Calcium tungstate (CaWO4) crystals were prepared by microwave-assisted hydrothermal (MAH) and polymeric precursor methods (PPM). These crystals were structurally characterized by X-ray diffraction (XRD), N2 adsorption, X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. The morphology and size of these crystals were observed by field emission scanning electron microscopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-Vis) absorption and photoluminescence (PL) measurements. Moreover, these materials were employed as catalysts towards gas phase toluene oxidation reaction. XRD indicates the purity of materials for both preparation methods and MAH process produced crystalline powders synthesized at lower temperatures and shorter processing time compared to the ones prepared by PPM. FE-SEM images showed particles with rounded morphology and particles in clusters dumbbells-like shaped. PL spectra exhibit a broad band covering the visible electromagnetic spectrum in the range of 360 to 750 nm. XANES and EXAFS results show that preparation method does not introduce high disorders into the structure, however the H2-TPR results indicated that the catalyst reducibility is affected by the preparation method of the samples.
In the present study, TiO2 nanopowder was partially coated with Y2O3 precursors generated by a sol-gel modified route. The system of nanocoated particles formed an ultra thin structure on the TiO2 surfaces. The modified nanoparticles were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) analysis, Zeta potential and surface area through N2 fisisorption measurements. Bioethanol dehydration was used as a probe reaction to investigate the modifications on the nanoparticles surface. The process led to the obtainment of nanoparticles with important surface characteristics and catalytic behavior in the bioethanol dehydration reaction, with improved activity and particular selectivity in comparison to their non-coated analogs. The ethylene production was disfavored and selectivity toward acetaldehyde, hydrogen and ethane increased over modified nanoparticles.
The increased preference for minimally processed vegetables has been attributed to the health benefits associated with fresh produce and the demand for ready-to-eat salads. In this paper, lettuce (Lactuca sativa L.) was evaluated for the effects of different cropping systems on the respiratory properties. Lettuce was packaged in low density polyethylene bags and stored in a refrigerator at 4 ºC. The concentration of carbon dioxide and oxygen inside the package was monitored during the storage at zero, three, six, eight, ten and twelve days by gas chromatography. Dry matter variation was measured gravimetrically up to day fourteen of storage. Values of respiratory rate for conventional lettuce increased from day 1 to 3 and remained low, while respiratory rate of the organic lettuce increased three-fold up to day 8, stabilizing at a high level. Variation in dry matter during storage also resulted from differences between the two cultivation systems. The highest content of dry matter was achieved by organic lettuce.
O aumento da preferência por hortaliças minimamente processada tem sido atribuído aos benefícios à saúde associado aos produtos frescos, bem como à demanda pelo consumo de salada pronta para o consumo. Neste trabalho, a alface americana (Lactuca sativa L.) foi avaliada quanto aos efeitos de diferentes sistemas de cultivo sobre as propriedades respiratórias. A alface foi acondicionada em sacos de polietileno de baixa densidade, conservada em refrigerador a 4 ºC. A concentração de dióxido de carbono e de oxigênio no interior das embalagens foi monitorada ao longo da conservação nos tempos 0, 3, 6, 8, 10 e 12 dias por cromatografia gasosa e a variação da matéria seca foi avaliada por gravimetria até o décimo quarto dia de conservação. O valor do padrão respiratório na alface convencional aumentou do primeiro ao terceiro dia e se manteve baixo, enquanto a orgânica aumentou a taxa respiratória até três vezes até o oitavo dia, estabilizando em alto nível. O sistema de cultivo também resultou em diferenças na variação da matéria seca durante o armazenamento. O mais elevado conteúdo de matéria seca foi atingido pela alface americana orgânica.
The purpose of the study was to analyse the effects of a short-term, high-intensity inspiratory muscle training (IMT) on healthy youth maximal respiratory pressures, with and without arm bracing postures. Thirty young women were randomly assigned to three groups: control group (CG); group training with no arm bracing (NAB); and group training with arm bracing (AB). The IMT consisted of three 10-minute daily supervised sessions for three consecutive days. Before, at the end, and one month after the end of training, subjects' maximal inspiratory pressures (MIP) and maximal expiratory pressures (MEP) were assessed. In NAB group a significant increase in MIP was found, from -75±10 to -97±14 cmH2O (p<0.001) and one month later (-99±14 cmH2O, p<0.001). Similarly, in AB group, MIP significantly raised from 77±17 to -96±20 cmH2O (p<0.001), which was maintained one month later (-96±23 cmH2O, p<0.001). No significant difference was found between the two groups final MIP (p>0.05). As to MEP, only in AB group a significant increase on final MEP was found, from 99±16 to 112±16 cmH2O, p<0.05), followed by a decrease one month later (101±19 cmH2O, p<0.05). Hence in young healthy women a short-term, high-intensity IMT protocol increases inspiratory muscle strength independently of arm positioning, simultaneous to an increase in expiratory muscle strength when the IMT is performed with arm bracing.
O objetivo do estudo foi analisar os efeitos de um treinamento muscular inspiratório (TMI) de curta duração e alta intensidade, com e sem o apoio de membros superiores, sobre as pressões respiratórias máximas em jovens saudáveis. Trinta jovens do sexo feminino foram aleatoriamente distribuídas em três grupos: o grupo controle (GC) fez treinamento placebo na posição sentada; o grupo GSA treinou em pé sem apoio de membros superiores; e o grupo GCA treinou com apoio de membros superiores. O TMI consistiu em três sessões diárias de 10 minutos em três dias consecutivos. Antes, ao final e após um mês do final do treino foram avaliadas a pressão inspiratória máxima (PImáx) e a pressão expiratória máxima (PEmáx). No GSA, houve aumento significante da PImáx após o treino de -75±10 para -97±14 cmH2O (p<0,001) e após um mês (-99±14 cmH2O; p<0,001). O mesmo ocorreu no GCA: a PImáx passou de -77±18 para -96±20 cmH2O (p<0,001), mantendo-se após um mês (-96±23 cmH2O, p<0,001). Não houve diferença entre a PImáx final dos dois grupos. Quanto à PEmáx, apenas no GCA houve aumento significante, de 99±16 para 112±16 cmH2O (p<0,05), seguida de diminuição após um mês (101±19 cmH2O, p<0,05). Em jovens saudáveis do sexo feminino, um TMI de curta duração e alta intensidade gera aumento da força muscular inspiratória independente do posicionamento dos braços; e aumento da força expiratória quando o treinamento é feito com os membros superiores apoiados.
The carbon dioxide reforming of methane was carried out over nickel catalysts supported on the gamma-Al2O3/CeO2 system prepared by wet impregnation. With the increase of the CeO2 weight in the catalyst, a higher stability was observed in the catalytic activity, together with an excellent resistance to carbon deposition and a better Ni dispersion. The catalysts were characterized by means of surface area measurements, TPR, H2 chemisorption, XRD, SEM, EDX, XPS and TEM. An interaction between Ni and CeO2 was observed to the Ni/CeO2 sample after activation in a H2 atmosphere above 300 ºC. Such behavior has a significantly influence on the catalytic activity.