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- Author or Editor: L. S. Santos x
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Abstract
In the present study we analyzed the Brazilian scientific production in the area of science education. The study was structured on: data by research groups registered in Conselho Nacional de Desenvolvimento Científico e Tecnológico; analysis of the post-graduate strictu sensu programs; analysis of theses and dissertations linked to post-graduate programs; and papers in international databases. Our research was conducted strictly via world wide web, from December 2009 to September 2010. It was found that both number of research groups, researchers, post-graduate programs, thesis, dissertations and papers presented a marked increase, especially in the last decade (from 2000 onwards). The major research centers were found to be located in public universities from Brazilian southeast and south regions. However, it was observed a tendency of decentralization, due to a recent investment in new public universities in the other Brazilian regions. So, this study sought to present an overview of the scientific production about science education and we expect that this information can help to expand the vision about the development of this research area in Brazil.
The objective of the present study was to compare differences between elderly rats and young obesity-induced rats in their activity/inactivity circadian rhythm. The investigation was motivated by the differences reported previously for the circadian rhythms of both obese and elderly humans (and other animals), and those of healthy, young or mature individuals. Three groups of rats were formed: a young control group which was fed a standard chow for rodents; a young obesity-induced group which was fed a high-fat diet for four months; and an elderly control group with rats aged 2.5 years that was fed a standard chow for rodents. Activity/inactivity data were registered through actimetry using infrared actimeter systems in each cage to detect activity. Data were logged on a computer and chronobiological analysis were performed. The results showed diurnal activity (sleep time), nocturnal activity (awake time), amplitude, acrophase, and interdaily stability to be similar between the young obesity-induced group and the elderly control group, but different in the young control group. We have concluded that obesity leads to a chronodisruption status in the body similar to the circadian rhythm degradation observed in the elderly.
Abstract
The use of biodegradable natural polymers has increased due to the over-solid packaging waste. In this study, a chemical modification of the casein molecule was performed by Maillard reaction, and the modified polymer was evaluated by polyacrylamide gel electrophoresis (PAGE), thermogravimetry/derivative thermogravimetry (TG/DTG), FT-IR, and 1H-NMR spectroscopy. Subsequently, films based on the modified casein were obtained and characterized by mechanical analysis, water vapor transmission, and erosion behavior. The PAGE results suggested an increase of molecular mass of the modified polymer, and FT-IR spectroscopy data indicated inclusion of C–OH groups into this molecule. The TG/DTG curves of modified casein presented a different thermal decomposition profile compared to the individual compounds. Mechanical tests showed that the chemical modification of the casein molecules provided higher elongation rates (45.5%) to the films, suggesting higher plasticity, than the original molecules (13.4%). The modified casein films presented higher permeability (0.505 ± 0.006 μg/h mm3) than the original polymer (0.387 ± 0.006 μg/h mm3) films at 90% relative humidity (RH). In pH 1.2, modified casein films presented higher erosion rates (32.690 ± 0.692%) than casein films (19.910 ± 2.083%) after 8 h, suggesting an increased sensibility for erosion of the modified casein films in acid environment. In water (pH 7.0), the films erosion profiles were similar. Those findings indicate that the modification of molecule by Maillard reaction provided films more plastic, hydrophilic, and sensitive to erosion in acid environment, suggesting that a new polymer with changed properties was founded.
Abstract
Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by base-catalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME.
Abstract
Physicochemical and thermal analyses were undertaken to evaluate the influence of the temperature on the oxidation of sea fish oil once its polyunsaturated fatty acids deteriorate rapidly. Fish oil displayed four decomposition steps in synthetic air atmosphere and only one step in nitrogen atmosphere. The first step started at 189 and 222 °C for oxidizing and inert atmospheres, respectively. An OIT value of 53 min was measured at 100 °C. After the degradation process the peroxide index and the iodine index reduced from 35.38 to 9.85 meq × 1000 g−1 and from 139.79 to 120.19 gI2 × 100 g−1, respectively. An increase of the free fatty acids amount from 0.07 to 0.17% was observed while viscosity increased from 57.2 to 58.0 cP. Absorption at 272 nm also increased. The thermogravimetric and spectroscopic techniques are reproducible and versatile being an option for characterization of edible oil oxidation.
Abstract
Copper monoxide (CuO) was successfully obtained by microwave-assisted hydrothermal method, using different conditions—in a solution without base, in a solution alkalinized with NaOH or with NH4OH. The powders were analyzed by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, UV–Visible spectroscopy, and scanning electronic microscopy. XRD results showed that CuO was obtained with monoclinic structure and without secondary phases. Thermal analysis and infrared spectra indicated the presence of acetate groups on the powder surface. TG curves also showed a mass gain assigned to the Cu(I) oxidation indicating that a reduction possibly occurred during synthesis. The high and broad absorption band in the UV–Vis spectroscopy from 250 to 750 nm indicated the coexistence of Cu(II) and Cu(I), confirming the Cu(II) reduction, inside the CuO lattice. It was also possible to confirm the Cu(II) reduction by a displacement of the Me–O vibration bands observed in the IR spectra at around 500 cm−1.
Abstract
The poultry fat methylic (BMF) and ethylic (BEF) biodiesels were synthesized through transesterification by homogeneous basic catalysis. The chromatographic analyses showed the palmitic, stearic, oleic, and linoleic esters as majority components. Owing to its considerable amount of polyunsaturated fat acids, poultry fat usually leads to a biodiesel with low oxidative stability. In this study, the oxidation of their ethylic and methylic biodiesels was evaluated by Rancimat, PDSC, and PetroOxy. The OSI (Rancimat) was of 0.47 and 0.40 h for the ethylic and methylic biodiesel, respectively. In PDSC, both fuels presented an OT of about 120–123 °C. PetroOxy analysis indicated an OxyStab of 11 min for BEF and higher than 11 min for BMF. There was no correspondence among the oxidative stabilities of the employed techniques [OT(BEF) ≈ OT(BMF), OSI(BEF) > OSI(BMF), and OxyStab(BEF) < OxyStab(BMF)]. The discussion of these results was based on the indicator measured by each technique: enthalpic events are observed by PDSC; conductivity of volatile secondary oxidation products is measured by Rancimat; reduction of the oxygen pressure is determined by PetroOxy. This discussion showed that these different indicators do not reflect the same stage of the oxidative process as energy is release at the beginning of the propagation step, oxygen pressure decreases during the propagation step, and oxidation products are formed during the termination step.
The study was aimed to investigate the reproducibility of performance parameters obtained from 10-s maximal cycling effort against different braking forces in young adult athletes. The sample (n = 48) included male athletes aged 18.9–29.9 years (175.5 ± 6.9 cm, 76.2 ± 10.1 kg). The exercise protocol was performed in a cycle-ergometer against a random braking force (4% to 11% of body mass). Intra-individual variation was examined from repeated tests within one week. Descriptive statistics were computed and differences between sessions were tested using paired t-test. The coefficient of correlation between repeated measures, technical error of measurement (TEM), coefficient of variation and ICC were calculated. Agreement between trials was examined using the Bland-Altman procedure. Mean values of peak power were relatively stable when obtained from sampling rates of 50 Hz and ranged between 1068 watt and 1082 watt (t(47) = 1.149, p = 0.256, ES-r = 0.165) or while corresponding to a sampling rate of 1 Hz (t(47) = 0.742, p = 0.462, ES-r = 0.107). Correlations between repeated measures were high (+0.907, 95% CI: +0.839 to +0.947) and TEM about 59.3 watt (%CV = 5.52%; ICC = 0.951, 95% CI: 0.912 to 0.972). The present study suggests that reproducibility of peak power in male adult athletes tended to be acceptable and within individual error appeared unrelated to braking force.
