Letteratura scientifica selezionata sul tema "Calcium cations divalents"
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Articoli di riviste sul tema "Calcium cations divalents"
1
Hess, P., J. B. Lansman e R. W. Tsien. "Calcium channel selectivity for divalent and monovalent cations. Voltage and concentration dependence of single channel current in ventricular heart cells." Journal of General Physiology 88, n. 3 (1 settembre 1986): 293–319. http://dx.doi.org/10.1085/jgp.88.3.293.
Testo completoAbstract (sommario):
Single channel and whole cell recordings were used to study ion permeation through Ca channels in isolated ventricular heart cells of guinea pigs. We evaluated the permeability to various divalent and monovalent cations in two ways, by measuring either unitary current amplitude or reversal potential (Erev). According to whole cell measurements of Erev, the relative permeability sequence is Ca2+ greater than Sr2+ greater than Ba2+ for divalent ions; Mg2+ is not measurably permeant. Monovalent ions follow the sequence Li+ greater than Na+ greater than K+ greater than Cs+, and are much less permeant than the divalents. These whole cell measurements were supported by single channel recordings, which showed clear outward currents through single Ca channels at strong depolarizations, similar values of Erev, and similar inflections in the current-voltage relation near Erev. Information from Erev measurements stands in contrast to estimates of open channel flux or single channel conductance, which give the sequence Na+ (85 pS) greater than Li+ (45 pS) greater than Ba2+ (20 pS) greater than Ca2+ (9 pS) near 0 mV with 110-150 mM charge carrier. Thus, ions with a higher permeability, judged by Erev, have lower ion transfer rates. In another comparison, whole cell Na currents through Ca channels are halved by less than 2 microM [Ca]o, but greater than 10 mM [Ca]o is required to produce half-maximal unitary Ca current. All of these observations seem consistent with a recent hypothesis for the mechanism of Ca channel permeation, which proposes that: ions pass through the pore in single file, interacting with multiple binding sites along the way; selectivity is largely determined by ion affinity to the binding sites rather than by exclusion by a selectivity filter; occupancy by only one Ca ion is sufficient to block the pore's high conductance for monovalent ions like Na+; rapid permeation by Ca ions depends upon double occupancy, which only becomes significant at millimolar [Ca]o, because of electrostatic repulsion or some other interaction between ions; and once double occupancy occurs, the ion-ion interaction helps promote a quick exit of Ca ions from the pore into the cell.
2
Kamgaing, Théophile. "Précipitation de carbonates de cations divalents dans les systèmes lacustres : intérêt, état des connaissances des mécanismes et suggestions (Revue critique de la littérature)". Revue des sciences de l’eau 28, n. 2 (7 luglio 2015): 81–102. http://dx.doi.org/10.7202/1032292ar.
Testo completoAbstract (sommario):
Les carbonates de fer, de manganèse, de calcium et de magnésium précipités en solution des lacs sont documentés. Indicateurs de climat et de variation des caractéristiques chimiques des lacs, ils sont de plus en plus recherchés dans les sédiments. Souvent incomplets, les mécanismes de leur précipitation dans la colonne d’eau du lac et dans les eaux interstitielles sont reprécisés dans cette étude. D’après la littérature, la sidérite et la rhodochrosite précipitent en milieu réducteur saturé de carbonate de fer et de carbonate de manganèse respectivement. Ces prévisions sont confirmées dans cette étude, le potentiel redox étant un paramètre déterminant pour la précipitation du carbonate de fer. Toutefois, la littérature ne décrit pas suffisamment l’origine (géochimique ou biologique) des éléments constitutifs des solides carbonatés lacustres, encore moins les phénomènes qui stabilisent ces derniers ou les rendent vulnérables (dissolution). Cette étude apporte plus de précisions à l’endogènèse de ces carbonates, l’origine de leurs éléments constitutifs étant prise en compte. Elle montre que le caractère de l’eau (agressif ou incrustant) pourrait avoir un impact considérable sur le devenir de ces carbonates. Ainsi un dégazage forcé d’un lac rendrait ses eaux incrustantes, caractère idéal pour la précipitation des carbonates, mais néfaste à la stabilité des strates qui changent de composition après précipitation d’espèces chimiques. Par conséquent, tout projet de dégazage de lac devrait prendre en considération ce paramètre (caractère de l’eau) dans sa conception, sa mise en oeuvre et son exploitation.
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Momoshima, N., e E. A. Bondietti. "Cation binding in wood: applications to understanding historical changes in divalent cation availability to red spruce". Canadian Journal of Forest Research 20, n. 12 (1 dicembre 1990): 1840–49. http://dx.doi.org/10.1139/x90-247.
Testo completoAbstract (sommario):
The ion exchange characteristics of red spruce (Picearubens Sarg.) bolewood were investigated to understand factors that control divalent cation and H+ concentrations in tracheid cell walls. Vertical concentration measurements of selected cations along the stem demonstrated that the alkaline earths showed the expected chromatographic fractionation, while other cations showed variable patterns relative to calcium. The concentration of cation binding sites (pectates) decreased in a predictable manner from the pith towards the cambium as a function of radius, not chronological age, explaining why in red spruce calcium concentrations are usually highest in the oldest wood. Red spruce wood from Maine and Tennessee had divalent base saturations of about 60 to 65% before the mid-1900s; however, divalent base saturations increased to about 75 to 80% in the mid-1900s, after which they decreased. Wood pH values were highest when divalent base saturation was highest. Calcium and potassium equilibration experiments were conducted, and the results were used to parameterize the Donnan model of cation exchange to understand why base saturation in woody tissues changes in different time periods. Increased divalent cation concentrations in red spruce wood formed during the 1940s to the 1970s are explainable by small increases in both sap pH and divalent cation concentrations and may be the signal of cation mobilization following increasing mineral acid anion deposition from the atmosphere.
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Yoder, C. H., N. T. Landes, L. K. Tran, A. K. Smith e J. D. Pasteris. "The relative stabilities of A- and B-type carbonate substitution in apatites synthesized in aqueous solution". Mineralogical Magazine 80, n. 6 (ottobre 2016): 977–83. http://dx.doi.org/10.1180/minmag.2016.080.035.
Testo completoAbstract (sommario):
AbstractCarbonated calcium apatites doped with a monovalent cation (Li+, Na+, or K+) or a divalent cation (Mg2+ or Zn2+) were prepared in aqueous solution and analysed by powder X-ray diffraction, inductively coupled plasma atomic emission spectroscopy and infrared spectroscopy. The hypothesis that the location of carbonate in the apatite structure, either in place of hydroxide ions in the c-axis channels (A-type substitution) or in place of phosphate (B-type substitution), is affected by the solution energetics of the cation (specifically its enthalpy of hydration) was strengthened by the observation of larger amounts of Atype carbonate in apatites containing the monovalent cations in aqueous solution. It is shown that cations with low negative enthalpies of hydration favour A-type substitution, whereas cations with higher negative hydration enthalpies, such as divalent cations (Mg2+, Zn2+), favour B-type substitution.
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D’Elia, John A., e Larry A. Weinrauch. "Role of Divalent Cations in Infections in Host–Pathogen Interaction". International Journal of Molecular Sciences 25, n. 18 (10 settembre 2024): 9775. http://dx.doi.org/10.3390/ijms25189775.
Testo completoAbstract (sommario):
With increasing numbers of patients worldwide diagnosed with diabetes mellitus, renal disease, and iatrogenic immune deficiencies, an increased understanding of the role of electrolyte interactions in mitigating pathogen virulence is necessary. The levels of divalent cations affect host susceptibility and pathogen survival in persons with relative immune insufficiency. For instance, when host cellular levels of calcium are high compared to magnesium, this relationship contributes to insulin resistance and triples the risk of clinical tuberculosis. The movement of divalent cations within intracellular spaces contributes to the host defense, causing apoptosis or autophagy of the pathogen. The control of divalent cation flow is dependent in part upon the mammalian natural resistance-associated macrophage protein (NRAMP) in the host. Survival of pathogens such as M tuberculosis within the bronchoalveolar macrophage is also dependent upon NRAMP. Pathogens evolve mutations to control the movement of calcium through external and internal channels. The host NRAMP as a metal transporter competes for divalent cations with the pathogen NRAMP in M tuberculosis (whether in latent, dormant, or active phase). This review paper summarizes mechanisms of pathogen offense and patient defense using inflow and efflux through divalent cation channels under the influence of parathyroid hormone vitamin D and calcitonin.
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Silverman, Harold, James W. McNeil e Thomas H. Dietz. "Interaction of trace metals Zn, Cd, and Mn, with Ca concretions in the gills of freshwater unionid mussels". Canadian Journal of Zoology 65, n. 4 (1 aprile 1987): 828–32. http://dx.doi.org/10.1139/z87-131.
Testo completoAbstract (sommario):
The interaction of Zn, Mn, and Cd with Ca concretions in the gills of unionid mussels was investigated. Raising blood levels of these ions to twice their normal values for a week does not result in significant deposition of these metals into gill concretions. The interaction of Zn with the concretions was examined in more detail both in vivo and in vitro. Isolated concretions bind Zn as rapidly as Ca. However short-term in vivo labelling studies using radiolabeled Zn and Ca verify that Zn is not added to concretions while Ca is being rapidly accumulated. These studies demonstrate that calcium concretions from the gills of unionid mussels do not indiscriminately bind divalent cations, but precisely regulate the species of divalent cation incorporated. This is further evidenced by the lack of relationship between blood or pond water cation levels and the levels of specific cations found in the concretions. Since the concretions are mobilized during the reproductive period, and serve as a source of glochidial calcium, it would be disadvantageous for these concretions to bind divalent cations for detoxification purposes.
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Bondietti, E. A., N. Momoshima, W. C. Shortle e K. T. Smith. "A historical perspective on divalent cation trends in red spruce stemwood and the hypothetical relationship to acidic deposition". Canadian Journal of Forest Research 20, n. 12 (1 dicembre 1990): 1850–58. http://dx.doi.org/10.1139/x90-248.
Testo completoAbstract (sommario):
Anomalies in the radial concentration trends of Ca2+, Mg2+, and other divalent cations in the stemwood of red spruce (Picearubens Sarg.) occurred in trees grown in New England, Tennessee, and North Carolina. These anomalies may be assumed to result from changes in sap chemistry. These inferred changes in sap chemistry were the expected result of changes of divalent cation availability in forest soils. The patterns of these anomalies may be interpreted as a signal of a regional mobilization of cations in the rooting zone of red spruce. The anomalous increase in divalent cations present in wood formed in the mid-1900s is coincident both with rapid increases in SOx and NOx deposition in eastern North America and with increases in radial growth increment. The anomalous decrease in divalent cations in wood formed in the late-1900s is coincident with declines in radial increment. Comparisons with divalent cation trends in eastern hemlock (Tsugacanadensis (L.) Carr.), Fraser fir (Abiesfraseri (Pursh) Poir.), and yellow birch (Betulaalleghaniensis Britt. = B. lutea Michx.) suggested that these anomalies were not restricted to red spruce. Radial concentration trends of 90Sr introduced to the environment through radioactive fallout during the 1950s and 1960s were used to investigate the physiology of these divalent cation concentration anomalies. The distributions of 90Sr were also used to estimate the turnover rates for the nutritionally available pools of alkaline earths such as calcium.
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Rokitskaya, Tatyana I., Alexander M. Arutyunyan, Ljudmila S. Khailova, Alisa D. Kataeva, Alexander M. Firsov, Elena A. Kotova e Yuri N. Antonenko. "Usnic Acid-Mediated Exchange of Protons for Divalent Metal Cations across Lipid Membranes: Relevance to Mitochondrial Uncoupling". International Journal of Molecular Sciences 23, n. 24 (19 dicembre 2022): 16203. http://dx.doi.org/10.3390/ijms232416203.
Testo completoAbstract (sommario):
Usnic acid (UA), a unique lichen metabolite, is a protonophoric uncoupler of oxidative phosphorylation, widely known as a weight-loss dietary supplement. In contrast to conventional proton-shuttling mitochondrial uncouplers, UA was found to carry protons across lipid membranes via the induction of an electrogenic proton exchange for calcium or magnesium cations. Here, we evaluated the ability of various divalent metal cations to stimulate a proton transport through both planar and vesicular bilayer lipid membranes by measuring the transmembrane electrical current and fluorescence-detected pH gradient dissipation in pyranine-loaded liposomes, respectively. Thus, we obtained the following selectivity series of calcium, magnesium, zinc, manganese and copper cations: Zn2+ > Mn2+ > Mg2+ > Ca2+ >> Cu2+. Remarkably, Cu2+ appeared to suppress the UA-mediated proton transport in both lipid membrane systems. The data on the divalent metal cation/proton exchange were supported by circular dichroism spectroscopy of UA in the presence of the corresponding cations.
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Marshall, Wayne E., Lynda H. Wartelle e Danny E. Akin. "Flax shive as a source of activated carbon for metals remediation". BioResources 2, n. 1 (23 febbraio 2007): 82–90. http://dx.doi.org/10.15376/biores.2.1.82-90.
Testo completoAbstract (sommario):
Flax shive constitutes about 70% of the flax stem and has limited use. Because shive is a lignocellulosic by-product, it can potentially be pyrolyzed and activated to produce an activated carbon. The objective of this study was to create an activated carbon from flax shive by chemical activation in order to achieve significant binding of selected divalent cations (cadmium, calcium, copper, magnesium, nickel, zinc). Shive carbons activated by exposure to phosphoric acid and com-pressed air showed greater binding of cadmium, copper, nickel or zinc than a sulfuric acid-activated flax shive carbon reported in the literature and a commercial, wood-based carbon. Uptake of calcium from a drinking water sample by the shive carbon was similar to commercial drinking water filters that contained cation exchange resins. Magnesium removal by the shive carbon was greater than a commercial drinking water filtration carbon but less than for filters containing cation exchange resins. The results indicate that chemically activated flax shive carbon shows considerable promise as a component in industrial and residential water filtration systems for removal of divalent cations.
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Almatrafi, Roua, Saeed Banawas e Mahfuzur R. Sarker. "Divalent Cation Signaling in Clostridium perfringens Spore Germination". Microorganisms 11, n. 3 (26 febbraio 2023): 591. http://dx.doi.org/10.3390/microorganisms11030591.
Testo completoAbstract (sommario):
Spore germination plays an essential role in the pathogenesis of Clostridium perfringens-associated food poisoning. Germination is initiated when bacterial spores sense various stimuli, including chemicals and enzymes. A previous study showed that dipicolinic acid (DPA) chelated with calcium (Ca-DPA) significantly stimulated spore germination in C. perfringens. However, whether Ca2+ or DPA alone can induce germination is unknown. Therefore, we aimed to evaluate the possible roles of Ca2+ and other divalent cations present in the spore core, such as Mn2+ and Mg2+, in C. perfringens spore germination. Our study demonstrated that (i) Ca-DPA, but not DPA alone, induced C. perfringens spore germination, suggesting that Ca2+ might play a signaling role; (ii) all tested calcium salts induced spore germination, indicating that Ca2+ is critical for germination; (iii) the spore-specific divalent cations Mn2+ and Mg2+, but not Zn2+, induced spore germination, suggesting that spore core-specific divalent cations are involved in C. perfringens spore germination; and (iv) endogenous Ca2+ and Mg2+ are not required for induction of C. perfringens spore germination, whereas exogenous and partly endogenous Mn2+ are required. Collectively, our results suggest that exogenous spore core-specific divalent cation signals are more important than endogenous signals for the induction of spore germination.
Tesi sul tema "Calcium cations divalents"
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AbouKaïs-Nassrallah, Najat. "Influence du manganèse (II) et du cuivre (II) sur la transformation de la vatérite en calcite en solution aqueuse". Lille 1, 1997. http://www.theses.fr/1997LIL10165.
Testo completoAbstract (sommario):
Dans ce mémoire, nous nous sommes intéressés a la transformation cristalline de la vatérite en calcite cubique sous l'influence des cations métalliques divalents mn#2#+ et cu#2#+ dans l'eau ultra-pure. Pour cela, nous avons réalisé sur nos échantillons solides récupérés par filtration : I) des analyses macroscopiques en utilisant les techniques suivantes : spectroscopies atomique d'émission, vibrationnelles infrarouge et Raman, par diffraction des rayons x et de résonance paramagnétique électronique, mesures d'aire spécifique ; et II) des analyses microscopiques au moyen des methodes suivantes : microscopies optique et a balayage électronique, microspectrometrie raman. Nos études ont montre que les ions mn#2#+ et cu#2#+ substituent les ions ca#2#+ présents a la surface des micro-grains de vatérite et que la morphologie de ces micro-particules de vatérite et l'étendue de la transformation cristalline de ce carbonate de calcium métastable en calcite cubique dépendent de la nature même du cation incorpore et de la concentration de ce dernier dans le milieu. Ainsi, nous avons trouve qu'aux concentrations élevées d'ions métalliques (10#-#2m), l'interaction entre la vatérite et les ions me#2#+ conduit a : I) un mélange de rhodochrosite et calcite dans le cas du mn(II) ; et II) un mélange d'aragonite, calcite et malachite (cuco#3, cu(oh)#2) dans le cas du cu(II) ; et nous avons pu donner une représentation microscopique et/ou moléculaire de la surface de ces échantillons solides et discerner les différents phases carbonatées mises en jeu dans les systèmes : vatérite-métal(II)-h#2oCependant, pour une concentration d'ions métalliques égale a 10#-#3m nous avons constate un retard de cette transformation de quelques heures pour le mn(II) et de quelques jours pour le cu(II) en raison de la formation de complexes du type (h#2o)#yme#xca#1#-#xco#3 a la surface des micro-grains de vatérite. Nous avons utilise la technique d'analyse de surfaces solides spx : (spectroscopie de photoélectrons induits par rayons x) pour atteindre les coefficients stœchiométriques des différents éléments de surface : c, ca, me et o#carbonate, constituant ces complexes et avons détermine leur quantité d'eau (y) au moyen de la thermogravimétrie. Le calcul thermodynamique nous a permis d'expliquer le phénomène de relative stabilité de ces complexes
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Lacapère, Jean-Jacques. "Mecanisme reactionnel de l'atpase calcium du reticulum sarcoplasmique : interaction avec les nucleotides, role des cations divalents". Paris 6, 1987. http://www.theses.fr/1987PA066465.
Testo completoAbstract (sommario):
L'atpase calcique du reticulum sarcoplasmique hydrolyse une molecule d'atp pour transporter du calcium contre son gradient de concentration. Plusieurs hypotheses existantes pour expliquer ce phenomene: 1) deux sites topologiquement differents (un site catalytique de haute affinite et un site activateur de basse affinite) 2) un seul site ayant des affinites differentes pour les deux conformations principales de l'enzyme, la saturation sur site basse affinite entrainant une acceleration du changement de conformation 3) un seul site, la liaison d'atp sur le site catalytique phosphoryle de l'enzyme, apres depart de l'adp, induisant l'activation. Par une approche cinetique, la derniere hypothese est la plus solidement etayee. Les auteurs proposent un schema de fonctionnement de cette enzyme ou, a fortes concentrations de substrat, le site catalytique serait toujours occupe par l'atp. L'activation serait le fruit de modifications de differentes etapes du cycle
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Lacapere, Jean-Jacques. "Mécanisme réactionnel de l'ATPase calcium du reticulum sarcoplasmique interaction avec les nucléotides, rôle des cations divalents /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37606772m.
Testo completo
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Amat, Tiffany. "Interplay between pulse proteins, phytic acid and calcium : impact on their aggregation state and solubility". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCK048.
Testo completoAbstract (sommario):
Ce projet de thèse vise à approfondir les connaissances sur les interactions qui peuvent exister entre les protéines de féveroles et de pois, les ions calcium et l’acide phytique (AP). Différents niveaux de complexité ont été étudiés depuis les concentrés et isolats commerciaux jusqu’aux fractions protéiques extraites en laboratoire (globulines totales, vicilines 7S, légumines 11S et albumines 2S). Les impacts de la dénaturation protéique par chauffage ont aussi été analysés. Les résultats ont mis en évidence que les interactions moléculaires sont influencées par le pH et les concentrations molaires mais dépendent aussi du type d’ingrédients et/ou de la fraction de protéines étudiée. L’existence de complexes insolubles binaires (Ca-Protéines et/ou Ca-AP) et ternaires (Ca-AP-Protéines) pour des pHs ≤ 7.0 a été observée dans des dispersions de concentrés commerciaux. Autour du pH neutre, les protéines sont impliquées dans des complexes solubles avec l’AP et le Ca : (i) de types binaires majoritairement et (ii) ternaires plus rarement à pH 7.5. A contrario, les isolats commerciaux composés de protéines hautement dénaturées, présentaient une faible solubilité. Le pouvoir d’association au Ca dans les systèmes de protéines extraites en laboratoire dépendait principalement des taux d'AP co-extraits. Plus riches en AP, les dispersions de vicilines 7S présentaient de meilleures capacités à chélater le Ca par comparaison aux légumines 11S. L’agrégation thermique a induit une modification du type et de la taille des complexes formés. En conséquence, en fonction des concentrations en ions Ca ajoutées, des teneurs en AP et des conditions de pH, il semble possible de contrôler la stabilité colloïdale des systèmes de protéines de légumineuses. Ces travaux ont permis d’acquérir des connaissances intéressantes à propos des ingrédients optimaux et/ou des conditions de formulation préférentielles à utiliser pour maîtriser l’élaboration, le goût et la stabilité des aliments à base de légumineusesThis PhD project focused on improving knowledge about the interactions that may exist between faba bean and pea proteins, calcium ions and phytates (PA) in order to develop strategies aimed at improving properties of ingredients. PA is a polyphosphate compound, which can bind to interesting molecules such as proteins and Ca. Consequently, PA can play a major role in colloidal stability of protein systems while modulating the formation of complexes. Various levels of complexity were investigated from commercial concentrate and isolate ingredients to laboratory-scale protein fractions (total globulins, 7S vicilins, 11S legumins and 2S albumins). The impacts of thermal denaturation were also studied. The results evidenced that molecular interactions are influenced by the environmental medium including pH, and molar concentrations but also depended on ingredient and fraction types. Insoluble binary (Ca-Proteins and/or PA-Ca) and ternary complexes (PA-Ca-Proteins) were evidenced for pH ≤ 7.0 in concentrate dispersions. Around neutral pH, proteins were involved in soluble binary complexes with PA and Ca. Even small amounts of soluble ternary complexes were identified at pH 7.5. Alongside, highly denatured protein structures of commercial isolate ingredients resulted in low solubility. Calcium binding capacities of laboratory scale protein systems were shown to be mainly driven by phytic acid. Significantly higher PA content in 7S vicilin dispersions led to better calcium chelation properties vs 11S legumin ones (lower in PA). Thermal aggregation resulted in modified complexes in terms of types and sizes. Consequently, depending on added calcium ions, phytic acid contents and pH conditions, it seems possible to monitor the colloidal stability of protein systems. These new findings provided interesting data about adequate ingredients and/or environmental conditions to be preferentially used to master formulation, taste and stability of pulse-based foods
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Jesus, Florence de. "Caractérisation des propriétés de la partie membranaire de l'ATPase-Ca2+ du réticulum sarcoplasmique du muscle squelettique de lapin : étude de la perméabilité passive aux cations monovalents et divalents". Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10229.
Testo completoAbstract (sommario):
L' atpase-ca#2#+ serca-1a initie la relaxation musculaire en pompant activement le calcium cytoplasmique à l'intérieur du reticulum sarcoplasmique. Le domaine transmembranaire de cette protéine a été caractérisé en étudiant les phénomènes de perméabilité passive. L'utilisation de la thapsigargine, un inhibiteur spécifique de la protéine a montré que l'enzyme est permeante aux cations monovalents (k#+ ou na#+), en absence de calcium externe (ca#1#/#2n0,2-0,15 um) et de protons (pk=7,4 a 0c). Cette permeation est inhibée par la thapsigargine et le vanadate qui stabilisent la protéine dans sa conformation e#2. Deux modèles peuvent décrire cette translocation de cations monovalents: - soit l'état e#2 de la protéine correspond à un état perméable qui permet le passage des cations par les sites de transport membranaires lorsque ceux-ci sont libres. - soit le passage des cations monovalents s'effectue lors des transconformations e#1e#2 de la protéine, lorsque les sites calciques sont libres. Ce schema est accrédité par le taux de passage des cations monovalents (0,5 s#-#1) qui est voisine de celle de la transconformation e#2e#1. Physiologiquement, cette perméabilité aux cations monovalents pourrait compenser les effets électriques engendrés par le pompage de calcium. La perméabilité au calcium a été caractérisée sur la protéine dont la partie membranaire a été dissociée du domaine catalytique. Ce découplage a été obtenu en associant une trypsinolyse limitée du domaine cytoplasmique et un traitement thermique. Dans ces conditions, le domaine cytoplasmique de la protéine est majoritairement détruit tandis que le domaine transmembranaire et l'étanchéité des vésicules sont bien conservés. Ainsi traitées, la perméabilité passive au calcium des vésicules réticulaires augmente. Cette perméabilité est régulée par les mêmes agents que celle des cations monovalents. Ces résultats permettent désormais d'appréhender l'activité intrinsèque du domaine membranaire de l'atpase-ca#2#+. Ils seront appliqués à l'étude fonctionnelle des mutants transmembranaires exprimés dans la levure s. Cerevisiae
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Forristal, Ailish. "MRS studies on the role and function of divalent cations in the cerebral cortex". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299709.
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Wang, Yu-Wen. "Substitution of Catalytic Calcium to Divalent Metal Cations in Paraoxonase 1 (PON1): Implications for the Catalytic Mechanism". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1525760969900355.
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JOUSSE, FABIEN. "Adsorption de l'oxygene dans des zeolithes a a cations monovalents et divalents spectrometrie infrarouge, calcul de l'interaction et deplacement de la frequence vibrationnelle". Paris 6, 1994. http://www.theses.fr/1994PA066605.
Testo completoAbstract (sommario):
Ce travail presente d'une part l'analyse infrarouge de la bande induite de l'oxygene adsorbe dans differentes zeolithes (naa, nacaa, caa), et d'autre part un calcul du deplacement des niveaux vibrationnels de la molecule perturbee par l'interaction avec les ions du cristal. Cette etude montre que le deplacement de frequence n'est pas relie de facon simple a la configuration d'equilibre de la molecule dans son site d'adsorption. La precision des resultats est limitee par l'absence de donnees sur les derivees secondes par rapport a la coordonnee interne de la polarisabilite et du quadrupole. La comparaison aux resultats experimentaux a permis d'evaluer l'ordre de grandeur de ces quantites
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"Exploring calcium channels using divalent cations and specific channel blockers in frog sympathetic neurons". Tulane University, 2001.
Cerca il testo completoAbstract (sommario):
In the present study, distinctive interactions of divalent cations and specific blockers with calcium channels were exploited to probe several functional features related to permeation through calcium channels in frog sympathetic neurons In the first study, our experiments have focused on resolving a paradox why the whole-cell current has not been observed under typical recording conditions for one type of calcium channel that is highly expressed in frog sympathetic neurons. These channels are referred to as Ef-channels, and they are present in the membrane at a density greater than the channels that carry ∼90% of whole-cell current in low Ba2+, but Ef-current has not been detected in low Ba2+. Using Ca2+, instead of Ba2+ as the charge carrier, we recorded a possible E-type current in frog sympathetic neurons. The current contributed about 12% of total current at peak voltage in 3 mM Ca2+ , and increased at voltages more hyperpolarized to the peak, reaching ∼40% at -30 mV. The presence of Ef-current in 3 mM Ca2+ , suggests a potential role of Ef-channels in regulating calcium influx into sympathetic neurons In the second study, the effect of Ba2+ on the block of N-channels by o-conotoxin GVIA (oCGVIA) was investigated. oCGVIA has been reported to be an irreversible blocker of N-type calcium channels (Cav 2.2). Surprisingly, oCGVIA block was rapidly reversed in 0 Ba2+. The off-rate of oCGVIA from N-channels was dependent on [Ba2+]o, since at an intermediate concentration (3 muM Ba2+), current recovered with a tau of 64 +/- 16 s (n = 6), significantly slower than in 0 Ba2+ but faster than in 3 mM Ba2+ In the final study, we examined Ca2+ permeation through N-channels. Models of permeation through voltage-gated Ca2+ channels have been constructed based on L-channel data. Specifically, our goal was to determine if an apparent high affinity binding site underlies channel selectivity for Ca2+, and an apparent low affinity binding site supports Ca2+ conductance in N-channels. Our data confirmed that Ca2+ binding inside N-channels is involved in both Ca2+ selectivity and conductance. (Abstract shortened by UMI.)acase@tulane.edu
Libri sul tema "Calcium cations divalents"
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Houillier, Pascal. Magnesium homeostasis. A cura di Robert Unwin. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0027.
Testo completoAbstract (sommario):
Magnesium is critically important in the process of energy release. Although most magnesium is stored outside the extracellular fluid compartment, the regulated concentration appears in blood. Urinary magnesium excretion can decrease rapidly to low values when magnesium entry rate into the extracellular fluid volume is low, which has several important implications: cell and bone magnesium do not play a major role in the defence of blood magnesium concentration; while a major role is played by the kidney and especially the renal tubule, which adapts to match the urinary magnesium excretion and net entry of magnesium into extracellular fluid. In the kidney, magnesium is reabsorbed in the proximal tubule, the thick ascending limb of the loop of Henle (TALH), and the distal convoluted tubule (DCT). Magnesium absorption is mainly paracellular in the proximal tubule and TALH, whereas it is transcellular in the DCT. The hormone(s) regulating renal magnesium transport and blood magnesium concentration are not fully understood. Renal tubular magnesium transport is altered by a number of hormones, mainly in the TALH and DCT. Parathyroid hormone, calcitonin, arginine vasopressin, ß-adrenergic agonists, and epidermal growth factor, all increase renal tubular magnesium reabsorption; in contrast, prostaglandin E2 decreases magnesium reabsorption. Non-hormonal factors also influence magnesium reabsorption: it is decreased by high blood concentrations of calcium and magnesium, probably via the action of divalent cations on the calcium-sensing receptor; metabolic acidosis decreases, and metabolic alkalosis increases, renal magnesium reabsorption.
Capitoli di libri sul tema "Calcium cations divalents"
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Nara, Masayuki, Hisayuki Morii e Masaru Tanokura. "Coordination to Divalent Cations by Calcium-Binding Proteins". In Methods in Molecular Biology, 127–34. New York, NY: Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9030-6_9.
Testo completo
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Westbrook, Gary L., e Mark L. Mayer. "Divalent Cations as Modulators of NMDA-Receptor Channels on Mouse Central Neurons". In Calcium and Ion Channel Modulation, 383–93. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0975-8_32.
Testo completo
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Stern, Paula H. "Interactions of Calcemic Hormones and Divalent Cation Ionophores on Fetal Rat Bone in Vitro". In Calcium in Biological Systems, 541–47. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4613-2377-8_58.
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Cox, Jos A. "Divers Models of Divalent Cation Interaction to Calcium-Binding Proteins: Techniques and Anthology". In Methods in Molecular Biology, 15–35. Totowa, NJ: Humana Press, 2012. http://dx.doi.org/10.1007/978-1-62703-230-8_2.
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Colwell, Frederick S., Robert W. Smith, F. Grant Ferris, Anna-Louise Reysenbach, Yoshiko Fujita, Tina L. Tyler, Joanna L. Taylor et al. "Microbially Mediated Subsurface Calcite Precipitation for Removal of Hazardous Divalent Cations: Microbial Activity, Molecular Biology, and Modeling". In ACS Symposium Series, 117–37. Washington, DC: American Chemical Society, 2005. http://dx.doi.org/10.1021/bk-2005-0904.ch006.
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Yatime, Laure. "Structural Analysis of S100A8 Complex with Zinc and Calcium: A General Protocol for the Study of S100 Proteins in the Presence of Divalent Cations by X-Ray Crystallography". In Methods in Molecular Biology, 417–35. New York, NY: Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9030-6_26.
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Singh, Anu, Ritesh Verma, Preeti Thakur, Atul Thakur e Fayu Wan. "Structural Analysis of Piezoelectric Perovskite Materials". In Biomedical Applications of Perovskites: The Era of Bio-Piezoelectric Systems, 40–59. BENTHAM SCIENCE PUBLISHERS, 2024. http://dx.doi.org/10.2174/9789815256383124010005.
Testo completoAbstract (sommario):
Perovskite (Calcium titanium oxide)was discovered in 1839 by Alekseevich Perovski, a Russian mineralogist. Perovskites are materials with the same structure as calcium titanium oxide (CaTiO3 ) mineral or you can say that all the materials with the same structure as CaTiO3 are perovskites. The basic structure of perovskite is ABX3 , where the A-site is generally occupied by large twelve coordinated cations and B by smaller, octahedrally coordinated cations, and X is a common anion, for instance, Oxygen. A cation is divalent and B is tetravalent cation. Tilting of BO6 octahedra through B-O-B linkage results in rhombohedral, orthorhombic and tetragonal structures. The structure of perovskites can be modified by doping and altering synthesis techniques, such as by changing pH value, calcination temperature, and calefactive velocity. Perovskite materials have a wide range of applications in different fields, such as solar cells, photodetectors, sensors, water purification, etc
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Sheterline, Peter, Jon Clayton e John C. Sparrow. "Ligand-binding sites". In Actin, 88–118. Oxford University PressOxford, 1999. http://dx.doi.org/10.1093/oso/9780198504634.003.0003.
Testo completoAbstract (sommario):
Abstract There is a single, exchangeable high-affinity divalent-cation-binding ,site located ,,within the cleft of actin close to the nucleotide and three or more intermediate and lower affinity cation binding sites elsewhere on the molecule (see Table 2 and [34] for review). The high-affinity cation-binding site has relative affinities for cation in the order Ca> Mn >Cd> :Mg > Zn > Ni > Sr [425,426, 427, 399, 1277], whilst the lower affinity sites do not greatly discriminare between calcium and magnesium and will bind monovalent cations [377].
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"Aa". In Biochemistry and Molecular biology, a cura di Dr AD Smith, SP Datta, Dr G. H. Smith, P. N. Campbell, Dr R. Bentley, Dr HA McKenzie, Dr DA Bender et al., 1–58. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198547686.003.0001.
Testo completoAbstract (sommario):
Abstract A23187 or calcimycin a toxic and weakly antibiotic substanceisolated from cultures of Streptomyces chartreusensis. It is alipophilic 523 Da monocarboxylic acid of complex structure,two molecules of which form stable lipid-soluble complexes atpH 7.4 with one atom of certain divalent metal cations, especiallyMn2+ , Ca2+ , and Mg2+ ; monovalent cations are boundonly weakly. It also forms lipid-soluble complexes with certainamino acids. It is used experimentally as a calcium ionophore.
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Susanna Tojkander, Sari. "TRPV Family Ion Channels in the Mammary Epithelium: Role in Normal Tissue Homeostasis and along Breast Cancer Progression". In Ion Channels - From Basic Properties to Medical Treatment [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103665.
Testo completoAbstract (sommario):
Calcium homeostasis directs various intracellular cascades and therefore strict spatio-temporal control of calcium influx is also crucial for diverse physiological processes. In the mammary gland, calcium is important for the specialized tasks of this organ during lactation, but it also guides other structural and functional features of the mammary epithelium and in this way the maintenance of the whole tissue. Transient receptor potential, TRP, family ion channels are cationic channels, permeable to both monovalent and divalent cations and play a role in the influx of calcium mainly through the plasma membrane. These channels also represent vital calcium entry routes in the mammary epithelium and may thus act as central players in the preservation of calcium balance within this tissue. Moreover, TRP family channel proteins are abnormally expressed in breast cancers and may promote cancer progression through deregulation of intracellular signaling, consequently triggering several hallmarks of cancer. This chapter concentrates on the role of transient receptor potential vanilloid, TRPV, a subfamily of proteins in the calcium-dependent functions of normal mammary epithelium and the evident role of these channel-forming proteins along breast cancer progression.
Atti di convegni sul tema "Calcium cations divalents"
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Rousseau, David, e Mathieu Salaün. "Impact Of Cation Exchange On Polymer In-Situ Viscosity: An Experimental Investigation For A Low-Salinity Polymer Flooding Case". In International Petroleum Technology Conference. IPTC, 2023. http://dx.doi.org/10.2523/iptc-22907-ms.
Testo completoAbstract (sommario):
Abstract Cation exchange occurs when water with a different salinity as the connate brine is injected in a reservoir. During polymer flooding operations, the potential release of divalent cations by the rock can have a detrimental impact on the in-situ viscosity in the polymer bank. The objective of this work was to assess for the risk related to cations exchange in an Argentinian oilfield and to provide guidelines for the injection water design. Reservoir rock samples were first submitted to mineralogical analysis involving scanning-electron microscopy (SEM), X-Ray Diffraction (XRD) and determination of their Cation Exchange Capacities (CEC). Coreflood tests were then performed where the effluents were analyzed for their cations composition. In these experiments, two main scenarios for the composition of the low-salinity injection water (with or without softening) were investigated and the transport properties of the polymer were determined. As a more exploratory approach, polymer was also injected in a 12-meter-long slim tube filled with crushed reservoir rock, to assess if it could be exposed to released cations. The results showed that all reservoir rocks investigated had high CEC, which was consistent with their high clay contents, and that significant cations exchanges took place during low salinity water injection, although no formation damage occurred, showing the stability of the clays. During injection of the softened water, evidences of significant divalent (and monovalent) cations release from the rock were found. During injection of the unsoftened water, a marked and long-term adsorption of the injected calcium cations was observed, corresponding to a depletion in calcium of the injected water. This suggests that, quite counter-intuitively, using unsoftened water as polymer make up water could be interesting in view of economics because the cations exchanges could entail an increase of the in-situ viscosity. The coreflood test results also showed that the presence of polymer in the injected water had no impact on the cations exchanges mechanisms. The partial results from the slim tube injection test suggested, however, that the retardation of the polymer bank caused by polymer adsorption was sufficient to avoid for its viscosity to be affected by the changes in cations distribution. This study illustrates the importance of cation exchange mechanisms and their potential impact for polymer flooding. It also shows that these effects can be investigated in a representative manner at the lab and that practical guidelines for the composition of the polymer injection water can be deduced from the experiments, provided a risk for in-situ viscosity reduction is identified.
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Fisher, Nicholas, Marc Lehmann, Steve Brunt e Mark Gloyn. "Selection of a Flocculant to Assist in Divalent Cation Removal in a MEG Pre-Treatment Process". In Offshore Technology Conference Asia. OTC, 2022. http://dx.doi.org/10.4043/31690-ms.
Testo completoAbstract (sommario):
Abstract When monoethylene glycol (MEG) is used to provide hydrate protection for gas condensate production, MEG pre-treatment, reconcentration and reclamation systems are generally employed to recover and reuse the MEG. Prior to reconcentration, low solubility salts of divalent cations such as calcium, iron, strontium and magnesium, that may be present in the Rich MEG, are removed in a MEG pre-treatment process. This process involves the addition of a base, such as NaOH or KOH, to the Rich MEG at elevated temperatures to convert dissolved carbon dioxide to carbonate ions and so precipitate the cations, as their respective insoluble carbonate or hydroxide salts. When enough residence time is available within the process these precipitated salts are removed from the Rich MEG stream through physical separation. For onshore based MEG systems, this is usually accomplished via settling tanks. However, in offshore systems the residence time for crystallization and settling becomes limited due to vessel sizes imposed by facility space limitations so precipitated salts are actively removed using mechanical equipment such as centrifuges. Centrifuges are only effective when crystals reach threshold particle sizes. Contaminants in MEG such as dissolved hydrocarbons and magnesium ions can inhibit crystal growth of calcium and iron carbonate. This study details the development of testing methodologies to screen chemistries to assist in particle agglomeration and led to the identification of a promising class of chemistries that could be applied in MEG Pre-treatment for the flocculation of cation salts.
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Andersen, Pål Østebø, Sander Sunde Herlofsen, Reidar Inge Korsnes e Mona Wetrhus Minde. "Flow-Through Experiments of Reactive Ba-Sr-Mg Brines in Mons Chalk at North Sea Reservoir Temperature at Different Injection Rates". In SPE EuropEC - Europe Energy Conference featured at the 84th EAGE Annual Conference & Exhibition. SPE, 2023. http://dx.doi.org/10.2118/214367-ms.
Testo completoAbstract (sommario):
Abstract Chalk reservoirs in the North Sea of Norway contain significant amounts remaining oil and gas, and are potential candidates for enhanced recovery by modifying the injected brine composition. This work investigates how brines with divalent cations Ba, Sr and Mg interact when injected into chalk (CaCO3). Ba and Sr are often associated with mineral precipitation and occur in formation water while Mg is present in seawater, commonly injected in chalk. Relatively clean (>99% calcite) outcrop chalk cores from Mons, Belgium, were flooded at 130 °C in triaxial cells with four brines containing 0.12 mol/L divalent cations: either 0.06 mol/L Sr and Ba, 0.06 mol/L Sr and Mg, or 0.12 mol/L Ba or Sr. Each brine was injected in a separate core, with 100 to 150 pore volumes. The injection rate was varied between 0.5 and 8 pore volumes per day. Produced brine was analyzed continuously and compared with the injected brine composition. After flooding, the cores flooded with only Ba or only Sr were cut into slices and analyzed locally in terms of Scanning Electron Microscopy (SEM), matrix density, specific surface area and X-Ray diffraction. In all experiments, the produced divalent cation concentration was reduced compared to the injected value. The total reduction of injected cation concentration closely equaled the produced Ca concentration (from calcite dissolution). When flooding 0.12 mol/L Sr, the Sr concentration depleted 50%, while when flooding 0.12 mol/L Ba, 10% Ba depleted. When injecting equal concentrations of Ba and Sr, 40% Sr and 7% Ba depleted, while with equal concentrations of Mg and Sr injected, ~50% Sr was retained and almost no Mg depleted. Sr appeared to dominate and suppress other reactions. There was little sensitivity in steady state concentrations with variation in injection rate. The similar modification of the brine regardless of residence time suggests the reactions reached equilibrium. Cutting the cores revealed a visually clear front a few cm from the inlet. The material past the front was indistinguishable from unflooded chalk in terms of density, specific surface area, micro scale structure, porosity and composition (XRD and SEM-EDS). The material near the inlet was clearly altered. Images, XRD, SEM-EDS and geochemical simulations indicated that BaCO3 and SrCO3 formed during BaCl2- and SrCl2-flooding, respectively. The simulations also predicted equal exchange of cations to occur. The matrix densities, porosities and the distance traveled by the front corresponded with these minerals and suggested that the chalk was completely converted to these minerals behind the front. It was demonstrated that Ba-, Sr-, Mg-brines and their mixtures can be highly reactive in chalk without clogging the core after tens of pore volumes. This is because precipitation of minerals bearing these ions associates with simultaneous dissolution of calcite. The Ca-, Ba-, Sr-mineral reactions are effectively in equilibrium. Previous investigations with MgCl2 show rate dependent results and smoother alterations, indicating that Mg-mineral reactions at same conditions have longer time scale.
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Al Murayri, Mohammed T., Dawood S. Sulaiman, Anfal Al-Kharji, Munther Al Kabani, Ken S. Sorbie, Giulia Ness, Malcolm J. Pitts e Mehdi Salehi. "Scale Mitigation for Field Implementation of Alkaline-Surfactant-Polymer ASP Flooding in a Heterogeneous High Temperature Carbonate Reservoir with High Divalent Cation Concentration in Formation Water". In Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/207573-ms.
Testo completoAbstract (sommario):
Abstract An alkaline-surfactant-polymer (ASP) pilot in a regular five spot well pattern is underway in the Sabriyah Mauddud (SAMA) reservoir in Kuwait. High divalent cation concentrations in formation water and high carbonate concentration of the ASP formulation makes the formation of calcite scale a concern. The main objective of this study is to investigate the severity of the calcium carbonate (CaCO3) scaling issues in the central producer in pursuit of a risk mitigation strategy to treat the potential scale deposition and reduce the flow assurance challenges. Calcite scaling risk in terms of Saturation Ratio (SR) and scale mass (in mg/L of produced water) in the pilot producer is potentially very severe and the probability of forming calcium carbonate scale at the production well is high. Produced Ca2+ concentration is high (> 800 mg/l), which makes the equilibrated calcite SR severe (> 500) and results in significant amount of scale mass precipitation. Different flooding strategies were modelled to evaluate a variety of flood design options to mitigate scale risks (varying slug size, Na2CO3 concentration, and volume of softened pre-flush brine), with marginal impact on scale formation. When the high permeability contrast of the different layers is reduced (to mimic gel injection), calcite SR and precipitated scale mass is significantly reduced to manageable levels. The option of injecting a weak acid in the production well downhole can suppress most of the expected calcite scale through reduction of the brine pH in the produced fluid stream for the ASP flood. Weak acid concentrations in the range of 4,000 to 5,000 mg/l are forecast to mitigate scale formation.
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Hassan, Anas M., Emad W. Al-Shalabi, Aaron G. Tellez Arellano, Muhammad S. Kamal, Shirish Patil e Syed M. Shakil Hussain. "Mechanistic Modeling for Low Salinity Polymer (LSP) Flooding in Carbonates Under Harsh Conditions". In SPE Annual Technical Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/215059-ms.
Testo completoAbstract (sommario):
Abstract Low Salinity Polymer (LSP) injection is a hybrid synergistic Enhanced Oil Recovery (EOR) technique that improves displacement efficiency by combining the advantages of both low salinity and polymer flooding methods. Nevertheless, proper design of this technique at field-scale requires a predictive mechanistic model that captures the geochemical interactions that occur within the polymer-brine-rock (PBR) system. A few studies have so far attempted to mechanically model the LSP injection process. Therefore, to achieve a realistic mechanistic model in this contribution, we used the validated coupled MRST-Iphreeqc simulator, which integrates the MATLAB Reservoir Simulation Toolbox (MRST) with IPhreeqc geochemical software, for gaining more knowledge about the geochemical interactions within the PBR system during LSP flooding. In particular, this study investigates the effect of water chemistry (salinity and hardness), rock-permeability, hydrolysis, and rock-mineralogy (dolomite and calcite) on polymer viscosity in carbonates under harsh conditions. In addition, charge ratio (CR) analysis was conducted for risk evaluation of polymer viscosity loss as a function of salinity, hardness, and rock mineralogy variations, and thus, the capacity of cation exchange during LSP injections was examined. The outcome of this study shows that the LSP solutions demonstrated higher divalent cation (Ca2+ + Mg2+) concentrations than the produced fluids of the LS injections with no polymer. The scenario of twice spiked salinity (1246 ppm) is more beneficial than the twice diluted salinity (311.5 ppm), as per their corresponding polymer viscosity losses of 35% and 72%, respectively. For the dolomite model, the 10-times spiked hardness was found to be superior to the hardness case of 10-times diluted, as per their corresponding polymer viscosity losses of 30% and 60%, respectively. For the calcite model, the 10-times spiked hardness was found to be more preferable than the 10-times diluted hardness, as per their corresponding polymer viscosity losses of 26% and 53%, respectively. Therefore, in terms of reducing polymer viscosity loss, calcite model was the most advantageous rock-forming mineral. For LSP injection de-risking strategies, the impact of the divalent cation was associated with the CR value. Thus, it is necessary to obtain a CR value that is ideal and at which the viscosity loss is minimal. According to the CR calculations, a CR > 1 indicates minimal viscosity loss in the LSP-solution, which correlates to the cation threshold concentration of 130 ppm. The LSP solution is anticipated to undergo considerable viscosity loss at CR < 0.5. Additional risk evaluation for viscosity loss would be required when 0.5 < CR < 1. Accordingly, to optimize the LSP process in carbonates, careful design of the divalent cations (Ca2+ + Mg2+) is essential, as it can affect the LSP solution viscosity. Hence, the benefit of this study includes providing consistent data for further research into optimizing the LSP injection strategy.
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Brenas, T., A. L. Vincent e N. Lesage. "Mineral Sulfite Scale Issues: Water Compatibility and Mitigation Assessment". In Offshore Technology Conference. OTC, 2024. http://dx.doi.org/10.4043/35497-ms.
Testo completoAbstract (sommario):
Abstract This paper aims to study the compatibility of two mineral waters (containing sulfites and calcium) likely to produce large quantity of sulfites scale if they are mixed. This scale formation impacts the production facilities and is hardly recoverable. Consequently, this work is assessing the scale risks simulation and simple laboratory tests. The results of both methods show very high risks of precipitation likely to disturb process operations. The scale quantity is also very sensitive to pH modification. Then, three different scale mitigations solutions were evaluated to prevent any deposit formation by working either on the sulfites of the first water or on the cations of the second one. These measures are: The formation water divalent cations sequestration thanks to Ethylenediaminetetraacetic acid (EDTA) as complexing agent.The early precipitation of sulfites thanks to CaCl2 or CaCO3 addition.The chemical scale mitigation by antiscalant injection. The injection of scale inhibitors did not show any efficiency whatever the scale inhibitor and the concentration (30, 60 and 120 ppm) for process water at pH = 8 and 12. The sequestration requires a high amount of EDTA (5.9 g EDTA/g divalent cations) to be fully effective due to stochiometric conditions necessity. The early precipitation with 120 g.L-1 of CaCl2 remains the most effective solution and enables the easy separation of sulfites salts by physical methods such as settling. The most promising solution consists in a mix of early precipitation, acidification and scale inhibitor addition.
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Abu-Al-Saud, Moataz, Subhash Ayirala, Abdulkareem AlSofi e Ali Yousef. "A Surface Complexation Modeling SCM Based Electrokinetic Solution for Chemical EOR in Carbonates". In SPE Conference at Oman Petroleum & Energy Show. SPE, 2022. http://dx.doi.org/10.2118/200027-ms.
Testo completoAbstract (sommario):
Abstract Understanding the impact of water salinity and ionic compositions on rock-fluids interactions and subsequently wettability plays a major role to determine the performance of different recovery processes in carbonate formations. Various studies have shown that surface electric charge manipulation is the main driving mechanism behind wettability alteration observed in controlled ionic composition waterflooding (CICW) processes. Therefore, investigation of electrokinetic interactions at both brine/calcite and brine/crude-oil interfaces is important to optimize the injection water compositions used for chemical enhanced oil recovery (EOR) in carbonates. In this investigation, the electrokinetic interactions of different surfactants at calcite/brine/crude-oil interfaces are studied using Surface Complexation Modeling (SCM) approach. First, the three low salinity water recipes of NaCl brine, Na2SO4 brine, SmartWater, and a high salinity water (HSW) are analyzed as baseline for zeta-potential comparison. The salinities of low salinity water recipes are fixed at the same salinity as 10-times diluted high salinity water. Then, four different surfactants are added at 0.1 wt% concentration to the brine recipes, where the first two surfactants are anionic, the third one is amphoteric, and the fourth one is non-ionic surfactant. The SCM results are compared with experimental zeta potential measurements for calcite/brine and crude oil/brine suspensions in different aqueous solutions containing surfactants. The SCM results reasonably matched the experimental zeta potential data trends obtained with different surfactants at brine/calcite and crude-oil/brine interfaces. Both the anionic surfactants altered the zeta-potential values of brine/calcite and crude-oil/brine interfaces towards more negative in all brine recipes. This impact is found to be more pronounced for SmartWater and HSW. For amphoteric surfactant that includes both anionic and cationic charges, the opposite trend is observed. The zeta potentials became less negative at calcite/brine and oil/brine interfaces thereby making it unattractive for chemical EOR in carbonates. The negative surface charge of NaCl, and Na2SO4 brines decreased when non-ionic surfactant is added to the aqueous solution. However, much favorable effect is observed with HSW in conjunction with non-ionic surfactant, wherein the zeta-potential magnitudes became increasingly negative at the two interfaces. In SCM framework, the trend is accurately captured by reducing the surface equilibrium reaction constants for divalent cations (Ca+2, and Mg+2) to result in less adsorbed concentrations of divalent cations at the interfaces. This assumption can be rationalized by the optimal phase behavior of non-ionic surfactant observed in HSW to further explain such high effectiveness from electrokinetics perspective. The novelty of this work is that it captures the electrokinetic interactions of different surfactant chemicals at calcite/brine/crude-oil interfaces besides validating the SCM results with experimental zeta potential data. These modeling results will provide new insights on defining optimal water compositions to synergize with surfactants and further improve oil recovery in carbonate reservoirs.
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Sugai, Yuichi, Nao Miyazaki, Satohiro Yanagisawa e Yoshifumi Okamoto. "Study on the application of surfactin for enhanced oil recovery". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/qugo4464.
Testo completoAbstract (sommario):
Surfactin is an anionic bio-surfactant produced by Bacillus subtilis. Although it has high capacity to decrease interfacial tension between oil and water and improve oil recovery, it has not been used for enhanced oil recovery because it forms precipitation by binding with divalent cations such as calcium ions which are contained in formation water. This study examined the countermeasure to prevent surfactin from forming the precipitation for applying it to enhanced oil recovery. Alcohols, chelating agents, a cationic surfactant and an ion capturing substance were selected as the candidates for inhibiting surfactin from forming the precipitation. Citric acid and trisodium citrate were selected as promising candidates through the measurements of turbidity of the mixture of the candidate, surfactin and calcium ions. Those chemicals also had a function as a co-surfactant for surfactin. The interfacial tension between crude oil and the mixture of citric acid or trisodium citrate (0.6 %) and surfactin (0.3 %) was decreased to 0.1 mN/m, whereas that between crude oil and 0.3 % of surfactin was 3.5 mN/m (see Figure 1). The permeability of a sandstone core into which the solution containing surfactin and trisodium citrate was injected was decreased significantly, whereas citric acid could be injected into the core without significant permeability reduction. Citric acid was therefore selected as the best inhibitor and subjected to the core flooding experiments. 25 % of oil remaining after the primary oil recovery was additionally recovered by the injection of the mixture of surfactin and citric acid after the primary oil recovery (see Figure 2). Moreover, the pressure drop was not increased during the injection of the mixture of surfactin and citric acid. Those results suggest that citric acid has a dual role as the binding inhibitor and co-surfactant for surfactin.
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Zhou, Nancy C., Fangya Niu, Krishna K. Panthi, Mohammad B. Abdullah, Meng Lu, Steven Vaughan, Danhua Leslie Zhang et al. "Feasibility Study of Low-Tension-Gas Flooding Application in High Temperature High Salinity Sandstone Reservoirs". In ADIPEC. SPE, 2023. http://dx.doi.org/10.2118/216524-ms.
Testo completoAbstract (sommario):
Abstract Low-tension-gas (LTG) flooding has been demonstrated in the laboratory to improve oil recovery for tight formations with sub-20-md permeability. High temperature and high salinity (HTHS) reservoir conditions still pose significant challenges for this hybrid surfactant and gas enhance oil recovery (EOR) method. This paper presents a systematic study that includes developing low interfacial tension (IFT) surfactant formulation, investigating LTG flooding, and lab-scale reservoir simulations to evaluate the feasibility of LTG for field application in harsh reservoir conditions. The brine and crude oil analysis showed that the formation water and injection water from the interested field have total dissolved solids (TDS) up to 70,000 ppm and divalent cations, such as calcium (Ca2+) and magnesium (Mg2+) over 2,000 ppm, and the crude oil contains over 5% asphaltene and has total acid number of > 0.5 mg KOH/g. A novel synergistic blend of two commercially available long-alkyl-chain surfactants with a co-solvent was developed with ultralow IFT and acceptable foamability at 92°C. The foam injectivity core flood showed that a foam quality of 50-80% demonstrated a stable foam. The surfactant polymer (SP) core flood test using outcrop cores demonstrated the efficiency of the developed ultra-low IFT surfactant formulation. LTG core flood experiments using reservoir core plugs were performed by injecting the same low tension surfactant formulation along with gas at 50% quality followed by foam drive with the mobility control foam at 80% quality. The residual oil saturation was reduced to less than 5% by LTG flooding. The lab observed recovery was accurately modeled using UTCHEM, a chemical flooding simulator. Our experimental work demonstrates the effectiveness of LTG flooding in high temperature sandstone reservoirs with high divalent cations in high salinity formation brine. Our mechanistic models and numerical simulations for this complex surfactant and gas EOR method matched the experimental results.
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Wang, C. T., W. J. Tsai, J. C. Chen, Y. J. Shiao e J. Y. Lee. "BLEB FORMATION ON THE HUMAN PLATELET MEMBRANE SURFACE IS INDUCED BY SURFACE BOUND CALCIUM ION". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643533.
Testo completoAbstract (sommario):
the morphological sthudy by scanning electron microscopy (SEM) showed that blebs were found on cell surface of the gel-filtered human platelets when incubated in the modified Tyrode's buffer containing 8mM or higher of Ca++ for 5 min. EDTA immediately abolished blebs [Wang et al Thrombos. Haemostas., 54, 184 (1985)]. The phenomenon was further investigated. The bleb-forming cells respond ghto thrombin stimulation with as aggregation rate 30% lower than that of control. EDTA reversed the aggregation rate back to that of control. Two other divalent cations, i.e. Ba++ andSr++ at a concentration above8 mM could not induce bleb on cell jsurface. however, pseudopods were formed. In response to thrombin stimulation, the cell treasted with either Ba++or Sr++ exhibited a similar aggregation rate to that of control. Hence, calcium ions may be specifically responsible for including the bleb formation, which may retard cell function. The amount of Ca++ bound to cell surface was estimated by using 4 5CaCl2 as a probe. After incubation with 4 5CaCl2, the cell suspension was divided into two aliquots. One was immediately centrifuged through a layer of silicon oil.The other was added with EDTA prior to the centrifugation. The difference between radioactivity of the former and that of the latter represented the amount of surface bound Ca++. We found that 1200 pmole/108 cells was bound on cell ksurface by incubating the cells in 10 mM Ca++ for 5 min. The same quantity was also found in the cells incubated with 5 mM Ca++ for 60 min. However, the latter had no bleb on the cell surface as revealed by SEM. The result implies that the bleb formation is caused by an impact of large amount of Ca++ on cell surface.