Delimitação de áreas inundáveis a partir de Modified Normalized Difference Water Index (MNDWI) no Município de Esteio (RS, Brasil)

One of the possibilities of analysis from satellite images is the spatial and temporal variation of flodplains. Among the indices developed for analysis of water resources highlights the Modified Normalized Difference Water Index (MNDWI), prepared in order to highlight flood areas with a higher power of discrimination of targets. This work aims to verify the spatial and temporal dynamics of floods, using Landsat images to observe the overflow of water from the Sinos River, from MNDWI index, as support for the delimitation of flooding in the city of Esteio, located in the Metropolitan Region of Porto Alegre, Rio Grande do Sul, Brazil. Therefore, we used four dates of selected images from the reading of accumulated rainfall of ten and thirty days: 08/30/1984 and 03/30/2004 (low rainfall), 11/19/1990 and 10/01/2007 (highest accumulated rainfall). The first two dates showed average accumulated rainfall of 113.6 mm and 61.5 mm, within 30 days and 19.7 mm and 11.9 mm, within 10 days preceding ten image acquisition. The dates of 11/19/1990 and 10/01/2007 presented, respectively, 201.7 mm and 200.1 mm accumulated in the period of 30 days and 28.1 and 126.6 mm accumulated in the previous 10 days of the image acquisition. Concerning the analysis of flood spots in images with low accumulation of precipitation, average MNDWI stood at -0.33, that is lower in relation to the date 10/01/2007, with a mean of -0.11. This data can be seen mainly in points where flood spot was separated from MNDWI composition and overlaps on the city’s image, allowing the study of the influence of this flood in the flow of the streams that cutting through the city of Esteio.Uma das possibilidades de análise a partir de imagens de satélite é a variação espacial e temporal de comportamento de áreas inundáveis. Entre os índices desenvolvidos para análise de recursos hídricos, se destaca o Modified Normalized Difference Water Index (MNDWI), elaborado com o intuito de ressaltar áreas inundáveis com um maior poder de discriminação dos alvos. Esse trabalho tem como objetivo verificar a dinâmica espacial e temporal das inundações, utilizando imagens LANDSAT para observar o extravasamento das águas do Rio dos Sinos, a partir do índice MNDWI, como subsídio para a delimitação de inundações no município de Esteio, localizado na Região Metropolitana de Porto Alegre, Rio Grande do Sul, Brasil. Para tanto, foram utilizadas quatro datas de imagens selecionadas a partir da leitura da precipitação acumulada de dez e trinta dias: 30/08/1984 e 30/03/2004 (baixa precipitação), 19/11/1990 e 01/10/2007 (precipitação acumulada mais alta). As duas primeiras datas apresentaram precipitação média acumulada de 113,6 e 61,5 mm, no período de 30 dias e 19,7 mm e 11,9 mm, no período de 10 dez dias anteriores à aquisição da imagem. As datas de 19/11/1990 e 01/10/2007 apresentaram, respectivamente, 201.7 mm e 200.1 mm acumulados no período de 30 dias e 28.1 e 126.6 mm acumulados no perí- odo de 10 dias anteriores à imagem. Em relação às manchas de inundação, nas imagens com baixo acúmulo de precipitação, as médias de MNDWI ficaram em -0,33, ou seja, bem mais baixo em relação a 01/10/2007, com uma média de -0,11. Esse dado pode ser percebido principalmente nos pontos onde a mancha de inundação foi separada da composição MNDWI e sobreposta na imagem do município, propiciando o estudo da influência dessa inundação no escoamento dos arroios que cortam o município de Esteio

Vitamin C supplement use may protect against gallstones: an observational study on a randomly selected population

<p>Abstract</p> <p>Background</p> <p>Animal experiments have shown a protective effect of vitamin C on the formation of gallstones. Few data in humans suggest an association between reduced vitamin C intake and increased prevalence of gallstone disease. The aim of this study was to assess the possible association of regular vitamin C supplementation with gallstone prevalence.</p> <p>Methods</p> <p>An observational, population-based study of 2129 subjects aged 18-65 years randomly selected from the general population in southern Germany was conducted. Abdominal ultrasound examination, completion of a standardized questionnaire, compilation of anthropometric data and blood tests were used. Data were collected in November and December 2002. Data analysis was conducted between December 2005 and January 2006.</p> <p>Results</p> <p>Prevalence of gallstones in the study population was 7.8% (167/2129). Subjects reporting vitamin C supplementation showed a prevalence of 4.7% (11/232), whereas in subjects not reporting regular vitamin C supplementation, the prevalence was 8.2% (156/1897). Female gender, hereditary predisposition, increasing age and body-mass index (BMI) were associated with increased prevalence of gallstones. Logistic regression with backward elimination adjusted for these factors showed reduced gallstone prevalence for vitamin C supplementation (odds ratio, OR 0.34; 95% confidence interval, CI 0.14 to 0.81; P = 0.01), increased physical activity (OR 0.62; 95% CI, 0.42 to 0.94; P = 0.02), and higher total cholesterol (OR 0.65; 95% CI, 0.52 to 0.79; P < 0.001).</p> <p>Conclusion</p> <p>Regular vitamin C supplementation and, to a lesser extent, increased physical activity and total cholesterol levels are associated with a reduced prevalence of gallstones. Regular vitamin C supplementation might exert a protective effect on the development of gallstones.</p

An Essential Difference between the Flavonoids MonoHER and Quercetin in Their Interplay with the Endogenous Antioxidant Network

Antioxidants can scavenge highly reactive radicals. As a result the antioxidants are converted into oxidation products that might cause damage to vital cellular components. To prevent this damage, the human body possesses an intricate network of antioxidants that pass over the reactivity from one antioxidant to another in a controlled way. The aim of the present study was to investigate how the semi-synthetic flavonoid 7-mono-O-(β-hydroxyethyl)-rutoside (monoHER), a potential protective agent against doxorubicin-induced cardiotoxicity, fits into this antioxidant network. This position was compared with that of the well-known flavonoid quercetin. The present study shows that the oxidation products of both monoHER and quercetin are reactive towards thiol groups of both GSH and proteins. However, in human blood plasma, oxidized quercetin easily reacts with protein thiols, whereas oxidized monoHER does not react with plasma protein thiols. Our results indicate that this can be explained by the presence of ascorbate in plasma; ascorbate is able to reduce oxidized monoHER to the parent compound monoHER before oxidized monoHER can react with thiols. This is a major difference with oxidized quercetin that preferentially reacts with thiols rather than ascorbate. The difference in selectivity between monoHER and quercetin originates from an intrinsic difference in the chemical nature of their oxidation products, which was corroborated by molecular quantum chemical calculations. These findings point towards an essential difference between structurally closely related flavonoids in their interplay with the endogenous antioxidant network. The advantage of monoHER is that it can safely channel the reactivity of radicals into the antioxidant network where the reactivity is completely neutralized

Low level methylmercury exposure affects neuropsychological function in adults

BACKGROUND: The neurotoxic effects of methylmercury (MeHg) have been demonstrated in both human and animal studies. Both adult and fetal brains are susceptible to the effects of MeHg toxicity. However, the specific effects of adult exposures have been less well-documented than those of children with prenatal exposures. This is largely because few studies of MeHg exposures in adults have used sensitive neurological endpoints. The present study reports on the results of neuropsychological testing and hair mercury concentrations in adults (>17 yrs) living in fishing communities of Baixada Cuiabana (Mato Grosso) in the Pantanal region of Brazil. METHODS: A cross-sectional study was conducted in six villages on the Cuiaba River. Participants included 129 men and women older than 17 years of age. They were randomly selected in proportion to the age range and number of inhabitants in each village. Questionnaire information was collected on demographic variables, including education, occupation, and residence history. Mercury exposure was determined by analysis of hair using flameless atomic absorption spectrophotometry. The neurocognitive screening battery included tests from the Wechsler Memory Scale and the Wechsler Adult Intelligence Scale, Concentrated Attention Test of the Toulouse-Pierron Factorial Battery, the Manual Ability Subtests of the Tests of Mechanical Ability, and the Profile of Mood States. RESULTS: Mercury exposures in this population were associated with fish consumption. The hair mercury concentration in the 129 subjects ranged from 0.56 to 13.6 μg/g; the mean concentration was 4.2 ± 2.4 micrograms/g and the median was 3.7 μg/g. Hair mercury levels were associated with detectable alterations in performance on tests of fine motor speed and dexterity, and concentration. Some aspects of verbal learning and memory were also disrupted by mercury exposure. The magnitude of the effects increased with hair mercury concentration, consistent with a dose-dependent effect. CONCLUSIONS: This study suggests that adults exposed to MeHg may be at risk for deficits in neurocognitive function. The functions disrupted in adults, namely attention, fine-motor function and verbal memory, are similar to some of those previously reported in children with prenatal exposures