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 & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Caracterização morfométrica da bacia hidrográfica do rio Debossan, Nova Friburgo, RJ

Abstract: The objective of this work was to perform a morphometric characterization based on some physical parameters. In order to do so, a Hydrologically Consistent Digital Elevation Model (HCDEM) was generated from IBGE topographical maps, scale 1:50.000, using as database and analysis the system of geographic information, by means of the ArcVIEW and Arc/INFO version 8.3 systems. From this, some morphometric parameters of a previous study on the hydrologic behavior of the watershed were calculated. The drainage area was 9,9156 Km2 and 17,684 km in perimeter. The Debossan river watershed was proven not easily subject to floods as the compacity coefficient was far from the unit (1.5842) and its shape factor presented a low value (0.3285). Such fact can still be proven by the circularity index value (0.3985). The drainage density was 2,3579 Km/Km2, showing that the watershed has average draining capacity. The drainage system forms a dendritic pattern. This pattern occurs in high lands, in which the regolith and the parent rock relatively provide a uniform resistance to erosion. The more elongated watershed shape, as the circularity index, shape factor and compacity coefficient, indicates that the rainwater volume that falls within the watershed is concentrated in different points, contributing to reduce rain intensities that could cause greater flow variations.

MODIS land cover and LAI collection 4 product quality across nine sites in the western hemisphere

Abstract: Global maps of land cover and leaf area index (LAI) derived from the Moderate Resolution Imaging Spectrometer (MODIS) reflectance data are an important resource in studies of global change, but errors in these must be characterized and well understood. Product validation requires careful scaling from ground and related measurements to a grain commensurate with MODIS products. We present an updated BigFoot project protocol for developing 25-m validation data layers over 49-km2 study areas. Results from comparisons of MODIS and BigFoot land cover and LAI products at nine contrasting sites are reported. In terms of proportional coverage, MODIS and BigFoot land cover were in close agreement at six sites. The largest differences were at low tree cover evergreen needleleaf sites and at an Arctic tundra site where the MODIS product overestimated woody cover proportions. At low leaf biomass sites there was reasonable agreement between MODIS and BigFoot LAI products, but there was not a particular MODIS LAI algorithm pathway that consistently compared most favorably. At high leaf biomass sites, MODIS LAI was generally overpredicted by a significant amount. For evergreen needleleaf sites, LAI seasonality was exaggerated by MODIS. Our results suggest incremental improvement from Collection 3 to Collection 4 MODIS products, with some remaining problems that need to be addressed

Characterization of a new world monopartite begomovirus causing leaf curl disease of tomato in Ecuador and Peru reveals a new direction in geminivirus evolution.

Abstract: All characterized whitefly-transmitted geminiviruses (begomoviruses) with origins in the New World (NW) have bipartite genomes composed of a DNA-A and DNA-B component. Recently, an NW begomovirus lacking a DNA-B component was associated with tomato leaf curl disease (ToLCD) in Peru, and it was named Tomato leaf deformation virus (ToLDeV). Here, we show that isolates of ToLDeV associated with ToLCD in Ecuador and Peru have a single, genetically diverse genomic DNA that is most closely related to DNA-A components of NW bipartite begomoviruses. Agroinoculation of multimeric clones of the genomic DNA of three ToLDeV genotypes (two variants and a strain) resulted in the development of tomato leaf curl symptoms indistinguishable from those of ToLCD in Ecuador and Peru. Biological properties of these ToLDeV genotypes were similar to those of Old World (OW) monopartite tomato-infecting begomoviruses, including lack of sap transmissibility, phloem limitation, a resistance phenotype in tomato germplasm with the Ty-1 gene, and functional properties of the V1 (capsid protein) and C4 genes. Differences in symptom phenotypes induced by the ToLDeV genotypes in tomato and Nicotiana benthamiana plants were associated with a highly divergent left intergenic region and C4 gene. Together, these results establish that ToLDeV is an emergent NW monopartite begomovirus that is causing ToLCD in Ecuador and Peru. This is the first report of an indigenous NW monopartite begomovirus, and evidence is presented that it emerged from the DNA-A component of a NW bipartite progenitor via convergent evolution and recombination.

Chemical and Mineralogical Properties of Kaolinite-Rich Brazilian Soils

Abstract: Highly weathered kaolinitic soils in Brazil often have adequate levels of K and Mg to support plant growth. The source of K and Mg in these soils and their relationship with the dominant mineral, kaolinite, is addressed in this article. Crystallographic, chemical, and morphological properties of kaolinite, from selected highly weathered Brazilian soils, were investigated by x-ray diffraction (XRD), analytical electron microscopy (AEM), chemical, and thermal methods. Kaolinite properties showed significant variations such as d(001) spacing ranging between 0.713 to 0.728 nm, width at half height (WHH) between 0.30 to 0.97 °20, and dehydroxylation temperature between 489 to 518°C. Kaolinite in the clay fraction has relatively poor crystal order with a mean crystallinity index value(CI) of 12.7. The dominant forms of the clay-fraction kaolinite were elongated and rounded, with relatively lower proportions of hexagonal particles. The silt-fraction kaolinite showed a tendency to form subspherical large aggregates with high stability. The average Fe 2 O 3 level in the kaolinite of the clay fraction (19.1 g kg -1 ) was higher than that obtained for the silt fraction (6.6 g kg -1 ). The smaller kaolinite particles of the clay fraction showed a lower degree of crystal order, higher K and Mg levels, and lower dehydroxylation temperatures. From the strong relationship between the asymmetry index (AI) of the (001) diffraction line and the level of K in kaolinite from the younger soils, we believe that both K and Mg in kaolinite are part of residual micaceous layers interleaved in kaolinite crystals.