Evaluation of water and sucrose diffusion coefficients in potato tissue during osmotic concentration

The water and sucrose effective diffusion coefficients behavior were studied in potato tubers immersed in aqueous sucrose solution, 50% (w/,A), at 27 degreesC. Water and sucrose concentration profiles were measured as function of the position for 3, 6 and 12 h of immersion. These were adjusted to a mathematical model for three components that take into account the bulk flow in a shrinking tissue and the concentration dependence of the diffusion coefficients.The binary effective coefficients were an order of magnitude lower than those for pure solutions of sucrose. These coefficients show an unusual concentration dependence. Analysis of these coefficients as functions of the concentration and position demonstrates that, cellular tissue promotes high resistance to diffusion in the tuber and also the elastic contraction of material influences the species diffusion. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

EVALUATION OF DIFFUSION-COEFFICIENTS IN OSMOTIC CONCENTRATION OF BANANAS (MUSA-CAVENDISH LAMBERT)

The effect of time of exposure, solution concentration and temperature on the osmotic concentration of banana (slices of 11 mm thickness) was studied in aqueous sucrose solutions. The selectivity of the cellular tissues was reduced by steam blanching the banana slices before osmotic treatment. Effective diffusion coefficients for the loss of water and the increase in sucrose content were determined according to Fick's Law applied to a two-dimensional body; calculated on the basis of the concentration of various components in the liquid phase impenetrating the fruit. These coefficients revealed values similar to binary diffusion coefficients for pure sucrose solutions.

Temperature and concentration dependence of density of model liquid foods

Density of binary solutions and combinations of sucrose, glucose, fructose, citric acid, malic acid, pectin, and inorganic salts were measured with an oscillating tube density meter in the temperature range from 10degrees to 60degreesC, at varying concentrations. Density can be predicted with accuracy better than 5 x 10(-5) g cm(-3) using predictive equations obtained by fitting the experimental data. Available literature values agreed well with experimental data. Relations for the excess molar volume of these solutions were derived in terms of mole fraction and temperature. A thermodynamic model for the volumetric analysis of multicomponent aqueous solutions containing electrolyte and non-electrolyte compounds was also proposed. These models can be used for prediction of density of liquid food systems, specially fruit juices and beverages, based on composition and temperature, with high accuracy and without elaborate experimental work.

Maximal lactate steady state concentration independent of pedal cadence in active individuals

The maximal lactate steady state (MLSS) is defined as the highest blood lactate concentration that can be maintained over time without a continual blood lactate accumulation. The objective of the present study was to analyze the effects of pedal cadence (50 vs. 100 rev min(-1)) on MLSS and the exercise workload at MLSS (MLSSworkload) during cycling. Nine recreationally active males (20.9 +/- 2.9 years, 73.9 +/- 6.5 kg, 1.79 +/- 0.09 m) performed an incremental maximal load test (50 and 100 rev min(-1)) to determine anaerobic threshold (AT) and peak workload (PW), and between two and four constant submaximal load tests (50 and 100 rev min(-1)) on a mechanically braked cycle ergometer to determine MLSSworkload and MLSS. MLSSworkload was defined as the highest workload at which blood lactate concentration did not increase by more than 1 mM between minutes 10 and 30 of the constant workload. The maximal lactate steady state intensity (MLSSintensity) was defined as the ratio between MLSSworkload and PW. MLSSworkload (186.1 +/- 21.2 W vs. 148.2 +/- 15.5 W) and MLSSintensity (70.5 +/- 5.7% vs. 61.4 +/- 5.1%) were significantly higher during cycling at 50 rev min(-1) than at 100 rev min(-1), respectively. However, there was no significant difference in MLSS between 50 rev min(-1) (4.8 +/- 1.6 mM) and 100 rev min(-1) (4.7 +/- 0.8 mM). We conclude that MLSSworkload and MLSSintensity are dependent on pedal cadence (50 vs. 100 rev min(-1)) in recreationally active individuals. However, this study showed that MLSS is not influenced by the different pedal cadences analyzed.

Effect of thermal stress on physiological parameters, feed intake and plasma thyroid hormones concentration in Alentejana, Mertolenga, Frisian and Limousine cattle breeds

The aim of the present study was to assess the heat tolerance of animals of two Portuguese (Alentejana and Mertolenga) and two exotic (Frisian and Limousine) cattle breeds, through the monitoring of physiological acclimatization reactions in different thermal situations characterized by alternate periods of thermoneutrality and heat stress simulated in climatic chambers. In the experiment, six heifers of the Alentejana, Frisian and Mertolenga breeds and four heifers of the Limousine breed were used. The increase in chamber temperatures had different consequences on the animals of each breed. When submitted to heat stress, the Frisian animals developed high thermal polypnea (more than 105 breath movements per minute), which did not prevent an increase in the rectal temperature (from 38.7 degrees C to 40.0 degrees C). However, only a slight depression in food intake and in blood thyroid hormone concentrations was observed under thermal stressful conditions. Under the thermal stressful conditions, Limousine animals decreased food intake by 11.4% and blood triiodothyronine (T3) hormone concentration decreased to 76% of the level observed in thermoneutral conditions. Alentejana animals had similar reactions. The Mertolenga cattle exhibited the highest capacity for maintaining homeothermy: under heat stressful conditions, the mean thermal polypnea increased twofold, but mean rectal temperature did not increase. Mean food intake decreased by only 2% and mean T3 blood concentration was lowered to 85,6% of the concentration observed under thermoneutral conditions. These results lead to the conclusion that the Frisian animals had more difficulty in tolerating high temperatures, the Limousine and Alentejana ones had an intermediate difficulty, and the Mertolenga animals were by far the most heat tolerant.

The Role of the Eu3+ Concentration on the SrMoO4:Eu Phosphor Properties: Synthesis, Characterization and Photophysical Studies

SrMoO4 doped with rare earth are still scarce nowadays and have attracted great attention due to their applications as scintillating materials in electro-optical like solid-state lasers and optical fibers, for instance. In this work Sr1-xEuxMoO4 powders, where x = 0.01; 0.03 and 0.05, were synthesized by Complex Polymerization (CP) Method. The structural and optical properties of the SrMoO4:Eu3+ were analyzed by powder X-ray diffraction patterns, Fourier Transform Infra-Red (FTIR), Raman Spectroscopy, and through Photoluminescent Measurements (PL). Only a crystalline scheelite-type phase was obtained when the powders were heat-treated at 800 A degrees C for 2 h, 2 theta = 27.8A degrees (100% peak). The excitation spectra of the SrMoO4:Eu3+ (lambda(Em.) = 614 nm) presented the characteristic band of the Eu3 + 5L6 transition at 394 nm and a broad band at around 288 nm ascribed to the charge-transfer from the O (2p) state to the Mo (4d) one in the SrMoO4 matrix. The emission spectra of the SrMoO4:Eu3+ powders (lambda(Exc.) = 394 and 288 nm) show the group of sharp emission bands among 523-554 nm and 578-699 nm, assigned to the D-5(1)-> F-7(0,1and 2) and D-5(0)-> F-7(0,1,2,3 and 4), respectively. The band related to the D-5(0)-> F-7(0) transition indicates the presence of Eu3+ site without inversion center. This hypothesis is strengthened by the fact that the band referent to the D-5(0)-> F-7(2) transition is the most intense in the emission spectra.

Effect of Ag concentration on the thermal behavior of the Cu-10 mass% Al and Cu-11 mass% Al alloys

In this work the effect of Ag concentration on the thermal behavior of the Cu-10 mass% Al and Cu-11 mass% Al alloys with additions of 4, 6, 8 and 10 mass% Ag was studied using differential scanning calorimetry (DSC), in situ X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results showed that for the Cu-10 mass% Al alloy Ag addition induce the beta'(1) phase formation and for the Cu-11 mass% Al alloy these additions increase the amount of martensite formed on quenching and decrease the stability range of this phase on heating.

Influence of Ca concentration on the electric, morphological, and structural properties of (Pb,Ca)TiO3 thin films

Pb1-xCaxTiO3 (0.10less than or equal toxless than or equal to0.40) thin films on Pt/Ti/SiO2/Si(100) substrates were prepared by the soft solution process and their characteristics were investigated as a function of the calcium content (x). The structural modifications in the films were studied using x-ray diffraction and micro-Raman scattering techniques. Lattice parameters calculated from x-ray data indicate a decrease in lattice tetragonality with the increasing content of calcium in these films. Raman spectra exhibited characteristic features of pure PbTiO3 thin films. Variations in the phonon mode wave numbers, especially those of lower wave numbers, of Pb1-xCaxTiO3 thin films as a function of the composition corroborate the decrease in tetragonality caused by the calcium doping. As the Ca content (x) increases from 0.10 to 0.40, the dielectric constant at room temperature abnormally increased at 1 kHz from 148 to 430. Also calcium substitution decreased the remanent polarization and coercive field from 28.0 to 5.3 muC/cm(2) and 124 to 58 kV/cm, respectively. These properties can be explained in terms of variations of phase transition (ferroelectric-paraelectric), resulting from the substitution the lead site of PbTiO(3)for the nonvolatile calcium. (C) 2002 American Institute of Physics.

LH and FSH concentration and follicular development in Nellore heifers submitted to fixed-time artificial insemination protocols with different progesterone concentrations

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