Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Dry matter. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Spatial and temporal variation of precipitation in the State of Pará

Abstract: Studies about the climatology of precipitation in the State of Para are essential for the planning of agricultural activities. The variation of annual and seasonal precipitation in Para was analysed based on a historic series of 23 years (1976 1998) of daily rainfall data. The analysis was made for 31 locations in Para, using geographic information systems techniques, with the results presented in maps. The variability of annual and seasonal precipitation was characterized based on the coefficient of variation and the index of relative interanual variability. The variation of these coefficients for the annual precipitation in Para was 15 to 30 %. The monthly characteristics of the wet season, in terms of beginning, end and duration, were determined using a criteria proposed by KASSAM (1979). The variation between early planting dates and late planting dates were identified by the periods of julian days of 309 319 and 353 363, respectively.

From Local to Global: The Anti-Dam Movement in Southern Brazil, 1979-1992

Abstract: A case study of the anti-dam movement in southern Brazil shows how particular local mobilizations are linked to national and global economics, politics, and social movements. In the early stages, the progressive church was the predominant influence and was largely responsible for framing the key issue as peasants' right to land, while left intellectuals contributed a class analytical frame. After 1988, the weakening of the regional power company ELETROSUL, the crisis of the Left after the fall of the Berlin Wall, the defeat of the agrarian reform movement, the rise of national and international ecology movements, and the anti-dam movement's need for a broader political and financial base all contributed to the adoption of a broadened and more pro-active land/energy/ecology frame and an alliance with international environmentalism.

Boolean network model for cancer pathways: predicting carcinogenesis and targeted therapy outcomes.

Abstract: A Boolean dynamical system integrating the main signaling pathways involved in cancer is constructed based on the currently known protein-protein interaction network. This system exhibits stationary protein activation patterns – attractors – dependent on the cell's microenvironment. These dynamical attractors were determined through simulations and their stabilities against mutations were tested. In a higher hierarchical level, it was possible to group the network attractors into distinct cell phenotypes and determine driver mutations that promote phenotypic transitions. We find that driver nodes are not necessarily central in the network topology, but at least they are direct regulators of central components towards which converge or through which crosstalk distinct cancer signaling pathways. The predicted drivers are in agreement with those pointed out by diverse census of cancer genes recently performed for several human cancers. Furthermore, our results demonstrate that cell phenotypes can evolve towards full malignancy through distinct sequences of accumulated mutations. In particular, the network model supports routes of carcinogenesis known for some tumor types. Finally, the Boolean network model is employed to evaluate the outcome of molecularly targeted cancer therapies. The major find is that monotherapies were additive in their effects and that the association of targeted drugs is necessary for cancer eradication.

Modeling the Spatiotemporal Epidemic Spreading of COVID-19 and the Impact of Mobility and Social Distancing Interventions

Abstract: On 31 December, 2019, an outbreak of a novel coronavirus, SARS-CoV-2, that causes the COVID-19 disease, was first reported in Hubei, mainland China This epidemics' health threat is probably one of the biggest challenges faced by our interconnected modern societies According to the epidemiological reports, the large basic reproduction number R-0 similar to 3 0, together with a huge fraction of asymptomatic infections, paved the way for a major crisis of the national health capacity systems Here, we develop an age-stratified mobility-based metapopulation model that encapsulates the main particularities of the spreading of COVID-19 regarding (i) its transmission among individuals, (ii) the specificities of certain demographic groups with respect to the impact of COVID-19, and (iii) the human mobility patterns inside and among regions The full dynamics of the epidemic is formalized in terms of a microscopic Markov chain approach that incorporates the former elements and the possibility of implementing containment measures based on social distancing and confinement With this model, we study the evolution of the effective reproduction number R(t), the key epidemiological parameter to track the evolution of the transmissibility and the effects of containment measures, as it quantifies the number of secondary infections generated by an infected individual The suppression of the epidemic is directly related to this value and is attained when R < 1 We find an analytical expression connecting R with nonpharmacological interventions, and its phase diagram is presented We apply this model at the municipality level in Spain, successfully forecasting the observed incidence and the number of fatalities in the country at each of its regions The expression for R should assist policymakers to evaluate the epidemics' response to actions, such as enforcing or relaxing confinement and social distancing

Spin-Current to Charge-Current Conversion and Magnetoresistance in a Hybrid Structure of Graphene and Yttrium Iron Garnet.

Abstract: The use of graphene in spintronic devices depends, among other things, on its ability to convert a spin excitation into an electric charge signal, a phenomenon that requires a spin-orbit coupling (SOC). Here we report the observation of two effects that show the existence of SOC in large-area CVD grown single-layer graphene deposited on a single crystal film of the ferrimagnetic insulator yttrium iron garnet (YIG). The first is a magnetoresistance of graphene induced by the magnetic proximity effect with YIG. The second is the detection of a dc voltage along the graphene layer resulting from the conversion of the spin current generated by spin pumping from microwave driven ferromagnetic resonance into a charge current, which is attributed to the inverse Rashba-Edelstein effect.