8,191 research outputs found
Microscopic images of Dictyosphaeria ocellata (Howe 5090 and Howe 5585), New York Botanical Garden (NY)
No full textMicroscopic images of
Valonia ocellata M.Howe - M. A. Howe 5090, 1907-11-25, Bahamas, Watling Island, in the lagoon, 24.063924 -74.532563, New York Botanical Garden (NY) 00937651 (Holotype)
Valonia ocellata M.Howe – M.A. Howe 5585, 1907-12-16, Turks and Caicos Islands, Cockburn Harbor, South Caicos, B.W.I., 21.500434 -71.532698, New York Botanical Garden (NY) 0214087
Deep anisotropic dry etching of silicon microstructures by high-density plasmas
No full textThis thesis deals with the dry etching of deep anisotropic microstructures in monocrystalline silicon by high-density plasmas. High aspect ratio trenches are necessary in the fabrication of sensitive inertial devices such as accellerometers and gyroscopes. The etching of silicon in fluorine-based plasmas is isotropic. To obtain anisotropy the addition of sidewall passivation is necessary. This is achieved with both oxygen passivation at low temperatures and fluorocarbon passivation at room temperature. A quantitative approach was pursued to explain the etching mechanism. The etch results were analysed using the measured plasma species fluxes and the surface composition. Moreover, the transport of the plasma species in narrow anisotropic structures is a fundamental factor determining the etch rate and the profile evolution. The experimental methods such as the etching equipment, plasma diagnostics, surface analysis and sample preparation are described in chapter 2. Three etching processes were investigated: the cryogenic etching process with oxygen passivation at low temperatures, the Bosch process with fluorocarbon passivation at room temperature and the novel triple pulse process that was developed in our laboratory. The polymer deposition mechanism and the characteristic role of the ions are also explained. The cryogenic etching process is discussed in chapter 3. Fluorine radicals, oxygen radicals and ion bombardment are responsible for the three main sub-processes, that is, etching, sidewall passivation and depassivation of the trench bottom, respectively. Etching experiments with an extremely low ion-to-radical flux ratio were used to reveal the etching mechanism. Crystal orientation dependent etching leading to Si(111) crystal facets is observed in a surface kinetics controlled regime. By varying the plasma conditions it is possible to adjust the etching mechanism from fluorine-limited to ion-limited. Controlled etching is obtained because the etching is tuned from aspect ratio dependent in the fluorine-limited domain to aspect ratio independent in the ion-limited domain. The transport of radicals in high aspect ratio trenches is an important limiting factor and was investigated with special structures. The etch results are described by an analytic model that is based on the surface site balance of fluorine and oxygen radicals. The results are further explained with a Monte Carlo simulation model. The Bosch process is clarified in chapter 4. The anisotropy of the etched structures is controlled by balancing the etching and passivation pulse. However, the maximal obtainable aspect ratio is limited by convergence of the trench sidewalls due to excessive passivation. The maximal obtainable aspect ratio increases if the ion-to-radical flux ratio increases. The transport of ions is an important limiting factor in the depassivation of the bottom of the trench. Divergence of the ion beam leads to a reduction of the ion flux, so that the fluorocarbon passivation is insufficiently removed near the base of the sidewalls. The average ion angle was measured and correlated to the maximal obtainable aspect ratio. The Bosch process was improved at the depassivation side with the triple pulse process and at the passivation side with preferential sidewall deposition. The triple pulse process that is described in chapter 5 has the aim to improve the depassivation in deep trenches. The three main sub-processes are decoupled using a separate depassivation pulse directly after the etching and passivation pulses. The fluorocarbon passivation is efficiently removed with low-pressure, high-density, oxygen-based plasmas. The investigated plasma chemistries include O2, CO2 and SO2. The triple pulse process leads to better profile control with a straight trench bottom. However, the maximal obtainable aspect ratio is comparable to the Bosch process because a larger etch depth and a small lateral etch cancel out. The polymer deposition mechanism is treated in chapter 6 with the aim to understand the fluorocarbon passivation in deep trenches. The deposition on plane surfaces and on special structures was investigated to distinguish between the radical-induced and ion-enhanced components. A simple analytical model, which explains the main deposition characteristics, was developed. Preferential sidewall deposition is obtained for higher ion fluxes and higher bias voltages where sputtering plays an important role. In this case no fluorocarbon passivation has to be removed from the bottom of the trench. The trench profile was optimised in the Bosch process by tuning the bias voltage during etching and passivation independently. It resulted in perfectly anisotropic trenches but the maximal obtainable aspect ratio was still limited by a small lateral etch. The characteristic role of the ions in the etching mechanism is explained in chapter 7. Ion-induced etching of both SiC in a SF6-O2 plasma and Si in a Cl2 plasma were investigated. The impact of the ions on the profile evolution can be examined more explicitly because spontaneous chemical reactions are absent for these plasma-material systems. The etching mechanism varies from fluorine-limited to ion-limited depending on the radical-to-ion flux ratio. Microtrenches are observed for an ion-limited etching mechanism. Fluorine-limited SiC etching is aspect ratio dependent in contrast to ion-limited SiC etching, which is aspect ratio independent. The etching of high aspect ratio SiC structures is limited by the positive sidewall taper. This is presumably caused by insufficient removal of the thin fluorocarbon layer on the surface. Si etching in a Cl2 plasma is always aspect ratio independent in contrast to SiC etching because of the low reaction probability. The conclusions and recommendations of this thesis are given in chapter 8.Applied Science
Evaluation of polyphenol content and antioxidant activity of the hydroalcoholic extract of Eisenia cokeri m.a. howe
No full textWas aimed to evaluate the content of total polyphenols and the antioxidant activity of the rhizoid, thallid and phyloid extracts of the Eisenia cokeri M.A. Howe. Using spectrophotometric reference methods. The content of total polyphenols was determined by the Folin-Ciocalteau method from the reference material Gallic acid and the antioxidant activity is referred to 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and 2,2\u27 -azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) ABTS.+. The results obtained showed that the content of total polyphenols is 3.111346 mg for the estípite; 0.4625 mg for the fronda and 2.31665 mg for the gallic acid rhizoid / 1 gram sample. For the antioxidant activity the extracts showed antioxidant activity in the DPPH methods for the rhizoid (IC50 = 659.74 μg / mL): for the fronda (IC50 = 280.00 μg / mL) and for the estípite (IC50 = 248, (IC50 = 20.3 μg / mL), and for the fronda (IC50 = 39.2 μg / mL) and for the estípite (IC50 = 50 μg / mL) 24.7 μg / mL). The obtained results show that the content of polyphenols is related very well to the antioxidant activity shown by the samples studied.Se tuvo como finalidad evaluar el contenido de polifenoles totales y la actividad antioxidante de los extractos rizoide, estípite y fronda del alga Eisenia cokeri M.A. Howe, mediante métodos de referencia espectrofotométricos. El resultado de polifenoles de las algas se determinó por el método de Folin-Ciocalteau a partir del estándar de referencia Ácido gálico y la actividad antioxidante es referida a los radicales libres fue determinado por los métodos de 1,1-difenil-2-picrilhidrazil (DPPH) y el ácido 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) ABTS.* . La conclusión fue que el contenido de polifenoles totales es de 3,11346 mg para el estípite; 0,4625 mg para la fronda y 2,31665 mg para el rizoide de ácido gálico/1 gramo de muestra. Para la actividad antioxidante los extractos mostraron actividad antioxidante en los métodos de DPPH para el rizoide (IC50= 659,74 μg/mL): para la fronda (IC50= 280,00 μg/mL) y para el estípite (IC50= 248,50 μg/ mL) y por el método de ABTS.+ los extractos mostraron para el rizoide (IC50= 20,3 μg/mL): para la fronda (IC50= 39,2 μg/ mL) y para el estípite (IC50= 24,7 μg/mL). Estos resultados se correlacionan con los de la actividad antioxidante mostrada por las muestras estudiadas
Paintings by Oscar Howe before the Annual National Indian Painting Competition at the Philbrook Museum of Art, 1958
No full textix, 68 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.In 1958 Yanktonai Sioux painter Oscar Howe's (1915-1983) submission to the
Annual National Indian Painting Competition at the Philbrook Museum of Art was
rejected for deviating too far from the established conventions of "traditional Indian
painting." Howe's innovative use of style and his subsequent declarations against the
premises of his rejection established the artist as a major figure in the development of
Native American painting in the twentieth century. The existing literature on Howe is
predominantly biographical and lacks contextual or stylistic analysis. In particular, an
under-analyzed relationship is prevalent between his mature style and his early works.
This thesis aims to address the social, cultural, educational, political, and stylistic
influences that prepared the artist to evolve the formal aspects of his painting. This
discussion will expand the discourse on Howe by revealing trends of continuity in the
artist's transition from his earlier style to an experimental style and showing that neither
is without the influence of the other.Committee in Charge:
Leland M. Roth, Chair;
Joyce Cheng;
Brian Klopote
Determinación de polifenoles, actividad antioxidante, antielastasa, anticolagenasa y elaboración de una fórmula dermocosmética a partir del extracto hidroalcohólico de Eisenia cokeri M.A. Howe
Get PDFEvalúa el contenido de polifenoles totales, la actividad antioxidante, antielastasa, anticolagenasa, además de la acción fotoprotectora en una crema dermocosmética a partir de los extractos de rizoide, estípite y fronda del alga Eisenia cokeri M.A. Howe, mediante métodos de referencia espectrofotométricos. El contenido de polifenoles de las algas se determinó por el método de Folin-Ciocalteau a partir del material de referencia ácido gálico y la actividad antioxidante referida a los radicales libres 1,1-difenil2-picrilhidrazil (DPPH) y ácido 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) ABTS. +. Los resultados obtenidos mostraron que el contenido de polifenoles totales es de 3,11346 mg para el estípite; 0,4625 mg para la fronda y 2,31665 mg para el rizoide en ácido gálico/ gramo de muestra. Para la actividad antioxidante los extractos mostraron actividad antioxidante por los métodos de DPPH para el rizoide IC50= 65,974 µg/mL; para la fronda IC50= 280,00 µg/mL y para el estípite IC50= 248,50 µg/mL. Por el método de ABTS. + los extractos mostraron para el rizoide IC50= 20,3 µg/mL; para la fronda IC50= 39,2 µg/mL y para el estípite IC50= 24,7 µg/mL. Los resultados obtenidos manifiestan que el contenido de polifenoles se relaciona muy bien con la actividad antioxidante mostrada por las muestras estudiadas. Para la actividad antielastasa, los extractos mostraron una actividad por el método de Thring para la inhibición de enzima elastasa de galato de epigalocatequina (EGCG) y de los extractos hidroalcohólicos; estos mostraron para la sustancia patrón EGCG un IC50 igual a 12 µg/mL y para los extractos de rizoide 6,7; estípite 47 788 y fronda 9 607 µg/mL, respectivamente. Con relación al porcentaje de inhibición de enzima colagenasa de galato de epigalocatequina (EGCG) y de los extractos hidroalcohólicos; estos mostraron los siguientes resultados: para el rizoide 83,60; estípite 106,281 y para fronda 113,87 µg/mL; siendo para el EGCG 216,991 µg/mL. Se realizó la prueba del efecto fotoprotector del extracto de rizoide, presentando las mejores condiciones en contenido de polifenoles, efecto antioxidante, antielastasa y anticolagenasa. De las cremas elaboradas al 1,3, y 5% con el extracto, la que más se aproxima a las características de uso de la crema comercial, usado como referencia; es la crema al 5%; concluyéndose que con este extracto hidroalcohólico de Eisenia cokeri M.A. Howe y que se puede elaborar una crema dermocosmética con este extracto.Tesi
Assessment of Models for Near Wall Behavior and Swirling Flows in Nuclear Reactor Sub-system Simulations
No full textAccurate simulation of turbulence remains one of the most challenging problems in nuclear reactor analysis and design. Due to limitations in computing resources, Reynolds averaged Navier Stokes models (RANS) continue to play an important role in reactor simulations. The Consortium for advanced simulations of light water reactors (CASL) is a Department of Energy technology hub that is investing in research and developmentof a state-of-the-art computational fluid dynamics capabilityto meet the challenges of turbulent simulation of nuclear reactors. In this presentation, we assess several RANS eddy viscosity models appropriate for single-phase incompressible turbulent flows. Specifically, we compare the single equation Splalart-Allmaras to several variations of the model. The assessment takes into consideration elements of full system reactor cores such as complex geometries, heterogeneous meshes, swirling flow, near wall flow behavior, heat transfer and robustness issues. The goal of this strategically oriented assessment is to provide an accurate and robust turbulent simulation capability for the CASL community. Metrics of performance will be constructed by comparing different models on a strategically chosen set of problems that represent reactor core sub-systems
O zarubežnoj dejatel'nosti professora M.A. Kumaxova
No full textOn professor M.A. Kumakhov's work and research abroad (in Russian)
Professor Mukhadin A. Kumakhov and the author collaborated in the area of Northwest Caucasian languages under a period from 1991 to 2008. The fruitful collaboration at Lund and Malmö universities resulted in three joint monographs and a number of articles, which is outlined in the article. Mukhadin A. Kumakhov became Honorary Doctor of the Philosophical Faculty of Lund University in 1998
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