Baterias de níquel-hidreto metálico, uma alternativa para as baterias de níquel-cádmio

Nickel metal hydride (Ni-MH) batteries have emerged as an alternative for replacement of nickel-cadmium batteries, because of their more environmental compatibility and high energy capacity. In this article, we described the properties and applications for Ni-MH batteries, giving some emphasis on the metal-hydride electrode, including the description of composition, the charge storage capacity and the discharge profile. The key component of the nickel-metal hydride electrode is a hydrogen storage alloy whose composition is formulated to obtain a high stable material over a large number of charge-discharge cycles.

Qualidade de medições em química analítica. Estudo de caso: determinação de cádmio por espectrofotometria de absorção atômica com chama

Calculation of uncertainty of results represents the new paradigm in the area of the quality of measurements in laboratories. The guidance on the Expression of Uncertainty in Measurement of the ISO / International Organization for Standardization assumes that the analyst is being asked to give a parameter that characterizes the range of the values that could reasonably be associated with the result of the measurement. In practice, the uncertainty of the analytical result may arise from many possible sources: sampling, sample preparation, matrix effects, equipments, standards and reference materials, among others. This paper suggests a procedure for calculation of uncertainties components of an analytical result due to sample preparation (uncertainty of weights and volumetric equipment) and instrument analytical signal (calibration uncertainty). A numerical example is carefully explained based on measurements obtained for cadmium determination by flame atomic absorption spectrophotometry. Results obtained for components of total uncertainty showed that the main contribution to the analytical result was the calibration procedure.

Estudos da deposição em subtensão de cádmio sobre ouro policristalino na presença de diferentes ânions co-adsorvidos

Cadmium UPD on Au was studied by voltammetric and microgravimetric measurements. In the oxide formation/reduction potential region, a mass increasing/decreasing of 32 ng cm-2 was associated to incorporation/elimination of one oxygen per active site. The modifications promoted in the voltammetric and mass profiles by 10-5 M Cd(ClO4)2 are restricted to potentials more negative than 0.4 V. After a 120 s potential delay at 0.05 V, the positive sweep reveals an anodic peak with charge of 40 muC cm-2 and mass decrease of 22 ng cm-2, associated to Cd ads dissolution. Sulphate or chloride was added to the solution without significant influence, due to the low coverage with Cd or anions.

Deposição eletrolítica catódica e anódica simultâneas para minimizar interferências de cobre e chumbo na determinação espectrofotométrica de cádmio em água e alimentos via reação com Verde de Malaquita e iodeto

Simultaneous electrolytic deposition is proposed for minimization of Cu2+ and Pb2+ interferences on automated determination of Cd2+ by the Malachite Green-iodide reaction. During electrolysis of sample in a cell with two Pt electrodes and a medium adjusted to 5% (v/v) HNO3 + 0.1% (v/v) H2SO4 + 0.5 mol L-1 NaCl, Cu2+ is deposited as Cu on the cathode, Pb2+ is deposited as PbO2 on the anode while Cd2+ is kept in solution. With 60 s electrolysis time and 0.25 A current, Pb2+ and Cu2+ levels up to 50 and 250 mg L-1 respectively, can be tolerated without interference. With on-line extraction of Cd2+ in anionic resin minicolumn, calibration graph in the 5.00 - 50.0 µg Cd L-1 range is obtained, corresponding to twenty measurements per hour, 0.7 mg Malachite Green and 500 mg KI and 5 mL sample consumed per determination. Results of the determination of Cd in certified reference materials, vegetables and tap water were in agreement with certified values and with those obtained by GFAAS at 95% confidence level. The detection limit is 0.23 µg Cd L-1 and the RSD for typical samples containing 13.0 µg Cd L-1 was 3.85 % (n= 12).

Pré-concentração de chumbo e cádmio em um sistema de micro extração líquido-líquido e determinação por espectrometria de absorção atômica com chama

A method for determination of lead and cadmium in aqueous samples using solvent microextraction and dithizone as complexing agent with FAAS was developed. Solvent microextraction parameters were optimized. The effect of foreign ions on the extraction yields was studied. The extraction was carried out until the aqueous to organic phase ratio achieved a 250 fold preconcentration of metals. For preconcentration times of 4 min the 3sigma detection limits, relative standard deviations (n=7) and linear calibration ranges were 1.6 mug L-1, 5.8% and 10.0 -- 80.0 mug L-1 for lead and 11.1 ng L-1, 5.9% and 0.3 -- 3.0 mug L-1 for cadmium, respectively. The solvent microextraction procedure presented here was applied to the determination of lead and cadmium in natural waters.

L'aplicació de l'art teràpia amb nens hospitalitzats amb càncer, per tal de millorar el seu estat d'ànim, disminuir l'ansietat i l'estrès

Amb aquest projecte d'intervenció ens agradaria poder posar sobre la taula que l'art teràpia és una disciplina, una tècnica dins de la psicologia, que aporta beneficis psico-emocionals als usuaris que la reben; en el cas d'aquest projecte amb nens i adolescents amb càncer a l'Hospital Sant Joan de Déu.

Novos produtos naturais capazes de atuar na estabilização de microtúbulos, um importante alvo no combate ao câncer

Microtubules are involved in many aspects of cellular biology and represent an important target of anticancer chemotherapeutics. In the past five years, novel natural products such as epothilones, discodermolide, sarcodictyin, eleutherobin, and laulimalide, all of which have biological activities similar to those of paclitaxel (Taxolâ), have been discovered. Taxolâ is an important antitumor drug approved by the FDA for the treatment of ovarian, breast and non-small-cell lung carcinomas and became the first natural product described that stabilized microtubules avoiding the cellular replication. The present article reports new natural products that are able to act on the stabilization of microtubules.

Comportamento da atomização eletrotérmica de ouro, prata, bismuto, cádmio, chumbo e estanho em soluções aquosas e em etanol, a partir de diferentes superfícies atomizadoras

The atomization behavior of Au, Ag, Bi, Cd, Pb, and Sn from pyrolitic graphite coating (L'vov platform) with the use Pd and Mg solutions, and zirconium coated platform with the analytes in nitric acid 0.2% v/v and in ethanol was investigated. In ethanol medium, the sensitivity gain was three-fold for Bi and Cd using Zr as modifier. Without modifier, the ethanol medium is appropriate only for Au and Cd. In nitric acid medium, the Zr coated platform elevates sensitivity at least two-fold for Bi and Cd. The method was applied to the determination of Ag, Au and Bi of certified steel samples, after on-line preconcentration, sorption on a minicolumn filled with C-18 bonded to silica gel and elution with ethanol. The concentrations obtained agreed with the recommended values.

Câncer e agentes antineoplásicos ciclo-celular específicos e ciclo-celular não específicos que interagem com o DNA: uma introdução

The chemotherapy agents against cancer may be classified as "cell cycle-specific" or "cell cycle-nonspecific". Nevertheless, several of them have their biological activity related to any kind of action on DNA such as: antimetabolic agents (DNA synthesis inhibition), inherently reactive agents (DNA alkylating electrophilic traps for macromolecular nucleophiles from DNA through inter-strand cross-linking - ISC - alkylation) and intercalating agents (drug-DNA interactions inherent to the binding made due to the agent penetration in to the minor groove of the double helix). The earliest and perhaps most extensively studied and most heavily employed clinical anticancer agents in use today are the DNA inter-strand cross-linking agents.

Desigualdades geográficas en mortalidad e incidencia por cáncer de laringe en varones: factores socioeconómicos y ambientales

Diversos estudios sugieren la relación entre menor nivel socioeconómico y factores ambientales con mayor riesgo de cáncer. El objetivo del trabajo es identificar desigualdades geográficas en mortalidad e incidencia por cáncer de laringe (CL) en varones y su asociación con factores de privación y ambientales en el marco del proyecto MEDEA. Métodos: Estudio ecológico cuya población de referencia fueron loshombres residentes en el municipio de Zaragoza. El periodo de estudio fue1996-2003. Las defunciones fueron obtenidas del Registro de Mortalidad de Aragón, los casos incidentes del Registro Poblacional de Cáncer de Zaragoza y los datos socioeconómicos del Censo de 2001. Se utilizó la base de datos del Registro Europeo de Emisiones Contaminantes en lalocalización de posibles industrias contaminantes. Para cada sección censal(SC) se obtuvo un índice de privación mediante análisis de componentesprincipales. Se obtuvieron las Razones de Mortalidad e Incidencia Estandarizadas suavizadas aplicando metodología bayesiana.Resultados: Se analizaron 211 defunciones y 569 casos incidentes, con SC conocida, que correspondieron al 95% del total de casos registrados de mortalidad y el 97,8% de incidencia. Las SC que se encontraban enel cuartil superior, mayor índice de privación, tuvieron significativamentemayor riesgo, tanto de mortalidad (2,74 veces) como de incidencia (1,66 veces). Sin embargo no se encontró asociación estadísticamente significativa con los indicadores ambientales utilizados. Conclusiones: Las SC con menor nivel económico presentan mayor riesgo de mortalidad e incidencia por CL. La posible exposición a focos industriales contaminantes no explica la variabilidad geográfica observada

El secret del càncer més resistent

En la lluita contra el càncer, la recerca de nous fàrmacs cada cop més efectius i específics sovint troba un escull important: en molts tumors hi ha una petita fracció de cèl·lules resistents, que no es poden eliminar fàcilment. Tanmateix, el principal problema no és aquest, sinó que, a més, acostumen a respondre als fàrmacs incrementant la taxa de proliferació i la capacitat de fer metàstasi. Això fa que alguns tractaments no acabin de ser del tot efectius a llarg termini, per la presència cada cop més nombrosa i dispersa d'aquestes cèl·lules canceroses resistents. L'equip de recerca de Joan Massagué, al Memorial Sloan Kettering Cancer Center de Nova York, ha demostrat que aquest efecte a llarg termini induït pels mateixos fàrmacs és perquè les cèl·lules sensibles, abans de morir, preparen un ambient molt favorable per a les resistents.

Pré-concentração de cádmio com Saccharomyces cerevisiae e determinação em águas fluviais usando espectrometria de emissão óptica com plasma indutivamente acoplado

A preconcentration method based on the use of Saccharomyces cerevisiae as sorbent material is proposed for the determination of Cd(II) in river water. The solid phase extraction was performed in batch mode and the determination of the analyte in the solid phase was easily carried out by introducing a slurry of the yeast (0.0625 g / 2.5 mL) directly into the ICP OES. A limit of detection of 0.11 µg L-1 and a sample throughput in the range of 4 - 54 sample h-1 were obtained. Determinations of cadmium in a certified sample and in real river water samples were in excellent agreement with the expected values.

Recuperação de cádmio de baterias níquel-cádmio via extração seletiva com tributilfosfato (TBP)

This work describes a recovery process of cadmium from spent nickel-cadmium batteries by a new hydrometallurgical route based on the selective extraction in hydrochloric acid medium with tributylphosphate (TBP), alone or dissolved in kerosene. The best results were obtained when TBP concentration was at least 75 vol%. Nickel extraction was negligible under these conditions. It was isolated after processing the rafinate through an anionic ion-exchange column. Final wastes generated are basically sodium chloride solutions, with no turbidity, color or heavy metals present in significant amounts.

Evaluación de dos estrategias de cribado de cáncer colorrectal: Test inmunológico versus test bioquímico. Cataluña, 2008-2010

Fundamento: El objetivo del estudio fue evaluar el cambio de estrategia de cribado (test inmunológico cuantitativo) en un programa poblacional de detección precoz de cáncer colorrectal (CCR) en Cataluña. Métodos: La cuarta ronda del programa de cribado de CCR en Hospitalet de Llobregat se implementó en 2008-2010. Se ofreció un test bioquímico a 50.227 individuos y uno inmunológico cuantitativo a 12.707 individuos. Se analizaron diferencias en las dos estrategias de cribado respecto a variables de aceptabilidad (entre participación, abandonos y adherencia a la colonoscopia), de precisión diagnóstica (valor predictivo positivo y tasas de detección), de resultados (tamaño y localización de lesiones, estadio de los cánceres detectados) y de recursos (número necesario de colonoscopias e intervalo de tiempo entre el resultado positivo del test y la colonoscopia). Resultados: La participación en el cribado fue superior entre los individuos que utilizaron el test inmunológico (OR: 1,35; IC95%:1,27-1,42). Las tasas de detección fueron superiores para el test inmunológico destacando la de adenomas de alto riesgo (26,7 vs 3,0 ). El valor predictivo positivo para adenomas de alto riesgo fue del 45,0% y del 46,9% en el inmunológico y el guayaco, respectivamente. El número de colonoscopias necesarias para detectar un cáncer fue de casi el doble que en el guayaco (13,6 vs 7,4). Conclusiones: El test inmunológico es una buena estrategia de cribado especialmente sensible para la detección de adenomas de alto riesgo. Sin embargo, requiere realizar un gran número de colonoscopias y por ello se debe disponer de los recursos y medios necesarios.

Caracterização de subproduto da indústria de alumínio e seu uso na retenção de cádmio e chumbo em sistemas monoelementares

The present work aimed to characterize an aluminum industry by-product in natura (L.A. nat) and after phosphate and thermal pretreatments; evaluate the adsorption/desorption capacity of Cd and Pb by this L.A. nat form and after the aforementioned pretreatments, comparing them with an in natura iron mining by-product (L.F. nat). The L.A. nat presented a high pH as well as a high Na concentration and also an oxide-rich mineralogy. Pretreatment of the by-product had no significant effect upon Cd and Pd adsorption/desorption. The L.A. nat performed better than the L.F. nat as an Cd and Pb adsorbent.