4,520 research outputs found
Thermal conductivity of suspended pristine graphene measured by Raman spectroscopy
The thermal conductivity of suspended single-layer graphene was measured as a
function of temperature using Raman scattering spectroscopy on clean samples
prepared directly on a prepatterned substrate by mechanical exfoliation without
chemical treatments. The temperature at the laser spot was monitored by the
frequency of the Raman 2 band of the Raman scattering spectrum, and the
thermal conductivity was deduced by analyzing heat diffusion equations assuming
that the substrate is a heat sink at ambient temperature. The obtained thermal
conductivity values range from 1800 WmK near 325 K to
710 WmK at 500 K.Comment: 4pages, 3 figure
Clinical analysis of pediatric patients who visited Masan Samsung Emergency Center
Purpose : Through a clinical and retrospective analysis of pediatric patients who visited the Regional Emergency Medical Center of Masan Samsung Hospital from January 2007 to December 2008, we characterized pediatric and adolescent emergency patients to improve emergency care in future. Methods : We reviewed the medical records of 14,065 pediatric patients below 19 years of age. Results : The male to female ratio was 1.5:1, and the most common age group was less than 3 years (49.6%). The peak month was May (10.0%), the peak day of the week was Sunday (24.7%), and the peak time of day was 20:00–20:59 (8.5%). There was no difference in the number of visits per day based on weather (sunny, rain [below 10 mm per day], snow, and fog) or daily temperature difference; however, visits increased on sandy, dusty days and decreased on rainy days with more than 10 mm of rain per day. Based on the international classification of disease (ICD)-10 system, the most common disease code was code R (symptoms, sign, and abnormal clinical laboratory finding) (31.5%), and the most common symptom was fever (13.1%). Final outcomes were discharged (73.8%), admitted (25.7%), transferred (0.4%), and expired (0.1%). In adolescent patients aged 15–19 years, the most common disease code was Injury & Poisoning (code S&T, 36.9%); the most common symptom was abdominal pain (9.6%). Conclusion : Pediatric patients visiting the emergency center were most likely to be male and under 3 years of age and to visit between 20:00 and 21:00 on Sundays and in May, and the most common symptom was fever. Differences between adolescents and pediatric patients showed that adolescents had a higher visiting rate with abdominal pain and a larger temperature difference
Transition from quasi-unidirectional to unidirectional guided resonances in leaky-mode photonic lattices
Unidirectional light emission from planar photonic structures is highly
advantageous for a wide range of optoelectronic applications. Recently, it has
been demonstrated that unidirectional guided resonances (UGRs) can be realized
by utilizing topological polarization singularities in momentum space. However,
the practical application of these topological unidirectional emitters has been
limited due to their intricate geometric configurations, requiring special
efforts with high-cost fabrication processes. In this study, we show that
unidirectional light emission can be achieved in conventional one-dimensional
zero-contrast gratings (ZCGs), which can be easily fabricated using current
nanofabrication technologies. In ZCGs, the interband coupling between even-like
and odd-like waveguide modes leads to the formation of quasi-UGRs,
characterized by significantly higher decay rates in either the upward or
downward direction compared to the opposite direction. We demonstrate that
these quasi-UGRs evolve into genuine UGRs with an gradual increase in grating
thickness. Moreover, the emission direction of UGRs can be selectively steered
either upward or downward by adjusting the lattice parameters. In addition to
quasi-UGRs and UGRs, our study also reveals additional topological phenomena in
ZCGs, including exceptional points and quasi-BICs
Information sources cited and relayed in political conversations on Twitter
Using the Twitter data collected prior to the Presidential Election in Korea in 2012, we ask questions regarding influential sources of information in public political discourse. The frequently cited sources, being included as URLs in political tweet messages, are identified and categorized. The result shows that people rely on various sources of information beyond the traditional news media, but the pattern of sharing differ by sources
Research Update: Strategies for efficient photoelectrochemical water splitting using metal oxide photoanodes
Photoelectrochemical (PEC) water splitting to hydrogen is an attractive method for capturing and storing the solar energy in the form of chemical energy. Metal oxides are promising photoanode materials due to their low-cost synthetic routes and higher stability than other semiconductors. In this paper, we provide an overview of recent efforts to improve PEC efficiencies via applying a variety of fabrication strategies to metal oxide photoanodes including (i) size and morphology-control, (ii) metal oxide heterostructuring, (iii) dopant incorporation, (iv) attachments of quantum dots as sensitizer, (v) attachments of plasmonic metal nanoparticles, and (vi) co-catalyst coupling. Each strategy highlights the underlying principles and mechanisms for the performance enhancements.open2
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