Nickel adsorption in two Oxisols and an Alfisol as affected by pH, nature of the electrolyte, and ionic strength of soil solution

Background, aim, and scope The retention of potentially toxic metals in highly weathered soils can follow different pathways that variably affect their mobility and availability in the soil-water-plant system. This study aimed to evaluate the effects of pH, nature of electrolyte, and ionic strength of the solution on nickel (Ni) adsorption by two acric Oxisols and a less weathered Alfisol. Materials and methods The effect of pH on Ni adsorption was evaluated in surface and subsurface samples from a clayey textured Anionic `Rhodic` Acrudox ( RA), a sandy-clayey textured Anionic `Xantic` Acrudox (XA), and a heavy clayey textured Rhodic Kandiudalf (RK). All soil samples were equilibrated with the same concentration of Ni solution (5.0 mg L(-1)) and two electrolyte solutions (CaCl(2) or NaCl) with different ionic strengths (IS) (1.0, 0.1 and 0.01 mol L(-1)). The pH of each sample set varied from 3 to 10 in order to obtain sorption envelopes. Results and discussion Ni adsorption increased as the pH increased, reaching its maximum of nearly pH 6. The adsorption was highest in Alfisol, followed by RA and XA. Competition between Ni(2+) and Ca(2+) was higher than that between Ni(2+) and Na(+) in all soil samples, as shown by the higher percentage of Ni adsorption at pH 5. At pH values below the intersection point of the three ionic strength curves (zero point of salt effect), Ni adsorption was generally higher in the more concentrated solution (highest IS), probably due to the neutralization of positive charges of soil colloids by Cl(-) ions and consequent adsorption of Ni(2+). Above this point, Ni adsorption was higher in the more diluted solution (lowest ionic strength), due to the higher negative potential at the colloid surfaces and the lower ionic competition for exchange sites in soil colloids. Conclusions The effect of ionic strength was lower in the Oxisols than in the Alfisol. The main mechanism that controlled Ni adsorption in the soils was the ionic exchange, since the adsorption of ionic species varied according to the variation of pH values. The ionic competition revealed the importance of electrolyte composition and ionic strength on Ni adsorption in soils from the humid tropics. Recommendations and perspectives The presence of NaCl or CaCl(2) in different ionic strengths affects the availability of heavy metals in contaminated soils. Therefore, the study of heavy metal dynamics in highly weathered soils must consider this behavior, especially in soils with large amounts of acric components.

Synthesis, characterization and electrochemical behavior of the vanadium pentoxide/cetyl pyridinium chloride hybrid material

In situ and ex situ studies concerning the new hybrid material vanadium pentoxide xerogel in the presence of the cationic surfactant cetyl pyridinium chloride (V(2)O(5)/CPC) are presented. The in situ characterization studies revealed the presence of a lamellar structure for the V(2)O(5)/CPC hybrid material. The intercalation reaction was evidenced on the basis of the increase in the d-spacing as well as the displacement of the infrared bands toward lower energy levels. Electrochemical studies comprising the cyclic voltammetry and the electrochemical impedance spectroscopy techniques showed that the behavior of the hybrid material is considerably influenced by the electrolyte composition. The ion insertion/de-insertion into the V(2)O(5) xerogel structure accompanying the charge transfer process is influenced by the solid-state diffusion process modeled by using the finite-space Warburg element.

Electrochemical vs antibacterial characterization of ZrCN-Ag coatings

Nowadays, antibacterial properties are becoming a viable feature to be introduced in biomaterials due to the possibility of modifying the materials' surface used in medical devices in a micro/nano metric scale. As a result, it is mandatory to understand the mechanisms of the antimicrobial agents currently used and their possible failures. In this work, the antibacterial activity of ZrCNAg films is studied, taking into consideration the ability of silver nanoparticles to be dissolved when embedded into a ceramic matrix. The study focuses on the silver release evaluated by glow discharge optical emission spectroscopy and the effect of the fluid composition on this release. The results revealed a very low silver release of the films, leading to non-antibacterial activity of such materials. The silver release was found to be dependent on the electrolyte composition. NaCl (8.9 g L? 1) showed the lowest spontaneously silver ionization, while introducing the sulfates in Hanks' balanced salt solution (HBSS) such ionization is increased; finally, the proteins incorporated to the (HBSS) showed a reduction of the silver release, which also explains the low ionization in the culture medium (tryptic soy broth) that contains high quantities of proteins.

Análise de ácidos graxos por eletroforese capilar utilizando detecção condutométrica sem contato

This article describes a novel approach to the separation of fatty acids ranging from 8 to 20 carbons using capillary electrophoresis with contactless conductivity detection. Complete separation of nine linear chain fatty acids (from C8:0 to C20:0) was achieved in 15 min under normal polarity operation. Limits of detection ranged from 35 to 319 µmol L-1 for C20:0 to C8:0, respectively. The optimized running electrolyte composition was 5.0 mmol L-1 phosphate buffer at pH 7, 4.0 mmol L-1 dimethyl-b-cyclodextrin, 2.0 mmol L-1 trimethyl-b-cyclodextrin, acetonitrile 50% (v/v), and methanol 20% (v/v). The applicability of the separation system was demonstrated by the analysis of coconut vegetable oil.

Importance du stress oxydant dans le diabète secondaire à la fibrose kystique

Introduction : La fibrose kystique (FK) est une maladie génétique mortelle qui touche principalement les poumons et l’appareil digestif. Elle est causée par des mutations sur le gène codant la protéine du CFTR, un canal chlore exprimé à la surface des organes à sécrétions exocrines. Les fonctions principales du CFTR sont les suivantes: 1) la régulation de l’homéostasie ionique des sécrétions; 2) le maintien de la fluidité des sécrétions et; 3) le transport du glutathion. Le dysfonctionnement de la protéine du CFTR rend les sécrétions visqueuses et épaisses, avec des phénomènes obstructifs qui sont responsables de l’apparition de fibrose au sein des divers organes. Dans le poumon, l’accumulation du mucus épais rend difficile l’élimination des bactéries inhalées, ces dernières établissent alors des cycles d’infection qui endommagent les tissus pulmonaires à travers des processus inflammatoires. Dans le tube digestif, le mucus épais entrave l’absorption d’une quantité suffisante d’éléments nutritifs incluant les principaux antioxydants. L’infection et l’inflammation des poumons favorisent l’apparition d’un stress oxydant qui détruit davantage le tissu pulmonaire. Le déficit en glutathion, probablement lié au dysfonctionnement de la proteine du CFTR, et la malabsorption des antioxydants favorisent l’augmentation du stress oxydant. Une augmentation du stress oxydant a été démontrée au cours du diabète et les produits dérivés du stress oxydant ont été mis en évidence dans la pathogenèse des complications associées au diabète. Une augmentation du stress oxydant a également été montrée durant la FK, mais sans pour autant expliquer la survenue du diabète secondaire à la FK dont la prévalence augmente sans cesse. Objectifs : Notre étude consiste à évaluer l’impact du stress oxydant dans les anomalies du métabolisme du glucose durant la FK, et à étudier son rôle dans les mécanismes de sécrétion d’insuline induite par le glucose. Pour ce faire, nous avons déterminé l’impact de la peroxydation lipidique sur la tolérance au glucose et la défense antioxydante globale, in vivo, chez des patients FK présentant une altération du métabolisme du glucose. De plus, nous avons évalué le rôle du stress oxydatif sur la synthèse et la sécrétion d’insuline, in vitro, dans les cellules pancréatiques βTC-tet. Résultats : Dans l’étude in vivo, nous avons démontré que l’intolérance au glucose et le diabète étaient associés à une augmentation de la peroxydation lipidique, traduite par la hausse des niveaux sanguins de 4-hydroxynonenal lié aux protéines (HNE-P). La défense antioxydante évaluée par la mesure du glutathion sanguin démontre que les niveaux de glutathion oxydé restent également élevés avec l’intolérance au glucose. Dans l’étude in vitro, nos résultats ont mis en évidence que l’exposition de la cellule βTC-tet au stress oxydant: 1) induit un processus de peroxydation lipidique; 2) augmente la sécrétion basale d’insuline; 3) diminue la réponse de la sécrétion d’insuline induite par le glucose; et 4) n’affecte que légèrement la synthèse de novo de l’insuline. Nous avons aussi démontré que les cellules pancréatiques βTC-tet résistaient au stress oxydant en augmentant leur synthèse en glutathion tandis que la présence d’un antioxydant exogène pouvait restaurer la fonction sécrétoire de ces cellules. Conclusion : Le stress oxydant affecte le fonctionnement de la cellule pancréatique β de plusieurs manières : 1) il inhibe le métabolisme du glucose dont les dérivés sont nécessaires à la sécrétion d’insuline; 2) il active la voie de signalisation impliquant les gènes pro-inflammatoires et; 3) il affecte l’intégrité membranaire en induisant le processus de peroxydation lipidique.

Tamizaje neonatal para fibrosis quística en una muestra de la ciudad de Bogotá

La Fibrosis Quística es la enfermedad autosómica recesiva mas frecuente en caucásicos. En Colombia no se conoce la incidencia de la enfermedad, pero investigaciones del grupo de la Universidad del Rosario indican que podría ser relativamente alta. Objetivo: Determinar la incidencia de afectados por Fibrosis Quística en una muestra de recién nacidos de la ciudad de Bogotá. Metodología: Se analizan 8.297 muestras de sangre de cordón umbilical y se comparan tres protocolos de tamizaje neonatal: TIR/TIR, TIR/DNA y TIR/DNA/TIR. Resultados: El presente trabajo muestra una incidencia de 1 en 8.297 afectados en la muestra analizada. Conclusiones: Dada la relativamente alta incidencia demostrada en Bogotá, se justifica la implementación de Tamizaje Neonatal para Fibrosis Quística en Colombia.

Multivariant optimization, validation, and application of capillary electrophoresis for simultaneous determination of polyphenols and phenolic acids in Brazilian wines

A method for the simultaneous determination of the stilbene resveratrol, four phenolic acids (syringic, coumaric, caffeic, and gallic acids), and five flavonoids (catechin, rutin, kaempferol, myricetin, and quercetin) in wine by CE was developed and validated. The CE electrolyte composition and instrumental conditions were optimized using 2(7-3) factorial design and response surface analysis, showing sodium tetraborate, MeOH, and their interaction as the most influential variables. The optimal electrophoretic conditions, minimizing the chromatographic resolution statistic values, consisted of 17 mmol/L sodium tetraborate with 20% methanol as electrolyte, constant voltage of 25 kV, hydrodynamic injection at 50 mbar for 3 s, and temperature of 25 degrees C. The R(2) values for linearity varied from 0.994 to 0.999; LOD and LOQ were 0.1 to 0.3 mg/L and 0.4 to 0.8 mg/L, respectively. The RSDs for migration time and peak area obtained from ten consecutive injections were less than 2% and recoveries varied from 97 to 102%. The method was applied to 23 samples of inexpensive Brazilian wines, showing wide compositional variation.

Structural Effects of Nanotubes, Nanowires, and Nanoporous Ti/TiO2 Electrodes on Photoelectrocatalytic Oxidation of 4,4-Oxydianiline

The present work illustrates the effect of electrolyte composition on the self-organized TiO2 nanotube arrays electrode preparation. The influence of structural and surface morphology of the TiO2 nanotube-like anode on their photoactivity and photoelectrocatalytic performance was also investigated. TiO2 nanotubular array electrodes are grown by anodization of Ti foil in 0.25wt % NH4F/glycerol/water, but nanowires can be obtained in 4% HF-DMSO as supporting electrolyte, even when both are subjected to electrochemical anodization at 30V during 50 h. The morphological characteristics are analyzed by X-ray diffraction (XRD) and field emission scanning electron microscope (FEG-SEM). The electrodes were successfully applied in photoelectrocatalytic oxidation of 4,4'-oxydianiline (ODAN) in aqueous solution, as a model of a harmful pollutant. Complete removal of the aromatic amine was obtained after 3 hours of photoelectrocatalytic treatment on nanotubular arrays electrodes.

Criopreservação e fertilidade de espermatozoides do ejaculado e recuperados da cauda do epidídimo de garanhões subférteis

Pós-graduação em Medicina Veterinária - FMVZ

Formation of caries-like lesions in vitro on the root surfaces of human teeth in solutions simulating plaque fluid

Lesion formation on root surfaces of human posterior teeth was studied in acetate/lactate buffers with a background electrolyte composition based on plaque fluid analyses. Lesion depth after 28 days at 37 degrees C was measured in relation to: the presence or absence of cementum; the concentration of undissociated buffer; the presence or absence of magnesium ions at plaque fluid concentration. Each factor was evaluated at several values of -log(ion activity product for hydroxyapatite): pI(HA). Solutions were formulated to minimize variation in pH, which varied by < or =0.03 for a given comparison (individual pI(HA)) and by 0.42-0.82 over the range of pI(HA) within experiments. Lesions on surfaces from which cementum had been ground were significantly deeper than on intact surfaces, but this is considered to be due to subsurface mechanical damage and not to a solubility difference. Neither the concentration of undissociated buffer nor the presence of magnesium ions significantly affected lesion depth. Lesion depth was strongly influenced by the correlated variations in pI(HA) and pH. At pI(HA) 54 and 55, only extremely shallow lesions formed. From pI(HA) 56, lesion depth increased with increasing pI(HA). The results confirm that the solubility of the mineral of root tissues is higher than that of hydroxyapatite, but indicate that it is probably lower than suggested by Hoppenbrouwers et al. [Arch Oral Biol 1987;32:319-322]. For calcium concentrations of 3-12 mM, the critical pH for root tissue mineral was calculated as 5.22-5.66 assuming solubility equivalent to pI(HA) 54 and 5.08-5.51 assuming pI(HA) 55.

Molten carbonate fuel cells

Over the past 12 months, developments in both porous and non-porous materials for the molten carbonate fuel cell (MCFC) should lead to significantly increased stack lifetimes. Lithium-sodium carbonate is emerging as the material of choice for the electrolyte and has been tested in a 10 kW scale stack. Several new cathode materials, with lower dissolution rates in the electrolyte than state-of-the-art NiO, have been tested. However a significant finding is that the dissolution rate of NiO can also be reduced by an order of magnitude by preparing it as a functional nanomaterial. Although most developers continue to use nickel anodes, recent tests with ceramic oxides anodes open up the prospects of reduced carbon deposition and future cells running directly on dry methane. (c) 2004 Published by Elsevier Ltd.

Aspects of the prevention and repair of chloride-induced corrosion of steel in concrete

Sodium formate, potassium acetate and a mixture of calcium and magnesium acetate (CMA) have all been identified as effective de-icing agents. In this project an attempt has been made to elucidate potentially deleterious effects of these substances on the durability of reinforced concrete. Aspects involving the corrosion behaviour of embedded steel along with the chemical and physical degradation of the cementitious matrix were studied. Ionic diffusion characteristics of deicer/pore solution systems in hardened cement paste were also studied since rates of ingress of deleterious agents into cement paste are commonly diffusion-controlled. It was found that all the compounds tested were generally non-corrosive to embedded steel, however, in a small number of cases potassium acetate did cause corrosion. Potassium acetate was also found to cause cracking in concrete and cement paste samples. CMA appeared to degrade hydrated cement paste although this was apparently less of a problem when commercial grade CMA was used in place of the reagent grade chemical. This was thought to be due to the insoluble material present in the commercial formulation forming a physical barrier between the concrete and the de-icing solution. With the test regimes used sodium formate was not seen to have any deleterious effect on the integrity of reinforced concrete. As a means of restoring the corrosion protective character of chloride-contaminated concrete the process of electrochemical chloride removal has been previously developed. Potential side-effects of this method and the effect of external electrolyte composition on chloride removal efficiency were investigated. It was seen that the composition of the external electrolyte has a significant effect on the amount of chloride removed. It was also found that, due to alterations to the composition of the C3A hydration reaction products, it was possible to remove bound chloride as well as that in the pore solution. The use of an external electrolyte containing lithium ions was also tried as a means of preventing cathodically-induced alkali-silica reaction in concretes containing potentially reactive aggregates. The results obtained were inconclusive and further practical development of this approach is needed.

Cathodic protection of reinforced concrete:anodic processes in cements and related electrolytes

The nature and kinetics of electrode reactions and processes occurring for four lightweight anode systems which have been utilised in reinforced concrete cathodic protection systems have been studied. The anodes investigated were flame sprayed zinc, conductive paint and two activated titanium meshes. The electrochemical properties of each material were investigated in rapidly stirred de-oxygenated electrolytes using anodic potentiodynamic polarisation. Conductive coating electrodes were formed on glass microscope slides, whilst mesh strands were immersed directly. Oxygen evolution occurred preferentially for both mesh anodes in saturated Ca (OH)2/CaC12 solutions but was severely inhibited in less alkaline solutions and significant current only passed in chloride solutions. The main reactions for conductive paint was based on oxygen evolution in all electrolytes, although chlorides increased the electrical activity. Self-corrosion of zinc was controlled by electrolyte composition and the experimental set-up, chlorides increasing the electrical activity. Impressed current cathodic protection was applied to 25 externally exposed concrete slabs over a period of 18 months to investigate anode degradation mechanisms at normal and high current densities. Specimen chloride content, curing and reinforcement depth were also variables. Several destructive and non-destructive methods for assessing the performance of anodes were evaluated including a site instrument for quantitative "instant-off- potential measurements. The impact of cathodic protection on the concrete substrate was determined for a number of specimens using appropriate methods. Anodic degradation rates were primarily influenced by current density, followed by cemendtious alkalinity, chloride levels and by current distribution. Degradation of cementitious overlays and conductive paint substrates proceeded by sequential neutralisation of cement phases, with some evidence of paint binder oxidation. Sprayed zinc progressively formed an insulating layer of hydroxide complexes, which underwent pitting_ attack in the presence of sufficient chlorides, whilst substrate degradation was minimal. Adhesion of all anode systems decreased with increasing current density. The influence of anode material on the ionic gradients which can develop during cathodic protection was investigated. A constant current was passed through saturated cement paste prisms containing calcium chloride to central cathodes via anodes applied or embedded at each end. Pore solution was obtained from successive cut paste slices for anion and cation analyses. Various experimental errors reduced the value of the results. Characteristic S-shaped profiles were not observed and chloride ion profiles were ambiguous. Mesh anode specimens were significantly more durable than the conductive coatings in the high humidity environment. Limited results suggested zinc ion migration to the cathode region. Electrical data from each investigation clearly indicated a decreasing order of anode efficiency by specific anode material.

Contact lens interactions with the tear film

Biochemical changes brought about by the influence of the contact lens on the tear film are conveniently split into two categories. Firstly, the lens can remove or reduce the levels of specific components in the tear film, and secondly, the lens can augment the tear film, by stimulating the influx of new components or increasing the level of existing components. The most obvious tear film components for study in this context are lipids, proteins, mucins and electrolytes. The interactions are affected by the properties of the lens, the characteristics of the individual wearer and the wear schedule. An additional complicating factor is the fact that the lens is many times thicker than the tear film and any immobilised tear components will be more extensively exposed to oxygen and UV radiation than is the case in the absence of a lens. It is arguably the lipoidal components that are most markedly affected by lens wear, since their immobilisation on the lens surface markedly increases their susceptibility to autoxidative degradation. The limited information that is available highlights the importance of subject specificity and suggests that lipid oxidation phenomena are potentially important in contributing to the 'end of day' discomfort of symptomatic contact lens patients. It is clear that tear lipids, although regarded as relatively inert for many years, are now seen as a reactive and potentially important family of compounds in the search for understanding of contact lens-induced discomfort. The influence of the lens on tear proteins shows the greatest range of complexity. Deposition and denaturation can stimulate immune response, lower molecular weight proteins can be extensively absorbed into the lens matrix and the lens can stimulate cascade or upregulation processes leading either to the generation of additional proteins and peptides or an increase in concentration of existing components. Added to this is the stimulating influence of the lens on vascular leakage leading to the influx of plasma proteins such as albumin. The evidence from studies of mucin expression in tears is not consistent and conclusive. This is in part because sample sources, lens materials and methods of analysis vary considerably, and in some cases the study population numbers are low. Expression levels show mucin and material specificity but clear patterns of behaviour are elusive. The electrolyte composition of tears is significantly different from that of other body fluids. Sodium and potassium dominate but potassium ion concentrations in tears are much higher than in serum levels. Calcium and magnesium concentrations in tears are lower than in serum but closer to interstitial fluids. The contact lens provides the potential for increased osmolarity through enhanced evaporation and differential electrolyte concentrations between the anterior and posterior tear films. Since the changes in ocular biochemistry consequent upon contact lens wear are known to be subject-dependent - as indeed is wearer response to the lens - pre-characterisation of individual participant tear chemistry in clinical studies would enhance understanding of these complex effects. © 2013 Elsevier Ltd.

Randomized, Double-Blind Trial of the Effect of Fluid Composition on Electrolyte, Acid-Base, and Fluid Homeostasis in Patients Early After Subarachnoid Hemorrhage.

Hyper- and hyponatremia are frequently observed in patients after subarachnoidal hemorrhage, and are potentially related to worse outcome. We hypothesized that the fluid regimen in these patients is associated with distinct changes in serum electrolytes, acid-base disturbances, and fluid balance.