Ionic Composition Of Solution Research Articles

Secondary minerals of Fe, Pb, Cu in sulfide-containing tailings: sequence of formation, electrochemical reactions and physico-chemical model (Talmovskie Sands, Salaire, Russia)

The results of studies of the composition and form of secondary minerals Fe, Pb, Cu, formed under contrasting physico-chemical conditions of the accumulated tailings from the enrichment of barite-polymetallic ores of the Salair ore field, are presented. The complex mineral composition of ores (pyrite, chalcopyrite, sphalerite, galena, fahlore) and long-term processes of chemical weathering of the substance contributed to the formation of monomineral and zonal secondary rims and fillings of the intergranular space, which were identified using modern research methods. Plumbojarosite, anglesite, cerussite, and iron hydroxides predominate among them; pyromorphite, ginsdalite, and covellite occur less frequently. The method of thermodynamic modeling was used to solve the inverse problem - the restoration of the composition of solutions that led to a change in the associations of secondary minerals. The nature of the ongoing processes can be characterized not only by chemical interactions, but also by electrochemical reactions in the systems under consideration, where various mineral components act as galvanic pairs, which, in combination with the physico-chemical parameters of the medium (pH, Eh, ionic composition of solutions ), leads to stepwise or incomplete oxidation of the original minerals with subsequent selective deposition of secondary compounds.

T76. INVESTIGATION OF NAV1.1 POSITIVE MODULATOR EFFECTS ON FAST SPIKING INTERNEURONS IN SOMATOSENSORY CORTEX SLICES

BackgroundGABAergic inhibition is essential for normal cortical function as it serves the purpose of proper excitation/inhibition (E/I) balance in many circuits. In contrast, inappropriate interneuron signaling leads to E/I imbalance, reduced gamma oscillations in EEG measurements and has serious behavioural consequences. Among the heterogeneous group of GABAergic cells, fast-spiking, parvalbumin positive interneurons (FS-PV+) play a key role in the generation and maintenance of gamma oscillations. E/I imbalance due to interneuron dysfunction has been implicated in the pathophysiology of various psychiatric disorders.Cognitive impairment has been associated with altered gamma oscillation in schizophrenia and there is accumulating evidence for involvement of FS-PV+ interneuron deficit in the disease. Hypofunction of FS-PV+ neurons leads to disinhibition of pyramidal cells which cause network desynchronization. Therefore, it is hypothesized that activation of these neurons could restore high-frequency oscillations and consequently improve cognitive functions. However selective modulation of different interneuron types is still challenging due to limited number of known cell type specific targets.MethodsA possible starting point for the treatment could be pharmacological activation of voltage gated sodium channels (Nav) which have a pivotal role in action potential initiation. Of the four subtypes of Nav channels expressed in the CNS Nav 1.1 comprises the majority of the sodium current in FS-PV+ but not in pyramidal neurons. Based on this we looked for selective Nav 1.1 activators and found a recently published promising compound (Compound 3a, see Crestey et al, 2015) which has been shown to increase the electrical activity of FS-PV+ interneurons in the CA1 area of the hippocampus. However, the dysfunction in information processing found in schizophrenic patients is not only restricted to the hippocampus and high-order association cortices but also influences the sensory cortex. Thus, our aim was to explore the effect of the selective Nav 1.1 positive modulator Compound 3a on FS interneurons in the mouse somatosensory cortex. We performed whole-cell patch clamp recordings from mouse cortical brain slices and recorded the electrical activity of single FS cells before and after the drug application.ResultsSurprisingly the excitatory effect of the compound 3a could only partly be confirmed in the way that positive modulation of Nav1.1 in terms of action potential number and threshold only takes place under particular conditions, i.e. at physiological temperature and under specific ion compositions of the recording solutionsDiscussionThe discrepancy of our results from published data might be attributed to the different experimental conditions such as recording temperature and ionic composition of solutions and highlight the importance of selecting near physiological conditions during brain slice patch clamp experiments.

Evaluation of Technogenous Processes Proceeding in Tailing Dump of the Central Concentrating Mill of Dal’Negorsk District and their Effect on the Hydrosphere with Method of Physicochemical Modeling

Modeling allowed us to show Eh-pH parameters of the technogenic mineral formation in the mining-industrial technogenic system of polymetallic ores of Dal’negorsk district, to study the process of the hypergene mineral crystallization from solutions, to consider the qualitative and quantitative ionic composition of solutions, to show the role of hypergenesis in the contamination of surface and ground waters of the area. The aim of this work is to estimate the action of the CCM tailing oxidation on the hydrosphere of the district using the method of physicochemical modeling. The results obtained testify to a significant evacuation of a wide range of elements of sulfide ores (Zn, Pb, Cu, As, S) and enclosing rocks (Si, Al, Mg, Ca, K, Na) from the CCM tailing dumps into the surface waters polluting the hydrosphere with them.

Reversible Electrochemical Switching of Polymer Brushes Grafted onto Conducting Polymer Films

We demonstrate the electrochemical switching of conformation of surface-bound polymer brushes, by grafting environmentally sensitive polymer brushes from an electrochemically active conducting polymer (ECP). Using atom transfer radical polymerization (ATRP), we grafted zwitterionic betaine homopolymer and block copolymer brushes of poly(3-(methacryloylamido)propyl)-N,N'-dimethyl(3-sulfopropyl)ammonium hydroxide) (PMPDSAH) and poly(methyl methacrylate)-b-PMPDSAH, from an initiator, surface-coupled to a poly(pyrrole-co-pyrrolyl butyric acid) film. The changes in ionic solution composition in the surface layer, resulting from oxidation and reduction of the ECP, trigger a switch in conformation of the surface-bound polymer brushes, demonstrated here by electrochemical impedance spectroscopy (EIS) and in a change of wettability. The switch is dependent upon temperature in a way that is analogous to the temperature-dependent solubility and aggregation of similar betaine polymers in aqueous solution but has a quite different dependence on salt concentration in solution. The switch is fully reversible and reproducible. We interpret the switching behavior in terms of a transition to a "supercollapsed" state on the surface that is controlled by ions that balance the charge state of the ECP and are adsorbed to the opposite charges of the zwitterionic graft, close to the graft-ECP interface. The behavior is significantly modified by hydrophobic interactions of the block copolymer graft. We speculate that the synergistic combination of properties embodied in these "smart" materials may find applications in electrochemical control of surface wetting and in the interaction with biomolecules and living cells.

The pH and Mobile Phase Composition Effects Ochratoxin A Fluorescence at Liquid Chromatography

Changes in the fluorescence behavior of fungal toxic metabolite ochratoxin were studied. The influence of ratio aqueous/organic solvent, the ionic composition of solution, and pH were investigated. The chromatographic separation under conditions yielding the highest fluorescence intensity were tested and compared with results obtained under commonly used chromatographic methods. The developed method was applied on analysis of spiked and naturally contaminated cereal samples.

Salt-induced protein separation in an aqueous electrolyte solution

Liquid-liquid phase separations of aqueous ovalbumin and bovine serum albumin (BSA) solutions are reported experimentally for a wide range of solution conditions. The temperature-induced clouding of protein solutions, which signals the onset of liquid-liquid phase separation, provides a simple means of assessing the effect of solution conditions on the strength of protein interaction. Our results show that the effect of salts on protein interactions depends sensitively on the ionic composition of solution and the identities of both the cation and the anion of the added salts. The results are used to test and refine theoretical models for the interaction energy between macromolecules. A modified perturbed hard-sphere chain (MPHSC) model is employed to determine the interaction energy for solvation forces playing an important role in protein interactions and to predict the osmotic pressures of protein solutions.

Effect of ionic composition of solutions on the methanol reaction with adsorbed oxygen on smooth polycrystalline platinum electrodes: Transients of the open-circuit potential

Transients of the open-circuit potential observed in the reaction of methanol with oxygen (Oads) preliminarily adsorbed on smooth polycrystalline platinum (pcPt) are measured in 0.05 M HClO4, 0.5 M HClO4, 0.05 M H2SO4, 0.05 M H2SO4 + 0.45 M Na2SO4, and 0.05 M H2SO4 + 0.45 M Cs2SO4. It is shown that the solution pH has a weak effect on the transient characteristics (when the reversible hydrogen electrode potential scale is used). This confirms the chemical nature of rate-controlling stages in the reaction mechanism. The changes in the reaction rate, observed upon going from one electrolyte to another, are preferentially associated with the involvement of solution ions in the formation of activated surface complexes that include CH3OH, Oads, and supporting-electrolyte components.

Influence of the Electrolyte on Triton X-100 Adsorption on Fumed Silica

Fumed silica was used for adsorption of Triton X-100 from electrolyte solutions. Influence of such parameters as the kind of fumed silica and its pretreatment, pH, ionic strength and ionic composition of solution on the process of surfactant adsorption has been studied using differential capacity measurements at a controlled growth mercury drop electrode. The kinetics of Triton adsorption on silica have also been studied. It was found that under optimal conditions 0.1% of fumed silica removes completely 5 ppm of Triton X-100 in time shorter than 1 minute.

Physico-chemical aspects of the hydrothermal growth of GaPO4

Abstract The chemistry and selected physical properties of nutrient solutions based on the solvent H 3 PO 4 -H 2 O are analysed with respect to a better understanding and optimizing of the hydrothermal growth of GaPO 4 . Vapour pressures and the ionic composition of solutions with different H 3 PO 4 concentrations were determined. Putting together these data, crystal properties, solubility data and their temperature dependence, NMR investigations and results from light scattering experiments lead to the proposal that the growth solution largely contains colloidal GaPO 4 .

PH-Dependent kinetics of tuff dissolution

Despite the widespread use of commercial tuffs as growth substrates, their dissolution kinetics and the time variation of their solution compositions have not hitherto been investigated. To fill this gap in our knowledge, rates of ion release by two tuffs were measured as a function of pH in batch and in steady-solution-flow suspensions. Reaction kinetics was characterized by rapid H +/OH − consumption, and Si, Al, Ca, Mg, and P release during the first day. This was followed by a period in which H + consumption and ion release were linear functions of time for at least 720 h. On the basis of reaction stoichiometry and equilibrium calculations, rapid short-term H + consumption of the studied tuffs was related to cation exchange and rapid dissolution of fine particles of volcanic glass and hydroxyapatite (HA). The rate laws for long-term acid consumption were fractional-order with respect to H + concentration in the pH ranges 3.4–6.5 and 3.6–9.6, black and yellow tuffs, respectively. On the basis of proton-consumption rate data and ionic solution composition, long-term acid consumption was attributed to the dissolution of halloysite-like allophane in yellow tuff, volcanic glass in black tuff, and HA in both tuffs. Aluminum dissolution from black tuff under batch conditions at pH below 4 may create a toxic environment for plant roots.

Recombination dynamics at indium phosphide/liquid interfaces

The relaxation dynamics of photoexcited charge carriers at the interface between InP and several metal ion solutions has been studied using picosecond time-resolved photoluminescence and electrochemical techniques. The results show that for p-InP, the controlling recombination process follows the nonradiative Shockley-Read-Hall (SRH) mechanism, while on the other hand, radiative bulk recombination is the controlling process in n-type crystals. The surface recombination velocities (SRV) of both conductivity types were found to be strongly dependent (varying over the range of 500 to 2 [times] 10[sup 5] cm/s) on the ionic solution composition and concentration. The SRV of the etched n-InP surface is retained and remains low when it is in contact with nonoxidizing ions like Zn[sup 2+] or Cr[sup 3+]. On the other hand, for n-InP, the SRV increases sharply when the crystal is dipped into stronger oxidizing species like Ag[sup +] (SRV = 1.4 [times] 10[sup 5] cm/s) or Cu[sup 2+] (SRV = 3.4 [times] 10[sup 42] cm/s). The electrochemical measurements provided firm evidence for chemisorbed-induced surface states in the case of the more strongly oxidizing solutions. 32 refs., 14 figs., 1 tab.

Surface recombination velocity measurements of cadmium sulfide single crystals immersed in electrolytes. A picosecond photoluminescence study

The effect of solution composition and concentration on the luminescence decay profile is measured for CdS single crystals immersed in various aqueous solutions. The surface recombination velocity is strongly dependent on the ionic solution composition and concentration. The experimental data are explained in terms of the chemisorption of ions on the CdS surface

Observations of the preferential loss of major ions from melting snow and laboratory ice

Two types of laboratory experiments were undertaken to understand changes in the ionic composition of solutions from melting snows: (1) a set of field-laboratory experiments which involved partially melting recently collected snows and (2) experiments on the controlled melting of artificial ices of known composition. Sulphate and nitrate ions are preferentially lost with respect to chloride during the melting process so apparent elution sequence may be written SO 4 2− > NO 3 − > Cl −. Of the cations, sodium appears to be removed least readily giving an elution sequence Mg 2+ = K + > Na +. In the laboratory the differences in the efficiency of removal of ions from ice are small in the first stages of melting, but pronounced by the end of the melt. Sodium and chloride are expected to be proportionally enriched in residual leached snow packs. This is generally born out by field observations. The preferential loss of some ions is more evident in aged laboratory ice than in the freshly made ice. The changes in the ice and meltwater composition throughout the process of melting may be understood to arise from the mixing of two types of solutions: (i) an intergranular surficial brine with high solute concentration that occupies the ice grain boundaries and (ii) the meltwater from the ice grains.

The growth of Myriophyllum spicatum L. in relation to selected characteristics of sediment and solution

The growth of Myriophyllum spicatum L. was examined experimentally on a variety of sediments and in two ionically distinct solutions. The influence of solution on growth was greatest on sediments that provided optimum growth and least on sediments that retarded growth. In agreement with results of a related investigation involving another submersed macrophyte species, the growth of M. spicatum was relatively poor on highly organic sediments. The possibility that high-level accumulations of organic matter in sediments might be inhibitory to M. spicatum was substantiated in one experiment involving organic matter additions to sediment. In another experiment, the influence of ionic composition of solution on the growth of this species was demonstrated to involve differences in both exogenous calcium and dissolved inorganic carbon (DIC) concentrations. Through mechanisms similar to those investigated here, sediment and open water may interact in determining the growth of M. spicatum in natural systems. This interaction needs to be carefully considered in evaluating variations in the productivity and distribution of submersed macrophytes.