J. Da Silva - Academia.edu (original) (raw)
Papers by J. Da Silva
Time series of water stages derived from satellite radar altimetry are of very variable quality, ... more Time series of water stages derived from satellite radar altimetry are of very variable quality, depending on the mission, the tracking scheme and the geomorphological context of the crossing between the satellite track and the river. Also, it has long been observed that this quality is dependent on the hydrological cycle itself: stage values are often much worse at low water compared to those determined at high waters. This problem is mostly due to the data selection. Indeed, common window for data selection is mostly geographical. At low waters, measurements contaminated/distorted by non-water reflectors are more likely present within the selection window because of emerged river banks and/or islets. We have developped a processing scheme based on the GRASS freeware GIS to improve the selection of the satellite measurements and reduce the incorporation of non-water measurement within the dataset retained for estimating the water stage. This scheme has been successfully applied to the ENVISAT mission over the Rio Negro where reliable water stages could be obtained far upstream at both high and low waters, and also over adjacent wetlands.
Revista do Hospital das Clínicas
Phytochemistry, 2000
Two enzymes characterised as iodoperoxidases (PcI and PcII), with vanadium-dependent activity, ha... more Two enzymes characterised as iodoperoxidases (PcI and PcII), with vanadium-dependent activity, have been purified from the brown alga Pelvetia canaliculata (L.) Decne et Thur. (Fucaceae, Phaeophyceae), collected in the Northern Portuguese coast, at Viana do Castelo. The relative molecular masses were 166 kDa for PcI and 416 kDa for PcII, as determined by gel filtration. SDS-PAGE shows that PcI has just one band corresponding to a subunit of 66 kDa, while PcII shows four bands (66, 72, 157 and 280 kDa). The following kinetic parameters have been determined from a steady-state analysis of the oxidation of iodide by H2O2: PcI, pHopt = 6.0, KM(I-) = 2.1 mM, KM(H2O2) = 110 microM, Ki(I-) = 127 mM; and PcII, pHopt = 6.5, KM(I-) = 2.4 mM, KM(H2O2) = 20 microM and Ki(I-) = 69 mM. These iodoperoxidases are thermostable, as also observed for vanadium bromo- and chloroperoxidases.
Revista do Hospital das Clínicas, 1980
Revista do Hospital das Clínicas
Revista do Hospital das Clínicas, 1979
Revista da Sociedade Brasileira de Medicina Tropical, 1995
The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hemato... more The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hematological, histopathological and immunohistochemical alterations in sixty animals inoculated by the intraperitoneal route with 1ml of the culture of virulent strain of Leptospira interrogans serovar copenhageni. Leptospirae antigens were detected by immunoperoxidase, chiefly in liver, kidney and heart muscle capillaries. Possible pathogenic mechanisms responsible for hemorrhagic syndrome are discussed with emphasis on toxic and anoxic attacks causing damage to endothelia, platelet depletion and alterations to hemostasia rates: prothrombin time [PT], partial thromboplastin time [PTT] and fibrinogen concentrations. The clinical-laboratory picture is compatible with the histopathological observation of disseminated intravascular coagulation [DIC] in most of the guinea pigs from day 4 of infection.
Journal of insect science (Online), 2005
The Southern Green Stink Bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), is a cosmopolitan... more The Southern Green Stink Bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), is a cosmopolitan and economically important pest to several crops. Studies on N. viridula migration and population structure have been neglected. We studied geographically distinct Brazilian N. viridula populations to assess their variability and to determine gene flow among them. DNA from specimens collected on soybean fields were subjected to RAPD analysis to determine genetic similarity and population structure parameters. All N. viridula populations studied were genetically distinct from the others. The maximum similarity occurred between populations from Londrina and Sertanópolis (Parana State). The Cruz Alta population was the most divergent from the others. Despite the short distance between Cambé and Londrina (ca. 29 km), and the absence of geographic barriers, both populations clustered in different groups and the estimated gene flow index (Nm) among them was 2.02, indicating relatively restric...
Neotropical Entomology, 2012
… integrated surface and …, 2009
The combined use of satellite imagery and radar altimetry offers entirely new perspectives for th... more The combined use of satellite imagery and radar altimetry offers entirely new perspectives for the monitoring of water resources in large tropical transboundary basins. We illustrate this point of view with results from a study conducted mostly in the region of the Llanos de Mojos, a ...
Time series of water stages derived from satellite radar altimetry are of very variable quality, ... more Time series of water stages derived from satellite radar altimetry are of very variable quality, depending on the mission, the tracking scheme and the geomorphological context of the crossing between the satellite track and the river. Also, it has long been observed that this quality is dependent on the hydrological cycle itself: stage values are often much worse at low water compared to those determined at high waters. This problem is mostly due to the data selection. Indeed, common window for data selection is mostly geographical. At low waters, measurements contaminated/distorted by non-water reflectors are more likely present within the selection window because of emerged river banks and/or islets. We have developped a processing scheme based on the GRASS freeware GIS to improve the selection of the satellite measurements and reduce the incorporation of non-water measurement within the dataset retained for estimating the water stage. This scheme has been successfully applied to the ENVISAT mission over the Rio Negro where reliable water stages could be obtained far upstream at both high and low waters, and also over adjacent wetlands.
Revista do Hospital das Clínicas
Phytochemistry, 2000
Two enzymes characterised as iodoperoxidases (PcI and PcII), with vanadium-dependent activity, ha... more Two enzymes characterised as iodoperoxidases (PcI and PcII), with vanadium-dependent activity, have been purified from the brown alga Pelvetia canaliculata (L.) Decne et Thur. (Fucaceae, Phaeophyceae), collected in the Northern Portuguese coast, at Viana do Castelo. The relative molecular masses were 166 kDa for PcI and 416 kDa for PcII, as determined by gel filtration. SDS-PAGE shows that PcI has just one band corresponding to a subunit of 66 kDa, while PcII shows four bands (66, 72, 157 and 280 kDa). The following kinetic parameters have been determined from a steady-state analysis of the oxidation of iodide by H2O2: PcI, pHopt = 6.0, KM(I-) = 2.1 mM, KM(H2O2) = 110 microM, Ki(I-) = 127 mM; and PcII, pHopt = 6.5, KM(I-) = 2.4 mM, KM(H2O2) = 20 microM and Ki(I-) = 69 mM. These iodoperoxidases are thermostable, as also observed for vanadium bromo- and chloroperoxidases.
Revista do Hospital das Clínicas, 1980
Revista do Hospital das Clínicas
Revista do Hospital das Clínicas, 1979
Revista da Sociedade Brasileira de Medicina Tropical, 1995
The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hemato... more The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hematological, histopathological and immunohistochemical alterations in sixty animals inoculated by the intraperitoneal route with 1ml of the culture of virulent strain of Leptospira interrogans serovar copenhageni. Leptospirae antigens were detected by immunoperoxidase, chiefly in liver, kidney and heart muscle capillaries. Possible pathogenic mechanisms responsible for hemorrhagic syndrome are discussed with emphasis on toxic and anoxic attacks causing damage to endothelia, platelet depletion and alterations to hemostasia rates: prothrombin time [PT], partial thromboplastin time [PTT] and fibrinogen concentrations. The clinical-laboratory picture is compatible with the histopathological observation of disseminated intravascular coagulation [DIC] in most of the guinea pigs from day 4 of infection.
Journal of insect science (Online), 2005
The Southern Green Stink Bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), is a cosmopolitan... more The Southern Green Stink Bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), is a cosmopolitan and economically important pest to several crops. Studies on N. viridula migration and population structure have been neglected. We studied geographically distinct Brazilian N. viridula populations to assess their variability and to determine gene flow among them. DNA from specimens collected on soybean fields were subjected to RAPD analysis to determine genetic similarity and population structure parameters. All N. viridula populations studied were genetically distinct from the others. The maximum similarity occurred between populations from Londrina and Sertanópolis (Parana State). The Cruz Alta population was the most divergent from the others. Despite the short distance between Cambé and Londrina (ca. 29 km), and the absence of geographic barriers, both populations clustered in different groups and the estimated gene flow index (Nm) among them was 2.02, indicating relatively restric...
Neotropical Entomology, 2012
… integrated surface and …, 2009
The combined use of satellite imagery and radar altimetry offers entirely new perspectives for th... more The combined use of satellite imagery and radar altimetry offers entirely new perspectives for the monitoring of water resources in large tropical transboundary basins. We illustrate this point of view with results from a study conducted mostly in the region of the Llanos de Mojos, a ...