University of Trás-os-Montes and Alto Douro

About: University of Trás-os-Montes and Alto Douro is a education organization based out in Vila Real, Portugal. It is known for research contribution in the topics: Population & Context (language use). The organization has 2858 authors who have published 7146 publications receiving 138394 citations. The organization is also known as: University of Tras-os-Montes and Alto Douro & UTAD.

Histopathological changes in liver and gill epithelium of nile tilapia, oreochromis niloticus, exposed to waterborne copper

Abstract: Nile tilapia, Oreochromis niloticus, of both sexes were reared in freshwater and exposed to 05, 10 and 25mg L-1 of waterborne copper for a period of 21 days Liver and gill samples were collected after 21 days of exposure to copper and lesions were analyzed by light microscopy The main histopathological changes observed in gills exposed to the highest concentration were edema, lifting of lamellar epithelia and an intense vasodilatation of the lamellar vascular axis Although less frequent, lamellar fusion caused by the filamentar epithelium proliferation and some lamellar aneurisms were also found The liver of control group exhibited a quite normal architecture, while the fish exposed to copper showed vacuolation and necrosis These hepatic alterations were more evident in fish exposed to 10 and 25mg L-1 copper concentrations The number of hepatocytes nucleus per mm² of hepatic tissue decreased with the increase of copper concentration In contrast, the hepatic somatic index was high in fish exposed at 25mg L-1 of copper In short, this work advance new knowledge as influence of copper in the gill and liver histology of O niloticus and demonstrated that their effects could be observed at different concentrations

Sol−Gel Derived Urea Cross-Linked Organically Modified Silicates. 2. Blue-Light Emission

Abstract: The photoluminescence and the local structure of sol−gel derived organic−inorganic hybrids, so-called ureasils, are discussed. Their host matrix is a silica-based network to which different numbers of oxyethylene repeat units8.5, 15.5, and 40.5 for U(600), U(900), and U(2000), respectivelyare covalently grafted by means of urea linkages. The small-angle X-ray scattering (SAXS) results suggest a diphasic structure for the morphology of the hybrids induced by local phase separation between siliceous domains and polymeric regions. The estimated interdomain distances, ranging from 27 A for U(600) to 59−64 A for U(2000), indicate that the three ureasils are greatly homogeneous on the SAXS scale. The luminescence spectra show a broad light emission (2.0−4.1 eV) with a blue band at ∼2.6 eV and a purplish-blue one at ∼2.8−3.0 eV, clearly distinguished by time-resolved spectroscopy. The energies of these two components are related to the dimension of the backbone inorganic skeleton. The local structure of these am...

Role of temperature and humidity in the modulation of the doubling time of COVID-19 cases

Abstract: COVID-19 is having a great impact on public health, mortality and economy worldwide, in spite of the efforts to prevent its epidemy. The SARS-CoV-2 genome is different from that of MERS-CoV and SARS-CoV, although also expected to spread differently according to meteorological conditions. Our main goal is to investigate the role of some meteorological variables on the expansion of this outbreak. In this study, an exponential model relating the number of accumulated confirmed cases and time was considered. The rate of COVID-19 spread, using as criterion the doubling time of the number of confirmed cases, was used as dependent variable in a linear model that took four independent meteorological variables: temperature, humidity, precipitation and wind speed. Only China cases were considered, to control both cultural aspects and containment policies. Confirmed cases and the 4 meteorological variables were gathered between January 23 and March 1 (39 days) for the 31 provinces of Mainland China. Several periods of time were sampled for each province, obtaining more than one value for the rate of disease progression. Two different periods of time were tested, of 12 and 15 days, along with 3 and 5 different starting points in time, randomly chosen. The median value for each meteorological variable was computed, using the same time period; models with were selected. The rate of progression and doubling time were computed and used to fit a linear regression model. Models were evaluated using α = 0.05. Results indicate that the doubling time correlates positively with temperature and inversely with humidity, suggesting that a decrease in the rate of progression of COVID-19 with the arrival of spring and summer in the north hemisphere. A 20°C increase is expected to delay the doubling time in 1.8 days. Those variables explain 18% of the variation in disease doubling time; the remaining 82% may be related to containment measures, general health policies, population density, transportation or cultural aspects.