O eletrólito suporte e suas múltiplas funções em processos de eletrodo

The aim of this work is to present the principal properties and applications of supporting electrolytes (SE) to students, teachers and researchers interested in electrode processes. Different aspects are discussed including the importance of SE in maintaining constant the activity coefficients and the diffusion coefficients and reducing the transport number of electroactive species. Its effect on the electrochemical kinetic parameters is also presented.

Uso de membranas de Nafion para a construção de sensores ópticos para medidas de pH

The behaviour of Nafion® polymeric membranes containing acid-base dyes, bromothymol blue (BB) and methyl violet (MV), were studied aiming at constructing an optical sensor for pH measurement. BB revealed to be inadequate for developing sensing phases due to the electrostatic repulsion between negative groups of their molecules and the negative charge of the sulfonate group of the Nafion®, which causes leaching of the dye from the membrane. On the other hand, MV showed to be suitable due to the presence of positive groups in its structure. The membrane prepared from a methanolic solution whose Nafion®/dye molar ratio was 20 presented the best analytical properties, changing its color from green to violet in the pH range from 0.6 to 3.0. The membrane can be prepared with good reproducibility, presenting durability of ca. 6 months and response time of 22 s, making possible its use for pH determination in flow analysis systems.

Estudo da labilidade de Cu(II), Cd(II), Mn(II) e Ni(II) em substâncias húmicas aquáticas utilizando-se membranas celulósicas organomodificadas

In this work commercial filters papers were organomodified with tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (3-APTS), aiming at the development of a new analytical procedure for in-situ speciation of labile and inert metal species in aquatic systems. Parameters that exert influence on the metal lability such as pH, chelating time, concentration and characteristics of the organic matter were studied in the laboratory using tests for metal recuperation. The results showed slower kinetics for Cu ion than for Ni, Mn and Cd in the absence of aquatic humic substances (AHS). The relative lability observed for complexed metals in aquatic humic substances using organomodified filter papers was Cu>>Cd>Ni>Mn. The pH values, structural characteristics and concentration of AHS exert strong influence on the lability of the metals. The results obtained showed that the utilization of organomodified filter papers can be an interesting and promising alternative for in situ characterization of metal lability in aquatic systems.

Comparação do desempenho da lipase de candida rugosa imobilizada em suporte híbrido de polissiloxano-polivinilálcool empregando diferentes metodologias

The efficiency for immobilizing microbial Candida rugosa lipase on a hybrid matrix of polysiloxane polyvinyl alcohol, by adsorption, covalent coupling and encapsulation was compared. The activities of immobilized derivatives were evaluated using p-nitrophenylpalmitate (hydrolysis) and butyric acid and butanol (esterification) as substrates. Operational stability and storage tests were also performed. Among the procedures tested, the proposed matrix was efficient for immobilizing C. rugosa lipase by adsorption and covalent coupling techniques and unsuitable for encapsulation purposes. The results reveal that better catalytic properties in both aqueous and organic media were demonstrated by the covalent coupling POS-PVA immobilized lipase, including also satisfactory half-life and good storage stability.

Anestésicos locais: interação com membranas biológicas e com o canal de sódio voltagem-dependente

Many theories about the mechanism of action of local anesthetics (LA) are described in the literature. Two types of theories can be distinguished: those that focus on the direct effects of LA on their target protein in the axon membranes, i.e. the voltage-gated sodium channel and the ones that take into account the interaction of anesthetic molecules with the lipid membrane phase for the reversible nerve blockage. Since there is a direct correlation between LA hydrophobicity and potency, it is crucial to take this physico-chemical property into account to understand the mechanism of action of LA, be it on the sodium channel protein, lipid(s), or on the whole membrane phase.

Efeitos da incorporação de peneiras moleculares 3A, 4A, 5A e 13X em membranas compósitas de quitosana/poli(vinil álcool)

The composite membranes prepared via incorporation of 12.5% of molecular sieves 3A, 4A, 5A and 13X into chitosan/poly(vinyl alcohol) (1:1). The composite membranes were immersed in the cross-linker sulfuric acid in order to acquire high proton conductivity for applications in electrolytes in PEMCF and DMF. The influence of the molecular sieves on the structural, optical, thermal, mechanical, morphologic and protonic conductivity properties and water/methanol swelling degree of membranes were investigated.

Preparação de membranas de acetato de celulose organomodificadas para adsorção dos íons Cu(II), Cd(II), Mn(II) e Ni(II)

Cellulose acetate polymeric membranes had been prepared by a procedure of two steps, combining the method of phase inversion and the technique of hydrolysis-deposition. The first step was the preparation of the membrane, and together was organomodified with tetraethylortosilicate and 3-aminopropyltrietoxysilane. Parameters that exert influence in the complexation of the metallic ion, as pH, time of complexation, metal concentration, had been studied in laboratory using tests of metal removal. The membranes had presented resistance mechanics and reactivity to cations, being able to be an alternative for the removal, daily pay-concentration or in the study of the lability of metals complexed.

Determinação de constituintes químicos em madeira de eucalipto por Pi-CG/EM e calibração multivariada: comparação entre redes neurais artificiais e máquinas de vetor suporte

Multivariate models were developed using Artificial Neural Network (ANN) and Least Square - Support Vector Machines (LS-SVM) for estimating lignin siringyl/guaiacyl ratio and the contents of cellulose, hemicelluloses and lignin in eucalyptus wood by pyrolysis associated to gaseous chromatography and mass spectrometry (Py-GC/MS). The results obtained by two calibration methods were in agreement with those of reference methods. However a comparison indicated that the LS-SVM model presented better predictive capacity for the cellulose and lignin contents, while the ANN model presented was more adequate for estimating the hemicelluloses content and lignin siringyl/guaiacyl ratio.

Aplicação de quitosana como suporte para a imobilização de enzimas de interesse industrial

Chitosan, poly[β-(1-4)-linked-2-amino-2-deoxy-D-glucose], is the N-deacetylated product of chitin which is a major component of arthropod and crustacean shells such as lobsters, crabs, shrimps, and cuttlefishes. In addition, chitosan has many significant biological and chemical properties such as biodegradability, biocompatibility and bioactivity as well as polycationic properties. Thus, it has been widely used in many industrial and biomedical applications including wastewater treatment, chromatographic support, carriers for controlled drug delivery and enzyme immobilization. This review is an insight into the exploitation of utilization of chitosan based-supports in different geometrical configurations on the immobilization of enzymes by different protocols for further application in biotransformation reactions.

Membranas de condução mista iônica e eletrônica (miec): composições, preparação e desempenho

This paper presents a review of different chemical compositions that are used in the production of mixed ionic-electronic conducting membranes with the perovskite structure. In these dense membranes, oxygen from the air is permeated through ionic and electronic processes, and high oxygen permeation fluxes are observed at high temperatures (800-900 ºC). Various membranes were compared for their performance and properties after being synthesized by different methods.

Nanopartículas de poli-hidroxibutirato-co-valerato como suporte para a imobilização da lipase de Candida antarctica fração B

This work evaluates the immobilization of Candida antarctica lipase (Fraction B) using poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanoparticles as support. The effects of immobilization time (30-150 min) and pH (5-10) on lipase loading were evaluated. The stability of the immobilized enzyme towards temperature (40, 60, and 80 ºC), reuse and storage (at 4 ºC) were also determined. Furthermore, to assess its potential application in a system of interest, the immobilized lipase was used as a catalyst in the esterification of geraniol with oleic acid. The results indicated a time of 120 minutes and pH of 7 as optimal for immobilization. A 21 hour exposure of the PHBV-lipase derivative to 60 ºC showed a 33% reduction of the initial activity while storage at 4 ºC led to a residual activity (5% of the original activity). The derivative was used without significant loss of activity for 4 successive cycles. The use of the immobilized lipase as a catalyst in the production of geranyl oleate led to about 88% conversion of the initial reactants to products.

Caracterização de membranas assimétricas de acetato de celulose produzidas a partir do aproveitamento do resíduo da palha de milho para uso em ultrafiltração

Cellulose acetates (CA) with different degrees of acetylation were synthesized from cellulose extracted from corn stover. Membranes were prepared for the ultrafiltration process with pure polymers and blend form of CA utilizing a dioxane/acetone system. The membranes were characterized according to their transport properties. The blend form materials presented the best results for application in ultrafiltration experiments. M-TAC/DAC (corn stover triacetate and diacetate) and M-TAC/DAC-Rho (corn stover triacetate and Rhodia diacetate) presented rejection to egg albumin protein of 87.39% and 80.50%, respectively. Thus, MWCO of 45 kDa was determined for these materials.

PREPARAÇÃO E CARACTERIZAÇÃO DE MEMBRANAS DE CELULOSE REGENERADA A PARTIR DA CELULOSE EXTRAÍDA DE RESÍDUOS AGROINDUSTRIAIS PARA APLICAÇÃO EM PROCESSOS DE SEPARAÇÃO

The aim of this study was to produce membranes using the adapted cuprammonium method. The cellulose utilized was obtained from recycled agroindustrial residues: sugarcane bagasse, corn stover and soybean hulls. The levels of Cu (II) ions in regenerated cellulose membranes produced with cellulose from bagasse, corn stover and soybean hulls were 0.0236 wt%, 0.0255 wt% and 0.0268 wt%, respectively. These levels were approximately 15 times lower than those observed in previous studies (0.3634 wt%). Cellular viability data show that membranes produced from bagasse cellulose do not present toxicity to the cellular cultures studied. These results demonstrate an evolution in production of regenerated cellulose membranes from agroindustrial residues mainly due to a decrease in the Cu (II) ions level, showing the possibility of application of these systems with improved membranes processing.

Conhecimentos em atenção pré-hospitalar e suporte básico de vida por estudantes recém-ingressos de medicina

Reconhecer sinais iminentes de morte em vítimas de trauma, acidente vascular encefálico e acidentes domésticos constitui parte do Suporte Básico de Vida (SBV), ação fundamental à prática médica. Objetivou-se investigar o conhecimento em manobras no SBV e urgências domiciliares entre estudantes recém-ingressos de Medicina. Estudo quantitativo, analítico e quase-experimental, realizado com estudantes do primeiro semestre 2012.2 do curso de Medicina de universidade pública do Ceará - Campus Cariri em Barbalha (CE), Brasil. Os dados foram coletados em fases. Na primeira etapa, aplicou-se um questionário com 40 perguntas de múltipla escolha sobre manobras de atendimento pré-hospitalar em SBV como pré-teste de forma presencial. A segunda etapa consistiu num minicurso de 20 horas com profissional treinado. Na terceira fase, utilizou-se pós-teste para comparar as questões acertadas antes e depois do curso. Quanto aos conhecimentos adquiridos, houve acréscimo nos temas traumatismo raquimedular, liberação de vias aéreas e cuidados domiciliares. Há necessidade de realizar cursos com maior carga horária para fundamentar uma prática médica centrada nos temas de menor rendimento dos estudantes.

Metodologia baseada em técnicas de mineração de dados para suporte à certificação de raças de ovinos

RESUMO O objetivo deste trabalho foi desenvolver uma metodologia baseada em técnicas de mineração de dados para selecionar os principais marcadores SNP (Single Nucleotide Polymorphism) para as raças de ovinos: Crioula, Morada Nova e Santa Inês. Os dados utilizados foram obtidos do Consórcio Internacional de Ovinos e são compostos por 72 animais das raças citadas, e cada animal possui 49.034 marcadores SNP. Considerando que o número de atributos (marcadores) é muito maior que o de observações (animais), foram aplicadas as técnicas de predição LASSO (Least Absolute Shrinkage and Selection Operator), Random Forest e Boosting para a geração de modelos preditivos que incorporam métodos de seleção de atributos. Os resultados revelaram que os modelos preditivos selecionaram os principais marcadores SNP para identificação das raças estudadas. O modelo LASSO selecionou um total de 29 marcadores relevantes. A partir dos modelos Random Forest e Boosting, foram obtidos 27 e 20 marcadores importantes, respectivamente. Por meio da intersecção dos modelos gerados, identificou-se um subconjunto de 18 marcadores com maior potencial de identificação das raças.