125 research outputs found
Far-Ultraviolet Cooling Features of the Antlia Supernova Remnant
We present far-ultraviolet observations of the Antlia supernova remnant
obtained with Far-ultraviolet IMaging Spectrograph (FIMS, also called SPEAR).
The strongest lines observed are C IV 1548,1551 and C III 977. The C IV
emission of this mixed-morphology supernova remnant shows a clumpy
distribution, and the line intensity is nearly constant with radius. The C III
977 line, though too weak to be mapped over the whole remnant, is shown to vary
radially. The line intensity peaks at about half the radius, and drops at the
edge of the remnant. Both the clumpy distribution of C IV and the rise in the C
IV to C III ratio towards the edge suggest that central emission is from
evaporating cloudlets rather than thermal conduction in a more uniform, dense
medium.Comment: 9 pages, 4 figures, will be published in ApJ December 1, 2007, v670n2
issue. see http://astro.snu.ac.kr/~jhshinn/ms.pd
Activation of spleen tyrosine kinase is required for TNF-α-induced endothelin-1 upregulation in human aortic endothelial cells
AbstractEndothelin-1 (ET-1) promotes atherosclerosis. We tested whether spleen tyrosine kinase (Syk) mediates tumor necrosis factor-α (TNF-α)-induced ET-1 upregulation in human aortic endothelial cells (HAECs) and sought to identify the signal pathways involved. TNF-α-induced reactive oxygen species (ROS) activated Syk and phosphatidylinositol 3-kinase (PI3K), which was required for the activation of AP-1 and subsequent ET-1 gene transcription. ROS mediated c-Jun NH2-terminal kinase (JNK) is also required for AP-1 activation, but Syk and PI3K regulated AP-1 activation independently of JNK. Through regulation of ET-1 production, Syk could be implicated in atherosclerosis
On the Origin of Near-Infrared Extragalactic Background Light Anisotropy
Extragalactic background light (EBL) anisotropy traces variations in the
total production of photons over cosmic history, and may contain faint,
extended components missed in galaxy point source surveys. Infrared EBL
fluctuations have been attributed to primordial galaxies and black holes at the
epoch of reionization (EOR), or alternately, intra-halo light (IHL) from stars
tidally stripped from their parent galaxies at low redshift. We report new EBL
anisotropy measurements from a specialized sounding rocket experiment at 1.1
and 1.6 micrometers. The observed fluctuations exceed the amplitude from known
galaxy populations, are inconsistent with EOR galaxies and black holes, and are
largely explained by IHL emission. The measured fluctuations are associated
with an EBL intensity that is comparable to the background from known galaxies
measured through number counts, and therefore a substantial contribution to the
energy contained in photons in the cosmos.Comment: 65 pages, 29 figures, Published in Science Nov 7 2014 (includes
supplementary material
Crystal structure of hyperthermophilic esterase EstE1 and the relationship between its dimerization and thermostability properties
<p>Abstract</p> <p>Background</p> <p>EstE1 is a hyperthermophilic esterase belonging to the hormone-sensitive lipase family and was originally isolated by functional screening of a metagenomic library constructed from a thermal environmental sample. Dimers and oligomers may have been evolutionally selected in thermophiles because intersubunit interactions can confer thermostability on the proteins. The molecular mechanisms of thermostabilization of this extremely thermostable esterase are not well understood due to the lack of structural information.</p> <p>Results</p> <p>Here we report for the first time the 2.1-Å resolution crystal structure of EstE1. The three-dimensional structure of EstE1 exhibits a classic α/β hydrolase fold with a central parallel-stranded beta sheet surrounded by alpha helices on both sides. The residues Ser154, Asp251, and His281 form the catalytic triad motif commonly found in other α/β hydrolases. EstE1 exists as a dimer that is formed by hydrophobic interactions and salt bridges. Circular dichroism spectroscopy and heat inactivation kinetic analysis of EstE1 mutants, which were generated by structure-based site-directed mutagenesis of amino acid residues participating in EstE1 dimerization, revealed that hydrophobic interactions through Val274 and Phe276 on the β8 strand of each monomer play a major role in the dimerization of EstE1. In contrast, the intermolecular salt bridges contribute less significantly to the dimerization and thermostability of EstE1.</p> <p>Conclusion</p> <p>Our results suggest that intermolecular hydrophobic interactions are essential for the hyperthermostability of EstE1. The molecular mechanism that allows EstE1 to endure high temperature will provide guideline for rational design of a thermostable esterase/lipase using the lipolytic enzymes showing structural similarity to EstE1.</p
Analysis On Runoff Characteristics Of Decentralized Rainwater Management System Using XP-SWMM Simulation
In recent years, impervious areas are increasing in residential zone as well as unsettled area with rapid urbanization and land use. Consequently, this phenomenon influences weak urban environmental compositions about climate change including urban flooding accidents. Therefore, a new paradigm on rainwater management is needed for sound and sustainable restoration of hydrological circulation. Recently, a novel rainwater management system has been developed and recommended for irrigation and flood control in Korea. Especially, P city is now planning a new rainwater management system adopting LID (Low Impact Development) techniques on a small scale development area. In this study, XP-SWMM was used to simulate effects on runoff characteristics by installation of 8 kinds of rainwater management facilities on small scale development area (4.2 ha) of P city in Korea. Also, flood control safety analysis under the condition of localized torrential downpour event was carried out and effects of rainwater recycling facility was evaluated to measure annual water resource amount and water cost reduction. Peak rate runoff was reduced 11.8% and 36.4% in restrict A and B, respectively. Total amount of annual water source substitution was estimated 3,000㎡/yr with LID adoption in land use planning. Acknowledgement : This research was supported by a grant (12-TI-C01) from Advanced Water Management Research Program funded by Ministry of Land , Infrastructure, and Transport of Korean government
Conceptual Design of a Solid State Telescope for Small scale magNetospheric Ionospheric Plasma Experiments
The present paper describes the design of a Solid State Telescope (SST) on board the Korea Astronomy and Space Science Institute satellite-1 (KASISat-1) consisting of four [TBD] nanosatellites. The SST will measure these radiation belt electrons from a low-Earth polar orbit satellite to study mechanisms related to the spatial resolution of electron precipitation, such as electron microbursts, and those related to the measurement of energy dispersion with a high temporal resolution in the sub-auroral regions. We performed a simulation to determine the sensor design of the SST using GEometry ANd Tracking 4 (GEANT4) simulations and the Bethe formula. The simulation was performed in the range of 100 ~ 400 keV considering that the electron, which is to be detected in the space environment. The SST is based on a silicon barrier detector and consists of two telescopes mounted on a satellite to observe the electrons moving along the geomagnetic field (pitch angle 0°) and the quasi-trapped electrons (pitch angle 90°) during observations. We determined the telescope design of the SST in view of previous measurements and the geometrical factor in the cylindrical geometry of Sullivan (1971). With a high spectral resolution of 16 channels over the 100 keV ~ 400 keV energy range, together with the pitch angle information, the designed SST will answer questions regarding the occurrence of microbursts and the interaction with energetic particles. The KASISat-1 is expected to be launched in the latter half of 2020
The Effects of Chunghyul-Dan, an Agent of Korean Medicine, on a Mouse Model of Traumatic Brain Injury
Chunghyul-Dan (CHD) is the first choice agent for the prevention and treatment of stroke at the Kyung Hee Medical Hospital. To date, CHD has been reported to have beneficial effects on brain disease in animals and humans, along with antioxidative and anti-inflammatory effects. The aim of this study was to evaluate the pharmacological effects of CHD on a traumatic brain injury (TBI) mouse model to explore the possibility of CHD use in patients with TBI. The TBI mouse model was induced using the controlled cortical impact method. CHD was orally administered twice a day for 5 d after TBI induction; mice were assessed for brain damage, brain edema, blood-brain barrier (BBB) damage, motor deficits, and cognitive impairment. Treatment with CHD reduced brain damage seen on histological examination and improved motor and cognitive functions. However, CHD did not reduce brain edema and BBB damage. In conclusion, CHD could be a candidate agent in the treatment of patients with TBI. Further studies are needed to assess the exact mechanisms of the effects during the acute-subacute phase and pharmacological activity during the chronic-convalescent phase of TBI
Pulmonary Artery Embolotherapy in a Patient with Type I Hepatopulmonary Syndrome after Liver Transplantation
Although liver transplantation (LT) is the only effective treatment option for hepatopulmonary syndrome (HPS), the post-LT morbidity and mortality have been high for patients with severe HPS. We performed post-LT embolotherapy in a 10-year-old boy who had severe type I HPS preoperatively, but he failed to recover early from his hypoxemic symptoms after an LT. Multiple embolizations were then successfully performed on the major branches that formed the abnormal vascular structures. After the embolotherapy, the patient had symptomatic improvement and he was discharged without complications
Far-ultraviolet Observations of the North Ecliptic Pole with SPEAR
We present SPEAR/FIMS far-ultraviolet observations near the North Ecliptic
Pole. This area, at b~30 degrees and with intermediate HI column, seems to be a
fairly typical line of sight that is representative of general processes in the
diffuse ISM. We detect a surprising number of emission lines of many elements
at various ionization states representing gas phases from the warm neutral
medium (WNM) to the hot ionized medium (HIM). We also detect fluorescence bands
of H2, which may be due to the ubiquitous diffuse H2 previously observed in
absorption.Comment: 5 pages, 3 figures, Accepted for publication in ApJ Letter
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