Search results for "MINERALOGY"
showing 10 items of 1516 documents
Continuum-uniform approach calculations of the solubility of hydrocarbons in water
1993
Abstract The ransfer free energies from gas phase to water for some hydrocarbons are calculated by means of a continuum-uniform model of the solvent. For the calculation of the cavitation energy a model based on the surface tension is proposed. The calculated values are compared with the experimental free energies obtained with and without a corrective factor that accounts for the difference in the solute—solvent sizes. Good agreement between the theoretical free energies and the corrected experimental data is obtained. Our calculations seem to show that the hydrophobic effect is directly related to the molecular surface area.
Single particle jumps and correlated ionic motions in glass-ceramics
1993
Using impedance spectroscopy, the ion transport in poorly Li-conducting aluminosilicate glass ceramics and their precursor glasses has been measured for temperatures 50 K < T < 550 K and covering a frequency range of more than 14 decades from 10 mHz up to 3 THz. In addition to the familiar cooperative ionic motion dominating at high temperatures, for the first time dielectric relaxation due to elementary hopping processes is observed well below room temperature.
Influence of HCl pretreatment and organo-mineral complexes on laser diffraction measurement of loess–paleosol-sequences
2016
Abstract The influence of different sample pretreatment methods on grain size distributions in particle size analysis has been subject to controversial discussions. Standard sample preparation typically comprises the disaggregation of aggregated and agglomerated particles into single primary particles, i.e., the organic binding material is oxidized by hydrogen peroxide (H2O2) and the contained carbonates are dissolved by hydrochloric acid (HCl). The aim of this study is to evaluate the effects of HCl treatment on grain size analyses of Late Pleistocene and Holocene loess–paleosol-sequences investigated by a Beckman Coulter LS 13320 laser particle analyzer. For this purpose, samples from two…
ESR of Nd3+ in BaTiO3
1990
Afin d'identifier les defauts responsables de l'effet photo-refractif dans BaTiO 3 , on etudie ces cristaux. Les echantillons contiennent generalement divers etats de charge et des associations de Fe, Cr, ainsi que des trous de O − induits par le rayonnement. On trouve un nouveau centre qui doit etre attribue a Nd 3+ . Dans la presente etude, l'echantillon utilise n'est pas dope, et on l'etudie dans la phase rhomboedrique a T∼77 K. Il apparait que Na est une impurete courante dans BaTiO 3 probablement incorporee avec le materiau de depart, BaCO 3
Species-specific aggregation factor in sponges : VIII. Nature and alteration of cell surface charge.
1977
Isolated cells from the siliceous spongeGeodia cydonium have been studied with respect to their partition behaviour in a two-phase aqueous polymer system. With this method it is possible to determine subtle changes in the cell surface charge. Addition of a homologous aggregation factor to the isolated cells lowers the partition rate, a finding which indicates that after binding of the aggregation factor to the cells their surface charge is reduced. The partition rate of the cells is strongly correlated with their content of membranebound sialic acid. Sixty-nine percent of the total, membrane-bound hexuronic acid is associated with the aggregation receptor; 1.8×107 aggregation receptor molec…
Sulfide mineral identification using laser-induced plasma spectroscopy
2003
Sulfide minerals in rock samples were identified with laser-induced plasma spectroscopy (LIPS) in the near vacuum ultraviolet spectral region. Reference spectra of pyrite, pyrrhotite, chalcopyrite, sphalerite, barite, calcite and dolomite were applied to classification of minerals in sulfur-bearing drill core samples. On the basis of the results mineral distributions in the sample were estimated. The potential of the LIPS method for in situ analysis is discussed.
Microbial origin for pedogenic micrite associated with a carbonate paleosol (Champagne, France)
1999
Abstract Micro-rods have been observed in indurated carbonate horizons (30 cm thick) that overlie a periglacial chalk formation, in contact with the present-day soil (Champagne, France). They are numerous in the upper part of the hardened layers. Variations in micro-rod morphologies are related to progressive biomineralization of organic matter, transforming purely organic rods into calcite. Mineralized rods undergo diagenesis and their arrangement evolves from a random mesh fabric to recrystallized micritic platelets to microsparite. Two types of organic micro-rods have been observed: bacilliform and thread-like bacteria. Mineralogically, micro-rods are low-magnesian calcite. Crystallograp…
Molecular dynamics of supercooled polymer films
2000
We present results of molecular dynamics simulations for a supercooled polymer melt confined between two smooth and purely repulsive walls. The thickness D of the film is about 7 times the bulk radius of gyration. For all temperatures studied, a significant increase of the monomer and chain mobilities with respect to the bulk is observed. Preliminary results suggest that structural relaxation times exhibit a power-law behavior in the vicinity of a critical temperature T c (D) 0.39 (in Lennard-Jones units). This estimate of T c (D) is about 14% smaller than the corresponding bulk value. Despite this significant decrease the time dependence of various mean-square displacements seems to be una…
Influence of land use on the characteristics of humic substances in some tropical soils of Nigeria
2005
Summary In highly weathered tropical conditions, soil organic matter is important for soil quality and productivity. We evaluated the effects of deforestation and subsequent arable cropping on the qualitative and quantitative transformation of the humic pool of the soil at three locations in Nigeria. Cultivation reduced the humic pool in the order: acetone-soluble hydrophobic fraction (HE) > humic acid (HA) > humin (HU) > fulvic acid (FA), but not to the same degree at all three sites. The C and N contents, as well as the C/N ratios of humic extracts, were large and not substantially influenced by land use. The δ13C values of the humic extracts were invariably more negative in forested soil…
Shear Effects on the Phase Diagrams of Solutions of Highly Incompatible Polymers in a Common Solvent. 1. Equilibrium Behavior and Rheological Propert…
1997
Phase diagrams (cloud points, tie lines, critical compositions) and viscosities of homogeneous solutions were determined at temperatures ranging from 20 to 100 °C for three representatives of the ternary system cyclohexanone/polystyrene/poly(n-butyl methacrylate) [CHO/PS/PBMA] in preparation of a study on shear influences. An only moderate increase of the two-phase region observed upon heating (LCST behavior) witnesses little heat effects upon mixing. Tie lines which are nearly parallel to the PS/PBMA edge of the Gibbs phase triangle indicate comparable solvent quality of CHO for both polymers. The quantitative mathematical description of the equilibrium behavior-required for a theoretical …