Efeitos da soldagem por laser de fibra de Yb na microestrutura do compósito A356/SiCp

Materiais compósitos são projetados e fabricados para várias aplicações de alto desempenho, incluindo componentes para os segmentos automobilístico, aeroespacial, aeronáutico, naval, de defesa, de óleo e gás, energia eólica e até equipamentos esportivos. Porém, a união por soldagem de Compósitos de Matriz Metálica de Alumínio (Al-CMM) ainda é um grande obstáculo para a maior disseminação desta classe de materiais estruturais. As mudanças microestruturais decorrentes do ciclo de soldagem e/ou do tratamento térmico afetam sensivelmente as propriedades mecânicas e físico-químicas finais da junta e do metal base nas proximidades de mesma, daí a importância de se estudar a evolução microestrutural que prospera nestas etapas. O presente trabalho caracterizou a microestrutura do compósito liga-A356/SiCp soldado por laser de fibra de Itérbio, empregando-se nessa tarefa técnicas de microscopia óptica, radiografia e microscopia eletrônica de varredura, assim como difração de raios-X e de elétrons retroespalhados, ensaio instrumentado de dureza e microtomografia computadorizada. O foco das análises realizadas restringiu-se à geometria dos cordões de solda, à expulsão de SiC particulado da zona soldada, à volatilização de elementos químicos da poça de soldagem, à formação de precipitados fragilizantes de Al4SiC4 em formato de agulhas no cordão de solda e à determinação das regiões com concentração de poros, todos estes fenômenos tendo efeitos nocivos, em maior ou menor extensão, no desempenho global da junta do Al-CMM soldada a laser, notadamente em suas propriedades mecânicas e eletroquímicas.

Monitoramento de micro-organismos indicadores de higiene em linha de abate de bovinos de um matadouro-frigorífico habilitado à exportação no oeste do Paraná

Indicators microorganisms can be used as a method for evaluating the sanitary quality of food products, indicating the suitability of conditions for obtaining, processing and storage of food. This study sought to evaluate surface contamination of cattle carcasses that come from a slaughter plant under Federal Inspection in western Parana by mesophilic bacteria (AM), Enterobacteriaceae (EB), coliform at 35 degrees C (TC) and E. coli (EC). Surface samples were collected from 25 carcasses, each at 4 different points of slaughter, for non-destructive method. The samples were diluted in decimal scale and incubated in Petrifilm (R) plates. Were found averages of 1.46; 0.3; 0.23 and 0.21 log CFU / cm (2) for AM, EB, CT and EC, respectively. The values to be found were well below those recommended by the decision 471/2001 of the European Union and several other authors surveyed, indicating the effectiveness of the hygienic process industry.

Síntese de supercondutores cerâmicos à base de bismuto produzidos pelo método Pechini associado ao processo de hidrotermalização assistido por micro-ondas

Pós-graduação em Ciência dos Materiais - FEIS

Viabilidade operacional e econômica da utilização de micro tratores em sistema de manejo florestal comunitário no oeste da Amazônia.

Em meados da década de 1990, a Embrapa Acre iniciou o desenvolvimento de um projeto de manejo florestal comunitário no Projeto de Colonização Pedro Peixoto, no Acre, o qual propõe métodos acessíveis para produtores rurais de baixa renda e que consideram suas relações com a floresta, os meios que dispõem e suas tradições como agricultores familiares. Originalmente, no sistema de manejo do PC Peixoto o transporte primário da madeira da floresta até as vias de escoamento é praticado com animais (bois de carga), no entanto, é verificado que a eficiência desse método é baixa. Diante dessa limitação, foi proposto substituir os animais por micro tratores, acoplados a carretas basculantes. Este trabalho tem por objetivo apresentar os índices técnicos e econômicos da colheita de madeira do PC Peixoto com a inserção de um micro trator em substituição aos animais. O equipamento foi o micro trator Yanmar Agritech TC-14, 14 cv. Comparado aos animais, o micro trator mostrou-se vantajoso em muitos aspectos, tanto na melhoria do desempenho e produtividade, que praticamente dobrou, como também em relação aos custos, apontando para a viabilidade da sua utilização.

Ihwg-μnir: A Miniaturised Near-infrared Gas Sensor Based On Substrate-integrated Hollow Waveguides Coupled To A Micro-nir-spectrophotometer.

A miniaturised gas analyser is described and evaluated based on the use of a substrate-integrated hollow waveguide (iHWG) coupled to a microsized near-infrared spectrophotometer comprising a linear variable filter and an array of InGaAs detectors. This gas sensing system was applied to analyse surrogate samples of natural fuel gas containing methane, ethane, propane and butane, quantified by using multivariate regression models based on partial least square (PLS) algorithms and Savitzky-Golay 1(st) derivative data preprocessing. The external validation of the obtained models reveals root mean square errors of prediction of 0.37, 0.36, 0.67 and 0.37% (v/v), for methane, ethane, propane and butane, respectively. The developed sensing system provides particularly rapid response times upon composition changes of the gaseous sample (approximately 2 s) due the minute volume of the iHWG-based measurement cell. The sensing system developed in this study is fully portable with a hand-held sized analyser footprint, and thus ideally suited for field analysis. Last but not least, the obtained results corroborate the potential of NIR-iHWG analysers for monitoring the quality of natural gas and petrochemical gaseous products.

Estudo por espectroscopia micro-Raman dos mecanismos de separação de fase em vidros fosfatos de metais de transição

Glass-ceramics are prepared by controlled separation of crystal phases in glasses, leading to uniform and dense grain structures. On the other hand, chemical leaching of soluble crystal phases yields porous glass-ceramics with important applications. Here, glass/ceramic interfaces of niobo-, vanado- and titano-phosphate glasses were studied by micro-Raman spectroscopy, whose spatial resolution revealed the multiphase structures. Phase-separation mechanisms were also determined by this technique, revealing that interface composition remained unchanged as the crystallization front advanced for niobo- and vanadophosphate glasses (interface-controlled crystallization). For titanophosphate glasses, phase composition changed continuously with time up to the equilibrium composition, indicating a spinodal-type phase separation.

Determinação espectrofotométrica de hexametilenotetramina (HMT) em medicamentos, utilizando ácido cromotrópico e forno de micro-ondas

This paper proposes a methodology for spectrophotometric determination of hexamethylenetetramine (HMT) by using chromotropic acid in a phosphoric acid media employing a domestic microwave oven as a source of heating. The reddish-purple soluble product is quantitatively formed after 30 s of irradiation and obeys the Beer´s law in the range between 0.1-1.2 mg L-1 HMT (r = 0.99925). The method was applied successfully in commercial pharmaceutical preparations containing dyes in their composition. The results showed that the method proposed is feasible for simplicity, speed, low cost, precision and accuracy when compared with United States Pharmacopeia official method.

Trombose na endoprótese do aneurisma da aorta: avaliação por TC multidetector

OBJETIVO: Avaliar as características demográficas e de imagens da trombose endoluminal em uma série de pacientes submetidos a tratamento endovascular do aneurisma de aorta abdominal (TEAAA). MÉTODOS: Avaliamos as características de imagem que permitiram o diagnóstico da trombose endoluminal em uma série de 30 pacientes submetidos ao TEAAA, com seguimento de 5 a 29 meses, através de exames de tomografia computadorizada multidetectores (TCMD) de 64 canais. RESULTADOS: Foram diagnosticados dez casos de trombose luminal (33,3%), sendo que em três pacientes a trombose foi total de um ramo ilíaco. CONCLUSÃO: A TCMD permitiu o diagnóstico de diferentes tipos de trombose endoluminal em pacientes submetidos ao TEAAA. O uso desta modalidade diagnóstica minimamente invasiva deverá ser encorajado na prática clínica.

The Rg1 allele as a valuable tool for genetic transformation of the tomato 'Micro-Tom' model system

Background: The cultivar Micro-Tom (MT) is regarded as a model system for tomato genetics due to its short life cycle and miniature size. However, efforts to improve tomato genetic transformation have led to protocols dependent on the costly hormone zeatin, combined with an excessive number of steps. Results: Here we report the development of a MT near-isogenic genotype harboring the allele Rg1 (MT-Rg1), which greatly improves tomato in vitro regeneration. Regeneration was further improved in MT by including a two-day incubation of cotyledonary explants onto medium containing 0.4 mu M 1-naphthaleneacetic acid (NAA) before cytokinin treatment. Both strategies allowed the use of 5 mu M 6-benzylaminopurine (BAP), a cytokinin 100 times less expensive than zeatin. The use of MT-Rg1 and NAA pre-incubation, followed by BAP regeneration, resulted in high transformation frequencies (near 40%), in a shorter protocol with fewer steps, spanning approximately 40 days from Agrobacterium infection to transgenic plant acclimatization. Conclusions: The genetic resource and the protocol presented here represent invaluable tools for routine gene expression manipulation and high throughput functional genomics by insertional mutagenesis in tomato.

Analysis of the tip roundness effects on the micro- and macroindentation response of elastic-plastic materials

In this work, the effects of indenter tip roundness oil the load-depth indentation curves were analyzed using finite element modeling. The tip roundness level was Studied based on the ratio between tip radius and maximum penetration depth (R/h(max)), which varied from 0.02 to 1. The proportional Curvature constant (C), the exponent of depth during loading (alpha), the initial unloading slope (S), the correction factor (beta), the level of piling-up or sinking-in (h(c)/h(max)), and the ratio h(max)/h(f) are shown to be strongly influenced by the ratio R/h(max). The hardness (H) was found to be independent of R/h(max) in the range studied. The Oliver and Pharr method was successful in following the variation of h(c)/h(max) with the ratio R/h(max) through the variation of S with the ratio R/h(max). However, this work confirmed the differences between the hardness values calculated using the Oliver-Pharr method and those obtained directly from finite element calculations; differences which derive from the error in area calculation that Occurs when given combinations of indented material properties are present. The ratio of plastic work to total work (W(p)/W(t)) was found to be independent of the ratio R/h(max), which demonstrates that the methods for the Calculation of mechanical properties based on the *indentation energy are potentially not Susceptible to errors caused by tip roundness.

Importance of considering a material micro-failure criterion in the numerical modelling of the shot peening process applied to parabolic leaf springs

Shot peening is a cold-working mechanical process in which a shot stream is propelled against a component surface. Its purpose is to introduce compressive residual stresses on component surfaces for increasing the fatigue resistance. This process is widely applied in springs due to the cyclical loads requirements. This paper presents a numerical modelling of shot peening process using the finite element method. The results are compared with experimental measurements of the residual stresses, obtained by the X-rays diffraction technique, in leaf springs submitted to this process. Furthermore, the results are compared with empirical and numerical correlations developed by other authors.

Convergence of developmental mutants into a single tomato model system: 'Micro-Tom' as an effective toolkit for plant development research

Background: The tomato (Solanum lycopersicum L.) plant is both an economically important food crop and an ideal dicot model to investigate various physiological phenomena not possible in Arabidopsis thaliana. Due to the great diversity of tomato cultivars used by the research community, it is often difficult to reliably compare phenotypes. The lack of tomato developmental mutants in a single genetic background prevents the stacking of mutations to facilitate analysis of double and multiple mutants, often required for elucidating developmental pathways. Results: We took advantage of the small size and rapid life cycle of the tomato cultivar Micro-Tom (MT) to create near-isogenic lines (NILs) by introgressing a suite of hormonal and photomorphogenetic mutations (altered sensitivity or endogenous levels of auxin, ethylene, abscisic acid, gibberellin, brassinosteroid, and light response) into this genetic background. To demonstrate the usefulness of this collection, we compared developmental traits between the produced NILs. All expected mutant phenotypes were expressed in the NILs. We also created NILs harboring the wild type alleles for dwarf, self-pruning and uniform fruit, which are mutations characteristic of MT. This amplified both the applications of the mutant collection presented here and of MT as a genetic model system. Conclusions: The community resource presented here is a useful toolkit for plant research, particularly for future studies in plant development, which will require the simultaneous observation of the effect of various hormones, signaling pathways and crosstalk.

A flow injection procedure based on solenoid micro-pumps for spectrophotometric determination of free glycerol in biodiesel

A flow system designed with solenoid micro-pumps is proposed for fast and greener spectrophotometric determination of free glycerol in biodiesel. Glycerol was extracted from samples without using organic solvents. The determination involves glycerol oxidation by periodate, yielding formaldehyde followed by formation of the colored (3,5-diacetil-1,4-dihidrolutidine) product upon reaction with acetylacetone. The coefficient of variation, sampling rate and detection limit were estimated as 1.5% (20.0 mg L(-1) glycerol, n =10), 34 h(-1), and 1.0 mg L(-1) (99.7% confidence level), respectively. A linear response was observed from 5 to 50 mg L(-1), with reagent consumption estimated as 345 mu g of KIO(4) and 15 mg of acetylacetone per determination. The procedure was successfully applied to the analysis of biodiesel samples and the results agreed with the batch reference method at the 95% confidence level. (C) 2010 Elsevier B.V. All rights reserved.

A flow-based procedure with solenoid micro-pumps for the spectrophotometric determination of uric acid in urine

The determination of uric acid in urine shows clinical importance, once it can be related to human organism dysfunctions, such as gout. An analytical procedure employing a multicommuted flow system was developed for the determination of uric acid in urine samples. Cu(II) ions are reduced by uric acid to Cu(I) that can be quantified by spectrophotometry in the presence of 2,2`-biquinoline 4,4`-dicarboxylic acid (BCA). The analytical response was linear between 10 and 100 mu mol L(-1) uric acid with a detection limit of 3.0 mu mol L(-1) (99.7% confidence level). Coefficient of variation of 1.2% and sampling rate of 150 determinations per hour were achieved. Per determination, 32 mu g of CuSO(4) and 200 mu g of BCA were consumed, generating 2.0 mL of waste. Recoveries from 91 to 112% were estimated and the results for 7 urine samples agreed with those obtained by the commercially available enzymatic kit for determination of uric acid. The procedure required 100-fold dilution of urine samples, minimizing sample consumption and interfering effects. In order to avoid the manual dilution step, on-line sample dilution was achieved by a simple system reconfiguration attaining a sampling rate of 95 h(-1). (C) 2009 Elsevier B.V. All rights reserved.

Exploiting Mn(III)/EDTA complex in a flow system with solenoid micro-pumps coupled to long pathlength spectrophotometry for fast manganese determination

The formation of the Mn(III)/EDTA complex in a flow system with solenoid micro-pumps was exploited for fast manganese determination in freshwater. Manganese(II) was oxidized in a solid-phase reactor containing lead dioxide immobilized on polyester. Long pathlength spectrophotometry was exploited to increase sensitivity, aiming to reach the threshold limit established by environmental legislation. A linear response was observed from 25 to 1500 mu g L(-1), with a detection limit of 6 mu g L(-1) (99.7% confidence level). Sample throughput and coefficient of variation were 36 samples/h and 2.6% (n = 10), respectively. EDTA consumption and waste generation were estimated as 500 mu g and 3 mL per determination, respectively. The amount of Pb in the residue corresponds to 250 mu g per determination and a solid-phase reactor could be used for up to 1600 determinations. Adsorption in active charcoal avoided interferences caused by organic matter and the developed procedure was successfully applied for determination of manganese in freshwater samples. Results were in agreement with those attained by GFAAS at the 95% confidence level. (C) 2010 Elsevier B.V. All rights reserved.