Estudo da eletrocristalização de Ni e Ni-P sobre ultramicroeletrodo de platina

This work describes a comparative study of the electrocrystallization of Ni and Ni-P on Pt ultramicroelectrodes using chronoamperometric measurements. It was possible to confirm that in all cases a progressive nucleation was the predominant mechanism. Moreover, the application of the Atomistic Theory to the experimental rate of nuclei formation showed that the number of atoms in the critical nucleus was zero, except for Ni-P on Pt at low overpotentials were a value of one was observed. Furthermore, the physical characterisation of the different deposits on Pt by atomic force microscopy allowed observing the coalescence of the hemispherical nuclei of Ni and Ni-P at t max thus confirming the results obtained from the current-time analysis.

Estudo da eletrocristalização de Ni e Ni-P sobre ultramicroeletrodo de platina

This work describes a comparative study of the electrocrystallization of Ni and Ni-P on Pt ultramicroelectrodes using chronoamperometric measurements. It was possible to confirm that in all cases a progressive nucleation was the predominant mechanism. Moreover, the application of the Atomistic Theory to the experimental rate of nuclei formation showed that the number of atoms in the critical nucleus was zero, except for Ni-P on Pt at low overpotentials were a value of one was observed. Furthermore, the physical characterisation of the different deposits on Pt by atomic force microscopy allowed observing the coalescence of the hemispherical nuclei of Ni and Ni-P at t max thus confirming the results obtained from the current-time analysis.

Elaboração e caracterização de revestimentos nanocompósitos Ni-P-Sic eletrodepositados

Revestimentos compósitos com incorporação de SiC (com tamanho médio 600nm e 30nm) à matriz metálica de Ni-P foram elaborados por eletrodeposição a partir de uma solução de sais de níquel, contendo um precursor fosforoso H3PO3, na qual as partículas foram colocadas em suspensão. A partir de medidas de viscosidade e velocidade de sedimentação foi evidenciado que o tamanho das partículas de SiC é uma característica importante que influencia na estabilidade das suspensões. Além disso, a presença de aditivos orgânicos, como SDS ou CTAHS, modifica as características das suspensões podendo ter, de acordo com o tamanho das partículas, um efeito sobre a taxa de incorporação da mesma no depósito durante o crescimento da matriz. Observou-se que acima de uma certa concentração de partículas em suspensão, a taxa de incorporação avaliada em função da fração em volume atinge um patamar, quando, no entanto, a mesma continua a aumentar se avaliada pelo número de partículas incorporadas. Para as suspensões com elevada concentração de partículas, o processo de incorporação torna-se seletivo, e as partículas de menor tamanho são preferencialmente incorporadas. Medidas de microdureza, análise térmica e ensaios eletroquímicos (voltametria cíclica e impedância eletroquímica) foram realizados com o objetivo de investigar o efeito da quantidade e do tamanho das partículas de SiC incorporadas, sobre o comportamento térmico, a microdureza, e a resistência à corrosão dos revestimentos compósitos Ni-P-SiC com teor em fósforo igual a 17 %at.

Sintesi, caratterizzazione e reattività di nuovi Cluster Carbonilici Ni-P

The aim of this work is to explore the chemistry of new heteroatomic molecular compounds never reported in the scientific literature so far: Ni-P carbonyl clusters. First, an attempt was made to illustrate the reasons which brought to the choice of this specific metal-pnictogen couple, such as the interesting properties of Ni-P binary phases, the difficulties related in obtaining structural data for this bulk compounds and the absence of references about nickel-phosphorus molecular compounds (e.g. carbonyl clusters) reported in literature. Then, the general criteria chosen for the reactions between precursors [Ni6(CO)12]2- and PCl3 or POCl3 have been reported. This work has permitted to individuate many new products, of which some have also been isolated and characterised: [Ni11P(CO)18]3-, [Ni23-xP2(CO)30-x]6- (x=0, 1), [HNi31P4(CO)39]5- e [H2Ni31P4(CO)39]4-. Except for the former, a reproducible synthetic path has been refined for all those new Ni-P carbonyl clusters; furthermore some chemical reactivity has been carried out in order to test their characteristics.

Propuesta de manejo de residuos químicos de procesos autocatalíticos de Ni-P sobre aceros

En el presente trabajo de graduación se realizó un análisis sobre la propuesta de manejo de residuos químicos de procesos autocatalíticos de Ni-P sobre aceros, la cual es una técnica que en El Salvador aún no se realiza a nivel industrial y con el desarrollo de esta investigación se espera facilitar el desarrollo de dichos procesos. La investigación se desarrolló con la ayuda de información bibliográfica donde se describen los procesos, el manejo y almacenamiento de los químicos utilizados en los procesos y una cantidad significativa de los muchos baños que se producen, de los cuales se eligieron dos para presentar la propuesta, tomando en cuenta también el factor económico para la deposición final, con la cual se realizará la eliminación de los residuos químicos del proceso de deposición autocatalítica de Ni-p sobre aceros

Preparation of Ni-P electroless and its corrosion resistance against sea water

Electroless coating is much appropriate process at engineering surface. Since the discovery of electroless nickel-phosphorus coating in 3996, due to technical and economic advantages as well as desirable characteristics such as resistance to corrosion, abrasion and a high hardness has found wide application at engineering industries. Properties of electroless nickel-phosphorus coating depend on the characteristics of the used bath and heat treatment. In this study, optimal conditions and concentration of sodium citrate, sodium acetate and lactic acid in the bath of electroless nickel-phosphorus coating to the steel ck67 surface was determined. Structure, chemical composition and phases occurring in the coating were investigated using Scanning Electron Microscope (SEM) and X-ray diffraction analysis (XRD). The corrosion behavior of coatings in solution 3.5٪ NaCl was studied using electrochemical. The results showed that corrosion resistance of the coating with composition sodium citrate, sodium acetate and lactic acid decreased respectively.

Electrodeposition of amorphous Fe-Cr-P-Ni-C alloys. Morphological and structural characteristics

The effect of bath composition and electroplating conditions on structure, morphology and composition of amorphous Fe-Cr-P-Ni-C deposits on Cu substrate was investigated. The deposition efficiency of Fe-Ni-P-C alloy increased significantly with the addition of formic acid, but decreased with the addition of Cr to the plating bath. The increase of charge density activates the inclusion of Cr in the deposit. However, above a specific value of charge density, which depends on deposition current density, the Cr content in the deposit decreases. SEM analysis showed that the increase of Ni, Cr or charge deposition promotes susceptibility to microcracking.

Exploring the emission intensities of ICP OES aided by chemometrics in the geographical discrimination of mineral waters

A rapid method for classification of mineral waters is proposed. The discrimination power was evaluated by a novel combination of chemometric data analysis and qualitative multi-elemental fingerprints of mineral water samples acquired from different regions of the Brazilian territory. The classification of mineral waters was assessed using only the wavelength emission intensities obtained by inductively coupled plasma optical emission spectrometry (ICP OES), monitoring different lines of Al, B, Ba, Ca, Cl, Cu, Co, Cr, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Sb, Si, Sr, Ti, V, and Zn, and Be, Dy, Gd, In, La, Sc and Y as internal standards. Data acquisition was done under robust (RC) and non-robust (NRC) conditions. Also, the combination of signal intensities of two or more emission lines for each element were evaluated instead of the individual lines. The performance of two classification-k-nearest neighbor (kNN) and soft independent modeling of class analogy (SIMCA)-and preprocessing algorithms, autoscaling and Pareto scaling, were evaluated for the ability to differentiate between the various samples in each approach tested (combination of robust or non-robust conditions with use of individual lines or sum of the intensities of emission lines). It was shown that qualitative ICP OES fingerprinting in combination with multivariate analysis is a promising analytical tool that has potential to become a recognized procedure for rapid authenticity and adulteration testing of mineral water samples or other material whose physicochemical properties (or origin) are directly related to mineral content.

Influence of field-based nutrient enrichment on the photobiology of the giant clam Tridacna maxima

Nutrients were added to 12 microatolls in One Tree Island lagoon every low tide for 13 mo to an initial concentration of 10 mu M (ammonium, N) and 2 mu M (phosphate, P). These concentrations remained above background for 2 to 3 h after addition. The addition of ammonium (N and NI-P but not P alone) significantly increased P, (gross photosynthesis) P,, (net photosynthesis) and R (respiration) per unit wet-tissue weight and cc (photosynthetic efficiency) in Tridacna maxima after 3 mo nutrient enrichment. These responses to small and transient changes in ammonium concentrations suggest that symbiotic clams are not nutrient-replete, and that even subtle changes in nutrients can have a measurable effect on photosynthesis. The same clams did not show significant differences in photosynthetic parameters 6 mo after the beginning of nutrient enrichment, suggesting that their previous responses had either been seasonal or that symbiotic clams such as T. maxima are able to adjust their photophysiology following external changes in nutrient concentrations.

Caracterização trófica e modelação da Lagoa do Fogo - S. Miguel, Açores

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia do Ambiente, perfil de Engenharia Sanitária

Nosocomial infections in a Brazilian neonatal intensive care unit: a 4-year surveillance study

INTRODUCTION: Report the incidence of nosocomial infections, causative microorganisms, risk factors associated with and antimicrobial susceptibility pattern in the NICU of the Uberlândia University Hospital. METHODS: Data were collected through the National Healthcare Safety Network surveillance from January 2006 to December 2009. The patients were followed five times/week from their birth to their discharge or death. RESULTS: The study included 1,443 patients, 209 of these developed NIs, totaling 293 NI episodes, principally bloodstream infections (203; 69.3%) and conjunctivitis (52; 17.7%). Device-associated infection rates were as follows: 17.3 primary bloodstream infections per 1,000 central line-days and 3.2 pneumonias per 1000 ventilator-days. The mortality rate in neonates with NI was 11.9%. Mechanical ventilation, total parenteral nutrition, orogastric tube, previous antibiotic therapy, use of CVC and birth weight of 751-1,000g appeared to be associated with a significantly higher risk of NI (p < 0.05). In multiple logistic regression analysis for NI, mechanical ventilation and the use of CVC were independent risk factors (p < 0.05). Coagulase- negative Staphylococcus (CoNS) (36.5%) and Staphylococcus aureus (23.6%) were the most common etiologic agents isolated from cultures. The incidences of oxacillin-resistant CoNS and S. aureus were 81.8% and 25.3%, respectively. CONCLUSIONS: Frequent surveillance was very important to evaluate the association of these well-known risk factors with NIs and causative organisms, assisting in drawing the attention of health care professionals to this potent cause of morbidity.

Contribuição para a otimização do fabrico de compressores scroll

A indústria automóvel é um meio extremamente competitivo, onde existe uma procura constante por novas soluções, sempre com a necessidade de redução de custos e otimização de recursos. A Halla Visteon Climate Control (HVCC), que se trata de uma empresa líder na sua área de atuação, verificou a existência de problemas no processo de fabrico de alguns componentes do seu compressor Scroll, na sequência da alteração da matéria-prima para uma liga AA 6082-T6. Na presente Dissertação realizou-se uma análise comparativa entre o material corrente e um novo material, AA 7075-T6, sem que tenham sido alterados quaisquer parâmetros do processo produtivo, tornando possível a avaliação do potencial de utilização do novo material. Foram testados diversos parâmetros, tendo em conta as diferentes etapas do processo produtivo, como a dureza e a rugosidade superficial, o estado do revestimento aplicado por Electroless e o comportamento da camada obtida por Anodização. A utilização da liga 7075 permitiu obter melhores resultados após as etapas de maquinagem, podendo contribuir para a eliminação dos problemas verificados nesta etapa do processo. No que diz respeito aos testes realizados após aplicação tanto dos revestimentos Ni-P, como da camada anodizada, os resultados revelaram-se semelhantes aos da liga 6082, sendo de destacar a melhoria de adesão verificada, comprovando assim o potencial de utilização deste material, especialmente num processo que possa ver os parâmetros otimizados para o mesmo.

Caracterização dos solos da ilha de Santiago (Cabo Verde) numa perspectiva de sustentabilidade ambiental

As respostas geoquímicas do ambiente são controladas, em primeiro lugar, pelos processos naturais, geológicos, pedológicos, climáticos e biológicos. Sobrepondo-se a essa herança, a presença do homem adquire papel importante pelas possibilidades de alteração que promove no ambiente geoquímico a partir das concentrações urbanas, actividades industriais e agrícolas. Nos últimos anos a cartografia geoquímica tem assumido uma importância relevante já que tem sido largamente reconhecido que para se identificar e quantificar a poluição antropogénica é fundamental a existência de mapas que apresentem os valores de fundo geoquímico natural. O principal objectivo deste estudo é o estabelecimento de uma base de dados geoquímicos da ilha de Santiago (Cabo Verde) utilizando os solos como meio amostral. Esta base de dados geoquímicos permitiu caracterizar o estado actual dos solos da ilha de Santiago e estabelecer os valores de fundo geoquímico. A ilha de Santiago, com uma área de 991km2, é a maior ilha do arquipélago representando cerca de 25% da área total. Tem forma adelgaçada na direcção Norte-Sul, apresentando um comprimento máximo de 54,9km entre a ponta Moreia, a Norte, e a ponta Mulher Branca, a Sul, e uma largura máxima de 29km entre a ponta Janela, a Oeste, e a ponta Praia Baixo, a Leste. Apresenta uma altitude máxima de 1392m. No presente trabalho foram seguidas as recomendações do projecto “IGCP 259 – International Geochemical Mapping” no que se refere aos procedimentos de amostragem, preparação física das amostras, análise química e controlo de qualidade dos resultados. Na ilha de Santiago foram colhidas 278 amostras de solos correspondendo a uma densidade de amostragem de 0.28 amostras por km2. As amostras foram decompostas com uma solução modoficada de áqua régia e analisadas para 37 elementos (Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Co, Cr, Cu,Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Se, Sr, Te, Th, Ti, Tl, U, V, W and Zn) por ICP-ES. Foram ainda determinados 5 parâmetros característicos do solo (pH, condutividade, matéria orgânica, cor e textura). Os padrões geoquímicos obtidos através dos mapas de distribuição espacial foram correlacionados com vários factores designadamente a natureza da rocha mãe, o tipo de solo e ainda com algumas fontes de contaminação. A utilização da Análise em Componentes Principais permitiu distinguir diferentes tipos de associações de variáveis realçando a importância das associações do tipo geogénico relativamente às associações to tipo antropogénico. A associação Na-CE assinala as áreas onde o impacto das actividades humanas influência os valores de fundo geoquímico

Endoleak and in-stent thrombus detection with CT angiography in a thoracic aortic aneurysm phantom at different tube energies using filtered back projection and iterative algorithms.

PURPOSE: To determine the lower limit of dose reduction with hybrid and fully iterative reconstruction algorithms in detection of endoleaks and in-stent thrombus of thoracic aorta with computed tomographic (CT) angiography by applying protocols with different tube energies and automated tube current modulation. MATERIALS AND METHODS: The calcification insert of an anthropomorphic cardiac phantom was replaced with an aortic aneurysm model containing a stent, simulated endoleaks, and an intraluminal thrombus. CT was performed at tube energies of 120, 100, and 80 kVp with incrementally increasing noise indexes (NIs) of 16, 25, 34, 43, 52, 61, and 70 and a 2.5-mm section thickness. NI directly controls radiation exposure; a higher NI allows for greater image noise and decreases radiation. Images were reconstructed with filtered back projection (FBP) and hybrid and fully iterative algorithms. Five radiologists independently analyzed lesion conspicuity to assess sensitivity and specificity. Mean attenuation (in Hounsfield units) and standard deviation were measured in the aorta to calculate signal-to-noise ratio (SNR). Attenuation and SNR of different protocols and algorithms were analyzed with analysis of variance or Welch test depending on data distribution. RESULTS: Both sensitivity and specificity were 100% for simulated lesions on images with 2.5-mm section thickness and an NI of 25 (3.45 mGy), 34 (1.83 mGy), or 43 (1.16 mGy) at 120 kVp; an NI of 34 (1.98 mGy), 43 (1.23 mGy), or 61 (0.61 mGy) at 100 kVp; and an NI of 43 (1.46 mGy) or 70 (0.54 mGy) at 80 kVp. SNR values showed similar results. With the fully iterative algorithm, mean attenuation of the aorta decreased significantly in reduced-dose protocols in comparison with control protocols at 100 kVp (311 HU at 16 NI vs 290 HU at 70 NI, P ≤ .0011) and 80 kVp (400 HU at 16 NI vs 369 HU at 70 NI, P ≤ .0007). CONCLUSION: Endoleaks and in-stent thrombus of thoracic aorta were detectable to 1.46 mGy (80 kVp) with FBP, 1.23 mGy (100 kVp) with the hybrid algorithm, and 0.54 mGy (80 kVp) with the fully iterative algorithm.