Electrolyte Exchange Research Articles

Sulfidation of a Cu submonolayer at the Au(1 1 1)/electrolyte interface – An in situ STM study

We describe the electrochemical preparation of an ultrathin copper sulfide film on Au(1 1 1) and its structural characterization by in situ STM. The first step, underpotential deposition of a Cu submonolayer from CuSO 4/H 2SO 4 solution, is followed by two electrolyte exchanges for (i) Cu-free (blank) H 2SO 4 solution and (ii) NaOH/Na 2S solution. The well-known (√3 × √3) R30° structure of the upd Cu layer is stable in the blank electrolyte for at least 2 h. After exposure to bisulfide, the Cu layer contracts and forms two-dimensional islands of two distinct ordered surface phases, i.e. a rectangular and, at higher potentials, a hexagonal phase, with Cu-free Au(1 1 1) regions between them, the latter exhibiting the characteristic (√3 × √3) R30°-S adlayer structure. Potential changes lead to a complex phase behaviour including HS − ⇆ S x oxidation/reduction and, at strongly anodic potentials, dissolution of the Cu adlayer.

Adsorption, oxidation and reduction of crotyl alcohol on platinum

Abstract The electrochemical reactivity of crotyl alcohol (CA) on Pt in acid media has been studied applying electrochemical methods combined with in situ Fourier transform IR spectroscopy (FTIRS) and on-line mass spectrometry (DEMS). Mass spectrometric cyclic voltammograms (MSCVs) and IR spectra, acquired with the alcohol in the solution, point out the formation of CO 2 and crotonaldehyde as oxidation products. On the other hand, spectra recorded during the electroreduction display negative features at 2964, 2934 and 2875 cm −1 , which are assigned to the CH 3 and CH 2 asymmetric stretchings and the CH 2 symmetric stretching, respectively. The intensity of these signals confirms that a massive hydrogenation process occurs at E V RHE with a strong production of hydrocarbons. Accordingly, several reduction compounds (2-butene, butane, propane, propene, ethane and methane) were detected by DEMS. The same products, with the exception of the aldehyde, were established from CA adsorbed species, isolated applying an electrolyte exchange procedure. A feature at 2020 cm −1 due to lineal adsorbed CO develops in the IR spectra. These results allow us to propose a general overview of the electrochemical reactions of CA at Pt.

Stability of carbon monoxide adsorbed on nanoparticle Pt and Pt/Ru electrodes in sulfuric acid media

Pt and Pt/Ru nanoparticle electrodes were used as substrates for studies of stability of chemisorbed CO and its interactions (exchange) with carbon monoxide and hydrogen gas admitted to sulfuric acid solution, which served as the supporting electrolyte for these measurements. The surface bound, radioactive CO was obtained after decomposition of 14C labeled methanol or formic acid from the same solution. The stability and/or exchange of the surface bound CO was examined after (i) the 14C CO containing electrolyte was replaced by the clean supporting electrolyte (to remove the CO solute from the bulk) and (ii) after hydrogen and, separately, non-radioactive CO was admitted to the cell. We found no displacement of adsorbed CO due to the exchange of electrolyte or introduction of hydrogen to the cell. However, non-radioactive CO rapidly displaced the adsorbed 14C CO on the surface leaving behind a monolayer of chemisorbed but non-radioactive CO. Both results were independent of the electrode potential applied and they neither dependent on the source of surface CO, that is, whether it was deposited from methanol or formic acid solutions.

Role of endogenous channels in red blood cells response to their exposure to the pore forming toxin Sticholysin II

Sticholysin II (St II) is a highly hemolytic cytolysin isolated from the sea anemone Stichodactyla heliantus. The toxin hemolytic action takes place through the formation of channels that provoke an electrolyte unbalance leading to osmotic shock. The lytic event must involve the exchange of electrolytes and the entrance of water, leading to red blood cell disruption. These processes can occur through St II pores and/or the endogenous red blood cells transporters. In order to evaluate the contribution of these channels to water, anion and cation transport, we have measured the hemolysis and K + efflux rates in the presence of several specific inhibitors. The results obtained in the presence of Hg, an AQP1 blocker, indicate that water transport through these channels is not essential for the occurrence of the lytic process induced by St II. The data also support a partial role of K + and anion transporters. In particular, they are compatible with a preferential K + efflux though the K +/Cl − co-transport as a response to the promoted swelling. Furthermore, they suggest that chloride influx, a process that can regulate both K + efflux and lysis, is partially mediated by the endogenous cell transporters, in particular, band-3 anion exchange system being relevant at early stages of the lytic process.

Effect of dronedarone on renal function in healthy subjects

Background/Aims Creatinine clearance (CL) is used to assess glomerular filtration rate (GFR). During the clinical development of dronedarone, a new antiarrhythmic agent, a 10–15% increase in serum creatinine was noticed, as also shown recently for amiodarone. This study aimed to assess dronedarone effects on renal function and tubular cations handling. Methods 12 healthy males were enrolled in a randomised, cross-over, placebo-controlled, double-blind study. They received 400mg dronedarone or placebo bid for 7 days. Baseline and on-treatment renal function tests were performed under strict standardization of intakes, by assessing creatinine, sinistrin, para-amino-hippurate (PAH) and N-methylnicotinamide (NMN) CLs, and electrolyte excretions. Results Dronedarone did not alter sinistrin CL compared to placebo, but decreased creatinine CL significantly (mean 138 to 119mL/min under dronedarone vs 142 to 149 under placebo; p=0.04) and NMN CL marginally (448 to 368 vs 435 to 431; p=0.06), while PAH CL and other renal parameters remained unaffected. Conclusion Dronedarone compared to placebo reduces renal creatinine and NMN CLs by about 17%, without evidence of a true effect on GFR, renal plasma flow or electrolyte exchanges. This suggests a specific inhibition of tubular organic cation transporters (OCT). A limited increase in serum creatinine is therefore expected under dronedarone treatment, but does not mean a decline in renal function. Clinical Pharmacology & Therapeutics (2005) 77, P10–P10; doi: 10.1016/j.clpt.2004.11.041

Influence of atomic ordering on the electrocatalytic activity of Pt–Co alloys in alkaline electrolyte and proton exchange membrane fuel cells

Carbon-supported Pt–Co alloy catalysts with Co contents of 10–50 wt% have been synthesized by reducing aqueous Co2+ ions with borohydride or precipitating as hydroxide in the presence of a commercially available carbon-supported Pt catalyst followed by heat treatment in a 90% Ar–10% H2 mixture at 900 °C for 1 h. X-Ray diffraction indicates the Pt–Co alloys thus obtained to have the ordered Pt3Co or PtCo type structures or the disordered Pt type structure depending on the Co content. High resolution transmission electron microscopy (HRTEM) studies also confirm the formation of ordered structures. Structural analysis of the products after annealing at various temperatures 500 ≤ T ≤ 900 °C for 1 h suggests the ordering to be maximized for an annealing temperature of around 650 °C. Evaluation of the Pt–Co/C alloy catalysts for oxygen reduction in half cells employing KOH as the electrolyte and in proton exchange membrane fuel cells indicates that the alloys with the ordered Pt3Co or PtCo type structures have higher catalytic activity with lower polarization losses and higher power densities than Pt or disordered Pt–Co alloys. With the ordered phases, the activity increases with the extent of ordering. The enhanced catalytic activity is explained based on optimal structural and electronic features consisting of optimum number of Pt and Co nearest neighbors, Pt–Pt distance, and d-electron density in Pt.

A novel dual thin-layer flow cell double-disk electrode design for kinetic studies on supported catalysts under controlled mass-transport conditions

We present a novel dual thin-layer flow cell double-disk electrode design, which due to its high collection efficiency in combination with a reasonable time resolution allows highly sensitive measurements of electro-active species generated during electrochemical reactions on the working electrode. Most important, it allows for rapid changes of the electrolyte during the measurements, which in combination with a thin-film electrode, where an inert glassy carbon substrate is covered by a thin film of carbon-supported noble metal catalyst, makes it particularly useful for kinetic studies on electrocatalytic fuel cell reactions under realistic conditions (continuous reaction, continuous electrolyte flow) and on realistic materials (supported catalysts). The performance of the set-up and its suitability for kinetic studies, in particular for transient experiments involving rapid electrolyte exchange, are demonstrated in potentiodynamic and transient potentiostatic measurements for the oxygen reduction reaction on carbon-supported Pt catalysts and, for comparison, on Pt-free Vulcan carbon supports.

Involvement of opioid peptides and arginine-vasopressin in the regulation of water-electrolyte exchange in the amoeba Amoeba proteus.

Involvement of opioid peptides and arginine-vasopressin in the regulation of water-electrolyte exchange in the amoeba Amoeba proteus.

Dependence of Plasmodium falciparum In Vitro Growth on the Cation Permeability of the Human Host Erythrocyte

Intraerythrocyte growth of the malaria parasite Plasmodium falciparum induces a Ca²⁺-permeable unselective cation conductance in the host cell membrane which is inhibited by ethylisopropylamiloride (EIPA) and is paralleled by an exchange of K⁺ by Na⁺ in the host cytosol. The present study has been performed to elucidate the functional significance of the electrolyte exchange. Whole-cell patch-clamp experiments confirmed the Ca²⁺ permeability and EIPA sensitivity of the Plasmodium falciparum induced cation channel. In further experiments, ring stage-synchronized parasites were grown in vitro for 48 h in different test media. Percentage of Plasmodium-infected and phosphatidylserine-exposing erythrocytes was measured with FACS analysis by staining with the DNA-dye Syto16 and annexin V, respectively. The increase of infected cells was not significantly affected by an 8 h replacement of NaCl in the culture medium with Na-gluconate but was significantly blunted by replacement of NaCl with KCl, NMDG-Cl or raffinose. Half maximal growth was observed at about 25 mM Na⁺. The increase of infected cells was further inhibited by EIPA (IC₅₀< 10 µM) and at low extracellular free Ca²⁺. Infected cells displayed significantly stronger annexin binding, an effect mimicked by exposure of noninfected erythrocytes to oxidative stress (1 mM t-butylhydroperoxide for 15 min) or to Ca²⁺ ionophore ionomycin (1 µM for 60 min). The observations indicate that parasite growth requires the entry of both, Na⁺ and Ca²⁺ cations into the host erythrocyte probably through the EIPA sensitive cation channel. Ca²⁺ entry further induces break-down of the phospholipid asymmetry in the host membrane.

“Cup-patch” Technique of Ileocystoplasty for Bladder Enlargement or Partial Substitution

THE IDEA of enlarging or replacing the urinary bladder with isolated segments of bowel is not new in urologic surgery. However, Scheele’s description (1923) of his “ring plastik” to enlarge the bladder was more or less forgotten until Couvelaire in 1950 initiated the present era of interest in bladder enlargement and partial substitution by isolated loops of ileum. Various types of ileocystoplasty have been tried and enthusiastically reported by European authors, viz., Cibert, Tasker, Pyrah, Annis, May and associates, Schwartz, Glaser, and Jacobs. Couvelaire’s review of the literature, from the time of Mikulicz in 1898, is the best summary of the literature to that time. In 1957, Quenu presented the most recent complete review. In the American literature, however, there are to date fewer articles concerning this useful operation. Shoemaker and co-workers described experimental and clinical studies in which they used isolated ileac loops, denuded of mucosa and turned inside out, to form seromuscular grafts for bladder and ureteral replacement. This procedure is said to obviate difficulty with mucus formation and electrolyte exchange. Shoemaker’s article with Marucci19 contains a review of the background literature to be found in American journals. Campbell recently described an equivocal success with Shoemaker’s technique, but the procedure has not yet found wide acceptance. Ferris has succinctly reported his success with a patch type of ileocystoplasty (similar to that described by Tasker) in 2 patients treated at the Mayo Clinic. Our own interest in this problem began in 1953 when animal experiments were initiated to study partial substitution of the bladder with isolated segments of both ileum and sigmoid colon in the dog.22 To date we have employed ileocystoplasty in 17 patients utilizing a more complex variant of the “patch” technique described by Tasker. The surgical procedures have been technically satisfactory. There has been 1 death from coronary thrombosis. There have been no serious complications related to the surgery. Late results of the procedure are to be described elsewhere. In the present article the technique is described in detail as we have used it.

???Cup-patch??? Technique of Ileocystoplasty for Bladder Enlargement or Partial Substitution

THE IDEA of enlarging or replacing the urinary bladder with isolated segments of bowel is not new in urologic surgery. However, Scheele’s description (1923) of his “ring plastik” to enlarge the bladder was more or less forgotten until Couvelaire in 1950 initiated the present era of interest in bladder enlargement and partial substitution by isolated loops of ileum. Various types of ileocystoplasty have been tried and enthusiastically reported by European authors, viz., Cibert, Tasker, Pyrah, Annis, May and associates, Schwartz, Glaser, and Jacobs. Couvelaire’s review of the literature, from the time of Mikulicz in 1898, is the best summary of the literature to that time. In 1957, Quenu presented the most recent complete review. In the American literature, however, there are to date fewer articles concerning this useful operation. Shoemaker and co-workers described experimental and clinical studies in which they used isolated ileac loops, denuded of mucosa and turned inside out, to form seromuscular grafts for bladder and ureteral replacement. This procedure is said to obviate difficulty with mucus formation and electrolyte exchange. Shoemaker’s article with Marucci19 contains a review of the background literature to be found in American journals. Campbell recently described an equivocal success with Shoemaker’s technique, but the procedure has not yet found wide acceptance. Ferris has succinctly reported his success with a patch type of ileocystoplasty (similar to that described by Tasker) in 2 patients treated at the Mayo Clinic. Our own interest in this problem began in 1953 when animal experiments were initiated to study partial substitution of the bladder with isolated segments of both ileum and sigmoid colon in the dog.22 To date we have employed ileocystoplasty in 17 patients utilizing a more complex variant of the “patch” technique described by Tasker. The surgical procedures have been technically satisfactory. There has been 1 death from coronary thrombosis. There have been no serious complications related to the surgery. Late results of the procedure are to be described elsewhere. In the present article the technique is described in detail as we have used it.

An enzyme histochemical and biochemical study of the activity of three oxidative enzymes in the developing rat parotid gland

Information on ductal differentiation in the developing rat parotid gland is sparse. One of the main functions of the striated and excretory ducts in this gland is the selective exchange of electrolytes from the primary fluid secreted by the acini. These ducts are rich in a number of enzymes involved in this task, suggesting that they might be useful as markers of ductal differentiation. The objective of this investigation was to delineate the developmental changes in activity of three of these, cytochrome C oxidase (CCO), succinate dehydrogenase (SDH), nicotinamide adenine phosphate dinucleotide (reduced form)-dehydrogenase (NADPH-DH). Histochemical localization of all three enzymes in fresh frozen sections was complemented by biochemical assays of CCO and SDH and cytochemical localization of CCO. Biochemically, CCO- and SDH-specific activity in gland homogenates increased progressively after birth, reaching adult levels at 21-28 days. Histochemically, deposits of reaction products of all three enzymes increased more in the striated and excretory ducts, especially in their basal cytoplasm, than in other glandular structures between 19 days in utero and 28 days after birth. During the same age span, the mitochondria in the striated and excretory ducts increased markedly in both number and size, migrated to a mostly basal location, and increased from many to virtually all showing strong cytochemical CCO reactions. These histochemical and cytochemical patterns of changes in enzyme activity at the cellular level accounted for the overall increases in CCO and SDH seen in the biochemical assays. Only the SDH histochemical reaction was consistently weak in the acini and intercalated ducts, and thus provided the most contrast with the progressively stronger reactions in the larger ducts. We conclude that of the three enzymes evaluated in these experiments, SDH is the best marker of the functional differentiation of the striated and excretory ducts in the developing rat parotid gland.

An enzyme histochemical and biochemical study of the activity of three oxidative enzymes in the developing rat parotid gland

Information on ductal differentiation in the developing rat parotid gland is sparse. One of the main functions of the striated and excretory ducts in this gland is the selective exchange of electrolytes from the primary fluid secreted by the acini. These ducts are rich in a number of enzymes involved in this task, suggesting that they might be useful as markers of ductal differentiation. The objective of this investigation was to delineate the developmental changes in activity of three of these, cytochrome C oxidase (CCO), succinate dehydrogenase (SDH), nicotinamide adenine phosphate dinucleotide (reduced form)-dehydrogenase (NADPH-DH). Histochemical localization of all three enzymes in fresh frozen sections was complemented by biochemical assays of CCO and SDH and cytochemical localization of CCO. Biochemically, CCO- and SDH-specific activity in gland homogenates increased progressively after birth, reaching adult levels at 21-28 days. Histochemically, deposits of reaction products of all three enzymes increased more in the striated and excretory ducts, especially in their basal cytoplasm, than in other glandular structures between 19 days in utero and 28 days after birth. During the same age span, the mitochondria in the striated and excretory ducts increased markedly in both number and size, migrated to a mostly basal location, and increased from many to virtually all showing strong cytochemical CCO reactions. These histochemical and cytochemical patterns of changes in enzyme activity at the cellular level accounted for the overall increases in CCO and SDH seen in the biochemical assays. Only the SDH histochemical reaction was consistently weak in the acini and intercalated ducts, and thus provided the most contrast with the progressively stronger reactions in the larger ducts. We conclude that of the three enzymes evaluated in these experiments, SDH is the best marker of the functional differentiation of the striated and excretory ducts in the developing rat parotid gland.

A Simulation of the Tertiary Current Density Distribution from a Chlorate Cell: I. Mathematical Model

Numerical modeling is becoming an integral part of all research and development within the field of electrolytic systems. A numerical model that calculates the current density distribution and concentration profiles of a chlorate cell is presented here. The results are shown as functions of electrolyte velocity and exchange current density. The model takes into account the three transport mechanisms; diffusion, migration, and convection by considering the development of the flow velocity vector through the channel. It was seen that the developing velocity profile influences the concentration overpotentials, which in turn influences current density distributions. Results from the model show that the total current density decreased along the length of the anode, and that this distribution varied more at lower velocities. In addition, it was seen that migration contributes significantly to species transport, even within the diffusion layer. Finally, the model indicates that the hypochlorite ion is the main participant in the principal side reaction producing oxygen, and not the hypochlorous acid molecule. The results are useful as they increase knowledge of the chlorate process, and can be used to simulate future systems with a wide range of varying parameters such as cell geometry, flow, electrolyte composition, and electrode materials. The aim of the model is to use it as a tool for identifying the sources that contribute to the overpotential in the cell. This article concentrates on the concentration overpotential, which is one of the phenomena that can actually be influenced. © 2001 The Electrochemical Society. All rights reserved.

In vivo study of electrolyte exchanges through membranes of saline-filled breast implants.

Saline-filled breast implants are currently used in breast reconstruction and augmentation. Free diffusion of electrolytes through these implants has been questioned recently and is of potentially high importance. Many questions are still unanswered about this phenomenon. Eighteen prostheses were reviewed and tested for diffusion and exchange of electrolytes and glucose in vivo. None of these implants demonstrated major variation of the inner contents from the original saline used to fill them, emphasizing the real innocuousness of such implants in terms of possible ionic pooling. Extrapolation of these results to all implants made by different manufacturers is not possible according to the sample size in the present study.

The alkaline aluminium/hydrogen peroxide power source in the Hugin II unmanned underwater vehicle

In 1993, The Norwegian Defence Research Establishment (FFI) demonstrated AUV-Demo, an unmanned (untethered) underwater vehicle (UUV), powered by a magnesium/dissolved oxygen seawater battery (SWB). This technology showed that an underwater range of at least 1000 nautical miles at a speed of 4 knots was possible, but also that the maximum hotel load this battery system could support was very limited. Most applications for UUV technology need more power over a shorter period of time. Seabed mapping using a multibeam echo sounder mounted on an UUV was identified as a viable application and the Hugin project was started in 1995 in cooperation with Norwegian industry. For this application, an endurance of 36 h at 4 knots was required. Development of the UUV hull and electronics system resulted in the UUV Hugin I. It carries a Ni/Cd battery of 3 kW h, allowing up to 6 h under-water endurance. In parallel, we developed a battery based on a combination of alkaline Al/air and SWB technology, using a circulating alkaline electrolyte, aluminium anodes and maintaining the oxidant concentration in the electrolyte by continuously adding hydrogen peroxide (HP) to the electrolyte. This concept resulted in a safe battery, working at ambient pressure (balanced) and with sufficient power and energy density to allow the UUV Hugin II to make a number of successive dives, each of up to 36 h duration and with only 1 h deck time between dives for HP refill and electrolyte exchange. After 100 h, an exchange of anodes takes place. The power source consists of a four-cell Al/HP battery, a DC/DC converter delivering 600 W at 30 V, circulation and dosing pumps and a battery control unit. Hugin II is now in routine use by the Norwegian Underwater Intervention AS (NUI) which operates the UUV for high-precision seabed mapping down to a water depth of 600 m.

Redoxspeciation of selenium in water samples by cathodic stripping voltammetry using an automated flow system

A method for the determination of Se(IV) and Se(VI) species in water samples is described based on the cathodic stripping voltammetry of copper selenide at the mercury electrode using an automated flow system. The use of a voltammetric flow-through cell facilitates the automation of the measurements. It is shown that the applied electrolyte exchange is reducing the matrix effect during the voltammetric determination step. The system was optimized systematically with respect to the electrochemical and hydrodynamic parameters. The prior reduction of Se(VI) to Se(IV) was carried out after 1 h of UV-irradiation in alkaline medium (pH 11.0). The content of Se(VI) was calculated from the difference between the content of Setotal and Se(IV), previously determined. The linear range for the measurements was from 1.0 to 150.0 µg l–1 with a detection limit calculated as 0.35 µg l–1 and a RSD of 1.4% (n = 5) for 5.0 µg l–1 of Se(IV) measured. During the UV-irradiation of water samples not only the reduction of Se(VI) takes place but also the decomposition of the organic matter present. The combination of both enables the speciation of Se(IV) and Se(VI) as well as the determination of total selenium in water samples with a high content of organic interferences. A mechanism for both photolytic processes, the reduction of selenium and decomposition of the organic matter is proposed, showing that both phenomena occur under the conditions used. The interferences of some organic compounds and inorganic ions were tested. Recoveries between 93 and 109% were obtained using the standard addition method for spiked samples of purified water, model water, drinking water and lake water. Additional measurements were carried out on a certified water sample.

Decrease in the Total Amount of Extracellular Bicarbonate Is Not Dilution

Decrease in the Total Amount of Extracellular Bicarbonate Is Not Dilution

Chlorine and sodium perfusion and electrolyte balance in human tissue and tumours before and during neutron and photon radiotherapy

Radiotherapy with nuclear reactor fission neutrons was applied in 49 cases of pre-treated patients with superficial metastases or relapses from primary carcinoma. Measurements of the decay rates of the radiation-induced radioactivity of , and in the irradiated tissue resulted in values for the simultaneous local kinetics of chlorine and sodium, and in approximate data on the electrolyte masses. The electrolytes were present in non-exchangeable and exchangeable compartments of soft tissue. Exchange times of the intravascular to extravascular turnover and the frequencies of the exchange fractions were determined for a series of irradiations. The results have been interpreted in terms of the mean electrolyte exchange rates, of a standardized functional blood flow, and of the supply capacity of the vascular system. In the average of all cases, the regional perfusion was reduced by about 30% by irradiation up to 14 Gy (equivalent photon dose ) connected with an increase in the non-exchangeable fractions. After fractionated doses higher than 14 Gy, functional blood flow and supply capacity increased to 120%, and fixed electrolytes were removed from the irradiated tissue. Data on electrolyte kinetics and vascularity are compared with the literature.

Capillary Electrochromatography with Predetermined Selectivity Obtained through Molecular Imprinting

This article presents a novel approach to capillary electrochromatography by which predetermined selectivity is achieved. A simple and quick method for the in situ preparation of monolithic molecularly imprinted flow-through polymers inside fused silica capillaries is described. The superporous structure of the polymers permits rapid solvent and electrolyte exchange, as well as easy regeneration of the capillaries by hydrodynamic pumping. Chiral stationary phases were prepared by molecular imprinting of the β-adrenergic antagonists propranolol and metoprolol. The separation systems were operational within 3 h of the start of capillary preparation. Chiral separations with baseline resolution could be carried out in less than 120 s.