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Transferência de massa em reator eletroquímico de carbono vítreo reticulado
(Universidade Federal de São Carlos, 2010-03-02) Costa, Pedro Henrique de Britto; Ruotolo, Luís Augusto Martins; https://lattes.cnpq.br/9718347600666805
In this work, the electrodeposition of toxic metals, copper and zinc in this case, onreticulated vitreous carbon (RVC) electrode was studied. The effect of EDTA presence on thecopper electrodeposition process was also evaluated. The electrolytic process took place in anelectrochemical reactor projected with a filter-press configuration, however, with a fewmodifications aiming of a decrease in charge loss. The electrochemical reactor consisted of anRVC porous cathode of 45 ppi and was characterized in terms of mass transfer coefficient(km) which was determined through voltametric and galvanostatic electrodepositiontechniques. In a second phase of this work, the electrodeposition kinetic was studied throughthe application of different current values stipulated as a fraction of the limiting current(α = I / I lim) which was calculated by using km values obtained during the first phase. Thecopper electrodeposition results showed that the voltametric and galvanostatic techniques todetermine km presented very similar values and that the electrodeposition kinetic was nearlyindependent of pH in acid media with pH values between 2 and 4. When it comes to thecopper electrodeposition in EDTA medium, it was observed that the presence of organiccomplexes significantly alter the electrodeposition process and that further phenomena, otherthan mass transfer, control the process. The voltametric technique was not efficient todetermine km values for the zinc electrodeposition and the pH must be controlled with valuesaround 5 in order for galvanostatic electrodeposition to occur. The following correlation formass transfer in the proposed electrochemical reactor was obtained by using the copperelectrodeposition results: Sh = 1.39Re0.57Sc0.33. The comparison of this correlation with that ofother electrochemical reactors cited in the literature showed that it is very efficient when itcomes to mass transfer, and that the presence of the RVC considerably improves theelectrodeposition process. The electrodeposition kinetic results were analyzed in terms ofinstantaneous and global current efficiency and energy consumption efficiencies as a functionof α. It was verified that for Cu2+ and Zn2+ electrodeposition there is an α value whichmaximizes current efficiency and minimizes energy consumption. The optimum α valuedepends on the metal that is being electrodeposited and is lower than 1.0 due to the fact thatthe application of currents lower than the limiting one provides a higher operation time underactivated or mixed control conditions. Finally, it should be observed that the electrodepositionin the presence of EDTA presented an inverse behavior, once the greatest α value studied wasthe one which presented the best results.
Distribuição espacial de espécies arbóreas de cerrado: filogenia e traços de defesa contra herbivoria
(Universidade Federal de São Carlos, 2010-03-02) Loiola, Priscilla de Paula; Batalha, Marco Antônio Portugal Luttembarck; https://lattes.cnpq.br/3893228815181339; https://lattes.cnpq.br/2691455603546958
Herbivory is expected to promote an overdispersed distribution of traits in co-occurring plant species, since similar plants are more vulnerable to specialised herbivores. As long as conservatism of traits is usually observed in lineages of plant species, phylogenetic relatedness may also be related to spatial distribution. Thus, we expected that defense traits against herbivory were conserved and that phylogenetic distances of co-occurring species were higher than expected by chance. In a cerrado site in southeastern Brazil, we analysed 100 quadrats, with 25 m 2 each, and sampled all woody individuals. For each species, we measured defense traits against herbivory and answered whether the degree of co-occurrence of species was correlated with both functional differences and phylogenetic distances. We also tested whether the defense traits were phylogenetically conserved. On the one hand, we did not find significant correlation between species co-occurrence and neither defense traits nor phylogenetic distances. On the other hand, we found phylogenetic signal for four out of nine defense traits. The absence of correlations may be due to (1) herbivory not being as strong as we expected in cerrado vegetation or (2) the presence of environmental filters, such as drought and nutrient-poor soil, promoting phylogenetic clustering, counteracting phylogenetic overdispersion by herbivory.
Defesas contra herbivoria e descritores da vegetação: relações com variáveis edáficas em uma área de cerrado
(Universidade Federal de São Carlos, 2010-03-02) Dantas, Vinícius de Lima; Batalha, Marco Antônio Portugal Luttembarck; https://lattes.cnpq.br/3893228815181339; https://lattes.cnpq.br/3386981992178350
Together with fire and climate changes, soil is considered a major determinant in the Braziliancerrado, the richest savanna in the world. Soil can influence plants by filtering species capableof acquiring resources and compete for them, but can also influence plant patterns ofallocation in defense against herbivory. Although many studies focused on plant soilrelationship in cerrado, few focused on the influence of soil at fine scale. We expectedcommunity descriptors, such as floristic composition, richness, evenness, diversity, and totalabundance to be related to soil features at fine scale within a physiognomy. We also expectedplants on nutrient-poor soils to present higher anti-herbivory defenses. In a cerrado site, weplaced 100 contiguous 25 m2 plots, in which we identified all woody individuals, measuredsoil variables and the following leaf traits: specific leaf area, C:N ratio, water content,toughness, trichomes, latex, and presence of tannins, alkaloids, and terpenoids. We did apartial redundancy analysis to test for relationship between soil features and floristiccomposition, controlled for spatial dependence. We also did multiple regression or spatialautoregressive models to test for relationships between soil features and: (1) the abundance ofthe five commonest species, (2) total abundance, (3) richness, (4) evenness, and (5) diversityand to predict defense traits based on soil features. We found no relationship between soil andfloristic composition, probably due to functional redundancy or limited dispersal. Organicmatter was positively related to Myrsine umbellata, the most abundant species, and totalabundance, and negatively related to evenness, what suggests positive feedbacks to cause thedominance by Myrsine umbellata. We also found a positive relationship between sum of basisand species richness, probably reflecting a fertility gradient. Contrary to our expectations, wefound no relationship between total defenses and total soil fertility or soil variables, whatcould result from low variability in soil fertility at fine scale or of high phenotypic variability.Presence of tannins was positively related to organic matter, possibly reflecting a strategytowards lower tolerance due to low reserve allocation or interactions with other resources.However, since tannins decrease leaf decomposition rates, organic matter could beaccumulating in soil. Overall, we suggest that soil is an important factor structuring cerradocommunity even at fine scales and that the dominance of cerrado species could be related topositive plant-soil feedbacks.
Estudo de efeitos quânticos nas propriedades eletrônicas de nanofios semicondutores
(Universidade Federal de São Carlos, 2010-03-02) Sousa-Dias, Mariama Rebello de; Richard, Victor Lopez; https://lattes.cnpq.br/0638704940221279; https://lattes.cnpq.br/9972552337847809
The growth and characterization of semiconductor nanowires systems have attracted increasing interest due to their potential technological application, like, photo-detectors, optoelectronic devices and their promising features for quantum information processing and photonic applications. The goal of this work is the characterization of properties of semiconductor nanowires. The study was started within the framework of classical electrodynamics and this model for light-scattering was contrasted with experimental results from the photoluminescence. This classical model has been published in the literature without a concrete discussion and its application range is often not compatible with the analyzed experimental phenomenology. Thus, we have introduced quantum elements to elucidate a consistent phenomenology with the results obtained in the experiments. Through the k.p method, using in particular the Luttinger Hamiltonian, the effects of biaxial confinement and strain were analyzed in the valence band of semiconductor nanowires. This study was complemented with the description of optical properties. For the conduction band states, we were able to introduce the spin-orbit interaction since analytical results, successfully obtained from the simulation of the valence band, could be directly used in this new calculation.
Avaliação e caracterização da borracha natural de diferentes clones de seringueira cultivados nos estados de Mato Grosso e Bahia
(Universidade Federal de São Carlos, 2010-03-02) Galiani, Patrini Danielle; Mattoso, Luiz Henrique Capparelli; https://lattes.cnpq.br/5839043594908917; https://lattes.cnpq.br/5599391930270583
Natural rubber (NR) is a basic raw material used in the manufacture of a wide range of rubber goods. Usually both quality and productivity levels of Brazilian NR are lower than the imported NR. This is due to a lack of research projects which would particularly deal with the characterization and evaluation of the NR properties. For this purpose this paper summarized the study on the following items: the evaluation of both inter- and intraclonal variations; the effect of coagulation method on the NR properties; the evaluation of the coagulation method and the conditions of the bowls used for latex extraction within the NR technological properties; and the characterization of GEBs employing phosphoric acid, sulfate of hydroxylamine, and EDTA. The examination on NR was carried out through the routine analysis of such material applying DSC, TG, FTIR, GPC techniques, and also minerals analysis. In the investigation on both inter- and intraclonal influences, the results had shown statistical distinct behaviors for the NR properties of the following clones: FX 3864, GT 1, RRIM 600, PR 255 and FX 3864-PMB, including significant variations among clones and extractions. For the tire industries the essay in the PRI is the most important procedure, since it indicates an inference on the resistance to thermooxidative degradation of NR. Except for the clone PR 255, the average PRI values of all investigated clones was lower than the minimum value required by Brazilian Standard NBR 11597, and therefore it was identified a low-quality rubber of such clones. The linear regression analysis indicated that the genetic characteristics of each clone are responsible for the different results concerning the variations in environmental conditions as temperature and precipitation. The variants examined on the NR properties can be considered as the effects of factors such as climate, the origin of the clone, frequency of bleeding, soil, stimulation, seasonal, processing, and non-rubber compound, among others. In the investigation on the effect of coagulation method in the NR technological properties, the results have shown that coagulated latex samples with EDTA presented the highest PRI values for all investigated clones. Treatments with different antioxidant substances demonstrated an increase in PRI values of fresh latex samples (with no ammonia addition), for the concentrations of 0,001% and 0,01% with antioxidant substances (B and D) e (A, C, D, and A+D), in that order. In the review of the evaluation of the coagulation method and the conditions of the bowls used to extract latex from clone RRIM 600, it was verified that rubber samples obtained from the chemical coagulation had the highest PRI values and the samples from natural coagulation of the latex (it was used recycled bowls) presented PRI values lower than the standard rates required by the industries. In the findings of the characterization of the GEBs, treatments with phosphoric acid and sulfate of hydroxylamine contributed to an increase in PRI as well as a reduction in VR, respectively.
Autogestão, Economia Solidária e gênero: as trabalhadoras de cooperativas incubadas na cidade de São Carlos
(Universidade Federal de São Carlos, 2010-03-02) Pires, Aline Suelen; Lima, Jacob Carlos; https://lattes.cnpq.br/9244132532446607; https://lattes.cnpq.br/8860270341724853
Since the end of the nineteenth century, when they started to become popular, cooperatives are generating important debates. From the 70's, with the crisis of the Fordist production and the restructuring of production in the world, with the unemployment s growth and the loss of social rights linked to the formal work, the cooperativism resurfaces now, renovated as a alternative proposal of "other economy" within capitalism and as a possible overcoming. We analyzed the perception of workers in Solidarity Economy s cooperatives. We tried to see how the workers understand the meaning of self-management, how she(he) internalizes the ideas proposed by the Solidarity Economy s movement. At the same time, we decided to analyze gender relations in the cooperatives studied, which are formed mostly of women, and if the involvement with the proposal resulted in changes in daily work and home life. We investigated workers of projects of the Technological Incubator of Popular Cooperatives of the Federal University of São Carlos. The research studied three cooperatives in the city of São Carlos through the techniques of interviews and observation. The results show a gap between the actual practices and the movement s proposals, which indicates the character "under construction" of the Solidarity Economy in Brazil. Gender relations have not changed, remaining the same of the ordinary companies.