On the preparation of clean tungsten single crystals

The cleaning procedure consists of two-step-flashing: (i) cycles of low power flashes T similar to 1200 K) at an oxygen partial pressure of P(o2) = 6 x 10(-8) mbar, to remove the carbon from the surface, and (ii) a single high power flash (T similar to 2200 K), to remove the oxide layer. The removal of carbon from the surface through the chemical reaction with oxygen during low power flash cycles is monitored by thermal desorption spectroscopy. The exposure to O(2) leads to the oxidation of the W surface. Using a high power flash, the volatile W-oxides and the atomic oxygen are desorbed, leaving a clean crystal surface at the end of procedure. The method may also be used for cleaning other refractory metals like Mo, Re and It. (C) 2009 Elsevier B.V. All rights reserved.

Characterization and evaluation of BaCo0.7Fe0.2Nb0.1O3−δ as a cathode for proton-conducting solid oxide fuel cells

This study characterizes BaCo0.7Fe0.2Nb0.1O3−δ (BCFN) perovskite oxide and evaluates it as a potential cathode material for proton-conducting SOFCs with a BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte. A four-probe DC conductivity measurement demonstrated that BCFN has a modest electrical conductivity of 2–15 S cm−1 in air with p-type semiconducting behavior. An electrical conductivity relaxation test showed that BCFN has higher Dchem and Kchem than the well-known Ba0.5Sr0.5Co0.8Fe0.2O3−δ oxide. In addition, it has relatively low thermal expansion coefficients (TECs) with values of 18.2 × 10−6 K−1 and 14.4 × 10−6 K−1 at temperature ranges of 30–900 °C and 30–500 °C, respectively. The phase reaction between BCFN and BZCY was investigated using powder and pellet reactions. EDX and XRD characterizations demonstrated that BCFN had lower reactivity with the BZCY electrolyte than strontium-containing perovskite oxides such as SrCo0.9Nb0.1O3-δ and Ba0.6Sr0.4Co0.9Nb0.1O3−δ. The impedance of BCFN was oxygen partial pressure dependent. Introducing water into the cathode atmosphere reduced the size of both the high-frequency and low-frequency arcs of the impedance spectra due to facilitated proton hopping. The cathode polarization resistance and overpotential at a current density of 100 mA cm−2 were 0.85 Ω cm−2 and 110 mV in dry air, which decreased to 0.43 Ω cm−2 and 52 mV, respectively, in wet air (∼3% H2O) at 650 °C. A decrease in impedance was also observed with polarization time; this was possibly caused by polarization-induced microstructure optimization. A promising peak power density of ∼585 mW cm−2 was demonstrated by an anode-supported cell with a BCFN cathode at 700 °C.

Predicting migratory flight altitudes by physiological migration models

Using the altitudinal profiles of wind, temperature, pressure, and humidity in three flight models, we tried to explain the altitudinal distributions of nocturnal migrants recorded by radar above a desert in southern Israel. In the simplest model, only the tailwind component was used as a predictor of the most preferred flight altitude (T model). The energy model (E model) predicted flight ranges according to mechanical power consumption in flapping flight depending on air density and wind conditions, assuming optimal adjustment of airspeed and compensation of crosswinds, and including the influence of mass loss during flight. The energy-water model (EW model) used the same assumptions and parameters as the E model but also included restrictions caused by dehydration. Because wind was by far the most important factor governing altitudinal distribution of nocturnal migrants, differences in predictions of the three models were small. In a first approach, the EW model performed slightly better than the E model, and both performed slightly better than the T model. Differences were most pronounced in spring, when migrants should fly high according to wind conditions, but when climbing and descending they must cross lower altitudes where conditions are better with respect to dehydration. A simplified energy model (Es model) that omits the effect of air density on flight costs explained the same amount of variance in flight altitude as the more complicated E and EW models. By omitting the effect of air density, the Es model predicted lower flight altitudes and thus compensated for factors that generally bias height distributions downward but are not considered in the models (i.e. climb and descent through lower air layers, cost of ascent, and decrease of oxygen partial pressure with altitude). Our results confirm that wind profiles, and thus energy rather than water limitations, govern the altitudinal distribution of nocturnal migrants, even under the extreme humidity and temperature conditions in the trade wind zone.

Comparison of the cardio-respiratory effects of methadone and morphine in conscious dogs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Parâmetros hemogasométricos e equilíbrio ácido-básico de cabritos nascidos de partos normais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Control of respiration in fish, amphibians and reptiles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal evaporation furnace with improved configuration for growing nanostructured inorganic materials

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mixed ionic-electronic YSZ/Ni composite for SOFC anodes with high electrical conductivity

The preparation of the ZrO(2):8 mol % Y(2)O(3)/NiO (YSZ/NiO) composites by a modified liquid mixture technique is reported. Nanometric NiO particles dispersed over the yttria-stabilized zirconia (YSZ) were prepared, resulting in dense sintered specimens with no solid solution formation between the oxides. Such a feature allowed for the electrical characterization of the composites in a wide range of relative volume fraction, temperature, and oxygen partial pressure. The main results indicate that the composites have high electrical conductivity, and the transport properties in these mixed ionic-electronic (MIEC) composites are strongly dependent on the relative volume fraction of the phases, microstructure, and temperature. These parameters should hence be taken into consideration for the optimized design of MIEC composites for electrochemical applications. In this context, the composite was reduced under H(2) for the preparation of high-conductivity YSZ/Ni cermets for use as solid oxide fuel cell anode material with relatively low metal content. (c) 2005 the Electrochemical Society. [DOI:10.1149/1.2149312] All rights reserved.

Estudo de diferentes frações inspiradas de oxigênio em coelhos submetidos à hipovolemia aguda e anestesiados com isofluorano, associado ou não à infusão contínua de tramadol

Pós-graduação em Cirurgia Veterinária - FCAV

Estudo comparativo entre as ventilações espontânea, mandatória intermitente sincronizada, pressão de suporte e volume garantido e suporte pressórico, em coelhos anestesiados com propofol e induzidos à hipovolemia aguda

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Different fasting periods in tiletamine-zolezepam-anethetized cats: Glycemia, recovery, blood-gas and cardiorrespiratory parameters

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the vitality of nelore calves born of normal or dystocic parturitions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vacuum infiltration of copper aluminate by liquid aluminium

This paper studies attained microstructures and reactive mechanisms involved in vacuum infiltration of copper aluminate preforms with liquid aluminium. At high temperatures, under vacuum, the inherent alumina film enveloping the metal is overcome, and aluminium is expected to reduce copper aluminate, rendering alumina and copper. Under this approach, copper aluminate toils as a controlled infiltration path for aluminium, resulting in reactive wetting and infiltration of the preforms. Ceramic preforms containing a mixture of Al2O3 and CuAl2O4 were infiltrated with aluminium under distinct vacuum levels and temperatures, and the resulting reaction and infiltration behaviour is discussed. Copper aluminates stability ranges depend on vacuum level and oxygen partial pressure, which determine both CuAl2O4 and CuAlO2 ability for liquid aluminium infiltration. At 1100 °C and 0.76 atm vacuum level CuAl2O4 is stable, indicating pO2 above 0.11 atm. Reactive infiltration is achieved via reaction between aluminium and CuAl2O4; however, fast formation of an alumina film blocking liquid aluminium wicking results in incipient infiltration. At 1000 °C and 3.8 × 10−7 atm vacuum level, CuAlO2 decomposes to Cu and Al2O3 indicating a pO2 below 6.0 × 10−7 atm; infiltration of the ceramic is hindered by the non-wetting behaviour of the resulting metal alloy. At 1000 °C and 1.9 × 10−6 atm vacuum level CuAlO2 is stable, indicating pO2 above 6.0 × 10−7 atm. Extensive infiltration is achieved via redox reaction between aluminium and CuAlO2, rendering a microstructure characterised by uniform distribution of alumina particles amid an aluminium matrix. This work evidences that liquid aluminium infiltration upon copper aluminate-rich preforms is a feasible route to produce Al–matrix alumina-reinforced composites. The associated reduction reaction renders alumina, as fine particulate composite reinforcements, and copper, which dissolves in liquid aluminium contributing as a matrix strengthener.

Efeitos da interação da doxiciclina e adrenomedulina na embolia pulmonar aguda em ovinos anestesiados

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos da estabulação sobre o trato respiratório de equinos em dois tipos diferentes de camas e a pasto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)