311 research outputs found

    Moduli Spaces of Parabolic Bundles over P1\mathbb{P}^1 with Five Marked Points

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    This paper considers the moduli spaces (stacks) of parabolic bundles (parabolic logarithmic flat bundles with given spectrum, parabolic regular Higgs bundles) with rank 22 and degree 11 over P1\mathbb{P}^1 with five marked points. The foliation and stratification structures on these moduli spaces (stacks) are investigated. In paricular, we confirm Simpson's conjecture for moduli space of parabolic logarithmic flat bundles with certain non-special weight system

    Stark tuning of telecom single-photon emitters based on a single Er3+^{3+}

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    The implementation of scalable quantum networks requires photons at the telecom band and long-lived spin coherence. The single Er3+^{3+} in solid-state hosts is an important candidate that fulfills these critical requirements simultaneously. However, to entangle distant Er3+^{3+} ions through photonic connections, the emission frequency of individual Er3+^{3+} in solid-state matrix must be the same, which is challenging because the emission frequency of Er3+^{3+} depends on its local environment. In this study, we propose and experimentally demonstrate the Stark tuning of the emission frequency of a single Er3+^{3+} in a Y2_2SiO5_5 crystal by employing electrodes interfaced with a silicon photonic crystal cavity. We obtain a Stark shift of 182.9 ±\pm 0.8 MHz which is approximately 27 times of the optical emission linewidth, demonstrating the promising applications in tuning the emission frequency of independent Er3+^{3+} into the same spectral channels. Our results provide a useful solution for the construction of scalable quantum networks based on single Er3+^{3+} and a universal tool for tuning the emission of individual rare-earth ions

    S-adenosylmethionine and methylthioadenosine are antiapoptotic in cultured rat hepatocytes but proapoptotic in human hepatoma cells

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    S-adenosylmethionine (AdoMet) is an essential compound in cellular transmethylation reactions and a precursor of polyamine and glutathione synthesis in the liver. In liver injury, the synthesis of AdoMet is impaired and its availability limited. AdoMet administration attenuates experimental liver damage, improves survival of alcoholic patients with cirrhosis, and prevents experimental hepatocarcinogenesis. Apoptosis contributes to different liver injuries, many of which are protected by AdoMet. The mechanism of AdoMet's hepatoprotective and chemopreventive effects are largely unknown. The effect of AdoMet on okadaic acid (OA)-induced apoptosis was evaluated using primary cultures of rat hepatocytes and human hepatoma cell lines. AdoMet protected rat hepatocytes from OA-induced apoptosis dose dependently. It attenuated mitochondrial cytochrome c release, caspase 3 activation, and poly(ADP-ribose) polymerase cleavage. These effects were independent from AdoMet-dependent glutathione synthesis, and mimicked by 5'-methylthioadenosine (MTA), which is derived from AdoMet. Interestingly, AdoMet and MTA did not protect HuH7 cells from OA-induced apoptosis; conversely both compounds behaved as proapoptotic agents. AdoMet's proapoptotic effect was dose dependent and observed also in HepG2 cells. In conclusion, AdoMet exerts opposing effects on apoptosis in normal versus transformed hepatocytes that could be mediated through its conversion to MTA. These effects may participate in the hepatoprotective and chemopreventive properties of this safe and well-tolerated drug

    Evolutionary trajectories of snake genes and genomes revealed by comparative analyses of five-pacer viper

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    Snakes have numerous features distinctive from other tetrapods and a rich history of genome evolution that is still obscure. Here, we report the high-quality genome of the five-pacer viper, Deinagkistrodon acutus, and comparative analyses with other representative snake and lizard genomes. We map the evolutionary trajectories of transposable elements (TEs), developmental genes and sex chromosomes onto the snake phylogeny. TEs exhibit dynamic lineage-specific expansion, and many viper TEs show brain-specific gene expression along with their nearby genes. We detect signatures of adaptive evolution in olfactory, venom and thermal-sensing genes and also functional degeneration of genes associated with vision and hearing. Lineage-specific relaxation of functional constraints on respective Hox and Tbx limb-patterning genes supports fossil evidence for a successive loss of forelimbs then hindlimbs during snake evolution. Finally, we infer that the ZW sex chromosome pair had undergone at least three recombination suppression events in the ancestor of advanced snakes. These results altogether forge a framework for our deep understanding into snakes' history of molecular evolution
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