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An Isothermal Mganetohydrodynamic Code and Its Application to the Parker Instability
KIM JONGSOO,RYU DONGSU,JONES T. W.,HONG S. S. The Korean Astronomical Society 2001 Journal of The Korean Astronomical Society Vol.34 No.4
As a companion to an adiabatic version developed by Ryu and his coworkers, we have built an isothermal magnetohydrodynamic code for astrophysical flows. It is suited for the dynamical simulations of flows where cooling timescale is much shorter than dynamical timescale, as well as for turbulence and dynamo simulations in which detailed energetics are unimportant. Since a simple isothermal equation of state substitutes the energy conservation equation, the numerical schemes for isothermal flows are simpler (no contact discontinuity) than those for adiabatic flows and the resulting code is faster. Tests for shock tubes and Alfven wave decay have shown that our isothermal code has not only a good shock capturing ability, but also numerical dissipation smaller than its adiabatic analogue. As a real astrophysical application of the code, we have simulated the nonlinear three-dimensional evolution of the Parker instability. A factor of two enhancement in vertical column density has been achieved at most, and the main structures formed are sheet-like and aligned with the mean field direction. We conclude that the Parker instability alone is not a viable formation mechanism of the giant molecular clouds.
Jeon, Jongsoo,Ryu, Choong-Min,Lee, Jun-Young,Park, Jong-Hwan,Yong, Dongeun,Lee, Kyungwon American Society for Microbiology 2016 Applied and environmental microbiology Vol.82 No.14
<P>The increasing prevalence of carbapenem-resistant Acinetobacter baumannii (CRAB) strains in intensive care units has caused major problems in public health worldwide. Our aim was to determine whether this phage could be used as an alternative therapeutic agent against multidrug-resistant bacterial strains, specifically CRAB clinical isolates, using a mouse model. Ten bacterio-phages that caused lysis in CRAB strains, including bla(OXA-66-like) genes, were isolated. YMC13/01/C62 ABA BP (phage B phi-C62), which showed the strongest lysis activity, was chosen for further study by transmission electron microscopy (TEM), host range test, one-step growth and phage adsorption rate, thermal and pH stability, bacteriolytic activity test, genome sequencing and bioinformatics analysis, and therapeutic effect of phage using a mouse intranasal infection model. The phage B phi-C62 displayed high stability at various temperatures and pH values and strong cell lysis activity in vitro. The phage B phi-C62 genome has a double-stranded linear DNA with a length of 44,844 bp, and known virulence genes were not identified in silico. In vivo study showed that all mice treated with phage B phi-C62 survived after intranasal bacterial challenge. Bacterial clearance in the lung was observed within 3 days after bacterial challenge, and histologic damage also improved significantly; moreover, no side effects were observed. IMPORTANCE In our study, the novel A. baumannii phage B phi-C62 was characterized and evaluated in vitro, in silico, and in vivo. These results, including strong lytic activities and the improvement of survival rates, showed the therapeutic potential of the phage B phi-C62 as an antimicrobial agent. This study reports the potential of a novel phage as a therapeutic candidate or nontoxic disinfectant against CRAB clinical isolates in vitro and in vivo.</P>
Choi Jongsoo,Ryu Moon-Chul,Kim Jae Jung,최수형,Won Jong-In 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.8
Thermoresponsive protein-based hydrogels have been widely used due to their high potential in biomedical fields. Elastin-like polypeptides (ELPs) are one of the proteins that show lower critical solution temperature (LCST) behavior, resulting in self-assembly above critical micellular temperature (CMT). Here, we utilized ABC-type blocky ELPs to form hydrogels by introducing cross-linking sites, resulting in good mechanical properties. The hydrogels showed temperature-dependent viscoelasticity due to their structure change. Also, the recovery process of ELP-based hydrogels after large deformation is significantly dependent on the types of cross-linking (i.e., ionic, covalent, or ionic-covalent hybrid).
Transonic Magnetohydrodynamic Turbulence
LEE HYESOOK,RYU DONGSU,KIM JONGSOO,JONES T. W. The Korean Astronomical Society 2001 Journal of The Korean Astronomical Society Vol.34 No.4
Compressible, magnetohydrodynamic (MHD) turbulence in two dimension is studied through high-resolution, numerical simulations with the isothermal equation of state. First, hydrodynamic turbulence with Mach number $(M)_{rms}\;\~$1 is generated by enforcing a random force. Next, initial, uniform magnetic field of various strengths with Alfvenic Mach number Ma $\gg$ 1 is added. Then, the simulations are followed until MHD turbulence is fully developed. Such turbulence is expected to exist in a variety of astrophysical environments including clusters of galaxies. Although no dissipation is included explicitly in our simulations, truncation errors produce dissipation which induces numerical resistivity. It mimics a hyper-resistivity in our second-order accurate code. After saturation, the resulting flows are categorized as SF (strong field), WF (weak field), and VWF (very weak field) classes respectively, depending on the average magnetic field strength described with Alfvenic Mach number, $(Ma)_{rms}{\ge}1$, $(Ma)_{rms}{\~}1$, and $(Ma)_{rms}{\gg}1$. The characteristics of each class are discussed.
SIMULATED FARADAY ROTATION MEASURES TOWARD HIGH GALACTIC LATITUDES
Akahori, Takuya,Ryu, Dongsu,Kim, Jongsoo,Gaensler, B. M. IOP Publishing 2013 The Astrophysical journal Vol.767 No.2
<P>We study the Faraday rotation measure (RM) due to the Galactic magnetic field (GMF) toward high Galactic latitudes. The RM arises from the global, regular component as well as from the turbulent, random component of the GMF. We model the former based on observations and the latter using the data of magnetohydrodynamic turbulence simulations. For a large number of different GMF models, we produce mock RM maps around the Galactic poles and calculate various statistical quantities with the RM maps. We find that the observed medians of RMs toward the north and south Galactic poles, similar to 0.0 +/- 0.5 rad m(-2) and similar to+6.3 +/- 0.5 rad m(-2), are difficult to explain with any of our many alternate GMF models. The standard deviation of observed RMs, similar to 9 rad m(-2), is clearly larger than that of simulated RMs. The second-order structure function of observed RMs is substantially larger than that of simulated RMs, especially at small angular scales. We discuss other possible contributions to RM toward high Galactic latitudes. Besides observational errors and the intrinsic RM of background radio sources against which RM is observed, we suggest that the RM due to the intergalactic magnetic field may account for a substantial fraction of the observed RM. Finally, we note that reproducing the observed medians may require additional components or/and structures of the GMF that are not present in our models.</P>