Effects of gender on stroke rates, critical speed and velocity of a 30-min swim in young swimmers

Our objective was to analyze the effect of gender on the relationship between stroke rates corresponding to critical speed (SRCS) and maximal speed of 30 min (SRS30) in young swimmers. Twenty two males (GM1) (Age = 15.4 ± 2.1 yr., Body mass = 63.7 ± 12.9 kg, Stature = 1.73 ± 0.09 m) and fourteen female (GF) swimmers (Age = 15.1 ± 1.6 yr., Body mass = 58.3 ± 8.8 kg, Stature = 1.65 ± 0.06 m) were studied. A subset of males (GM2) was matched to the GF by their velocity for a 30 min swim (S30). The critical speed (CS) was determined through the slope of the linear regression line between the distances (200 and 400 m) and participant's respective times. CS was significantly higher than S30 in males (GM1 - 1.25 and 1.16 and GM2 - 1.21 and 1.12 m·s-1) and females (GF - 1.15 and 1.11 m·s-1). There was no significant difference between SRCS and SRS30 in males (GM1 - 34.16 and 32.32 and GM2 - 34.67 and 32.46 cycle·s-1, respectively) and females (GF - 34.18 and 33.67 cycle·s-1-1, respectively). There was a significant correlation between CS and S30 (GM1 - r = 0.89, GF - r = 0.94 and GM2 - r = 0.90) and between SRCS and SRS30 (GM1 - r = 0.89, GF - r = 0.80 and GM2 - r = 0.88). Thus, the relationship between SRCS and SRS30 is not influenced by gender, in swimmers with similar and different aerobic capacity levels. ©Journal of Sports Science and Medicine (2007).

The influence of residual salivary fluoride from dentifrice on enamel erosion: An in situ study

The objective of this study was to assess the salivary residual effect of fluoride dentifrice on human enamel subjected to an erosive challenge. This crossover in situ study was performed in two phases (A and B), involving ten volunteers. In each phase, they wore acrylic palatal appliances, each containing 3 human enamel blocks, during 7 days. The blocks were subjected to erosion by immersion of the appliances in a cola drink for 5 minutes, 4 times a day. Dentifrice was used to brush the volunteers' teeth, 4 times a day, during 1 minute, before the appliance was replaced into the mouth. In phases A and B the dentifrices used had the same formulation, except for the absence (PD) or presence (FD) of fluoride, respectively. Enamel alterations were determined using profilometry, microhardness (%SMHC), acid- and alkali-soluble F analysis. The data were tested using ANOVA (p < 0.05). The concentrations (mean ± SD) of alkali- and acid-soluble F (μgF/cm 2) were, respectively, PD: 1.27 a ± 0.70/2.24∧ A ± 0.36 and FD: 1.49 a ± 0.44/2.24∧ ± 0.67 (p > 0.05). The mean wear values (± SD, μm) were PD: 3.63 a ± 1.54 and FD: 3.54 a ± 0.90 (p > 0.05). The mean %SMHC values (± SD) were PD: 89.63 a ± 4.73 and FD: 87.28 a ± 4.01 (p > 0.05). Thus, we concluded that the residual fluoride from the fluoride-containing dentifrice did not protect enamel against erosion.

Effect of light-curing method and indirect veneering materials on the Knoop hardness of a resin cement

This study evaluated the Knoop hardness of a dual-cured resin cement (Rely-X ARC) activated solely by chemical reaction (control group) or by chemical / physical mode, light-cured through a 1.5 mm thick ceramic (HeraCeram) or composite (Artglass) disc. Light curing was carried out using conventional halogen light (XL2500) for 40 s (QTH); light emitting diodes (Ultrablue Is) for 40 s (LED); and Xenon plasma arc (Apollo 95E) for 3 s (PAC). Bovine incisors had their buccal face flattened and hybridized. On this surface a rubber mold (5 mm in diameter and 1 mm in height) was bulk filled with the resin cement. A polyester strip was seated for direct light curing or through the discs of veneering materials. After dry storage in the dark (24 h 37°C), the samples (n = 5) were sectioned for hardness (KHN) measurements, taken in a microhardness tester (50 gF load 15 s). The data were statistically analyzed by ANOVA and Tukey's test (α = 0.05). The cement presented higher Knoop hardness values with Artglass for QTH and LED, compared to HeraCeram. The control group and the PAC/Artglass group showed lower hardness values compared to the groups light-cured with QTH and LED. PAC/HeraCeram resulted in the worst combination for cement hardness values. © 2009 Sociedade Brasileira de Pesquisa Odontológica.

Evaluation of some properties of fermented milk beverages that affect the demineralization of dental enamel

The aim of this in vitro study was to evaluate the erosive capacity of fermented milk beverages, as well as some of their properties that affect the demineralization of dental enamel (pH, buffering capacity, fluoride, calcium and phosphorus contents). Three different batches of 6 commercial brands of fermented milk beverages were analyzed. pH evaluation was accomplished using a potentiometer. The buffering capacity was measured by adding 1 mol L -1 NaOH. Fluoride concentration was assessed by an ion specific electrode after hexamethyldisiloxane-facilitated diffusion, and calcium and phosphorus concentrations were assessed by a colorimetric test using a spectrophotometer. Sixty specimens of bovine enamel were randomly assigned to 6 groups (n = 10). They were exposed to 4 cycles of demineralization in the fermented milk and remineralization in artificial saliva. Enamel mineral loss was determined by surface microhardness (%SMHC) and profilometric tests. The samples' pH ranged from 3.51 to 3.87; the buffering capacity ranged from 470.8 to 804.2 μl of 1 mol L -1 NaOH; the fluoride concentration ranged from 0.027 to 0.958 μgF/g; the calcium concentration ranged from 0.4788 to 0.8175 mgCa/g; and the phosphorus concentration ranged from 0.2662 to 0.5043 mgP/g. The %SMHC ranged from-41.0 to -29.4. The enamel wear ranged from 0.15 μm to 0.18 μm. In this in vitro study, the fermented milk beverages did not promote erosion of the dental enamel, but rather only a superficial mineral loss.

Fluoride concentration of some brands of fermented milks available in the market

Objectives: To evaluate the fluoride ion concentration in some fermented milks present in the market. Methods: Three brands of 6 fermented milks (Parmalat®-uva, Chamyto®, Paulista®, Batavito®, Yakult®, Vigor Club®) were analyzed. Fluoride concentration was evaluated after facilitated microdiffusion by HDMS. Results: Parmalat® products ranged from 0.022 μgF/g to 0.031 μgF/g, Chamyto® from 0.228 μgF/g to 0.272 μgF/g, Paulista® from 0.182 μgF/g to 0.220 μgF/g, Batavito® from 0.028 μgF/g to 0.030 μgF/g, Yakult® from 0.115 μgF/g to 0.206 μgF/g and Vigor Club® from 0.808 μgF/g to 1.171 μgF/g. Conclusions: The presence of fluoride could be observed in all of the fermented milks analyzed which can contribute with the total fluoride daily intake.

Fluxo de potência trifásico probabilístico para redes de distribuição usando o método de estimação por pontos

In this paper the point estimation method is applied to solve the probabilistic power flow problem for unbalanced three-phase distribution systems. Through the implementation of this method the probability distribution functions of voltages (magnitude and angle) as well as the active and reactive power flows in the branches of the distribution system are determined. Two different approaches of the point estimation method are presented (2m and 2m+1 point schemes). In order to test the proposed methodology, the IEEE 34 and 123 bus test systems are used. The results obtained with both schemes are compared with the ones obtained by a Monte Carlo Simulation (MCS).

Spermatogenesis of riffle bugs, Rhagovelia whitei and Rhagovelia sp (Veliidae), and backswimmers Martarega sp (Notonectidae).

We examined the course of spermatogenesis and the meiotic chromosome complements in aquatic species of true bugs, Heteroptera. The chromosome complement of the Veliidae species was 2n = 39 (38A + X0) and 23 (22A + X0) in Rhagovelia whitei and Rhagovelia sp, respectively, and in the species of the Notonectidae (Martarega sp) it was 26 (22A + 2m + XY); all collected from the region of São José do Rio Preto, SP, Brazil. An impressive characteristic of the first analysis was the size of the cells belonging to Martarega sp, which were six times larger than the same cells in Pentatomidae and twice as large as the cells in aquatic Heteroptera (Gerridae). Regarding spermatogenesis, all the species analyzed showed the same pattern: holocentric chromosomes and elongated spermatids with the chromatin distributed evenly along the head. The family Veliidae showed several bodies impregnated with silver nitrate at prophase, while the family Notonectidae displayed only one. The cells of Notonectidae also showed an evident and round body until the end of prophase I and in the family Veliidae the silver-impregnated bodies were disorganized, where the only region visualized was possibly that of the NOR. In metaphase, silver-stained regions were found at the periphery of all chromosomes in Veliidae and at the periphery of some chromosomes in Notonectidae. The spermatids of Veliidae showed a less silver-impregnated vesicle, while Notonectidae showed silver staining only in part of the nuclear membrane. Therefore, families of Heteroptera have some differences and features that can help identify and classify these species.

Above- and below-ground biomass and carbon dynamics in Brazilian Cerrado wet grasslands

Questions: Grasslands are usually neglected as potential carbon stocks, partially due to the lack of studies on biomass and carbon dynamics in tropical grasslands. What is the importance of Brazilian tropical wet grasslands as carbon sinks? Does fire frequency and season affect biomass and carbon allocation in Brazilian wet grasslands? Location: Wet grasslands, tropical savanna, Jalapão, Tocantins, northern Brazil. Methods: We determined biomass above- and below-ground, estimated carbon stocks in biennially burned plots (B2) and plots excluded from fire for 4 yr (B4). Moreover, we determined biomass in both rainy and dry seasons. Samples were 0.25 m × 0.25 m × 0.2 m (eight samples per treatment, applying a nested design, total of 48 samples). The biomass was classified in above-ground graminoids, forbs and dead matter, and below-ground roots and other below-ground organs. We used ANOVA to compare variables between treatments and seasons. Results: More than 40% of the total biomass and carbon stocks were located below-ground, mostly in roots. A high proportion of dead biomass (B4) was found in the above-ground material, probably due to low decomposition rates and consequent accumulation over the years. Although these grasslands do not experience water stress, we found significant evidence of resource re-allocation from below-ground organs to the above-ground biomass in the rainy season. Conclusions: We found more dead biomass in the rainy season, probably due to low decomposition rates, which can increase fire risk in these grasslands during the following dry season. These tropical wet grasslands stored high amounts of carbon (621 to 716 g C.m-2), mostly in the roots. Thus, policymakers should consider tropical grasslands as potential carbon stocks, since they are one of the most threatened and unprotected ecosystems in Brazil. © 2012 International Association for Vegetation Science.

Evaluation of degree of conversion and hardness of dental composites photoactivated with different light guide tips

Objective: The aim of this study was to evaluate the degree of conversion and hardness of different composite resins, photo-activated for 40 s with two different light guide tips, fiber optic and polymer. Methods: Five specimens were made for each group evaluated. The percentage of unreacted carbon double bonds (% C=C) was determined from the ratio of absorbance intensities of aliphatic C=C (peak at 1637 cm-1) against internal standard before and after curing of the specimen: aromatic C-C (peak at 1610 cm-1. The Vickers hardness measurements were performed in a universal testing machine. A 50 gf load was used and the indenter with a dwell time of 30 seconds. The degree of conversion and hardness mean values were analyzed separately by ANOVA and Tukey's test, with a significance level set at 5%. Results: The mean values of degree of conversion for the polymer and fiber optic light guide tip were statistically different (P<.001). The hardness mean values were statistically different among the light guide tips (P<.001), but also there was difference between top and bottom surfaces (P<.001). Conclusions: The results showed that the resins photo-activated with the fiber optic light guide tip promoted higher values for degree of conversion and hardness.

Grip and load force coordination in cyclical isometric manipulation task is not affected by the feedback type

Background: The relationship between normal and tangential force components (grip force - GF and load force - LF, respectively) acting on the digits-object interface during object manipulation reveals neural mechanisms involved in movement control. Here, we examined whether the feedback type provided to the participants during exertion of LF would influence GF-LF coordination and task performance. Methods. Sixteen young (24.7 ±3.8 years-old) volunteers isometrically exerted continuously sinusoidal FZ (vertical component of LF) by pulling a fixed instrumented handle up and relaxing under two feedback conditions: targeting and tracking. In targeting condition, FZ exertion range was determined by horizontal lines representing the upper (10 N) and lower (1 N) targets, with frequency (0.77 or 1.53 Hz) dictated by a metronome. In tracking condition, a sinusoidal template set at similar frequencies and range was presented and should be superposed by the participants' exerted FZ. Task performance was assessed by absolute errors at peaks (AEPeak) and valleys (AEValley) and GF-LF coordination by GF-LF ratios, maximum cross-correlation coefficients (r max), and time lags. Results: The results revealed no effect of feedback and no feedback by frequency interaction on any variable. AE Peak and GF-LF ratio were higher and rmax lower at 1.53 Hz than at 0.77 Hz. Conclusion: These findings indicate that the type of feedback does not influence task performance and GF-LF coordination. Therefore, we recommend the use of tracking tasks when assessing GF-LF coordination during isometric LF exertion in externally fixed instrumented handles because they are easier to understand and provide additional indices (e.g., RMSE) of voluntary force control. © 2013 Pedão et al.; licensee BioMed Central Ltd.

Recovery of pulmonary structure and exercise capacity by treatment with granulocyte-colony stimulating factor (G-CSF) in a mouse model of emphysema

Emphysema is a chronic obstructive pulmonary disease characterized abnormal dilatation of alveolar spaces, which impairs alveolar gas exchange, compromising the physical capacity of a patient due to airflow limitations. Here we tested the effects of G-CSF administration in pulmonary tissue and exercise capacity in emphysematous mice. C57Bl/6 female mice were treated with elastase intratracheally to induce emphysema. Their exercise capacities were evaluated in a treadmill. Lung histological sections were prepared to evaluate mean linear intercept measurement. Emphysematous mice were treated with G-CSF (3 cycles of 200 μg/kg/day for 5 consecutive days, with 7-day intervals) or saline and submitted to a third evaluation 8 weeks after treatment. Values of run distance and linear intercept measurement were expressed as mean ± SD and compared applying a paired t-test. Effects of treatment on these parameters were analyzed applying a Repeated Measures ANOVA, followed by Tukey's post hoc analysis. p < 0.05 was considered statistically significant. Twenty eight days later, animals ran significantly less in a treadmill compared to normal mice (549.7 ± 181.2 m and 821.7 ± 131.3 m, respectively; p < 0.01). Treatment with G-CSF significantly increased the exercise capacity of emphysematous mice (719.6 ± 200.5 m), whereas saline treatment had no effect on distance run (595.8 ± 178.5 m). The PCR cytokines genes analysis did not detect difference between experimental groups. Morphometric analyses in the lung showed that saline-treated mice had a mean linear intercept significantly higher (p < 0.01) when compared to mice treated with G-CSF, which did not significantly differ from that of normal mice. Treatment with G-CSF promoted the recovery of exercise capacity and regeneration of alveolar structural alterations in emphysematous mice. © 2013.

Effect of low fluoride acidic dentifrices on dental remineralization

This study evaluated the capacity of fluoride acidic dentifrices (pH 4.5) to promote enamel remineralization using a pH cycling model, comparing them with a standard dentifrice (1,100 μgF/g). Enamel blocks had their surface polished and surface hardness determined (SH). Next, they were submitted to subsurface enamel demineralization and to postdemineralization surface hardness analysis. The blocks were divided into 6 experimental groups (n=10): placebo (without F, pH 4.5, negative control), 275, 412, 550, 1,100 μgF/g and a standard dentifrice (positive control). The blocks were submitted to pH cycling for 6 days and treatment with dentifrice slurries twice a day. After pH cycling, surface and crosssectional hardness were assessed to obtain the percentage of surface hardness recovery (%SHR) and the integrated loss of subsurface hardness (δKHN). The results showed that %SHR was similar among acidic dentifrices with 412, 550, 1,100 μgF/g and to the positive control (Tukey's test; p>0.05). For ΔKHN, the acidic dentifrice with 550 μg F/g showed a better performance when compared with the positive control. It can be concluded that acidic dentifrice 550 μgF/g had similar remineralization capacity to that of positive control.

Commutative group codes in R4, R6, R8 and R16-Approaching the bound

Spherical codes in even dimensions n = 2m generated by a commutative group of orthogonal matrices can be determined by a quotient of m-dimensional lattices when the sublattice has an orthogonal basis. We discuss here the existence of orthogonal sublattices of the lattices A2, D3, D4 and E8, which have the best packing density in their dimensions, in order to generate families of commutative group codes approaching the bound presented in Siqueira and Costa (2008) [14]. © 2013 Elsevier B.V. All rights reserved.

Cover crops and no-till effects on physical fractions of soil organic matter

Physical fractions (free light fraction, intra-aggregate light fraction and heavy fraction) of soil organic matter (SOM) are good indicators of soil quality for sustainable land use. The objective of this study was to evaluate the effect of cover crops on total organic carbon (TOC) and physical fractions of soil organic matter in soil under a no-tillage system (NTS) and a conventional tillage system (CTS, one plowing and two disking). A three-year field experiment was carried out as a cover crop-rice (Oryza sativa)-cover crop-rice rotation. Treatments included cover crops (Panicum maximum, Brachiaria ruziziensis, Brachiaria brizantha, and pearl millet (Pennisetum glaucum), fallow, till or no till. The SOM was physically fractionated in free light fraction (FLF), intra-aggregates light fraction (IALF) and heavy fraction (HF). The levels of C in whole soil were also evaluated, as well as C in the light fractions (FLF+IALF) and in the HF. Results indicated that concentrations of C in the FLF and IALF in surface soils (0-0.05m) were much higher (10.8 and 1.95gkg-1, respectively) than that in the 0.05-0.1m soil depth (7.68 and 1.54gkg-1, respectively) and in the 0.1-0.2m soil depth (4.98 and 1.24gkg-1, respectively). The NTS resulted in higher levels of FLF (12.2gkg-1) and IALF (2.19gkg-1) than with CTS (1.37-7.30gkg-1). Millet had the highest C (19.5gkg-1) and N (1.1gkg-1) concentrations in soil. There was an accumulation of TOC and total N in the surface soil with cover crops, and concentrations of TOC were higher in the HF (79.0%) than in the light fractions (21.0%). Although SOM changed little during the two years of this experiment, the various C fractions were significantly affected by the tillage treatments. We conclude that SOM physical fractionation allowed seeing significant differences caused by the soil management in the organic matter dynamics in a short period of time. © 2013 Elsevier B.V.

Influence of densities on the growth of brown mussel Perna perna L. cultivated in suspended socks at Caraguatatuba, southeastern Brazil

This study was carried out in a marine area at Cocanha Beach, Caraguatatuba, southeastern Brazil, aiming to determine the most appropriated density for brown mussel (Perna perna L.) cultured in suspended socks (French System), in order to reduce costs with acquisition of juvenile mussels (seed) and labor. In September 2007, 15 socks measuring 2 m each were reared at densities of 300, 400 and 500 seeds/m. After 250 days, mussels were harvested and separated in two length classes: non-commercial (<6 cm) and commercial (≥6 cm). Mussels were counted and weighed. In August 2008, the experiment was repeated with 1-m-long socks at lower densities (200, 250 and 300 seeds/m) in order to identify differences among commercial-sized mussels only. Data were analyzed by ANOVA or nonparametric Kruskal-Wallis test, followed by Tukey or SNK tests, respectively. The results suggest that it is feasible to use densities from 250 to 300 seeds/m, since biomass yields are similar to those registered at higher densities and the use of mussel seed is therefore optimized. © 2013 Springer Science+Business Media Dordrecht.