12,495 research outputs found

    On the dispersion management of fluorite whispering-gallery mode resonators for Kerr optical frequency comb generation in the telecom and mid-infrared range

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    Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above 10910^9. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion (GVDGVD). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the GVDGVD of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar GVDGVD, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to push the zero-dispersion wavelength of fluorite crystals towards the mid-infrared (mid-IR) range, thereby allowing for efficient Kerr comb generation in that spectral range. We show that barium fluoride is the most interesting crystal in this regard, due to its zero dispersion wavelength (ZDWZDW) at 1.93μm1.93 \rm{\mu m} and an optimal dispersion profile in the mid-IR regime. We expect our results to facilitate the design of different platforms for Kerr frequency comb generations in both telecommunication and mid-IR spectral ranges

    Gendered aspects of perceived and internalized HIV-related stigma in China.

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    Although studies have demonstrated that females experience more HIV-related stigma than males do, questions remain regarding the different dimensions of the stigma (i.e., perceived versus internalized) in China. The present study investigated gender differences in perceived and internalized HIV-related stigma, taking into account the potential influence of education. The study was conducted between October 2011 and March 2013. A total of 522 people living with HIV (PLH) were recruited from Anhui Province, China. The PLH participated in a survey using the Computer Assisted Personal Interview (CAPI) method. The gender differences in perceived and internalized HIV-related stigma were calculated with and without stratifying by education level. Female participants had significantly less education than the male participants. No significant difference was observed between females and males with respect to perceived stigma. However, females reported significantly higher internalized stigma than males did (p < .001). When socio-demographic characteristics were controlled, the gender difference in internalized stigma remained significant among educated participants (p = .038). The findings suggested that gender differences in HIV-related stigma were primarily found for internalized stigma. Heightened intervention efforts are encouraged to reduce internalized HIV-related stigma, particularly among female PLH in China and other regions with similar gender dynamics

    Basket Options Pricing for Jump Diffusion Models

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    In this thesis we discuss basket option valuation for jump-diffusion models. We suggest three new approximate pricing methods. The first approximation method is the weighted sum of Rogers and Shi’s lower bound and the conditional second moment adjustments. The second is the asymptotic expansion to approximate the conditional expectation of the stochastic variance associated with the basket value process. The third is the lower bound approximation which is based on the combination of the asymptotic expansion method and Rogers and Shi’s lower bound. We also derive a forward partial integro-differential equation (PIDE) for general asset price processes with stochastic volatilities and stochastic jump compensators. Numerical tests show that the suggested methods are fast and accurate in comparison with Monte Carlo and other methods in most cases

    Hausdorff operators on modulation and Wiener amalgam spaces

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    We give the sharp conditions for boundedness of Hausdorff operators on certain modulation and Wiener amalgam spaces.Comment: To appear in "Annals of Functional Analysis
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