Water activity of aqueous solutions of ethylene oxide-propylene oxide block copolymers and maltodextrins

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

Exothermic Behavior, Degree of Conversion, and Viscoelastic Properties of Experimental and Commercially Available Hard Chairside Reline Resins

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Combined experimental and theoretical investigations of the photoluminescent behavior of Ba(Ti,Zr)O-3 thin films

The correlation between experimental data and theoretical calculations have been investigated to explain the photoluminescence at room temperature of Ba(Ti0.75Zr0.25)O-3 (BTZ) thin films prepared by the polymeric precursor method. The degree of structural order-disorder was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectroscopy and photoluminescence (PL) measurements. First-principles quantum mechanical calculations based on density functional theory (B3LYP level) were employed to study the electronic structure of ordered and deformed asymmetric models. The electronic properties are analyzed and the relevance of the present theoretical and experimental results on the PL behavior is discussed. The presence of localized electronic levels and a charge gradient in the band gap due to a break in symmetry, are responsible for the PL in disordered BTZ lattice. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Experimental and theoretical study on the piezoelectric behavior of barium doped PZT

An experimental and theoretical study of the ferroelectric and piezoelectric behavior of PZT doped with barium is presented. Ab initio perturbed ion calculations was carried out. The properties, such as remnant polarization, coercive field and the coupling factor of the PZT at constant sintering temperature was compared with the Zr4+/Ti4+ ions dislocation energy and the lattice interaction energy. An agreement between the experimental and theoretical results, with a decrease of the interaction energy and an inversion of the energy stability from tetragonal to rhombohedral phase was observed. (C) 1999 Kluwer Academic Publishers.

Experimental and theoretical study of the ferroelectric and piezoelectric behavior of strontium-doped PZT

Theoretical data using ab initio perturbed ion calculation were compared with ferroelectric and piezoelectric experimental data of strontium doped PZT. Various concentrations of SrO in PZT at constant temperature and sintering time were carried out. Experimental results, such as the remanent polarization, P-R of 6.9-8.9 muC/Cm-2, the coercive field, E-C of 6.6-7.8 kVcm, and the planar coupling factor, Kp of 0.45-0.53, were compared with the energy of Zr4+ and Ti4+ ion dislocation and the lattice interaction energy which show that strontium increment in PZT alter the energies and increase the values of piezoelectric and ferroelectric variables. Calculations of lattice energy of the rhombohedral phase show that a phase non-stability is coincident with increasing experimental values of the P-R, E-C and Kp. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

On the stabilizing behavior of zirconia: A combined experimental and theoretical study

Reactive zirconia powder was synthesized by the complexation of zirconium metal from zirconium hydroxide using a solution of 8-hydroxiquinoline. The kinetics of zirconia crystallization was followed by X-ray diffraction, scanning electron microscopy and surface area measured by the nitrogen adsorption/desorption technique. The results indicated that zirconia with a surface area as high as 100 m(2)/g can be obtained by this method after calcination at 500degreesC. Zirconia presents three polymorphic phases (monoclinic, tetragonal and cubic), which are reversibly interconversible. The cluster model Zr4O8 and Z(r)4O(7)(+2) was used for a theoretical study of the stabilization process. The ab initio RHF method was employed with the Gaussian94 program and the total energies and the energy gap of the different phases were calculated and compared with the experimental energy gap. The theoretical results show good reproducibility of the energy gap for zirconia. (C) 2004 Kluwer Academic Publishers.

The dynamic behavior of a cantilever beam coupled to a non-ideal unbalanced motor through numerical and experimental analysis

An excitation force that is not influenced by the system state is said to be an ideal energy source. In real situations, a direct and feedback coupling between the excitation source and the system must always exist at a certain level. This manifestation of the law of conservation of energy is known as the Sommerfeld effect. In the case of obtaining a mathematical model for such a system, additional equations are usually necessary to describe the vibration sources with limited power and its coupling with the mechanical system. In this work, a cantilever beam and a non-ideal DC motor fixed to its free end are analyzed. The motor has an unbalanced mass that provides excitation to the system which is proportional to the current applied to the motor. During the coast up operation of the motor, if the drive power is increased slowly, making the excitation frequency pass through the first natural frequency of the beam, the DC motor speed will remain the same until it suddenly jumps to a much higher value (simultaneously its amplitude jumps to a much lower value) upon exceeding a critical input power. It was found that the Sommerfeld effect depends on some system parameters and the motor operational procedures. These parameters are explored to avoid the resonance capture in the Sommerfeld effect. Numerical simulations and experimental tests are used to help gather insight of this dynamic behavior. (C) 2014 Elsevier Ltd. All rights reserved.

Comportamento da pressão intra-ocular segundo os efeitos cardiorrespiratórios e hemodinâmicos induzidos pela anestesia com desflurano, em cães submetidos à hipovolemia experimental

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

Canopy characteristics and behavior of Nellore heifers in Brachiaria brizantha pastures under different grazing heights at a continuous stocking rate

The objective of this study was to evaluate the Brachiaria brizantha cv. Marandu canopy structure maintained at different grazing heights under a continuous stocking rate and with a dietary supplementation strategy for the animals during the rainy season. This study also intended to observe the relationships of these variables with the grazing behaviors of the heifers. The effects of three canopy heights (15, 25 and 35 cm) were evaluated in association with three types of supplements: one mineral and two protein/energy supplements, the first with a high rumen degradable protein and energy and the others with a low ratio. Both the protein/energy supplements were provided at 0.3% of body weight/day. The experimental design was completely randomized, with two replications and repeated measures, and took place during the period from January to April 2008. The supplementation strategies did not affect any variable related to the canopy structure. Total and green herbage masses and the ratio of green/dead material increased with canopy height. The leaf/stem ratio was higher in the lowest canopy height: 15 cm. Changes in the canopy structure caused variations in the grazing behavior of the animals. Animals maintained in the 15-cm-tall pasture grazed for a longer time, increasing the time for each meal, but the number of meals was lower than that of the animals grazing within the 35-cm-tall pasture. The grazing time of animals receiving the energy/protein supplement was lower only in the period of the day during which it was supplied. Canopy structure is affected by sward height, and changes animal behavior. Supplementation does not affect the canopy structure of the pastures with similar heights.

Characteristics of forage and feeding behavior of Nellore heifers fed hydrolyzed sugarcane

The objective of this study was to evaluate the chemical characteristics of the forage and ingestive behavior of Nellore heifers fed hydrolyzed sugarcane in different periods of storage. Twenty-four heifers with initial body weight of 119.6±8.1 kg were utilized. The experimental design was completely randomized, in which the treatments were diets with fresh sugarcane and hydrolyzed sugarcane (5 g of lime kg-1 of chopped sugarcane) stored for 24, 48 or 72 hours as the only roughage. The addition of lime to sugarcane associated with its storage up to 72 hours provided an increase of 20% of the potentially degradable cell wall of carbohydrates, from 382.4 to 458.8 g kg-1 of total carbohydrates. The in vitro digestibility of dry matter was altered by the storage of hydrolyzed sugarcane, increasing 7.08% when the storage time was increased from 24 to 72 hours. Heifers fed fresh sugarcane remained more time consuming compared with heifers fed other diets. The time used for water intake was not influenced by the diet. The rumination time presented a quadratic variation in relation to storage time of the hydrolyzed sugarcane, with higher values for the of hydrolyzed sugarcane diets stored for 48 hours. Heifers fed hydrolyzed sugarcane spent more time on other activities than those fed fresh sugarcane. The supply of hydrolyzed sugarcane stored up to 72 hours in the proportion of 600 g kg-1 of dry matter in the diet, alters the intake patterns, reducing the feed intake in Nellore heifers.

Aggressive behavior in the genus Gallus sp

The intensification of the production system in the poultry industry and the vertical integration of the poultry agribusiness have brought profound changes in the physical and social environment of domestic fowls in comparison to their ancestors and have modified the expression of aggression and submission. The present review has covered the studies focusing on the different aspects linked to aggressiveness in the genus Gallus. The evaluated studies have shown that aggressiveness and subordination are complex behavioral expressions that involve genetic differences between breeds, strains and individuals, and differences in the cerebral development during growth, in the hormonal metabolism, in the rearing conditions of individuals, including feed restriction, density, housing type (litter or cage), influence of the opposite sex during the growth period, existence of hostile stimuli (pain and frustration), ability to recognize individuals and social learning. The utilization of fighting birds as experimental material in the study of mechanisms that have influence on the manifestation of aggressiveness in the genus Gallus might comparatively help to elucidate important biological aspects of such behavior.

Evaluation of thermal behavior of latex membranes from genetically improved rubber tree (Hevea brasiliensis)

Thermal stability, thermal decomposition process, residual mass, temperature of glass transition (T-g) and temperature dependence of storage modulus (E'), were determined for latex membranes prepared from six clones of Hevea brasiliensis: IAC 331, IAC 332, IAC 333 and IAC 334 grown at experimental plantations of Instituto Agronomico de Campinas (IAC) in Votuporanga, São Paulo State, Brazil. Latex membranes from GT1 and RRIM 600 Asian matrix clones were used as references. The thermal behavior of latex membranes from genetically improved rubber trees was characterized using thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The thermal behavior of latex from clones studied in the present work showed similar features of the clones previously reported (IAC 40, IAC 300, IAC 301, IAC 328, IAC 329 and IAC 330), with mass loss in four consecutive steps, except IAC 333, which showed an additional mass loss step. (c) 2006 Elsevier B.V. All rights reserved.

Stretch Injuries of Skeletal Muscles: Experimental Study in Rats' Soleus Muscle

The study aimed to verify the physiological injury behavior by stretching the soleus muscle of rats, using a noninvasive experimental model. Twenty-four rats were used and divided into three groups of eight animals: control group (A), group that performed tetanus followed by electrical stimulation and a sudden dorsiflexion of the left paw performed by a device equipped with a mechanism of muscle soleus rapid stretching (B); and a group that only received the tetanus (C). Three days later, the animals were killed, and the soleus muscle was resected and divided into three segments. Morphological changes indicative of muscle damage appeared in all three segments of group B. In a lesser degree, similar changes were also detected in muscles subjected to only tetanus. This model was effective; reproducing an injury similar to what occurs in human sports injuries.

Stress induces behavioral sensitization, increases nicotine-seeking behavior and leads to a decrease of CREB in the nucleus accumbens

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

Toward an understanding of intermediate- and short-range defects in ZnO single crystals. A combined experimental and theoretical study

A joint use of experimental and theoretical techniques allows us to understand the key role of intermediate- and short-range defects in the structural and electronic properties of ZnO single crystals obtained by means of both conventional hydrothermal and microwave-hydrothermal synthesis methods. X-ray diffraction, Raman spectra, photoluminescence, scanning electronic and transmission electron microscopies were used to characterize the thermal properties, crystalline and optical features of the obtained nano and microwires ZnO structures. In addition, these properties were further investigated by means of two periodic models, crystalline and disordered ZnO wurtzite structure, and first principles calculations based on density functional theory at the B3LYP level. The theoretical results indicate that the key factor controlling the electronic behavior can be associated with a symmetry breaking process, creating localized electronic levels above the valence band.