2,359 research outputs found
Interplay between plastic deformations and optical properties of metal surfaces : a multiscale study
Complex Organic Molecules in a Very Young Hot Corino, HOPS 373SW
We present the spectra of Complex Organic Molecules (COMs) detected in HOPS
373SW with the Atacama Large Millimeter/submillimeter Array (ALMA). HOPS 373SW,
which is a component of a protostellar binary with a separation of 1500 au, has
been discovered as a variable protostar by the JCMT Transient monitoring survey
with a modest ~30% brightness increase at submillimeter wavelengths. Our ALMA
Target of Opportunity (ToO) observation at ~345 GHz for HOPS 373SW revealed
extremely young chemical characteristics with strong deuteration of methanol.
The dust continuum opacity is very high toward the source center, obscuring
line emission from within 0.03 arcsec. The other binary component, HOPS 373NE,
was detected only in C17O in our observation, implying a cold and quiescent
environment. We compare the COMs abundances relative to CH3OH in HOPS 373SW
with those of V883 Ori, which is an eruptive disk object, as well as other hot
corinos, to demonstrate the chemical evolution from envelope to disk. High
abundances of singly, doubly, and triply deuterated methanol (CH2DOH, CHD2OH,
and CD3OH) and a low CH3CN abundance in HOPS 373SW compared to other hot
corinos suggest a very early evolutionary stage of HOPS 373SW in the hot corino
phase. Since the COMs detected in HOPS 373SW would have been sublimated very
recently from grain surfaces, HOPS 373SW is a promising place to study the
surface chemistry of COMs in the cold prestellar phase, before sublimation.Comment: Accepted for publication in Ap
The ice composition in the disk around V883 Ori revealed by its stellar outburst
Complex organic molecules (COMs), which are the seeds of prebiotic material
and precursors of amino acids and sugars, form in the icy mantles of
circumstellar dust grains but cannot be detected remotely unless they are
heated and released to the gas phase. Around solar-mass stars, water and COMs
only sublimate in the inner few au of the disk, making them extremely difficult
to spatially resolve and study. Sudden increases in the luminosity of the
central star will quickly expand the sublimation front (so-called snow line) to
larger radii, as seen previously in the FU Ori outburst of the young star V883
Ori. In this paper, we take advantage of the rapid increase in disk temperature
of V883 Ori to detect and analyze five different COMs, methanol, acetone,
acetonitrile, acetaldehyde, and methyl formate, in spatially-resolved
submillimeter observations. The COMs abundances in V883 Ori is in reasonable
agreement with cometary values. This result suggests that outbursting young
stars can provide a special opportunity to study the ice composition of
material directly related to planet formation.Comment: Published in Nature Astronom
Nonvolatile memory characteristics associated with oxygen ion exchange in thin-film transistors with indium-zinc oxide channel and HfO2-x gate oxide
Non-charge-storage-based nonvolatile memory characteristics associated with oxygen ion exchange are demonstrated in a thin-film transistor (TFT) composed of an indium-zinc oxide (IZO) channel and an oxygen-deficient HfO2???x gate oxide. A nonvolatile increase in drain current and a reduced threshold voltage are obtained upon application of positive gate voltage, with the opposite characteristics upon application of negative voltage. The device shows nonvolatile retention properties and suitable endurance properties after repeated operations. Modulation of channel conductance occurs as a results of oxygen ion exchange between the HfO2???x gate oxide and the IZO channel, which consequently alters the oxygen vacancy concentration in the IZO channel; these vacancies act as n-type dopants. For comparison, a device with a thin SiO2 layer inserted between the HfO2???x gate oxide and the IZO channel to prevent oxygen ion exchange shows only the increased threshold voltage upon application of a positive gate voltage as a result of electron charging. These results verify the conductance modulation mechanism associated with oxygen ion exchange at the interface of the HfO2???x gate oxide and the IZO channel. In addition, the nonvolatile memory characteristics of the device are indicative of its potential for non-charge-storage-based nonvolatile memory application
Spectral survey of a Hot core with an Eruptive Accretion in S255IR NIRS3 (SHEA): The discovery of class I and class II millimeter methanol maser transitions
We report the detection of the millimeter CHOH masers including a new
detection of class I (11-10A) and class II
(6-5E) maser transitions toward the high-mass protostar S255IR
NIRS3 in post-burst phase. The CHOH emissions were detected as a mixture of
maser and thermal characteristics. We examine the detected transitions using an
excitation diagram and LTE model spectra and compare the observed properties
with those of thermal lines. Class II CHOH maser transitions showed
distinctive intensity and velocity distributions from those of thermal
transitions. Bright distinct emission components in addition to the fragmented
and arc-shaped emissions are only detected in class I CHOH maser
transitions toward southern and western directions from the protostellar
position, implying the presence of the slow outflow shocks.Comment: 9 pages, 4 Figures, 1 Table, Accepted for publication in ApJ
Sofosbuvir-based therapy for patients with chronic hepatitis C: Early experience of its efficacy and safety in Korea
Background/AimsThe previous standard treatment for chronic hepatitis C (CHC) patients, comprising a combination of pegylated interferon (IFN) and ribavirin, was associated with suboptimal efficacy and severe adverse reactions. A new era of direct-acting antivirals is now dawning in Korea. Early experience of applying sofosbuvir-based therapy to CHC patients in Korea is reported herein.MethodsData on efficacy and safety were collected for CHC patients treated with a combination of sofosbuvir plus ribavirin or sofosbuvir/ledipasvir with or without ribavirin.ResultsThis retrospective study included 25 consecutive patients who received sofosbuvir-based therapy (19 with genotype 1b and 6 with genotype 2) at Seoul National University Hospital from May 2014 to April 2015. A virologic response was achieved at week 4 by 85.7% and 80% of the patients with genotypes 1b and 2, respectively. The HCV-RNA level decreased more slowly in IFN-experienced than in treatment-naïve patients with genotype 1b. However, the sustained virologic response at week 12 (SVR12) rate did not differ among these patients, and was as high as 100%. The presence of cirrhosis significantly increased the risk of a virologic response failure at week 4 (OR, 11.0; P=0.011) among patients with HCV genotype 1b. Only five patients (20%) experienced minor adverse events, including grade 1 fatigue and headache. The hemoglobin level decreased slightly after sofosbuvir-based therapy, but there was no case of premature discontinuation of this therapy.ConclusionsIn a real clinical practice, sofosbuvir-based therapy for CHC patients in Korea achieved optimal antiviral efficacy with insignificant adverse events. Long-term follow-up data are warranted to ensure the sustained antiviral efficacy and long-term safety of sofosbuvir-based IFN-free therapy
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