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See detailMagma chamber processes in the Tellnes ilmenite deposit (Rogaland Anorthosite Province, SW Norway) and the formation of Fe-Ti ores in massif-type anorthosites
Charlier, Bernard ULg; Duchesne, Jean-Clair ULg; Vander Auwera, Jacqueline ULg

in Chemical Geology (2006), 234(3-4), 264-290

The origin of igneous Fe-Ti oxide ores associated with massif-type anorthosites is investigated through a detailed study of the world-class Tellnes ilmenite deposit, part of the late-Proterozoic (930-920 ... [more ▼]

The origin of igneous Fe-Ti oxide ores associated with massif-type anorthosites is investigated through a detailed study of the world-class Tellnes ilmenite deposit, part of the late-Proterozoic (930-920 Ma) AMC series of the Rogaland Anorthosite Province (SW Norway). More than 100 samples from drill cores reveal significant petrographical and compositional variations within the ore body. Four zones are defined, based on variations in modal proportions and cumulus mineral assemblages: the Lower and Upper Central Zones and the Lower and Upper Marginal Zones. Plagioclase and whole-rock compositions discriminate the zones and display patterns interpreted as a result of mixing of either plagioclase-ilmenite or plagioclase-ilmenite-orthopyroxene-olivine cumulates with a melt of ferrodioritic (jotunitic) composition with a content decreasing from 80 to 20% from the margins to the central part of the ore body. Phase diagrams for a jotunitic parental magma reproduce the crystallization sequence at 5 kb. The orthopyroxene-olivine liquidus boundary is a peritectic in the Bjerkreim-Sokndal layered intrusion and a cotectic in Tellnes and this explains the differences in the sequence of crystallization of the two intrusions. The high concentration of ilmenite, well above cotectic proportions, resulted from gravity-sorting in the Tellnes ore body, which represents the lower part of a larger magma chamber. Uniform Sr isotope ratios do not support magma mixing. The cryptic layering of the ore body precludes injection as a crystal mush but favours in situ crystallization from an evolving magma in a sill-like magma chamber. The present trough-shape and mineral orientations result from deformation during gravity-induced subsidence and by up-doming of the anorthosite. Fractional crystallization of a TiO2-rich magma with ilmenite as an early liquidus mineral and plagioclase buoyancy are the principal mechanisms responsible for the formation of Fe-Ti deposits in Proterozoic massif-type anorthosites. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailMagma chamber-scale liquid immiscibility in the siberian traps represented by melt pools in native iron
Kamenetsky, V. S.; Charlier, Bernard ULg; Zhitova, L. et al

in Geology (2013), 41(10), 1091-1094

Magma unmixing (i.e., separation of a homogeneous silicate melt into two or more liquids) is responsible for sudden changes in the evolution of common melts, element fractionation, and potential formation ... [more ▼]

Magma unmixing (i.e., separation of a homogeneous silicate melt into two or more liquids) is responsible for sudden changes in the evolution of common melts, element fractionation, and potential formation of orthomagmatic ore deposits. Although immiscible phases are a common phenomenon in the mesostasis of many tholeiitic basalts, evidence of unmixing in intrusive rocks is more difficult to record because of the transient nature of immiscibility during decompression, cooling, and crystallization. In this paper, we document a clear case of liquid immiscibility in an intrusive body of tholeiitic gabbro in the Siberian large igneous province, using textures and compositions of millimeter-sized silicate melt pools in native iron. The native iron crystallized from a metallic iron liquid, which originated as disseminated globules during reduction of the basaltic magma upon interaction with coal-bearing sedimentary rocks in the Siberian craton. The silicate melts entrapped and armored by the native iron are composed of two types of globules that represent the aluminosilicate (60-77 wt% SiO2) and silica-poor, Fe-Ti-Ca-P-rich (in wt%: SiO2, 15-46; FeO, 15-22; TiO2, 2-7; CaO, 11-27; P2O5, 5-30) conjugate liquids. Different proportions and the correlated compositions of these globules in individual melt pools suggest a continuously evolving environment of magmatic immiscibility during magma cooling. These natural immiscible melts correspond extremely well to the conjugate liquids experimentally produced in common basaltic compositions at <1025 °C. Our results show that immiscibility can occur at large scale in magma chambers and can be instrumental in generating felsic magmas and Fe-Ti-Ca-P-rich melts in the continental igneous provinces. © 2013 Geological Society of America. [less ▲]

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See detailMagma flow and feeder chamber location inferred from magnetic fabrics in jotunitic dykes (Rogaland anorthosite province, SW Norway)
Bolle, Olivier ULg; Besse, Michal; Diot, Hervé

in Tectonophysics (2010), 493(1-2), 42-57

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See detailLe magma parental du lopolithe de Bjerkreim-Sokndal (Norvège méridionale)
Duchesne, Jean-Clair ULg; Hertogen, Jan

in Comptes Rendus de l'Académie des Sciences. Série II, Mécanique, Physique, Chimie, Sciences de l'Univers, Sciences de la Terre (1988), 306(série II), 45-48

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See detailMagmatic intrusion and mineralization along a strike-slip fault into the Åna-Sira anorthosite: the Tellnes case, Rogaland, Norway
Diot, Hervé; Lambert, Jean-Marc; Bolle, Olivier ULg et al

in Documents du BRGM (1999), 290

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See detailMagnesium and glucose homeostasis.
Paolisso, G.; Scheen, André ULg; D'Onofrio, F. et al

in Diabetologia (1990), 33(9), 511-4

Magnesium is an important ion in all living cells being a cofactor of many enzymes, especially those utilising high energy phosphate bounds. The relationship between insulin and magnesium has been ... [more ▼]

Magnesium is an important ion in all living cells being a cofactor of many enzymes, especially those utilising high energy phosphate bounds. The relationship between insulin and magnesium has been recently studied. In particular it has been shown that magnesium plays the role of a second messenger for insulin action; on the other hand, insulin itself has been demonstrated to be an important regulatory factor of intracellular magnesium accumulation. Conditions associated with insulin resistance, such as hypertension or aging, are also associated with low intracellular magnesium contents. In diabetes mellitus, it is suggested that low intracellular magnesium levels result from both increased urinary losses and insulin resistance. The extent to which such a low intracellular magnesium content contributes to the development of macro- and microangiopathy remains to be established. A reduced intracellular magnesium content might contribute to the impaired insulin response and action which occurs in Type 2 (non-insulin-dependent) diabetes mellitus. Chronic magnesium supplementation can contribute to an improvement in both islet Beta-cell response and insulin action in non-insulin-dependent diabetic subjects. [less ▲]

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See detailMagnesium et metabolisme glucidique.
Lefebvre, Pierre ULg; Paolisso, G.; Scheen, André ULg

in Thérapie (1994), 49(1), 1-7

The interrelationships between magnesium and carbohydrate metabolism have regained considerable interest over the last few years. Insulin secretion requires magnesium: magnesium deficiency results in ... [more ▼]

The interrelationships between magnesium and carbohydrate metabolism have regained considerable interest over the last few years. Insulin secretion requires magnesium: magnesium deficiency results in impaired insulin secretion while magnesium replacement restores insulin secretion. Furthermore, experimental magnesium deficiency reduces the tissues sensitivity to insulin. Subclinical magnesium deficiency is common in diabetes. It results from both insufficient magnesium intakes and increase magnesium losses, particularly in the urine. In type 2, or non-insulin-dependent, diabetes mellitus, magnesium deficiency seems to be associated with insulin resistance. Furthermore, it may participate in the pathogenesis of diabetes complications and may contribute to the increased risk of sudden death associated with diabetes. Some studies suggest that magnesium deficiency may play a role in spontaneous abortion of diabetic women, in fetal malformations and in the pathogenesis of neonatal hypocalcemia of the infants of diabetic mothers. Administration of magnesium salts to patients with type 2 diabetes tend to reduce insulin resistance. Long-term studies are needed before recommending systematic magnesium supplementation to type 2 diabetic patients with subclinical magnesium deficiency. [less ▲]

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See detailMagnésium et système cardio-vasculaire
Reginster, Jean-Yves ULg

in Semper (1985), 98

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See detailMagnetic alignment in 2212 Bi-based superconducting system .1. Magnetic orientation of Bi2Sr2Ca1-x(RE)(x)Cu2O8-y [(RE)=Gd, Dy, Ho, Er] powder dispersed in epoxy resin at room temperature
Stassen, S.; Cloots, Rudi ULg; Vanderbemden, Philippe ULg et al

in Journal of Materials Research (1996), 11(5), 1082-1085

The magnetic anisotropy of rare-earth substituted 2212 materials (Bi(2)Sr(2)Ca(0.8)RE(0.2)Cu(2)O(x) with RE = Gd, Dy, Ho, Er) is put into evidence. Superconducting powder dispersed in epoxy resin is ... [more ▼]

The magnetic anisotropy of rare-earth substituted 2212 materials (Bi(2)Sr(2)Ca(0.8)RE(0.2)Cu(2)O(x) with RE = Gd, Dy, Ho, Er) is put into evidence. Superconducting powder dispersed in epoxy resin is oriented under an external magnetic field (4 T) in a direction that depends on the nature of the rare-earth used in the substitution. Both directions of observation (parallel or perpendicular to the field) were investigated. Splitting of (00l) peaks is neatly observed and discussed. [less ▲]

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See detailA magnetic and conversion electron Mossbauer spectral study of amorphous Dy20Fe80-yCoy thin films
Fleury-Frenette, Karl ULg; Delwiche, Jacques ULg; Grandjean, Fernande ULg et al

in IEEE Transactions on Magnetics (2001), 37(4), 2311-2314

Amorphous thin films of Dy20Fe80-yCoy, with 0 < y < 20 and of ca. 40 nm thickness, have been prepared by sputtering on polyimide substrates. The 295 K conversion electron Mossbauer spectra (CEMS) of these ... [more ▼]

Amorphous thin films of Dy20Fe80-yCoy, with 0 < y < 20 and of ca. 40 nm thickness, have been prepared by sputtering on polyimide substrates. The 295 K conversion electron Mossbauer spectra (CEMS) of these films consist of broadened sextets which have been analyzed with a distribution of hyperfine fields in which the iron moments are oriented perpendicular to the plane of the film, an orientation which is in agreement with the perpendicular magnetic anisotropy observed herein at 295 K by vibrating sample magnetrometry. The average hyperfine field and isomer shift increase linearly with increasing Co content. Both increases arise from an increase in the electron occupation of the 3d states as the cobalt content increases. [less ▲]

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See detailMagnetic and electronic ground states of B-site-substituted LaMnO3: from antiferromagnetism to ferromagnetism
Vertruyen, Bénédicte ULg; Flahaut, Delphine; Hebert, Sylvie et al

in Journal of Magnetism & Magnetic Materials (2004), 280(1), 75-83

We report about the physical properties of samples obtained by different substitutions on the Mn site of LaMnO3: LaMn0.85Ni0.15O3, LaMn0.85Ga0.15O3 and LaMn0.5Ga0.5O3. It is well known that the ... [more ▼]

We report about the physical properties of samples obtained by different substitutions on the Mn site of LaMnO3: LaMn0.85Ni0.15O3, LaMn0.85Ga0.15O3 and LaMn0.5Ga0.5O3. It is well known that the antiferromagnetic orbitally ordered ground state of LaMnO3 is easily destroyed to give way to ferromagnetism. However, this ferromagnetic behaviour can result from several mechanisms: depending on the nature of the substituting cation and on the substitution level, the physical properties derived from a complex interplay between exchange interactions, orbital ordering and Jahn-Teller distortion. As a result, there are noticeable differences between the physical properties of the different samples, even though all three samples display a ferromagnetic component in zero applied magnetic field. In this paper we compare the crystallographic, electrical and magnetic properties of these samples, with a special attention for the AC susceptibility behaviour. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailMagnetic and electronic properties of Eu4Sr4Ga16Ge30
Woods, G. T.; Marti; Beekman, M. et al

in Physical Review b (2006), 73(17),

Magnetization, static and ac magnetic susceptibility, nuclear forward scattering, and electrical resistivity measurements have been performed on polycrystalline Eu4Sr4Ga16Ge30, a type I clathrate that has ... [more ▼]

Magnetization, static and ac magnetic susceptibility, nuclear forward scattering, and electrical resistivity measurements have been performed on polycrystalline Eu4Sr4Ga16Ge30, a type I clathrate that has divalent strontium and europium ions encapsulated within a Ga-Ge framework. These data are compared with those of type I clathrates Eu8Ga16Ge30 and Eu6Sr2Ga16Ge30. The ferromagnetic ordering of these Eu-containing clathrates is substantially altered by the incorporation of strontium, as compared to Eu8Ga16Ge30. Ferromagnetism, accompanied by a relatively large negative magnetoresistance, is observed below 15 and 20 K in Eu4Sr4Ga16Ge30 and Eu6Sr2Ga16Ge30, respectively. An effective magnetic moment of 7.83 mu(B) per Eu ion is observed above 30 K for Eu4Sr4Ga16Ge30, a moment which is close to the free-ion moment of 7.94 mu(B) per europium(II) ion. [less ▲]

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See detailMagnetic and mossbauer spectral study of ErFe11Ti and ErFe11TiH
Piquer, C.; Hermann, Raphaël ULg; Grandjean, Fernande ULg et al

in Journal of Applied Physics (2003), 93(6), 3414-3421

X-ray diffraction, isothermal magnetization at 5 and 300 K, ac magnetic susceptibility measurements between 5 and 200 K, and iron-57 Mossbauer spectral measurements between 4.2 and 295 K have been carried ... [more ▼]

X-ray diffraction, isothermal magnetization at 5 and 300 K, ac magnetic susceptibility measurements between 5 and 200 K, and iron-57 Mossbauer spectral measurements between 4.2 and 295 K have been carried out on ErFe11Ti and ErFe11TiH. Hydrogen uptake has been measured by gravimetric analysis and the insertion of hydrogen into ErFe11Ti increases its magnetization, magnetic hyperfine fields, and isomer shifts as a result of the associated lattice expansion. Peaks and steplike changes in both the real and imaginary components of the ac magnetic susceptibility are observed at similar to50 and 40 K for ErFe11Ti and ErFe11TiH, respectively, and are assigned to spin-reorientation transitions resulting from the temperature dependence of the sixth-order Stevens crystal-field term of erbium. The Mossbauer spectra have been analyzed with a model which considers both these spin reorientations and the distribution of titanium atoms in the near-neighbor environment of the three crystallographically distinct iron sites. The assignment and the temperature dependencies of the hyperfine fields and isomer shifts are in complete agreement with the Wigner-Seitz cell analysis of the three iron sites in ErFe11Ti and ErFe11TiH. The changes in the hyperfine field and isomer shift with the number of titanium near neighbors of the three iron sites are in agreement with the values observed for related titanium-iron intermetallic compounds. (C) 2003 American Institute of Physics. [less ▲]

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See detailA Magnetic and Mössbauer Spectral Study of Several Na-Mn-Fe-bearing Alluaudites
Long, Gary J.; Hautot, Dimitri; Hatert, Frédéric ULg et al

Poster (2001)

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See detailA magnetic and Mossbauer spectral study of TbFe11Ti and TbFe11TiH
Piquer, C.; Hermann, Raphaël ULg; Grandjean, François-Xavier ULg et al

in Journal of Physics. Condensed Matter : An Institute of Physics Journal (2003), 15(43), 7395-7409

Magnetic and iron-57 Mossbauer spectral measurements between 4.2 and 640 K have been carried out on TbFe11Ti and TbFe11TiH. The insertion of hydrogen into TbFe11Ti form TbFe11TiH increases its ordering ... [more ▼]

Magnetic and iron-57 Mossbauer spectral measurements between 4.2 and 640 K have been carried out on TbFe11Ti and TbFe11TiH. The insertion of hydrogen into TbFe11Ti form TbFe11TiH increases its ordering temperature, magnetization, magnetic hyperfine fields, and isomer shifts as a result of lattice expansion. Further, the insertion of hydrogen reinforces the basal magnetic anisotropy of the terbium sublattice and, as is shown by ac susceptibility measurements and thermomagnetic analysis, the spin reorientation observed in TbFe11Ti at 338 K disappears in TbFe11TiH. The Mossbauer spectra have been analysed with a model that considers both the easy magnetization direction and the distribution of titanium atoms in the near-neighbour environment of the three crystallographically distinct iron sites. The assignment and the temperature dependencies of the hyperfine fields and isomer shifts are in complete agreement with a Wigner-Seitz cell analysis of the three iron sites in RFe11Ti and RFe11TiH, where R is a rare-earth element. A complete analysis of the quadrupole interactions in both magnetic phases and in the paramagnetic phase of TbFe11Ti supports the Mossbauer spectral analysis, and indicates that in the basal magnetic phase the iron magnetic moments are oriented along the equivalent [100] and [010] directions of the unit cell. [less ▲]

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See detailMagnetic and transport measurements on melt-textured DyBCO single domains
Vanderbemden, Philippe ULg; Misson, Vincent; Ausloos, Marcel ULg et al

in Physica C: Superconductivity (2002), 372(Part 2), 1225-1228

In this communication we report critical current measurements of melt processed DyBa2Cu3O7-x samples determined by several measuring techniques. First the material was characterized by AC susceptibility ... [more ▼]

In this communication we report critical current measurements of melt processed DyBa2Cu3O7-x samples determined by several measuring techniques. First the material was characterized by AC susceptibility and DC magnetization. The results are characteristic of good quality melt-processed (RE)BCO material with T-c = 89 K and Jc(77 K, 1 T) = 10^4 A/cm^2. Next, pulsed currents were used in order to determine both I-V curves and transport critical currents. The origin of the discrepancy between transport and magnetic data has been discussed. The results point out significant local variations of the critical current density throughout the single domain. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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