Short communication: plasma concentration of glucose-dependent insulinotropic polypeptide may regulate milk energy production in lactating dairy cows

In dairy cows, an increase in plasma concentration of glucose-dependent insulinotropic polypeptide (GIP) is associated with an increase in metabolizable energy intake, but the role of GIP in energy partitioning of dairy cattle is not certain. The objective of this study was to examine the relationship between plasma GIP concentrations and energy partitioning toward milk production. Four mid-lactation, primiparous, rumenfistulated Holstein-Friesian cows were fed a control diet of 55% forage and 45% concentrate [dry matter (DM) basis] in a 4 × 4 Latin square design with 4-wk periods. The 4 treatments were (1) control diet fed at 1000 and 1600 h, and (2) once-daily (1000 h) feeding, (3) twice daily (1000 and 1600 h) feeding, and (4) 4 times/d (1000, 1600, 2200 and 0400 h) feeding of the control diet plus 1 dose (1.75 kg on a DM basis at 0955 h) into the rumen of supplemental vegetable proteins (Amino Green; SCA NuTec Ltd., Thirsk, UK). Measurements of respiratory exchange and energy balance were obtained over 4 d during the last week of each period while cows were housed in open-circuit respiration chambers. Blood was collected from the jugular vein every 30 min for 12 h, using indwelling catheters, starting at 0800 h on d 20 of each period. Plasma GIP concentration was measured in samples pooled over each 5 consecutive blood samplings. The relationships between plasma GIP, DM intake, heat production, respiratory quotient, milk yield, and milk energy output were analyzed using linear correlation procedures, with metabolizable intake as a partial variant. Plasma GIP concentration was not correlated with heat production, or milk yield, but was positively correlated with milk energy yield (correlation coefficient = 0.67) and negatively correlated with RQ (correlation coefficient = −0.72). The correlations between GIP and RQ and milk energy output do not imply causality, but suggest that a role for GIP may exist in the regulation of energy metabolism in dairy cows.

Can physical exercise during gestation attenuate the effects of a maternal perinatal low-protein diet on oxygen consumption in rats?

A protocol of physical exercise, based on maximal oxygen uptake ((V) over dot(O2max)), for female rats before and during pregnancy was developed to evaluate the impact of a low-protein diet on oxygen consumption during gestation and growth rate of the offspring. Virgin female Wistar rats were divided into four groups as follows: untrained (NT, n = 5); trained (T, n = 5); untrained with low-protein diet (NT+LP, n = 5); and trained with low-protein diet (T+LP, n = 5). Trained rats were submitted to a protocol of moderate physical training on a treadmill over a period of 4 weeks (5 days week(-1) and 60 min day(-1), at 65% of (V) over dot(O2max)). At confirmation of pregnancy, the intensity and duration of the exercise was reduced. Low-protein groups received an 8% casein diet, and their peers received a 17% casein diet. The birthweight and growth rate of the pups up to the 90th day were recorded. Oxygen consumption ((V) over dot(O2)), CO(2) production and respiratory exchange ratio (RER) were determined using an indirect open-circuit calorimeter. Exercise training increased. (V) over dot(O2max) by about 20% when compared with the initial values (45.6 +/- 1.0 ml kg(-1) min(-1)). During gestation, all groups showed a progressive reduction in the resting (V) over dot(O2) values. Dams in the NT+LP group showed lower values of resting (V) over dot(O2) than those in the NT group. The growth rate of pups from low-protein-fed mothers was around 50% lower than that of their respective controls. The T group showed an increase in body weight from the 60th day onwards, while the NT+LP group presented a reduced body weight from weaning onwards. In conclusion, physical training attenuated the impact of the low- protein

Substitutional Impurities in PPV Crystals: An Intrinsic Donor-Acceptor System for High V(oc) Photovoltaic Devices

Defects are usually present in organic polymer films and are commonly invoked to explain the low efficiency obtained in organic-based optoelectronic devices. We propose that controlled insertion of substitutional impurities may, on the contrary, tune the optoelectronic properties of the underivatized organic material and, in the case studied here, maximize the efficiency of a solar cell. We investigate a specific oxygen-impurity substitution, the keto-defect -(CH(2)-C=O)- in underivatized crystalline poly(p-phenylenevinylene) (PPV), and its impact on the electronic structure of the bulk film, through a combined classical (force-field) and quantum mechanical (DFT) approach. We find defect states which suggest a spontaneous electron hole separation typical of a donor acceptor interface, optimal for photovoltaic devices. Furthermore, the inclusion of oxygen impurities does not introduce defect states in the gap and thus, contrary to standard donor-acceptor systems, should preserve the intrinsic high open circuit voltage (V(oc)) that may be extracted from PPV-based devices.

Investigation of the CO tolerance mechanism at several Pt-based bimetallic anode electrocatalysts in a PEM fuel cell

The electrocatalysis of CO tolerance of Pt/C, PtRu/C, PtFe/C, PtMo/C, and PtW/C at a PEM fuel cell anode has been investigated using single cell polarization and online electrochemical mass spectrometry (EMS) measurements, and cyclic voltammetry, X-ray diffraction (XRD), in situ X-ray absorption near edge structure (XANES) analyses of the electrocatalysts. For all bimetallic electrocatalysts, which presented higher CO tolerance, EMS results have shown that the production of CO(2) start at lower hydrogen electrode overpotentials as compared to Pt/C, confirming the occurrence of the so-called bifunctional mechanism. On the other hand, XANES results indicate an increase in the Pt 5d-band vacancies for the bimetallic catalysts, particulary for PtFe/C, this leading to a weakening of the Pt-CO bond, helping to increase the CO tolerance (the so-called electronic effect). For PtMo/C and PtRu/C supplied with H(2)/CO, the formation of CO(2) is observed even when the cell is at open circuit, confirming some elimination of CO by a chemical process, most probably the water gas shift reaction. (C) 2008 Elsevier Ltd. All rights reserved.

Estudos de Durabilidade Frente ao Ataque Ácido de Compósitos Portland-Polímero para Cimentação de Poços de Petróleo

Portland-polymers composites are promising candidates to be used as cementing material in Northeastern oil wells of Brazil containing heavy oils submitted to steam injection. In this way, it is necessary to evaluate its degradation in the commonly acidizind agents. In addition, to identify how aggressive are the different hostile environments it is an important contribution on the decision of the acidic systems to be used in. It was investigated the performance of the Portland-polymer composites using powdered polyurethane, aqueous polyurethane, rubber tire residues and a biopolymer, those were reinforced with polished carbon steel SAE 1045 to make the electrochemical measurements. HCl 15,0 %, HCl 6,0 % + HF 1,5 % (soft mud acid), HCl 12,0 % + HF 3,0 % (regular mud acid) and HAc 10 % + HF 1,5 % were used as degrading environment and electrolytes. The more aggressive acid solution to the plain Portland hardened cement paste was the regular mud acid, that showed loss of weight around 23.0 %, followed by the soft mud acid, the showed 11.0 %, 15.0 % HCl with 7,0 % and, at last the 10.0 % HAc plus HF 1.5 % with just 1.0 %. The powdered polyurethane-composite and the aqueous polyurethane one showed larger durability, with reduction around 87.0 % on the loss of weight in regular mud acid. The acid attack is superficial and it occurs as an action layer, where the degraded layer is responsible for the decrease on the kinetic of the degrading process. This behavior can be seen mainly on the Portland- aqueous polyurethane composite, because the degraded layer is impregnated with chemically modified polymer. The fact of the acid attack does not have influence on the compressive strength or fratography of the samples, in a general way, confirms that theory. The mechanism of the efficiency of the Portland-polymers composites subjected to acid attack is due to decreased porosity and permeability related with the plain Portland paste, minor quantity of Ca+2, element preferentially leached to the acidic solution, wave effect and to substitute part of the degrading bulk for the polymeric one. The electrolyte HAc 10 % + HF 1,5 % was the least aggressive one to the external corrosion of the casing, showing open circuit potentials around +250 mV compared to -130 mV to the simulated pore solution to the first 24 hours immersion. This behavior has been performed for two months at least. Similar corrosion rates were showed between both of the electrolytes, around 0.01 μA.cm-2. Total impedance values, insipient arcs and big polarization resistance capacitive arcs on the Nyquist plots, indicating passivity process, confirm its efficiency. In this way, Portlandpolymers composites are possible solutions to be succeed applied to oilwell cementing concomitant submitted to steam injection and acidizing operation and the HAc 10,0 % + HF 1,5 % is the less aggressive solution to the external corrosion of the casing

Desempenho de um painel fotovoltaico de baixa tensão, acoplado ao protótipo de um conversor dc/dc topologia Booster

Low voltage solar panels increase the reliability of solar panels due to reduction of in series associations the configurations of photovoltaic cells. The low voltage generation requires DCDC converters devices with high efficiency, enabling raise and regulate the output voltage. This study analyzes the performance of a photovoltaic panel of Solarex, MSX model 77, configured to generate an open circuit voltage of 10.5 V, with load voltage of 8.5 V, with short circuit current of 9 A and a power of 77 W. The solar panel was assembled in the isolated photovoltaic system configuration, with and without energy storage as an interface with a DCDC converter, Booster topology. The converter was designed and fabricated using SMD (Surface Mounted Devices) technology IC (integrated circuit) that regulates its output voltage at 14.2 V, with an efficiency of 87% and providing the load a maximum power of 20.88 W. The system was installed and instrumented for measurement and acquisition of the following data: luminosities, average global radiation (data of INPE Instituto Nacional de Pesquisas Espaciais), solar panel and environment temperatures, solar panel and DC-DC converter output voltages, panel, inverter, and battery charge output currents. The photovoltaic system was initially tested in the laboratory (simulating its functioning in ideal conditions of operation) and then subjected to testing in real field conditions. The panel inclination angle was set at 5.5°, consistent with the latitude of Natal city. Factors such as climatic conditions (simultaneous variations of temperature, solar luminosities and ra diation on the panel), values of load resistance, lower limit of the maximum power required by the load (20.88 W) were predominant factors that panel does not operate with energy efficiency levels greater than 5 to 6%. The average converter efficiency designed in the field test reached 95%

Análise aerodinâmica de perfis de asa para aeronaves experimentais tipo jn-1

The great importance in selecting the profile of an aircraft wing concerns the fact that its relevance in the performance thereof; influencing this displacement costs (fuel consumption, flight level, for example), the conditions of flight safety (response in critical condition) of the plane. The aim of this study was to examine the aerodynamic parameters that affect some types of wing profile, based on wind tunnel testing, to determine the aerodynamic efficiency of each one of them. We compared three types of planforms, chosen from considerations about the characteristics of the aircraft model. One of them has a common setup, and very common in laboratory classes to be a sort of standard aerodynamic, it is a symmetrical profile. The second profile shows a conFiguration of the concave-convex type, the third is also a concave-convex profile, but with different implementation of the second, and finally, the fourth airfoil profile has a plano-convex. Thus, three different categories are covered in profile, showing the main points of relevance to their employment. To perform the experiment used a wind tunnel-type open circuit, where we analyzed the pressure distribution across the surface of each profile. Possession of the drag polar of each wing profile can be, from the theoretical basis of this work, the aerodynamic characteristics relate to the expected performance of the experimental aircraft, thus creating a selection model with guaranteed performance aerodynamics. It is believed that the philosophy used in this dissertation research validates the results, resulting in an experimental alternative for reliable implementation of aerodynamic testing in models of planforms

Photoinduced hole-transfer in semiconducting polymer/low-bandgap cyanine dye blends: evidence for unit charge separation quantum yield

Power-conversion efficiencies of organic heterojunction solar cells can be increased by using semiconducting donor-acceptor materials with complementary absorption spectra extending to the near-infrared region. Here, we used continuous wave fluorescence and absorption, as well as nanosecond transient absorption spectroscopy to study the initial charge transfer step for blends of a donor poly(p-phenylenevinylene) derivative and low-band gap cyanine dyes serving as electron acceptors. Electron transfer is the dominant relaxation process after photoexcitation of the donor. Hole transfer after cyanine photoexcitation occurs with an efficiency close to unity up to dye concentrations of similar to 30 wt%. Cyanines present an efficient self-quenching mechanism of their fluorescence, and for higher dye loadings in the blend, or pure cyanine films, this process effectively reduces the hole transfer. Comparison between dye emission in an inert polystyrene matrix and the donor matrix allowed us to separate the influence of self-quenching and charge transfer mechanisms. Favorable photovoltaic bilayer performance, including high open-circuit voltages of similar to 1 V confirmed the results from optical experiments. The characteristics of solar cells using different dyes also highlighted the need for balanced adjustment of the energy levels and their offsets at the heterojunction when using low-bandgap materials, and accentuated important effects of interface interactions and solid-state packing on charge generation and transport.

Contribuições para a detecção e identificação de faltas em inversores Multiníveis

This work presents contributions in the detection and identication of faults in multilevel inverters through the study of the converters behavior under these operation conditions. Basically, the approached fault consists of an open-circuit in any switch of a three-level clamped diode inverter. The converter operation is characterized in the pre and post-fault states. A wave form behavior analysis of the pole voltage, phase current and dc-bus current is also done, which highlights characteristics that allow the detection of failure and, even, under favorable conditions, the identication of the faulty device. A compensation strategy of the approached fault (open-switch) is also investigated with the purpose of maintaining the driving system operational when a failure occurs. The proposed topology uses SCRs in parallel with the internal switches of the inverter, which allows, in some occasions, the full utilization of the dc-bus

Aplicação de técnicas eletroquímicas no estudo da dissolução oxidativa da covelita (CuS) por Thiobacillus ferrooxidans

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

Electron Transport in Dye-Sensitized Solar Cells Based on ZnO Nanotubes: Evidence for Highly Efficient Charge Collection and Exceptionally Rapid Dynamics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Approach on the Electrochemical Reactivity of Poly-L-Glutamic Acid Against Doxorubicin and Its Application in the Development of a Voltammetric Sensor

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

Thermogenic activity of growth hormone transgenic mice

The objective was to determine the effect of a mouse metallothionein/bovine growth hormone transgene on resting metabolic rate (RMR), cold-induced thermogenesis, and beta-agonist stimulated nonshivering thermogenesis in mice. Non-transgenic littermates were used as controls. Open-circuit indirect calorimetry was used to assess RMR and cold-induced thermogenesis in 64 mice. Air temperature in the chamber was set at 31 degrees C for RMR and was decreased to 28, 25, 21, or 17 degrees C to determine cold-induced thermogenesis. Response to the beta-agonist isoproterenol was evaluated by monitoring changes in colonic temperature of 34 mice upon injection of the drug or saline. Despite the fact that RMR tended to be lower in transgenics than in nontransgenics, at 31 degrees C transgenic mice were able to regulate colonic temperature at the same level as nontransgenics, but colonic temperature decreased in transgenics relative to nontransgenics as air temperature was reduced. For each degree decrease in air temperature between 31 and 17 degrees C, nontransgenic mice increased heat production by 1.03 +/- .10 watt/kg, whereas transgenic mice increased it by only .56 +/- .08 watt/kg, indicating that the thermogenic response of transgenics to cold was inferior. The magnitude of the maximal increase in colonic temperature after isoproterenol injection was similar for both groups, but the response was slower in transgenics. We suggest that lean body mass and substrate availability for shivering thermogenesis are reduced in transgenics relative to total body weight, and that they allow colonic temperature to decrease to conserve energy.

Effect of thermal conditioning during embryonic development on aspects of physiological responses of broilers to heat stress

The purpose of the present study was to investigate the effect of thermal conditioning, (through exposure to heat stress), during pre-hatch development on some physiological responses of post-hatch broilers to a post-natal heat stress challenge. Exposure to heat stress at this stage, we hope, may possibly induce epigenetic heat adaptation. Incubating eggs were exposed to temperature of 39.0degreesC for 2 h from Day 13 to 17 of incubation. At 33, 35, 37, 39, 41 and 43 d of age, the broilers hatched from these eggs were housed individually in open-circuit respiration cells. The climatic chambers were set to 22degreesC and increased to 30degreesC for 4 h. O-2 consumption and CO2 production of each chicken was monitored continuously in order to calculate the heat production. Blood samples were obtained before and during the 4 h heat stress. Thermal conditioning during incubation did not affect the plasma T-4, corticosterone, glucose, uric acid and CK concentrations. Temperature challenge, decreased plasma T-3 of broilers of both groups but the decrease was greater in pre-conditioned broilers compared with controls. A similar trend was observed for triglycerides. These changes did not affect total heat production. Since decreased T3 and triglyceride levels are part of the mechanisms for thermoregulation, these suggest that thermal conditioning during incubation can improve the broiler chicken capability for thermotolerance at later post-hatch age. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Corrosion behaviour of thermal sprayed nitinol coatings

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)