomogeneous distribution of temperature. The parabolic approximation is valid only within the induction period, until the fluctuations have macroscopic consequences. Our study reveals that the following anomalies bear a common origin that can be explained quantitatively if the correction is introduced: a) Discrepancy between the experimental and theoretical value for the Frank‐Kamenetsky constant. Early work by O.K. Rice on the gaseous thermal explosion of ethyl azide indicates that this discrepancy is enhanced when the size of the vessel increases. — b) Reduction of the induction period, or, equivalently, contraction of the time‐scale for the transient bimodality during which heat accumulates in the system. This anomaly is accompanied by an enhancement of the growth rate for the Gaussian width of the probability density distribution for the temperature due to fluctuations. This phenomenon will be interpreted by the observer as a premature ignition.