29 research outputs found

    Insight-HXMT observations of Swift J0243.6+6124 during its 2017-2018 outburst

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    The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by {\it the Hard X-ray Modulation Telescope} ({\it Insight-\rm HXMT). Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. No evidence of line-like features is, however, found up to 150 keV\rm 150~keV. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with B1013 GB\rm \sim 10^{13}~G, D6 kpcD\rm \sim 6~kpc and peak luminosity of >1039 erg s1\rm >10^{39}~erg~s^{-1} which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star.Comment: publishe

    Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

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    As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.Comment: 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.0443

    Strategic Entry Decisions, Accounting Signals, and Risk Management Disclosure

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    This dissertation investigates the economic consequences from hedge accounting signals and risk management disclosure. I first examine the product market consequences to these accounting signals and related disclosure in Chapter 1, then stock market reactions to disclosure requirements in Chapter 2. Chapter 1 examines potential entrants’ strategic entry decisions in response to incumbents’ accounting information and related disclosure. I predict that potential entrants are more likely to enter markets in which the incumbents’ accounting information suggests higher future production costs that are specific to the incumbents themselves. I further hypothesize that the relation is stronger when the accounting signals are accompanied by more disclosure. Using detailed U.S. airline industry data and hedge accounting disclosure under SFAS 133, I find that potential entrants are more likely to enter routes in which the incumbents’ lower accumulated other comprehensive income from fuel hedges suggests their higher future production costs. This entry pattern is stronger when incumbents have more transparent annual report disclosure regarding their fuel hedge programs. The entry pattern is also stronger after a systematic increase in risk management disclosure requirements following the (exogenous) adoption of SFAS 161. Chapter 2 analyzes stock returns of U.S. airlines around events leading up to the adoption of SFAS 161. SFAS 161 enhanced the disclosure requirements for derivatives and hedging activities. I find that U.S. airlines experienced statistically significant positive returns around the key events leading up to the adoption of SFAS 161. I then examine the cross-sectional variation of the returns around these events. Regression results provide initial support for the real effects theory that greater disclosure requirements could distort firms’ hedging and production decisions and lead to suboptimal behavior. In summary, this dissertation provides evidence that competitors use hedge accounting signals and related disclosure in making product market decisions. Meanwhile, additional risk-management disclosures may also distort firms’ hedging and production behavior, leading to suboptimal decisions. This dissertation sheds light on the ongoing projects by the FASB and the IASB on hedge accounting and disclosure and informs the regulators that costs and benefits should be weighted in hedge accounting policy setting.Ph

    The Real Effects of Geographic Lending Disclosure on Banks

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    An Efficient Propagation System through Root Cuttings of an Ecological and Economic Value Plant—Broussonetia papyrifera (L.) L’Hér. ex Vent

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    Broussonetia papyrifera (L.) L’Hér. ex Vent. has considerable economic and ecological value and a long history of use in China. In this paper, root cuttings were used as the material to establish an efficient vegetative propagation of B. papyrifera. The results revealed that root segments with a diameter of 1.5~2.0 cm and a length of 20~30 cm were most suitable for shoot regeneration, as these segments had the highest adventitious shoot induction rates (93.3%), strongest adventitious shoots, and highest multiplication coefficients (7.07). With regard to the methods used for root burial, a horizontal burial at a depth of 1~3 cm yielded the best results, in this case, the adventitious shoot induction rate can reach 86.7%. The best substrate combination was perlite: peat: coconut chaff = 1:1:1 (v/v/v), wherein the adventitious shoot induction rate can reach 75.6%. The best sterilization method was mixing soil with carbendazim and soaking the root sections in carbendazim for 30 min, wherein the adventitious shoot induction rate can reach 77.8%. Adding 0.2 mg/L naphthaleneacetic acid (NAA) to 1/4 Hoagland nutrient solution significantly improved the rooting rate of adventitious shoots to 82.2%, and the survival rate of the acclimatized plants was more than 90.0%

    Targeted Delivery of GDNF through the Blood-Brain Barrier by MRI-Guided Focused Ultrasound

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    Neurotrophic factors, such as glial cell line-derived neurotrophic factor (GDNF), are promising therapeutic agents for neurodegenerative diseases. However, the application of GDNF to treat these diseases effectively is limited because the blood-brain barrier (BBB) prevents the local delivery of macromolecular therapeutic agents from entering the central nervous system (CNS). Focused ultrasound combined with microbubbles (MBs) using appropriate parameters has been previously demonstrated to be able to open the BBB locally and noninvasively. This study investigated the targeted delivery of GDNF MBs through the BBB by magnetic resonance imaging (MRI)-guided focused ultrasound. Evans Blue extravasation and histological examination were used to determine the optimum focused ultrasound parameters. Enzyme-linked immunosorbent assay was performed to verify the effects of GDNF bound on MBs using a biotin-avidin bridging chemistry method to promote GDNF delivery into the brain. The results showed that GDNF can be delivered locally and noninvasively into the CNS through the BBB using MRI-guided focused ultrasound combined with MBs under optimum parameters. MBs that bind GDNF combined with MRI-guided focused ultrasound may be an effective way of delivering neurotrophic factors directly into the CNS. The method described herein provides a potential means of treating patients with CNS diseases
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