3114 Optical zone centration of excimer laser photo-refractive keratectomy for myopia relative to the pupil with and without the use of an active eye tracking system

Explosive volcanic eruptions can eject large quantities of particulate matter that, along with other aerosol droplets and trace gases, are carried upwards into the atmosphere by the buoyant eruption column and then dispersed by winds aloft. The presence in the atmosphere of volcanic ash is a sporadic yet important factor that can threaten human health, affect the urban built environment, disrupt aerial navigation and, for very large eruptions, alter both atmospheric composition and chemistry. Once volcanic ash is injected into the atmosphere, it can be transported over great distances, even circumnavigating the entire planet. Volcanic ash modeling systems are used to simulate the atmospheric dispersion of volcanic ash and to generate operational short-term forecasts to support civil aviation and emergency management. The efficiency of response and mitigation actions is directly associated to the accuracy of the volcanic ash cloud detection. Volcanic ash modeling systems normally require an emission or source term model to characterize the eruption column; a dispersal model to simulate the atmospheric transport, dispersion and ground deposition of ash particles; and a meteorological model for the description of the atmospheric conditions. Traditional forecasts for volcanic ash build on off-line coupled modeling systems, where meteorological variables are only updated at the specified coupling intervals. Although this approach is computationally advantageous is some cases, there is a concern that it can lead to a number of accuracy issues and limitations that can be corrected by on-line modeling strategies. Despite these concerns, to date, no on-line coupled model is available for operational forecast of volcanic ash. In addition, the quantification of the limitations associated to the off-line systems has received no attention. This Ph.D. thesis describes and evaluates NMMB-MONARCH-ASH, a novel fully coupled on-line multiscale meteorological and atmospheric transport model designed to predict ash cloud trajectories, concentration of ash at relevant flight levels, and the expected deposit thickness for both regional and global domains in research and operational set-ups. The first activity targeted a model validation against several well-characterized events including, the Mt. Etna 2001, Eyjafjallajökull 2010, and Cordón Caulle 2011 eruptions. The model has shown to be robust, scalable, and capable to reproduce the spatial and temporal dispersal variability of the ash cloud and tephra deposits, showing promising results and improving the performance from well-known off-line operational models. The second activity quantified the model shortcomings and systematic errors associated to traditional off-line forecasts employed in operational set-ups. NMMB-MONARCH-ASH demonstrated that off-line forecasts could fail to reproduce up to 45-70% of the ash cloud of an on-line forecast, considered to be the best estimate of the true outcome. The uncertainty associated to off-line systems was found to be as relevant (same order of magnitude) as those uncertainties attributed to the source term. The third activity focused on a global application of NMMB-MONARCH-ASH to analyze the potential impacts of ash dispersal from Antarctic volcanoes. Numerical simulations suggested that volcanic ash emitted from Antarctic volcanoes could potentially encircle the globe, leading to significant consequences for global aviation safety. The last activity included a novel computational inversion method to account, for the first time, for the Plinian and co-ignimbrite phases of the 39 ka Campanian Ignimbrite super-eruption. This particular application employed the off-line coupled FALL3D model, found to be more suitable from a computational point of view. The outcome of this Ph.D. thesis encourages operational groups responsible for real-time advisories for aviation to consider using computationally efficient on-line coupled ash dispersal models.Las erupciones volcánicas explosivas pueden emitir una gran cantidad de material que, junto con otros aerosoles y gases traza, son inyectados en la atmósfera por la columna eruptiva para luego ser dispersados por los vientos en altura. La presencia en la atmósfera de cenizas volcánicas es un factor esporádico aunque importante, que puede llegar a amenazar la salud humana, afectar las infraestructuras urbanas, interrumpir la navegación aérea y, en el caso de grandes erupciones, alterar la composición atmosférica y química. Una vez en la atmósfera, la ceniza puede ser transportada a grandes distancias, llegando incluso a circunnavegar todo el planeta. Los sistemas de modelado de cenizas volcánicas se utilizan para simular la dispersión atmosférica de estas partículas, y para generar pronósticos operacionales a corto plazo empleados para dar soporte a la aviación civil y a la gestión de emergencias. La eficacia para responder a estos eventos está directamente asociada a la precisión de los modelos de transporte de cenizas volcánicas. Los sistemas de modelado de cenizas volcánicas requieren de un modelo de emisión de partículas para la caracterización de la columna eruptiva; un modelo de dispersión para la simulación del transporte atmosférico y la deposición de cenizas; y de un modelo meteorológico para la descripción de las condiciones atmosféricas. Los pronósticos tradicionales se basan en sistemas de modelado desacoplados (off-line), donde las variables meteorológicas sólo se actualizan a intervalos de tiempo especificados. Aunque este enfoque presenta ventajas desde el punto de vista computacional, existe la preocupación de que puede estar asociado a limitaciones y problemas de precisión que, por el contrario, pueden ser corregidos mediante estrategias de modelado acoplado (on-line). A pesar de estas preocupaciones, hasta la fecha no hay un modelo acoplado on-line disponible para el pronóstico operativo de la cenizas volcánicas. Además, tampoco existe una cuantificación de las limitaciones asociadas a los sistemas off-line. Este doctorado describe y evalúa NMMB-MONARCH-ASH, un modelo de transporte meteorológico y atmosférico multiescalar (regional/global) completamente acoplado on-line, para su uso en investigación y predicción operacional. El modelo está diseñado para predecir trayectorias de cenizas volcánicas, concentración de ceniza en niveles de vuelo (flight levels), y el correspondiente espesor de depósito. La primera actividad de esta tesis se centra en la validación de modelo mediante erupciones bien caracterizadas (Mt. Etna 2001, Eyjafjallajökull 2010, y del Cordón Caulle 2011). El modelo ha demostrado ser robusto, escalable y capaz de reproducir la variabilidad de la dispersión espacial y temporal de los depósitos y de las nubes de ceniza, ostrando resultados prometedores y mejorando el rendimiento de modelos operacionales. La segunda actividad cuantifica los errores sistemáticos asociados a los pronósticos off-line. NMMB-MONARCH-ASH demuestra que estps pronósticos podrían no reproducir hasta un 45-70% de la nube de cenizas de un pronóstico on-line, considerado éste último como la mejor estimación de la realidad. Esta actividad concluye que la incertidumbre asociada a los sistemas off-line puede llegar a ser tan relevante como aquellas incertidumbres atribuidas al término fuente. La tercera actividad se centra en una aplicación global de NMMB-MONARCH-ASH para analizar los posibles impactos asociados a la dispersión de ceniza de volcanes antárticos. Los resultados alertan de las posibles consequencias de estas erupciones en la aviación a nivel mundial . La última actividad incluye un nuevo método de inversión computacional para identificar, por primera vez, las fases Pliniana y coignimbrita de la super-erupción de la Ignimbrita Campaniana (39 ka) con FALL3D. Los resultados de este Ph.D. alientan a considerar el uso de modelos acoplados on-line para generar pronósticos operacionales de ceniza volcánica

Microscopic origin of the mobility enhancement at a spinel/perovskite oxide heterointerface revealed by photoemission spectroscopy

The spinel/perovskite heterointerface $\gamma$-Al$_2$O$_3$/SrTiO$_3$ hosts a two-dimensional electron system (2DES) with electron mobilities exceeding those in its all-perovskite counterpart LaAlO$_3$/SrTiO$_3$ by more than an order of magnitude despite the abundance of oxygen vacancies which act as electron donors as well as scattering sites. By means of resonant soft x-ray photoemission spectroscopy and \textit{ab initio} calculations we reveal the presence of a sharply localized type of oxygen vacancies at the very interface due to the local breaking of the perovskite symmetry. We explain the extraordinarily high mobilities by reduced scattering resulting from the preferential formation of interfacial oxygen vacancies and spatial separation of the resulting 2DES in deeper SrTiO$_3$ layers. Our findings comply with transport studies and pave the way towards defect engineering at interfaces of oxides with different crystal structures.Comment: Accepted as Rapid Communications in Physical Review

Dynamic Singularities in Cooperative Exclusion

We investigate cooperative exclusion, in which the particle velocity can be an increasing function of the density. Within a hydrodynamic theory, an initial density upsteps and downsteps can evolve into: (a) shock waves, (b) continuous compression or rarefaction waves, or (c) a mixture of shocks and continuous waves. These unusual phenomena arise because of an inflection point in the current versus density relation. This anomaly leads to a group velocity that can either be an increasing or a decreasing function of the density on either side of these wave singularities.Comment: 4 pages, 4 figures, 2 column revtex 4-1 format; version 2: substantially rewritten and put in IOP format, mail results unchanged; version 3: minor changes, final version for publication in JSTA

Unveiling the Impact of Morphine on Tamoxifen Metabolism in Mice in vivo

Background- Tamoxifen is used to treat breast cancer and cancer recurrences. After administration, tamoxifen is converted into two more potent antitumor compounds, 4OH-tamoxifen and endoxifen by the CYP3A4/5 and 2D6 enzymes in human. These active compounds are inactivated by the same UDP-glucuronosyltransferases isoforms as those involved in the metabolism of morphine. Importantly, cancer-associated pain can be treated with morphine, and the common metabolic pathway of morphine and tamoxifen suggests potential clinically relevant interactions. Methods- Mouse liver microsomes were used to determine the impact of morphine on 4OH-tamoxifen metabolism in vitro. For in vivo experiments, female mice were first injected with tamoxifen alone and then with tamoxifen and morphine. Blood was collected, and LC-MS/MS was used to quantify tamoxifen, 4OH-tamoxifen, N-desmethyltamoxifen, endoxifen, 4OH-tamoxifen-glucuronide and endoxifen-glucuronide. Results- In vitro, we found increased Km values for the production of 4OH-tamoxifen-glucuronide in the presence of morphine, suggesting an inhibitory effect on 4OH-tamoxifen glucuronidation. Conversely, in vivo morphine treatment decreased 4OH-tamoxifen levels in the blood while dramatically increasing the formation of inactive metabolites 4OH-tamoxifen-glucuronide and endoxifen-glucuronide. Conclusions- Our findings emphasize the need for caution when extrapolating results from in vitro metabolic assays to in vivo drug metabolism interactions. Importantly, morphine strongly impacts tamoxifen metabolism in mice. It suggests that tamoxifen efficiency could be reduced when both drugs are co-administered in a clinical setting, e.g. to relieve pain in breast cancer patients. Further studies are needed to assess the potential for tamoxifen-morphine metabolic interactions in humans

Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO3 ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading microscopic mechanisms, i.e., a dimensionality-induced readjustment of octahedral rotations, magnetism, and electronic correlations. The astonishing resemblance of the band structure in the two-dimensional limit to that of bulk Sr2IrO4 opens new avenues to unconventional superconductivity by "clean" electron doping through electric field gating

Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph

We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were obtained as part of a coordinated observing program including X-ray observations with the Chandra/High Energy Transmission Grating (HETG) Spectrometer and Suzaku. We detected nine kinematic components of UV absorption, which were previously identified using the HST/Space Telescope Imaging Spectrograph. None of the absorption components showed evidence for changes in column density or profile within the \sim 10 yr between the STIS and COS observations, which we interpret as evidence of 1) saturation, for the stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the weaker components. After applying a +200 km s^-1 offset to the HETG spectrum, we found that the radial velocities of the UV absorbers lay within the O VII profile. Based on photoionization models, we suggest that, while UV components 2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray absorption detected in the HETG analysis occurs in more highly ionized gas. Moreover, the mass loss rate is dominated by high ionization gas which lacks a significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical Journa

Laser treatment in diabetic retinopathy

Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferative diabetic retinopathy (NPDR) under certain conditions. For clinically significant macular edema the Early Treatment of Diabetic Retinopathy Study could show that immediate focal laser photocoagulation reduces the risk of moderate visual loss by at least 50%. When and how to perform laser treatment is described in detail, offering a proven treatment for many problems associated with diabetic retinopathy based on a high evidence level. Copyright (c) 2007 S. Karger AG, Basel

A Cell of One’s Own? Incarceration and Other Turning Points in Women’s Journeys to Desistance

Research has shown the importance of turning points in desistance from criminal behavior. Using qualitative data from a sample of 100 formerly incarcerated mothers interviewed about their criminal behavior, this article explores their descriptions of transition moments and whether and how those moments affected their criminal behavior. The findings indicate that whereas parenting emerges as a turning point, the practical difficulties of reentry may reduce the impact of mothering on women’s desistance. More self-focused turning points, such as those due to incarceration, arrest, and sobriety appeared to be particularly important to the women’s desistance. This article emphasizes the need for research into the subjective and environmental factors that affect women’s desistance behaviors

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC11763 using XMM-Newton data

Aims. The detailed analysis of all data taken by the XMM-Newton satellite of UGC11763 to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus. Methods. The continuum emission was studied through the EPIC spectra taking profit of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of this source. Results. A power law with a photon index \Gamma = 1.72^{+0.03}_{-0.01} accounts for the continuum emission of this source in the hard X-rays from 10 down to 1 keV. At lower energies, a black body model with kT= 0.100\pm 0.003 keV provides a good description of the observed soft excess. The absorption signatures in the spectra of UGC11763 are consistent with the presence of a two phase ionized material (log U=1.65^{+0.07}_{-0.08}; 2.6\pm 0.1 and log N_{H} = 21.2\pm 0.2; 21.51\pm 0.01 cm^{-2}, respectively) in the line of sight. The physical conditions found are consistent with the two phases being in pressure equilibrium. The low ionization component is more ionized than typically found for warm absorbers in other Seyfert 1 galaxies. There are also signatures of some emission lines: Ovii He$\alpha$(r), Ovii He$\alpha$(f), a blend of the Neix He$\alpha$ triplet and Fexviii at \lambda 17.5 \AA.Comment: 11 pages, 10 figures, accepted to be published by A&

Dynamics of hydration water in deuterated purple membranes explored by neutron scattering

The function and dynamics of proteins depend on their direct environment, and much evidence has pointed to a strong coupling between water and protein motions. Recently however, neutron scattering measurements on deuterated and natural-abundance purple membrane (PM), hydrated in H2O and D2O, respectively, revealed that membrane and water motions on the ns–ps time scale are not directly coupled below 260 K (Wood et al. in Proc Natl Acad Sci USA 104:18049–18054, 2007). In the initial study, samples with a high level of hydration were measured. Here, we have measured the dynamics of PM and water separately, at a low-hydration level corresponding to the first layer of hydration water only. As in the case of the higher hydration samples previously studied, the dynamics of PM and water display different temperature dependencies, with a transition in the hydration water at 200 K not triggering a transition in the membrane at the same temperature. Furthermore, neutron diffraction experiments were carried out to monitor the lamellar spacing of a flash-cooled deuterated PM stack hydrated in H2O as a function of temperature. At 200 K, a sudden decrease in lamellar spacing indicated the onset of long-range translational water diffusion in the second hydration layer as has already been observed on flash-cooled natural-abundance PM stacks hydrated in D2O (Weik et al. in J Mol Biol 275:632–634, 2005), excluding thus a notable isotope effect. Our results reinforce the notion that membrane-protein dynamics may be less strongly coupled to hydration water motions than the dynamics of soluble proteins