Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Nenes, Athanasios; Committee Member: Huey, Greg; Committee Member: Meredith, Carson; Committee Member: Teja, Amyn; Committee Member: Weber, Rodney J. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Th.--Pharm.--Paris, 1873?

The regulation of food-intake in Limanda limanda was investigated, including (a) the role of the stomach as a limiting factor in fish food intake, (b) the qualities of a diet dab respond to and (c) the dynamics of food intake. Fish fed on squid (4.0 U. g'', 76.2% moisture) ate similar daily rations whether fed three times daily or once per day; when fed every three days they were unable to maintain this intake. Fish fed on pellets (18.8 kJ. g'', 8% moisture) could maintain their average daily food intake for all meal intervals tested. After a satiation meal, food intake broadly increased with deprivation time for at least 96 hours with no clear indication that stomach volume was limiting. However, when the data was re-examined using a return map (where meal m is plotted against meal m-1) there was evidence that feeding was restricted by stomach fullness as the interval between meals exceeded 25 hours. Surprisingly such limitation did not occur at higher feeding frequencies. Three models of food intake were used to simulate food-intake data, in which the role of the stomach as a constraining factor was varied: 1) Food intake was assumed always to be completely limited by stomach volume. 2) Food-intake was assumed always to be driven by a systemic need 3) Food intake was assumed to be chiefly limited by a systemic need, but when this was high, stomach volume would constrain intake. Comparisons of experimental results with these models suggest that when fish are fed frequently, or on a high-energy diet, the stomach volume is probably not limiting, whereas for a low-energy diet, fed infrequently, stomach volume was limiting when systemic need was high. Dab adapted their food intake to diets of different water content (and therefore energy density). They also adapted the distensibility of their stomachs in response to the increased volume eaten; fish fed on pellets having less distensible stomachs than those fed on squid. Thus it is unlikely that stomach volume can limit food intake in the long term, unless food quality and/or meal timing is variable and the fish cannot adapt their stomachs to the diet/feeding frequency. Methodological trials proved that that observed stomach VI volume is a function of the measurement technique, as well as the diet history of the fish, and experiments examining stomach volume should take this into consideration. The question of what aspect of a diet L. limanda adapt to was examined by testing different models using path analysis, a method of inferential modelling of causal relationships, in an attempt to explain how food-intake is regulated. Dab were found to be adapting to both the energy content of the diet and to the individual nutrients. The dynamics driving food intake in groups of dab were investigated using non-linear time series analyses. These proved to be low-dimensional, significantly non-linear, deterministic systems. The data also suggests that such systems are either capable of occasional chaotic behaviour, or are on the edge of chaos i. e. complex dynamical systems. Thus food intake is under the direct control of few (two or three) variables, through which the many known factors that influence food intake must act. Comparisons were made with individuals and groups of Oncorhynchus mykiss, with a brief look at Merlangius merlangus and Dicentrarchus labrax. These results were similar to the dab, and so this dynamical behaviour may be a feature of teleost fish in general. Importantly the fact that individual trout had similar feeding behaviour to groups indicate that the findings were not a function of hierarchical dynamics. The significance of this finding should be that appetite control with these properties allows rapid adjustment of fish according to changes in diet quality.

Made available in DSpace on 2014-06-12T23:14:50Z (GMT). No. of bitstreams: 2 arquivo8962_1.pdf: 612408 bytes, checksum: b775622cd500cf37d88772515a5ea702 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2002 / Este trabalho apresenta uma nova metodologia aplicada na construção de simuladores baseados em elementos de volume. O processo de segmentação dos modelos resume-se à tarefa de colorir as imagens tomográficas atribuindo uma cor diferente para cada órgão segmentado. Um modelo de cabeça e pescoço foi construído utilizando esta nova técnica. Além de simplificar o procedimento permitindo a construção dos modelos em um menor período de tempo, as informações são armazenadas de forma otimizada aumentando a performance do programa que calcula o transporte de radiação. A execução de comandos gráficos pelo mesmo programa que calcula o transporte de radiação permite também que imagens sejam reconstruídas a partir dos dados do modelo mostrando regiões de isodose, sob diversos pontos de vista, aumentando o nível da informação passada ao usuário. Radiografias virtuais do modelo construído também podem ser obtidas. Esta capacidade permite que estudos sejam realizados visando a otimização das técnicas radiográficas avaliando ao mesmo tempo as doses nos órgãos e tecidos. O programa aqui apresentado, denominado MCvoxEL, que implementa esta nova metodologia, foi validado comparando-se os seus resultados com os de programas já consolidados no meio científico. Coeficientes de conversão para doses provenientes de exposições a feixes de fótons paralelos também foram obtidos

L'objectif de cette thèse a consisté à étudier différentes topologies d’oscillateur à faible bruit de phase et de synthèses de fréquence à 4.6 GHz pour une application de la micro-horloge atomique au Césium. Nous avons étudié 7 topologies d'oscillateur à 2,1 GHz (à base du résonateur BAW utilisant la filière technologie 0.25μm SiGe:C BiCMOS de chez STMicroelectronics) à faible bruit de phase présentant des performances à l’état de l’art pour certaines topologies. Une comparaison expérimentale de ces différentes topologies a confirmé les résultats théoriques. En particulier, les résultats expérimentaux ont montré que la topologie différentielle possède de meilleures performances en bruit de phase et qu'elle est moins sensible aux bruits provenant des alimentations comparées aux topologies single-ended. Enfin, une topologie Double-Colpitts-Différentiel a été proposée. Elle a permis d'obtenir théoriquement des performances en bruit de phase, en encombrement au delà de l'état de l'art. Différentes architectures des synthèses de fréquence à 4,6 GHz ont été étudiées. Nous avons réalisé une synthèse de fréquence utilisant un circuit DDS piloté par un FPGA. Pour obtenir de bonnes performances au niveau de la pureté du spectre, différents circuits commerciaux constituant cette synthèse de fréquence ont été caractérisés finement. Finalement, l’architecture proposée a été utilisée au sein d'un dispositif complet de micro-horloge de césium. Nous avons obtenu un signal verrouillé présentant une stabilité de 2.5 10 – 9 à 1seconde. / The objective of this thesis is to study different topologies of low phase noise oscillator as well as a frequency synthesizer at 4.6 GHz for the application of Cs vapor microcell atomic clock. We have studied 7 topologies of low-phase-noise oscillators combined with BAW resonator and 0.25μm SiGe:C BiCMOS Technology from ST Microroelectronics at 2.1 GHz, which present the stat of the art performances. An experimental comparison of these different topologies confirmed the theoretical results. In particular, experimental results showed that the differential topology has better performance in phase noise and is less sensitive to the noise from power supply compared to the single-ended topologies. Finally, a Double-differential-Colpitts topology was proposed, because it was theoretically possible to obtain performance beyond the state of the art in phase noise and in size. Different architectures of frequency synthesizer at 4.6 GHz were studied. We have realized a frequency synthesizer in which a DDS controlled by a FPGA was used. To get good performance in terms of purity of the spectrum, different commercial circuits constituting the frequency synthesis were finely characterized. Finally, the proposed architecture has been used within a completed Cs vapor microcell atomic clock. We got a signal locked with a stability of 2.5 10 – 9 at 1second.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Rapid development of digital technology has enabled the real-time volume rendering of scientific data, in particular large microscopy data sets. In general, volume rendering techniques project 3D discrete datasets onto 2D image planes, with the generated views being transparent and having designated color that is not necessarily "real" color. Volume rendering techniques initially require designating a processing method that assigns different colors and transparency coefficients to different regions. Then based on the "viewer" and the dataset "location," the method will determine the final imaging effect. Current popular techniques include ray casting, splatting, shear warp, and texture-based volume rendering. Of particular interest is ray casting as it permits the display of objects interior to a dataset as well as render complex objects such as skeleton and muscle. However, ray casting requires large memory and suffers from longer processing time. One way to address this is to parallelize its implementation on programmable graphic processing hardware. This thesis proposes a GPU based ray casting algorithm that can render a 3D volume in real-time application. In addition, to implementing volume rendering techniques on programmable graphic processing hardware to decrease execution times, 3D image segmentation techniques can also be utilized to increase execution speeds. In 3D image segmentation, the dataset is partitioned into smaller sized regions based on specific properties. By using a 3D segmentation method in volume rendering applications, users can extract individual objects from within the 3D dataset for rendering and further analysis. This thesis proposes a 3D segmentation algorithm with combinatorial map that can be parallelized on graphic processing units.

A great challenge in the volume-rendering field is to achieve high-quality images in an acceptable amount of time. In the area of volume rendering, there is always a trade-off between speed and quality. Applications where only high-quality images are acceptable often use the ray-casting algorithm, but this method is computationally expensive and typically achieves low frame rates. The work presented here is RZSweep, a new volume-rendering algorithm for uniform rectilinear datasets, that gives high-quality images in a reasonable amount of time. In this algorithm a plane sweeps the vertices of the implicit grid of regular datasets in depth order, projecting all the implicit faces incident on each vertex. This algorithm uses the inherent properties of a rectilinear datasets. RZSweep is an object-order, back-toront, direct volume rendering, face projection algorithm for rectilinear datasets using the cell approach. It is a single processor serial algorithm. The simplicity of the algorithm allows the use of the graphics pipeline for hardware-assisted projection, and also, with minimum modification, a version of the algorithm that is graphics-hardware independent. Lighting, color and various opacity transfer functions are implemented for giving realism to the final resulting images. Finally, an image comparison is done between RZSweep and a 3D texture-based method for volume rendering using standard image metrics like Euclidian and geometric differences.

Effects of thinning, such as increased diameter growth and decreased mortality in the residual stand, have been recognized by foresters for many years. These effects are largely the result of increased tree vigor which is induced by a decreased level of competition. These relationships are reflected in many of the models that are central to PTAEDA2, a growth and yield simulator which was developed for use with loblolly pine (Pinus taeda) plantations established on cut-over, site prepared lands. Data from a long-term thinning study served as a basis for attempting to improve the predictive output of PTAEDA2. Assessment of differences in model parameter estimates between three levels of thinning intensity led to various approaches to reach this goal. Height increment and mortality models were found to need no additional refinement and were re-fit using all available data. Diameter increment and crown ratio model forms could not account for thinning effects in their present form and thinning response functions that could provide the proper behavioral response were added to these models.Models were evaluated individually and in combinations in a reduced growth simulator. This reduced simulator is a modified form of the growth subroutines in PTAEDA2 and is designed to utilize external data. Results of growth simulation runs show improvements in predictive ability for the crown ratio model fit to all data and for the re-fit height increment model/crown ratio model with thinning response variable combination. The diameter increment model with a thinning response variable significantly improved diameter prediction within the simulator, but predicted stand volumes were poor. The re-fit mortality function resulted in greater prediction error for mortality than the original PTAEDA2 mortality function. / Master of Science

<p>Knowledge of the leftventricular (LV) pressure-volume relation, along withparameters derived from this relation, have led to newpossibilities for the characterisation of cardiac pumpfunction, in both experimental studies and clinicalsettings.</p><p>The pressure-volume diagram is apowerful tool for visualising LV performance, but in order tobe clinically useful it is necessary to make plots continuouslyand on-line. The conductance catheter technique offers thispossibility. The conductance catheter system has experiencedgrowing interest among cardiologists, physiologists, surgeons,and anaesthesiologists around the world as a powerful newresearch tool, but the invasiveness of this technique has beena limiting factor for most clinical applications. The catheterneeds to be thinner and softer in order to make this techniquemore suitable for human use.</p><p>This thesis reports of a newthin and soft conductance catheter for continuously and on-linemeasurements of LV pressure and volume.</p><p>One way to reduce both cathetersize and stiffness is to decrease the number of electrodes onthe catheter. Theoretical calculations shown in this thesisproves that it is possible to obtain the same performance witha single segment catheter as with a five-segment catheter. Thethin catheter has been tested and compared to a commercialfive-segment conductance catheter in animal studies.</p><p>We conclude that the thin singlesegment conductance catheter can measure left ventricularvolume and pessure. The regression coefficient between the twomethods is good independent of loading condition and duringbaseline conditions the catheters produce very similar volumecurves. During preload reduction the estimated volume reductionis different in the two systems.</p><p>Our thin catheter does notdisturb the heart's normal electrophysiology, neither by thecatheter current nor by any mechanical stimuli. The resultsdemonstrates that our thin, soft, single segment conductancecatheter has performance characteristics which warrant furtherdevelopment, with the goal to make the method available forhuman use.</p>