In 10-minute speaking, N95 respirators significantly decreased SARS-CoV-2 emissions compared with no-mask wearing. However, SARS-CoV-2 was detected in the air even when wearing N95 and surgical masks in patients with high viral loads. Therefore, universal masking of infected and uninfected persons is important for preventing COVID-19 transmission via the air.

In order to investigate the origin of multiple populations in globular clusters (GCs), we have constructed new chemical evolution models for proto-GCs where the supernova blast waves undergo blowout without expelling the ambient gas. Chemical enrichments in our models are then dictated by the winds of massive stars together with the asymptotic-giant-branch stars ejecta. We find that the observed Na-O anti-correlation can be reproduced when multiple episodes of starburst and enrichment are allowed to continue in proto-GCs. The “mass budget problem” is mostly resolved by our models without ad-hoc assumptions on star formation efficiency, initial mass function, and significant loss of first-generation stars. Interestingly, ages and chemical abundances predicted by this chemical evolution model are in good agreements with those independently obtained from our stellar evolution model for the horizontal-branch. We also discuss observational evidence for the GC-like multiple populations in the Milky Way bulge.

Recent analyses of Lee et al. (2018, 2019) have confirmed that Galactic bulge consists of stellar populations originated from Milky Way globular clusters (MWGCs). Motivated by this, here we present the evolutionary population synthesis (EPS) for the Galactic bulge and early-type galaxies (ETGs) with the realistic treatment of individual variations in light elements observed in the MWGCs. We have utilized our model with GC-origin populations to explain the CN spread observed in ETGs, and the results show remarkable matches with the observations. We further employ our model to estimate the age of ETGs, which are considered as good analogs for the MW bulge. We find that, without the effect of our new treatments, EPS models will almost always underestimate the true age of ETGs. Our analysis indicates that the EPS with GC-origin populations is an essential constraint in determining the ETG formation epoch and is closely related to understanding the evolution of the Universe.

Sesame (Sesamum indicum L.) is one of the oldest oil crops and is widely cultivated in Asia and Africa. The aim of this study was to assess the genetic diversity, phylogenetic relationships and population structure of 277 sesame core collection accessions collected from 15 countries in four different continents. A total of 158 alleles were detected among the sesame accessions, with the number varying from 3 to 25 alleles per locus and an average of 11.3. Polymorphism information content values ranged from 0.34 to 0.84, with an average of 0.568. These values indicated a high genetic diversity at 14 loci both among and within the populations. Of these, 44 genotype-specific alleles were identified in 12 of the 14 polymorphic simple sequence repeat markers. The core collection preserved a much higher level of genetic variation. Therefore, 10.1% was selected as the best sampling percentage from the whole collection when constructing the core collection. The 277 core collection accessions formed four robust clusters in the unweighted pair group method and the arithmetic averages (UPGMA) dendrogram, although the clustering did not indicate any clear division among the sesame accessions based on their geographical locations. Similar patterns were obtained using model-based structure analysis and country-based dendrograms, as some accessions situated geographically far apart were grouped together in the same cluster. The results of these analyses will increase our understanding of the genotype-specific alleles, genetic diversity and population structure of core collections, and the information can be used for the development of a future breeding strategy to improve sesame yield.

The ultraviolet (UV) color-color relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) is re-examined with the latest GALEX GR6 and SDSS DR7 data. By drawing the FUV – NUV (as a measure of UV temperature) versus FUV – r (as a measure of UV amplitude) color-color diagram for the morphologically-cleaned, spectroscopically-cleaned sample of ~3700 quiescent ETGs, we find that the “old and dead“ ETGs consist of a well-defined sequence in UV colors, the “UV red sequence”, so that the stronger UV excess galaxies should have a harder UV spectral shape systematically. However, the observed UV spectral slope is too steep to be reproduced by the canonical models in which the UV flux is mainly controlled by age or metallicity parameters. The observed data support the helium enhancement scenario in which the UV spectral shape of UV upturn (FUV – NUV < 0.9; FUV – r ~ 6) galaxies may be governed by the minority population of helium-enhanced horizontal-branch (HB) stars.

We present new population synthesis models (Chung et al.2011) for quiescent early-type galaxies (ETGs) with UV-upturn phenomenon using relatively metal-poor and helium-enhanced subpopulations in the model. We find that the presence of helium-enhanced subpopulations in ETGs can naturally reproduce the strong UV-upturns observed in giant elliptical galaxies (Figure 1. left panel), without invoking unrealistically old ages (Park & Lee 1997). Our models with helium-enhanced subpopulations also predict that the well-known Burstein relation can be explained by the fraction of helium-enhanced subpopulation, the mean age, and the mean metallicity of the underlying stellar populations (Figure 1. right panel).

To enhance the lifetime of large-sized active matrix organic light emitting diodes (AMOLEDs), we developed a liquid desiccant for encapsulation. The liquid desiccant was prepared by mixing nano-sized calcium oxide (CaO) powders and silicone binder including polyalkylalkenylsiloxane, polyalkylhydrogensiloxane and platinum compound. It was confirmed that liquid desiccant had an effect on absorption of penetrated moisture and oxygen through calcium tests. Also, the test cells encapsulated with only epoxy sealant dispensed at the edge of the cell developed dark spots within 100 hrs, which grew larger with time at 85 oC and 85 % R.H. On the other hand, the test cell sealed with epoxy sealant and liquid desiccant showed no dark spots and retained 97% of its initial luminance even after being stored for 800 hrs at 85 oC and 85 % R.H. Furthermore, the accelerating storage lifetimes of 31-inch bottom-emitting AMOLEDs with epoxy sealant and liquid desiccant showed about 1000 hrs. These results suggest that the liquid desiccant can be applied to encapsulation of large-sized AMOLEDs.

We investigate the empirical relation between corporate governance and stock market liquidity. We find that firms with better corporate governance have narrower spreads, higher market quality index, smaller price impact of trades, and lower probability of information-based trading. In addition, we show that changes in our liquidity measures are significantly related to changes in the governance index over time. These results suggest that firms may alleviate information-based trading and improve stock market liquidity by adopting corporate governance standards that mitigate informational asymmetries. Our results are remarkably robust to alternative model specifications, across exchanges, and to different measures of liquidity.

This paper develops a controller for position tracking of a new ball wheel drive mechanism for a robust omnidirectional wheeled mobile platform, an adaptive controller with physical parameter estimation. This platform, integrated with a manipulator, is designed for use in highway maintenance and construction, which is a generally unstructured and congested environment. The proposed ball wheel mechanism can move in all directions on the plane, instantaneously and isotropically. Reconfiguration of the redundant drive system of the ball wheel mechanism is accomplished by altering the contact pressure between the drive wheels and the sphere based on platform heading direction. The system redundancy is resolved through a Weighted Optimal Torque Distribution method allowing for smooth reconfiguration. Finally, experimental and simulation results demonstrate the effectiveness of the approach.

The hot He-burning horizontal-branch (HB) stars and their progeny are most likely dominant ultraviolet (UV) sources in the old stellar population systems such as globular clusters (GCs). Integrated FUV flux can be an age indicator of GCs and allow us to investigate age distributions of GCs within a given galaxy or between galaxies. The unprecedented set of UV photometry for M31 by Galaxy Evolution Explorer (GALEX), coupled with most recent detailed population models enable to study detailed global UV properties of M31 GCs.

We propose a pre-electrical bias aging to reduce threshold voltage (Vth) shift of hydrogenated- amorphous silicon thin-film transistor (a-Si:H TFT) for AMOLED display. The quantity of Vth shift in the sample subjected to a bias-aging is reduced due to the reduction of created dangling bond density, compared with a sample without a bias-aging. When an identical stress duration of 50,000 sec is applied to a-Si:H TFT with or without a pre-electrical bias-aging, the created dangling bond density (ΔNDB) after a pre-electrical bias-aging is decreased from 1.38 × 1011/cm2 to 0.685 × 1011/cm2. Our experimental results indicate that after the pre-electrical bias aging, a newly created dangling bond during an electrical stress is decreased because a weak bond density and hydrogen diffusion may be decreased.

Metal contamination in Si and SiO2 films deposited by plasma-enhanced chemical vapor deposition (PECVD) in the fabrication of low-temperature poly Si thin-film transitor was investigated. Aluminum was the major metal impurity to have the highest concentration. Segregation of Al was always observed in the films deposited at temperatures above 400 °C. The impurity level in the segregated region was 1018 ∼ 1020 atoms/cm3 for Al, while the concentration in matrix was about 1016 atoms/cm3. From the transmission electron microscopy image, the Al segregated region contains small-size Al precipitates. Although the Al impurity level of 1016 atoms/cm3 did not cause any serious degradation of device performance, the level of 1018 atom/cm3 and higher can induce a fatal degradation of the threshold voltage. This study revealed that the Al originated from the PECVD chamber, carbon precipitates provided the preferred sites for Al precipitates, and the solubility and diffusivity of Al in Si accelerated the segregation of Al.