Polymer-nanoparticle composites: from orientation phenomena to optoelectronic applications

Polymer-nanoparticle hybrids show synergistic effects, demonstrating both, the unique properties of nanosized structures and the good processability and functionalities of polymeric materials. This work shows the synthesis and application of block copolymers containing a soluble, functional block and a short anchor block, which efficiently binds to the surface of nanocrystals. We functionalized anisotropic, semiconducting nanoparticles, which can be dissolved in organic and polymeric matrices upon modification. The modified nanorods have the ability to form liquid crystalline phases, which behave similar to low molecular liquid crystals with a reversible clearing behaviour. These liquid crystalline phases could also be obtained in hole conducting matrices. For a macroscopic orientation of the nanorods, electric fields were applied and a switching (in analogy to known liquid crystals) to a homeotropic orientation was observed.rnBy introduction of dye molecules in the anchor block of a hole conducting block copolymer, all essential components of a solar cell can be combined in a single particle. Light absorption of the dye induces the injection of electrons into the particles, followed by a charging, that was monitored by a special AFM technique.rnLight emitting nanocrystals were functionalized analogously with a hole transporting polymer. The stability of the particles could be enhanced by the sterically stabilizing polymer corona and the particles showed improved properties in terms of processing. We applied these hybrid materials in light emitting devices, which showed better characteristics due to an improved hole injection and well dispersed emitting particles in the active device layer.rnThe work shows the broad spectrum of properties and applications based on the synergistic effects in hybrid and composite materials.

Avalanche risk assessment - a multi-temporal approach, results from Galtür, Austria

Snow avalanches pose a threat to settlements and infrastructure in alpine environments. Due to the catastrophic events in recent years, the public is more aware of this phenomenon. Alpine settlements have always been confronted with natural hazards, but changes in land use and in dealing with avalanche hazards lead to an altering perception of this threat. In this study, a multi-temporal risk assessment is presented for three avalanche tracks in the municipality of Galtür, Austria. Changes in avalanche risk as well as changes in the risk-influencing factors (process behaviour, values at risk (buildings) and vulnerability) between 1950 and 2000 are quantified. An additional focus is put on the interconnection between these factors and their influence on the resulting risk. The avalanche processes were calculated using different simulation models (SAMOS as well as ELBA+). For each avalanche track, different scenarios were calculated according to the development of mitigation measures. The focus of the study was on a multi-temporal risk assessment; consequently the used models could be replaced with other snow avalanche models providing the same functionalities. The monetary values of buildings were estimated using the volume of the buildings and average prices per cubic meter. The changing size of the buildings over time was inferred from construction plans. The vulnerability of the buildings is understood as a degree of loss to a given element within the area affected by natural hazards. A vulnerability function for different construction types of buildings that depends on avalanche pressure was used to assess the degree of loss. No general risk trend could be determined for the studied avalanche tracks. Due to the high complexity of the variations in risk, small changes of one of several influencing factors can cause considerable differences in the resulting risk. This multi-temporal approach leads to better understanding of the today's risk by identifying the main changes and the underlying processes. Furthermore, this knowledge can be implemented in strategies for sustainable development in Alpine settlements.

Diversity of neuronal connexins in the mammalian retina

Many neurons in the mammalian retina are electrically coupled by intercellular channels or gap junctions, which are assembled from a family of proteins called connexins. Numerous studies indicate that gap junctions differ in properties such as conductance and tracer permeability. For example, A-type horizontal cell gap junctions are permeable to Lucifer Yellow, but B-type horizontal cell gap junctions are not. This suggests the two cell types express different connexins. My hypothesis is that multiple neuronal connexins are expressed in the mammalian retina in a cell type specific manner. Immunohistochemical techniques and confocal microscopy were used to localize certain connexins within well-defined neuronal circuits. The results of this study can be summarized as follows: AII amacrine cells, which receive direct input from rod bipolar cells, are well-coupled to neighboring AIIs. In addition, AII amacrine cells also form gap junctions with ON cone bipolar cells. This is a complex heterocellular network. In both rabbit and primate retina, connexin36 occurs at dendritic crossings in the AII matrix as well as between AIIs and ON cone bipolar cells. Coupling in the AII network is thought to reduce noise in the rod pathway while AII/bipolar gap junctions are required for the transmission of rod signals to ON ganglion cells. In the outer plexiform layer, connexin36 forms gap junctions between cones and between rods and cones via cone telodendria. Cone to cone coupling is thought to reduce noise and is partly color selective. Rod to cone coupling forms an alternative rod pathway thought to operate at intermediate light intensity. A-type horizontal cells in the rabbit retina are strongly coupled via massive low resistance gap junctions composed from Cx50. Coupling dramatically extends the receptive field of horizontal cells and the modulation of coupling is thought to change the strength of the feedback signal from horizontal cells to cones. Finally, there are other coupled networks, such as B-type horizontal cells and S1/S2 amacrine cells, which do not use either connexin36 or Cx50. These results confirm the hypothesis that multiple neuronal connexins are expressed in the mammalian retina and these connexins are localized to particular retinal circuits. ^

Ground truthing the Cd/Ca-carbon isotope relationship in foraminifera of the Greenland-Iceland-Norwegian Seas

In order to examine whether the paleoceanographic nutrient proxies, d13C and cadmium/calcium in foraminiferal calcite, are well coupled to nutrients in the region of North Atlantic Deep Water formation, we present da ta from two transects of the Greenland-Iceland-Norwegian Seas. Along Transect A (74.3°N, 18.3°E to 75.0°N, 12.5°W, 15 stations), we measured phosphate and Cd concentrations of modern surface sea water. Along Transect B (64.5°N, 0.7°W to 70.4°N, 18.2°W, 14 stations) we measured Cd/Ca ratios and d13C of the planktonic foraminifera Neogloboquadrina pachyderma sinistral in core top sediments. Our results indicate that Cd and phosphate both vary with surface water mass and are well correlated along Transect A. Our planktonic foraminiferal d13C data indicate similar nutrient variation with water mass along Transect B. Our Cd/Ca data hint at the same type of nutrient variability, but interpretations are hampered by low values close to the detection limit of this technique and therefore relatively large error bars. We also measured Cd and phosphate concentrations in water depth profiles at three sites along Transect A and the d13C of the benthic foraminifera Cibicidoides wuellerstorfi along Transect B. Modern sea water depth profiles along Transect A have nutrient depletions at the surface and then constant values at depths greater than 100 meters. The d13C of planktonic and benthic foraminifera from Transect B plotted versus depth also reflect surface nutrient depletion and deep nutrient enrichment as seen at Transect A, with a small difference between intermediate and deep waters. Overall we see no evidence for decoupling of Cd/Ca ratio and d13C in foraminiferal calcite from water column nutrient concentrations along these transects in a region of North Atlantic Deep Water formation.

Modelo dinámico y mejora de la recuperación de los hidrocarburos en el Reservorio "QUA IBOE ESTE" del Campo Zafiro

El petróleo en Guinea Ecuatorial como en todo el mundo, es una fuente de energía agotable, pero de mucha importancia por la infinidad de usos de sus derivados. Por eso se necesita optimizar al máximo su producción de los yacimientos. En este proyecto se pretende descubrir qué parámetros variar en el yacimiento “QUA IBOE ESTE” del Campo Zafiro (Guinea Ecuatorial), con el fin de producir más crudo del inicialmente previsto. Para ello emplearemos el método de simulación, usando las herramientas que nos ofrecen los programas de simulación de yacimientos PETREL 2011.2 y ECLIPSE 100. Después de conocer cuántos barriles de petróleo, y metros cúbico de gas recuperaríamos de más, en el apartado económico, se busca conocer el total de beneficio se obtendría. ABSTRACT Oil in Equatorial Guinea and around the world, is an exhaustible energy source, but of great importance for the myriad uses of derivatives. We therefore need to optimize reservoir production. In this project we intend to discover which parameters vary in the field "QUA IBOE ESTE" Zafiro Field (Equatorial Guinea), in order to produce more oil than estimated. To do this we use the simulation method, using the tools that we provide the reservoir simulation programs Petrel 2011.2 and ECLIPSE 100. After knowing how many barrels of oil and cubic meters of gas would recover more in the economic section, we seek to know the total benefit would be obtained.

Concrete constitutive model, calibration and applications

A methodology has been developed for characterising the mechanical behaviour of concrete, based on the damaged plasticity model, enriched with a user subroutine (V)USDFLD in order to capture better the ductility of the material under moderate confining pressures. The model has been applied in the context of the international benchmark IRIS_2012, organised by the OECD/NEA/CSNI Nuclear Energy Agency, dealing with impacts of rigid and deformable missiles against reinforced concrete targets. A slightly modified version of the concrete damaged plasticity model was used to represent the concrete. The simulation results matched very well the observations made during the actual tests. Particularly successful predictions involved the energy spent by the rigid missile in perforating the target, the crushed length of the deformable missile, the crushed and cracked areas of the concrete target, and the values of the strains recorded at a number of locations in the concrete slab.

Forward micro-inverter with primary-parallel secondary-series multicore transformer

This paper presents a primary-parallel secondary-series multicore forward micro-inverter for photovoltaic AC-module application. The proposed solution changes the number of active phases depending on the grid voltage, thus enabling the usage of low-profile unitary turns ratio transformers. Therefore, the transformers are well coupled and the overall performance of the inverter is improved. Due to the multiphase solution the number of devices increases but, the current stress and losses per device are reduced contributing to an easier thermal management. Furthermore, the decoupling capacitor is split between the phases, contributing to a low-profile solution without electrolytic capacitors suitable to be mounted in the frame of a PV module.

Desenvolvimento e otimização de antenas Vivaldi antipodais para aplicações a altas frequências.

Esta tese propõe a síntese e o estudo de uma nova técnica de cavidades de borda aplicada a antenas Vivaldi, com o intuito de melhorar suas características de diretividade. Embora as antenas do tipo Vivaldi possuam características diretivas, elas produzem radiações laterais indesejáveis, o que se reflete nos elevados índices de lóbulos laterais devido a correntes superficiais que fluem ao longo das bordas metalizadas nas laterais da antena. Estas correntes são a origem das radiações laterais que vêm sendo mitigadas pela aplicação de cavidades ressonantes, triangulares ou retangulares, que aprisionam tais correntes e, consequentemente, atenuam os lóbulos laterais, sem o incremento do lóbulo principal, uma vez que toda a energia dos lóbulos laterais é apenas confinada nos ressonadores e por isso literalmente perdida. Ao contrário desses esforços, este trabalho propõe cavidades radiantes tanto na forma de abertura exponencial, como na forma do fractais de Koch, que funcionam como radiadores auxiliares (antenas auxiliares), canalizando as correntes de borda e aproveitando-as para aumentar os níveis do lóbulo principal, mitigando os níveis de lóbulo lateral. A síntese desta nova técnica foi implementada em uma antena Vivaldi antipodal com características de baixa diretividade, como qualquer antena Vivaldi, o que foi corrigido e a aplicação da técnica de cavidades radiantes deu origem a duas novas antenas Vivaldis efetivamente diretivas. Os resultados foram obtidos através de simulações do modelo numérico no CST Microwave Studio e confirmados com medidas de laboratório, o que evidenciou a melhora das características de diretividade da antena pela aplicação da nova técnica de cavidades radiantes.

Effect of surface-perturbed intermolecular interaction on adsorption of simple gases on a graphitized carbon surface

In this paper, we investigate the effect of the solid surface on the fluid-fluid intermolecular potential energy. This modified fluid-fluid interaction energy due to the inducement of a solid surface is used in the grand canonical Monte Carlo (GCMC) simulation of various noble gases, nitrogen, and methane on graphitized thermal carbon black. This effect is such that the effective interaction potential energy between two particles close to surface is less than the potential energy if the solid substrate is not present. With this modification the GCMC simulation results agree extremely well with the experimental data over a wide range of pressures while the simulation results with the unmodified potential energy give rise to a shoulder near the neighborhood of monolayer coverage and the significant overprediction of the second and higher layer coverages. In particular the unmodified GCMC results exhibit very sharp change in those higher layers while the experimental data have a much gradual change in the uptake. We will illustrate this theory with adsorption data of argon, xenon, neon, nitrogen, and methane on graphitized thermal carbon black.

Adsorption of quadrupolar, diatomic nitrogen onto graphitized thermal carbon black and in slit-shaped carbon pores. Effects of surface mediation

In this paper, we study the effect of solid surface mediation on the intermolecular potential energy of nitrogen, and its impact on the adsorption of nitrogen on a graphitized carbon black surface and in carbon slit-shaped pores. This effect arises from the lower effective interaction potential energy between two particles close to the surface compared to the potential energy of the same two particles when they are far away from the surface. A simple equation is proposed to calculate the reduction factor and this is used in the Grand Canonical Monte Carlo (GCMC) simulation of nitrogen adsorption on graphitized thermal carbon black. With this modification, the GCMC simulation results agree extremely well with the experimental data over a wide range of pressure; the simulation results with the original potential energy (i.e. no surface mediation) give rise to a shoulder in the neighbourhood of monolayer coverage and a significant over-prediction of the second and higher layer coverages. The influence of this surface mediation on the dependence of the pore-filling pressure on the pore width is also studied. It is shown that such surface mediation has a significant effect on the pore-filling pressure. This implies that the use of the local isotherms obtained from the potential model without surface mediation could give rise to a serious error in the determination of the pore-size distribution.

Call admission control algorithms in OFDM-based wireless multiservice networks

Orthogonal frequency division multiplexing (OFDM) is becoming a fundamental technology in future generation wireless communications. Call admission control is an effective mechanism to guarantee resilient, efficient, and quality-of-service (QoS) services in wireless mobile networks. In this paper, we present several call admission control algorithms for OFDM-based wireless multiservice networks. Call connection requests are differentiated into narrow-band calls and wide-band calls. For either class of calls, the traffic process is characterized as batch arrival since each call may request multiple subcarriers to satisfy its QoS requirement. The batch size is a random variable following a probability mass function (PMF) with realistically maximum value. In addition, the service times for wide-band and narrow-band calls are different. Following this, we perform a tele-traffic queueing analysis for OFDM-based wireless multiservice networks. The formulae for the significant performance metrics call blocking probability and bandwidth utilization are developed. Numerical investigations are presented to demonstrate the interaction between key parameters and performance metrics. The performance tradeoff among different call admission control algorithms is discussed. Moreover, the analytical model has been validated by simulation. The methodology as well as the result provides an efficient tool for planning next-generation OFDM-based broadband wireless access systems.

A method for enhancing digital information displayed to computer users with visual refractive errors via spatial and spectral processing

This research pursued the conceptualization, implementation, and verification of a system that enhances digital information displayed on an LCD panel to users with visual refractive errors. The target user groups for this system are individuals who have moderate to severe visual aberrations for which conventional means of compensation, such as glasses or contact lenses, does not improve their vision. This research is based on a priori knowledge of the user's visual aberration, as measured by a wavefront analyzer. With this information it is possible to generate images that, when displayed to this user, will counteract his/her visual aberration. The method described in this dissertation advances the development of techniques for providing such compensation by integrating spatial information in the image as a means to eliminate some of the shortcomings inherent in using display devices such as monitors or LCD panels. Additionally, physiological considerations are discussed and integrated into the method for providing said compensation. In order to provide a realistic sense of the performance of the methods described, they were tested by mathematical simulation in software, as well as by using a single-lens high resolution CCD camera that models an aberrated eye, and finally with human subjects having various forms of visual aberrations. Experiments were conducted on these systems and the data collected from these experiments was evaluated using statistical analysis. The experimental results revealed that the pre-compensation method resulted in a statistically significant improvement in vision for all of the systems. Although significant, the improvement was not as large as expected for the human subject tests. Further analysis suggest that even under the controlled conditions employed for testing with human subjects, the characterization of the eye may be changing. This would require real-time monitoring of relevant variables (e.g. pupil diameter) and continuous adjustment in the pre-compensation process to yield maximum viewing enhancement.

A method for enhancing digital information displayed to computer users with visual refractive errors via spatial and spectral processing

This research pursued the conceptualization, implementation, and verification of a system that enhances digital information displayed on an LCD panel to users with visual refractive errors. The target user groups for this system are individuals who have moderate to severe visual aberrations for which conventional means of compensation, such as glasses or contact lenses, does not improve their vision. This research is based on a priori knowledge of the user's visual aberration, as measured by a wavefront analyzer. With this information it is possible to generate images that, when displayed to this user, will counteract his/her visual aberration. The method described in this dissertation advances the development of techniques for providing such compensation by integrating spatial information in the image as a means to eliminate some of the shortcomings inherent in using display devices such as monitors or LCD panels. Additionally, physiological considerations are discussed and integrated into the method for providing said compensation. In order to provide a realistic sense of the performance of the methods described, they were tested by mathematical simulation in software, as well as by using a single-lens high resolution CCD camera that models an aberrated eye, and finally with human subjects having various forms of visual aberrations. Experiments were conducted on these systems and the data collected from these experiments was evaluated using statistical analysis. The experimental results revealed that the pre-compensation method resulted in a statistically significant improvement in vision for all of the systems. Although significant, the improvement was not as large as expected for the human subject tests. Further analysis suggest that even under the controlled conditions employed for testing with human subjects, the characterization of the eye may be changing. This would require real-time monitoring of relevant variables (e.g. pupil diameter) and continuous adjustment in the pre-compensation process to yield maximum viewing enhancement.

Análise da atividade cognitiva do operador de sala de controle da produção de controle da produção de petróleo on-shore: uma abordagem da ergonomia para a gestão das restrições do sistema sociotécnico

This master's thesis aims to analyze the activity of the operators in a control room of the processes of production on-shore petroleum, with a focus on sociotechnical restrictions that interfere in the decision-making process and the actions of operators and therefore, the strategies (individual and collective) to regulate and maintain the operator action required and the safety of the system, together. The activity in focus involves the supervision and control of the production of thousands of barrels of oil/day in a complex and dispersed production’s structures built in an extension of 80 km. This operational framework highlights the importance of this activity for the fulfilment of the targets local and corporate efficiency, good management of the environment, health and safety of operators. This is an exploratory research and in the field, which uses the methodology of Ergonomic Analysis of the Work, composed of observational techniques and interactional, having as locus control room of the processes of production on-shore oil of an oil company. The population of this research is formed by operators in the control room of an Brazilian oil company. The results showed that the supervisory activity and control of the superheated steam injection is an complex context, demands greater attention, concentration, calculations, comparisons, trend analysis and decision making. The activity is collectively constructed between the control room operator, field operator and the supplier of steam. The research showed that the processes of communication and collaboration between the control room , fields and support staff are the key elements of this activity. The study shows that the operators have the autonomy and the elements necessary for work; and that there is continuous investments to improve the technology used and that the operators report sleep disturbances as a result of chronic exposure to night work. The study contributed with proposals for transformation of this activity: with regard to the installation of a area reserved for food in control room, the update the screens of the supervisory current operating condition, the periodic visits by room operators in the field, standardization of production reports, development assistance and standardization of nomenclature of controlling stations steam systems, to improve the conditions of realization of the activity, improve the quality of products produced by operators and contribute to reduce the possibility of slips or shifts in the activity.

Stability and Local Toxicity Evaluation of a Liposomal Prilocaine Formulation

This study reports a physicochemical stability evaluation of a previously reported liposomal prilocaine (PLC(LUV)) formulation (Cereda el al. J. Pharm. Pharmaceut. Sci. 7:235, 2004) before and after steam sterilization as well as its local toxicity evaluation. Prilocaine (PLC) was encapsulated into extruded unilamellar liposomes (LUVs) composed by egg phosphatidylcholine:cholesterol:alfa-tocopherol (4:3:0.07, mole %). Laser light-scattering analysis (p > 0.05) and thiobarbituric acid reaction (p > 0.05) were used to evaluate the liposomes physical (size) and chemical (oxidation) stability, respectively. The prilocaine chemical stability was followed by (1)H-nuclear magnetic resonance. These tests detected no differences on the physicochemical stability of PLC or PLCLUV, sterilized or not, up to 30 days after preparation (p > 0.05). Finally, the paw edema test and histological analysis of rat oral mucosa were used to assess the possible inflammatory effects of PLC(LUV). PLC(LUV) did not evoke rat paw edema (p > 0.05), and no significant differences were found in histological analysis, when compared to the control groups (p > 0.05). The present work shows that PLC(LUV) is stable for a 30-day period and did not induce significant inflammatory effects both in the paw edema test and in histological analysis, giving supporting evidence for its safely and possible clinical use in dentistry.