Navegando por Data de Publicação, começando com "2004-03-26"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 5 de 5

Estudos de ionização de moléculas poliatômicas de interesse tecnológico
(Universidade Federal de São Carlos, 2004-03-26) Sanches, Ivana Pereira; Iga, Ione; https://lattes.cnpq.br/8934634344275868
Complex polyatomic compounds are increasingly being used for modern technological applications, e.g., those related to the semiconductor industry, generation of new materials etc. However, there is a big lack of knowledge of the fundamental properties of such relevant chemical species, and more investigations of them are highly desirable. In the above context, we have studied electron impact partial and total ionization cross sections, in the energy range of Emin 1000 eV for molecules like CHF3, C2F6, CF3Cl and C2H4. A time-of-flight mass spectrometer developed at the Laboratório de Espalhamento de Elétrons, at the chemistry department of UFSCar, was used to perform these studies. Absolute scattering cross sections were obtained using the relative flow technique. Also, we have begun studies using the synchrotron radiation in pulsed mode with a view to determine the photoionization cross sections at the Laboratório Nacional de Luz Síncrotron. In this work we have tested the viability of this method to determine the photoionization cross section by studying the gases for which these cross sections are already present in the literature.
Perturbação hidrológica, estabilidade e diversidade de macroinvertebrados em uma zona úmida (lagoas intermitentes) do semi-árido brasileiro
(Universidade Federal de São Carlos, 2004-03-26) Silva-Filho, Manoel Inácio; Gessner, Alaíde Aparecida Fonseca; https://lattes.cnpq.br/8465752836529703; https://lattes.cnpq.br/5557996426005126
Intermittent shallow lakes are a kind of wetland of great importance in the Brazilian semiarid area, being characterized by hydrological extremes of flood and drought. These shallow lakes are good model for ecological study because they have discrete boundaries, and are subject to disturbance processes such as drying. The goal of this study was to analyse, in according to the conceptual mark of natural disturbances and ecological stability, the diversity and stability of the macroinvertebrates in three Brazilian semi-arid intermittent lakes during two hydrological cycles. In this study, I also compare the diversity of the macroinvertebrate communities to the hydrological disturbance; analyse the degree of resilience and resistance of the community to the drought, as well as, the relationship between diversity and stability in the community studied. Furthermore, I accomplished the inventory of the fauna of macroinvertebrates of 33 intermittent shallow lakes widespread in the Paraibano semi-arid. The results of this study suggest that (i) flooding and drought are the main disturbance agents in these shallow lakes, which are events of great importance to explain the model of macroinvertebrates succession; (ii) in the lakes studied I did not determined the pattern of macroinvertebrate diversities, because a peculiar pattern of diversity seemed to occur in each hydrological cycle; (iii) the species richness was relatively high and the number of individuals small; (iv) the macroinvertebrate populations varied substantially during the hydrological cycle due to variation of the water level and the impacts of the drought; (v) the resistance and resilience of the macroinvertebrate communities to drought demonstrated to be relatively high; and (vi) the variability of the total biomass of macroinvertebrate communities was lower in the lake that exhibited high species richness, while the variability of the abundance of the populations in each species was lower in the lakes with larger species richness of macroinvertebrates.
Estudo do efeito da correlação do alvo no espalhamento de elétrons por moléculas pequenas na faixa de energias baixas e intermediária
(Universidade Federal de São Carlos, 2004-03-26) Cerqueira Sobrinho, Antonio Moreira de; Tao, Lee Mu; https://lattes.cnpq.br/5112032594921811
In this present work, we have carried out a theoretical investigation on the influence of the target electronic correlation on electron elastic scattering by molecules. Calculated differential, integral and momentum-transfer cross sections on electron elastic scattering by nitrous oxide (N2O) and carbon dioxide (CO2), in low energy range (0.1-20 eV), and carbon monosulfide (CS) and silicon monosulfide (SiS), in low and intermediate energy range (0.1-500 eV) are reported. In this study target wave functions at the Hartree-Fock-Roothaan (HFR) and with single-double excitation configuration interaction (SDCI) levels were calculated. The dynamics of electron-molecule interaction is described by a complex optical potential formed by static, of exchange and correlationpolarization contributions, and for e−CS and e−SiS collisions, we include also the absorption contribution, as the imaginary part of optical potential, to account for the influence of inelastic channels at higher energies. The Schwinger variational iterative method (SVIM) combined with distorted-wave approximation is applied to calculate the scattering amplitudes. The results of cross sections, calculated for both HFR and SDCI functions are presented and compared, along with experimental and/or other theoretical results available in the literature.
Aspectos biológicos de Heterotermes tenuis (Isoptera Rhinotermidae) em cana-de-açúcar
(Universidade Federal de São Carlos, 2004-03-26) Campos, Maria Bernadete Silva de; Macedo, Newton; https://lattes.cnpq.br/2167952105880286; https://lattes.cnpq.br/5024245659105477
The main objectives were: to study at laboratory some biological aspects the biology of Heterotermes tenuis, by stablishing colonies with couples collected in the field, foraging behavior and the intraspecific agonistic behavior among individuals from different places in area sugarcane, collected by baits. The stablishment of colonies was studied from September/2002 to December/2003, with the installation of 400 baits in of 10.000 m2 sugarcane area, to collect the couples. The collected couples were removed and aconditioned in plastic flasks containing humidified soil and food and maintained in room at 28°C ± 2°C, 70% RU and 12 hours of photophase. Biological studies was systematicaly the colonies for counting alive couples, presence and number of eggs, breeds (workers and soldiers). The couples showed a period of 29 days before oviposition and a number of five eggs/ colony in the first oviposition, in average. The egg measures were 0.68 mm length and 0.36 mm width. The first workers appeared 53 days after the formation of the couples, and the number was four workes/colony. The first soldiers appeared 127 days after the formation of the couples, with an average of 1 soldier/colony. Foraging behavior was studied from 1999, April to 2003, December with the installation of 27 baits in three different places with nine points each. Monthly the baits were removed and a new one were placed. Baits with termites present were carried to laboratory for individuals counting. It was observed that there were significant variances in the foraging activity according to rain precipitation and environmental temperature variations and it was affected, as well, by development cycle and growth of the colony. The maximum foraging activity occures in the autumn and the agricultural pratices as plowing and furrowing for new planting promote a drastic foraging activity redutions in the subsequent years. Intraspecific agonistic behavior of H. tenuis was studied by confrontation tests between places and different points. In each confrontation 20 workers plus two soldiers were placed in a transparent plastic flask (7,0 cm of height x 4,5 cm of diameter) with bottom covered by filter paper and a square of humidified fiberboard (4 cm2) . The evaluations were done 48 hours after the confrontation by counting dead individuals. It was verified that there is intra-specific agonistic behavior in H. tenuis and by means that behavior different colonies can be distinguished and its forraging areas can be delimited in sugarcane areas.
A grande seca de 1979 a 1983: um estudo de caso das ações do governo federal em duas sub-regiões do estado do Ceará (Sertão Central e Sertão de Inhamuns)
(Universidade Federal de São Carlos, 2004-03-26) Campos, Nivalda Aparecida; Villa, Marco Antonio; https://lattes.cnpq.br/9571225340239118
The subject of this article is the State intervention in two macro regions of the Brazilian state of Ceará: Central Hinterlands and Inhamuns Hinterlands during the hard drought of 1979-1983. The objective was to identify why the effects of the weather phenomenon were so catastrophic even with the governmental programs being developed. During the researches, it was observed that the principles and strategies that orientate the intervention in the semi-arid Northeast region has been conservative and concentrative, beneficiating only certain groups.