Authors:L.F. Barbosa, C.C. Greco and Benedito Denadai
The aim of this study was to analyze the relationship between the slope of the VO2 slow component (VO2sc) and exercise tolerance (tlim) during constant-work-rate (CWR) exercise performed within the severe intensity domain. Fifteen active subjects (VO2max = 41.2 ± 5.1 ml.kg−1.min−1) performed the following tests: 1) an incremental test to determine the VO2max and the work rate associated with the VO2max (IVO2max) and; 2) two CWR transitions at 95% of the IVO2max to determine the slope of the VO2 slow component and the tlim. Three tlims were obtained: tlim1 = CWR1; tlim2 = CWR2; and tlim1+2 = (CWR1 + CWR2) / 2. There was no significant difference between the VO2max (3271.7 ± 410.7 mL·min−1) and VO2peak obtained during the CWR tests (CWR1 = 3356.3 ± 448.8 mL·min−1, CWR2 = 3362.2 ± 393.4 mL·min−1, p > 0.05). Significant correlations (p < 0.05) were found among the VO2sc kinetics and tlim1 (r = −0.53), tlim2 (r = −0.49) and tlim1+2 (r = −0.55). Thus, exercise tolerance during CWR performed within the severe intensity domain is partially explained by the slope of the VO2 slow component.
Authors:G. F. Barbosa, F. L. A. Machado, A. R. Rodrigues and W. M. Azevedo
Magnetic thermogravimetric analysis (TGM) was used to investigate the influence of the milling time (tmill) in the Curie temperature (TC) of nanocrystalline powders and of a melt-spun amorphous ribbon with composition Fe56Co7Ni7Zr10B20. The TGM analysis was carried in a continuous flow of 99.99% pure argon from room temperature up to 1250 K. A magnetic field of 100 Oe was applied throughout the measurements. Nanopowders of Fe56Co7Ni7Zr10B20 were produced by mechanical alloying the samples in an argon atmosphere for milling times ranging from 1 to 100 h. The samples were characterized by X-ray diffraction and by scanning electron microscopy. The average particle size decreased from 45.4 nm for a powder milled for 1 h to 5 nm after being milled for 100 h. Moreover, TC (=1126.4 ± 4.4 K) was found to be nearly independent of tmill while for the melt-spun amorphous ribbon it was found to be substantially smaller (TC = 482 K). This is a clear indication that TC is quite sensitive to the degree of amorphosity present in the sample. The activation energy associated to the crystallization process was estimated from DSC data by using the Kissinger's method to be 193 kJ/mol.
Authors:Marcela N. Barbosa, Antonio S. Araujo, Luzia P. F. C. Galvão, Edjane F. B. Silva, Anne G. D. Santos, Geraldo E. Luz Jr. and Valter J. Fernandes Jr.
The capture of carbon dioxide was carried out using MCM-41 and SBA-15 as adsorbents. These mesoporous materials were synthesized by the hydrothermal method, and subsequently functionalized with the di-iso-propylamine (DIPA). Then, they were characterized by XRD, BET, and TG/DTG. The X-ray diffraction patterns of the synthesized samples showed the characteristic peaks of MCM-41 and SBA-15, indicating that the structures of these materials were obtained. The functionalized samples presented a decrease of the intensities of these peaks, suggesting a decreasing in the structural organization of the material; however, the mesoporous structure was preserved. For the adsorption capacity measurements, the materials were previously saturated with carbon dioxide at 75 °C, and then desorbed in a thermobalance in the temperature range of 25–900 °C, under helium atmosphere. Desorption tests showed that the functionalized MCM-41 presented a weight loss of 7.5 wt%, against 5.9 wt% for SBA-15. The obtained values indicate that these nanostructured materials can be used as adsorbent for carbon dioxide capture.
Authors:Carla Sayago, Vanessa Camargo, F. Barbosa, Cláudia Gularte, Geovana Pereira, Silvia Miotto, V. Cechinel Filho, R. Luiz Puntel, V. Folmer and A. Mendez
Bauhinia species are known to have hypoglycemiant and antioxidant activities. Here, hydro-ethanolic leaf extracts from Bauhinia forficata subsp. pruinosa and Bauhinia variegata, collected in a Pampa biome region of Brazil, were investigated to characterize their chromatographic profile, flavonoid content and in vitro antioxidant activity (TBARS and DPH assays). The extracts were obtained from dried and fresh leaves. The total flavonoid content was assessed by spectrophotometric determination, and the results ranged between 572.08 and 1,102.99 μg mL−1. Moreover, flavonoids were more predominant in B. variegata than in B. forficata subsp. pruinosa. HPLC analysis detected a complex profile of phenolic compounds, being the flavonoid kaempferitrin founded B. forficata subsp. pruinosa; in addition, other kaempferol and quercetin derivatives were present. In vitro antioxidant assays demonstrated a different behavior depending on the species, leaf treatment and extract concentration. In general, B. variegata extracts obtained from fresh material presented higher antioxidant potential, which can be attributed to the predominance of flavonoids in their chemical composition.
Authors:Alex M. Nasaré, Roberto C. Tedesco, Priscila C. Cristovam, Marcos A. Cenedese, Andrés J. Galisteo Jr., Heitor F. Andrade Jr., José Álvaro P. Gomes, Érik V. Guimarães, Helene S. Barbosa and Luis G. Alonso
HSP90B1 is a gene that codifies heat shock protein 108 (HSP108) that belongs to a group of proteins induced under stress situation, and it has close relation with the nervous system, especially in the retina. Toxoplasma gondii causes ocular toxoplasmosis that has been associated with a late manifestation of the congenital toxoplasmosis although experimental models show that morphological alterations are already present during embryological development. Here, we used 18 eyes of Gallus domesticus embryos in 7th and 20th embryonic days to establish a model of congenital ocular toxoplasmosis, experimentally infected in its fifth day correlating with HSP90B1 gene expression. Embryos’ eyes were histologically evaluated, and gene expression was performed by real-time polymerase chain reaction (PCR). Our data showed parasite present in the choroid, unusual migration of retinal pigment epithelium, and chorioretinal scars, and a tendency to a lower expression of the HSP90B1 gene upon experimental infection. This is a promising model to better understand T. gondii etiopathogeny.