8 results on '"Échange chimique"'
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2. Microstructure and compositional changes across biotite-rich reaction selvedges around mafic schollen in a semipelitic diatexite migmatite
- Author
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Lin, Lina, Sawyer, Edward W., Lin, Lina, and Sawyer, Edward W.
- Abstract
Biotite‐rich selvedges developed between mafic schollen and semipelitic diatexite in migmatites at Lac Kénogami in the Grenville Province of Quebec. Mineral equilibria modelling indicates that partial melting occurred in the mid‐crust (4.8–5.8 kbar) in the range 820–850°C. The field relations, petrography, mineral chemistry and whole‐rock composition of selvedges along with their adjacent mafic schollen and host migmatites are documented for the first time. The selvedges measured in the field are relatively uniform in width (~1 cm wide) irrespective of the shape or size of their mafic scholle. In thin section, the petrographic boundary between mafic scholle and selvedge is defined by the appearance of biotite and the boundary between selvedge and diatexite by the change in microstructure for biotite, garnet, plagioclase and quartz. Three subtypes of selvedges are identified according to mineral assemblage and microstructure. Subtype I have orthopyroxene but of different microstructure and Mg# to orthopyroxene in the mafic scholle; subtype II contain garnet with many mineral inclusions, especially of ilmenite, in contrast to garnet in the diatexite host which has few inclusions; subtype III lack orthopyroxene or garnet, but has abundant apatite. Profiles showing the change in plagioclase composition from the mafic schollen across the selvedge and into the diatexite show that each subtype of selvedge has a characteristic pattern. Four types of biotite are identified in the selvedges and host diatexite based on their microstructural characteristics. (a) Residual biotite forms small rounded red‐brown grains, mostly as inclusions in peritectic cordierite and garnet in diatexite; (b) selvedge biotite forms tabular subhedral grains with high respect ratio; (c) diatexite biotite forms tabular subhedral grains common in the matrix of the diatexite; and (d) retrograde biotite that partially replaces peritectic cordierite and garnet in the diatexite. The four groups of biotite
- Published
- 2019
3. Bimodal distribution of the solid products in a magmatic chamber: Modelling by fractional crystallization and coupling of the chemical exchanges with the differential melt/solid transport
- Author
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Lakhssassi, Morad, Guy, Bernard, Touboul, Eric, and Cottin, Jean-Yves
- Subjects
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DISTRIBUTION (Probability theory) , *IGNEOUS rocks , *MAGMAS , *CRYSTALLIZATION , *SOLIDIFICATION , *SEDIMENTATION & deposition - Abstract
Abstract: Our aim is to explain the possible bimodality of the compositions of the magmatic rocks of the same province. In order to do so, we present a model for the crystallization of a magmatic chamber, coupling the three phenomena: solidification, sedimentation, chemical reactions between the solid and the liquid. These three phenomena make two independent dimensionless parameters appear: the ratios of the solidification rate to the transport velocity, and of the chemical kinetics to the transport velocity. The model is written for one independent chemical component. It is shown that, for certain values of the dimensionless parameters, the chemical composition of the chamber can present a bimodal distribution, starting from uniform initial conditions. This model shows that the coupling between three elementary phenomena is enough to explain the bimodality, or more generally the appearance of discontinuities of chemical compositions, without making any additional assumption. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
4. Optimizing HSQC experiment for the observation of exchange broadened signals in RNA–protein complexes
- Author
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Barraud, Pierre, Dardel, Frédéric, and Tisné, Carine
- Subjects
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RNA , *PROTEINS , *NUCLEAR magnetic resonance , *SPECTRUM analysis , *MAGNETIC resonance - Abstract
Abstract: Sites for interaction in protein–RNA complexes are often regions of conformational exchange. Although the study of exchange processes could bring valuable information about the recognition mode between protein and RNA, chemical exchange can be detrimental to the NMR spectra quality, resulting in broad, very weak or even unobservable signals. In the present report, we used CPMG-like experiments to improve HSQC spectra of an RNA–protein complex in fast exchange on the chemical shift time scale. The use of such improvement will allow us to handle the resolution of the three-dimensional structure of the complex by NMR. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
5. Carbohydrate-antibody interactions by NMR for a [sup 13] C-labelled disaccharide ligand.
- Author
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Uhrín, Dušan, Prasad, A.V Krishna, Brisson, Jean-Robert, and Bundle, David R
- Subjects
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CARBOHYDRATES , *NUCLEAR magnetic resonance spectroscopy , *MONOCLONAL antibodies , *CARBON , *PROTEINS - Abstract
Incorporation of a [sup 13] C label into a carbohydrate ligand, methyl 3-O-(3,6-dideoxy-α-D-xylohexopyranosyl)-2-O-methyl-α-D-mannopyranoside permitted by NMR spectroscopy the study of its binding to the Fab from a monoclonal antibody, Se 155-4. The signals of the free and bound form were observed in the [sup 13] C spectrum of the carbohydrate-protein complex. The dissociation rate constants were consequently determined by full lineshape analysis of the [sup 13] C spectrum. Comparison with simplified analyses relying only on the linewidth of the [sup 1] H and [sup 13] C signals of the free ligand were made and the justifications of underlying assumptions used in these analyses were discussed. For [sup 1] H NMR, the protein resonances were purged with a [sup 13] C filter to observe only the ligand resonances and NOEs between the ligand and the protein.Key words: carbohydrate, binding, NMR, C-13 label, chemical exchange.L'incorporation d'un marqueur [sup 13] C dans un hydrate de carbone servant de ligand, le 3-O-(3,6-didésoxy-α-D-xylohexopyranosyl)-2-O-méthyl-α-D-mannopyranoside de méthyle a permis d'utiliser la spectroscopie RMN pour étudier sa fixation sur le Fab d'un anticorps monoclonal, Se 155-4. Les signaux des formes libres et liées (conjuguées) ont été observés dans le spectre [sup 13] C du complexe glucide-protéine. En se basant sur une analyse complète de la forme des bandes du spectre du [sup 13] C, on a par la suite déterminé les constantes de vitesse de la dissociation. On a fait une comparaison avec les analyses n'utilisant que la largeur des bandes des signaux du [sup 1] H et du [sup 13] C et on discute des hypothèses sous-jacentes utilisées dans ces analyses. Pour la RMN du [sup 1] H, les résonances de la protéine ont été purgées à l'aide d'un filtre de [sup 13] C afin de n'observer que les résonances du ligand et les eOn entre le ligand et la protéine.Mots clés : hydrate de carbone, fixation, RMN, marqueur au C-13, échange chimique.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]
- Published
- 2002
6. Bimodal distribution of the solid products in a magmatic chamber: Modelling by fractional crystallization and coupling of the chemical exchanges with the differential melt/solid transport
- Author
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Morad Lakhssassi, Jean-Yves Cottin, Eric Touboul, Bernard Guy, Département Géochimie, environnement, écoulement, réacteurs industriels et cristallisation (GENERIC-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-SPIN, Centre Sciences des Processus Industriels et Naturels (SPIN-ENSMSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Laboratoire Magmas et Volcans (LMV-ENSMSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-SPIN-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Magmas et Volcans (LMV), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement et la société-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Université Jean Monnet [Saint-Étienne] (UJM), Centre de Génie Industriel et Informatique (G2I-ENSMSE), Département Méthodes et Modèles Mathématiques pour l'Industrie (3MI-ENSMSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Centre G2I, Laboratoire de Transferts Lithosphériques (LTL), Université Jean Monnet [Saint-Étienne] (UJM), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Jean Monnet Saint-Étienne, Ecole Nationale Supérieure des Mines de Saint Etienne Centre G2I, Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), Université Jean Monnet - Saint-Étienne (UJM), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Échange chimique ,010504 meteorology & atmospheric sciences ,[SDE.MCG]Environmental Sciences/Global Changes ,[SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography ,Thermodynamics ,Mineralogy ,Chemical exchange ,Répartition bimodale ,010502 geochemistry & geophysics ,01 natural sciences ,law.invention ,Discontinuity of composition ,Solidification ,Bimodal distribution ,[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry ,law ,Fractional crystallization ,Sédimentation ,[SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering ,Crystallization ,0105 earth and related environmental sciences ,Physics ,Cristallisation fractionnée ,Global and Planetary Change ,Fractional crystallization (geology) ,Discontinuité de composition ,Magmatic chamber ,General Earth and Planetary Sciences ,Chambre magmatique - Abstract
International audience; Our aim is to explain the possible bimodality of the compositions of the magmatic rocks of the same province. In order to do so, we present a model for the crystallization of a magmatic chamber, coupling the three phenomena: solidification, sedimentation, chemical reactions between the solid and the liquid. These three phenomena make two independent dimensionless parameters appear: the ratios of the solidification rate to the transport velocity, and of the chemical kinetics to the transport velocity. The model is written for one independent chemical component. It is shown that, for certain values of the dimensionless parameters, the chemical composition of the chamber can present a bimodal distribution, starting from uniform initial conditions. This model shows that the coupling between three elementary phenomena is enough to explain the bimodality, or more generally the appearance of discontinuities of chemical compositions, without making any additional assumption. ==================================================== Nous cherchons à rendre compte de la bimodalité possible des compositions des roches magmatiques d'une même province. Pour cela, nous présentons un modèle de cristallisation d'une chambre magmatique couplant les trois phénomènes : solidification, sédimentation, réactions chimiques entre le solide et le liquide. Ceux-ci font apparaître deux paramètres sans dimension indépendants, exprimant les rapports respectifs de la vitesse de solidification sur la vitesse du déplacement solide/liquide, et de la cinétique d'échange sur la vitesse de déplacement. Le modèle est écrit pour un constituant chimique indépendant. On montre que, pour certaines valeurs des paramètres sans dimension, la composition chimique de la chambre peut présenter une répartition bimodale, alors que les conditions initiales sont uniformes. Ce modèle montre que le couplage entre trois phénomènes élémentaires suffit à rendre compte de la bimodalité, ou plus généralement, de l'apparition de discontinuités de compositions, sans faire intervenir d'hypothèse additionnelle.
- Published
- 2010
7. L'estuaire de la Casamance : environnement, pêche, socio-économie
- Author
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Le Brusq, Jean-Yves, Le Reste, Louis (ed.), Fontana, André (ed.), and Samba, A. (ed.)
- Subjects
EAU DE SURFACE ,SALINITE ,SOL ,ECHANGE CHIMIQUE ,ESTUAIRE - Abstract
La sécheresse a entraîné une sursalure des sols exondables, les rendant dans la plupart des cas inutilisables pour la culture. L'abaissement de la nappe phréatique a par ailleurs favorisé l'oxydation des sols potentiellement sulfatés-acides ce qui a entraîné une diminution du PH. Dans certains cas il y a même libération de sels d'aluminiums solubles et toxiques. Le problème prioritaire est l'élimination du sel par la construction de petits barrages anti-sel. (Résumé d'auteur)
- Published
- 1986
8. Applications of Long-Lived Spin States to High Resolution NMR Studies of Biomolecules
- Author
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Ahuja, Puneet, Bodenhausen, Geoffrey, and Vasos, Paul Romeo
- Subjects
Quantitative Biology::Biomolecules ,Cohérences aux temps de vie longs ,Hyperpolarization ,Chemical Exchange ,Dynamiques lentes ,Etats aux temps de vie longs ,Hyperpolarisation ,Long-Lived Coherences ,Slow Dynamics ,Long-Lived States ,Echange chimique - Abstract
Slow dynamic processes, such as biomolecular folding/unfolding, macromolecular diffusion, etc., can be conveniently monitored by solution-state two-dimensional (2D) NMR spectroscopy, provided the inverse of their rate constants does not exceed the nuclear spin-lattice relaxation time constants (T1). The discovery of long-lived states (LLS) by Malcolm Levitt's group opened a new dimension for the study of slow dynamic phenomena, as magnetization stored in the form of LLS decays with the time constants TLLS, where in many cases TLLS >> T1. In this thesis, various excitation methods and applications of LLS are discussed. Broadband excitation of LLS is suitable to monitor slow processes and has been applied to study the slow ring-flip in tyrosine residues of BPTI (Bovine Pancreatic Trypsin Inhibitor), as well as to perform simultaneous measurements of diffusion coefficients in mixtures of molecules with arbitrary J-couplings and chemical shifts. The applications of LLS, initially believed to be limited to isolated spin-½ pairs, were extended to larger spin systems, including some common amino acids like Serine, Aspartic Acid, etc. LLS have been observed in Glycine residues of small peptides like Ala-Gly, as well as in mobile parts of proteins, e.g., in Gly 75 and 76 of Ubiquitin. The lifetimes TLLS are more sensitive to dipolar interactions with external spins than longitudinal and transverse relaxation time constants, T1 or T2, and therefore can provide structural information for unfolded proteins. The unfolding of Ubiquitin by addition of Urea and by varying pH was followed using LLS. The excitation of coherent superpositions across singlet and triplet states, which we call long-lived coherences (LLC's), leads to resolution enhancement in conventional NMR spectroscopy. New methods have been designed to store hyperpolarized (13C or 1H) magnetization in the form of LLS and have been demonstrated using samples of Ala-Gly and Acrylic Acid.
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