Brain-machine interfaces (BMIs) hold promise for restoring motor functions in severely paralyzed individuals. Invasive BMIs are capable of recording signals from individual neurons and typically provide the highest signal-to-noise ratio. Despite many efforts in the scientific community, BMI technology is still not reliable enough for widespread clinical application. The most prominent challenges include biocompatibility, stability, longevity, and lack of good models for informed signal processing and BMI comparison. To address the problem of low signal quality of chronic probes, in the first part of the thesis one such design, the Neurotrophic Electrode, was modified by increasing its channel capacity to form a Neurotrophic Array (NA). Specifically, single wires were replaced with stereotrodes and the total number of recording wires was increased. This new array design was tested in a rhesus macaque performing a delayed saccade task. The NA recorded little single unit spiking activity, and its local field potentials (LFPs) correlated with presented visual stimuli and saccade locations better than did extracted spikes. The second part of the thesis compares the NA to the Utah Array (UA), the only other micro-array approved for chronic implantation in a human brain. The UA recorded significantly more spiking units, which had larger amplitudes than NA spikes. This was likely due to differences in the array geometry and construction. LFPs on the NA electrodes were more correlated with each other than those on the UA. These correlations negatively impacted the NA's information capacity when considering more than one recording site. The final part of this dissertation applies information theory to develop objective measures of BMI performance. Currently, decoder information transfer rate (ITR) is the most popular BMI information performance metric. However, it is limited by the selected decoding algorithm and does not represent the full task information embedded in the recorded neural signal. A review of existing methods to estimate ITR is presented, and these methods are interpreted within a BMI context. A novel Gaussian mixture Monte Carlo method is developed to produce good ITR estimates with a low number of trials and high number of dimensions, as is typical for BMI applications.

The transfer of sparingly soluble gases across the air-water interface has significant effects on the distribution of the constituents in aquatic ecosystems. Gas-liquid transfer rate determines the flux of the sparingly soluble gases driven by the concentration difference. Considerable stream-driven gas-liquid transfer rate formulae have been developed. They have reasonable predictions in one-dimensional uniform flows. However, their applications in more complex cases such as three-dimensional flows are problematic. Furthermore, the wind effects are not incorporated into these formulae. New models need to be developed for gas-liquid transfer rate in three-dimensional flows that incorporate the effects of both wind and streamflow. In this study, first, a model of gas-liquid transfer rate in non-isotropic turbulent flows is developed. Second, a general stream-driven gas-liquid transfer rate model is developed for the normal ranges of water depth and flow velocity in natural rivers. Third, a wind-stream-driven gas-liquid transfer rate model is developed. Fourth, a model of surface renewal rate caused by turbulence from transition location of shear flows is developed. Fifth, a gas-liquid transfer rate model for wind and dynamic three-dimensional flow systems is developed. A computer program is coded and applied to various cases from simple one-dimensional uniform flow systems to complex wind and dynamic three-dimensional flow systems. A specific model can be selected from the series models for a specific application based on the application requirements and the acceptable computation complexity.

A microbubble dispersion (MBD) was used to supply oxygen for an aerobic fermentation of Baker's yeast. The 1-liter microbubble dispersion generator supplied bubbles for 20-liter and 50-liter working volume fermentations in a 72-liter pilot scale fermenter. The microbubbles were stabilized by the surfactants naturally present in the culturing broth medium. The growth patterns of yeast Saccharomyces cerevisiae, cultured at agitation speeds of 150 rpm and 500 rpm, were compared for oxygen supplied by ordinary air sparging and by MBD sparging. Both air sparged and MBD systems were supplied air at equivalent volumetric flow rates. The volumetric oxygen transfer coefficients (KLa) were estimated by the yield coefficient method. The KLa values increased from 142.5 to 458.3 h-1 and from 136.1 to 473.3 h-1 for 20- and 50- liter runs, respectively, as the agitation speed was increased from 150 to 500 rpm in the ordinary air sparged fermentations. The oxygen transfer coefficients in the MBD sparged fermentations were found to be independent of the fermenter agitation speed at approximately 480 h-1 for 20-liter runs and 340 h-1 for 50-liter runs. The growth rates for MBD at 150 rpm were essentially equivalent with air sparged fermentations at 500 rpm. The total power consumption per unit volume of broth for the 150 rpm, MBD fermentation was 68% lower than the 500 rpm, air sparged run for the 20-liter fermentations and was 55% lower for the 50-liter fermentations. / Master of Science

Animal cells are often cultured in stirred tank reactors. Having no cell wall, these animal cells are very sensitive to the fluid mechanical stresses that result from agitation by the impeller and from the rising and bursting of bubbles, which are generated within the culture medium in the stirred tank to supply oxygen by mass transfer to the cells. If excessive, these fluid mechanical stresses can result in damage/death of animal cells. Stress due to the rising and bursting of bubbles can be avoided by using a gas-permeable membrane, in the form of a long coiled tube (with air passing through it) within the stirred tank, instead of air-bubbles to oxygenate the culture medium. Fluid mechanical stress due to impeller agitation can be controlled using appropriate impeller rotational speeds. The aim of this study was to lay the foundations for future work in which a correlation would be developed between cell damage/death and the fluid mechanical stresses that result from impeller agitation and bubbling. Such a correlation could be used to design stirred-tank reactors at any scale and to determine appropriate operating conditions that minimise cell damage/death due to fluid mechanical stresses. Firstly, a validated CFD model of a baffled tank stirred with a Rushton turbine was developed to allow fluid mechanical stresses due to impeller agitation to be estimated. In these simulations, special attention was paid to the turbulence energy dissipation rate, which has been closely linked to cell damage/death in the literature. Different turbulence models, including the k-ε, SST, SSG-RSM and the SAS-SST models, were investigated. All the turbulence models tested predicted the mean axial and tangential velocities reasonably well, but under-predicted the decay of mean radial velocity away from the impeller. The k-ε model predicted poorly the generation and dissipation of turbulence in the vicinity of the impeller. This contrasts with the SST model, which properly predicted the appearance of maxima in the turbulence kinetic energy and turbulence energy dissipation rate just off the impeller blades. Curvature correction improved the SST model by allowing a more accurate prediction of the magnitude and location of these maxima. However, neither the k-ε nor the SST models were able to properly capture the chaotic and three-dimensional nature of the trailing vortices that form downstream of the blades of the impeller. In this sense, the SAS-SST model produced more physical predictions. However,this model has some drawbacks for modelling stirred tanks, such as the large number of modelled revolutions required to obtain good statistical averaging for calculating turbulence quantities. Taking into consideration both accuracy and solution time, the SSG-RSM model was the least satisfactory model tested for predicting turbulent flow in a baffled stirred tank with a Rushton turbine. In the second part of the work, experiments to determine suitable oxygen transfer rates for culturing cells were carried out in a stirred tank oxygenated using either a sparger to bubble air through the culture medium or a gas-permeable membrane. Results showed that the oxygen transfer rates for both methods of oxygenation were always above the minimum oxygen requirements for culturing animal cells commonly produced in industry, although the oxygen transfer rate for air-bubbling was at-least 10 times higher compared with using a gas-permeable membrane. These results pave the way for future experiments, in which animal cells would be cultured in the stirred tank using bubbling and (separately) a gas-permeable membrane for oxygenation so that the effect of rising and bursting bubbles on cell damage/death rates can be quantified. The effect of impeller agitation on cell damage/death would be quantified by using the gas permeable membrane for oxygenation (to remove the detrimental effects of bubbling), and changing the impeller speed to observe the effect of agitation intensity. In the third and final part of this work, the turbulent flow in the stirred tank used in the oxygenation experiments was simulated using CFD. The SST turbulence model with curvature correction was used in these simulations, since it was found to be the most accurate model for predicting turbulence energy dissipation rate in a stirred tank. The predicted local maximum turbulence energy dissipation rate of 8.9x10¹ m2/s3 at a rotational speed of 900 rpm was found to be substantially less than the value of 1.98x10⁵ m2/s3 quoted in the literature as a critical value above which cell damage/death becomes significant. However, the critical value for the turbulence energy dissipation rate quoted in the literature was determined in a single-pass flow device, whereas animal cells in a stirred tank experience frequent exposure to high turbulence energy dissipation rates (in the vicinity of the impeller) due to circulation within the stirred tank and long culture times. Future cell-culturing experiments carried out in the stirred tank of this work would aim to determine a more appropriate critical value for the turbulence energy dissipation rate in a stirred tank, above which cell damage/death becomes a problem.

Baigiamajame magistro darbe nagrinėjami su duomenų perdavimo sparta susiję ryšio kanalo parametrai. Pirmojoje darbo dalyje apžvelgiami užsienio ir Lietuvos mokslininkų atliekami tyrimai kanalo parametrų, susietų su duomenų perdavimo sparta, tematika, analizuojama mobilaus tinklo kanalo parametrų matavimams skirta iranga. Kituose darbo skyriuose išskiriami konkretūs su duomenų pralaidumu sąveikaujantys parametrai. Naudojant šiuos parametrus darbe kuriami modeliai, skirti duomenų perdavimo spartai prognozuoti tikrinamas modelių tinkamumas bei tikslumas. Tiesinės prognozės atveju pasiektas 77,83%, o netiesinės prognozės atveju – 76,19% tikėtinos duomenų perdavimo spartos prognozės tikslumas. Atsižvelgiant į vartotojų interesus siūlomi jų įrangai pritaikyti prognozės modeliai. Darbo pabaigoje tikrinamas sukurtų modelių adekvatumas realiomis ryšio salygomis. / This work analyzes communication channel settings of UMTS technology which are related with a data transfer throughput. Further course of study includes the most specific parameters selection, that arethe most crucial for data speed. Using these parameters it is developed the models suitable for data transfer throughput prediction. To build the model the linear and nonlinear forecasting methods are applied. The linear prediction is made by using linear regression, nonlinear – neural networks. Using linear prediction model 77.83% forecast accuracy has been achieved, while the nonlinear forecast expected transmission rate forecast accuracy is 76.19%.These prediction models accuracy obtained by using eight parameters of the communication channel. Finally in this paper are built the data throughput prediction models that allow to predict data speed using only standard terminal presented channel parameters. At the end all built prediction models are checked in real communication environment.

This work deals with accessible communications technologies and their possible usage in firms. It is necessary to have a survey about types and trends of communications technologies at proposal of communications network. It is important to choose the combination that is suitable with its reliability, achievement and price.

Optimising illumination is essential for optimising the growth of phototrophic cells and their production of desired metabolites and/or biomass. This requires appropriate modulation of light and other key inputs and continuous online monitoring of their metabolic activities. Powerful non-invasive systems for cultivating heterotrophic organisms include shake flasks in online monitoring units, but they are rarely used for phototrophs because they lack the appropriate illumination design and necessary illuminatory power. This study presents the design and characterisation of a photosynthetic shake flask unit, illuminated from below by warm white light-emitting diodes with variable light intensities up to 2300 μmol m-2 s-1. The photosynthetic unit was successfully used, in combination with online monitoring of oxygen production, to cultivate Arthrospira platensis. In phototrophic growth under continuous light and a 16 h light/8 h dark cycle (light intensity: 180 μmol m-2 s-1), the oxygen transfer rate and biomass-related oxygen production were - 1.5 mmol L-1 h-1 and 0.18 mmol O2 gx-1 h-1, respectively. The maximum specific growth rate was 0.058 h-1, during the exponential growth phase, after which the biomass concentration reached 0.75 g L-1.

A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.

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No. of bitstreams: 1 VictorRLO_DISSERT.pdf: 1864412 bytes, checksum: 5110310795a99006bc86a9720eaeb5a4 (MD5) Previous issue date: 2017-05-11 / The development of biodegradable coatings has been potentially discussed due to the exacerbated use of petrochemical polymers, and their non-biodegradable load has been aggravating serious environmental problems. Furthermore the growing worldwide demand for health improvement has reached an interest in technological solutions capable of offering means of conservation and reduction of the metabolic activity of fruits and vegetables to preserve their numerous nutrients effectively for long periods of storage. Biopolymers, which are the polymeric base of the coating, add several positive points: they are attractive for their renewable characteristics, abundance, low cost and easy access in the semi-arid region. The coatings were synthesized by the casting method with three polymer bases: corn starch (3%), cassava starch (2%) and gelatin (5%); beeswax was added as a hydrophobic agent in the polymeric network at different concentrations relative to the dry biopolymer base (0%, 5% and 10%). The effect of the incorporation of the beeswax on the barrier properties was evaluated and the biofilm was determined with the best characteristics for coating in "Paluma" guavas, with a significant difference (p <0.05) in the addition of beeswax in cassava starch films 2%. The surface roughness and the contact angle of the systems containing beeswax indicated the hydrophobic behavior of the films. This was also confirmed by the water vapor transfer rate and solubility and led to a significant improvement in the elasticity of biofilms. "Paluma" guavas were harvested at physiological maturity and selected for the uniformity f shell color and absence of defects, were covered by the casting method with filmogenic solution of cassava starch, cassava starch with the addition of beeswax and uncoated, and then conditioned in regulated chamber at 15 ± 2 ° C and 90% -95% RH for 15 days. The physicochemical and sensorial analyzes showed that the use of the filmogenic solution of cassava starch with the addition of beeswax delayed the loss of chlorophyll and maintained a good maturation index, and consequently increased the shelf life of the guavas. The sensorial attributes: aroma, texture, acceptance and purchase intention, indicated a better acceptability of the fruits with cassava starch coating with addition of beeswax, demonstrating the commercial potential of this cover / O desenvolvimento de coberturas biodegradáveis tem sido potencialmente discutido devido ao uso exacerbado de polímeros petroquímicos, e sua carga não-biodegradável, alavancando graves problemas ambientais. Além disso, a crescente demanda mundial em busca de melhoria da saúde tem alcançado interesse em soluções tecnológicas capazes de oferecer meios de conservação e redução da atividade metabólica dos frutos e hortaliças para preservar seus inúmeros nutrientes de forma eficaz por períodos longos de armazenamento. Os biopolímeros, que são a base polimérica das coberturas propostos nesse trabalho, agregam diversos pontos positivos: são atrativos por suas características renováveis, de abundância, baixo custo e fácil acesso na região do semiárido. Foram sintetizadas coberturas a base de amido de milho (3%), fécula de mandioca (2%) e gelatina (5%); cera de abelha foi adicionada como agente hidrofóbico na rede polimérica em concentrações diferentes em relação à base seca de biopolímero (0%, 5% e 10%). O efeito da incorporação da cera de abelha sobre as propriedades de barreira foi avaliado e elegeu-se o biofilme com as melhores características para cobertura em goiabas “Paluma”. Propriedades mecânicas, de barreira, estruturais, de cor e térmicas foram analisadas. A rugosidade superficial e o ângulo de contato dos sistemas contendo cera de abelha indicaram o comportamento hidrofóbico dos filmes; isto também foi confirmado pela taxa de transferência de vapor de água e solubilidade, e levou a uma importante melhoria na elasticidade dos biofilmes. Goiabas “Paluma”, colhidas na maturidade fisiológica e selecionadas quanto a uniformidade de cor da casca e ausência de defeitos, foram cobertas, pelo método casting, com solução filmogênica de fécula de mandioca, fécula de mandioca com adição de cera de abelha e sem cobertura, e então acondicionadas em câmara regulada para 15ºC±2ºC e 90%-95% UR, durante 15 dias. As análises físico-químicas e sensoriais evidenciaram que o uso da solução filmogênicas de fécula de mandioca com adição de cera de abelha retardou a perda de clorofila e manteve bom índice de maturação, e consequentemente aumentou o tempo de vida útil das goiabas. Os atributos sensoriais: aroma, textura, aceitação e intenção de compra, apontaram melhor aceitabilidade dos frutos revestidos com fécula de mandioca com adição de cera de abelha, demonstrando potencial comercial desta cobertura / 2017-06-27

The consumption of unsafe fresh vegetables has been linked to an increasing number of outbreaks of human infections. In Lebanon, although raw vegetables are major constituents of the national cuisine, studies on the safety of fresh produce are scant. This research employed a holistic approach to identify the different stages of the food chain that contribute to the microbiological risks on fresh produce and the spreading of hazards. A thorough analysis of the institutional and regulatory framework and the socio-political environment showed that the safety of local fresh produce in Lebanon is at risk due to largely unregulated practices and shortfalls in supporting the agricultural environment as influenced by the lack of a political commitment. Microbiological analysis showed that the faecal indicator levels ranged from < 0.7 to 7 log CFU/g (Escherichia coli), 1.69-8.16 log CFU/g (total coliforms) and followed a significantly increasing trend from fields to the post-harvest washing area. At washing areas, Salmonella was detected on lettuce (6.7% of raw vegetables from post-harvest washing areas). This suggested that post-harvest cross-contamination occurs predominantly in the washing stage. At retails, a combination of observation and self-reported data provided an effective tool in assessing knowledge, attitudes and practices. It showed that the food safety knowledge and sanitation practices of food handlers were inadequate, even among the better trained in corporate-managed SMEs. Overall, the microbiological quality of fresh-cut salad vegetables in SMEs was unsatisfactory. The link between Staphylococcus aureus and microorganism levels on fresh salads vegetables and the overall inspection scores could not be established. On the other hand, inspection ratings on individual components, e.g., cleanliness and cross-contamination preventive measures showed significant correlation with Listeria spp. levels. Together, results confirmed that inspection ratings don’t necessary reflect the microbiological safety of fresh vegetables and that the application of control points of risk factors that likely to contribute to microbial contamination in the production environment are essential. The washing methods were limited in their effectiveness to reduce the contamination of parsley with Salmonella. In general, the pre-wash chopping and storing of parsley at 30ºC reduced the decontamination effect of all solutions, including sodium dichloroisocyanurate which was reduced by 1.3 log CFU/g on both intact and chopped leaves stored at 30ºC. In such conditions, the transfer rate of Salmonella from one contaminated parsley to subsequently chopped clean batches on the same cutting board(CB) recorded 60%-64%. Furthermore, the transmission of Salmonella persisted via washed CBs stored at 30°C for 24 h. It is recommended to keep parsley leaves unchopped and stored at 5ºC until wash for an optimum decontamination effect and to apply vigilant sanitation of CBs after use with fresh produce. This research presented important data for quantitative risk assessment for Salmonella in parsley and useful descriptive information to inform decision-makers and educators on microbial hazards associated with fresh produce in Lebanon. It also highlighted the risks areas that require urgent interventions to improve food safety. Considering the complex institutional and political challenges in Lebanon, there is an obvious need to direct development programs and support towards local agriculture production, effective education strategies and growing awareness of consumers and stakeholders on food safety related risks.