Factors that influence the occurrence and dispersion of iron minerals in sandy sediments of terraces and floodplains of rivers draining the Quadrilatero Ferrifero (MG).

Este trabalho apresenta os resultados de estudos sedimentol?gicos realizados ao longo dos cursos de ?gua das bacias hidrogr?ficas dos rios Piracicaba, das Velhas e Doce que drenam as ?reas das minas de ferro do Quadril?tero Ferr?fero. Foram realizadas caracteriza??es sedimentol?gicas e mineral?gicas de amostras coletadas na calha dos cursos de ?gua visando obter a concentra??o de minerais de ferro. Paralelamente, foram analisadas amostras de sedimentos coletados nas v?rzeas e terra?os, com objetivo de obter elementos de compara??o temporal da ocorr?ncia de minerais de ferro em sedimentos aluviais depositados anteriormente ? instala??o das minas na regi?o. Os resultados obtidos indicam que a presen?a de barramentos nos cursos de ?gua interfere na dispers?o dos minerais de ferro. A malha ferrovi?ria utilizada como escoamento da produ??o de ferro ao longo do rio Piracicaba atua como fonte secund?ria de minerais de ferro nas v?rzeas e na calha do rio. Quando comparados ? concentra??o de minerais de ferro nos terra?os, os sedimentos das calhas fluviais mostram substancial aumento da concentra??o, indicando que a a??o antr?pica ? a causadora deste aumento a despeito das a??es mitigadoras que a legisla??o ambiental preconiza.This work presents the results of sedimentological studies conducted along the watercourses of the Piracicaba, Velhas and Doce river basins that drain the iron mining areas of the Quadrilatero Ferr?fero. Sedimentological and mineralogical characterization of sandy sediment samples collected in the channel of the water courses was carried out in order to obtain the concentration of iron minerals. In addition, samples of sediments from the floodplains and terraces were collected and analyzed, with the pourpose of make temporal comparison among sandy iron mineral concentration in alluvial sediments deposited prior to the installation of the mines in the region. The results indicate that the presence of dams in the watercourses interferes with the dispersion of iron minerals. The railroad used in transport of the iron production along the Piracicaba river valley acts as a secondary source of iron minerals in the floodplains and in the river channel. When compared to the concentration of iron minerals in the terraces, the sediments of the river channels show a substantial increase in concentration, indicating that the anthropic action is the main cause of this increase despite mitigating actions regulated by environmental laws

Effects of post-exercise cooling on heart rate recovery in normotensive and hypertensive men

Background: Post-exercise heart rate recovery (HRR) is determined by cardiac autonomic restoration after exercise and is reduced in hypertension. Post-exercise cooling accelerates HRR in healthy subjects, but its effects in a population with cardiac autonomic dysfunction, such as hypertensives (HT), may be blunted. This study assessed and compared the effects of post-exercise cooling on HRR and cardiac autonomic regulation in HT and normotensive (NT) subjects. Methods: Twenty-three never-treated HT (43±8 ys) and 25 NT (45±8 ys) men randomly underwent two exercise sessions (30 min of cycling at 70%VO2peak) followed by 15 min of recovery. In one randomly allocated session, a fan was turned on in front of the subject during the recovery (cooling), while in the other session, no cooling was performed (control). HRR was assessed by heart rate reductions after 60 (HRR60s) and 300s (HRR300s) of recovery, short-term time constant of HRR (T30), and the time constant of the HRR after exponential fitting (HRRτ). HRV was assessed using time- and frequency-domain indices. Results: HRR and HRV responses in the cooling and control sessions were similar between the HT and NT. Thus, in both groups, post-exercise cooling equally accelerated HRR (HRR300s = 39±12 vs. 36±10 bpm, p≤0.05) and increased post44 exercise HRV (lnRMSSD = 1.8±0.7 vs. 1.6±0.7 ms, p≤0.05). Conclusion: Differently from the hypothesis, post-exercise cooling produced similar improvements in HRR in HT and NT men, likely by an acceleration of cardiac parasympathetic reactivation and sympathetic withdrawal. These results suggest that post-exercise cooling equally accelerates HRR in hypertensive and normotensive subjects

Experience of sexual coercion and risky sexual behavior among Ugandan university students

<p>Abstract</p> <p>Background</p> <p>Growing worldwide evidence shows that the experience of sexual coercion is fairly prevalent among young people and is associated with risky sexual behavior thereafter. The causal mechanisms behind this are unclear but may be dependent on specific contextual determinants. Little is known about factors that could buffer the negative effects of coercion. The aim of this study was to assess the association between the experience of sexual coercion and risky sexual behavior among university students of both sexes in Uganda.</p> <p>Methods</p> <p>In 2005, 980 (80%) out of a total of 1,220 students enrolled in Mbarara University of Science and Technology in Uganda participated in a self-administered questionnaire covering socio-demographic and religious factors, social capital, mental health, alcohol use, and sexual behavior. A validated scale of six items was used to assess the experience of sexual coercion. Logistic regression analyses were applied to control for confounders. Potential buffering factors were analyzed by testing for effect modification.</p> <p>Results</p> <p>Fifty-nine percent of those who responded had previously had sexual intercourse. Among the male students 29.0%, and among the female students 33.1% reported having had some experience of sexual coercion. After controlling for age, gender, and educational level of household of origin, role of religion and trust in others sexual coercion was found to be statistically significantly associated with previously had sex (OR 1.6, 95% CI; 1.1-2.3), early sexual debut (OR 2.4, 95% CI; 1.5-3.7), as well as with having had a great number of sexual partners (OR 1.9, 95% CI; 1.2-3.0), but not with inconsistent condom use.</p> <p>Scoring low on an assessment of mental health problems, reporting high trust in others, or stating that religion played a major role in one's family of origin seemed to buffer the negative effect that the experience of sexual coercion had on the likelihood of having many sexual partners.</p> <p>Conclusion</p> <p>The findings of this study suggest that the experience of sexual coercion is common among youth/young adults in Uganda and is subsequently associated with risky sexual behavior in both sexes. The existence of individual and contextual factors that buffer the effects mentioned was also demonstrated. In the Ugandan context, this has implications for policy formulation and the implementation of preventive strategies for combating HIV/AIDS.</p