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Anomalous content of chromium in a Cretaceous sandstone aquifer of the Bauru Basin, state of Sao Paulo, Brazil

Bertolo, Reginaldo Antonio; Bourotte, Christine Laure Marie; MARCOLAN, Leonardo; Oliveira, Sonia Maria Barros de; Hirata, Ricardo
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.13%
Anomalous and natural concentrations of Cr(6+), occasionally exceeding the permitted limit for human consumption (0.05 mg/L), have been detected in groundwater in the northwestern region of the state of Sao Paulo. As part of a water-rock interaction investigation, this article describes the chemical and mineralogical characterization of rock samples taken from boreholes in the municipality of Urania, with the objective of identifying Cr-bearing minerals and determining how chromium is associated with these minerals. Rock sample analysis were performed using X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, electron microprobe and sequential extraction techniques. Chemical analyses indicated that the quartzose sandstones show a geochemical anomaly of chromium, with an average content of 221 ppm, which is higher than the reported chromium content of generic sandstones (35 ppm). Diopside was identified as the primary Cr-bearing mineral potentially subject to weathering processes, with a chromium content of up to 1.2% as Cr(2)O(3). Many of the diopside grains showed dissolution features, confirming the occurrence of weathering. Sequential extraction experiments indicated that 99.3% of the chromium in samples is tightly bonded to minerals...

"Estudo espectrofotométrico do sistema crômio(III)/azoteto e seu aproveitamento analítico". ; "Spectrophotometric study of chromium(III)/azide system and your analytical application".

Lourenço, Leandro Maranghetti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/02/2004 PT
Relevância na Pesquisa
37.16%
Na área de Química, uma das linhas mais tradicionais de pesquisa envolve o estudo de formação de complexos. Estes trabalhos são realizados de modo sistemático em nossos laboratórios, geralmente envolvendo cátions de metais de transição com vários ligantes (haletos, pseudo-haletos e carboxilatos). A intensa coloração desenvolvida pela maioria dessas reações de complexação, entre um metal e um pseudo-haleto, tem motivado o desenvolvimento de novos métodos espectrofotométricos para a determinação de íons em amostras reais. Espera-se que o crômio(III), da mesma forma que outros metais de transição, como o ferro, níquel e cobalto, forme complexos com o pseudo-haleto denominado azida ou azoteto (N3-). Desta forma, dando continuidade a esta linha de pesquisa, este trabalho teve como objetivo otimizar as condições experimentais para o sistema crômio(III)/azoteto. Diversos parâmetros como acidez, concentração de ligante, natureza e concentração de solvente, bem como o efeito da temperatura, foram investigados. Reunidas as melhores condições (otimização), montou-se o método analítico que possibilita a determinação do metal. As condições ideais empregadas foram: concentração analítica de ligante e ácido perclórico de 493 e 12...

Efeitos do cobre e cromo na comunidade zooplanctônica : um estudo experimental em mesocosmos; Effects of copper and chromium on the zooplankton community : a mesocosms experimental study

Gusmão, Luiz Felipe Mendes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2004 PT
Relevância na Pesquisa
37.1%
O crescente desenvolvimento industrial e urbano tem acarretado a introdução de grandes quantidades de metais nos ecossistemas aquáticos, expondo, potencialmente, sua biota e toda a cadeia alimentar que dela se origina à contaminação por esses elementos. Muitos estudos sobre o comportamento dos metais no meio aquático vêm sendo desenvolvidos, pois os metais representam um problema ambiental por sua persistência no ambiente e não biodegradabilidade. No entanto, pouco se conhece sobre seus efeitos ecológicos na estrutura e função das comunidades aquáticas. O presente trabalho, neste sentido, visa contribuir para um melhor conhecimento desses efeitos sobre a comunidade zooplanctônica em experimentos de campo que reproduzem, com maior fidelidade, o ecossistema. O objetivo deste trabalho foi avaliar os efeitos dos metais cromo e cobre sobre a estrutura da comunidade zooplanctônica de espécies holo-zooplanctônicas em experimentos de mesocosmos realizados na Represa do Lobo-Broa (CHREA/USP). Os mesocosmos constituíram-se de três cercados de filme de PVC transparente, com volume aproximado de 5000 litros, em contato com o sedimento de fundo. Um mesocosmos foi mantido como controle, não sendo contaminado, e os outros dois foram contaminados inicialmente com as concentrações máximas permitidas pelo CONAMA/86 para o cobre (20µg/L) e cromo (40µg/L). O experimento foi realizado de 28 de Março a 30 de Abril de 2002...

Investigação hidrogeoquímica do cromo no aquífero Adamantina no município de Urânia - SP; Hydrogeochemical investigation of chromium in the Adamantina aquifer, in the municipality of Urânia - SP, Brazil

Marcolan, Leonardo Nobuo Oshima
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/12/2009 PT
Relevância na Pesquisa
37.29%
Teores anômalos de cromo hexavalente vêm sendo detectados na água subterrânea de vários municípios da região noroeste do Estado de São Paulo, sendo que em Urânia foram observadas as maiores concentrações do elemento, afetando as condições do consumo e uso humano. Estudos prévios realizados indicaram que a origem do cromo na água subterrânea é natural e proveniente de minerais com cromo no aqüífero profundo. Este projeto teve como principais objetivos: (1) a caracterização química e mineralógica da fase sólida do aqüífero profundo, realizada em testemunhos de duas sondagens profundas; (2) a caracterização da estratificação das concentrações de cromo na água subterrânea, com base na coleta e análise de amostras de água provenientes de poços de monitoramento instalados em diferentes profundidades do aqüífero; (3) a identificação dos processos hidrogeoquímicos que justificam a passagem do cromo da fase sólida para a água. Para tanto, foram realizadas análises químicas e mineralógicas por WDS, microssonda eletrônica e CTC, diversos métodos de análise química da água subterrânea, utilizados programas como o AquaChem e PHREEQc para trabalhamento do banco de dados e modelagens, além de uma grande variedade de experimentos de laboratório. As análises químicas por WDS e microssonda eletrônica indicaram concentrações de cromo de até 12.600 ppm em cristais de diopsídio...

Investigação de tratamentos alternativos de fosfatização para eliminação do níquel e cromo hexavalente; Investigation of alternative phosphating treatments for nickel and hexavalent chromium elimination

Jazbinsek, Luiz Antônio Rossi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/10/2014 PT
Relevância na Pesquisa
37.1%
O processo de fosfatização é amplamente utilizado na indústria de tratamento de superfície de metais, especialmente de placas de baixa espessura, melhorando a aderência entre a superfície do metal e o revestimento de tinta, e aumentando a durabilidade dos sistemas de pintura contra ataques corrosivos. Os fosfatos tricatiônicos contendo zinco, níquel e manganês são comumente aplicados em aço, e muito se discute sobre a substituição do níquel por outro elemento com o objetivo de obter um fosfato mais amigável ao meio ambiente, tanto em seus processos como para as pessoas envolvidas. O nióbio tem sido avaliado nesse sentido. Os impactos ambientais mais significativos dos fosfatos estão relacionados com a presença do níquel e do cromo hexavalente utilizado no processo, devido a exposição ao contato humano e a contaminação residual da água e do solo. Seguindo a linha de pesquisa que estudou a substituição do níquel por nióbio em camadas formadas sobre o aço carbono, o presente estudo avaliou e caracterizou camadas de fosfato contendo zinco, manganês e nióbio, formadas em aço galvanizado, comparando os resultados com o fosfato de zinco, manganês e níquel, bem como com o fosfato de zinco e manganês, sem a adição de nióbio. Embora o uso de cromo não seja recomendado mundialmente...

Uso de um lodo de cromo proveniente da indústria de curtume na fabricação de vidros sodo-cálcicos.; Use of tannery sludge containing chromium compounds in soda-lime glass fabrication.

Peralta, Marvin Marco Chambi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/08/2014 PT
Relevância na Pesquisa
37.1%
A indústria de produção de couro gera uma grande quantidade de resíduos com características poluentes e de elevada periculosidade, entre os quais se destacam os resíduos curtidos (aparas, serragem e pó de couro curtido) e os lodos provenientes das estações de tratamento de efluentes (lodos de cromo, lodos primários e lodos secundários). Estes resíduos possuem uma considerável quantidade de compostos de Cr(III) na sua composição, os quais, sob condições oxidantes, podem transformar-se em Cr(VI), que é altamente tóxico para animais, plantas e seres humanos. No entanto, estes resíduos constituem uma potencial fonte alternativa de cromo (tradicional pigmento industrial) que poderia ser aproveitada pela indústria de vidros e de esmaltes. No presente trabalho foi realizado o estudo das propriedades físicas e químicas de um lodo de cromo proveniente do distrito industrial do município de Franca/SP, com o intuito de avaliar a viabilidade da utilização das cinzas da incineração deste resíduo como uma potencial fonte alternativa de cromo na fabricação de vidros sodo-cálcicos coloridos para embalagens. Fluorescência de Raios X (FRX), Difração de Raios X (DRX), análises termodiferencial (DTA) e termogravimétrica (TG/DTG)...

Effect of electroless nickel interlayer on the fatigue strength of chromium electroplated AISI 4340 steel

Voorwald, H. J. C.; Padilha, R.; Costa, M. Y. P.; Pigatin, W. L.; Cioffi, M. O. H.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 695-704
ENG
Relevância na Pesquisa
37.1%
Deposition of wear-resistant hard chromium plating leads to a decrease in the fatigue strength of the base material. Despite the effective protection against wear and corrosion, fatigue life and environmental requirements result in pressure to identify alternatives or to improve conventional chromium electroplating mechanical characteristics. An interesting, environmentally safer and cleaner alternative for the replacement of hard chronic plating is tungsten carbide thermal spray coating, applied by high velocity oxyfuel (HVOF) process.To improve the fatigue strength of aeronautical steel chromium electroplated, shot peening is a successfully used method. Multiple lacer systems of coatings are considered to have larger resistance to crack propagation in comparison with simple layer.The aim of this study was to analyze the effect of nickel underplate on the fatigue strength of hard chromium plated AISI 4340 steel in two mechanical conditions: HRc 39 and HRc 52.Rotating bending fatigue tests results indicate that the clectroless nickel plating underlayer is responsible for the increase in fatigue strength of AISI 4340 steel chromium electroplated. This behavior may be attributed to the largest toughness/ductility and compressive residual stresses which...

Acute Toxicity by Water Containing Hexavalent or Trivalent Chromium in Native Brazilian Fish, Piaractus mesopotamicus: Anatomopathological Alterations and Mortality

Castro, Marcello Pardi; Moraes, Flavio Ruas de; Fujimoto, Rodrigo Yudi; Cruz, Claudinei da; Andrade Belo, Marco Antonio de; Engracia de Moraes, Julieta Rodini
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 213-219
ENG
Relevância na Pesquisa
37.18%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 05/57989-8; This study evaluated the toxicity of hexavalent and trivalent compounds of chromium to the pacu, Piaractus mesopotamicus, in acute exposures of 96 h through mortality and histopathological responses. Hexavalent potassium dichromate was more toxic than trivalent compounds of chromium chloride, chromium oxide and chromium carbochelate. Sufficient mortalities occurred only with potassium dichromate to yield an LC50 value at 124.2 mg L-1. Hexavalent chromium caused reversible and irreversible lesions, which may affect organ functionality. Histopathological evaluation showed that trivalent chromium caused lesions of lower severity. Pacu subjected to different concentrations of chromium carbochelate showed no histopathological changes in the kidneys, liver, skin and gills, being similar to those of the control fish. Among the three sources of Cr3+, only chromium chloride at 200 mg L-1 resulted in mortality, which reached 100 % within the first 18 h. These findings confirm that trivalent chromium, when administered within recommended levels, may be used safely in aquaculture.

Remoção de cromo de solução aquosa utilizando rocha sedimentar contendo zeolita; Chromium removal from aqueous soolution using zeolite bearing sedimentary rock

Sandra Maria Dal Bosco
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/08/2007 PT
Relevância na Pesquisa
37.1%
Além do enriquecimento de metais pesados em águas subterrâneas devido aos processos biogeoquímicos que ocorrem na natureza, as atividades industriais, agrícolas e outras têm contribuído para um aumento significativo nas concentrações de íons metálicos em águas, representando importantes fontes de contaminação dos corpos aquáticos e provocando preocupações principalmente quando se considera que tais íons podem ser disseminados via cadeia alimentar. O cromo, objeto deste estudo, é um dos metais potencialmente tóxicos encontrados em água subterrânea. Em águas naturais, o cromo pode ocorrer nas formas químicas Cr(III) e Cr(VI), estáveis em meio aeróbio. A ingestão de águas contaminadas com Cr(VI) pode causar vários danos à saúde como dermatite alérgica, ulcerações na pele, perfurações do septo nasal e câncer. Embora o Cr(III) seja reconhecido como menos móvel e menos tóxico que o Cr(VI), vários processos podem induzir o intercâmbio entre as espécies Cr(VI) e Cr(III) revelando a importância de prevenir concentrações excessivas de cromo em água. Neste trabalho, foi avaliado o comportamento de um arenito contendo zeólita, proveniente da Formação Corda, Bacia do Parnaíba, como trocador catiônico...

Reduction of chromium (VI) by the indirect action of Thiobacillus thioparus

Donati,E.; Oliver,C.; Curutchet,G.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2003 EN
Relevância na Pesquisa
37.13%
The microbial reduction of chromium(VI) to chromium(III) has been one of the most widely studied forms of metal bioremediation. Recently, we have found that Thiobacillus ferrooxidans and Thiobacillus thiooxidans, growing on elemental sulphur, can indirectly promote chromium(VI) reduction by producing reducing agents such as sulphite and thiosulphate, which abiotically reduce chromium(VI). Those species of Thiobacillus are acidophilic bacteria which grow optimally at pH values lower than 4. However, most of those reducing agents are stabilised at higher pH values. Thus, the present paper reports on the ability to reduce chromium(VI) using another specie of Thiobacilli, Thiobacillus thioparus, which is able to grow at pH close to 7.0. T. thioparus cultures were carried out in a fermentation vessel containing medium and sulphur as the sole energy source and maintained at 30ºC and 400 rpm. The pH was adjusted to 6.0, 7.0 or 8.0 and maintained with the automatic addition of KOH. Our results show high chromium (VI) reduction values (close to 100% at the end of bacterial growth) at the three pH values. The results of these experiments are very promising for development of a microbiological process to be used in the detoxification of chromium(VI)-polluted effluents.

Cytokine detection for the diagnosis of chromium allergy

Martins,Luis Eduardo Agner Machado; Reis,Vitor Manoel Silva dos
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2013 EN
Relevância na Pesquisa
37.1%
BACKGROUND: Patch testing remains the gold standard method for the identification of the etiologic agent of allergic contact dermatitis. However, it is a subjective, time-consuming exam whose technique demands special care and which presents some contraindications, which hamper its use. In a recent study, we showed that the proliferation assay can suitably replace patch testing for the diagnosis of chromium allergy, which had been previously demonstrated only for nickel allergy. In this study, we try to refine the method by reducing the incubation period of cultures for lymphocyte proliferation assays in response to chromium. OBJECTIVE: Develop an alternative or complementary diagnostic test for chromium allergic contact dermatitis. METHODS: We compared the production of 9 cytokines (IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-17 and RANTES) between 18 chromium-allergic patients and 19 controls. RESULTS: Chromium increased the production of IFN-y, IL-5, IL-2 and IL-13 in allergic patients, but only IL-2 and especially IL-13 helped discriminate allergic patients from controls. The sensitivity, specificity and accuracy found with IL-13 were about 80%. CONCLUSIONS: IL-13 and IL-2 detection may be used to diagnose chromium allergy in 2-day cultures. However...

Effect of supplementing finishing pigs with different sources of chromium on performance and meat quality

Peres,Louise Manha; Bridi,Ana Maria; Silva,Caio Abércio da; Andreo,Nayara; Barata,Cátia Chilanti Pinheiro; Dário,Julie Gabriela Nagi
Fonte: Sociedade Brasileira de Zootecnia Publicador: Sociedade Brasileira de Zootecnia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2014 EN
Relevância na Pesquisa
37.25%
The objective was to evaluate the dietary supplementation of different sources of chromium (inorganic: chromium sulfate and chelated: chromium-methionine) during the finishing period of pigs to obtain improvements in the animal performance, and carcass and meat quality. The statistical design was randomized blocks, where 44 barrows, with an initial weight 60.49±5.12 kg, were divided into four blocks (heavier, heavy, light and lighter) according to initial weight. The experimental diets were isoenergetic and isonutrient, except for the chromium level. The treatments were divided as follows: control (without chromium), control + 200 ppb of inorganic chromium (chromium sulfate), and control + 200 ppb of chelated chromium (chromium-methionine). In the performance measures, the stall was considered the experimental unit and in the blood parameters, carcass and meat evaluations each animal constituted the experimental unit. Animals were slaughtered when they reached the final average weight of 107.23±5.23 kg. Blood samples were collected and tested for blood parameters (cholesterol, triglycerides and glucose) as well as carcass quality (hot and cold weights, yield, loin-eye area, muscle depth and backfat thickness) and meat quality (initial and final pH...

Chromium stress in plants

Panda,S.K.; Choudhury,S.
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2005 EN
Relevância na Pesquisa
37.2%
The article presents an overview of the mechanism of chromium stress in plants. Chromium is known to be a toxic metal that can cause severe damage to plants and animals. Chromium-induced oxidative stress involves induction of lipid peroxidation in plants that causes severe damage to cell membranes. Oxidative stress induced by chromium initiates the degradation of photosynthetic pigments causing decline in growth. High chromium concentration can disturb the chloroplast ultrastructure thereby disturbing the photosynthetic process. Like copper and iron, chromium is also a redox metal and its redox behaviour exceeds that of other metals like Co, Fe, Zn, Ni, etc. The redox behaviour can thus be attributed to the direct involvement of chromium in inducing oxidative stress in plants. Chromium can affect antioxidant metabolism in plants. Antioxidant enzymes like SOD, CAT, POX and GR are found to be susceptible to chromium resulting in a decline in their catalytic activities. This decline in antioxidant efficiency is an important factor in generating oxidative stress in plants under chromium stress. However, both metallothioneins and organic acids are important in plants as components of tolerance mechanisms and are also involved in detoxification of this toxic metal.

Otimização do processo de recuperação do cromo de efluentes de curtumes por microemulsões no extrator Morris; Optimisation of chromium recovery process from tanning effluent through micro emulsions in a Morris extractor

Moura, Maria Carlenise Paiva de Alencar
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Química; Pesquisa e Desenvolvimento de Tecnologias Regionais Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Química; Pesquisa e Desenvolvimento de Tecnologias Regionais
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
37.18%
The tanning industries are those which transform animal hide or skin into leather. Due to the complexity of the transformation process, greater quantities of chemicals are being used which results in the generation of effluents with residual solids. The chromium in the residual waters generated by tanning tend to be a serious problem to the environment, therefore the recovery of this metal could result in the reduction of manufacturing costs. This metal is usually found in a trivalent form which can be converted into a hexavalent compound under acidic conditions and in the presence of organic matter. The present study was carried out with the objective to recover chromium through an extraction/re-extraction process using micro emulsions. Micro emulsions are transparent and thermodynamically stable system composed of two immiscible liquids, one forming the continuous phase and the other dispersed into micro bubbles, established by an interfacial membrane formed by surface active and co-surface active molecules. The process of recovering the chromium was carried out in two stages. The first, an extraction process, where the chromium was extracted in the micro emulsion phase and the aqueous phase in excess was separated. In the second stage...

Efeito do nicotinato de cromo na sensibilidade à insulina e antropometria em indivíduos com diabetes mellitus tipo 2; >Effect of chromium nicotinate on insulin sensitivity and anthropometry in type 2 diabetes mellitus subjects

Guimarães, Marília Mendonça
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Ciências da Saúde (FM); Faculdade de Medicina - FM (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Ciências da Saúde (FM); Faculdade de Medicina - FM (RG)
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
37.2%
Chromium dietary interventions have been used to investigate the improvement in insulin sensitivity due to the role of chromium as a central component of the glucose tolerance factor. This study aims investigate the effect of chromium nicotinate supplementation on insulin sensitivity and anthropometry in type 2 diabetic subjects. In double-blind trial, fifty-six type 2 diabetic subjects with Body Mass Index 25 kg/m2 and increased waist circumference were randomized into three groups: placebo (NC0), 50μg (NC50) and 200μg (NC200) of chromium nicotinate. Status of chromium, insulin resistance, cell function, glycemic control, lipid profile, anthropometry, intensity and energy expenditure in physical activity were assessed at the beginning, 45 and 90 days of intervention. Energy consumption was assessed at the beginning, between the beginning and 45 days and between 45 and 90 days of study. Most subjects had low serum levels of chromium (71.88%), normal levels of urinary chromium (80.65%) and insulin resistance (73.80%). Chromium serum concentrations did not differ between groups over time (p = 0.2549). Changes in concentrations of serum and urinary chromium were not related to changes in fasting glucose (p> 0.05). At 90 days...

Predictors of serum chromium levels after stainless steel posterior spinal instrumentation for adolescent idiopathic scoliosis

Rackham, M.; Cundy, T.; Antoniou, G.; Freeman, B.; Sutherland, L.; Cundy, P.
Fonte: Lippincott Williams & Wilkins Publicador: Lippincott Williams & Wilkins
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
37.2%
OBJECTIVE. To determine the predictors of serum chromium levels after stainless steel posterior spinal instrumentation for adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA. Abnormally elevated serum chromium levels have been detected in patients with adolescent idiopathic scoliosis after stainless steel instrumentation. To date, the relationship among serum chromium levels, time of implantation, and implant characteristics (including surface area, rod length, numbers of hooks, screws, and cross connectors) has not been studied. METHODS. Thirty patients with adolescent idiopathic scoliosis undergoing posterior instrumented spinal arthrodesis using stainless steel implants between 1998 and 2002 were prospectively studied. Serum chromium levels were measured between October 2006 and June 2007. Postoperative radiographs were used to measure rod lengths, number of hooks, screws, cross-connectors, and cables. The surface area of each component and the total surface area for each patient were calculated. Possible associations between serum chromium levels, time of implantation, and implant characteristics were investigated. RESULTS. Implant exposure, whether expressed in the form of total metal implant surface area, rod length...

Chromium ion release from stainless steel pediatric scoliosis instrumentation

Cundy, T.; Delaney, C.; Rackham, M.; Antoniou, G.; Oakley, A.; Freeman, B.; Sutherland, L.; Cundy, P.
Fonte: Lippincott Williams & Wilkins Publicador: Lippincott Williams & Wilkins
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
37.18%
Study Design. Case–control study. Objective. To determine whether serum metal ion levels and erythrocyte chromium levels in adolescents with stainless steel spinal instrumentation are elevated when compared with 2 control groups. Summary of Background Data. Instrumented spinal arthrodesis is a common procedure to correct scoliosis. The long-term consequences of retained implants are unclear. Possible toxic effects related to raised metal ion levels have been reported in the literature. Methods. Thirty patients who underwent posterior spinal arthrodesis with stainless steel instrumentation for scoliosis (group 1) were included. Minimum postoperative duration was 3 years. Serum chromium, molybdenum, iron, and ferritin levels were measured. Participants with elevated above normal serum chromium levels (n = 11) also underwent erythrocyte chromium analysis. Comparisons were made with 2 control groups; 10 individuals with scoliosis with no spinal surgery (group 2) and 10 volunteers without scoliosis (group 3). All control group participants underwent serum and erythrocyte analysis. Results. Elevated above normal serum chromium levels were demonstrated in 11 of 30 (37%) group 1 participants. Elevated serum chromium levels were demonstrated in 0 of 10 participants (0%) in group 2 and 1 of 10 (10%) in group 3. There was a statistically significant elevation in serum chromium levels between group 1 and group 2 participants (P = 0.001). There was no significant association between groups 1...

The influence of microstructure on the corrosion and wear mechanisms of high chromium white irons in highly caustic solutions.

Nelson, G. D.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
Relevância na Pesquisa
37.26%
High chromium white irons are used extensively for wear resistance applications and owing to their high chromium content are often used in erosive-corrosive environments such as alumina processing plants using the Bayer refining process. The first stages of the Bayer refining processes (the red side) involve the transfer of hot slurries containing a high proportion of erosive quartz particles suspended in a pH 14 caustic solution. The solution contains varying amounts of dissolved alumina making the environment erosive and corrosive. High chromium white irons are often used to prolong service life and reduce operating costs. Pump components are often cast high chromium white irons and piping is often weld overlayed with high chromium white iron. To date there has been very little information reported in the literature on the wear of high chromium white irons in alumina processing environments. Furthermore, very limited work has been reported on the corrosion behaviour of high chromium white irons in caustic environments. This thesis investigates the development of microstructure in high chromium white irons typically used in the Australian Alumina Industry and how variables such as the bulk chemical composition, cooling rate and heat treatment can be used to vary the microstructure. Microstructural characteristics that influence wear and corrosion were investigated by undertaking corrosion and erosion-corrosion wear tests in a sodium aluminate solution representative of what is found in the alumina processing industry. The corrosion of high chromium white irons in sodium hydroxide solution was compared with their corrosion in sodium aluminate solution to investigate the influence aluminate ions have on corrosion. A range of ex-service alumina processing plant high chromium white irons castings and weld overlays were investigated. This not only provided materials for further testing but from the examination of the wear surface allowed the results of laboratory wear tests to be compared with those of the plant samples and test methods validated. A total of four different commercially produced casting materials ranging from hypoeutectic to hypereutectic compositions were compared with an experimental high chromium white iron casting...

Isotermas de adsorção de Freundlich para o crômio (III) em Latossolos; Freundlich adsorption isotherms for chromium (III) in Oxisols

Alcântara, Marco Aurélio Kondracki de; Camargo, Otávio Antonio de
Fonte: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz Publicador: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/09/2001 POR
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Environmental impacts caused by tannery waste application to agricultural soils must be studied to avoid biota and groundwater contamination. Soil chromium adsorption is very important, when the soil adsorptive capacity is exceeded and, potentially, the metals become available for leaching. The objectives of this study were to verify if the isotherm of Freundlich describes adequately the chromium adsorption by Oxisols, to study chromium adsorption considering different soils and horizons, as well as some chemical and physical attributes, and to evaluate the influence of the pH level on chromium adsorption. Samples of the A and B horizons of two soils were collected in the São Paulo State - Brazil: a) Typic Eutrorthox (LVe) and b) Typic Haplorthox (LVd). The pH alteration of the surface horizons was performed with the addition of calcium carbonate to reach 70% base saturation. Samples were shaken with CrCl3 solutions (prepared in Ca(NO3)2 5 mmol L-1 as the support electrolyte) of different initial chromium concentrations Co: 0; 0.5; 1.0; 2.5; 5.0; 10.0 and 50.0 mg L-1, using two replicates for each treatment. Freundlich isotherms were adjusted to describe the chromium adsorption by the soil. This isoterm fitted well to the experimental data. Chromium adsorption was higher in the Typic Eutrorthox than in the Typic Haplorthox. The adsorption was also favored by liming in both soils. There was no difference between chromium adsorption by the two horizons of the soils.; Os impactos causados no ambiente pela aplicação de resíduos de curtume contendo crômio em solos agrícolas devem ser estudados detalhadamente para que se evite a contaminação da biota e das águas subterrâneas. A adsorção do crômio ao solo reveste-se de especial importância em estudos de movimentação de solutos...

Separation of the chromium(III) present in a tanning wastewater by means of precipitation, reverse osmosis and adsorption

Hintermeyer,B. H.; Lacour,N. A.; Perez Padilla,A.; Tavani,E. L.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
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The separation of the chromium(III) dissolved in a tanning wastewater was studied by means of precipitation with calcium carbonate, reverse osmosis with polyamide membrane and adsorption on activated carbon. All tests were carried out at laboratory scale with a wastewater obtained from a unique typical tannage process. In a first stage, the original effluent was treated by sieving and ultrafiltration to perform a partial removal of fats and denaturalized proteins. The separation of chromium(III) by precipitation, reverse osmosis and adsorption was performed with the tanning wastewater so treated. The precipitation efficiency was determined by taking into account the chromium(III) content of the supernatant with the reaction time and with the alkali amount added. The polyamide membrane behavior used was established by the permeate flux and by the rejection of each species. The adsorption valuation involved the determination of the adsorbed amounts of chromium(III), sodium, chloride and sulfate. Under optimum conditions established for each process, the following results were obtained: a supernatant with less than 3.0 mg L-1 of chromium(III) by precipitation, a permeate with less than 2.0 mg L-1 of chromium(III) by reverse osmosis and an equilibrium solution with less than 6.0 mg L-1 of chromium(III) by adsorption. To conclude...