Laser Beam Deflection System For Measuring Stress Variations In Thin Film Electrodes

The bending beam method for measurements of stress in thin films deposited on an elastic substrate in the form of a thin stripe has been improved by the introduction of a laser beam deflection system and of a laser spot position detector. With this improvement, stress measurements have been performed in situ during the electrochemical reactions of palladium hydride formation and of valve metal anodic oxidation. Stress changes in the thin films of 107 N/m2 can be measured with a time response better than 1s. This allows the detection of rapid reactions (like H diffusion in a Pd thin film) and of the electrostriction effect even in anodic films with thickness below 20 nm.13741150115

AN ELECTRONEGATIVITY MODEL FOR VIBRATIONAL INTENSITIES OF SUBSTITUTED METHANES

8941887189

Environmental stress evaluation of Coffea arabica L. leaves from spectrophotometric fingerprints by PCA and OSC-PLS-DA

The effects of hydric stress and sunlight access conditions on metabolic compounds in coffee leaves were investigated utilizing statistical mixture design extractor solvents. PCA and OSC-PLS-DA chemometric methods were used to analyze UV-visible spectra of irrigated and non-irrigated Coffea arabica L. leaves from low (80 cm, light exposed) strata. The first latent variable of the OSC-PLS-DA score plot perfectly discriminated extracts of 34 calibration and 14 validation samples of irrigated and non-irrigated leaves. Higher spectral signals observed at the 410, 505, 535, 607 and 665 nm wavelengths are attributed to conjugate double bond pigments, mainly pheophytin a, indicating that non-irrigated conditions are more stressful than irrigated ones for this species. No significant difference was found for leaf sample extracts with varying light access conditions12842514257CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e Tecnológicosem informaçãosem informaçãoThe authors acknowledge the financial support of CNPq, CAPES, INCT – Energia e Ambiente and Fundação Araucária as well as for the scholarships granted. The Agronomic Institute of Paraná (IAPAR) is thanked for supplying the coffee leaf samples used in this wor

Optomechanical studies of lithium intercalation in amorphous molybdenum thin films

In this work, we studied radio-frequency reactively sputtered molybdenum oxide thin films. Thin films with distinct stoichiometries were obtained by varying the oxygen now and maintaining all other deposition parameters constant. The relationship between optical, electrochemical, and mechanical behavior of the films submitted to lithium intercalation in an aprotic electrolyte is reported. Films deposited at low oxygen flow (B-films) are substoichiometric molybdenum oxide, with composition MoO3-x (0 < x < 1). Films deposited at high oxygen flow (T-films) approach the MoO3 stoichiometry. B-films have a greater concentration of optically active sites and a more open structure when compared to T-films.14392822282

Time Evolution Of The Residual Stress Of Plasma-polymerized Acetylene Films In Various Ambients

The behavior of the residual stress with time of plasma-polymerized acetylene films in various ambients has been investigated. The plasma polymers were deposited on thin glass substrates in dc and rf discharges of acetylene. After deposition, the specimens were mounted in a chamber that could be evacuated or filled with air, oxygen, or nitrogen. Stress measurements were carried out by the bending beam method, using a He-Ne laser. A steady rise in the stress during time periods of several hours following film deposition was observed in most of the samples studied. Stress increments of more than one order of magnitude were detected in some of the films upon exposure to air. Pronounced stress increments were also observed during exposure to oxygen. Rises in the stress were detected even in a vacuum ambience. Nitrogen exposure was found to have little effect on the stress. The effect of the moisture content of air on the stress was also examined. The evolution of the stress was found to depend also on the film preparation conditions. The results strongly suggest that postplasma reactions involving active chemical species trapped in the film during deposition play an important role in the development of the stress.7094883488

Chemometric analysis of UV characteristic profile and infrared fingerprint variations of coffea arabica green beans under different space management treatments

Ultraviolet characteristic profiles and infrared spectroscopic (FTIR) fingerprints of green bean extracts of Coffea arabica L., cv. IAPAR 59, cultivated in two planting patterns, rectangular and square, and at two different densities, 10,000 and 6,000 plants ha-1, identified as R10, R6, S10, and S6 were analyzed with principal component and hierarchical cluster analyses. A simplex centroid design for four solvents (ethanol, acetone, dichloromethane, hexane) was used for sample extraction. The largest chlorogenic acid (CGA) contents were found at the lower planting density. The dichloromethane extracts of the S10 treatment showed the highest levels of unsaponifiable lipids (cafestol and kahweol). The R6 treatment showed a slightly higher content of cafestol and kahweol. Cluster analysis of FTIR fingerprints confirmed that the CGA and caffeine levels differentiate the spatial arrangements. The FTIR fingerprints suggest that green beans from S6 and R10 were richer in lipids and the other two treatments had more sugars and proteins27712541263CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPSem informaçãoSem informaçã

Respostas alimentares e arrestantes de Diabrotica speciosa a formulações contendo cucurbitacina

The objective of this work was to evaluate arrestant and stimulant feeding effects on Diabrotica speciosa (Ger.), using cucurbitacin-content starch-based formulations prepared with varying starch sources, and adding potassium lignate. In a glass slide assay, the wash off resistance of formulations was compared. Potassium lignate did not improve wash off resistance. Lagenaria vulgaris L. powder, in which cucurbitacin B concentration was determined as 0.28%, was added to the most adhesive formulation. The resultant material was used in a two-choice assay in which leaves of common bean, Phaseolus vulgaris L., treated with concentrations of 2.5%, 5%, 10%, 15% and 20% were offered to insects together with untreated control leaves. Greater number of insects and leaves consumed were found on leaves treated with cucurbitacin-content formulation (2.5%, 5% – greatest response –, 10% and 15% concentrations) than on untreated control leaves. The concentration, in which responses were higher, was sprayed in a bean field at 1,000, 1,900 and 3,000 g ha-1. Greater number of beetles was found in plots treated with the highest dosage, 3 and 6 days after spraying. Ten days after spraying, no significant differences were found among dosages, probably due to washoff of the bait.O objetivo deste trabalho foi avaliar os efeitos alimentares estimulantes e arrestantes para Diabrotica speciosa (Ger.), a partir de formulações amiláceas com cucurbitacina, variando-se as fontes de amido e adicionando-se lignato de potássio. Em ensaio com lâmina de vidro, comparou-se a resistência à lavagem das formulações. O lignato de potássio não aumentou a resistência à lavagem. Pó de Lagenaria vulgaris L., cuja concentração de cucurbitacina B foi determinada como sendo de 0,28%, foi adicionado à formulação mais adesiva. O material resultante foi utilizado em ensaios com dupla chance de escolha, nos quais folhas de feijão, Phaseolus vulgaris L., pulverizadas com concentrações de 2,5%, 5%, 10%, 15% e 20% foram oferecidas aos insetos juntamente com folhas não tratadas. Foram observados maior número de insetos e maior quantidade de folhas consumidas nas folhas tratadas com formulações com cucurbitacina (2,5%, 5% – maior resposta –, 10% e 15%) do que nas folhas não tratadas. A formulação cuja concentração teve maior resposta foi pulverizada em lavoura de feijão, nas dosagens de 1.000, 1.900 e 3.000 g ha-1. O maior número de adultos de D. speciosa foi encontrado nas parcelas tratadas com a maior dosagem, aos 3 e 6 dias após a pulverização. Dez dias após a pulverização, não foram encontradas diferenças entre as dosagens, provavelmente por causa da lavagem da isca pelas chuvas

25 years of chemometrics in Brazil

Chemometric activities in Brazil are described according to three phases: before the existence of microcomputers in the 1970s, through the initial stages of microcomputer use in the 1980s and during the years of extensive microcomputer applications of the ´90s and into this century. Pioneering activities in both the university and industry are emphasized. Active research areas in chemometrics are cited including experimental design, pattern recognition and classification, curve resolution for complex systems and multivariate calibration. New trends in chemometrics, especially higher order methods for treating data, are emphasized.1401140

Procedimentos analíticos para identificação de antocianinas presentes em extratos naturais

Anthocyanins are among the most important plant pigments. Due to their potential benefits for human health, there is considerable interest in these natural pigments. Nonetheless, there is great difficulty in finding a technique that could provide the identification of structurally similar compounds and estimate the number and concentration of the species present. A lot of techniques have been tried to find the best methodology to extract information from these systems. In this paper, a review of the most important procedures is given, from the extraction to the identification of anthocyanins in natural extracts

Optimization of electrophoretic separations of thirteen phenolic compounds using single peak responses and an interactive computer technique

An interactive computer method is proposed for the electrophoretic separation of 13 phenolic compounds from extra-virgin olive oil using single peak response values. A central composite design was executed for optimization of the sodium tetraborate concentration, pH and applied voltage. Statistical models were determined for eight resolution responses and thirteen effective mobilities. Six of the resolution models had highly significant ANOVA lack of fit values, limiting their accuracies for use in Derringer´s desirability function search for optimal separation conditions. None of the 13 effective mobility models suffered from significant lack of fit. Since it is not possible to define effective mobility target values for the desirability function, an interactive computer program developed in our laboratories was applied to the single peak models. Mouse or cursor movements were executed to define experimental conditions in model simulations of the electropherogram. These simulations resulted in superior peak separations, especially for the apigenin and luteolin peaks, in 35 min, compared with those obtained in close to 50 min with the resolution models. Verification experiments performed 2 and 3 years later confirmed the robustness of the models.Um método computacional interativo foi desenvolvido para a separação eletroforética de 13 compostos fenólicos de azeite de oliva extravirgem, usando valores individuais de resposta para cada pico. Um planejamento composto central foi executado para a otimização da concentração de tetraborato de sódio, pH e voltagem aplicada. Foram determinados modelos estatísticos para oito respostas de resolução e treze de mobilidades efetivas. Seis modelos de resolução apresentaram significativa falta de ajuste após ANOVA, o que limitou sua acurácia para uso nas funções de desejabilidade de Derringer-Suich na busca pelas condições ótimas de separação. Nenhum dos 13 modelos de mobilidade efetiva apresentou falta de ajuste significativa. Visto que não foi possível definir valores alvos para as funções de desejabilidade, um programa de computador interativo, desenvolvido em nossos laboratórios, foi aplicado aos modelos individuais de cada pico. Movimentos do mouse ou do cursor foram executados para definir as condições experimentais nas simulações dos eletroferogramas. Essas simulações resultaram em uma melhor separação dos picos, especialmente para os picos de apigenina e luteolina, em 35 min, comparado aos obtidos para cerca de 50 min com os modelos de resolução. Experimentos de verificação executados 2 e 3 anos depois confirmaram a robustez dos modelos.17441753Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES