HINTERGUND: Ziel dieser Studie war es, den Einfluss zweier in der klinischen Routine gebräuchlicher Oxygenatoren mit unterschiedlichen Membranen, bestehend aus Polymethylpenten (PMP) oder aus Polypropylen (PPL), auf die Plasmakonzentration von Sevofluran während der extrakorporalen Zirkulation zu untersuchen. Es sollte geprüft werden, ob mittels der PMP-Membran vs. der PPL-Membran eine klinisch relevante Blutplasmakonzentration von vor dem Start der extrakorporalen Zirkulation appliziertem Sevofluran während des gesamten Zeitraums der extrakorporalen Zirkulation erhalten bleibt ohne eine zusätzliche Einspeisung des volatilen Anästhetikums über einen Vapor in den Frischgasfluss des Oxygenators vorzunehmen. METHODIK: Zwanzig Patienten, welche sich einer elektiven koronaren Bypassoperation unterzogen, wurden randomisiert einer der beiden Gruppen mit unterschiedlichem Membranoxygenator zugeordnet. Die Konzentrationen von Sevofluran wurden während der Operation im Plasma der Patienten und am Oygenatorgasauslass der Herz-Lungen-Maschine gemessen. Es wurde ermittelt, wie hoch der Verbrauch von additiv intravenös verabreichten Anästhetika in der jeweiligen Gruppe war, um eine adäquate Narkosetiefe aufrecht zu erhalten. ERGEBNISSE: Der Verlust von Sevofluran war signifikant geringer wenn ein PMP-Membranoxygenator im Vergleich zu einem PPL-Membranoxygenator verwendet wurde. Die Plasmakonzentration von Sevofluran zeigte vor Beginn (PPL 1.15-4.84 (2.49) vs. PMP 1.29-3.97 (3.97) μl×100 ml^-1, p=0.62) und fünf Minuten nach dem Start der extrakorporalen Zirkulation (PPL 0.72-2.32 (1.42) vs. PMP 0.98-2.29 (1.68) µl x 100 ml^-1, p=0.31) keinen signifikanten Unterschied zwischen den beiden Oxygenatoren. Zehn Minuten nach Beginn der extrakorporalen Zirkulation war jedoch die Sevofluranplasmakonzentration in der Patientengruppe mit PPL-Membranoxygenator im Vergleich zu der PMP-Oxygenator-Gruppe signifikant gefallen (PPL 0.48-1.79 (0.93) vs. PMP 0.80-2.15 (1.56) μl×100 ml^-1, p=0.02). Dieser Unterschied hielt bis zehn Minuten nach Beendigung der extrakorporalen Zirkulation an. Zeitweise lag die Sevofluranplasmakonzentration in der Gruppe mit PMP-Membranoxygenator doppelt so hoch. Der Verbrauch von additiv intravenös verabreichten Anästhetika war in der Patientengruppe mit PMP-Membran signifikant geringer. FAZIT: Zusammenfassend konnte gezeigt werden, dass der Gebrauch eines PMP-Membranoxygenators im Vergleich zu einem PPL-Membranoxygenator zu einem signifikant niedrigeren Verlust von Sevofluran über die Membran führt, was in einer höheren, narkoserelevanten Sevofluranplasmakonzentration resultiert.

Afin de permettre de développer un modèle de mémoire non-volatile basée sur le transistor à nanotube de carbone à commande optique qui est utilisée dans des circuits électroniques neuromorphiques, il est nécessaire de comprendre les physiques électroniques et optoélectroniques des nanotubes de carbone, en particulier l’origine de l'effet mémoire que présente ces transistors. C’est dans ce contexte général que cette thèse s'intègre. Le travail est mené sur trois plans :• Caractériser électriquement et optoélectroniquement des structures de test des CNTFETs et des OG-CNTFETs.• Développer un modèle compact pour les contacts Schottky dans les transistors à nanotube de carbone de la façon auto-cohérente basé sur le diamètre et la nature du métal d’électrode en utilisant la méthode de la barrière effective avec les paramètres nécessaires calibrés.• Modéliser l'OG-CNTFET selon les régimes de fonctionnement, lecture, écriture, effacement ou programmation pour application à une mémoire non-volatile en intégrant le mécanisme de piégeage et dépiégeage à l’interface polymère/oxyde. / This PhD thesis presents a computationally efficient physics-based compact model for optically-gated carbon nanotube field effect transistors (OG-CNTFETs), especially in the non-volatile memory application. This model includes memory operations such as “read”, “write”, “erase” or “program”, and “reset” which are modeled using trapping and detrapping mechanisms at the polymer/oxide interface. The relaxation of the memory state is taken into account. Furthermore, the self-consistent modeling of Schottky barriers at contacts between the carbon nanotube channel and metal electrodes is integrated in this model applying the effective Schottky barrier method. The Schottky contact model can be included in CNTFET based devices for a typical biasing range of carbon nanotube transistors. This compact model is validated by the good agreement between simulation results and experimental data (I-V characteristics). In the non-volatile memory application, this model can fully reproduce device behaviors in transient simulations. A prediction study of the key technological parameter, the CNT diameter variety is established to expect its impact on the transistor performance, and more importantly, on the memory operation. In the other hand, this thesis presents a preliminary electric characterization (I-V) of CNTFETs and OG-CNTFETs for the device modeling database. A preliminary optoelectronic characterization method is proposed.

Compared to traditional hard-disk drives (HDDs), non-volatile (NV) memory technologies offer significant performance advantages on one hand, but also incur significant cost and asymmetric write-performance on the other. A common strategy to manage such cost- and performance-differentials is to use hierarchies such that a small, but intensely accessed, working set is staged in the NV storage (selective caching). However, when this working set includes write-heavy data, the low write-lifetime of NV storage necessitates significant over-provisioning to maintain required lifespans (e.g., storage lifespan must match or exceed 3 year server lifespan). One may think that employing DRAM-based write-buffers can filter writes that trickle through to the NV storage and thus alleviate the write-pressure felt at the NV storage. Unfortunately, selective caches, when used with common recency-based or frequency-based replacement, have access patterns that require large write buffers (e.g., 100MB+ relative to a 12GB cache) to filter writes adequately. Further, these large DRAM write-buffers also require backup-power to ensure the durability of disk writes. More sophisticated replacement policies that combine recency and frequency can reduce the size of the DRAM buffer (while preserving write-filtering), but are so computationally-expensive that they can limit the I/O rate, especially for simple controllers (e.g., RAID controller). <br>My first contribution is the design and implementation of WriteGuard– a self-tuning sieving write-buffer algorithm that filters writes as well as the highly-effective (but computationally-expensive) algorithms while requiring lightweight computation comparable to a simple LRU-based write-buffer. While WriteGuard reduces the capacity needed for DRAM buffering (to approx. 64 MB), it does not eliminate the need for DRAM buffers (and corresponding power backup).<br>For my second thrust, I identify two specific application characteristics – (1) the vast majority of the write-buffer’s contents is composed of write-dominant blocks, and (2) the vast majority of blocks in the write-buffer are overwritten within a period of 28 hours. I show that these characteristics help enable a high-density, optimized STT-MRAM as a replacement for DRAM, which enables durable write-buffers (thus eliminating the cost of power backup for the write-buffer). My optimized STT-MRAM-based write buffer achieves higher density by (a) trading off superfluous durability by exploiting characteristic (2), and (b) deoptimizing the read-performance of STT-MRAM by leveraging characteristic (1). Together, the techniques increase the density of STT-MRAM by 20% with low or no impact on write-buffer performance.<br>

Doctor of Philosophy / Department of Human Nutrition / Delores H. Chambers / A green tea descriptive sensory lexicon was developed by a highly trained panel, which identified, defined, and referenced 31 flavor attributes of green tea. The attributes were categorized as “green” (asparagus, beany, Brussels sprout, celery, parsley, spinach, green beans, and green herb-like), “brown” (ashy/sooty, brown spice, burnt/scorched, nutty, and tobacco), “fruity/floral” (fruity, floral/perfumy, citrus, and fermented), “mouthfeel” (astringent and tooth-etching), “basic tastes” (overall sweet and bitter), and other attributes (almond, animalic, grain, musty/new leather, mint, seaweed, and straw-like). Using the green tea lexicon, the flavor differences that exist among a wide range of green teas (n=138) produced in various countries were determined. Roast-processed teas were mostly responsible for brown-related flavors and steam-processed teas were mostly responsible for green-related flavors. Aroma analyses of green tea showed that the concentration of volatile compounds were much lower than stated in the literature. Brown, brown-related attributes, bitterness, and astringency became stronger and green and green-related attributes become weaker as the brewing time lengthened (1, 2, 5, and 20 min) and the water temperature increased (50, 70, 95°C). The flavor characteristics of roast-processed, steam processed, or roast-steam-processed Korean green teas differed only in their characterizing green flavors. The flavor and aroma of green teas change after sequential brewings. Green teas in leaf form can be brewed four times: the first two brews providing stronger flavor and aroma characteristics whereas the third and fourth brews will provide milder flavor and aroma characteristics. The flavor and aroma change in green teas that are stored over two years were observed at 3, 6, 12, 18, and 24 months after their original packaging dates. Green tea changes minimally during the first year of storage and only slightly more during the first two years of storage. Consumer studies and descriptive evaluations were conducted to understand what green tea flavor characteristics influence US consumers' liking. Twelve green tea samples were evaluated by three consumer groups from Korea, Thailand, and the United States. The current research suggests that familiarity plays a role in tea acceptance. However, various flavor profiles may be acceptable to consumers who are familiar with other flavors of green tea.

Background: Enteric methane from rumen methanogens is responsible for 25.9 % of total methane emissions in the United States. Rumen methanogens also contribute to decreased animal feed efficiency. For methane mitigation strategies to be successful, it is important to establish which factors influence the rumen methanogen community and rumen volatile fatty acids (VFA). In the present study, we used next-generation sequencing to determine if dairy breed and/or days in milk (DIM) (high-fiber periparturient versus high-starch postpartum diets) affect the rumen environment and methanogen community of primiparous Holstein, Jersey, and Holstein-Jersey crossbreeds. Results: When the 16S rRNA gene sequences were processed and assigned to operational taxonomic units (OTU), a core methanogen community was identified, consisting of Methanobrevibacter (Mbr.) smithii, Mbr. thaueri, Mbr. ruminantium, and Mbr. millerae. The 16S rRNA gene sequence reads clustered at 3 DIM, but not by breed. At 3 DIM, the mean % abundance of Mbr. thaueri was lower in Jerseys (26.9 %) and higher in Holsteins (30.7 %) and Holstein-Jersey crossbreeds (30.3 %) (P < 0.001). The molar concentrations of total VFA were higher at 3 DIM than at 93, 183, and 273 DIM, whereas the molar proportions of propionate were increased at 3 and 93 DIM, relative to 183 and 273 DIM. Rumen methanogen densities, distributions of the Mbr. species, and VFA molar proportions did not differ by breed. Conclusions: The data from the present study suggest that a core methanogen community is present among dairy breeds, through out a lactation. Furthermore, the methanogen communities were more influenced by DIM and the breed by DIM interactions than breed differences.

Thesis (MScAgric (Viticulture and Oenology))--Stellenbosch University, 2008. / The production of good quality wine is essential to ensure competitiveness on an international level. Wine quality is usually evaluated for the visual, olfactory and taste characteristics of that specific wine. The winemaking process starts with the grapes in the vineyard followed by oenological practises in the winery until the final wine is bottled. Factors that could influence wine quality include the grape quality from which the wine is made and different techniques used during wine production. Other factors include the presence as well as the interaction between microorganisms found in the grape juice and wine, and the biochemical effect these microorganisms have on certain chemical compounds in the wine. The different microorganisms found in grape juice and wine can either have a negative or positive contribution to the final quality of the wine. During certain stages of the winemaking process the growth and metabolic activity of certain microorganisms is a necessity to produce good wine. During other stages the presence of certain microorganisms can lead to the development of compounds that is regarded as off-flavours and therefore lead to unpalatable wines of low quality. Yeast strains that naturally present on the grapes and in the winery can also contribute to the final quality of the wine. Brettanomyces yeasts are part of the natural flora of winemaking and can drastically influence the aroma characters of a wine through the production of volatile phenols. The general aroma descriptions of volatile phenols include "smoky", "spicy", "barnyard", "animal" and "medicinal". Although some wine drinkers believe that these characters can add to the complexity of a wine, high levels of volatile phenols is mostly regarded as off-flavours and mask the natural fruity flavours of a wine. With this study we wanted to generate a better understanding of the effect of different winemaking practises on the production of volatile phenols by B. bruxellensis. We evaluated the difference in volatile phenol production when B. bruxellensis was introduced before or after alcoholic fermentation. We have shown that B. bruxellensis could grow and produce volatile phenols during alcoholic fermentation. Results obtained also showed that commercial wine yeast strains could produce the vinyl derivatives that serve as precursors for Brettanomyces yeast to produce the ethyl derivatives. The commercial yeast strains differed in their ability to produce vinyl derivatives. Different malolactic fermentation scenarios were evaluated, namely spontaneous versus inoculated, and with or without yeast lees. Results showed that spontaneous malolactic fermentation had higher volatile phenol levels in the wine than inoculated malolactic fermentation. The treatment with lees reduced the level of volatile phenols, probably due to absorption by yeast cells. The presence of the phenyl acrylic decarboxylase (PAD1) gene and the production of volatile phenols by S. cerevisiae commercial yeast strains were evaluated in Shiraz grape juice and in synthetic grape juice. The results indicated that the yeast strains differ in their ability to produce 4-vinylphenol and 4-vinylguaiacol. All the yeast strains tested had the PAD1 gene. We also evaluated the presence of the phenolic acid decarboxylase (padA) gene and the ability of different lactic acid bacteria strains to produce volatile phenols in synthetic wine media. Although some of these strains tested positive for the phenolic acid decarboxylase gene most of them only produced very low levels of volatile phenols. This study made a valuable contribution on the knowledge about the effect of Brettanomyces yeast on the volatile phenol content of red wines during different stages of the winemaking process and when applying different winemaking practices. It also showed the effect between Brettanomyces yeast and other wine microorganisms and the possible influence it could have on the final quality of wine. Research such as this can therefore aid the winemaker in making certain decisions when trying to manage Brettanomyces yeast spoilage of wines.

published_or_final_version / abstract / Botany / Master / Master of Philosophy

Many models for predicting volatile organic compounds (VOC) emissions from latex paints have been developed. Earlier models were developed for solvent-borne paints, particularly since these paints evaporate rapidly and can be modeled with simple decay models. However, paint has changed in the past fifty years, and a transition has been made towards water-borne paints. These paints were introduced for indoor applications because they lacked the health hazards and odors of their solvent-borne counterparts. These paints also have organic modifiers, therefore it is very important to predict how these modifiers evaporate from the coated material. New mechanistic models that can predict slow emitting VOCs over long periods of time are not available. An improved ability to predict VOC emissions from latex paints could lead to improved understanding, better policy-making and promotion of environmental regulations that benefit both the consumer and producers of architectural coatings. This research improves on existing models used to estimate VOC emissions off-gassed from latex paints. The developed two layer model (2LM) has a layer for paint and substrate material, and accounts for mass transfer at the paint layer, and diffusion transport between paint and material layers. The model provides a semi-mechanistic way to predict paint drying and VOC emissions from coatings on a variety of substrates. The model only requires the estimation of one parameter (the paint layer diffusion coefficient), unlike other models available that require multiple parameter estimations. This model is robust in the sense that it could be used to predict VOC emissions from paint, as well as predicting the variation of the internal VOC distribution on both paint and material layers with time. The model was tested and validated with empirical data collected from previous controlled chamber experiments, and also with data collected from short evaporation experiments. Critical paint components like polymer and pigment composition and its relation to VOC fate and transport after paint application, both initially and over long periods of time, were explored. Modeling results indicated that the diffusion coefficient of 2,2,4-trimethyl-1,3-pentadediol monoisobutyrate (TMPD-MIB) in the paint layer does not depend on the thickness of the wet paint film, but it depends on the pigment volume concentration (PVC) of the paint. Additionally, a constant diffusion coefficient used in the 2LM was successful for modeling emissions of TMPD-MIB from low pigment volume concentration (LPVC) paints, but it failed to capture the physical mechanisms of the drying film for high pigment volume concentration (HPVC) paints. A major finding from this research was that a detailed gas phase analysis of mass transport for TMPD-MIB would have negligible effects on the predicted overall evaporation rate. Therefore, the entire wet and dry emissions processes are likely dominated by diffusion processes. / text

Fractional crystallization, magma mixing, assimilation of continental crust, and how those processes modify volatile budgets, control the evolution of magma. As a consequence, the understanding of these processes, their magnitudes, and timescales is critical for interpreting ancient magma systems, their eruptions, and the potential future volcanic activity. In this dissertation I present the results of three projects. The first explores how magmatic processes affect magma reservoirs and eruption dynamics. The second explores where in the storage system and how often these processes occur. The third explores how volatile budgets are modified by processes such as crystallization, mixing, and assimilation. Volcán Popocatépetl (central México) erupted ~14100 14C yr BP producing the Tutti Frutti Plinian Eruption (TFPE). The eruption tapped two different silicic magmas that mixed just prior and during the eruption. The influx of mass and volatiles generated during the mixing of both magmas overpressured the reservoir, which was weakened at the top. The weakened reservoir relaxed while magma was tapped and collapsed to form a caldera at the surface. Although it is known that fractional crystallization, mixing, and assimilation can greatly modify magmas, the frequency and intensity of these events is not known. I investigated the magmatic processes responsible for the evolution of magmas erupted during five Plinian events of Popocatépetl volcano. Results show that during the last 23 ky magma was stored in two different zones, and was variably modified by replenishments of mafic magma. Interestingly, little evidence for large mafic inputs triggering explosive eruptions was found. Each of these processes alters the abundances of volatiles and introduces different types of volatiles to the system. Hence, the volatile budget of magma can have a rich and complex history. To investigate how volatile budgets evolve in active magma systems, I analyzed the abundances of volatiles (H2O, CO2, F, Cl, and S) in numerous glass inclusions trapped in phenocrysts. Results show that the magmas that produced the last five Plinian eruptions at Popocatépetl volcano evolved by crystallization and magma mixing, assimilation of the local carbonate basement is not chemically appreciable. Mixing with mafic magmas added substantial CO2 and S to the system, dewatered the magma, yet produced little change in the F contents of the magmas. / text

There is a need for chemical sensors for monitoring volatile organic compounds (VOCs) in air. Acute and chronic inhalation of toxic VOCs can cause adverse health effects in humans, so monitoring these analytes is important for ensuring that their concentrations are maintained below maximum permissible levels. Chemical sensors using polydimethylsiloxane (PDMS) to extract VOCs with partial selectivity, coupled with label-free optical detection methods based on refractive index, can overcome the limitations of conventional VOC detection methods. A variety of tunable and high refractive index PDMS materials were developed by incorporating a range of titanium and zirconium concentrations (2.5 – 30 mol % and 2.5 – 15 mol %, respectively) using a simple sol-gel synthesis and by incorporating a range of titanium concentrations (2.5 – 10 mol %) into naphthyl-functionalized PDMS. These materials ranged in refractive index from 1.4023 ± 0.0002 to 1.5663 ± 0.0001 at 635 nm and 1.3942 ± 0.0003 to 1.5510 ± 0.0007 at 1550 nm. The ability to use tunable refractive index PDMS films to differentiate between m-xylene and cyclohexane was demonstrated by monitoring changes in refractive index and thickness following absorption of these analytes using a refractometer at 1550 nm. The sensitivity of the refractive index response to an analyte using a particular PDMS film was dependent upon the difference between the refractive index of the analyte and film, as well as the film-air partition coefficient of the analyte. The detection limits for m-xylene and cyclohexane were 81 ppm and 4940 ppm, respectively, using PDMS-titanium-oxo nanocomposites with 5 and 10 mol % Ti, respectively. A simple planar waveguide sensor with an input grating coupler was developed to monitor changes in refractive index of the cladding through shifts in peak resonance wavelength. Using high refractive index PDMS materials as the waveguide core, we monitored changes in refractive index arising from absorption of VOCs into the grating. Here, the sensitivity of the waveguide response was dependent upon the difference in refractive index of the analyte and polymer, as well as the film-air partition coefficient of the analyte. The detection limits for m-xylene and cyclohexane were 1980 ppm and 18000 ppm, respectively. / Thesis (Master, Chemistry) -- Queen's University, 2013-08-24 11:45:57.642