Chung-Ang University

About: Chung-Ang University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Thin film. The organization has 13381 authors who have published 26978 publications receiving 416735 citations. The organization is also known as: CAU & Chung.

Green Synthesis of Silver Nanoparticles Using Pseudoduganella eburnea MAHUQ-39 and Their Antimicrobial Mechanisms Investigation against Drug Resistant Human Pathogens.

Abstract: Silver nanoparticles (AgNPs) have shown great promise in biomedical applications. The exact mechanism and mode of action of AgNPs regarding antimicrobial activity are still not well known. Moreover, synthesis of nanoparticles by physical and chemical methods is expensive and not ecofriendly. This study highlights the green, rapid, facile, cost-effective and ecofriendly synthesis of AgNPs using Pseudoduganella eburnea MAHUQ-39 and also investigates their antibacterial mechanisms. The transmission electron microscopy (TEM) image revealed a spherical shape of the AgNPs. The size of the synthesized AgNPs was 8 to 24 nm. The elemental mapping and selected area electron diffraction (SAED) and X-ray diffraction (XRD) patterns revealed the crystalline structure of AgNPs. Fourier-transform infrared spectroscopy (FTIR) analysis identified the functional groups that are involved in the reduction of silver ion to AgNPs. The green synthesized AgNPs exhibited strong antimicrobial activity against multidrug-resistant pathogenic microbes. Minimal inhibitory concentrations (MICs) of Staphylococcus aureus and Pseudomonas aeruginosa were 100 μg/mL and 6.25 μg/mL, respectively, and the minimum bactericidal concentrations (MBCs) of S. aureus and P. aeruginosa were 200 μg/mL and 50 μg/mL, respectively. Our data demonstrated that synthesized AgNPs created structural changes of cells and destroyed the membrane integrity of strains S. aureus and P. aeruginosa. Therefore, AgNPs synthesized by strain MAHUQ-39 can be used as a powerful antimicrobial agent for various therapeutic applications.

Inhibition of Ion Migration for Reliable Operation of Organolead Halide Perovskite-Based Metal/Semiconductor/Metal Broadband Photodetectors

Abstract: Organolead halide perovskites (OHPs) have attracted extensive attention as light harvesting materials for solar cells recently, because of their high charge carrier mobility, high photoconversion efficiencies, low cost, and simple methodology. Despite these advantages, the OHPs exhibit sweep-dependent hysteresis behavior in current–voltage characteristics films, deteriorating the reliability of devices based on the OHPs. This study demonstrates reliable high on/off ratio (Ion/Ioff = 104) CH3NH3PbI3 broadband photodetectors with buffer layer-free simple metal/semiconductor/metal lateral structure. At high external bias, poor on/off ratios and spikes in dark current and photocurrent are observed due to the migration of charged defect ions. The ion migration can be effectively inhibited at low external bias, and thus the devices show high Ion/Ioff ratios and spike-free dark current and photocurrent. In addition, prevention of the prepoling in the CH3NH3PbI3 films by operating at the low external bias results in pronouncedly enhanced signal-to-noise ratios even under low intensity incident light. These results strongly propose that inhibiting the migration of charged defect ions in CH3NH3PbI3 films is a key in developing reliable high performance CH3NH3PbI3-based devices.

Fertility-Related Proteomic Profiling Bull Spermatozoa Separated by Percoll

Abstract: Infertility or subfertility of bovine spermatozoa may lead to disintegration of the breeding system and large economic losses. Recently, proteomics have identified candidates for the sperm fertility biomarkers, but no definite studies have clearly identified the relationship between the proteome and sperm fertility after proteomic study. Therefore, to determine the clinical value of the protein markers identified by proteomic study, we first compared the protein expression profiles of spermatozoa from high and low fertility bulls using 2-dimensional electrophoresis. We then investigated the relationship between protein expression and the fertility of individual bulls as assessed by Western blot analysis. Five proteins, enolase 1 (ENO1), ATP synthase H+ transporting mitochondrial F1 complex beta subunit, apoptosis-stimulating of p53 protein 2, alpha-2-HS-glycoprotein, and phospholipid hydroperoxide glutathione peroxide, were more highly represented in high fertility bulls, whereas three proteins, voltage dependent anion channel 2 (VDAC2), ropporin-1, and ubiquinol-cytochrome-c reductase complex core protein 2 (UQCRC2), were more highly represented in low fertility bulls. Among those proteins, ENO1, VDAC2, and UQCRC2 were significantly correlated with individual fertility. Therefore, these results suggest that concurrent comparisons between protein expression and other fertility assays may represent a good in vitro assay to determine sperm fertility.

A Frequency Selective Surface Based Reconfigurable Rasorber With Switchable Transmission/Reflection Band

Abstract: In this letter, a reconfigurable rasorber has been designed based on switching activity of frequency selective surface (FSS) and resistive FSS. The proposed design consists of two periodic layers separated from each other by an air spacer. The upper layer comprising lumped resistors assists wide absorption band (above 90% absorption) from 3.8 to 10.3 GHz (entire C and partial X Band), whereas PIN diodes are mounted in the bottom layer to enable the switching operation of the rasorber at S-Band. The novelty of the proposed design lies in its reconfigurable transmission/reflection band, which switches from a bandpass response (at around 2.88 GHz) to perfect reflection, with the control of the biasing states of the diode. A sample prototype is also fabricated and experimentally verified. Wide absorption band along with switchable transmission/reflection band characteristics have made the proposed rasorber an excellent choice for various radar cross section reduction applications.

The roles of academic engagement and digital readiness in students’ achievements in university e-learning environments

Abstract: University students, who are assumed to be digital natives, are exposed to campus e-learning environments to improve their academic performance at the beginning of their academic careers. However, previous studies of students’ perceptions of e-learning demonstrate a lack of consistent results with respect to the prediction of their academic achievement. The goal of this study was to examine university students’ perceptions of e-learning, based on their experiences, and the mediating roles of academic engagement and digital readiness within the university context of an e-learning environment for academic achievement. A total of 614 undergraduate students enrolled in a Korean university participated in this study. Using a partial least squares model to develop the theory, we examined students engaging in university e-learning environments in relation to their perceptions of e-learning, digital readiness, academic engagement, and academic achievement (i.e., grade point average). The results are significant for the importance of students’ academic engagement and digital readiness as mediators in their perceptions of e-learning predicted by academic achievement. Although students positively perceived e-learning experiences on campus, they must have strong digital skills to perform academic work and commit to effortful involvement in the context of academic learning in university e-learning environments. Our results provide practical implications for ways to enhance effective adoption of e-learning environments by college students, educators, and administrators.