Biolixivia??o de sulfetos secund?rios de cobre por micro?organismos mes?filos em diferentes reatores agitados.

Programa de P?s-Gradua??o em Engenharia de Materiais. Departamento de Engenharia Metal?rgica, Escola de Minas, Universidade Federal de Ouro Preto.A biolixivia??o de cobre a partir de sulfetos secund?rios, tais como a calcocita e a bornita, ? amplamente aplicada industrialmente em v?rios pa?ses do mundo. Isso ocorre porque esses sulfetos s?o facilmente oxidados pelo ?on Fe3+ produzido por microorganismos de biolixivia??o. No entanto, a biolixivia??o pode ser severamente impactada se o min?rio portar impurezas sol?veis que podem afetar o crescimento bacteriano. Este ? o caso do fluoreto, que existe como HF nas condi??es ?cidas aplicadas na biolixivia??o de metais b?sicos. Este ?ltimo pode atravessar membranas celulares e dissociar dentro da c?lula (por causa de seu pH neutro), reduzindo o crescimento bacteriano. Nesta disserta??o foi investigada a influ?ncia da concentra??o de fl?or sobre o crescimento de Acidithiobacillus ferrooxidans e revelou que 20 mg.L?1 F?total inibiram a biooxida??o do ?on Fe2+. Tal inibi??o foi superada por adi??o de sulfato de alum?nio ao meio de crescimento. Em seguida, foi estudada a biolixivia??o de um min?rio de cobre secund?rio portador de fl?or (contendo calcocita e bornita) pela cultura mes?fila. Os efeitos do pH bem como as concentra??es de Fe2+, Al3+ e Mg2+ na extra??o de cobre foram determinados, os experimentos foram realizados em frascos Erlenmeyer (250 mL) contendo 100 mL de solu??o e porcentagem de s?lidos a 5% (p/v) agitada a 150 min?1. A cin?tica de lixivia??o da amostra foi ligeiramente afetada pelo pH e concentra??es do ?on Fe2+, sendo que as maiores extra??es de cobre foram observadas para pH 1,6?1,8 e 5?10 g.L?1 Fe2+. As concentra??es de alum?nio (at? 5 g.L?1) melhoraram a cin?tica de extra??o do cobre ? medida que os ?ons fluoreto foram complexados pelo elemento e a extra??o final de cobre atingiu 75%. Al?m disso, propondo uma adapta??o ao programa de ensaios metal?rgicos visando uma futura aplica??o industrial de lixivia??o em pilhas, especificamente em sistemas agitados, a segunda parte da disserta??o buscou comparar o perfil de lixivia??o de tr?s diferentes reatores (frascos Erlenmeyer, garrafas rotativas e um biorreator agitado mecanicamente) durante a biolixivia??o de duas amostras de sulfetos secund?rios com diferentes teores de cobre e fl?or. Na aus?ncia de uma fonte externa de alum?nio, os ensaios em Erlenmeyer n?o mostraram qualquer aumento no potencial da solu??o, independentemente da amostra de min?rio estudada. Concentra??es de fl?or e alum?nio em torno de 300 mg.L?1 foram registradas neste reator e a raz?o Al/F em torno de 1 explicou o baixo potencial registrado. Por outro lado, nos ensaios em garrafa e biorreator, a amostra de min?rio com menor teor de cobre produziu alum?nio (530 mg.L?1) acima das concentra??es de fl?or (380 mg.L?1), de modo que esse maior ?ndice Al/F estimulou o crescimento bacteriano. Isto se justificou, pelo fato do potencial da solu??o ter atingido valores acima de 600 mV ao final do experimento, o que indicou o crescimento bacteriano nesses reatores. Quando o alum?nio foi adicionado ao meio de crescimento, o potencial da solu??o aumentou exponencialmente, indicando boa atividade de biolixivia??o e at? 97% de extra??o de cobre foi observada nos tr?s reatores, mas as garrafas rotativas apresentaram uma cin?tica de lixivia??o mais r?pida devido a altas popula??es bacterianas (> 108 c?lulas. mL?1) proporcionada por uma melhor aera??o da solu??o (6 mg.L?1 como a concentra??o de oxig?nio dissolvido).Copper bioleaching from secondary sulphides such as chalcocite and bornite is widely applied industrially in several countries worldwide. This is because these sulphides are easily oxidized by the ferric iron produced by bioleaching microorganisms. Notwithstanding, bioleaching can be severely hampered if the ore contains soluble impurities which can affect bacterial growth. This is the case of fluoride, which exists as HF in the acid conditions applied in the bioleaching of base metals. The latter can cross cell membranes and dissociate inside the cell (because of its neutral pH) reducing the bacterial growth. The current dissertation investigated initially the fluoride concentration which impaired the growth of At. ferrooxidans and revealed that 20 mg.L? 1 Ftot inhibited ferrous iron bio?oxidation. Such inhibition was overcome by aluminium sulphate supplementation to the growth medium. Subsequently the bioleaching of a fluoride?bearing secondary copper ore (containing chalcocite and bornite) by the mesophile culture was studied. The effects of pH as well as the concentrations of Fe2+, Al3+ and Mg2+ on copper extraction were determined in experiments were performed in Erlenmeyer flasks (250 mL) containing 100 mL of a 5% (w/v) pulp stirred at 150 min?1. The leaching kinetics of the sample was slightly affected by both pH and ferrous iron concentrations and the largest copper extractions were observed for pH 1.6?1.8 and 5? 10 g.L?1 Fe2+. Aluminium concentrations (up to 5 g.L?1) improved the copper extraction kinetics as fluoride ions were complexed by the element and the final copper extraction reached 75%. In addition, the metallurgical testwork proposed in feasibility studies for leaching projects comprise different type of reactor experiments such as rolling bottles whereas shaking flasks tests are of widespread use in academic research. Therefore the second part of the current dissertation sought to compare the leaching profile of three different reactors (Erlenmeyer flasks, rolling bottles and a mechanically stirred bioreactor) during bioleaching of two samples of the secondary sulphide ore with different copper and fluoride content. In the absence of an external aluminium source, the shaking flask experiments did not show any increase in the solution potential, regardless of the ore sample studied. Fluoride and aluminium concentrations around 300 mg.L?1 were recorded in this reactor and the Al/F ratio around 1 explained the low potential recorded. Conversely, the ore sample with the lower fluoride content produced aluminium (530 mg.L?1) above fluoride (380 mg.L?1) concentrations so that such higher Al/F ratio fostered bacterial growth. This justified the solution potential attaining values above 600 mV by the end of the experiment, which indicated bacterial growth in that reactor. When aluminium was added to the growth medium the solution potential increases exponentially indicating good bioleaching activity and up to 97% copper extraction was observed in the three reactors, but the rolling bottles depicted a faster leaching kinetics due to high bacterial populations (>108 cells.mL?1) provided by a better aeration of the solution (6 mg.L?1 as the dissolved oxygen concentration)

Metallic brackets bonded with resin-reinforced glass lonomer cements under different enamel conditions

Objective: To assess the shear bond strength of metallic orthodontic brackets bonded with either Fuji Ortho or Ortho Glass LC resin-reinforced glass ionomer cements to enamel surfaces under different conditions, namely, enamel without etching, enamel conditioned with 37% phosphoric acid and enamel conditioned with Transbond Plus Self Etching Primer (TPSEP). Materials and Methods: One hundred and five bovine inferior incisors were divided into seven groups (n = 15). In group 1 (control) Transbond XT was used according to the manufacturer's recommendations. In groups 2, 3, and 4 all using Fuji Ortho LC, the brackets were bonded, respectively, to enamel nonetched, enamel etched with 37% phosphoric acid, and enamel etched with TPSEP. In groups 5, 6, and 7, the bonding was performed using Ortho Glass LC under the same enamel conditions observed in the other experimental groups. After 24 hours, shear bond strength tests were performed for all samples at a crosshead speed of 0.5 mm/min. Results: The results (MPa) showed no statistically significant difference between groups 1, 3, and 4 (P >.05). However, such groups were statistically superior to the others (P .05). Group 5 showed the lowest shear strength value, which was also statistically inferior to the other groups (P <.05). Conclusions: Regardless of the enamel treatment, Fuji Ortho LC yielded shear strength values superior to those from Ortho Glass LC.76470070

Natural selection in common bean microsatellite alleles and identification of QTLs for grain yield

Natural selection acts to select better adapted individuals or alleles in segregating population and help plant breeding. The objective of this work was to verify the effect of natural selection on microsatellite alleles as indicators of better adaptation and identification of quantitative trait loci (QTLs) for grain yield. This study evaluated 107 progenies from the F8 and 107 from the F24 generation derived from crossing Carioca MG and ESAL 686 lines, carried out by the bulk method, and evaluated in three different seasons: winter 2001; rainy 2001 and dry 2002. It was utilized 22 polymorphic markers and the natural selection acted in all of them. The frequency of the alleles of the parent Carioca MG, the most adapted, was increased in all of the 22 loci in F8 and 19 loci in F24. Selection affected each locus with different intensities in different generations. All of the selected alleles can be important for breeding program. QTLs were identified in generation F8 and F24 at varied magnitudes. The best marker PVttc002 explained 11.76% of variation in grain yield. However, an elevated interaction between QTLs and the environments was observed, showing the great difficulty in assisted selection

Cost-effective external interference for promoting the evolution of cooperation.

The problem of promoting the evolution of cooperative behaviour within populations of self-regarding individuals has been intensively investigated across diverse fields of behavioural, social and computational sciences. In most studies, cooperation is assumed to emerge from the combined actions of participating individuals within the populations, without taking into account the possibility of external interference and how it can be performed in a cost-efficient way. Here, we bridge this gap by studying a cost-efficient interference model based on evolutionary game theory, where an exogenous decision-maker aims to ensure high levels of cooperation from a population of individuals playing the one-shot Prisoner's Dilemma, at a minimal cost. We derive analytical conditions for which an interference scheme or strategy can guarantee a given level of cooperation while at the same time minimising the total cost of investment (for rewarding cooperative behaviours), and show that the results are highly sensitive to the intensity of selection by interference. Interestingly, we show that a simple class of interference that makes investment decisions based on the population composition can lead to significantly more cost-efficient outcomes than standard institutional incentive strategies, especially in the case of weak selection.</p

ENERGY POTENTIAL OF SPECIES FROM FOREST MANAGEMENT PLAN FOR THE RIO GRANDE DO NORTE STATE

The objective was to evaluate the energy potential of woods of species under forest management plan from Serid\uf3 region in the Rio Grande do Norte state. It was used the wood species Jurema Preta, Pereiro, Marmeleiro, Catingueira, Moror\uf3, Imburana, Jurema Branca and Mofumbo, at 20 years old, originated from the Dominga's farm in the Caic\uf3/RN municipality. The density, the content of volatiles, the ash and fixed carbon, calorific value, elemental composition and carbon/nitrogen (C/N) and carbon/ hydrogen (C/H) analysis were carried out in the wood. Additionally, the amount of energy produced in kW.h.m-3 and kW.h.ha-1 for all species was estimated. The experiment was conducted in a completely randomized design with eight treatments (species), four replicates (sample trees), adding up to 32 sampling units. There were significant differences, at 5 % significance between treatments for all variables, except for hydrogen percentage and C/H ratio. It was concluded that Moror\uf3's wood shows high energy potential, and along with Jurema Preta, presents higher energy generation per m3, and provides greater economy for the same productivity. The energy potential Jurema Preta wood's stands out among the species. Pereiro's wood stands for energy production per hectare. Marmeleiro and Jurema Branca's woods are indicated as direct burning potential and Imburana's wood is not recommended for power generation.O objetivo do trabalho foi avaliar o potencial energ\ue9tico das madeiras de esp\ue9cies sob plano de manejo florestal provenientes da regi\ue3o do Serid\uf3, no estado do Rio Grande do Norte. Utilizou-se na pesquisa, madeiras das esp\ue9cies Jurema-preta, Pereiro, Marmeleiro, Catingueira, Moror\uf3, Imburana, Jurema-branca e Mofumbo, aos 20 anos de idade, originadas da fazenda Dominga no munic\uedpio de Caic\uf3/RN. Foram realizadas na madeira, as an\ue1lises da densidade b\ue1sica, teores de materiais vol\ue1teis, cinzas e carbono fixo, poder calor\uedfico superior, composi\ue7\ue3o qu\uedmica elementar e rela\ue7\uf5es carbono/nitrog\ueanio (C/N) e carbono/ hidrog\ueanio (C/H). Adicionalmente, estimou-se a quantidade de energia produzida em kW.h.m-3 e em kW.h.ha-1 para todas as esp\ue9cies. O experimento foi realizado segundo um delineamento inteiramente casualizado com oito tratamentos (esp\ue9cies), quatro repeti\ue7\uf5es (\ue1rvores\u2013amostra), totalizando 32 unidades amostrais. Houve diferen\ue7a significativa, a 5 % de signific\ue2ncia, entre os tratamentos para todas as vari\ue1veis analisadas, exceto para a porcentagem de hidrog\ueanio e rela\ue7\ue3o C/H. Conclui-se que a madeira de Moror\uf3 apresenta alto potencial energ\ue9tico, e juntamente com a Jurema-preta, maior gera\ue7\ue3o de energia por m3, al\ue9m de proporcionar maior economia para uma mesma produtividade. O potencial energ\ue9tico da madeira de Jurema-preta se destaca entre as esp\ue9cies estudadas. A madeira de Pereiro se destaca na produ\ue7\ue3o de energia por hectare. As madeiras de Jurema-branca e Marmeleiro s\ue3o indicadas como potenciais para queima direta. A madeira de Imburana n\ue3o \ue9 recomendada para a gera\ue7\ue3o de energia

EFFECT OF PROPERTIES CHEMICAL AND SIRINGIL/GUAIACIL RELATION WOOD CLONES OF EUCALYPTUS IN THE PRODUCTION OF CHARCOAL

O trabalho teve como objetivo determinar a influ\ueancia das propriedades qu\uedmicas (composi\ue7\ue3o elementar, teores de extrativos totais, lignina total e holocelulose) e rela\ue7\ue3o siringil/guaiacil, da madeira de diferentes materiais gen\ue9ticos de eucalipto na produ\ue7\ue3o de carv\ue3o vegetal. Utilizaram-se na pesquisa quatro clones h\uedbridos de Eucalyptus , aos 7 anos de idade, sendo 6 \ue1rvores por clone, totalizando 24 unidades amostrais. Houve diferen\ue7a significativa, a 5% de signific\ue2ncia, entre os tratamentos para a composi\ue7\ue3o elementar, teores de extrativos totais, lignina total e holocelulose e rela\ue7\ue3o siringil/guaiacil da madeira, como tamb\ue9m, para os rendimentos gravim\ue9tricos em carv\ue3o vegetal, em gases condens\ue1veis e em gases n\ue3o condens\ue1veis, teores de carbono fixo e de materiais vol\ue1teis e para o poder calor\uedfico superior do carv\ue3o vegetal. Para o teor de cinzas e densidade relativa aparente do carv\ue3o n\ue3o foram observadas diferen\ue7as significativas ao mesmo n\uedvel de signific\ue2ncia. Concluiu-se que existe variabilidade na qualidade da madeira dos quatro materiais gen\ue9ticos avaliados, tendo, os mesmos, correla\ue7\uf5es distintas, tanto no rendimento quanto na qualidade do carv\ue3o vegetal. Todos os materiais gen\ue9ticos apresentaram, de modo satisfat\uf3rio, rendimento gravim\ue9trico em carv\ue3o vegetal e qualidade. As madeiras dos clones com baixa rela\ue7\ue3o siringil/guaiacil apresentaram aumento no rendimento em carv\ue3o vegetal. A composi\ue7\ue3o qu\uedmica das madeiras dos quatro clones, de modo geral, n\ue3o apresentou correla\ue7\uf5es significativas, a 5% de signific\ue2ncia, no rendimento e qualidade do carv\ue3o.The objective of this study was to determine the influence of the chemical properties (elemental composition, levels of extractives, lignin total and holocellulose) and the syringyl/guaiacyl, wood of different Eucalyptus genetic materials in the production of charcoal. It was used in the study four hybrid clones, at age of 7 years, 6 trees per clone, totaling 24 sampling units. There was significant difference, at 5% significance, between treatments for elemental composition, levels of extractives, lignin total and holocellulose and the wood syringyl/guaiacyl, as well as for gravimetric yields in charcoal, condensable gases and non-condensable gases, levels of fixed carbon and volatiles, and for the higher calorific value of charcoal. For the ash content and relative apparent density of charcoal were not observed significant differences at the same level of significance. Concluded that there is variability in the wood quality of four evaluated genetic materials, having the same, distinct correlations, thus the yield and the quality of charcoal. All genetic material presented satisfactorily gravimetric yield in charcoal and quality. The woods of clones with low syringyl/guaiacyl ratio showed an increase in yield in charcoal. The chemical composition of woods from the four clones, in general, showed no significant correlations, the 5% significance level, at the yield and quality of charcoal