Neste trabalho foi estudado o crescimento de fibras da matriz LiLa(WO4)2 (LLW) pura e co-dopada com íons Yb3+ e Er3+ via micro pulling-down. Foram crescidas fibras homogêneas e transparentes de LiLa(WO4)2:Yb3+:Er3+ com teor de dopante de 2, 5, 7, 10 e 15 mol% de Yb3+, todas co-dopadas com teor de 0,5 mol% de Er3+, com 1mm de diâmetro e até 22 mm de comprimento. Partindo-se da dopagem de 20 mol% não foi possível o crescimento de fibras com a mesma qualidade das demais, ocorrendo segregação e, possivelmente, formação de fase secundária. A temperatura de fusão dos compostos diminui com a adição de Yb3+, indo de 1020°C para o LLW puro, para 991°C com dopagem de 20 mol%. Para a análise de espectroscopia de emissão, as fibras foram excitadas com laser na região do infravermelho em 972 nm, sendo observada a emissão dos íons Er3+ via conversão ascendente. Foram observadas emissões referentes às transições 4S3/2 → 4I15/2 (centroide em 550 nm), 2H11/2 → 4I15/2 (527 nm) e 4F9/2 → 4I15/2 (653 nm); sendo a primeira a mais intensa. A eficiência de emissão aumentou de ~7% para a fibra pura, para 36% na fibra com 15 mol% de Yb3+. Foi encontrado que, para a maior intensidade de emissão, a quantidade ideal de Yb3+ deve ser de 11,5 mol%. / In the current work, was studied the growth of pure and Yb3+ and Er3+-doped LiLa(WO4)2 (LLW) by micro pulling-down technique. Were grown homogeneous and transparent fibers of Yb3+:Er3+:LiLa(WO4)2 with a dopant content of 2, 5, 7, 10 and 15 mol% of Yb3+, all co-doped with 0.5 mol% Er3+, 1 mm diameter and up to 22 mm length. It was not possible grow fibers with 20 mol% of Yb3+ due segregation and, possibly, formation of secondary phases. Noticed the melting temperature of the doped compounds decreases with the addition of Yb3+, from 1020 °C (pure LLW) to 991 °C (20 mol% Yb-doped). For emission studies, the fibers were excited in the infrared region at 972 nm and up conversion emission of Er3+ ions was registered. Emissions referring to transitions 4S3/2 → 4I15/2 (centroid at 550 nm), 2H11/2 → 4I15/2 (527 nm) and 4F9/2 → 4I15/2 (653 nm) were observed; the first one being the most intense. Emission efficiency increased from ~ 7% in pure fiber to 36% in doped fiber with 15 mol% of Yb3+. It was found that, for the highest emission intensity, the ideal amount of Yb3+ should be 11.5 mol%.

Neste trabalho foi estudado o crescimento de fibras da matriz LiLa(WO4)2 (LLW) pura e co-dopada com íons Yb3+ e Er3+ via micro pulling-down. Foram crescidas fibras homogêneas e transparentes de LiLa(WO4)2:Yb3+:Er3+ com teor de dopante de 2, 5, 7, 10 e 15 mol% de Yb3+, todas co-dopadas com teor de 0,5 mol% de Er3+, com 1mm de diâmetro e até 22 mm de comprimento. Partindo-se da dopagem de 20 mol% não foi possível o crescimento de fibras com a mesma qualidade das demais, ocorrendo segregação e, possivelmente, formação de fase secundária. A temperatura de fusão dos compostos diminui com a adição de Yb3+, indo de 1020°C para o LLW puro, para 991°C com dopagem de 20 mol%. Para a análise de espectroscopia de emissão, as fibras foram excitadas com laser na região do infravermelho em 972 nm, sendo observada a emissão dos íons Er3+ via conversão ascendente. Foram observadas emissões referentes às transições 4S3/2 → 4I15/2 (centroide em 550 nm), 2H11/2 → 4I15/2 (527 nm) e 4F9/2 → 4I15/2 (653 nm); sendo a primeira a mais intensa. A eficiência de emissão aumentou de ~7% para a fibra pura, para 36% na fibra com 15 mol% de Yb3+. Foi encontrado que, para a maior intensidade de emissão, a quantidade ideal de Yb3+ deve ser de 11,5 mol%. / In the current work, was studied the growth of pure and Yb3+ and Er3+-doped LiLa(WO4)2 (LLW) by micro pulling-down technique. Were grown homogeneous and transparent fibers of Yb3+:Er3+:LiLa(WO4)2 with a dopant content of 2, 5, 7, 10 and 15 mol% of Yb3+, all co-doped with 0.5 mol% Er3+, 1 mm diameter and up to 22 mm length. It was not possible grow fibers with 20 mol% of Yb3+ due segregation and, possibly, formation of secondary phases. Noticed the melting temperature of the doped compounds decreases with the addition of Yb3+, from 1020 °C (pure LLW) to 991 °C (20 mol% Yb-doped). For emission studies, the fibers were excited in the infrared region at 972 nm and up conversion emission of Er3+ ions was registered. Emissions referring to transitions 4S3/2 → 4I15/2 (centroid at 550 nm), 2H11/2 → 4I15/2 (527 nm) and 4F9/2 → 4I15/2 (653 nm) were observed; the first one being the most intense. Emission efficiency increased from ~ 7% in pure fiber to 36% in doped fiber with 15 mol% of Yb3+. It was found that, for the highest emission intensity, the ideal amount of Yb3+ should be 11.5 mol%.

Neste trabalho, foi investigado o processo de crescimento de fibras monocristalinas (FMc) para aplicação em sistemas laser. Para o aperfeiçoamento na fabricação de FMc de fluoretos, foi projetada e construída uma nova câmara de crescimento para um forno comercial de micro-pulling down (μ-PD), permitindo um rígido controle da atmosfera de processamento, (sob vácuo, fluxo e atmosferas estáticas). Paralelamente, foi investigado o processo de crescimento de FMc de molibdatos duplos de terras raras, sendo crescidas e caracterizadas fibras puras e dopadas com Nd3+ do composto LiLa(MoO4)2 (LLM) com concentrações na faixa de 0,5 a 10mol%. A câmara de crescimento projetada para o controle de atmosfera foi avaliada em diversas condições de operação. Em particular, a mesma foi testada com o puxamento de fibras de LiF, sob atmosfera de CF4, para observação da sua eficiência no controle da atmosfera de crescimento. Foram obtidas FMc de LLM, homogêneas e transparentes; nas fibras puras foi observada a presença de facetas, entretanto, a adequação dos parâmetros de crescimento e a adição de dopantes permitiu a redução significativa destes defeitos. A difração de raios-x mostrou a cristalização no grupo espacial I41/a; medidas de tomografia por coerência ótica permitiram a detecção de centros de espalhamento em regiões onde ocorreram instabilidades no processo de crescimento. Foi possível observar que o coeficiente de segregação do íon Nd3+ é próximo à unidade nesta matriz. O ganho potencial para ação laser foi determinado utilizando-se uma solução numérica das equações de taxa do sistema em 805nm e regime CW. O ganho máximo da emissão laser em 1,064 μm foi previsto para a dopagem de 5% mol Nd3+. / In this work we investigated crystal growth procedures aiming the development of single crystal fiber (SCF) for laser applications. For quality optimization in the fabrication of fluorides SCF a new growth chamber for a micro-pulling down furnace (μ-PD) was constructed targeting the fibers fabrication with strict atmosphere control (high vacuum, gas flux and static atmospheres). Simultaneously, the SCF growth process of rare earth double molybdates was studied. The growth of pure and Nd3+-doped SCF of LiLa(MoO4)2 (LLM) was studied in the range of 0,5 - 10mol% doping. The designed furnace growth chamber with controlled atmosphere was successfully constructed and tested under different conditions. Specially, it was tested with the growth of LiF SFC under CF4 atmosphere showing the expected results. Transparent and homogeneous SCF of Nd:LLM were grown. In the pure fibers was observed facets formation, however, these defects were minimized after tuning of the growth parameters and additionally with the fibers doping. X-ray analysis showed the crystallization of a single phase (space group I41/a); the optical coherence tomography showed the presence of scattering centers only in regions were some growth stability occurred due to the manual process control. The measured Nd3+ distribution showed uniform incorporation, indicative of a segregation coefficient close to unity in LLM. The potential laser gain of the system was determined using a numerical solution of the rate equations system for the 805nm, CW pumping regime, showing the maximum laser emission gain at 1.064 μm for a Nd3+-doping of 5mol%.

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Trichotillomania (TTM) is currently classified as an impulse disorder in the DSM-IV, but there is a growing consensus amongst researchers that trichotillomania should be placed on the putative QCD-related disorders spectrum. QCD and TTM have been compared in many fields including neurobiology, phenomenology and epidemiology. Studies of cognition in QCD and TTM typically focus on automatic thoughts and underlying assumptions and there is a paucity of research into enduring cognitive structures, or schemas, associated with the two disorders. This thesis reviews the available evidence regarding the relationship between QCD and TTM. The Young Schema Questionnaire (YSQ) was used to measure 15 maladaptive schemas in 96 QCD patients, 34 TTM patients, and 94 controls. In the comparison between QCD and TTM it was found that depression has a major impact on the profile of schemas in QCD. When controlling for depression a few differences in schema profile were found between QCD and TTM, though the schema enmeshment emerged as significant in both disorders. These findings are discussed in the light of the debate around the classification of trichotillomania in the psychiatric nomenclature. / Thesis (M.A.)-University of Natal, Pietermaritzburg, 2003.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Robert F. Simons, Dept. of Psychology. Includes bibliographical references.

Sculpting membranes into dynamic, curved shapes is central to intracellular cargo trafficking and other cellular functions. However, generation of membrane curvature during trafficking involves lipids and membrane-associated proteins; current mechanisms focus on creating rigid cages, curved scaffolds, or membrane surface area changes by proteins. This dissertation provides an alternative mechanistic example for the control of membrane deformations, involving modulation of membrane material properties. Sar1, a GTPase of the COPII family, regulates vesicle trafficking from the endoplasmic reticulum. We find that Sar1p lowers the rigidity of the lipid bilayer membrane to which it binds. We examine the behavior of Saccharomyces cerevisiae Sar1 (Sar1p) and Homo sapiens paralogs of Sar1 (Sar1A and Sar1B). Like Sar1p, human Sar1s lower membrane rigidity. Unlike Sar1p, the rigidity is not a monotonically decreasing function of concentration. At high concentrations, we find increased bending rigidity and decreased protein mobility. These features imply a model in which human Sar1 clustering governs membrane mechanical properties. Membrane rigidity measurements remain rare, however, and show a large variance, a situation that can be addressed by improving techniques and comparing disparate techniques applied to the same systems. I introduce applying selective plane illumination microscopy (SPIM) to image thermal fluctuations of giant vesicles. SPIM's optical sectioning enables high-speed fluorescence imaging of freely suspended vesicles and quantification of edge localization precision, yielding robust fluctuation spectra and rigidity estimates. For lipid-only membranes and membranes bound by the intracellular trafficking protein Sar1p, we show rigidity values from giant unilamellar vesicle fluctuations in close agreement with those derived from our independent assay based on membrane tether pulling. We also show that a model of homogeneous quasi-spherical vesicles poorly fits fluctuation spectra of vesicles bound by Sar1A at high concentrations, suggesting that SPIM-based analysis can offer insights into spatially inhomogeneous properties. I conclude by discussing our current work on amphipathic alpha helices, their ability to reduce membrane rigidity, and our hopes to create artificial helical structures capable of mimicking trafficking systems. Supplemental videos represent membrane disintegration with Sar1p and fluctuations of membrane only and Sar1p incubated vesicles. This dissertation contains previously published co-authored material.

Master of Science / Department of Electrical and Computer Engineering / W. B. Kuhn / An analysis of frequency pulling in a varactor-tuned LC VCO under coupling from an on-chip PA is presented. The large-signal behavior of the VCO's inversion-mode MOS varactors is outlined, and the susceptibility of the VCO to frequency pulling from PA aggressor signals with various modulation schemes is discussed. We show that if the aggressor signal is aperiodic, band-limited, or amplitude-modulated, the varactor-tuned LC VCO will experience frequency pulling due to time-modulation of the varactor capacitance. However, if the aggressor signal has constant-envelope phase modulation, VCO pulling can be eliminated, even in the presence of coupling, through careful choice of VCO frequency and divider ratio. Additional mitigation strategies, including new inductor topologies and system-level architectural choices, are also examined. The analysis is then applied to improve a fully-integrated half-duplex UHF micro- transceiver in which signal coupling between the LO and PA caused frequency pulling that prevented the use of QPSK signaling at certain data rates. We determine that a VCO operating at 4x transmit frequency will be naturally insensitive to pulling from QPSK signals. To validate the proposed solution, a prototype IC containing a pair of QPSK transmitters with integrated 100mW Class-C PAs was designed and fabricated in 0.18um SOI. The transmitters--one utilizing a 2x VCO, one utilizing a 4x VCO-- were designed to closely match the performance of the original microtransceiver when transmitting QPSK data. The transmitter with the 2x VCO experienced frequency pulling from the PA while transmitting QPSK data, but the transmitter with the 4x VCO did not, thereby confirming the analysis in this work. A revision of the microtransceiver was designed in 0.5 [mu]m SOS utilizing an off- chip PA inductor to reduce signal coupling with the VCO. A second revision of the microtransceiver with two prototype transmitters was designed in 0.25 [mu]m SOS uti- lizing 4x VCOs and figure-8 VCO inductors for maximum insensitivity to pulling from QPSK and band-limited modulation, as well as other design improvements that leverage the higher f[subscript]t of the smaller process. Both revisions also include a hardware FSK modulator, a new charge pump, and a redesigned fractional-N synthesizer to attenuate a divided-reference spur in the IF output. These revisions of the radio will enable future researchers to focus on system-level applications where highly-integrated medium-power transceivers with fully-functioning IQ modulation are needed.

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