Home About us Contact
|
Home About us Contact | ||
|
|
||
Electrolyte Concentration (electrolyte + concentration)
Selected AbstractsMaternal pseudo primary hyperaldosteronism in twin-to-twin transfusion syndromeBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 1 2007IL Gussi Objective, To monitor changes in the maternal renin,angiotensin,aldosterone system following laser therapy and amnioreduction in severe twin-to-twin transfusion syndrome (TTTS). Design, Observational prospective study. Setting, Single university hospital in Poissy, France. Population, Sixty cases of TTTS at 16,26 weeks of gestation. Method, Maternal blood sampling before, 6 and 24 hours following the procedure. Main outcome measures, Plasma levels of aldosterone, renin, angiotensin II (AII), atrial natriuretic peptide (ANP), vasopressin, sodium, potassium and plasma proteins together with full blood count were measured before, 6 and 24 hours following the procedure. Results, TTTS is associated with maternal hyperaldosteronism dissociated from renin,angiotensin changes. Correcting TTTS by placental surgery and amnioreduction triggers incomplete correction of hyperaldosteronism, as early as 6 hours following the procedure, without changes in AII but an increase in the levels of ANP in plasma. Electrolyte concentrations remained stable despite haemodilution, while vasoactive hormone levels such as that of vasopressin remained unchanged. Conclusion, Mechanisms involved in marked fluid retention in TTTS are rapidly corrected by laser therapy followed by amnioreduction while maintaining electrolyte homeostasis. [source] Elementary processes of soil,water interaction and thresholds in soil surface dynamics: a reviewEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2004Richard S. B. Greene Abstract Elementary processes of soil,water interaction and the thresholds to these processes are important to understand as they control a range of phenomena that occur at the soil surface. In particular processes involved with wetting by rainfall that lead to particle breakdown are critical. This breakdown causes soil detachment and crust formation, which are both key elements in erosion. This paper reviews the range of approaches that have been taken in describing the processes associated with the wetting of a soil surface by rainfall. It assembles the studies that emphasize soil physics, soil chemistry, and erosion mechanics in a framework to enable a balanced consideration of important processes and management strategies to control erosion for a particular situation. In particular it discusses the factors associated with the two basic processes of soil structural breakdown, i.e. slaking and dispersion, and how these processes are critical in particle detachment, transport and surface crust formation. Besides the balance between the exchangeable cation composition and electrolyte concentration (measured as the sodium adsorption ratio (SAR) and total cation concentration (TCC) respectively) of the soil, the importance of energy input and soil organic matter content in controlling clay dispersion is emphasized. Based on the balance between these factors, the soil can be in one of three different regions, i.e. a dispersed region, a ,occulated region and one where the resilience of the soil is variable. The implications of each of these regions to soil erosion management are brie,y outlined, as are the critical roles that soil cover levels and organic matter have in controlling erosion. Finally, the relationship between various laboratory measures of aggregate stability, and corresponding ,eld erosion characteristics, is discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Microwave Activation of Electrochemical Processes at Glassy Carbon and Boron-Doped Diamond ElectrodesELECTROANALYSIS, Issue 5-6 2005Kumar Sur, Ujjal Abstract Voltammetric experiments under intense microwave field conditions have been carried out at a carbon microfiber electrode, an array of carbon microfiber electrodes, and at a boron-doped diamond electrode. For the reversible one electron redox systems Fe(CN) and Ru(NH3) in aqueous KCl solution increased currents (up to 16 fold at a 33,,m diameter carbon microelectrode) and superheating (up to ca. 400,K at all types of electrodes) are observed. Electrodes with smaller diameter allow better signal enhancements to be achieved. From the missing effect of the supporting electrolyte concentration on the microwave enhanced currents, it can be concluded that effects observed at carbon electrodes (microwave absorbers) are due to the interaction of microwaves with the electrode material whereas for metal electrodes (microwave conductors) effects are dominated by the interaction of the microwaves with the aqueous dielectric. Short heat pulses can be applied by pulsing the microwave field and relatively fast temperature transients are observed for small electrodes. For the irreversible two electron oxidation of L -dopa in aqueous phosphate buffer, different types of effects are observed at glassy carbon and at boron-doped diamond. Arrays of carbon microfibers give the most reproducible and analytically useful current signal enhancements in the presence of microwaves. [source] Amperometric Ion Sensing Using Polypyrrole MembranesELECTROANALYSIS, Issue 5-6 2003Agata Michalska Abstract Oxidation/reduction of conducting polymers, coupled with ion exchange between the polymer and electrolyte solution can be utilized for amperometric ion sensing. Electrochemically deposited "model" polypyrrole membranes doped by chloride (PPyCl) and hexacyanoferrate (PPyFeCN) anions were studied from the point of view of their advantages and limits for amperometric determination of electroinactive anions and cations, respectively. Monotonous dependences of the current on electrolyte concentration were obtained for short reading times after potential step application (in the range of ms). The experimental conditions were optimized to obtain linear dependences: log (current) vs. log (KCl concentration) within the range 10,6,1,M. The advantages of the amperometric method over the potentiometric one are highlighted: much lower effect of redox and pH interferences, wider concentration range, elimination of long conditioning procedure. [source] On-line concentration of proteins in pressurized capillary electrochromatography coupled with electrospray ionization-mass spectrometryELECTROPHORESIS, Issue 7-8 2005Zhen Liang Abstract Pressurized capillary electrochromatography (pCEC) and electrospray ionization-mass spectrometry (ESI-MS) have been hyphenated for protein analysis. Taken cytochrome,c, lysozyme, and insulin as samples, the limits of detection (LODs) for absolute concentrations are 10,11,mol (signal-to-noise ratio S/N = 3) with relative standard deviations (RSDs) of retention time and peak area, respectively, of less than 1.7% and 4.8%. In order to improve the detection sensitivity, on-line concentration by field-enhanced sample-stacking effect and chromatographic zone-sharpening effect has been developed, and parameters affecting separation and detection, such as pH and electrolyte concentration in the mobile phase, separation voltage, as well as enrichment voltage and time, have been studied systematically. Under the optimized conditions, the LODs of the three proteins could be decreased up to 100-fold. In addition, the feasibility of such techniques has been further demonstrated by the analysis of modified insulins at a concentration of 20,,g/mL. [source] Effect of acetate-free biofiltration with a potassium-profiled dialysate on the control of cardiac arrhythmias in patients at risk: A pilot studyHEMODIALYSIS INTERNATIONAL, Issue 1 2008Rosa I. MUÑOZ Abstract Cardiac arrhythmias are a frequent event in chronic hemodialysis patients. The aim of this study was to evaluate the efficacy and safety of acetate-free hemofiltration with potassium-profiled dialysate (AFB-K) dialysis compared with constant potassium acetate-free biofiltration (AFB). Twelve patients (mean age 79 years) affected by cardiac arrhythmias or at a high risk for arrhythmia (advanced age, hypertension, left ventricular hypertrophy, heart valve disease, coronary artery disease, diabetes, paroxysmal atrial fibrillation) participated in a single-center, sequential cohort study. All were treated with hemodialysis 3 times per week, using constant potassium AFB for the first 3 weeks, followed by an AFB-K dialysate for the subsequent 3 weeks. The hemofilter, duration of dialysis, and electrolyte concentration were the same in both treatments. Both AFB-K and constant potassium AFB dialytic techniques were safe and well tolerated. The results of biochemical tests were similar, except for serum potassium levels after 2 hr of dialysis, which were significantly higher in the AFB-K group (4.0 mmol/L) than in the constant potassium AFB group (3.6 mmol/L) (p<0.001). All cardiac variables improved during AFB-K dialysis. There was a significant reduction of postdialysis QT intervals corrected for heart rate in the AFB-K group (448.8 ms) compared with the constant potassium AFB group (456.8 ms) (p=0.039). The severity and mean number of ventricular extasystoles also decreased (163.5 vs. 444.5/24 hr). Potassium profiling during hemodialysis treatment may be beneficial for patients with arrhythmias or at those risk of arrhythmias, particularly those with predialysis hyperkalemia. [source] Using a pore-scale model to quantify the effect of particle re-arrangement on pore structure and hydraulic propertiesHYDROLOGICAL PROCESSES, Issue 8 2007Oagile Dikinya Abstract A pore-scale model based on measured particle size distributions has been used to quantify the changes in pore space geometry of packed soil columns resulting from a dilution in electrolyte concentration from 500 to 1 mmol l,1 NaCl during leaching. This was applied to examine the effects of particle release and re-deposition on pore structure and hydraulic properties. Two different soils, an agricultural soil and a mining residue, were investigated with respect to the change in hydraulic properties. The mining residue was much more affected by this process with the water saturated hydraulic conductivity decreasing to 0·4% of the initial value and the air-entry value changing from 20 to 50 cm. For agricultural soil, there was little detectable shift in the water retention curve but the saturated hydraulic conductivity decreased to 8·5% of the initial value. This was attributed to localized pore clogging (similar to a surface seal) affecting hydraulic conductivity, but not the microscopically measured pore-size distribution or water retention. We modelled the soil structure at the pore scale to explain the different responses of the two soils to the experimental conditions. The size of the pores was determined as a function of deposited clay particles. The modal pore size of the agricultural soil as indicated by the constant water retention curve was 45 µm and was not affected by the leaching process. In the case of the mining residue, the mode changed from 75 to 45 µm. This reduction of pore size corresponds to an increase of capillary forces that is related to the measured shift of the water retention curve. Copyright © 2007 John Wiley & Sons, Ltd. [source] The stabilization of L -ascorbic acid in aqueous solution and water-in-oil-in-water double emulsion by controlling pH and electrolyte concentrationINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2004J.-S. Lee This study presents a new approach that can stabilize effectively l -ascorbic acid in water-in-oil-in-water (w/o/w) double emulsions. Basically, the behavior of l -ascorbic acid in the aqueous phase was observed, considering its molecular deformation. Then, it was found that the stability determined in the aqueous phase by high-performance liquid chromatography (HPLC) showed that the collapse of ionization of l -ascorbic acid played a crucial role in protecting the molecular deformation. Then, the stable aqueous system was incorporated into the internal aqueous phase of the double emulsions. From the PLC analysis, it was observed that the l -ascorbic acid in an appropriate system showed high molecular stability for a long time. Moreover, in the measurement of in vitro skin permeation, the l -ascorbic acid stabilized in this study showed considerable skin permeation ability, indicating its potential applicability in pharmaceutics and cosmetics. [source] Reaction-limited aggregation in presence of short-range structural forcesAICHE JOURNAL, Issue 4 2005Venkataramana Runkana Abstract A geometrically discretized sectional population balance model for reaction-limited aggregation of colloidal suspensions is presented. The two important model parameters are collision frequency factor and collision efficiency factor. The collision frequency factor is derived from physically realistic arguments proposed for collision of fractal aggregates. The collision efficiency factor is computed as a function of total interaction energy between particles, including short-range structural repulsion forces. The irregular and open structure of aggregates is taken into account by incorporating their mass fractal dimension. The characteristic time constant of reaction-limited aggregation, derived from dynamic scaling of mean aggregate size-aggregation time data, is found to correlate with electrolyte concentration. The population balance model is tested with published experimental data for aggregation of ,-alumina suspensions in the presence of different electrolytes. It is shown that the slow kinetics of aggregation under certain conditions of pH and electrolyte concentration require inclusion of short-range structural repulsion forces along with van der Waals attraction and electrical double layer repulsion forces in an extended DLVO theory. The model predictions are in good agreement with experimental data for time evolution of mean aggregate diameter in the reaction-limited aggregation regime. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Kinetics of microbubble,solid surface interaction and attachmentAICHE JOURNAL, Issue 4 2003Chun Yang Microbubble,solid surface interaction and attachment under the influence of hydrodynamic and physicochemical forces were studied experimentally and theoretically. An impinging-jet technique was developed to measure bubble-attachment flux onto a flat solid surface in an impinging-jet stagnation flow. A video imaging system enables direct observation of the attachment behavior of hydrogen microbubbles onto two different collector surfaces: hydrophilic untreated glass and hydrophobic methylated glass. Experimental results showed that the attachment flux depends on both hydrodynamic flow and electrolyte concentration. A mass-transfer model developed computes bubble-attachment flux, considering hydrodynamic convection, Brownian diffusion, migration under gravitational buoyancy, and DLVO surface forces (that is, van der Waals and electric double-layer forces). At high flow rates, the numerical predictions for attachment rates onto methylated glass generally agreed well with the experimental data. However, a difference exists between theoretical and experimentally determined attachment rates for both untreated and methylated glass when the Reynolds number of the flow is low. Several mechanisms are proposed to account for this discrepancy. [source] Mesoporous GaAs double layers for layer transfer processesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2009Enrique Garralaga Rojas Abstract Mesoporous GaAs double layers with different porosities and thicknesses up to 7,µm are formed on highly doped p-type 4,inch GaAs substrates by means of electrochemical etching in highly concentrated hydrofluoric acid electrolytes. Small ,111, oriented pyramids form at the interface between porous layer and substrate if etching current densities below 7.5,mA,cm,2 are applied. Porous double layers with different porosities are obtained by varying simultaneously the etching current density and the electrolyte concentration. The porosity of the porous GaAs layers decreases nearly linearly from 69 to 53% with electrolyte concentrations increasing from 30 to 50,wt.%, respectively. The etching process increases the mean roughness of the porous layer surface from 0.15 to 0.24,nm. [source] Investigations on porous silicon as electrode material in electrochemical capacitorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007S. Desplobain Abstract In this study, we have demonstrated the possibility of using macroporous silicon electrodes in electrochemical capacitors. Macroporous silicon was used to increase the surface exchange between pore surface and electrolyte. The inherent resistivity of the porous silicon can be reduced through the use of subsequent doping and metallization processes of the macropore surface. A systematic study of the electrolyte concentration and the porous silicon depth influences was also performed. A unit cell capacitance value of 320 µF/cm2 was obtained with doped and metallized p-type macroporous silicon electrodes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Gas Hold-Up in Stirred Tank Reactors in the Presence of Inorganic ElectrolytesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2002Archis A. Yawalkar Abstract Gas hold-up (,G) in air-aqueous electrolyte solutions in stirred tank reactors (STR) is correlated using a relative gas dispersion parameter, N/Ncd and a surface tension factor (STF), (c/z)(d,/dc)2. For electrolyte concentration below transition concentration (ct) a single correlation in the form of ,G = f(N/Ncd, vvm, STF) shows good agreement with gas hold-up data over a wide range of system and operating conditions. Above ct no effect of STF on gas hold-up is observed and the correlation obtained is of the form ,G = f(N/Ncd, vvm). Data available in the literature on large STR show good fit with the proposed correlation. On a corrélé la rétention de gaz (,G) dans un mélange air-solutions d'électrolytes aqueuses dans des réacteurs à réservoir agité (RRA) à l'aide d'un paramètre de dispersion de gaz, N/Ncd, et d'un facteur de tension de surface (FTS), (c/z)(d,/dc)2. Pour une concentration d'électrolytes en-dessous de la concentration de transition (ct), une corrélation simple sous la forme ,G = f(N/Ncd, vvm, STF) montre un bon accord avec les données de rétention de gaz pour une vaste gamme de conditions de systèmes et de fonctionnement. Au-dessus de ct, on observe aucun effet du STF sur la rétention de gaz et la corrélation obtenue est de la forme ,G = f(N/Ncd, vvm). Les données disponibles dans la littérature scientifique sur des RRA de grande taille montrent un bon accord avec la corrélation proposée. [source] Degradation of tetracycline in aqueous medium by electrochemical methodASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Hui Zhang Abstract The degradation of tetracycline by anode oxidation with Ti/RuO2,IrO2 electrode was carried out in an electrochemical cell. The effect of operating conditions such as electrical current density, initial pH, antibiotic concentration, electrolyte concentration and hydroxyl radical scavenger on the oxidation of tetracycline was investigated. The results showed that the degradation of tetracycline followed apparent pseudo-first-order kinetics. The rate constant increased linearly with the current density, but the oxidation curves displayed the same dependence on the amount of the specific charge passed. The degradation rate decreased with the initial antibiotic concentration. Either initial pH or electrolyte concentration had little effect on the electrochemical oxidation of tetracycline. The presence of tert -butanol did not hinder the degradation rate, indicating the radical contribution to the oxidation of tetracycline could be neglected. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Intensification of Rate of Diffusion Controlled Reactions in a Parallel Plate Electrochemical Reactor Stirred by a Curtain of Electrochemically Generated Gas BubblesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2007G. H. Sedahmed Abstract Rates of mass transfer were measured at a vertical plate stirred by a rising curtain of oxygen bubbles generated electrochemically at an upstream plate by measuring the limiting current of the cathodic reduction of K3Fe(CN)6 in alkaline solution. The rate of mass transfer was found to increase over the natural convection value by a factor ranging from 2.4 to 25 compared to the previously reported range of 2,5 in the case of copper deposition from acidified solutions. The high tendency of oxygen bubbles to coalesce in alkaline solutions is believed to be responsible for the high rates of mass transfer in alkaline solutions. The rate of mass transfer at a plate stirred by a curtain of oxygen bubbles was found to decrease with increasing plate height and electrolyte concentration. Curtains of H2 bubbles were found to be less effective in enhancing the rate of mass transfer compared to that of oxygen. Practical application of the results in designing a modified parallel plate electrochemical reactor stirred by a counterelectrode gas curtain was highlighted. The suggested design has the potential of saving part or all of the mechanical stirring energy as well as floor space since it extends vertically. [source] Indirect Electrochemical Oxidation of Phenol in the Presence of Chloride for Wastewater TreatmentCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2005D. Rajkumar Abstract Electrochemical oxidation of phenol using a Ti/TiO2 -RuO2 -IrO2 anode in the presence of chloride as the supporting electrolyte was investigated. The experiments were performed in an undivided batch reactor. Preliminary investigations showed that only a small fraction of phenol was oxidized by direct electrolysis, while complete degradation of phenol was achieved by indirect electrochemical oxidation using chloride as a supporting electrolyte. The effect of operating parameters such as initial pH, supporting electrolyte concentration, phenol concentration, and charge input was studied using Box-Behnken second order composite experimental design. The effect of current density on COD removal was studied separately. TOC removal and AOX formation were studied for selected conditions. It was found that the formation of chlorinated organic compounds was pronounced at the beginning of electrolysis, but it was reduced to lower levels by extended electrolysis. [source] Spectroscopic and Electrochemical Evaluation of Salt Effects on Electron-Transfer Equilibria between Donor/Acceptor and Ion-Radical Pairs in Organic SolventsCHEMPHYSCHEM, Issue 16 2008Sergiy V. Rosokha Dr. Abstract Addition of "inert" tetrabutylammonium hexafluorophosphate (Bu4NPF6) to a solution of TMDO/DDQ in dichloromethane (where TMDO=2,2,6,6-tetramethylbenzo[1,2-d;4,5-d]bis[1,3]-dioxole, donor, and DDQ=diclorodicyano-p-benzoquinone, acceptor) is accompanied by drastic changes in the electronic spectrum, which are related to the appearance of the DDQ,. and TMDO+. ion radicals and a decrease in the concentration of the neutral molecules and the charge-transfer complex [TMDO,DDQ]. These changes point to a considerable rise (of about three orders of magnitude) in the apparent electron-transfer equilibrium constant (KET) for this donor/acceptor pair upon increasing the electrolyte concentration from 0 to 0.5,M. Accordingly, the ion-radical fractions and KET values are higher in dichloromethane, at high electrolyte concentrations, than in acetonitrile (where the effect of Bu4NPF6 is less pronounced). Similar trends of the apparent equilibrium constants are observed for the tetramethyl-p-phenylenediamine/tetracyanoethylene pair. Electron-transfer equilibrium constants for both donor/acceptor dyads obtained from spectral measurements are related to those derived from the redox potentials of the reactants. The effects of media variations on the electron-transfer equilibria are discussed within the ion-pairing and ionic-activity frameworks. [source] Stripping Voltammetry of Cerium(IIl) with a Chemically Modified Carbon Paste Electrode Containing Functionalized Nanoporous Silica GelELECTROANALYSIS, Issue 2 2008Mehran Javanbakht Abstract This research introduces the design of an adsorptive stripping voltammetric method for the cerium(III) determination at a carbon paste electrode, chemically modified with dipyridyl-functionalized nanoporous silica gel (DPNSG-CPE). The electroanalytical procedure comprised two steps: the Ce(III) chemical accumulation at ,200,mV followed by the electrochemical detection of the Ce(III)/dipyridyl complex, using anodic stripping voltammetry. The factors, influencing the adsorptive stripping performance, were optimized including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The resulting electrode demonstrated a linear response over a wide range of Ce(III) concentration (1.0,28,ng mL,1). The precision for seven determinations of 4 and 10,ng mL,1 Ce(III) was 3.2% and 2.5% (relative standard deviation), respectively. The prepared electrode was used for the cerium determination in real samples and very good recovery results were obtained. [source] Effects of oral electrolyte supplementation on endurance horses competing in 80 km ridesEQUINE VETERINARY JOURNAL, Issue S36 2006F. SAMPIERI Summary Reasons for performing study: There is no evidence that use of oral electrolyte pastes enhances performance in competing endurance horses. Objective: To ascertain whether oral administration of a high dose (HD) of sodium chloride (NaCl) and potassium chloride (KCl) to endurance horses would differentially increase water intake, attenuate bodyweight (bwt) loss and improve performance when compared to a low dose (LD). Methods: A randomised, blinded, crossover study was conducted on 8 horses participating in two 80 km rides (same course, 28 days apart). Thirty minutes before and at 40 km of the first ride 4, horses received orally 0.2 g NaCl/kg bwt and 0.07 g KCl/kg bwt. The other 4 received 0.07 g NaCl/kg bwt and 0.02 g KCl/kg bwt. Horses received the alternate treatment in the second ride. Data were analysed with 2-way ANOVA for repeated measures (P<0.05). Results: Estimated water intake was significantly greater with HD both at the 40 km mark and as total water intake; however, differences in bwt loss and speed between HD and LD were not found. Treatment significantly affected serum Na+, Cl,, HCO3, pH and water intake, but not serum K+ or bwt. Serum Na+ and Cl, were significantly higher at 80 km when horses received HD, but no differences were found in early recovery. Venous HCO3 and pH were significantly lower throughout the ride and in early recovery when horses received HD. Conclusions and potential relevance: Other than enhancing water intake, supplementing endurance horses with high doses of NaCl and KCl did not provide any detectable competitive advantage in 80 km rides. Further, the elevated serum electrolyte concentrations induced with HD might not be appropriate for endurance horses. [source] The workload of riding-school horses during jumpingEQUINE VETERINARY JOURNAL, Issue S36 2006M. M. SLOET Van OLDRUITENBORGH-OOSTERBAAN Summary Reasons for performing the study: As there are no reports on the real workload of horses that jump fences, this study was undertaken in riding-school horses. Objective: To compare the workload of horses jumping a course of fences with that of horses cantering over the same course at the same average speed without jumping fences. The workload variables included heart rate (HR), packed cell volume (PCV), acid-base balance (venous pH, pCO2, HCO3,) and blood lactate (LA), glucose, total protein and electrolyte concentrations. Methods: Eight healthy riding-school horses performed test A (a course of approximately 700 m with 12 jumps from 0.8-1.0 m high at an average speed of approximately 350 m/min) and test B (same course at the same speed, but without the rails) in a crossover study with at least 4 h between the 2 tests. Before each test the horses were fitted with a heart rate meter (Polar Electro)1. Blood samples were taken from the jugular vein at rest prior to the test, after warm-up before starting the course, immediately after the course and after recovery. All samples were analysed immediately. Results: The mean ± s.d maximal HR (beats/min) during the course (184 ± 17 and 156 ± 21, respectively) and the mean HR after recovery (75 ± 6 and 63 ± 7, respectively) were significantly higher in test A compared to test B (P=0.001 and P=0.007 respectively). The mean LA concentrations after the course and after recovery (mmol/1) were significantly higher in test A (3.6 ± 2.7 and 1.0 ± 0.9, respectively) compared to test B (0.9 ± 0.5 and 0.3 ± 0.1, respectively), (P=0.016 and P = 0.048 respectively). The mean PCV (1/1) after the course and after recovery was also significantly different between tests A (0.48 ± 0.04 and 0.39 ± 0.03, respectively) and B (0.42 ± 0.04 and 0.36 ± 0.03, respectively) (P<0.01). The mean pH and the mean HCO3, (mmol/1) after the course were significantly lower in test A (7.40 ± 0.04 and 28.9 ± 1.4, respectively) compared to test B (7.45 ± 0.03 and 30.4 ± 2.3, respectively) (P<0.05). Conclusions: This study indicates that in riding-school horses jumping fences, even at a low level competition, provokes a significant workload compared to cantering the same distance and speed without fences. Potential relevance: This study makes it clear that the extra workload of jumping fences should be taken into account in the training programmes of jumping horses. Further research with more experienced horses jumping higher fences will reveal the workload for top-level jumping horses. [source] Biochemical Analysis of Pericardial Fluid and Whole Blood in Dogs with Pericardial EffusionJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 6 2005Armelle M. de Laforcade Studies evaluating pericardial fluid analysis in dogs to determine the etiology of pericardial effusions have yielded conflicting results. The purpose of this prospective study was to compare acid-base status, electrolyte concentrations, glucose, and lactate of pericardial fluid to peripheral blood from dogs with pericardial effusion and to compare these variables between dogs with neoplastic and nonneoplastic pericardial effusion. Acid-base status, electrolyte concentrations, glucose, hematocrit, urea nitrogen, and lactate concentrations were evaluated in peripheral blood samples and in pericardial effusion samples of 41 client-owned dogs with pericardial effusion. Common abnormal findings in the peripheral blood of dogs with pericardial effusion included hyperlactatemia (n = 38 [of 41]; 93%), hyponatremia (n = 25/41; 61%), hyperglycemia (n = 13/41; 32%), and hypermagnesemia (n = 13/41; 32%). Bicarbonate, sodium, ionized calcium, glucose, and hematocrit were all significantly lower in the pericardial fluid compared with peripheral blood, whereas lactate, chloride, and PCO2 were significantly higher in the pericardial fluid. When comparing the concentrations of variables in the pericardial fluid of dogs with neoplasia (n = 28) to those without neoplasia (n = 13), pH, bicarbonate, and chloride were significantly lower in dogs with neoplasia, whereas lactate, hematocrit, and urea nitrogen were significantly higher in the pericardial fluid of dogs with neoplasia. The difference between peripheral and pericardial glucose concentrations was significantly larger in dogs with neoplasia than in dogs without neoplasia. Although differences between variables in dogs with neoplastic and nonneoplastic pericardial effusion were documented, clinical relevance is likely limited by the degree of overlap between the 2 groups. [source] Metabolic alkalosis with hypoelectrolytemia in infants with cystic fibrosisPEDIATRICS INTERNATIONAL, Issue 3 2002Stojka Fustik Abstract Background: Infants with cystic fibrosis (CF) can develop episodes of hyponatremic hypochloremic dehydration with metabolic alkalosis when they sweat excessively, which is not caused by sweating in normal infants. We investigated the incidence of the metabolic alkalosis with hypoelectrolytemia in CF infants, the possible risk factors for its occurrence and the importance of the manifestation in the diagnosis of CF. Methods: In order to evaluate the incidence and the risk factors for the development of this sweat-related metabolic disorder in CF, we reviewed the records of all children diagnosed as having CF before the age of 12 months in a 10-year period. Data analysis included medical history data, clinical features, biochemical parameters (blood pH, serum bicarbonate, sodium, chloride and potassium levels), sweat chloride test values, as well as genetic analysis data. Results: The prevalence of metabolic alkalosis in association with low serum electrolyte concentrations (hyponatremia, hypochloremia, and hypokalemia) in infant CF population in our region was 16.5%. We found no season predilection in its occurrence. Early infant age, breast-feeding, delayed CF diagnosis, heat exhaustion and the presence of severe CF transmembrane conductance regulator mutations are predisposed factors for the development of metabolic alkalosis with hypoelectrolytemia. Conclusions: The results from our study suggest that metabolic alkalosis with hypoelectrolytemia is a relatively common manifestation of CF in infancy. The possibility of CF should be seriously considered in any infant with this metabolic disorder. [source] Mesoporous GaAs double layers for layer transfer processesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2009Enrique Garralaga Rojas Abstract Mesoporous GaAs double layers with different porosities and thicknesses up to 7,µm are formed on highly doped p-type 4,inch GaAs substrates by means of electrochemical etching in highly concentrated hydrofluoric acid electrolytes. Small ,111, oriented pyramids form at the interface between porous layer and substrate if etching current densities below 7.5,mA,cm,2 are applied. Porous double layers with different porosities are obtained by varying simultaneously the etching current density and the electrolyte concentration. The porosity of the porous GaAs layers decreases nearly linearly from 69 to 53% with electrolyte concentrations increasing from 30 to 50,wt.%, respectively. The etching process increases the mean roughness of the porous layer surface from 0.15 to 0.24,nm. [source] An analysis of renal dysfunction in 1511 patients with fractured neck of femur: the implications for peri-operative analgesiaANAESTHESIA, Issue 10 2009S. M. White Summary Following two deaths from respiratory failure secondary to opioid toxicity in patients admitted for surgical repair of fractured neck of femur, we retrospectively studied the serum urea and electrolyte concentrations of 1511 consecutive patients requiring surgery for proximal femoral fracture, and calculated their glomerular filtration rate. Five hundred and forty-five (36.1%) patients had renal dysfunction on admission (glomerular filtration rate < 60 ml.min,1.1.73 m,2); 435 (28.8%) had grade 3 chronic kidney disease (moderate; glomerular filtration rate 30,59 ml.min,1.1.73 m,2), 82 (5.4%) had grade 4 disease (severe; glomerular filtration rate 15,29 ml.min,1.1.73 m,2) and 28 (1.9%) had grade 5 (renal failure; glomerular filtration rate < 15 ml min,1.1.73 m,2). The 30-day mortality for patients with renal dysfunction (62/536; 11.6%) was significantly greater (p = 0.004) than for patients with normal renal function (68/958; 7.1%), although median (IQR [range]) postoperative lengths of stay were similar 15 (10,22 [1,125]) vs 14 (9,22 [1,120]) days respectively; p = 0.06). Renal impairment is common in patients admitted for fixation of fractured neck of femur, who are consequently at risk of opioid toxicity. [source] Charge Transport in Redox Polyelectrolyte Multilayer Films: The Dramatic Effects of Outmost Layer and Solution Ionic StrengthCHEMPHYSCHEM, Issue 13 2010Dr. Mario Tagliazucchi Abstract The redox switching kinetics, that is, charge transfer and transport in layer-by-layer-deposited electroactive polyelectrolyte multilayers is systematically studied with variable-scan-rate cyclic voltammetry. The experiments are performed with films finished in the redox polycation (an osmium pyridine,bipyridine derivatized polyallylamine, PAH-Os) and the polyanion (polyvinyl sulfonate, PVS), in solutions of different electrolyte concentrations. A modified diffusion model is developed to account for the experimentally observed dependence of the average peak potential with the scan rate. This model is able to describe both the redox peak potential and the current, providing information on the electron-transfer rate constants and the diffusion coefficient for the electron-hopping mechanism. While the former does not vary with the ionic strength or the nature of the outmost layer, polyanion-capped films present an electron-hopping diffusion coefficient at low ionic strength that is three orders of magnitude smaller than that for PAH-Os-capped films. The effect is offset at high ionic strength. We discuss the possible causes of the effect and the important consequences for electrochemical devices built by layer-by-layer self-assembly, such as amperometric biosensors or electrochromic devices. [source] Spectroscopic and Electrochemical Evaluation of Salt Effects on Electron-Transfer Equilibria between Donor/Acceptor and Ion-Radical Pairs in Organic SolventsCHEMPHYSCHEM, Issue 16 2008Sergiy V. Rosokha Dr. Abstract Addition of "inert" tetrabutylammonium hexafluorophosphate (Bu4NPF6) to a solution of TMDO/DDQ in dichloromethane (where TMDO=2,2,6,6-tetramethylbenzo[1,2-d;4,5-d]bis[1,3]-dioxole, donor, and DDQ=diclorodicyano-p-benzoquinone, acceptor) is accompanied by drastic changes in the electronic spectrum, which are related to the appearance of the DDQ,. and TMDO+. ion radicals and a decrease in the concentration of the neutral molecules and the charge-transfer complex [TMDO,DDQ]. These changes point to a considerable rise (of about three orders of magnitude) in the apparent electron-transfer equilibrium constant (KET) for this donor/acceptor pair upon increasing the electrolyte concentration from 0 to 0.5,M. Accordingly, the ion-radical fractions and KET values are higher in dichloromethane, at high electrolyte concentrations, than in acetonitrile (where the effect of Bu4NPF6 is less pronounced). Similar trends of the apparent equilibrium constants are observed for the tetramethyl-p-phenylenediamine/tetracyanoethylene pair. Electron-transfer equilibrium constants for both donor/acceptor dyads obtained from spectral measurements are related to those derived from the redox potentials of the reactants. The effects of media variations on the electron-transfer equilibria are discussed within the ion-pairing and ionic-activity frameworks. [source] Experimental Study on the Molecular Dimension and Configuration of Polymer and Its Flow Characteristics from Electrolyte EffectCHINESE JOURNAL OF CHEMISTRY, Issue 4 2009Xiangguo LU Abstract Molecular clew dimension and configuration of polymer, and flow characteristics of polymer solution were studied from electrolyte effect, by making use of dynamic light scattering (DLS), scanning electron microscopy (SEM), apparent viscosity method and core flow experiment. It can be observed that with the electrolyte concentration increasing, there exists a variation trend of "decreasing, increasing and decreasing again" to the molecular clew dimension of the polymer. The compression action of Ca2+ or Mg2+ to the double electrode layer of polymer molecules is more powerful by comparison against Na+, which results in that Ca2+ and Mg2+ have a more extensive effect on the viscosity of polymer solution, and clew dimensions and their distribution. With the electrolyte concentration increasing, the polymer molecular configuration of multi-layer stereoscopic random reticulation transformed into a dendritic one. During the succeeding water flooding, the variation degree of injection pressure of core was mainly determined by the swelling extent of molecular clew of retained polymer and the produced amount of polymer. And the bigger the molecular weight of polymer is, the stronger the compression or swelling action of electrolyte to the molecule clews is, and the greater the increasing degree of injection pressure during succeeding water flooding is. The greater difference of electrolyte concentrations in used water between polymer flooding and succeeding water flooding can result in greater increasing degree of injection pressure during the succeeding water flooding. So, an advisable increasing in difference of electrolyte concentrations in used water between the polymer flooding and succeeding water flooding was proposed when designing the polymer flooding performance in oilfields, which has promising result for improving effect of polymer flooding. [source] Vasopressin V1A Receptor Antagonism Does Not Reverse Adrenocorticotrophin-Induced Hypertension In The RatCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2000Tafline B Fraser SUMMARY 1. The role of arginine vasopressin (AVP) was examined in adrenocorticotrophin (ACTH)-induced hypertension in Sprague-Dawley rats using the non-peptide AVP V1a receptor antagonist OPC 21268. 2. In an acute study, six rats were pretreated with ACTH for 11 days and direct arterial blood pressure (4 h), plasma osmolality and electrolyte concentrations were measured after OPC 21268 gavage. In a chronic study, 40 rats were randomly divided into four groups: (i) sham injection + sham gavage; (ii) ACTH + sham gavage; (iii) sham injection + OPC 21268; or (iv) ACTH + OPC-21268 for 16 days. Systolic blood pressure (SBP), water intake, urine volume (UV), urine osmolality and electrolytes, food intake, bodyweight and plasma osmolality and electrolyte concentrations were measured. 3. In the acute study, direct mean arterial blood pressure did not change with OPC 21268 (122±2 and 120±3 mmHg at 0 and 240 min, respectively). 4. In the chronic study, OPC 21268 did not affect ACTH-induced rises in blood pressure (from 125±2 (control) to 145±5 mmHg (group 4) compared with 122±3 (control) to 149±5 mmHg (group2)). Water intake and UV increased (from 29±2 to 83±6 mL/day; and from 5±1 to 36±5 mL/day, respectively) and the change in bodyweight decreased from 0±2 to ,107±7 g. 5. These results suggest that AVP (at the V1a receptor) does not play a significant role in the maintenance of ACTH-induced hypertension. [source] | |||||||||||||||||||