Nanocrystalline beta-silicon carbide (ß-SiC) was synthesized at relatively low temperature (<1300C) by carbothermal reduction (CTR) reaction in fine scale carbon/silica mixtures. The fine scale mixing of the reactants (i.e., carbon and silica) was achieved by solution-based processing and subsequent heat treatment. The mechanism of the CTR reaction in the current system was investigated from different aspects. The condensates of the volatile species generated during the CTR reaction was collected and analyzed. The results supported previous investigations which suggested that the CTR reaction is a multi-step process that involves silicon monoxide (SiO) vapor as a reaction intermediate. The kinetics of the CTR reaction was investigated by isothermal weight loss study and by the study which determined the amount of SiC formed via quantitative X- ray diffraction (QXRD) analysis. The results of kinetic study were consistent with the "shrinking-core" model, in which the reaction between SiO vapor and carbon at the carbon surface to produce SiC is the rate-controlling step. In addition, several techniques, including XRD, gas adsorption analysis, laser diffraction particle size analysis, SEM, TEM, etc., had been used to study the structural evolutions of the reaction product of CTR. It was demonstrated that the evolutions of product structure characteristics such as crystallite size, specific surface area, specific pore volume, pore size distribution, particle size distribution, and powder morphology, etc. were consistent with each other and provided support to the reaction mechanism proposed.

Lead (Pb) is one of the most well known toxic heavy metals in human beings and animals, which leads to toxic neurological disorders, cognitive problems, learning and memory disabilities. Epidemiological studies revealed that chronic lead exposure is one of the environmental risk factors which may cause Alzheimer¡¦s Disease, which were speculated for the observation of cellular necrosis, apoptosis, and £]-amyloid deposition frequently occuring altogether after chronic lead exposure. Recent studies have shown that the £]-amyloid formed during autophagic turnover of APP-rich organelles supplied by both autophagy and endocytosis. Therefore, we will conduct the new perspective for studying the possible role of autophagy on amyloidogensis disorders after lead exposure. SH-SY5Y human neuroblastoma cells, used in this study, were differentiated to a neuronal phenotype by retinoic acid (RA) to the culture medium at 10 £gM for 1, 2, 3 and 4 days. Doses of lead acetate with of lead acetate were 5 £gM and applied to the neuronal culture and then cell viability measurement by MTT assay. The apoptotic effect of non-differentiation and differentiation neuroblastoma cells after lead exposure was determined by cleaved DNA fragments. Furthermore, APP, intracellular A£]1-40 and A£]1-42 expression were quantified by Real-time PCR and ELISA, respectively. The autophagy process and variation of total and phosphorylated mammalian target of rapamycin (mTOR) forms were determined after lead exposure in non-differentiation and differentiation neuroblastoma cells by western blot. The results indicate that lead exposure enhances autophagy response in both non-differentiation and differentiation SH-SY5Y cells, which might cause neuronal apoptosis associated with £]-amyloidgenesis. Otherwise, lead exposure resulted in the inhibition of mTOR signaling, which correlated with the autophagic process. Besides, in our studies, non-differentiated cells exhibited more toxic vulnerability than RA induced differentiated neuron is congruous to previous finding that lead exposure during fetal development might be a potential risk factor for AD in the adulthood.

Title from PDF of title page. / Document formatted into pages; contains 73 pages. / Thesis (M.S.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The goals of this research project were the design and construction of a carbon nanotube (CNT) reactor based on the plasma enhanced chemical vapor deposition (PECVD) principle and the development of a method for directed assembly of CNTs by catalyst patterning. PECVD was selected as the growth method due to the requirement of a catalyst for the growth process, thereby facilitating directed assembly and controlled diameter CNT growth at well-defined locations. The reactor was built in accord with horizontal flow design using standard ultra high vacuum components. The controllable parameters of the reactor include sample temperature, DC plasma intensity, chamber pressure, gas flow ratios, and total gas flow. The most favorable parameters for growing CNTs of well defined length, diameter, and separation were obtained by initially using parameter values obtained from literature, then optimized by changing a parameter and noting the effect on CNT growth. / ABSTRACT: Catalyst patterns for the directed assembly of CNTs were prepared by electron-beam lithography (EBL). Experiments were performed that demonstrated the feasibility of using lithographic methods to achieve directed assembly of carbon nanotubes for the manufacture of CNT devices. Experiments focusing on growth interruption and regrowth of CNTs were conducted to investigate methods of introducing tailored branching points into carbon nanotubes during the growth process. These experiments clearly demonstrate that growth interruption increases the occurrence of CNT branching. An analysis of the relationships between CNT diameter, branching points, and the number of growth steps was conducted. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Vor dem Hintergrund der in der Mikroelektronik-Fertigung heute verbreiteten Kupfertechnologie werden in der vorliegenden Arbeit drei neuartige metallorganische Verbindungen, nämlich phosphitstabilisierte Kupfer(I)-Trifluoracetat-Komplexe vorgestellt und hinsichtlich ihrer Anwendbarkeit für die chemische Gasphasenabscheidung (CVD) von Kupfer untersucht. Im einzelnen handelt es ich um die Substanzen Tris(trimethylphosphit)kupfer(I)trifluoracetat (METFA), Tris(triethylphosphit)kupfer(I)trifluoracetat (ETTFA) und Tri(tris(trifluorethyl)phosphit)kupfer(I)trifluoracetat (CFTFA). Mit den Substanzen erfolgen CVD-Experimente auf TiN und Cu bei Temperaturen &lt;400&deg;C. Die Precursoren werden dabei mittels eines Flüssigdosiersystems mit Verdampfereinheit der Reaktionskammer zugeführt. Während METFA wegen seiner ausreichend geringen Viskosität unverdünnt verwendet werden kann, kommen für ETTFA und CFTFA jeweils Precursor-Acetonitril-Gemische zum Einsatz. Mit keinem der Neustoffe können auf TiN geschlossene Kupferschichten erzeugt werden, während dies auf Kupferunterlagen in Verbindung mit Wasserstoff als Reduktionsmittel gelingt. Die Abscheiderate beträgt hierbei 2-3nm/min; der spezifische Widerstand der Schichten bewegt sich zwischen 4&mu;&Omega;cm und 5&mu;&Omega;cm. Mit allen Substanzen werden besonders an dünnen, gesputterten Kupferschichten Agglomerationserscheinungen und Lochbildung beobachtet. Im Fall von CFTFA treten zusätzlich Schäden am darunterliegenden TiN/SiO₂-Schichtstapel auf. Vergleichende Untersuchungen mit der für die Cu-CVD etablierten Substanz (TMVS)Cu(hfac) ergeben sowohl auf Cu als auch auf TiN geschlossene Kupferschichten. Dabei liegen die Abscheideraten bei Temperaturen zwischen 180&deg;C und 200&deg;C im allgemeinen deutlich über 100nm/min. Ein Vergleich dieser Resultate mit den Ergebnissen für die Neustoffe legt nahe, dass den untersuchten Kupfer(I)-Trifluoracetaten keine ausreichende Tauglichkeit für Cu-CVD-Prozesse in der Mikroelektronik-Technologie bescheinigt werden kann. Die im Vergleich zu (TMVS)Cu(hfac) höhere thermische Stabilität der Precursoren und ihre Fähigkeit, mit Wasserstoff als Reaktionspartner auf Cu geschlossene Kupferschichten erzeugen zu können, deutet jedoch auf ihre eventuelle Eignung für ALD-Prozesse hin. Daher widmet sich die Arbeit in einem abschließenden Kapitel dem Thema der Atomic Layer Deposition (ALD), wobei nach einem allgemeinen Überblick besonders auf für die Mikroelektronik relevante ALD-Prozesse eingegangen wird.

Diss. (sammanfattning) Uppsala : Univ., 2009. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 150-191).

Thesis (Ph.D.)--University of Central Florida, 2008. / Adviser: Sic L. Chan. Includes bibliographical references (p. 74-84).

Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Kiminobu Sugaya. Includes bibliographical references (p. 45-50).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 114-145).

A simple anaerobic digestion model has been developed for a continuously-stirred tank reactor (CSTR), which links the specific biogas production rate to the food/microorganism ratio (F/M). The model treats the various microbial populations involved in the sequential biological processes involved in anaerobic digestion as a composite and links the entire biomass specific growth rate directly to the specific biogas production rate. The model was calibrated by determining the specific gas production rate for a range of F/M values using a municipal wastewater seed sludge. The model predictions for steady-state biogas production rates were compared to observed biogas production and volatile solids destruction results from three laboratory-scale anaerobic digesters that were operated at hydraulic retention times of 10, 15, and 20 days. The F/M model results were shown to agree with reactor biogas output for 10, 15, and 20 day hydraulic retention times to within 5.0%, 14.3%, and 9.5%, respectively. A commercial wastewater treatment plant model, BioWin 3, was also used to model anaerobic digestion as a comparison. Agreement for the BioWin 3 model results, as compared to the 10, 15, and 20-day hydraulic retention time reactors, was within 66.2%, 114.1%, and 105.1%, respectively. In all cases the BioWin 3 model over-predicted biogas output as compared to the reactors. A molecular biology method called RT-RiboSyn was developed to measure the specific growth rate of microbial populations. RT-RiboSyn, is an ex situ method that utilizes a reverse transcription and primer extension (RT&PE) method to analyze the rRNA extracted from a time series of samples treated with chloramphenicol. The method measures the rate of ribosome synthesis over time through the increase in precursor 16S rRNA (pre16S rRNA) relative to the mature 16S rRNA (16S rRNA). A single fluorescently labeled primer that targets an interior region of both pre16S and 16S rRNA for a distinct population is used to generate two pools of reverse transcription product. The ratio of pre16S and 16S rRNA is then determined by separating these pools by length using capillary electrophoresis, and measuring the fluorescent intensity of each pool of fragments. Results from three different log growth cultures of Acinetobacter calcoaceticus indicate that RT-RiboSyn, as compared to spectrophotometer readings, was able to predict specific growth rates within -3.1% to 10% and -3.3% to 21.0% when using a primer targeting Eubacteria and Acinetobacter, respectively. The RT-RiboSyn results from a stationary phase culture predicted no growth and possible 16S rRNA degradation. Further work was completed to determine whether the RiboSyn method would successfully measure growth rates of specific microbial populations in environmental samples. The first of these was activated sludge from a high-purity oxygen system in a wastewater treatment facility located in Tampa, Florida. The organism targeted was the Acinetobacter genus, which was shown to be prevalent via fluorescence in situ hybridization results. RT-RiboSyn results indicated that growth was not measureable for the Acinetobacter present in the system; however, since the sludge was taken at the end of the process, Acinetobacter may have been in stationary phase when the samples were collected. Attempts were made to apply the method to methanogens in both pure culture and anaerobic digester sludge samples. An analysis of samples of RNA from Methanosarcina barkeri indicated that the presence of 16S rRNA could be measured; however, capillary electrophoresis instrument limitations prevented the detection of pre16S rRNA fragments. Additional testing of anaerobic digester sludge for both bacterial and Archaeal population was successful for detecting 16S rRNA and possibly precursor 16S rRNA fragments of a variety of lengths. However, specific growth rates could not be determined for the Archaea present in these samples, either due to capillary electrophoresis limitations or very slow growth rates. The results show that the RT-RiboSyn method is applicable to pure cultures; however, a modification of the method is needed to overcome the limitations apparent in populations with low specific growth rates.