No description available.

Thesis (Ph. D.)--Catholic University of America. / At head of title: The Catholic University of America.

Thesis (Ph. D.)--Catholic University of America. / At head of title: The Catholic University of America.

<div>Bacteria which enter a viable but non-culturable state cannot be concentrated by enrichment. This means they may not reach a detectable concentration for PCR methods - especially in the presence of sample compounds which may act as PCR reaction inhibitors. An alternative strategy for concentration of bacteria from aqueous samples is explored in this work using tangential flow filtration. The effectiveness of this technology to concentrate pathogens from food-derived samples was previously demonstrated; however, losses of bacteria to the filtration system can still be high (i.e. recovery of bacteria is low). </div><div>The goal of this research was to maximize recovery of pathogenic microorganisms from hollow fiber filtration processes while also maximizing flux. In this way, high recovery filtration conditions could be selected while keeping filtration time low. It was hypothesized that flux would have relatively lower impact on final recovery of bacteria at high shear rates (27,000 1/s) which are sufficient to remove attached bacteria on surfaces. It was hypothesized that these high shear rates would not cause loss of bacterial viability, and the main cause of bacterial losses during filtration would be accumulation on the membrane surface.</div><div>To test these hypotheses, single fiber filter modules (both microfilters and ultrafilters with 0.5 mm inner diameter), were constructed and used to concentrate GFP-producing Escherichia coli at a wide range of flux conditions. Post-concentration, fluorescence micrographs of bisected hollow fibers illustrated patterns of bacterial accumulation along the length of the fiber. A simple recovery model was constructed to predict recovery as a function of flux and shear rate, and predictions were compared against the experimental data. </div><div>Both in the experiments and in the simple recovery model developed in this dissertation, recoveries near 90% were achievable at high shear rates when flux was ≤0.5 mL min-1 cm-2. This amounted to a 3-hour filtration time for a 225 mL sample. Compared to a filtration with only 30% recovery, detectable bacteria concentrations could be achieved with lower starting concentrations – ~5 CFU/mL starting concentration versus at least 15 CFU/mL. Given these high recoveries (determined with plating methods on agar) occurred at high pressure and shear conditions, it was determined the filtration did not affect bacterial viability. </div><div>In addition to using the model to predict recovery at various shear and flux conditions, it would be helpful to predict module designs or concentration strategies which could improve bacterial recoveries from the filter. One strategy, explored with preliminary data, was to pre-develop a layer of bacteria on the filter surface prior to concentrating samples. </div><div>Understanding and reducing the losses of bacteria during tangential flow filtration could enable detection of dilute levels of viable but non-culturable microorganisms; in addition, sensitivity of detection could be improved for quickly concentration culturable microorganisms in food and water samples.</div><div><br></div>

Undersökningen utgår ifrån Watson, Morris &amp; Harris (2010) och Annetta m.fl. (2008) undersökningar av användandet av dataspel i en läromiljö samt Portnow’s (2008) teorier om tangential learning. Istället för att fokusera på om dataspel påverkan fokusera undersökningen på olika typer av narrativa strukturer, linjär och nät, påverkar elevers förmåga att minnas information förmedlad i ett dataspel. Är det fördelaktigt ifall eleven själv får söka upp informationen eller riskeras det att eleven missar vitala delar? Som artefakt skapades två mekanisk identiska pusselplattformsspel vilka använder sig av antingen linjärtnarrativ eller nätnarrativ vilka testades på en skolklass vid två tillfällen. Vid första tillfället spelade klassen igenom prototyperna, halva spelade linjär, och besvarade frågor rörande informationen i spelet. Efter fyra dagar fick eleverna besvara samma information, för att sedan jämföras med tidigare svar. Resultatet visade att de olika strukturerna påverkar eleverna, där linjärtnarrativ är att föredra då resultatet generellt är bättre och mer konstant.

"Excessive discharge of heavy metals has been one of the major causes of water pollution worldwide. Various traditional methods of heavy metal removal have been devised but certain drawbacks like high cost, high energy requirement, and the production of toxic sludge have limited their use. Hence, biosorption is one of the alternative methodologies. This study combined biosorption and diafiltration in an attempt to optimize Polymer Enhanced Diafiltration to study copper removal from aqueous solutions by the use of a biopolymer, lambda-carrageenan. Lambda-carrageenan was studied as a biosorbent owing to properties such as low cost, good water solubility, non-gelling nature and the presence of sulfate groups which can sequester cations. Conditions for binding such as pH, temperature and concentration of copper and lambda-carrageenan were studied. Equilibrium dialysis experiments were performed to study the metal ion membrane transport kinetics and to determine the metal ion binding capacity and strength of the copper-biopolymer association. Rheological measurements were performed to determine how the viscosity of lambda-carrageenan changes with increase in shear stress and with increase in metal concentration. The solution was found to be shear thinning. However, with increase in metal concentration, viscosity was found to increase when high concentrations of polymer (8 g/L and 12 g/L) were used. Solution viscosity was found to decrease with increase in metal concentration when 4 g/L of polymer was used. Polymer Enhanced Diafiltration studies showed no leakage of the polymer through the membrane and no significant binding elsewhere in the PEDF system. It also showed an impressive retention of copper inspite of a rather high metal ion-polymer dissociation constant suggesting a yet not understood series of events occurring on the membrane of the PEDF system. Lambda-carrageenan is a linear polysaccharide, which might be stacking up on the membrane after forming layers, and not allowing any free metal ion to escape. Other reasons could be the sieving effect, degradation of the polymer due to shear and compaction of molecule on metal binding such that the polymer is not itself escaping through the membrane, but also not allowing the free metal ion to escape. Hence, this study suggests the need for more information on the metal-polymer interactions on the surface of the membrane by designing a direct observation experiment with a mini-tangential flow filtration system."

The key to improving drying quality and reducing drying time and energy consumption lies in understanding and controlling moisture movement during drying. As wood dries, strains and stresses develop as a result of restraints imposed by moisture gradients and differential shrinkage in wood. So accurately measuring the moisture gradient in wood during drying will be helpful to improving drying quality. In this project, moisture gradients in red oak will be measured through four different techniques----<i><b>bandsaw slicing, Forstner bit layering, flaking and razor blade slicing</i></b>. The first two techniques are found in the literature. The last two are developed in this study. The results obtained with these four techniques were compared, and it was found that the newly developed techniques could get moisture gradients that were closer to the true value. The <i><b>thickness</i></b> of the slice was assumed to affect measuring the moisture gradient because of the environmental influences. So a thickness series was tested with the two new technique----flaking and razor blade slicing. The results showed that there was no slice or flake thickness effect on the moisture gradients.And an optimum slice and flake thickness was determined for the wood industries and research studies. Finally, the <i><b>directional</i></b> effect on transverse moisture movement during kiln drying was examined through measuring moisture gradients in the tangential and radial directions of wood. The results showed that moisture moved slightly faster in the radial direction than in the tangential direction during kiln drying and the moisture gradients in the tangential direction were slightly steeper than those in the radial direction. / Master of Science

Nesta tese apresentamos uma contribuição para o estudo da transição do retrato de fase de uma equação diferencial descontínua específica ao longo de uma linha de descontinuidade. A equação diferencial que tratamos neste trabalho é a das linhas de curvatura principal de uma superfície S contendo uma curva distinguida B e imersa em R^3. A linha de descontinuidade é a curva B, a qual é o bordo comum de duas superfícies suaves justapostas que formam S. Na primeira parte do trabalho consideramos a superfície seccionalmente suave, S = S+ U B U S-, obtida pela justaposição de S+ e S- ao longo do bordo comum B. O estudo da configuração principal de S nos casos em que as linhas de curvatura principal das superfícies S+ e S- tem contato quadrático ou cruzam transversalmente B foi feito por comparação com a configuração principal de uma superfície suave, obtida de S pelo processo da \"regularização\" ao longo da curva de descontinuidade B. Na segunda parte do trabalho estudamos as linhas de curvatura principal de uma superfície S em R^3 com bordo B e da superfície suave obtida de S através dos processos de engrossamento e regularização definidos por Garcia e Sotomayor em [5], onde os autores consideraram o caso genérico, sem pontos umbílicos e contato quadrático de uma linha de curvatura principal com B. Damos aqui continuidade ao estudo feito em [5] analisando o caso de contato cúbico com o bordo B. Obtivemos que dos pontos da curva bordo comum B de contato quadrático e de cruzamento transversal emergem, sobre a superfície regularizada, pontos umbílicos Darbouxianos dos tipos D1 e D3, enquanto que, para o ponto sobre B de contato cúbico obtivemos pontos umbílicos Darbouxianos dos tipos D1, D2 e D3 e também pontos umbílicos não Darbouxianos dos tipos D12 e D23. [5] Garcia, R., and Sotomayor, J. Umbilic and tangential singularities on configurations of principal curvature lines. Anais da Academia Brasileira de Ciências 74, 1 (2002), 117. / In this work we present a contribution to the study of the transition of the phase portrait of a specific discontinuous differential equation along a line of discontinuity. The differential equations under consideration will be that of the principal curvature lines of a surface S with a distinguished curve B immersed in R^3, where the line of discontinuity is the curve B which is the common border of two smooth surfaces attached to make up S. In the first part of the work we consider a piecewise smooth surface S = S+ U B U S-, obtained by the juxtaposition of two smooth surfaces S+ and S- along their common border B. The analysis of the principal configuration of S in the cases where the principal curvature lines of the surfaces S+ and S- have quadratic contact or cross transversally B was carried out by comparison with a smooth surface, obtained from S by the \"regularization\" along the discontinuity curve B. In the second part of the work we study the principal curvature lines of a surface S in R^3 with boundary B and of the smooth surface obtained from S by thickening and smoothing introduced by Garcia and Sotomayor in [5], where they considered the generic case of no umbilic points and at most quadratic contact of principal lines with B. Here we pursue the study in [5] and analyze the case of cubic contact with the border B. We established that while from quadratic contact points with B emerge on the smoothed surface Darbouxian umbilics of D1 and D3 types, from the cubic contact points appear Darbouxian umbilics of types D1, D2 and D3 as well as non Darbouxian points of types D12 and D23. [5] Garcia, R., and Sotomayor, J. Umbilic and tangential singularities on configurations of principal curvature lines. Anais da Academia Brasileira de Ciências 74, 1 (2002), 117.

Nesta tese apresentamos uma contribuição para o estudo da transição do retrato de fase de uma equação diferencial descontínua específica ao longo de uma linha de descontinuidade. A equação diferencial que tratamos neste trabalho é a das linhas de curvatura principal de uma superfície S contendo uma curva distinguida B e imersa em R^3. A linha de descontinuidade é a curva B, a qual é o bordo comum de duas superfícies suaves justapostas que formam S. Na primeira parte do trabalho consideramos a superfície seccionalmente suave, S = S+ U B U S-, obtida pela justaposição de S+ e S- ao longo do bordo comum B. O estudo da configuração principal de S nos casos em que as linhas de curvatura principal das superfícies S+ e S- tem contato quadrático ou cruzam transversalmente B foi feito por comparação com a configuração principal de uma superfície suave, obtida de S pelo processo da \"regularização\" ao longo da curva de descontinuidade B. Na segunda parte do trabalho estudamos as linhas de curvatura principal de uma superfície S em R^3 com bordo B e da superfície suave obtida de S através dos processos de engrossamento e regularização definidos por Garcia e Sotomayor em [5], onde os autores consideraram o caso genérico, sem pontos umbílicos e contato quadrático de uma linha de curvatura principal com B. Damos aqui continuidade ao estudo feito em [5] analisando o caso de contato cúbico com o bordo B. Obtivemos que dos pontos da curva bordo comum B de contato quadrático e de cruzamento transversal emergem, sobre a superfície regularizada, pontos umbílicos Darbouxianos dos tipos D1 e D3, enquanto que, para o ponto sobre B de contato cúbico obtivemos pontos umbílicos Darbouxianos dos tipos D1, D2 e D3 e também pontos umbílicos não Darbouxianos dos tipos D12 e D23. [5] Garcia, R., and Sotomayor, J. Umbilic and tangential singularities on configurations of principal curvature lines. Anais da Academia Brasileira de Ciências 74, 1 (2002), 117. / In this work we present a contribution to the study of the transition of the phase portrait of a specific discontinuous differential equation along a line of discontinuity. The differential equations under consideration will be that of the principal curvature lines of a surface S with a distinguished curve B immersed in R^3, where the line of discontinuity is the curve B which is the common border of two smooth surfaces attached to make up S. In the first part of the work we consider a piecewise smooth surface S = S+ U B U S-, obtained by the juxtaposition of two smooth surfaces S+ and S- along their common border B. The analysis of the principal configuration of S in the cases where the principal curvature lines of the surfaces S+ and S- have quadratic contact or cross transversally B was carried out by comparison with a smooth surface, obtained from S by the \"regularization\" along the discontinuity curve B. In the second part of the work we study the principal curvature lines of a surface S in R^3 with boundary B and of the smooth surface obtained from S by thickening and smoothing introduced by Garcia and Sotomayor in [5], where they considered the generic case of no umbilic points and at most quadratic contact of principal lines with B. Here we pursue the study in [5] and analyze the case of cubic contact with the border B. We established that while from quadratic contact points with B emerge on the smoothed surface Darbouxian umbilics of D1 and D3 types, from the cubic contact points appear Darbouxian umbilics of types D1, D2 and D3 as well as non Darbouxian points of types D12 and D23. [5] Garcia, R., and Sotomayor, J. Umbilic and tangential singularities on configurations of principal curvature lines. Anais da Academia Brasileira de Ciências 74, 1 (2002), 117.

Signal processing in the visual system is mediated by classic neurotransmission and neuropeptidergic modulatory pathways. In Dipteran insects, especially in the fruitfly Drosophila melanogaster, the morphology of the visual system is very well described. However neurotransmitter and neuropeptidergic circuits within the optic lobe neuropil are only partially known. Using several transgenic fly lines and antibodies we determined the localization of the classical neurotransmitters GABA, acetylcholine and glutamate in the visual system, and their putative targets via detecting several neurotransmitter receptors. We paid particular attention to the peripheral neuropil layer called the lamina, where the light signals are filtered, channeled and amplified (Paper I). We discovered four new types of efferent tangential neurons branching distally to the lamina. Among them was the first neuropeptidergic neuron (LMIo) in this region of Drosophila. The LMIo expresses myoinhibitory peptide (MIP) and has its cell body located close to the main lateral clock neurons that express the neuropeptide pigment-dispersing factor (PDF)(Paper II). Since in other Dipteran species PDF is expressed in processes distally to the lamina, we performed comparative anatomical studies of the MIP, PDF, Ion Transport Peptide (ITP) and serotonin (5-HT) distribution in the visual system of the flies Drosophila and Calliphora. Our data suggest that PDF signaling distal to the lamina of the blowfly might be replaced by MIP signaling in the fruitfly, while ITP and 5-HT expression is conserved in the two species (Paper III). Serotonin is crucial in light adaptation during the daily light-dark cycles. We analyzed putative serotonergic circuits in the lamina. We found that LMIo neurons express the inhibitory receptor 5-HT1A, while 5-HT1B and 5-HT2 are both expressed in the epithelial glia of the lamina. Another novel wide-field neuron with lamina branches expresses the excitatory serotonin receptor 5-HT7. Our studies have identified a fairly complex neuronal circuitry in the tangential plexus above the lamina. (Paper IV). Finally we tested circadian locomotor activity rhythms in flies with the GABAB receptor knocked down on the lateral PDF-expressing clock neurons. We observed significant changes in the activity periods and diminished strength of rhythmicity during DD suggesting a modulatory role of GABA in clock function (Paper V). / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.