Influence of heat treatment on LiNbO3 thin films prepared on Si(111) by the polymeric precursor method

The effects of heat-treatment temperature on LiNbO3 thin films prepared by the polymeric precursor method were investigated. The precursor solution was deposited on Si(111) substrates by dip coating. X-ray diffraction and thermal analyses revealed that the crystallization process occurred at a low temperature (420 °C) and led to films with no preferential orientation. High-temperature treatments promoted formation of the LiNb3O8 phase. Scanning electron microscopy, coupled with energy dispersive spectroscopy analyses, showed that the treatment temperature also affected the film microstructure. The surface texture - homogeneous, smooth, and pore-free at low temperature - turned into an `islandlike' microstructure for high-temperature treatments.

Behavior of the PMD coefficient of optical links under influence of mechanical and thermal effects

This papers presents results on the variation of the PMD coefficient of optical links under influence of mechanical tests, such as tensile strength, bending and compression, and also during the application of a thermal cycle. Results revealed that the link coefficient is more influenced by the application of a tension load and also suffers significant variation under strong temperature changes. Copyrigth © SBMO.

The influence of fluid ingestion on performance of soccer players during a match

The purpose of this study was to verify the effects of a carbohydrate-electrolyte drink on soccer performance. Twenty soccer players volunteered to participate in the study. Players were allocated to two assigned trials according to their positional roles in the team: CHO group (ingesting a 6% carbohydrate-electrolyte solution at regular 15 minutes intervals) and NCHO (ingesting no fluid) during 75 min on-field soccer game. During the trials, body mass loss, heart rate, time spent running, number of sprints and core temperature were measured. There were statistically significant changes (p < 0.05) in body mass loss (CHO: 1.14 ± 0.37 kg vs. NCHO: 1.75 ± 0.47 kg) and number of sprints performed (CHO: 14.70 ± 4.38 vs. NCHO: 10.70 ± 5.80) between groups. The main finding of the present study indicates that supplementation with a carbohydrate-electrolyte drink during a soccer match is beneficial in helping to prevent deterioration in performance. © Journal of Sports Science and Medicine (2004).

Shear bond strength of adhesive systems to enamel and dentin. Thermocycling influence

Objectives: The purpose of the this study was to evaluate the influence of thermocycling on shear bond strength on bovine enamel and dentin surfaces of different adhesive systems. Methods: Thirty sound bovine incisors were sectioned in mesiodistal and inciso-cervical direction obtaining 60 incisal surfaces (enamel) and 60 cervical surfaces (dentin). Specimens were randomly assigned to 3 groups of equal size (n = 40), according to the adhesive system used: I-Single Bond; II-Prime & Bond NT/NRC; III-One Coat Bond. After 24-h storage in distilled water at 37 o C, each main group was divided into two subgroups: A- specimens tested after 24 h storage in distilled water at 37°C; B - specimens submitted to thermocycling (500 cycles). Shear bond strength tests were performed. Data were submitted to ANOVA and Tukey test. Results: Means (MPa) of different groups were: I-AE-16.96, AD-17.46; BE-21.60, BD-12.79; II-AE-17.20, AD-11.93; BE-20.67, BD-13.94; III-AE-25.66, AD-17.53; BE-24.20, BD-19.38. Significance: Thermocycling did not influence significantly the shear bond strength of the tested adhesive systems; enamel was the dental substrate that showed larger adhesive strength; One Coat Bond system showed the best adhesive strength averages regardless of substrate or thermocycling. © 2005 Springer Science + Business Media, Inc.

Influence of brush type as a carrier of adhesive solutions and paper points as an adhesive-excess remover on the resin bond to root dentin

Purpose: To evaluate the influence of the brush type as a earner of priming adhesive solutions and the use of paper points as a remover of the excess of these solutions on the push-out bond strength of resin cement to bovine root dentin. The null hypotheses were that brush type and the use of paper points do not affect the bond strength. Materials and Methods: The canals of 80 single-root bovine roots (16 mm in length) were prepared at 12 mm using the preparation drill (FRC Postec Plus, Ivoclar). Half of each root was embedded in acrylic resin and the specimens were divided into 8 groups, considering the factors brush type (4 levels) and paper point (2 levels) (n = 10): Gr 1: small microbrush (Cavi-Tip, SDI); Gr 2: Microbrush (Dentsply); Gr 3: Endobrush (Bisco); Gr 4: conventional brush (Bisco); Gr 5: Cavi-Tip (SDI) + paper points; Gr 6: Microbrush (Dentsply) + paper points; Gr 7: Endobrush (Bisco) + paper points; Gr 8: conventional brush (Bisco) + paper points. The root dentin was treated with a multistep total-etch adhesive system (All Bond 2). The adhesive system was applied using each microbrush, with and without using paper points. One fiber post was molded with addition silicon and 80 posts were made of resin cement (Duolink), The resin posts were luted (Duolink resin cement), and the specimens were stored for 24 h in water at 37°C. Each specimen was cut into 4 disk-shaped samples (1.8 mm in thickness), which were submitted to the push-out test. Results: The brush type (p < 0.0001) (small microbrush > microbrush = endobrush = conventional brush) and the use of paper points (p = 0.0001) (with > without) influenced the bond strength significantly (two-way ANOVA). The null hypotheses were rejected. Conclusion: The smallest brush (Cavi-Tip) and the use of paper points significantly improved the resin bond to bovine root dentin.

The influence of the loop between residues 223-235 in beetle luciferase bioluminescence spectra: A solvent gate for the active site of pH-sensitive luciferases

Beetle luciferases emit a wide range of bioluminescence colors, ranging from green to red. Firefly luciferases can shift the spectrum to red in response to pH and temperature changes, whereas click beetle and railroadworm luciferases do not. Despite many studies on firefly luciferases, the origin of pH-sensitivity is far from being understood. Through comparative site-directed mutagenesis and modeling studies, using the pH-sensitive luciferases (Macrolampis and Cratomorphus distinctus fireflies) and the pH-insensitive luciferases (Pyrearinus termitilluminans, Phrixotrix viviani and Phrixotrix hirtus) cloned by our group, here we show that substitutions dramatically affecting bioluminescence colors in both groups of luciferases are clustered in the loop between residues 223-235 (Photinus pyralis sequence). The substitutions at positions 227, 228 and 229 (P. pyralis sequence) cause dramatic redshift and temporal shift in both groups of luciferases, indicating their involvement in labile interactions. Modeling studies showed that the residues Y227 and N229 are buried in the protein core, fixing the loop to other structural elements participating at the bottom of the luciferin binding site. Changes in pH and temperature (in firefly luciferases), as well as point mutations in this loop, may disrupt the interactions of these structural elements exposing the active site and modulating bioluminescence colors. © 2007 The Authors.

Influence of microwave polymerization method and thickness on porosity of acrylic resin

Purpose: This study evaluated the influence of polymerization cycle and thickness of maxillary complete denture bases on the porosity of acrylic resin. Materials and Methods: Two heat-activated denture base resins - one conventional (Clássico) and one designed for microwave polymerization (Onda-Cryl) - were used. Four groups were established, according to polymerization cycles: A (Onda-Cryl, short microwave cycle), B (Onda-Cryl, long microwave cycle), C (Onda-Cryl, manufacturing microwave cycle), and T (Clássico, water bath). Porosity was evaluated for different thicknesses (2.0, 3.5, and 5.0 mm; thicknesses I, II, and III, respectively) by measurement of the specimen volume before and after its immersion in water. The percent porosity data were submitted to Kruskal-Wallis for comparison among the groups. Results: The Kruskal-Wallis test detected that the combinations of the different cycles and thicknesses showed significant differences, and the mean ranks of percent porosity showed differences only in the thinnest (2.0 mm) microwave-polymerized specimens (A = 53.55, B = 40.80, and C = 90.70). Thickness did not affect the results for cycle T (I = 96.15, II = 70.20, and III = 82.70), because porosity values were similar in the three thicknesses. Conclusions: Microwave polymerization cycles and the specimen thickness of acrylic resin influenced porosity. Porosity differences were not observed in the polymerized resin bases in the water bath cycle for any thickness. © 2007 by The American College of Prosthodontists.

Influence of storage period and effect of different brands of acrylic resin on the dimensional accuracy of the maxillary denture base

The aim of this study was to evaluate the dimensional changes of denture bases made from different resins after different storage periods. For this purpose, 25 sets of plaster models/resin bases were prepared using 4 acrylic resins submitted to two types of polymerization: 1- QC-20 submitted to polymerization by microwave energy; 2- QC-20 submitted to polymerization by water hot bath; 3- Vipi Cril submitted to polymerization by water hot bath; 4- Vipi Wave submitted to polymerization by microwave energy; and 5- Onda Cryl submitted to polymerization by microwave energy. After polymerization, the specimens were sectioned for accuracy readings using a comparison microscope. Readings were taken at 3 points: the crests of the right (A) and left (B) ridges, and the median region of the palate, in 4 different periods. The data obtained were submitted to two-way ANOVA and Tukey's test at 5% significance level. The greatest distortions were found in the posterior palatal region of the base (M), with statistically significant difference (p<0.05) for the studied resins. All acrylic resins presented dimensional changes and the storage period influenced these alterations.

The influence of the mixing time in the rheological behavior of cement pastes

Rheology has the purpose to study the flux and deformation of materials when submitted to some tension or outer mechanical solicitation. In practice, the effective scientific field broached by rheology is restricted only to the study of homogeneous fluids behavior, in which are included eminent liquids, particles suspensions, and emulsions. The viscosity (η) and the yield stress (τ 0) are the two basic values that define the fluids' behavior. The first one is the proportionality constant that relates the shear rate (γ) with the shear stress (τ) applied, while the second indicates the minimal tension for the flowage beginning. The fluids that obey the Newton's relation - Newtonians fluids - display the constant viscosity and the null yield stress. It's the case of diluted suspensions and grate amount of the pure liquids (water, acetone, alcohol, etc.) in which the viscosity is an intrinsic characteristic that depends on temperature and, in a less significant way, pressure. The suspension, titled Cement Paste, is defined as being a mixture of water and cement with, or without, a superplasticizer additive. The cement paste has a non-Newtonian fluid behavior (pseudoplastic), showing a viscosity that varies in accord to the applied shear stress and significant deformations are obtained from a delimited yield stress. In some cases, systems can also manifest the influence of chemical additives used to modify the interactions fluid/particles, besides the introduced modifications by the presence of incorporated air. To the cement paste the rheometric rehearsals were made using the rheometer R/S Brookfield that controls shear stress and shear rate in accord to the rheological model of Herschel-Bulkley that seems to better adapt to this kind of suspension's behavior. This paper shows the results of rheometrical rehearsals on the cement paste that were produced with cements HOLCIM MC-20 RS and CPV-ARI RS with the addition of superplasticizer additives based of napthaline and polycarboxilate, with and without a constant agitation of the mixture. The obtainment of dosages of superplasticizer additives, as well as the water/cement ratio, at the cement at the fluidify rate determination, was done in a total of 12 different mixtures. It's observed that the rheological parameters seem to vary according to the cement type, the superplasticizer type, and the methodology applied at the fluidity rate determination.

Influence of the environment on behavior patterns of laying hens kept in cages

The aim of this paper is to verify the correlation between environmental indicators and behaviors expressed by laying hens kept in cages. The birds react to a severe environment through their behaviors, end the behaviors can be monitored to identify the birds' welfare conditions. The behaviors birds display ere the result of stress caused by the combination of environmental temperature, relative humidity, radiant heat, and air speed (environmental temperature being the most important). In order to check the influence of the environment, an experiment was carried out on a commercial poultry farm, located in the city of Bastos. The study was initiated in March 2007, during four non-consecutive weeks. The birds' behaviors were recorded using video, by cameras installed in the cages. The birds behaviors were identified and noted for the frequency of occurrence for each bird, and the average duration of each behavior (in seconds), using video samples of 15 minutes recorded from 1 PM to 4 PM. The environmental variables collected were: air temperature, concentration of ammonia, relative air humidity, velocity of the air, noise, roof temperature, and light intensity. The observed behaviors were: opening wings, stretching, threatening, ruffling feathers, drinking water, aggressive pecking, eating, running, lying down, stretching head out of the cage, preening, mounting and prostrating. Principal Components Analysis was used to determine associations between the behavior variables and environmental variables described above. In this experiment, there were no significant correlations between behavioral variables and environmental variables.

Influence of pre-heat treatment and different light-curing units on Vickers hardness of a microhybrid composite resin

The aim of this study was to evaluate the hardness of a dental composite resin submitted to temperature changes before photo-activation with two light-curing unite (LCUs). Five samples (4 mm in diameter and 2 mm in thickness) for each group were made with pre-cure temperatures of 37, 54, and 60°C. The samples were photo-activated with a conventional quartz-tungsten-halogen (QTH) and blue LED LCUs during 40 s. The hardness Vickers test (VHN) was performed on the top and bottom surfaces of the samples. According to the interaction between light-curing unit and different pre-heating temperatures of composite resin, only the light-curing unit provided influences on the mean values of initial Vickers hardness. The light-curing unit based on blue LED showed hardness mean values more homogeneous between the top and bottom surfaces. The hardness mean values were not statistically significant difference for the pre-cure temperature used. According to these results, the pre-heating of the composite resin provide no influence on Vickers hardness mean values, however the blue LED showed a cure more homogeneous than QTH LCU. © 2009 Pleiades Publishing, Ltd.

Influence of storage on chemical properties of different peats

The change of chemical properties during storage of 12 fertilized bagged peats of different origins at high temperature was investigated. The average values for N, soluble salts and EC decreased significantly, whereas the pH as well as P and K contents changed only slightly. Differences in N were observed between the peats. The contents of CAT soluble N in the two dredged frozen black peats did not change during storage. However, a decrease in N was found when water extraction was used. In the case of the 10 white peats the loss of N differed considerably, but it was independent of the method of peat harvest. The N decrease resulted mainly from reduced levels of NO3-N. Substances damaging to plant growth do not seem to have developed during storage as shown by trials on the germination and the growth of Chinese cabbage. There were no significant differences between the peats, whether stored or not.

Influence of bleaching treatment on flexural resistance of hybrid materials.

The aim of this study is to evaluate the flexural resistance of three types of restorative materials: compomer (Freedom), resin-modified glass-ionomer (Vitremer) and composite resin (Esthet-X), observing whether the application of bleaching agent can cause alterations of their flexural properties. Sixty samples were made using a 10 x 1 x 1 mm brass mold, and divided into three groups: G1- Freedom (SDI); G2- Vitremer (3M ESPE); G3- Esthet-X (Dentsply). On half of the samples of each group (10 samples) the bleaching treatment was applied and the other half used as control, was stored in distilled water at a temperature of 37 degrees C. Whiteness HP Maxx bleaching system was applied on the sample surface following the manufacturer's recommendations, simulating the bleaching treatment at the clinic. After this period, a flexural strength (three-point bending) test was conducted using (EMIC DL 1000) machine until the samples fractured. The data were submitted to ANOVA and Tukey tests. Of the restorative materials studied, G3-(87.24 +/- 31.40 MPa) presented the highest flexural strength, followed by G1-(61.67 +/- 21.32 MPa) and G2-(61.67 +/- 21.32 MPa). There was a statistical difference in flexural strength after the bleaching treatment. It was concluded that the use of a beaching agent can promote significant alteration of the flexural strength of these restorative materials.

Influence of the coloring agent concentration on bleaching gel and pulp chamber temperatures during dental bleaching

This study evaluated the Influence of the coloring agent concentration on the temperature of the gel layer and pulp chamber during dental bleaching with an LED/laser light source. Ten human incisors and a digital thermometer with K-type thermocouples were used. Using a high-speed spherical diamond bur, endodontic access was gained through openings on the lingual faces until pulp chamber was exposed. One end of the thermocouple was placed on the labial surface (immersed in bleaching gel) and the other end in the pulp chamber. The same 10 specimens were used in the 12 groups, according to the type and concentration of bleaching gel. Each bleaching gel was used in four different concentrations: manipulated without coloring, with normal quantity recommended by the manufacturer, with double the recommended amount of coloring, and with triple the recommended amount of coloring. The temperature rise was measured every 30 seconds for three minutes with a K-type thermocouple. The data were analyzed by ANOVA to examine the concentration and type of bleaching gel. This test was followed by Tukey's test, which was performed Independently for the gel at the labial surface and the pulp chamber (a = 5%). For both surfaces, values of p = 0.00 were obtained for all factors and for the Interaction between them. The varying concentrations of coloring agent produced statistically significant differences in terms of temperature increase for both the gel layer and the pulp chamber during activation.