Kwangwoon University

About: Kwangwoon University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Thin film & Resonator. The organization has 4020 authors who have published 8217 publications receiving 104365 citations.

A comparative study for the inactivation of multidrug resistance bacteria using dielectric barrier discharge and nano-second pulsed plasma

Abstract: Bacteria can be inactivated through various physical and chemical means, and these have always been the focus of extensive research. To further improve the methodology for these ends, two types of plasma systems were investigated: nano-second pulsed plasma (NPP) as liquid discharge plasma and an Argon gas-feeding dielectric barrier discharge (Ar-DBD) as a form of surface plasma. To understand the sterilizing action of these two different plasma sources, we performed experiments with Staphylococcus aureus (S. aureus) bacteria (wild type) and multidrug resistant bacteria (Penicillum-resistant, Methicillin-resistant and Gentamicin-resistant). We observed that both plasma sources can inactivate both the wild type and multidrug-resistant bacteria to a good extent. Moreover, we observed a change in the surface morphology, gene expression and β-lactamase activity. Furthermore, we used X-ray photoelectron spectroscopy to investigate the variation in functional groups (C-H/C-C, C-OH and C=O) of the peptidoglycan (PG) resulting from exposure to plasma species. To obtain atomic scale insight in the plasma-cell interactions and support our experimental observations, we have performed molecular dynamics simulations to study the effects of plasma species, such as OH, H2O2, O, O3, as well as O2 and H2O, on the dissociation/formation of above mentioned functional groups in PG.

Measurement of grain moisture content using microwave attenuation at 10.5 GHz and moisture density

Abstract: The dielectric properties of Korean short-grain rough rice, brown rice and barley with moisture content ranges of 11% to 27%, 11% to 18%, and 11 to 21%, wet basis, respectively, were characterized to develop a prototype grain moisture meter using microwave attenuation at 10.5 GHz and moisture density. A third-order polynomial regression model was proposed to describe the relationship between dielectric properties and moisture density. The prototype grain moisture meter consisted of a dielectric resonator type oscillator of 10.5 GHz, horn antenna, rectangular sample holder, load cell, temperature sensor, detector, and digital voltmeter. The calibration equation for measurement of grain moisture content was developed and estimated with Korean short-grain rough rice (12% to 26%). The coefficient of determination, standard error of prediction (SEP), and bias were 0.986, 0.52% moisture content and 0.07% moisture content, respectively.

Antibacterial activities of Cu-MOFs containing glutarates and bipyridyl ligands

Abstract: Metal-organic frameworks (MOFs) can be utilized as antibacterial agents due to their effective antibacterial activities. Four three-dimensional (3D) Cu-MOFs formulated as [Cu2(Glu)2(μ-L)]·x(H2O) (Glu is glutarate, and L is bpy = 4,4'-bipyridine (1), bpa = 1,2-bis(4-pyridyl)ethane (2), bpe = 1,2-bis(4-pyridyl)ethylene (3), and bpp = 1,2-bis(4-pyridyl)propane (4)) were synthesized by hydrothermal reactions or modified literature methods. Their solid-state structures were slightly modified to increase their hydrolytic stabilities in aqueous solution. Despite the seemingly sufficient void spaces in all the solvent-free MOFs, only the thermally activated form of MOF 2 displayed selective gas uptake ability for CO2 over N2 and H2. The antibacterial activities of the four Cu-MOFs, 1, 2, 3, and 4, were investigated by determining their minimal bactericidal concentration (MBC) values against five strains of bacteria, including E. coli, S. aureus, K. pneumonia, P. aeruginosa, and MRSA, which can be easily met in our daily surrounding environments. Although these Cu-MOFs were found to be structurally very stable in aqueous medium during antibacterial activity tests, they exhibited excellent antibacterial activities against all five kinds of bacteria, including Gram-positive bacteria (S. aureus and MRSA) and Gram-negative bacteria (E. coli, K. pneumonia, and P. aeruginosa), with very low MBCs. The robust 3D frameworks with surface active metal sites rather than the small amount of leached CuII ions may participate more strongly in inactivating various kinds of bacteria and reduce potential cytotoxicity mainly caused by leached metal ions.