The vertebrate retina, which provides the visual input to the brain and its main interface with the outside world, is a very attractive model system for approaching the question of the information processing role of biological mechanisms of nerve cells. It is as yet impossible to provide a complete circuit diagram of the retina, but it is now possible to identify a few simple computations that the retina performs and to relate them to specific biophysical mechanisms and circuit elements. In this paper we consider three operations carried out by most retinae: amplification, temporal differentiation, and computation of the direction of motion of visual patterns.

Fischer-Tropsch synthesis is a commercial technology that allows converting synthesis gas, a mixture of CO and H2, into fuels and chemicals. This process could be one of the actors in the reduction of oil dependency of the transportation sector. In fact, it has great potential for producing synthetic fuels also from renewable sources, such as biomass, after its thermochemical conversion (gasification) into synthesis gas. Concerning the quality of a diesel fuel produced with this technology, it has a lower local environmental impact than conventional diesel, since it is practically free of sulphur and nitrogen compounds and yields lower exhaust emissions of hydrocarbons, CO and particulates. The present study focuses on the use of cobalt-based catalysts for the production of diesel. In particular, it looks upon correlation between product selectivities when varying the catalyst properties and the effect of process parameters, such as a low H2/CO ratio, typical of a biomass-derived synthesis gas, and the water partial pressure. Different cobalt-based catalysts, with different properties, such as conventional 3-dimensional porous network supports (γ-Al2O3, α-Al2O3, TiO2, SiO2), Co-loading, preparation technique, etc., were investigated in the Fischer–Tropsch reaction at industrially relevant process conditions. For a set of process conditions, a linear relationship seems to exist between the selectivity to methane (and other light products) and higher hydrocarbons (identified by the industrially relevant parameter SC5+, selectivity to hydrocarbons with more than 4 carbon atoms) indicating a common precursor. Ordered mesoporous materials (SBA-15), characterized by a 1-dimensional mesoporous network, were tested as model supports and showed the possibility of occurrence of CO-diffusion limitations at diffusion distances much shorter than those required for conventional 3-dimensional porous network supports. The linear relationship mentioned above, derived for conventional supports, was shown to be an efficient tool for indicating whether measured selectivities are affected by CO-diffusion limitations. Some of the catalysts were exposed to H2-poor syngas and to external water addition and the effects on the selectivity relationships were investigated. Furthermore, the possibility of internal water-gas shift of a H2-poor syngas with mixtures of Co/γ-Al2O3 and a Cu/ZnO/Al2O3 catalyst was investigated both as a technical solution for direct use of a model bio-syngas in the Fischer-Tropsch synthesis, and as a means to study the effect of indigenous water removal on the reaction rate to hydrocarbons. It was found that removal of indigenously produced water slows down the reaction rate significantly. Lastly, the effect of water partial pressure on the Fischer–Tropsch rate of the Co catalyst supported on narrow-pore γ-Al2O3, on its own, was studied. Inlet water partial pressure was varied by external water vapor addition at different H2/CO molar ratios ranging from 1 to 3. The effect of water showed to be positive on the rate for all the H2/CO ratios, but more significantly at H2-poor conditions. The nature of this positive effect on the rate seems to be unrelated to changes in amounts of amorphous polymeric carbon detectable by temperature-programmed hydrogenation of the spent catalyst. / <p>QC 20120914</p>

Antimicrobial peptides (AMPs) are relatively-short chain molecules that living organisms use to defend themselves against a wide range of invading microorganisms such as bacteria and viruses. They selectively bind to and kill microbes over host cells by permeabilizing cell membranes or by inhibiting the biological functions of intra-cellular components. Despite its significance in determining their cell selectivity, however, the cell-concentration dependence of AMP's membrane-perturbing activity has not been criticality examined. In this thesis, we present a physical model for cell selectivity of AMPs, especially its cell-concentration dependence. To this end, we use a coarse-grained model that captures essential molecular details such as lipid composition (e.g., fraction of anionic lipids) and peptide amphiphilicity and charge. In particular, we calculate the surface coverage of peptides in the membrane-perturbing mode as a function of peptide and cell densities: those that bind to the interface between lipid headgroups and tails. This allows us to extract the minimum inhibitory concentration (MIC) and the minimum hemolytic concentration (MHC) of the peptides. Our results show that both MIC and MHC increase as the cell density increases so that the peptide selectivity (given by MHC/MIC) decreases with increasing cell density. Our results will help resolve conflicting interpretations of peptide-selectivity experiments.

Antimicrobial peptides (AMPs) are relatively-short chain molecules that living organisms use to defend themselves against a wide range of invading microorganisms such as bacteria and viruses. They selectively bind to and kill microbes over host cells by permeabilizing cell membranes or by inhibiting the biological functions of intra-cellular components. Despite its significance in determining their cell selectivity, however, the cell-concentration dependence of AMP's membrane-perturbing activity has not been criticality examined. In this thesis, we present a physical model for cell selectivity of AMPs, especially its cell-concentration dependence. To this end, we use a coarse-grained model that captures essential molecular details such as lipid composition (e.g., fraction of anionic lipids) and peptide amphiphilicity and charge. In particular, we calculate the surface coverage of peptides in the membrane-perturbing mode as a function of peptide and cell densities: those that bind to the interface between lipid headgroups and tails. This allows us to extract the minimum inhibitory concentration (MIC) and the minimum hemolytic concentration (MHC) of the peptides. Our results show that both MIC and MHC increase as the cell density increases so that the peptide selectivity (given by MHC/MIC) decreases with increasing cell density. Our results will help resolve conflicting interpretations of peptide-selectivity experiments.

Habilitationsschrift--Düsseldorf. / Bibliography: p. [115]-124.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Thesis (Ph.D.)--Victoria University (Melbourne, Vic.), 2009.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 143-149).

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Agradecemos a compreensão. on 2016-10-18T17:50:01Z (GMT) / Submitted by MARIANA SILVEIRA BATISTA null (mariana.silveira.batista@hotmail.com) on 2016-10-24T03:16:28Z No. of bitstreams: 1 dissertação Mariana-corrigida20-07.pdf: 1588233 bytes, checksum: d5c890fad0f53efad2f96d6713b49c42 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-10-24T18:26:21Z (GMT) No. of bitstreams: 1 batista_ms_me_ilha.pdf: 1588233 bytes, checksum: d5c890fad0f53efad2f96d6713b49c42 (MD5) / Made available in DSpace on 2016-10-24T18:26:21Z (GMT). No. of bitstreams: 1 batista_ms_me_ilha.pdf: 1588233 bytes, checksum: d5c890fad0f53efad2f96d6713b49c42 (MD5) Previous issue date: 2016-03-30 / A planta daninha está entre as espécies de maior importância nos campos de diversas culturas. Por se tratar de uma espécie que apresenta alto poder de produzir milhares de sementes que tem se adaptado ao uso de herbicidas, seu estudo se torna de grande importância para amenizar os danos causados às culturas. O trabalho foi desenvolvido com o objetivo de estudar as características morfofisiológicas da espécie Conyza canadensis (L.) Cronquist quanto à resistência ao herbicida do grupo químico das glicinas substituídas em plantas com histórico de resistência. O experimento foi instalado e conduzido durante o segundo semestre de 2014 em condição de campo na área da Universidade Federal do Mato Grosso do Sul – Campus Chapadão do Sul. O delineamento experimental foi blocos casualizados, com 4 repetições, os tratamentos em esquema fatorial 5x5, totalizando 25 tratamentos. O fator A correspondeu ao estádio de desenvolvimento: Tamanho I – plantas com 5 cm de altura; Tamanho II - 10 cm de altura; Tamanho III – 15 cm de altura; Tamanho IV – 20 cm de altura; Tamanho V – 25 cm de altura. O fator B foram as doses do glyphosate: Dose I (sem aplicação) - Testemunha; Dose II (1200 g i.a ha-1); Dose III (2400 g i.a ha-1); Dose IV (3600 g i.a ha-1) e Dose V (4800 g i.a ha-1). Foram realizadas análises de crescimento das plantas: altura de plantas e diâmetro do caule, aos 0, 14 e 28 dias após a aplicação dos tratamentos e uma avaliação de altura de plantas remanescentes ou rebrota realizada aos 100 dias após a aplicação. Para a análise de perdas de transpiração de folhas destacadas e hidratadas as plantas estavam em fase vegetativa e coletadas no terço-médio das plantas aos 0, 4 e 8 DAA. Os dados foram submetidos à análise de variância e as medias dos tratamentos comparadas pelo Teste de Scott Knott a 5% de probabilidade. Concluiu-se que tanto o tamanho das plantas como as doses do glyphosate influenciaram na altura de plantas, no diâmetro da haste e nas perdas de transpiração da espécie Conyza canadensis (L.) Cronquist. A porcentagem de redução da altura das plantas de tamanho menor foi maior conforme as doses de glyphosate aumentaram em todos os períodos das avaliações. Plantas de tamanho menor transpiram mais do que plantas de tamanho maior sem a aplicação de herbicida. Para as perdas de transpiração, as plantas de menor tamanho que receberam a aplicação do glyphosate em doses maiores, transpiraram menos. As plantas de tamanhos maiores transpiraram mais quando submetidas a doses medianas do glyphosate quando comparadas as doses maiores. / The weed is among the species of greatest importance in the fields of different cultures. Because it is a species that has a high power to produce thousands of seeds that have adapted to the use of herbicides, their study becomes very important to mitigate the damage to crops. The work was to study the morphological and physiological characteristics of species Conyza canadensis (L.) Cronquist for resistance to the herbicide chemical group of glycines substituted in plants with a history of resistance. The experiment was installed and conducted during the second half of 2014 under field conditions at the Universidade Federal do Mato Grosso do Sul-Campus Chapadão do Sul. The experimental design was blocks randomized with four repetitions, the treatments in a factorial 5x5, totaling 25 treatments. The factor A corresponded to the stage of development: Size I - plants with 5 cm; Size II - 10 cm; Size III - 15 cm; Size IV - 20 cm; Size V - 25 cm. The factor B were the glyphosate doses: Dose I (without application) - witness; Dose II (1200 g a.i. ha-1); Dose III (2400 g a.i. ha-1); Dose IV (3600 g a.i. ha-1) and Dose V (4800 g a.i ha-1). Plant growth analysis were performed: plant height and stem diameter at 0, 14 and 28 days after application of treatments and an assessment height of remaining plants or regrowth held at 100 days after application. For the analysis of transpiration losses highlighted and hydrated leaves the plants were in vegetative stage and collected the third-medium plants at 0, 4:08 DAA. The data were submitted to analysis of variance and the averages of the treatments compared by Scott Knott test at 5% probability. It was concluded that both the size of the plants as glyphosate doses influence on plant height, stem diameter and the losses in perspiration of species Conyza canadensis (L.) Cronquist. The percentage reduction of the height of the smaller plants was higher as the glyphosate rates increased in all periods of evaluations. smaller plants transpire more than plants of large size without the application of herbicide. For transpiration losses, smaller plants that received the application of glyphosate in larger doses, transpired less. The larger size plants transpired more when subjected to glyphosate median doses when compared to higher doses.

Orientador: Fernando Tadeu de Carvalho / Resumo: A planta daninha está entre as espécies de maior importância nos campos de diversas culturas. Por se tratar de uma espécie que apresenta alto poder de produzir milhares de sementes que tem se adaptado ao uso de herbicidas, seu estudo se torna de grande importância para amenizar os danos causados às culturas. O trabalho foi desenvolvido com o objetivo de estudar as características morfofisiológicas da espécie Conyza canadensis (L.) Cronquist quanto à resistência ao herbicida do grupo químico das glicinas substituídas em plantas com histórico de resistência. O experimento foi instalado e conduzido durante o segundo semestre de 2014 em condição de campo na área da Universidade Federal do Mato Grosso do Sul – Campus Chapadão do Sul. O delineamento experimental foi blocos casualizados, com 4 repetições, os tratamentos em esquema fatorial 5x5, totalizando 25 tratamentos. O fator A correspondeu ao estádio de desenvolvimento: Tamanho I – plantas com 5 cm de altura; Tamanho II - 10 cm de altura; Tamanho III – 15 cm de altura; Tamanho IV – 20 cm de altura; Tamanho V – 25 cm de altura. O fator B foram as doses do glyphosate: Dose I (sem aplicação) - Testemunha; Dose II (1200 g i.a ha-1); Dose III (2400 g i.a ha-1); Dose IV (3600 g i.a ha-1) e Dose V (4800 g i.a ha-1). Foram realizadas análises de crescimento das plantas: altura de plantas e diâmetro do caule, aos 0, 14 e 28 dias após a aplicação dos tratamentos e uma avaliação de altura de plantas remanescentes ou rebrota realizada aos ... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre