456 research outputs found
Blending in Future Space-based Microlensing Surveys
We investigate the effect of blending in future gravitational microlensing
surveys by carrying out simulation of Galactic bulge microlensing events to be
detected from a proposed space-based lensing survey. From this simulation, we
find that the contribution of the flux from background stars to the total
blended flux will be equivalent to that from the lens itself despite the
greatly improved resolution from space observations, implying that
characterizing lenses from the analysis of the blended flux would not be easy.
As a method to isolate events for which most of the blended flux is
attributable to the lens, we propose to use astrometric information of source
star image centroid motion. For the sample of events obtained by imposing a
criterion that the centroid shift should be less than three times of the
astrometric uncertainty among the events for which blending is noticed with
blended light fractions , we estimate that the contamination of
the blended flux by background stars will be less than 20% for most () of the sample events. The expected rate of these events is
events/yr, which is large enough for the statistical analysis of the lens
populations.Comment: total 6 pages, including 5 figures, ApJ, in pres
Effect of interlayer interactions on exciton luminescence in atomic-layered MoS2 crystals
The atomic-layered semiconducting materials of transition metal dichalcogenides are considered effective light sources with both potential applications in thin and flexible optoelectronics and novel functionalities. In spite of the great interest in optoelectronic properties of two-dimensional transition metal dichalcogenides, the excitonic properties still need to be addressed, specifically in terms of the interlayer interactions. Here, we report the distinct behavior of the A and B excitons in the presence of interlayer interactions of layered MoS 2 crystals. Micro-photoluminescence spectroscopic studies reveal that on the interlayer interactions in double layer MoS 2 crystals, the emission quantum yield of the A exciton is drastically changed, whereas that of the B exciton remains nearly constant for both single and double layer MoS 2 crystals. First-principles density functional theory calculations confirm that a significant charge redistribution occurs in the double layer MoS 2 due to the interlayer interactions producing a local electric field at the interfacial region. Analogous to the quantum-confined Stark effect, we suggest that the distinct behavior of the A and B excitons can be explained by a simplified band-bending model.1
Demographic, Behavioral and Perceptual Comparisons of the U.S. Visitor Experience with Group Package Tours and Free Independent Travel to China
U.S. visitor demand for the China travel experience is anticipated to rise significantly through 2105, causing the Chinese government to employ 100 million service providers over the next six years and raising concern about service delivery and perceptions of the on-site China experience. In an effort to better understand these issues concerning U.S. visitors, this study investigated two specific types of U.S. travelers to China: Group Package Tour (GPT) visitors and Free Independent Travel (FIT) visitors. Results indicated that GPT visitors were more likely to be older and have higher household income than FIT visitors. Four trip-related characteristics of GPT and FIT visitors were found to be significantly different, with GPT visitors showing higher levels of satisfaction with the overall China on-site travel experience
Limits of Binaries That Can Be Characterized by Gravitational Microlensing
Due to the high efficiency of planet detections, current microlensing planet
searches focus on high-magnification events. High-magnification events are
sensitive to remote binary companions as well and thus a sample of
wide-separation binaries are expected to be collected as a byproduct. In this
paper, we show that characterizing binaries for a portion of this sample will
be difficult due to the degeneracy of the binary-lensing parameters. This
degeneracy arises because the perturbation induced by the binary companion is
well approximated by the Chang-Refsdal lensing for binaries with separations
greater than a certain limit. For binaries composed of equal mass lenses, we
find that the lens binarity can be noticed up to the separations of
times of the Einstein radius corresponding to the mass of each lens. Among
these binaries, however, we find that the lensing parameters can be determined
only for a portion of binaries with separations less than times of
the Einstein radius.Comment: 5 pages, 3 figures, 1 tabl
A Feasibility Study on the Application of TVDI on Accessing Wildfire Danger in the Korean Peninsula
Wildfire is a major natural disaster affecting socioeconomics and ecology. Remote sensing data have been widely used to estimate the wildfire danger with an advantage of higher spatial resolution. Among the several wildfire related indices using remote sensing data, Temperature Vegetation Dryness Index (TVDI) assesses wildfire danger based on both Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST). Although TVDI has physical advantages by considering both weather and vegetation condition, previous studies have shown TVDI does not performed well compare to other wildfire related indices over the Korean Peninsula. In this study we have attempted multiple modification to improve TVDI performance over the study region. In-situ measured air temperature was employed to increase accuracy, regression line was generated using monthly data to include seasonal effect, and TVDI was calculated at each province level to consider vegetation type and local climate. The modified TVDI calculation method was evaluated in wildfire cases and showed significant improvement in wildfire danger estimation
An Optimal Framework of Video Adaptation and Its Application to Rate Adaptation Transcoding
Microlensing Detections of Planets in Binary Stellar Systems
We demonstrate that microlensing can be used for detecting planets in binary
stellar systems. This is possible because in the geometry of planetary binary
systems where the planet orbits one of the binary component and the other
binary star is located at a large distance, both planet and secondary companion
produce perturbations at a common region around the planet-hosting binary star
and thus the signatures of both planet and binary companion can be detected in
the light curves of high-magnification lensing events. We find that identifying
planets in binary systems is optimized when the secondary is located in a
certain range which depends on the type of the planet. The proposed method can
detect planets with masses down to one tenth of the Jupiter mass in binaries
with separations <~ 100 AU. These ranges of planet mass and binary separation
are not covered by other methods and thus microlensing would be able to make
the planetary binary sample richer.Comment: 5 pages, two figures in JPG forma
Effect of Achyranthes bidentata
The present study investigated the antiobesity effect of Achyranthes bidentata Blume root water extract in a 3T3-L1 adipocyte differentiation model and rats fed with a high-fat diet. To investigate the effect of Achyranthes bidentata Blume on adipogenesis in vitro, differentiating 3T3-L1 cells in adipocyte-induction media were treated every two days with Achyranthes bidentata Blume at various concentrations (1 to 25âÎŒg/mL) for eight days. We found that Achyranthes bidentata Blume root inhibited 3T3-L1 adipocyte differentiation without affecting cell viability, and Western blot analysis revealed that phospho-Akt expression was markedly decreased, whereas there was no significant change in perilipin expression. Furthermore, administration of Achyranthes bidentata Blume root (0.5âg/kg body weight for six weeks) to rats fed with a high-fat diet significantly reduced body weight gain without affecting food intake, and the level of triglyceride was significantly decreased when compared to those in rats fed with only a high-fat diet. These results suggest that Achyranthes bidentata Blume root water extract could have a beneficial effect on inhibition of adipogenesis and controlling body weight in rats fed with a high-fat diet
The effect of 4-hexylresorinol administration on NAD+ level and SIRT activity in Saos-2 cells
Background
4-hexylresorcinol (4HR) has been shown to have anti-oxidant activity similar to that of resveratrol. As resveratrol increases sirtuin (SIRT) activity, 4HR might behave similarly to resveratrol.
Method
In this study, the expression levels of SIRT1, SIRT3, and SIRT6 were evaluated after 4HR administration (1â100 ÎŒM). As NAD+ is a substrate for SIRTs, its levels with SIRT activity were also studied.
Results
In the results, SIRT3 (100 ÎŒM at 24 h) and SIRT6 (1â100 ÎŒM at 24 h and 10 ÎŒM at 8 h) were shown to have significantly higher expression levels compared to untreated control (p < 0.05). Pan-SIRT activity and the NAD+ level was significantly increased compared to that of the untreated control (p < 0.05; 10 and 100 ÎŒM at 24 h).
Conclusion
4HR administration increased SIRT activity and the NAD+ level in Saos-2 cells.This study was carried out with the support of the âCooperative Research Program for Agriculture Science and Technology Development (Project no.PJ01562601)â Rural Development Administration, Republic of Korea
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