10,946 research outputs found

    Digital filter design using root moments for sum-of-all-pass structures from complete and partial specifications

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    A local moments estimation of the spectrum of a large dimensional covariance matrix

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    This paper considers the problem of estimating the population spectral distribution from a sample covariance matrix when its dimension is large. We generalize the contour-integral based method in Mestre (2008) and present a local moment estimation procedure. Compared with the original, the new procedure can be applied successfully to models where the asymptotic clusters of sample eigenvalues generated by different population eigenvalues are not all separate. The proposed estimates are proved to be consistent. Numerical results illustrate the implementation of the estimation procedure and demonstrate its efficiency in various cases.postprin

    The thermal response of A pulsar glitch: The nonspherically symmetric case

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    We study the thermal evolution of a pulsar after a glitch in which the energy is released from a relatively compact region. A set of relativistic thermal transport and energy balance equations is used to study the thermal evolution, without making the assumption of spherical symmetry. We use an exact cooling model to solve this set of differential equations. Our results could differ significantly from those obtained under the assumption of spherical symmetry. Even for young pulsars with a hot core like the Vela pulsar, a detectable hot spot could be observed after a glitch if a large amount of energy is released in a small region close to the surface of the star. The results suggest that the intensity variation and the relative phases of hard X-ray emissions in different epochs may provide important information on the equation of state. © 1998. The American Astronomical Society. All rights reserved.published_or_final_versio

    Active anti-guide vertical cavity surface emitting lasers with diffused quantam wells structure

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    The enhancement of single transverse mode operation in vertical cavity surface emitting lasers by using interdiffused quantum wells is proposed and analyzed. It is observed that the influence of self-focusing (arising from carrier spatial hole burning and thermal lensing) on the profile of transverse modes can be minimized by introducing a step diffused quantum wells structure inside the core region of quantum-well active layer. Stable single-mode operation in vertical cavity surface emitting lasers can also be maintained.published_or_final_versio

    Disruption of the blood-testis barrier integrity by bisphenol A in vitro: Is this a suitable model for studying blood-testis barrier dynamics?

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    Bisphenol A, an estrogenic environmental toxicant, has been implicated to have hazardous effects on reproductive health in humans and rodents. However, there are conflicting reports in the literature regarding its effects on male reproductive function. In this study, it was shown that in adult rats treated with acute doses of bisphenol A, a small but statistically insignificant percentage of seminiferous tubules in the testes displayed signs of germ cell loss, consistent with some earlier reports. It also failed to disrupt the blood-testis barrier in vivo. This is possibly due to the low bioavailability of free bisphenol A in the systemic circulation. However, bisphenol A disrupted the blood-testis barrier when administered to immature 20-day-old rats, consistent with earlier reports concerning the higher susceptibility of immature rats towards bisphenol A. This observation was confirmed using primary Sertoli cells cultured in vitro with established tight junction-permeability barrier that mimicked the blood-testis barrier in vivo. The reversible disruption of Sertoli cell tight junction barrier by bisphenol A was associated with an activation of ERK, and a decline in the levels of selected proteins at the tight junction, basal ectoplasmic specialization, and gap junction at the blood-testis barrier. Studies by dual-labeled immunofluorescence analysis and biotinylation techniques also illustrated declining levels of occludin, connexin 43, and N-cadherin at the cell-cell interface following bisphenol A treatment. In summary, bisphenol A reversibly perturbs the integrity of the blood-testis barrier in Sertoli cells in vitro, which can also serve as a suitable model for studying the dynamics of the blood-testis barrier. © 2009 Elsevier Ltd. All rights reserved.postprin

    Acupuncture mycobacteriosis [6]

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    Cloning and molecular characterization of a copper chaperone gene (HbCCH1) from Hevea brasiliensis

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    The cDNA encoding a copper chaperone, designated as HbCCH1, was isolated from Hevea brasiliensis. HbCC1 was 589 bp long containing a 261 bp open reading frame encoding a putative protein of 86 amino acids, flanked by a 103 bp 5’UTR and a 225 bp 3’UTR. The predicted molecular mass of HbCCH1 was 9.2 kDa, with an isoelectric point (pI) of 5.13. The HbCCH1 share the conserved N-terminal metalbinding domain (MXCXXC) and a lysine-rich C-terminus. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that HbCCH1 was constitutively expressed in all the tested tissues. HbCCH1 transcripts were accumulated at relatively low levels in the flower, bud and leaves, while HbCCH1 transcripts were accumulated at relatively high levels in the latex. The transcription of HbCCH1 in the latex was induced by jasmonate.Key words: Copper chaperone, Hevea brasiliensis, latex

    Direct observation of an isopolyhalomethane O-H insertion reaction with water: Picosecond time-resolved resonance Raman (ps-TR 3) study of the isobromoform reaction with water to produce a CHBr 2OH product

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    The spectroscopic observation of an isopolyhalomethane O-H insertion reaction with water was obtained using picosecond time-resolved resonance Raman spectroscopy. It was observed that photolysis of low concentrations of bromoform in aqueous solution resulted in noticeable formation of HBr strong acid. It was shown by ab initio calculations that isobromoform can react with water to produce a CHBr 2(OH) O-H insertion reaction product and a HBr leaving group. The implications of the results for the phase dependent behavior of polyhalomethane photochemistry in the gas phase versus water solvated environments were discussed.published_or_final_versio

    Magnetic quantum phase transition of cold atoms in an optical lattice

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    We propose a scheme to investigate the magnetic phase transition of cold atoms confined in an optical lattice. We also demonstrate how to get coupled two-leg spin ladders which display a phase transition from a spin liquid to magnetic ordered state in two-dimensional optical lattice. An experimental protocol is further designed for observing this phenomenon. © 2007 The American Physical Society.published_or_final_versio
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