Journal articles on the topic 'Cations'
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1
Lindner, Christoph, Raman Tandon, Boris Maryasin, Evgeny Larionov, and Hendrik Zipse. "Cation affinity numbers of Lewis bases." Beilstein Journal of Organic Chemistry 8 (August 31, 2012): 1406–42. http://dx.doi.org/10.3762/bjoc.8.163.
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Using selected theoretical methods the affinity of a large range of Lewis bases towards model cations has been quantified. The range of model cations includes the methyl cation as the smallest carbon-centered electrophile, the benzhydryl and trityl cations as models for electrophilic substrates encountered in Lewis base-catalyzed synthetic procedures, and the acetyl cation as a substrate model for acyl-transfer reactions. Affinities towards these cationic electrophiles are complemented by data for Lewis-base addition to Michael acceptors as prototypical neutral electrophiles.
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Elicharova, Hana, and Hana Sychrova. "Fluconazole affects the alkali-metal-cation homeostasis and susceptibility to cationic toxic compounds of Candida glabrata." Microbiology 160, no. 8 (August 1, 2014): 1705–13. http://dx.doi.org/10.1099/mic.0.078600-0.
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Candida glabrata is a salt-tolerant and fluconazole (FLC)-resistant yeast species. Here, we analyse the contribution of plasma-membrane alkali-metal-cation exporters, a cation/proton antiporter and a cation ATPase to cation homeostasis and the maintenance of membrane potential (ΔΨ). Using a series of single and double mutants lacking CNH1 and/or ENA1 genes we show that the inability to export potassium and toxic alkali-metal cations leads to a slight hyperpolarization of the plasma membrane of C. glabrata cells; this hyperpolarization drives more cations into the cells and affects cation homeostasis. Surprisingly, a much higher hyperpolarization of C. glabrata plasma membrane was produced by incubating cells with subinhibitory concentrations of FLC. FLC treatment resulted in a substantially increased sensitivity of cells to various cationic drugs and toxic cations that are driven into the cell by negative-inside plasma-membrane potential. The effect of the combination of FLC plus cationic drug treatment was enhanced by the malfunction of alkali-metal-cation transporters that contribute to the regulation of membrane potential and cation homeostasis. In summary, we show that the combination of subinhibitory concentrations of FLC and cationic drugs strongly affects the growth of C. glabrata cells.
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Morillo, E., J. L. Pérez-Rodríguez, and C. Maqueda. "Mechanisms of interaction between montmorillonite and 3-aminotriazole." Clay Minerals 26, no. 2 (June 1991): 269–79. http://dx.doi.org/10.1180/claymin.1991.026.2.10.
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AbstractThe adsorption of aminotriazole, at its solution pH, with montmorillonite saturated with different cations has been studied. A pesticide-montmorillonite complex is formed through interlamellar cations which are not displaced. Aminotriazole is situated mostly as a polarized molecule around Mg2+ and Zn2+ cations, removing a great amount of water. In Na+- and Li+-montmorillonite, the pesticide remains as a non-polarized molecule, hydration water being retained in the interlamellar space; the pesticide is coordinated to interlamellar cations through water bridges. For all samples a proportion of cationic aminotriazole is also adsorbed, the amount being greater with increasing polarizing power of the interlamellar cation; consequently, in Fe3+-montmorillonite all the aminotriazole adsorbed is in the cationic form.
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Cozens, Frances L., V. M. Kanagasabapathy, Robert A. McClelland, and Steen Steenken. "Lifetimes and UV-visible absorption spectra of benzyl, phenethyl, and cumyl carbocations and corresponding vinyl cations. A laser flash photolysis study." Canadian Journal of Chemistry 77, no. 12 (December 5, 1999): 2069–82. http://dx.doi.org/10.1139/v99-210.
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Benzyl (4-MeO, 4-Me, and 4-methoxy-1-naphthylmethyl), phenethyl (4-Me2N, 4-MeO, 3,4-(MeO)2, 4-Me, 3-Me, 4-F, 3-MeO, 2,6-Me2, parent, and 4-methoxy-1-naphthylethyl) and cumyl (4-Me2N, 4-MeO, 4-Me, parent) cations have been studied by laser flash photolysis (LFP) in 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). In most cases styrene or α-methylstyrene precursors were employed for the phenethyl and cumyl ions, the intermediate being obtained by solvent protonation of the excited state. Benzyl cations were generated by photoheterolysis of trimethylammonium and chloride precursors. While a 4-MeO substituent provides sufficient stabilization to permit observation of cations in TFE, cations with less stabilizing substituents usually require the less nucleophilic HFIP. Even in this solvent, the parent benzyl cation is too short-lived (lifetime <20 ns) to be observed. When generated in HFIP, phenethyl cations can be seen to react with unphotolyzed styrene, giving rise to dimer cations that are observed to grow in as the initial phenethyl cation decays. The dimer cations, in common with the oligomer cations seen in cationic styrene polymerization, have a λmax 15-20 nm higher than the monomer and react with both solvent and styrene several orders of magnitude more slowly. This stabilization relative to the phenethyl may reflect an interaction with the aryl group present at the gamma-carbon. Cations 4-MeOC6H4C+(R)-CH3 (R = Me, Et, i-Pr, t-Bu, cyclopropyl, C6H5, 4-MeOC6H4) were generated in TFE via the photoprotonation route. The alkyl series shows that steric effects are important in the decay reaction. The cation with R = cyclopropyl is a factor of 1.5 less reactive than the cation where R = phenyl. Several vinyl cations have also been generated by photoprotonation of phenylacetylenes. ArC+=CH2 has a reactivity very similar to that of its analog ArC+H-CH3, the vinyl cation being slightly (factors of 2-5) shorter-lived. For the various series of cations, including vinyl, substituents in the aryl ring have a consistent effect on the λmax, a shift to higher wavelength relative to hydrogen of 15 nm for 4-Me, 30 nm for 4-MeO, and 50 nm for 4-Me2N.Key words: photogenerated carbocations, carbocation lifetime, styrene, photoprotonation.
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Arnold, Donald R., and Xinyao Du. "The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 5: methanol–monoterpenes (α- and β-pinene, tricyclene, and nopol), 1,4-dicyanobenzene." Canadian Journal of Chemistry 72, no. 2 (February 1, 1994): 403–14. http://dx.doi.org/10.1139/v94-062.
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The reactivity of the radical cations of α- and β-pinene (8 and 9), tricyclene (18), and nopol (23) has been studied. The radical ions were generated, in acetonitrile–methanol (3:1), by single electron transfer (set) to the singlet excited state of 1,4-di-cyanobenzene (1). Biphenyl (3) was used as a codonor. The cyclobutane rings of the initially formed radical cations of α- and β-pinene (8+• and 9+•) cleave to distonic radical cations that react as tertiary alkyl cations and allylic radicals. The results of ab initio molecular orbital calculations (STO-3G) are consistent with the observation that the positive charge is largely associated with the tertiary alkyl moiety while the spin density is largely distributed over the allylic radical. There was no evidence, experimental or theoretical, indicative of a bonding interaction between the cationic and allylic moieties of these distonic radical cations. The cyclobutane ring cleavage is irreversible. The radical cation of tricyclene (18) also gives 1:1:1 (nucleophile:cyclopropyl:aromatic) adducts. The regio- and stereochemistry of the adducts, and the nucleophile selectivity, are all indicative of nucleophile-assisted cleavage of the radical cation (18+•). The radical cation of nopol (23+•) also cleaves to the distonic radical cation. The cyclobutane ring cleavage must be rapid; intramolecular 1,5-endo cyclization of the hydroxyl group cannot compete.
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Venkatesan, P., V. Rajakannan, and S. Thamotharan. "Crystal structure of 3-amino-1-propylpyridinium bromide." Acta Crystallographica Section E Structure Reports Online 70, no. 12 (November 29, 2014): 580–83. http://dx.doi.org/10.1107/s1600536814025665.
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The title molecular salt, C8H13N2+·Br−, crystallizes with two independent 3-aminopyridinium cations and two bromide anions in the asymmetric unit (Z′ = 2). In the pyridine ring, the N atom is alkylated by a propyl group. The dihedral angle between the mean planes of the pyridinium ring and the propyl group is 84.84 (2)° in cationA, whereas the corresponding angle is 89.23 (2)° in cationB. In the crystal, the anions and cations are linkedviaN—H...Br and C—H...Br hydrogen bonds, forming chains propagating along [100].
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Mamedova, G. A. "THE ION-EXCHANGE PROPERTIES OF NATURAL ZEOLITE MORDENITE." Fine Chemical Technologies 11, no. 1 (February 28, 2016): 29–33. http://dx.doi.org/10.32362/2410-6593-2016-11-1-29-33.
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The cation exchange properties of mordenite (a Nakhchivan natural zeolite) were studied. Ion exchange of the original cations - sodium, potassium and calcium - by magnesium, strontium, cadmium, zinc and nickel cations was carried out. It was found that in the case of Zn cations cation exchange occurs readily at a high speed and the maximum value of the degree of exchange. A low value of the degree of cation exchange is observed for Mg. This is due to the large hydration shell of magnesium, which adversely affects the cation exchange. High values of the exchange rate of Na+ cations have already been explained at the first exchange of low content of sodium cations and their location mostly in exchange for positions available. The lesser ability to exchange K+, Na+ cations than contained in the natural zeolite is due to several reasons. With an increasing number of degrees of ionic exchange value exchangeable cations K+ vary to a greater degree than the degree of exchange of the cations Na+. Firstly, the content and size of the K+ cation are greater than those of the Na+ cations. Furthermore, a part of the K+ cations is in exchange for hard cancrinites cells. It has been found that the degree of cation exchange of K+ (αK), contained in the original zeolite, with Mg2+, Ni2+, Sr2+, Zn2+, Cd2+ cations is considerably lower than the values of the degree of cation exchange of Na+ (αNa) at the same cations.
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Philipp, Jule, and Ralf Ludwig. "Clusters of Hydroxyl-Functionalized Cations Stabilized by Cooperative Hydrogen Bonds: The Role of Polarizability and Alkyl Chain Length." Molecules 25, no. 21 (October 27, 2020): 4972. http://dx.doi.org/10.3390/molecules25214972.
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We explore quantum chemical calculations for studying clusters of hydroxyl-functionalized cations kinetically stabilized by hydrogen bonding despite strongly repulsive electrostatic forces. In a comprehensive study, we calculate clusters of ammonium, piperidinium, pyrrolidinium, imidazolium, pyridinium, and imidazolium cations, which are prominent constituents of ionic liquids. All cations are decorated with hydroxy-alkyl chains allowing H-bond formation between ions of like charge. The cluster topologies comprise linear and cyclic clusters up to the size of hexamers. The ring structures exhibit cooperative hydrogen bonds opposing the repulsive Coulomb forces and leading to kinetic stability of the clusters. We discuss the importance of hydrogen bonding and dispersion forces for the stability of the differently sized clusters. We find the largest clusters when hydrogen bonding is maximized in cyclic topologies and dispersion interaction is properly taken into account. The kinetic stability of the clusters with short-chained cations is studied for the different types of cations ranging from hard to polarizable or exhibiting additional functional groups such as the acidic C(2)-H position in the imidazolium-based cation. Increasing the alkyl chain length, the cation effect diminishes and the kinetic stability is exclusively governed by the alkyl chain tether increasing the distance between the positively charged rings of the cations. With adding the counterion tetrafluoroborate (BF4−) to the cationic clusters, the binding energies immediately switch from strongly positive to strongly negative. In the neutral clusters, the OH functional groups of the cations can interact either with other cations or with the anions. The hexamer cluster with the cyclic H-bond motive and “released” anions is almost as stable as the hexamer built by H-bonded ion pairs exclusively, which is in accord with recent IR spectra of similar ionic liquids detecting both types of hydrogen bonding. For the cationic and neutral clusters, we discuss geometric and spectroscopic properties as sensitive probes of opposite- and like-charge interaction. Finally, we show that NMR proton chemical shifts and deuteron quadrupole coupling constants can be related to each other, allowing to predict properties which are not easily accessible by experiment.
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Gärtner, Stefanie, Christof Suchentrunk, and Nikolaus Korber. "Coordination preferences of the alkali cations sodium and caesium in the mixed-cationic Zintl ammoniate Cs3.2Na0.8Ge9·5.3NH3." Acta Crystallographica Section C Structural Chemistry 70, no. 11 (October 11, 2014): 1036–39. http://dx.doi.org/10.1107/s2053229614021998.
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The involvement of two different alkali cations in the nonagermanide ammoniate Cs3.2Na0.8Ge9·5.3NH3[tricaesium sodium nonagermanide–ammonia (1/5.3)] provides insights into the coordination behaviour of ammonia towards sodium and caesium cations within one compound and represents the first mixed-cationic solvate structure of nonagermanide tetraanions. The compound crystallizes in the monoclinic space groupP21/mand, with the presence of pseudomerohedral twinning, mixed-cation sites and disordering of the nonagermanide cage anions, features a combination of crystallographic challenges which could all be resolved during the refinement.
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Bolanle-Ojo, Tope O., Abiodun D. Joshua, Opeyemi A. Agbo-Adediran, Ademola S. Ogundana, Kayode A. Aiyeyika, Adebisi P. Ojo, and Olubunmi O. Ayodele. "Exchange Characteristics of Lead, Zinc, and Cadmium in Selected Tropical Soils." International Journal of Agronomy 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/428569.
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Conducting binary-exchange experiments is a common way to identify cationic preferences of exchangeable phases in soil. Cation exchange reactions and thermodynamic studies of Pb2+/Ca2+, Cd2+/Ca2+, and Zn2+/Ca2+were carried out on three surface (0–30 cm) soil samples from Adamawa and Niger States in Nigeria using the batch method. The physicochemical properties studies of the soils showed that the soils have neutral pH values, low organic matter contents, low exchangeable bases, and low effective cation exchange capacity (mean: 3.27 cmolc kg−1) but relatively high base saturations (≫50%) with an average of 75.9%. The amount of cations sorbed in all cases did not exceed the soils cation exchange capacity (CEC) values, except for Pb sorption in the entisol-AD2 and alfisol-AD3, where the CEC were exceeded at high Pb loading. Calculated selectivity coefficients were greater than unity across a wide range of exchanger phase composition, indicating a preference for these cations over Ca2+. TheKeqvalues obtained in this work were all positive, indicating that the exchange reactions were favoured and equally feasible. These values indicated that the Ca/soil systems were readily converted to the cation/soil system. The thermodynamic parameters calculated for the exchange of these cations were generally low, but values suggest spontaneous reactions.
11
Waegele, Matthias M. "(Invited) Probing the Specific Adsorption of Alkali Metal Cations on Au Electrodes Under CO2 Reduction." ECS Meeting Abstracts MA2023-01, no. 46 (August 28, 2023): 2497. http://dx.doi.org/10.1149/ma2023-01462497mtgabs.
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Electrolyte engineering has recently been recognized as an integral component in the design of electrode/electrolyte interfaces for electrocatalysis. In particular, alkali metal cations of the supporting electrolyte are known to influence electrocatalytic processes. A better understanding of these cation effects requires methods capable of probing the distribution of alkali metal cations in the electrochemical double layer under reaction conditions. However, the scarcity of experimental technique capable of probing alkali metal cations greatly hinders further advances in leveraging cation effects in electrolyte engineering. In this talk, we will discuss our novel spectroscopic approach for quantifying the surface coverage of specifically adsorbed alkali metal cations, that is, the cations that are in direct contact with the electrode and therefore most likely to influence electrocatalysis. The technique is based on the use of an organic cation, tetramethylammonium (methyl4N+), as a vibrational probe of the electrode/electrolyte interface in the presence of alkali metal cations. We will discuss how we use this approach to characterize the adsorption of alkali metal cation during CO2-to-CO conversion.
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Schnetkamp, P. P. "Cation selectivity of and cation binding to the cGMP-dependent channel in bovine rod outer segment membranes." Journal of General Physiology 96, no. 3 (September 1, 1990): 517–34. http://dx.doi.org/10.1085/jgp.96.3.517.
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The properties of the cGMP-dependent channel present in membrane vesicles prepared from intact isolated bovine rod outer segments (ROS) were investigated with the optical probe neutral red. The binding of neutral red is sensitive to transport of cations across vesicular membranes by the effect of the translocated cations on the surface potential at the intravesicular membrane/water interface (Schnetkamp, P. P. M. J. Membr. Biol. 88: 249-262). Only 20-25% of ROS membrane vesicles exhibited cGMP-dependent cation fluxes. The cGMP-dependent channel in bovine ROS carried currents of alkali and earth alkali cations, but not of organic cations such as choline and tetramethylammonium; little discrimination among alkali cations (K greater than Na = Li greater than Cs) or among earth alkali cations (Ca greater than Mn greater than Sr greater than Ba = Mg) was observed. The cation dependence of cGMP-induced cation fluxes could be reasonably well described by a Michaelis-Menten equation with a dissociation constant for alkali cations of about 100 mM, and a dissociation constant for Ca2+ of 2 mM. cGMP-induced Na+ fluxes were blocked by Mg2+, but not by Ca2+, when the cations were applied to the cytoplasmic side of the channel. cGMP-dependent cation fluxes showed a sigmoidal dependence on the cGMP concentration with a Hill coefficient of 2.1 and a dissociation constant for cGMP of 92 microM. cGMP-induced cation fluxes showed two pharmacologically distinct components; one component was blocked by both tetracaine and L-cis diltiazem, whereas the other component was only blocked by tetracaine.
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Shibata, Takayuki, and Yutaka Moritomo. "Ultrafast cation intercalation in nanoporous nickel hexacyanoferrate." Chem. Commun. 50, no. 85 (2014): 12941–43. http://dx.doi.org/10.1039/c4cc04564e.
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Ultrafast cation intercalation is observed in nanoporous nickel hexacyanoferrate, which is ascribed to a fast cation diffusion constant. The cations deeply intercalate without colliding with residual surface cations.
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Morillo, E., J. L. Perez-Rodriguez, P. Rodriguez-Rubio, and C. Maqueda. "Interaction of aminotriazole with montmorillonite and Mg-vermiculite at pH 4." Clay Minerals 32, no. 2 (June 1997): 307–13. http://dx.doi.org/10.1180/claymin.1997.032.2.11.
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AbstractThe interaction of aminotriazole (AMT) at pH 4 on Wyoming montmorillonite (mainly with Na ions) and Mg-vermiculite has been studied by X-ray diffraction and infrared spectroscopy. The AMT is adsorbed on montmorillonite in the cationic form by cation exchange. The amount of pesticide adsorbed was 71 mEq/100 g, which comprises ∼91% of the CEC of this sample (78.2 mEq/100 g). Saturation was reached in 24 h, giving rise to a complex with basal spacing 12.5 Å. Vermiculite adsorbs 167 mEq/100 g, almost 20% greater than the CEC (141 mEq/100 g), and the basal spacing was stabilized at 13.68 Å after five weeks of treatment with AMT. A part of the AMT is adsorbed in cationic form, displacing a great part of the exchangeable Mg2+ cations. The rest is adsorbed in molecular form by coordination to the Mg2+ cations which remain in the interlamellar space, removing a great amount of water, and remaining in the interlamellar space of vermiculite after washing with water, probably because of a steric hindrance from the AMT cations adsorbed.
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Bigot, J., and P. Binet. "Étude des capacités d'échange et des sélectivités cationiques de parois isolées des racines de Cochlearia anglica et de Phaseolus vulgaris cultivés sur des milieux diversement salés." Canadian Journal of Botany 64, no. 5 (May 1, 1986): 955–58. http://dx.doi.org/10.1139/b86-128.
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Cochlearia anglica L. (halophyte) and Phaseolus vulgaris L. (glycophyte) were grown in media of different salinities. The root cell walls were isolated and then equilibrated with various salt solutions. There were differences between cell walls from C. anglica and P. vulgaris in both the cationic exchange capacity (computed by the sum of parietal cations) and the cell wall selectivity (evaluated by the centesimal proportion of each cation). In cell walls from plants grown without NaCl, the number of exchange sites was greater for the halophyte than for the glycophyte. Growing the plants on 42 and 85 mM NaCl medium reduced or reversed the disparities between the two species: with C. anglica, the cell wall cationic exchange capacity decreased when the growth medium salinity increased whereas this capacity tended to rise for P. vulgaris. However, the culture medium salinity did not affect the cell wall selectivity of these species for major cations. For Ca2+, the selectivity of cell walls from P. vulgaris was higher than that of cell walls from C. anglica; for the other cations, the situation was reversed.
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Marchuk, Alla, Pichu Rengasamy, Ann McNeill, and Anupama Kumar. "Nature of the clay - cation bond affects soil structure as verified by X-ray computed tomography." Soil Research 50, no. 8 (2012): 638. http://dx.doi.org/10.1071/sr12276.
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Non-destructive X-ray computed tomography (µCT) scanning was used to characterise changes in pore architecture as influenced by the proportion of cations (Na, K, Mg, or Ca) bonded to soil particles. These observed changes were correlated with measured saturated hydraulic conductivity, clay dispersion, and zeta potential, as well as cation ratio of structural stability (CROSS) and exchangeable cation ratio. Pore architectural parameters such as total porosity, closed porosity, and pore connectivity, as characterised from µCT scans, were influenced by the valence of the cation and the extent it dominated in the soil. Soils with a dominance of Ca or Mg exhibited a well-developed pore structure and pore interconnectedness, whereas in soil dominated by Na or K there were a large number of isolated pore clusters surrounded by solid matrix where the pores were filled with dispersed clay particles. Saturated hydraulic conductivities of cationic soils dominated by a single cation were dependent on the observed pore structural parameters, and were significantly correlated with active porosity (R2 = 0.76) and pore connectivity (R2 = 0.97). Hydraulic conductivity of cation-treated soils decreased in the order Ca > Mg > K > Na, while clay dispersion, as measured by turbidity and the negative charge of the dispersed clays from these soils, measured as zeta potential, decreased in the order Na > K > Mg > Ca. The results of the study confirm that structural changes during soil–water interaction depend on the ionicity of clay–cation bonding. All of the structural parameters studied were highly correlated with the ionicity indices of dominant cations. The degree of ionicity of an individual cation also explains the different effects caused by cations within a monovalent or divalent category. While sodium adsorption ratio as a measure of soil structural stability is only applicable to sodium-dominant soils, CROSS derived from the ionicity of clay–cation bonds is better suited to soils containing multiple cations in various proportions.
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Carotenuto, Gianfranco. "Isothermal Kinetic Investigation of the Water-Cations Interaction in Natural Clinoptilolite." European Journal of Engineering Research and Science 4, no. 5 (May 25, 2019): 119–25. http://dx.doi.org/10.24018/ejers.2019.4.5.1341.
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The kinetics of water adsorption by a natural zeolite (clinoptilolite) sample has been investigated by high-frequency AC current intensity measurements. According to the achieved kinetic results, cations should play a relevant role in the clinoptilolite hydration, in fact most of adsorbed water stay in the cationic sites. The water molecules associate withcation one-by-one. In particular, the forced adsorption of water molecules in a wet atmosphere is a quite slow process, while water desorption in air or dry atmosphere is a spontaneous and fast process. The observed increase of cation mobility could be adequately explained by assuming an arrangement of water molecules between the cation and the negatively charged oxygens contained in the cationic site. Such molecular arrangement could increase the strength of both dipole-cation and hydrogen bond interactions.
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Carotenuto, Gianfranco. "Isothermal Kinetic Investigation of the Water-Cations Interaction in Natural Clinoptilolite." European Journal of Engineering and Technology Research 4, no. 5 (May 25, 2019): 119–25. http://dx.doi.org/10.24018/ejeng.2019.4.5.1341.
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The kinetics of water adsorption by a natural zeolite (clinoptilolite) sample has been investigated by high-frequency AC current intensity measurements. According to the achieved kinetic results, cations should play a relevant role in the clinoptilolite hydration, in fact most of adsorbed water stay in the cationic sites. The water molecules associate withcation one-by-one. In particular, the forced adsorption of water molecules in a wet atmosphere is a quite slow process, while water desorption in air or dry atmosphere is a spontaneous and fast process. The observed increase of cation mobility could be adequately explained by assuming an arrangement of water molecules between the cation and the negatively charged oxygens contained in the cationic site. Such molecular arrangement could increase the strength of both dipole-cation and hydrogen bond interactions.
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Bondareva, L. P., and K. V. Grin. "Comparison of sorbents for extraction of nickel (II) cations from aqueous media." Proceedings of the Voronezh State University of Engineering Technologies 84, no. 1 (January 17, 2022): 238–44. http://dx.doi.org/10.20914/2310-1202-2022-1-238-244.
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Abstract: An urgent ecological and technological problem is the purification of natural and waste water from nickel cations and control of their content, since nickel cations belong to the third class and are hazardous to human health. To date, a large number of methods for removing nickel (II) cations from water have been created, the main of which can be considered sorption. In turn, the literature contains a variety of information about the most effective sorbents for cleaning from nickel cations, which sometimes contradict each other. The work determined the equilibrium characteristics of the sorption of nickel (II) cations on various polar sorbents on cation exchangers porous carboxyl Tokem 200, chelated iminodicarboxylic Amberlite IRC 748, gel sulfonic cation exchanger KU-2, experimental phosphoric acid gel KFP; strongly basic gel anion exchanger AV-17, as well as natural adsorbents flint and shungite. Sorption isotherms were obtained and described by the Langmuir equation, and the most promising materials for removing nickel cations from aqueous media were established. It has been determined that the studied sorbents, according to their equilibrium sorption characteristics, can be arranged in the following order: Tokem 200> KFP> Amberlite IRC 748> AV-17> KU-2> Flint> Shungite. The most effective sorbents for removing nickel (II) cations from aqueous solutions can be considered a prototype of a phosphate cation exchanger for gel CFP and a carboxyl porous cation exchanger Tokem 200. separating nickel cations from an aqueous solution.
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Noor, Ehteram A., and Fatma M. Al-Solmi. "Analysis of Adsorption, Ion Exchange, Thermodynamic Behaviour of Some Organic Cations on Dowex 50WX4-50/H+Cation Exchanger in Aqueous Solutions." E-Journal of Chemistry 8, s1 (2011): S171—S188. http://dx.doi.org/10.1155/2011/963603.
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The equilibrium adsorption, ion exchange characteristics of various concentrations of some organic cations from aqueous solutions onto dowex 50WEX/H+cation exchanger were studied at different temperatures in the range of 30-50 °C. The studied cations showed good adsorptive properties onto dowex 50WX4-5/H+at different concentrations and temperatures. Main adsorption behaviour was ion exchange between hydrogen ions and the organic cations as indicated from the linear relation between the initial concentration of the organic cations and the released hydrogen ions. It was found that the adsorption affinity of dowex 50WX4-50/H+towards the studied organic cations depends on the substituent type of the organic cations giving the following increasing order: 1-H < 2-OH < 3-OCH3. Thermodynamic parameters for the adsorption of the studied organic cations were evaluated and discussed. It was found that the adsorption 1-H organic cation was spontaneous, ordered, exothermic and favored with decreasing temperature. On the other hand the adsorption of both 2-OH and 3-OCH3organic cations was found to be spontaneous and disordered with enthalpy change varies significantly with increasing organic cation concentration, suggesting dipole-dipole adsorption forces as new active sites for adsorption under conditions of relatively high concentrations. Freundlich and Dubinin-Radushkevich adsorption isotherm models reasonably describe the adsorption of the studied organic cations onto dowex 50WX4-50/H+by segmented straight lines depending on the studied range of concentration, indicating the existence of two different sets of adsorption sites with substantial difference in energy of adsorption. According to Dubinin-Radushkevich adsorption isotherm model, physical-ion exchange mechanism was suggested for the adsorption of 1-H organic cation and both physical and chemical-ion exchange mechanisms were suggested for the adsorption of 2-OH and 3-OCH3organic cations depending on the studied range of concentration.
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Shainyan, Bagrat A. "Conjugative Stabilization versus Anchimeric Assistance in Carbocations." Molecules 28, no. 1 (December 21, 2022): 38. http://dx.doi.org/10.3390/molecules28010038.
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In this study, an old concept of anchimeric assistance is viewed from a different angle. Primary cations with two different heteroatomic substituents in the α-position to the cationic carbon atom CHXY–CH2+ (X, Y = Me2N, MeO, Me3Si, Me2P, MeS, MeS, Br) can be stabilized by the migration of either the X or Y group to the cation center. In each case, the migration can be either complete, resulting in the transfer of the migrating group to the adjacent carbon atom and the formation of a secondary carbocation stabilized by the remaining heteroatom, or incomplete, leading to an anchimerically assisted iranium ion. For all combinations of the above groups, these transformations have been studied by theoretical analysis at the MP2/aug-cc-pVTZ level and were shown to occur depending on the ability of anchimeric assistance by X and Y, as well as the conformation of the starting primary carbocation. In the conformers of α-amino cations with the p-orbital, C–N bond and the nitrogen lone pair in one plane, the Me2N group migrates to the cationic center to give aziranium ions. Otherwise, the second heteroatom is shifted to give iminium ions, without or with very slight anchimeric assistance. In the α-methoxy cations, the MeO group can be shifted to the cationic center to give the O-anchimerically assisted ions as local minima, the global minima being the ions anchimerically assisted by another heteroatom. The electropositive silicon tends to migrate towards the cationic center, but with the formation of a π-complex of the Me3Si cation with the C=C bond rather than a Si-anchimerically assisted cation. The phosphorus atom can either fully migrate to the cationic center (X = P, Y = S, Se) or form anchimerically stabilized phosphiranium ions (X = P, Y = O, Si, Br). The order of the anchimeric assistance for the heaviest atoms decreases in the order Se >> S > Br.
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Lamberts, Kevin, Andreas Möller, and Ulli Englert. "Enantiopure and racemic alanine as bridging ligands in Ca and Mn chain polymers." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 70, no. 6 (December 1, 2014): 989–98. http://dx.doi.org/10.1107/s2052520614021398.
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Under accelerated and controlled evaporation, chain polymers crystallize from aqueous solutions of CaIIand MnIIhalides with enantiopure L-alanine or racemic DL-alanine. In all ten solids thus obtained zwitterionic amino acid ligands bridge neighbouring cations. The exclusively O-donor-based coordination sphere around the metal cations is completed by aqua ligands; the halides remain uncoordinated and act as counter-anions for the cationic strands. Despite the differences in ionic radii and electronic structure between the main group and the transition metal cation, their derivatives with L-alanine share a common structure type. In contrast, the solids derived from DL-alanine differ and adopt structures depending on the metal cation and the halide. Homochiral chains of either chirality or heterochiral chains with different arrangements of crystallographic inversion centres along the polymer strands are encountered. On average, the six-coordinated CaIIcations, devoid of any ligand field effect, show more pronounced deviation from idealized octahedral geometry than thed-block cation MnII.
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Schepp, N. P., and Y. Rodríguez-Evora. "Generation and reactivity of the radical cations of coniferyl alcohol and isoeugenol in solution." Canadian Journal of Chemistry 81, no. 6 (June 1, 2003): 799–806. http://dx.doi.org/10.1139/v03-075.
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Nanosecond laser flash photolysis of coniferyl alcohol and isoeugenol in acetonitrile leads to the formation of transient species that are identified as the corresponding radical cations. These radical cations decay with rate constants of ca. 1 × 106 s1 in dry acetonitrile. Both radical cations react rapidly with hydroxylic solvents like water and alcohols to give 4-vinylphenoxyl radicals, indicating that these reagents behave as bases rather than nucleophiles. In addition, anionic reagents (acetate, cyanide, and chloride) react rapidly with the radical cations with second-order rate constants that are close to diffusion controlled. The main products generated in the presence of the anionic reagents are again the 4-vinylphenoxyl radicals, suggesting that these reagents also behave as bases. The lifetime of the radical cations in acidic acetonitrile was found to increase dramatically due to a shift in the radical cation vinyl phenoxyl radical acidbase equilibrium to the side of the radical cation. An estimate of the pKa of the radical cation in acetonitrile of 4.0 was obtained from the data.Key words: radical cations, laser flash photolysis, lignan, vinylphenols.
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Caurant, Daniel, Arnaud Quintas, Odile Majérus, Thibault Charpentier, and I. Bardez. "Structural Role and Distribution of Alkali and Alkaline-Earth Cations in Rare Earth-Rich Aluminoborosilicate Glasses." Advanced Materials Research 39-40 (April 2008): 19–24. http://dx.doi.org/10.4028/www.scientific.net/amr.39-40.19.
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The structure of a seven oxide aluminoborosilicate simplified nuclear glass, bearing a high amount of neodymium or lanthanum oxide (16 wt%), alkali and alkaline earth cations is studied. Nd3+ or La3+ are supposed to simulate the trivalent lanthanides and minor actinides present in nuclear wastes. In the studied glass composition, lanthanide ions have a modifying role and are located in highly depolymerized regions of the structure as shown by neodymium optical absorption and EXAFS spectroscopies. Both alkali and alkaline earth cations are present around Nd3+ ions enabling their stabilization in glass structure near non-bridging oxygen atoms (NBOs). We show that both the nature of alkali R+ and alkaline earth R'2+ cations and the K = [R'O]/([R2O]+[R'O]) ratio can greatly influence the structure of the aluminoborosilicate glass network. Three glass series were prepared for which: (i) K ratio was varied from 0 to 0.5 (Na+ and Ca2+ being respectively the only alkali and alkaline-earth cations), (ii) the nature of R+ cation was varied from Li+ to Cs+ (Ca2+ being the only alkaline earth cation and K = 0.3), (iii) the nature of R'2+ cation was varied from Mg2+ to Ba2+ (Na+ being the only alkali cation and K = 0.3). 27Al MAS NMR spectroscopy results show that (AlO4)- units are preferentially charge compensated by alkali cations rather than by alkaline-earth cations. Both R+ and R’2+ cations can compensate (BO4)- units. Nevertheless, whereas the proportion N4 of (BO4)- units increases with the size of R'2+ cations, the evolution of N4 with R+ cation size for glasses of the R series is not monotonous. The evolution of sodium ions distribution trough glass structure is followed by 23Na MAS NMR spectroscopy.
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Childs, Ronald F., Marianne D. Kostyk, Colin J. L. Lock, and Mailivaganam Mahendran. "Structural studies on 6-ethoxytetrahydropyrylium cations; stereoelectronic control in the reactions of lactonium salts." Canadian Journal of Chemistry 69, no. 12 (December 1, 1991): 2024–32. http://dx.doi.org/10.1139/v91-293.
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The structures of 6-ethoxy-2,3,4,5-tetrahydropyrylium, 1, 6-ethoxy-2-methyl-2,3,4,5-tetrahydropyrylium, 2, and 2-ethoxy-3,4,4a,5,6,7,8,8a-octahydro-1-benzopyrylium, 3, hexachloroantimonates have been determined by X-ray crystallography. In each case the tetrahydropyrylium rings exist in shallow half-chair conformations with the cationic centers C(6), C(5), O(1), and O(6) having a planar arrangement. The cations all have a Z conformation about the O(6)—C(7) bonds and it is shown that this conformation is also preferred in solution by comparison of narrow-line 13C NMR spectra in the solid state and solution. The O(1)—C(2) and O(6)—C(7) bond distances in 1–3 are significantly longer than those of comparable bonds in neutral esters. The length of the O(1)—C(2) bond is very dependent on substitution at C(2) suggesting a considerable fraction of the positive charge resides on this carbon as well as C(7). The closest cation/anion interactions present in the crystal lattices of these salts are between the chlorine atoms of the anion and the cationic center, C(6). These interactions provide information on the origin of the stereoselectivity observed in nucleophilic attack on these cations. The conformations, details of the C—O bonding, and closest contacts between cation and anion are discussed in terms of the concept of stereoelectronic control. Key words: 6-ethoxytetrahydropyrylium cations, lactonium salts, structure, X-ray, stereoelectronic control.
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Tahraoui, Zakaria, Habiba Nouali, Claire Marichal, Patrice Forler, Julien Klein, and T. Jean Daou. "Influence of the Compensating Cation Nature on the Water Adsorption Properties of Zeolites." Molecules 25, no. 4 (February 20, 2020): 944. http://dx.doi.org/10.3390/molecules25040944.
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The influence of the compensating cation (Na+, Li+, Mg2+) nature on the water adsorption properties of LTA and FAU-type zeolites was investigated. Cation exchanges were performed at 80 °C for 2 h using 1 M aqueous solutions of lithium chloride (LiCl) or magnesium chloride (MgCl2). XRF and ICP-OES analyses indicate that the cation exchange yields reach values between 59 to 89% depending on the number of exchange cycles and the nature of the zeolite and cation, while both zeolites structures are preserved during the process, as shown by XRD and solid state NMR analyses. Nitrogen adsorption-desorption experiments indicate a higher available microporous volume when sodium cations are replaced by smaller monovalent lithium cations or by divalent magnesium cations because twice less cations are needed compared to monovalent cations. Up to 15% of gain in the available microporous volume is obtained for FAU-type zeolites exchanged with magnesium cation. This improvement facilitates the adsorption of water with an increase in the water uptake up to 30% for the LTA and FAU type zeolites exchanged with magnesium. These exchanged zeolites are promising for uses in water decontamination because a smaller amount is needed to trap the same amount of water compared to their sodium counterparts.
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Yu, Hai-Ling, Wen-Yong Wang, Bo Hong, Yan-Ling Si, Tian-Liang Ma, and Ran Zheng. "First hyperpolarizabilities of Pt(4-ethynylbenzo-15-crown-5)2(bpy) derivatives with the complexation of mono-cations (Li+, Na+, K+) and di-cations (Mg2+, Ca2+): development of a cation detector." RSC Advances 7, no. 66 (2017): 41830–37. http://dx.doi.org/10.1039/c7ra04919f.
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Suryanti, Venty, Fajar Rakhman Wibowo, Ahmad Marzuki, and Meiyanti Ratna Kumala Sari. "Cation Sensing Capabilities of A Nitrophenyl Cinnamaldehyde Derivative." Molekul 15, no. 3 (November 27, 2020): 191. http://dx.doi.org/10.20884/1.jm.2020.15.3.654.
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The cationic chemosensor based on organic compound bearing an aminophenol moiety as a receptor for metal analyte and a cinnamaldehyde moiety as chromophoric fragment has been developed. In this work, we report the colorimetric sensing of nitrophenyl cinnamaldehyde derivative, namely methyl-3-(2-hidroxy-5-nitrophenyl amino)-3-phenylpropanoate, towards a variety of metal cations, such as Cu2+, Fe3+, Ni2+ and Zn2+. The cation sensing abilities of the sensor were observed for Cu2+and Fe3+ with a color change from colorless to pink and faint yellow, respectively, The characteristic UV-Vis spectra changes were observed upon addition of Cu2+and Fe3+ cations. The hypsochromic absorption spectra shifts were obtained, indicating the cations and sensor complexations had formed. A metal-to-ligand-charge-transfer (MLCT) had occurred and the charge density of the sensor changed resulting in appearance of new absorption peaks in the UV-Vis spectra and color changes of the sensor solution upon addition of the Cu2+and Fe3+.
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Patrício, Aline Cadigena Lima, Marcílio Máximo da Silva, Anna Karoline Freires de Sousa, Mariaugusta Ferreira Mota, and Meiry Glaúcia Freire Rodrigues. "SEM, XRF, XRD, Nitrogen Adsorption, Fosters Swelling and Capacity Adsorption Characterization of Cloisite 30 B." Materials Science Forum 727-728 (August 2012): 1591–95. http://dx.doi.org/10.4028/www.scientific.net/msf.727-728.1591.
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Cationic surfactants, such as quaternary ammonium cations, have been used, in order to ameliorate the oil sorption capacity of inorganics materials, such as clays. Clays modified with quaternary ammonium cations (organoclays) have better performance in sorption, remove oil and grease from water at seven times the rate of activated carbon, as well as they can be used like perforation fluids of oil wells to the oil base, lubricants, among others industries. This work aims characterize the Cloisite 30B using various techniques: X-Ray Diffraction (XRD), Specific Surface Area (BET) and Cation Exchange Capacity. Different organic solvents, namely gasoline, diesel and kerosene were used in order to investigate the clays compatibility after orgophilization.
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Yoder, C. H., N. T. Landes, L. K. Tran, A. K. Smith, and J. D. Pasteris. "The relative stabilities of A- and B-type carbonate substitution in apatites synthesized in aqueous solution." Mineralogical Magazine 80, no. 6 (October 2016): 977–83. http://dx.doi.org/10.1180/minmag.2016.080.035.
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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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Seo, Ji Hae, Namgyu Kim, Munsik Park, Sunkyung Lee, Seungjae Yeon, and Donghee Park. "Evaluation of metal removal performance of rod-type biosorbent prepared from sewage-sludge." Environmental Engineering Research 25, no. 5 (October 11, 2019): 700–706. http://dx.doi.org/10.4491/eer.2019.201.
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The aim of this work was to evaluate the potential use of recycled sewage-sludge as a biosorbent for removing various metals from aqueous solution. To improve adsorption capacity and accomplish easy solid-liquid separation, the sludge was immobilized into the rod type with Ca-alginate. The removal performance was analyzed through kinetic and equilibrium studies. We conducted batch experiments examining the removal of cationic metals and anionic metals/metalloid by the rod-type biosorbent (cations: Cd(II), Cu(II), Cr(III), Fe(II), Ni(II), Pb(II), Zn(II), Mn(II), Al(III), As(III), and Fe(III); anions: As(V), Cr(VI) and Mn(VII)).The rod-type biosorbent, which was manufactured using sludge and alginate, showed higher adsorption capability for the removal of cationic metal than anionic metal. In evaluations of cation adsorption, divalent cations adsorbed more and faster than trivalent cations. The maximum uptake of Cd(II) was determined to be 67.29 mg/g, which was higher than those of other sludge adsorbents reported in the literature. In evaluations of anions, As(V), Cr(VI) and Mn(VII) were removed by different mechanisms. In this study, we simultaneously evaluated the adsorption performance of a new biosorbent for cationic and anionic metals. Our findings are expected to contribute to the commercialization of sludge-based biosorbents.
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Khanna, PK, B. Ludwig, and RJ Raison. "Comparing modelled and observed effects of ash additions on chemistry of a highly acid soil." Soil Research 34, no. 6 (1996): 999. http://dx.doi.org/10.1071/sr9960999.
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The chemical composition of soil solutions (field percolates collected in situ and laboratory saturation extracts) and the amount of salt-extractable cations were measured at several microsites (unburnt, moderately burnt, and intensely burnt ashbeds) after a fuel reduction burning in a subalpine Eucalyptus pauciflora forest. Soil samples were collected 1, 58, 375, 745, and 1095 days after the fire, and soil percolates were obtained on 17 occasions during the initial year. A model of coupled equilibria, which includes insoluble salts, multiple cation exchange, and inorganic complexation, was used to describe soil chemical changes after fire and ash addition. The model was able to describe temporal changes in cation concentrations of held percolates and soil exchangeable cations. Measurements of extractable cations using unbuffered salt solution on samples taken immediately after fire suggest immediate changes in exchangeable cations which were related to solubilisation of cations from ash, and not to changes in exchangeable cations in soils. Modelling suggests that under natural conditions the differences in solubility of cations in ash result in slow changes in exchangeable cations extending over a period of 6 years or more. The time required to reacidify the surface layer of ashbed soil was estimated to be 45 years when annual acid input was 0.5 kmol H+/ha.
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Tucker, BM. "Active and exchangeable cations in soils." Soil Research 23, no. 2 (1985): 195. http://dx.doi.org/10.1071/sr9850195.
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The amounts of cations, Ca, Mg, K and Na, that could be extracted from soils by salt solutions varied with the cations, anions, acidity or alkalinity, and solvent of the extracting reagent. The variations were largest for soils that contained organic matter as the main source of those cations, and smallest in clay soils with little organic content. Calcium was the cation most affected and sodium the least affected. It appeared that the extractants removed all diffuse double-layer exchangeable cations, and variable portions of the other active cations including inner-sphere cations, specifically adsorbed cations, and those chelated by organic materials. A moderate, non-specific extractant containing a quaternary ammonium salt, choline chloride, is recommended for the displacement of exchangeable cations with a minimum contribution from other active cations. For an estimate of all forms of active cations, e.g. for soil nutrient assessment, a solution of ammonium sulfate is suggested.
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Chantrapromma, Suchada, Boonwasana Jindawong, Hoong-Kun Fun, P. S. Patil, and Chatchanok Karalai. "2-[(E)-2-(3-Hydroxy-4-methoxyphenyl)ethenyl]-1-methylquinolinium 4-chlorobenzenesulfonate." Acta Crystallographica Section E Structure Reports Online 62, no. 5 (April 11, 2006): o1802—o1804. http://dx.doi.org/10.1107/s1600536806012347.
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The title compound, C19H18NO2 +·C6H4ClO3S−, exhibits non-linear optical properties. The cation is almost planar and the benzene ring of the anion makes dihedral angles of 48.97 (6) and 51.63 (7)° with the mean planes through the quinolinium system and the benzene ring of the cation, respectively. The anions are linked by C—H...O interactions, forming a chain along the a axis, while the cations are stacked along the a axis. The anionic chains and the cationic stacks are alternately arranged.
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Schustereit, Tanja, Thomas Schleid, and Ingo Hartenbach. "The defect scheelite-type lanthanum(III)ortho-oxidomolybdate(VI) La0.667[MoO4]." Acta Crystallographica Section E Structure Reports Online 69, no. 2 (January 16, 2013): i7. http://dx.doi.org/10.1107/s1600536813000731.
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In scheelite-type La0.667[MoO4], one crystallographically unique position with site symmetry -4.. and an occupancy of 2/3 is found for the La3+cation. The cation is surrounded by eight O atoms in the shape of a trigonal dodecahedron. The structure also contains one [MoO4]2−anion (site symmetry -4..), which is surrounded by eight vertex-attached La3+cations. The polyhedra around the La3+cations are interconnectedviacommon edges, building up a three-dimensional network, in the tetrahedral voids of which the Mo6+cations reside.
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Choi, In, Ho Kim, Seung Wi, Ho Chun, In Hwang, Hak-Jong Choi, and Hae Park. "Effect of Cation Influx on the Viability of Freeze-Dried Lactobacillus brevis WiKim0069." Applied Sciences 8, no. 11 (November 8, 2018): 2189. http://dx.doi.org/10.3390/app8112189.
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Extension of the storage stability of freeze-dried lactic acid bacteria is important for industrialization. In this study, the effect of cation influx from soy powder, which contains high amounts of cations, as a cryoprotective agent on the viability of freeze-dried Lactobacillus brevis WiKim0069 was tested. Compared to that in the absence of the soy powder, bacterial viability was significantly higher in the presence of soy powder. Approximately 4.7% of L. brevis WiKim0069 survived in the absence of the protective agent, whereas 92.8% viability was observed in the presence of soy powder. However, when cations were removed from the soy powder by using ethylenediaminetetraacetic acid (EDTA) and a cationic resin filter, the viability of L. brevis WiKim0069 decreased to 22.9–24.7%. When the soy powder was treated with ethylene glycol tetraacetic acid, the viability was higher than when it was pretreated with EDTA and a cationic resin filter, suggesting that Mg2+ had a role in enhancing the viability of L. brevis WiKim0069. Cold adaptation at 10 °C prior to freeze-drying had a positive effect on the storage stability of freeze-dried L. brevis WiKim0069, with 60.6% viability after 56 days of storage. A decrease in the fluorescence polarization value indicated an increase in membrane fluidity, which regulates the activity of ion channels present in the cell membrane. Cold adaptation caused activation of the cation channels, resulting in increased intracellular influx of cations, i.e., Ca2+ and Mg2+. These results suggest that cold adaptation can be used to improve the storage stability of L. brevis WiKim0069.
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Krebs, Frederik C., Bo W. Laursen, Ib Johannsen, André Faldt, Klaus Bechgaard, Claus S. Jacobsen, Niels Thorup, and Kamal Boubekeur. "The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state. Structures of a planar organic cation with various monovalent and divalent anions." Acta Crystallographica Section B Structural Science 55, no. 3 (June 1, 1999): 410–23. http://dx.doi.org/10.1107/s0108768198016140.
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The geometry of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state was established by X-ray structural resolution of the salts formed between the cation and various anions. The geometry was found to be planar for the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium and 2,6,10-tri(tert-butyl)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium cations with the monovalent anions I−, BF_4^-, PF_6^-, AsF_6^-, HNO3.NO_3^- and CF3SO_3^-, and the divalent anions S2O_6^{2-} and Mo6Cl_{14}^{2-}. The salts were found to crystallize in distinct space groups following a characteristic pattern. Mixed cation–anion stacking resulted in space groups with high symmetry: Pbca in three cases and R3¯c in one; a temperature study of the latter was made at ten different temperatures. The formation of dimers of anions and cations resulted in lower-symmetry space groups, mainly monoclinic (P21/n, P21/c and C2/c), but also P1¯.
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ZHU, Zhenyu, and L. Victor DAVIDSON. "Kinetic and chemical mechanisms for the effects of univalent cations on the spectral properties of aromatic amine dehydrogenase." Biochemical Journal 329, no. 1 (January 1, 1998): 175–82. http://dx.doi.org/10.1042/bj3290175.
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Univalent cations and pH influence the UV-visible absorption spectrum of the tryptophan tryptophylquinone (TTQ) enzyme, aromatic amine dehydrogenase (AADH). Little spectral perturbation was observed when pH was varied in the absence of univalent cations. The addition of alkali metal univalent cations (K+, Na+, Li+, Rb+ or Cs+) to oxidized AADH caused significant changes in its absorption spectrum. The apparent Kd for each cation, determined from titrations of the spectral perturbation, decreased with increasing pH. Transient kinetic studies involving rapid mixing of AADH with cations and pH jump revealed that the rate of the cation-induced spectral changes initially decreased with increasing cation concentration to a minimum value, then increased with increasing cation concentration. A kinetic model was developed to fit these data, determine the true pH-independent Kd values for K+ and Na+, and explain the pH-dependence of the apparent Kd. A chemical reaction mechanism, based on the kinetic data, is presented in which the metallic univalent cation facilitates the chemical modification of the TTQ prosthetic group to form an hydroxide adduct which gives rise to the spectral change. Addition of NH4+/NH3 to AADH caused changes in the absorption spectrum which were very different form those caused by addition of the metallic univalent cations. The kinetics of the reaction induced by addition of NH4+/NH3 were also different, being simple saturation kinetics. Another reaction mechanism is proposed for the NH4+/NH3-induced spectral change that involves nucleophilic addition of the unprotonated NH3 to TTQ. The general relevance of these data and models to the physiological reactions of TTQ-dependent enzymes and to the roles of univalent cations in modulating enzyme activity are discussed.
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Srivastava, Ashutosh, Madhubanti Mukherjee, and Abhishek Kumar Singh. "Decoupled atomic contribution boosted high thermoelectric performance in mixed cation spinel oxides ACo2O4." Applied Physics Letters 120, no. 24 (June 13, 2022): 243901. http://dx.doi.org/10.1063/5.0099452.
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Decoupling the interdependence of various transport parameters in materials has been an intractable challenge in designing efficient thermoelectric materials. Using the first-principles density functional theory and the semi-classical Boltzmann transport theory, we demonstrate that the crucial criteria of obtaining suitable electronic and thermal transport have been achieved by utilizing the presence of mixed cations in spinel oxides. Differently coordinated cations present in spinel oxides lead to decoupled cationic contribution to the electronic and thermal transport properties. While electronic transport properties are controlled by tetrahedrally coordinated cation B (Co), the octahedrally coordinated cations A (Zn/Cd) only contribute to the thermal transport of the system. The combination of heavy bands in the electronic dispersions and tetrahedrally coordinated environment of Co results into an enhanced power factor. Additionally, the substitution of Cd leads to one order of magnitude reduction in the lattice thermal conductivity ( κl) without affecting the electronic transport properties. The significant reduction in κl has been attributed to the large mass difference, and remarkably strong anharmonic phonon scattering introduced by Cd. Simultaneously achieved high power factor and low lattice thermal conductivity result in a maximum figure of merit of 1.68 in CdCo2O4 spinel oxide. The approach of decoupling atomic contributions utilizing various cationic sites demonstrates a potential route to enhance thermoelectric performance.
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Maqueda, C., and E. Morillo. "Sorption of chlormequat on montmorillonite as affected by dissolved copper. Influence of background electrolytes." Clay Minerals 36, no. 4 (December 2001): 473–81. http://dx.doi.org/10.1180/0009855013640002.
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AbstractIn this paper, the role of Cu in the adsorption of the cationic pesticide chlormequat (CCC) on montmorillonite is studied. The adsorption of CCC was measured in various media, e.g. water and aqueous solutions of NaCl, CaCl2 and Ca(NO3)2 at the same ionic strength (I= 0.01 mol l–1). The retention of CCC on montmorillonite in aqueous media is due principally to a cationic exchange process with inorganic cations which saturate the interlamellar positions on this mineral. However, the amount of inorganic cations liberated from montmorillonite was ∼15% less than the amount of CCC adsorbed. This indicates that not all the pesticide was adsorbed through cation exchange.The adsorption of CCC in aqueous media decreased in the presence of a heavy metal, compared with metal-free treatment. This behaviour indicates competition between the two cations for interlamellar positions. The adsorption of CCC in the presence of Cu also decreased in electrolyte media with the effect being highest in the presence of Ca electrolytes. The maximum CCC diminution was ∼30%. However, the isotherms derived in CaCl2 and Ca(NO3)2 media at different Cu concentrations were close to each other, indicating that Ca from background electrolyte exerts greater competition than Cu for montmorillonite planar positions.
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Ishimaru, Shin’ichi, Miho Yamauchi, and Ryuichi Ikeda. "Dynamics of Interlayer Cations in Tetramethylammonium-Saponite Studied by 1H, 2H NMR, and Electrical Conductivity Measurements." Zeitschrift für Naturforschung A 53, no. 10-11 (November 1, 1998): 903–8. http://dx.doi.org/10.1515/zna-1998-10-1116.
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Abstract We observed 1H and 2H NMR spectra, 1H NMR spin-lattice relaxation times, and electrical con-ductivities of water-saturated and anhydrous tetramethylammonium(TMA)-saponites between 100 and 415 K. The very weakly bound cations produced narrow 1H and 2H NMR lines observed in both specimens down to 150 K. The temperature dependence of the 'H NMR spin-lattice relaxation times in the water-saturated and anhydrous samples gave asymmetric minima attributable to the heteroge-neous overall rotation and self-diffusion of the cations. The inhomogeneity of the cationic motions in the anhydrous TMA-saponite was greater than in the water-saturated one. From measurements of the electrical conductivity of anhydrous TMA-saponite a large anisotropic cation-diffusivity was concluded.
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Stoyanov, Evgenii S., and Irina V. Stoyanova. "The Chloronium Cation [(C2H3)2Cl+] and Unsaturated C4-Carbocations with C=C and C≡C Bonds in Their Solid Salts and in Solutions: An H1/C13 NMR and Infrared Spectroscopic Study." International Journal of Molecular Sciences 23, no. 16 (August 14, 2022): 9111. http://dx.doi.org/10.3390/ijms23169111.
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Solid salts of the divinyl chloronium (C2H3)2Cl+ cation (I) and unsaturated C4H6Cl+ and C4H7+ carbocations with the highly stable CHB11Hal11− anion (Hal=F, Cl) were obtained for the first time. At 120 °C, the salt of the chloronium cation decomposes, yielding a salt of the C4H5+ cation. This thermally stable (up to 200 °C) carbocation is methyl propargyl, CH≡C-C+-H-CH3 (VI), which, according to quantum chemical calculations, should be energetically much less favorable than other isomers of the C4H7+ cations. Cation VI readily attaches HCl to the formal triple C≡C bond to form the CHCl=CH-C+H-CH3 cation (VII). In infrared spectra of cations I, VI, and VII, frequencies of C=C and C≡C stretches are significantly lower than those predicted by calculations (by 400–500 cm−1). Infrared and 1H/13C magic-angle spinning NMR spectra of solid salts of cations I and VI and high-resolution 1H/13C NMR spectra of VII in solution in SO2ClF were interpreted. On the basis of the spectroscopic data, the charge and electron density distribution in the cations are discussed.
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Büchler, P. M. "The Effect of Exchangeable Cations on the Permeability of a Bentonite to Be Used in a Stabilization Pond Liner." Water Science and Technology 22, no. 6 (June 1, 1990): 23–26. http://dx.doi.org/10.2166/wst.1990.0047.
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The organophilic nature of bentonites exchanged with quaternary ammonium cations is used in sanitary engineering for the adsorption of organic pollutants. This paper deals with five different quaternary ammonium cations: tetramethylammonium, trimethylstearylammonium (C18), dimethylbenzyllaurylammonium (C12), trimethylpalmitylammonium (C16) and dimethyldistearylammonium. A Brazilian bentonite was treated with the above cations and the adsorption of vinasse organics was measured through the total organic carbon present in solution. The results show that tetramethylammonium cation is the most effective of those tested to make sodium bentonite more organophilic and the behaviour follows a Freundlich isotherm. If the isotherms are plotted in milliequivalents of the cation over the weight of the sodium bentonite the present experiments did not show an appreciable difference in the quantity adsorbed. Therefore, if cost is a determining factor, low molecular weight cations should be chosen. The modified bentonites were characterized by the X-ray diffraction patterns. For high molecular weight cations the interlamelar spacing is close to 18 Å but for tetramethylammonium it is 13.5 Å. In any case the replacement of sodium by a quaternary ammonium cation increases the capacity of the clay to adsorb organic molecules.
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Drits, V. A., L. G. Dainyak, F. Muller, G. Besson, and A. Manceau. "Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mössbauer and EXAFS spectroscopies." Clay Minerals 32, no. 2 (June 1997): 153–79. http://dx.doi.org/10.1180/claymin.1997.032.2.01.
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AbstractCeladonite, glauconite and Fe-illite samples were studied by XRD, EXAFS, IR and Mössbauer spectroscopy. The samples were monomineralic and corresponded to 1M polytype. In the OH-stretching region of the IR spectra the content of each definite pair of cations bonded to OH groups was determined. The number of heavy (Fe) and light (Al, Mg) octahedral cations nearest to Fe was found by the EXAFS technique. The predicted quadrupole splitting values for each definite arrangement of cations nearest to Fe3+ were used to interpret the Mössbauer spectra. After the fitting procedure, the intensity of each doublet corresponded to a definite set of local cation arrangements around Fe3+ and to a definite occurrence probability of these arrangements. Computer simulation and the experimental data obtained were used to reconstruct the distribution of isomorphous octahedral cations in the 2:1 layers. For all samples, R2+ cations prefer to occupy one of the two symmetrically independent cis-sites and R2+-R2+ and/or Al-Fe3+ were prohibited in the directions forming ± 120° with the b axis. Therefore, octahedral sheets of the samples revealed domain structure, in which domains differ in size, in the nature of predominant cation and/or by cation ordering.
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Carotenuto, Gianfranco. "Electrical Investigation of the Mechanism of Water Adsorption/Desorption by Natural Clinoptilolite Desiccant Used in Food Preservation." Materials Proceedings 2, no. 1 (April 21, 2020): 15. http://dx.doi.org/10.3390/ciwc2020-06800.
Full textAbstract:
Powdered zeolites are used as a desiccant in the preservation of many types of vegetable foods (e.g., cereal grain, corn, etc.). Natural clinoptilolite is a very abundant, inexpensive, nontoxic, regenerable, and environmentally friendly zeolite with good desiccant properties. Here, water adsorption/desorption properties of natural clinoptilolite have been investigated by a novel technique based on a.c. electrical measurements. In particular, owing to the presence of extra-framework cations, zeolites are ionic conductors. The presence of water in cationic sites significantly modifies cation mobility, because strong electrostatic interactions act between cations and nucleophilic areas in 3D-frameworks, and non-hydrated cations have a near zero mobility, while hydrated cations have enough mobility at room temperature. The type of law controlling the adsorption/desorption process has been established by monitoring the real-time behavior of relative current intensity moving in the sample surface biased by a sinusoidal voltage signal of 20Vpp (5 kHz) and exposed to a constant moisture atmosphere (75%) at 25 °C. An intergranular diffusion control was active at the beginning of hydration because of the lamellar texture, then Lagergren irreversible pseudo-first-order kinetics took place. To confirm the adsorption mechanism and possibility of regenerating the clinoptilolite desiccant, dehydration by silica gel was electrically monitored and an exponential kinetic law found.
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Nana Osipova, Tamar Kvernadze, Nino Burkiashvili, Leila Japaridze, Tsiala Gabelia, and Eter Salukvadze. "Some molecular-sieve peculiarities of natural zeolite of Georgia." World Journal of Advanced Research and Reviews 17, no. 3 (March 30, 2023): 514–19. http://dx.doi.org/10.30574/wjarr.2023.17.3.0388.
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Ion exchange property of fibrous zeolite scolecite of Georgian origin has been studied against mono (Li, Na, NH4, K Cs and Rb), divalent (Sr, Ba Ca, Mg) and transition (Cd, Cu, Mn, Zn, Co and Ni) metal cations. Selectivity series of the above cations for scolecite have been compiled. The structure of scolecite, charge and sizeof the cations (both in hydrated and dehydrated state) and cation concentration in the solution (0.1N, 0.3N, 0.5N 1.0N and 1.5N) greatly influence on the ion-exchange property and selectivity order of scolecite. Dynamic Exchange Capacity (DEC) values for the studied cations on scolecite have been calculated. Kinetics of ion exchange in dynamic conditions for the above cations has been studied. Analysis of the obtained data shows that the external diffusion processes have influence on the establishment of equilibrium between the ions on the surface and in the micro porous structure of scolesite. The time of dynamic exchange equilibrium is directly proportional to the cation radios.
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Schramm, Laurier L., Shmuel Yariv, Dipak K. Ghosh, and Loren G. Hepler. "Electrokinetic study of the adsorption of ethyl violet and crystal violet by montmorillonite clay particles." Canadian Journal of Chemistry 75, no. 12 (December 1, 1997): 1868–77. http://dx.doi.org/10.1139/v97-620.
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Electrophoretic mobilities of mixtures of a montmorillonite clay (in different exchangeable metal cation forms) and increasing amounts of two cationic dyes (ethyl violet and crystal violet) were measured. Electrophoretic mobilities were found to vary between −60 × 10−5 and +40 × 10−5 cm2 s−1 V−1. For both the dyes, the degree of saturation at which the isoelectric point (IEP) occurs, decreases with increasing valency of the metal cations. An effort was made to connect the IEP, maximum flocculation, and dye adsorption parameters. An important adsorption parameter is the transition saturation (TS), the saturation beyond which adsorption by organophilic attractions occurs in addition to adsorption by electrical and (or) π-interactions. It was found that maximum flocculation occurs before the IEP for all the exchangeable cations tested, but the IEP is reached at similar saturations to the TS for most of the cations. These results have been interpreted in terms of different types of adsorption phenomena and particle associations. Keywords: clay, adsorption, dye, ion exchange, electrokinetic charge.
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Malkani, A. S., J. Li, N. J. Oliveira, M. He, X. Chang, B. Xu, and Q. Lu. "Understanding the electric and nonelectric field components of the cation effect on the electrochemical CO reduction reaction." Science Advances 6, no. 45 (November 2020): eabd2569. http://dx.doi.org/10.1126/sciadv.abd2569.
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Electrolyte cations affect the activity of surface-mediated electrocatalytic reactions; however, understanding the modes of interaction between cations and reaction intermediates remains lacking. We show that larger alkali metal cations (excluding the thickness of the hydration shell) promote the electrochemical CO reduction reaction on polycrystalline Cu surfaces in alkaline electrolytes. Combined reactivity and in situ surface-enhanced spectroscopic investigations show that changes to the interfacial electric field strength cannot solely explain the reactivity trend with cation size, suggesting the presence of a nonelectric field strength component in the cation effect. Spectroscopic investigations with cation chelating agents and organic molecules show that the electric and nonelectric field components of the cation effect could be affected by both cation identity and composition of the electrochemical interface. The interdependent nature of interfacial species indicates that the cation effect should be considered an integral part of the broader effect of composition and structure of the electrochemical interface on electrode-mediated reactions.
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Yin, Wen-Yu, Yi-Gang Weng, Zhou-Hong Ren, Zhi-Ruo Zhang, Qin-Yu Zhu, and Jie Dai. "Tetrathiafulvalene-based double metal lead iodides: structures and electrical properties." Dalton Transactions 50, no. 23 (2021): 8120–26. http://dx.doi.org/10.1039/d1dt00631b.
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The conductive and photoconductive properties of hybrid lead–cuprous double metal iodides with tetrathiafulvalene cations are affected by the anion–cation electron donating effect and the electronic state of the TTF cations.
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Lindsay, A. R., A. Tinker, and A. J. Williams. "How does ryanodine modify ion handling in the sheep cardiac sarcoplasmic reticulum Ca(2+)-release channel?" Journal of General Physiology 104, no. 3 (September 1, 1994): 425–47. http://dx.doi.org/10.1085/jgp.104.3.425.
Full textAbstract:
Under appropriate conditions, the interaction of the plant alkaloid ryanodine with a single cardiac sarcoplasmic reticulum Ca(2+)-release channel results in a profound modification of both channel gating and conduction. On modification, the channel undergoes a dramatic increase in open probability and a change in single-channel conductance. In this paper we aim to provide a mechanistic framework for the interpretation of the altered conductance seen after ryanodine binding to the channel protein. To do this we have characterized single-channel conductance with representative members of three classes of permeant cation; group 1a monovalent cations, alkaline earth divalent cations, and organic monovalent cations. We have quantified the change in single-channel conductance induced by ryanodine and have expressed this as a fraction of conductance in the absence of ryanodine. Fractional conductance seen in symmetrical 210 mM solutions is not fixed but varies with the nature of the permeant cation. The group 1a monovalent cations (K+, Na+, Cs+, Li+) have values of fractional conductance in a narrow range (0.60-0.66). With divalent cations fractional conductance is considerably lower (Ba2+, 0.22 and Sr2+, 0.28), whereas values of fractional conductance vary considerably with the organic monovalent cations (ammonia 0.66, ethylamine 0.76, propanolamine 0.65, diethanolamine 0.92, diethylamine 1.2). To establish the mechanisms governing these differences, we have monitored the affinity of the conduction pathway for, and the relative permeability of, representative cations in the ryanodine-modified channel. These parameters have been compared with those obtained in previous studies from this laboratory using the channel in the absence of ryanodine and have been modeled by modifying our existing single-ion, four-barrier three-well rate theory model of conduction in the unmodified channel. Our findings indicate that the high affinity, essentially irreversible, interaction of ryanodine with the cardiac sarcoplasmic reticulum Ca(2+)-release channel produces a conformational alteration of the protein which results in modified ion handling. We suggest that, on modification, the affinity of the channel for the group 1a monovalent cations is increased while the relative permeability of this class of cations remains essentially unaltered. The affinity of the conduction pathway for the alkaline earth divalent cations is also increased, however the relative permeability of this class of cations is reduced compared to the unmodified channel. The influence of modification on the handling by the channel of the organic monovalent cations is determined by both the size and the nature of the cation.(ABSTRACT TRUNCATED AT 400 WORDS)