998 resultados para electrical differential


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Cynthia Dwork: A Firm Foundation for Private Data Analysis Required reading

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En el año 2002, la Secretaría de Educación de Bogotá estipuló la Resolución 2101 que tenía por objeto asegurar el ciclo de la educación completo en los colegios públicos. El propósito de este trabajo es evaluar el impacto de los mecanismos seguidos a la aplicación de esta política sobre la tasa de deserción escolar. Las escuelas tenían tres mecanismos diferentes para alcanzar el objetivo de la presente resolución: expandir los grados escolares ofertados, integrarse con otros colegios de la zona, o ambos. Para ello, utilizo variables instrumentales para resolver el sesgo causado por el hecho de que los colegios que siguen determinada estrategia eran los que tenían altas tasas de deserción inicialmente. Usando datos sobre las características institucionales y las características socio-demográficas de la población cerca del colegio, evalúo el impacto de estos tres mecanismos sobre las tasas de deserción escolar. Los resultados sugieren que las instituciones que aumentaron los grados experimentan un aumento en el número de estudiantes que abandonan el colegio en 12.1 puntos porcentuales, mientras que las instituciones que complementaron este mecanismo con la integración de un colegio próximo pre existente mostraron una reducción en la tasa de deserción escolar de 9.8 puntos porcentuales.

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Primary dysmenorrhea is pelvic pain during the menstrual cycle. The A delta and C fibers aresensitized by the increased release of prostaglandins and leukotrienes, thus causing pain. TransElectric Nerve Stimulation (TENS) is a physiotherapeutic strategy that mitigatespain sensation. Objective: The aim of this paper is to present six cases of women in childbearingage who were diagnosed with primary dysmenorrhea and received transcutaneous electricnerve stimulation. Materials and methods: A type of study, case report, was conducted with sixwomen between 15 and 25 years of age with medical diagnosis of primary dysmenorrhea. Weassessed pain intensity utilizing the visual analogue pain scale and located the pain by usinga pain test map. Results: Pain intensity decreased in all treated women. Conclusion: Transcutaneouselectric nerve stimulation (TENS) is a physiotherapeutic strategy that mitigates painsensation. We conclude that high frequency TENSis a safe noninvasive modality to achievereduction of pain in primary dysmenorrhea.

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An analytic method to evaluate nuclear contributions to electrical properties of polyatomic molecules is presented. Such contributions control changes induced by an electric field on equilibrium geometry (nuclear relaxation contribution) and vibrational motion (vibrational contribution) of a molecular system. Expressions to compute the nuclear contributions have been derived from a power series expansion of the potential energy. These contributions to the electrical properties are given in terms of energy derivatives with respect to normal coordinates, electric field intensity or both. Only one calculation of such derivatives at the field-free equilibrium geometry is required. To show the useful efficiency of the analytical evaluation of electrical properties (the so-called AEEP method), results for calculations on water and pyridine at the SCF/TZ2P and the MP2/TZ2P levels of theory are reported. The results obtained are compared with previous theoretical calculations and with experimental values

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The influence of the basis set size and the correlation energy in the static electrical properties of the CO molecule is assessed. In particular, we have studied both the nuclear relaxation and the vibrational contributions to the static molecular electrical properties, the vibrational Stark effect (VSE) and the vibrational intensity effect (VIE). From a mathematical point of view, when a static and uniform electric field is applied to a molecule, the energy of this system can be expressed in terms of a double power series with respect to the bond length and to the field strength. From the power series expansion of the potential energy, field-dependent expressions for the equilibrium geometry, for the potential energy and for the force constant are obtained. The nuclear relaxation and vibrational contributions to the molecular electrical properties are analyzed in terms of the derivatives of the electronic molecular properties. In general, the results presented show that accurate inclusion of the correlation energy and large basis sets are needed to calculate the molecular electrical properties and their derivatives with respect to either nuclear displacements or/and field strength. With respect to experimental data, the calculated power series coefficients are overestimated by the SCF, CISD, and QCISD methods. On the contrary, perturbation methods (MP2 and MP4) tend to underestimate them. In average and using the 6-311 + G(3df) basis set and for the CO molecule, the nuclear relaxation and the vibrational contributions to the molecular electrical properties amount to 11.7%, 3.3%, and 69.7% of the purely electronic μ, α, and β values, respectively

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Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any molecule) makes an important contribution to the static second vibrational hyperpolarizability of CF4 and SF6. A comparison between calculated and experimental values for the difference between the (anisotropic) Kerr effect and electric field induced second-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approximation gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small

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This study provides detailed information on the ability of healthy ears to generate distortion product otoacoustic emissions (DPOAEs).

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This paper discusses a study conducted to perform a mathematical analysis and an electrical analysis of pulsed tones to determine which type of pulsed tone is most suitable.

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This paper studies trends in the use of diagnostic auditory brainstem response (ABR) at St. Louis Children's Hospital from 1984 to 2001 in light of legislative changes in Missouri mandating screening for hearing loss in all newborns beginning January 1, 2002.

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This dissertation examined whether a hearing impairment of the auditory end-organ has the same or a differential effect on the place and periodicity processes. Differential sensitivities for four normally hearing listeners and for both ears of five patients with unilateral Meniere’s disease were measured for tonal frequency and rate of sinusoidally amplitude-modulated noise at common frequencies and rates of the stimulus.