Navegando por Data de Publicação, começando com "2013-08-01"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 4 de 4

Transparência eletromagneticamente induzida em diferentes sistemas físicos e seu análogo em osciladores acoplados
(Universidade Federal de São Carlos, 2013-08-01) Cabral, Luís Antônio; Villas-Bôas, Celso Jorge; https://lattes.cnpq.br/5700887540085418; https://lattes.cnpq.br/2629141307724947
The simultaneously incidence of two light beams on one or more atoms causes destructive interference of these beams in atomic states causing cancellation of the absorption of one of the incident beams and this phenomenon is called Electromagnetically Induced Transparency (EIT). The main objective of this work is to show that the Electromagnetically Induced Transparency, which is usually studied in the quantum context, can be modeled classically as a function of coupled harmonic oscillators subject to an external force and dissipation. To will establish the classical equivalence, it will be presented the theory of the EIT in diferent quantum systems and also the theory of classic harmonic oscillators. Analogies will be performed comparing the classical and quantum equations of motion obtained for each scheme. For this, we perform the equivalence of EIT in quantum systems as atoms in three levels in Λ configuration, two-level atoms plus a cavity mode and the cavity optomechanics with the classical system of two coupled harmonics oscillator forced and damped. We also analyze the equivalence of two diferent quantum systems: three level atoms plus one cavity mode and four levels atoms in free space with a classical system composed by three coupled harmonic oscilators, forced and damped, in diferent configurations.
Influência das águas amazônicas no compromisso osmorrespiratório em osteoglossiformes
(Universidade Federal de São Carlos, 2013-08-01) Ramos, Cleverson Agner; Fernandes, Marisa Narciso; https://lattes.cnpq.br/9306613290256886
In the Amazon basin, the Osteoglossiforme order is represented by the species Osteoglossum ferreirai, O. bicirrhosum and Arapaima gigas. Although belonging to the same order, these species show different modes of breathing; while Osteoglossum ssp. is an obligatory water breather, A. gigas shows a gill remodeling during its development, which causes changes in the osmorespiratory compromise with implications for the gill functions which turns more related to the ion exchanges. The rivers of the Amazon basin have different physicochemical features. While the white water rivers (WW) are slightly alkaline and its waters are considered "soft", black water rivers (BW) are practically distilled" having an acidic pH. Such different characteristics between these waters leads to hypothesize that black water rivers can act as an hydrographic barrier, containing the spread of some species. This can be observed in the distribution of some amazonian fish since there are several species unique from black waters while other species are distributed in white and black waters as others only in white waters. In Osteoglossiformes, data from literature suggest O. bicirrhosum as a fish from white water, while A. gigas can be found in black water rivers as white water lakes. This study tested the hydrographic barrier hypothesis exposing the animals in the Amazonian waters and observing responses of ionic fluxes, proliferation of mitochondria rich cells (MRCs), responsible for regulating ion, the presence of mucous cells (MCs) and changes in morphology functional gills.In A. gigas 2000 g there is a fast recovery from ion losses so probably there is no influence of the hydrographic barrier for this specie. Comparing A. gigas and O. bicirrhosum, these fishes are able to ion regulation iin white water environments, mostly by the ion uptake showed in 3 hours. Data from immunohistochemistry for NKA enzyme of MRCs and morphometric data (CRMsFA and density) of these cell indicates that A. gigas 2000g have the gill functions related to ion regulation. About the ion regulation pattern and functional morphology there are similarities between O. bicirrhosum and 200g A. gigas however O. bicirrhosum did not showed the same potential to recovery ion losses as A. gigas.
Estudos qualitativos das transformações termodinâmicas ocorridas durante o processo pirometalúrgico de recuperação de Pb a partir de PbSO4
(Universidade Federal de São Carlos, 2013-08-01) Santin, Betânia de Oliveira; D'Alkaine, Carlos Ventura; https://lattes.cnpq.br/8699821828310072; https://lattes.cnpq.br/0036756630569466
This study was carried out in order to gain a qualitative understanding of one of the fundamental processes of pyrometallurgical recovery of Pbfrom the inorganic scraps of lead-acid batteries by the reduction of PbSO4to lead and connected reactions. Within a program of experiments concerning solid-solid reactions and, at high temperatures, solid-liquid or, at times, reactions involving gases, the work described here was an initial qualitative attempt to reveal the possible reaction mechanisms of the reduction of PbSO4 to Pb and the related reactions that can occur taking into account the composition of the lead-acid battery inorganic scraps (Pb and its possible alloys, PbO2, PbO e PbSO4). Since the pyrometallurgical processes includes the addition of C, Fe in filings and, in some cases, powered Na2CO3, the study was centered on the various possible reactions between these components and those of the scraps, with an emphasis on the PbSO4component. For this purpose, the various pure products then binary, ternary and quaternary mixtures were successively studied, to obtain information by comparing the results. The techniques used were thermogravimetry (TG) and differential thermal analysis (DTA) in the range 200o C to 1200 o C (this last temperature is the highest attained in industrial pyrometallurgicall process). The results showed several undescribed phenomena. The PbO can evaporate at higher temperatures. The presence of C facilitates the lowering of the PbSO4 thermal decomposition temperature. It also diminishes considerably the rate of PbO evaporating by favoring decomposition of PbO to Pb as has been previously suggested in the literature, but until now without experimental confirmation. Finally, the results do not permit a definite conclusion about the roles of Fe or Na2CO3. This is may be because in this study it was not to perform sufficient analytical identification measurements. Nevertheless, from the results, it is clear that the Fe is oxidized to an oxide iron at low temperatures (near 400o C) and it is this oxide which participates in the reactions at higher temperatures. On the other hand, the Na2CO3 is melted and immediately decomposed at about 800- 850o C. Thus, it will be in this conclusion when it takes put in the process.
Síntese e caracterização de nanopartículas de Nb2O5 e estudo de suas propriedades fotocatalíticas
(Universidade Federal de São Carlos, 2013-08-01) Lopes, Osmando Ferreira; Oliveira, Cauê Ribeiro de; https://lattes.cnpq.br/5321313558714462; https://lattes.cnpq.br/9493281509128559
In this study, the use of niobium oxide nanoparticles (Nb2O5) prepared through the OPM method as photocatalysts for the degradation of pollutants was investigated, describing the dependence on hydrothermal parameters (temperature and time) in aspects such as morphology, structure, electronic properties, and how these factors influence the photocatalytic activity. The catalytic activity of the samples was probed by evaluating the photodegradation under UV and visible irradiation of a dye (Rhodamine B, Rod.B) and a pesticide, Atrazine. An indirect measurement of the hydroxil radicals produced in the catalyst s surface was done by fluorescence spectroscopy, in order to evaluate the importance of this mechanism in the degradation process. The results showed that the Nb2O5 nanoparticles prepared by the OPM method are promising for the catalysis of photoactivated reactions. Surface hydroxylation and crystallinity were shown as the most important parameters involved in the activity per area of the nanoparticles, where the surface hydroxylation was more influent in the samples obtained in low temperature, whereas crystallinity was the key parameter for the obtained in higher temperatures. Under ultraviolet irradiation, the main photodegradation mechanism was governed by the . OH radical generation and attack. On the other hand, the dye-sensitization mechanism was shown as the main path for the degradation of Rod.B under visible irradiation.