Vapor crystal growth technology development: Application to cadmium telluride

Growth of bulk crystals by physical vapor transport was developed and applied to cadmium telluride. The technology makes use of effusive ampoules, in which part of the vapor contents escapes to a vacuum shroud through defined leaks during the growth process. This approach has the advantage over traditional sealed ampoule techniques that impurity vapors and excess vapor constituents are continuously removed from the vicinity of the growing crystal. Thus, growth rates are obtained routinely at magnitudes that are rather difficult to achieve in closed ampoules. Other advantages of this effusive ampoule physical vapor transport (EAPVT) technique include the predetermination of transport rates based on simple fluid dynamics and engineering considerations, and the growth of the crystal from close to congruent vapors, which largely alleviates the compositional nonuniformities resulting from buoyancy driven convective transport. After concisely reviewing earlier work on improving transport rates, nucleation control, and minimization of crystal wall interactions in vapor crystal growth, a detail account is given of the largely computer controlled EAPVT experimentation

Asymptotic eigenfunctions for Schrödinger operators on a vector bundle

In the limit $\hbar\to 0$, we analyze a class of Schr\"odinger operators $H_\hbar = \hbar^2 L + \hbar W + V\cdot \mathrm{id}$ acting on sections of a vector bundle $\mathcal{Eh}$ over a Riemannian manifold $M$ where $L$ is a Laplace type operator, $W$ is an endomorphism field and the potential energy $V$ has a non-degenerate minimum at some point $p\in M$. We construct quasimodes of WKB-type near $p$ for eigenfunctions associated with the low lying eigenvalues of $H_\hbar$. These are obtained from eigenfunctions of the associated harmonic oscillator $H_{p, \hbar}$ at $p$, acting on smooth functions on the tangent space

Multispectral Image Correction for Geometric Measurements

Multispectral- and hyperspectral imaging technologies enable new possibilities in industrial measurement applications. Based on the knowledge of remote sensing a lot of investigations were made in the last decades of years. Nevertheless the demands on remote sensing versus technical multi spectral image processing are quite different. In the field of precise geometric measurement technics it is necessary to correct the image data between different spectral channels with a high accuracy, normally in the micron range. Otherwise the geometric absolute value of fail detection on edges can be become very large. State of the art in industrial imaging and detection of geometric features is the calibration of only one imaging channel. In this paper, the studies on a twelve channel multi spectral imager were presented. For the applied filter wheel system, investigations on the improvement of lens aberration as well as for the defocus problem were made. Therefore a calibrated high precision geometric test chart was used to calibrate the system geometrically. To correct the geometric errors on the image plane a special moving filter approach, based on linear convolution, was developed. For every channel a calibration matrix were calculated and applied on the image system output

Simulación numérica del proceso de Pasteurización artesanal de leche

El proceso de pasteurización consiste en el calentamiento de líquidos hasta una temperatura tal que permita la reducción de los microorganismos patógenos hasta un nivel aceptable para el ser humano y de esta forma extender el tiempo de vida útil. El enfriamiento es la última etapa de la pasteurización, durante esta etapa el producto debe ser enfriado drásticamente a la temperatura de inhibición bacteriana (4 °C). El tiempo de calentamiento en la pasteurización es un parámetro importante, ya que si es breve no destruye el número suficiente de microorganismos y, por lo tanto, su población podría volver a aumentar hasta niveles que pongan en riesgo la salud de los consumidores, por otro lado si es muy grande se incurren en pérdidas económicas y se degrada la calidad del producto. El objetivo de este trabajo es la optimización de la pasteurización artesanal de leche, para aprovechar la producción regional de las chacras de la provincia de Misiones y realizar la transferencia a pequeños productores. Se analizó el proceso de pasteurización lenta, que emplea temperaturas de entre 63ºC y 65 ºC y un tiempo mínimo de 30 minutos. Se efectuó la simulación numérica del proceso de pasteurización empleando el método de elementos finitos. Se utilizaron modelos de simetría axial del sachet para distintos valores de temperatura del agua de calefacción y del agua de enfriamiento. Los modelos fueron validados con medidas experimentales de la temperatura dentro y fuera del sachet conteniendo un litro de agua mediante un termistor Pt100 y termómetros, durante los procesos de calentamiento y enfriamiento. Se analizaron los resultados identificando los puntos que necesitaban más tiempo en calentarse en el interior del sachet. Con la historia térmica de esos puntos se calculó el tiempo necesario para destruir distintos tipos de los microorganismos de acuerdo a su resistencia intrínseca y así determinar el tiempo óptimo de pasteurización. También se tuvieron en cuenta otros dos parámetros para analizar la eficiencia de la pasteurización, la ausencia de fosfatasa alcalina, ya que su eliminación asegura la eliminación de los microorganismos patógenos y la presencia de lactoperoxidasa, que es un indicador de la calidad del producto. Finalmente se determinaron recomendaciones de tiempos óptimos para diferentes temperaturas del agua de calefacción y una forma más eficiente del enfriamiento del producto comprendiendo dos etapas.Fil: Martinez, Ana M.. Provincia de Misiones. Comite de Desarrollo E Innovacion Tecnologica; ArgentinaFil: Rosenberger, Mario Roberto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; Argentina. Universidad Nacional de Misiones; Argentin

Self-rated health and employment status in patients with multiple sclerosis

Purpose. The aim is to explore the association between self-rated health and employment status in patients with multiple sclerosis (MS) when controlling for age, gender, functional disability, disease duration, anxiety and depression. Method. One hundred eighty-four people with MS completed a sociodemographic questionnaire that included questions on employment status, the first item of the Short Form-36 Health Survey and the Hospital Anxiety and Depression Scale. Functional disability was assessed using the Expanded Disability Status Scale. The probability of good self-rated health in employed persons was investigated using stepwise logistic regression analyses. Results. Patients with MS who reported good self-rated health were 2.46 times more likely to be employed (95% confidence interval [CI]: 1.08-5.59). Patients without anxiety were 2.64 times more likely to be employed (95% CI: 1.23-5.67). Patients with higher EDSS scores were 0.49 times less likely to be employed (95% CI: 0.33-0.70). Age, gender, disease duration and the presence of depression did not show an increased chance of patient employment. Conclusions. Patients with MS with good self-rated health are more likely to be employed, even after adjusting for age, gender, education, functional disability, disease duration, depression and anxiety. Dependent on the findings of longitudinal studies unravelling the relevant causal pahways, self-rated health might be used as a quick and cheap prognostic marker, which could warn about the possible loss of employment, or changes in functional disability

Single-shot carrier-envelope-phase measurement in ambient air

The ability to measure and control the carrier envelope phase (CEP) of few-cycle laser pulses is of paramount importance for both frequency metrology and attosecond science. Here, we present a phase meter relying on the CEP-dependent photocurrents induced by circularly polarized few-cycle pulses focused between electrodes in ambient air. The new device facilitates compact single-shot, CEP measurements under ambient conditions and promises CEP tagging at repetition rates orders of magnitude higher than most conventional CEP detection schemes as well as straightforward implementation at longer wavelengths

Mutations of fake weighted projective planes

In previous work by Coates, Galkin, and the authors, the notion of mutation between lattice polytopes was introduced. Such a mutation gives rise to a deformation between the corresponding toric varieties. In this paper we study one-step mutations that correspond to deformations between weighted projective planes, giving a complete characterisation of such mutations in terms of T-singularities. We show also that the weights involved satisfy Diophantine equations, generalising results of Hacking-Prokhorov

Polynomial functions for direct calculation of the surface free energy developed from the Neumann Equation of State method

The Neumann Equation of State (EQS) allows obtaining the value of the surface free energy of a solid {\gamma}_{SV} from the contact angle ({\theta}) of a probe liquid with known surface tension {\gamma}_{LV}. The value of {\gamma}_{SV} is obtained by numerical methods solving the corresponding EQS. In this work, we analyzed the discrepancies between the values of {\gamma}_SV obtained using the three versions of the EQS reported in the literature. The condition number of the different EQS was used to analyze their sensitivity to the uncertainty in the {\theta} values. Polynomials fit to one of these versions of EQS are proposed to obtain values of {\gamma}_{SV} directly from contact angles ({\gamma}_SV ({\theta})) of particular probe liquids. Finally, a general adjusted polynomial is presented to obtain the values of {\gamma}_{SV} not restricted to a particular probe liquid ({\gamma}_{SV}({\theta},{\gamma}_{LV})). Results showed that the three versions of EQS present non-negligible discrepancies, especially at high values of {\theta}. The sensitivity of the EQS to the uncertainty in the values of {\theta} is very similar in the three versions and depends on the probe liquid used (greater sensitivity at higher {\gamma}_{LV}) and on the value of {\gamma}_{SV} of the solid (greater sensitivity at lower {\gamma}_{SV}). The discrepancy of the values obtained by numerical resolution of both the fifth-order fit polynomials and the general fit polynomial was low, no larger than {\pm}0.40 mJ/m^{2}. The polynomials obtained allow the analysis and propagation of the uncertainty of the input variables in the determination of {\gamma}_{SV} in a simple and fast way.Comment: 37 pages, 13 figure