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Search Results: 1 - 10 of 50420 matches for " Young Jin Kim "
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Mirage Cosmology in M-theory
Jin Young Kim
Physics , 2002, DOI: 10.1016/S0370-2693(02)02815-0
Abstract: We extend the idea of mirage cosmology to M-theory. Considering the motion of a probe brane in the M-theory background generated by a stack of non-threshold (M2,M5) bound states, we study the cosmological evolution of the brane universe in this background. We estimate the range of $r$ where the formalism is valid. Effective energy density on the probe brane is obtained in terms of the scale factor. Comparing the limiting case of the result with that from type IIB background, we confirm that the cosmological evolution by mirage matter is a possible scenario in the M-theory context.
Dilaton-driven brane inflation in type IIB string theory
Jin Young Kim
Physics , 2000, DOI: 10.1103/PhysRevD.62.065002
Abstract: We consider the cosmological evolution of the three-brane in the background of type IIB string theory. For two different backgrounds which give nontrivial dilaton profile we have derived the Friedman-like equations. These give the cosmological evolution which is similar to the one by matter density on the universe brane. The effective density blows up as we move towards the singularity showing the initial singularity problem. The analysis shows that when there is axion field in the ambient space the recollapsing of the universe occurs faster compared with the case without axion field.
Brane inflation in tachyonic and non-tachyonic type 0B string theories
Jin Young Kim
Physics , 2000, DOI: 10.1103/PhysRevD.63.045014
Abstract: We consider the motion of the brane universe moving in a background bulk space of tachyonic and non-tachyonic type 0B string theory. The effective densities are calculated for both cases and they show different power law behavior. Brane inflation for non-tachyonic type 0B background has the same power law behavior as that for type IIB background. The brane inflation under tachyonic background is less divergent than the one without tachyon. The role of tachyonic field in brane inflation scenario is different from that of the ordinary matter field.
Absorption of dilaton s-wave in type 0B string theory
Jin Young Kim
Physics , 1999, DOI: 10.1103/PhysRevD.61.084020
Abstract: We find the absorption probability of dilaton field in type 0B string theory. Since the background solutions are of the form $AdS_5 \times S^5$ on both regions, we use the semiclassical formalism adopted in type IIB theory to find the absorption cross section. The background tachyon field solution was used as a reference to relate the solutions of the two regions. We also consider the possible corrections to absorption probability and the $\ln(\ln z)$ form of the correction is expected as in the calculation of the confinement solution.
Stability and fluctuation modes of giant gravitons with NSNS B field
Jin Young Kim
Physics , 2001, DOI: 10.1016/S0370-2693(02)01233-9
Abstract: We study the stability of the giant gravitons in the string theory background with NSNS B field. We consider the perturbation of giant gravitons formed by a probe D$(8-p)$ brane in the background generated by D$(p-2)$-D$(p)$ branes for $2 \le p \le 5$. We use the quadratic approximation to the brane action to find the equations of motion. For $p=5$, giant graviton configurations are stable independent of the size of the brane. For $p \ne 5$, we calculated the range of the size of the brane where they are stable. We also present the mode frequencies explicitly for some special cases.
Bending of electromagnetic wave in an ultra-strong magnetic field
Jin Young Kim
Physics , 2012, DOI: 10.1088/1475-7516/2012/10/056
Abstract: We consider the bending of light by nonlinear electrodynamics when the magnetic field $B$ exceeds the critical value $B_{\rm c}$. Using the index of refraction derived from the analytic series representation in one-loop effective action of QED, we found the trajectory and the bending angle of light in geometric optics. The angle bent by ultra-strong magnetic field of magnetar was estimated and compared with the gravitational bending. The result may be useful in studying the lensing, birefringence, and other nonlinear quantum electrodynamic effects above $B_{\rm c}$.
Clinical Response to Treatment of Central Nervous System Tuberculosis in Non-Human Immunodeficiency Virus-Infected Adolescents and Adults  [PDF]
Jin Young Lee, Su Jin Lee, Ji Young Park, Min Jeong Kim
Journal of Tuberculosis Research (JTR) , 2016, DOI: 10.4236/jtr.2016.44020
Abstract: Introduction: More than half of patients with central nervous system tuberculosis (CNS TB) die or are left with severe neurological deficits despite receiving anti-TB treatment. Aims of the study: This study examined risk factors associated with poor response to initial treatment with four anti-TB drug regimens or three drug regimens with steroids as adjuvant therapy. Methods: This study analyzed medical records from two tertiary hospitals in Busan, Korea, between January 2009 and March 2012. The subjects were non-human immunodeficiency virus (HIV)-infected patients aged ≥16 years with clinical CNS TB. The subjects were divided into two groups according to response to treatment. Results: In totally, 52 patients with CNS TB were included. Of these, 14 (26%) and 38 (73%) showed poor and good responses, respectively. Of the patients with poor response, nine had stage III disease (64.3%) according to the British Medical Research Council (BMRC) staging system. A significantly higher proportion was seen in the good response group (p < 0.05). Patients with positive cerebrospinal fluid (CSF) acid-fast bacillus (AFB) culture, positive sputum AFB culture, positive CSF TB polymerase chain reaction (PCR) results, and brain tuberculoma had poorer responses (p < 0.05). Multivariate analysis to determine risk factors associated with poor response to anti-TB therapy revealed that a poor response was associated with stage III clinical signs upon diagnosis (odds ratio [OR] 32.122; 95% confidence interval [CI] 2.221 - 464.605), positive sputum AFB culture (OR 13.624; 95% CI 1.066 - 174.149), and tuberculoma on brain images (OR 45.714; 95% CI 1.893 - 1104.018). Conclusions: The results demonstrate the importance of identifying the severity of CNS TB and promptly administering anti-TB drugs. It is necessary to perform drug susceptibility testing for anti-TB drugs. Further studies are needed to confirm the correlations between risk factors associated with poor response and anti-TB drug resistance and the other risk factors.
Experimental Study on the Ultimate Shear Performance of Elastomeric Bearings of Doublefold Elastomeric Layer  [PDF]
Hyejin Yoon, Im Jong Kwahk, Young Jin Kim
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.51014
Abstract:

The elastomeric bearings shall not fail nor degrade the durability of the bridge due to the loss of its properties during its service life. Since the elastomeric bearings can be used in the seismic design complementarily to seismic devices, even if it is not a seismic isolator, they particularly should secure high shear performance. For elastomeric bearings to behave monolithically, the internal rubber which is located between the steel plates should be single rubber layer. In this study, a series of elastomeric bearings were fabricated and ultimate shear performance was investigated. Some specimens are of single elastomeric layer, the other are of doublefold elastomeric layer. Shear fatigue tests and ultimate shear tests were carried out. Tests results show that the elastomeric bearings whose internal rubber layer is formed by agglomeration of several rubber pads is likely to experience significant loss of its shear performance or early failure.

HSF1-mediated oxidative stress response to menadione in Saccharomyces cerevisiae KNU5377Y3 by using proteomic approach  [PDF]
Il-Sup Kim, Hyun Kim, Young-Saeng Kim, Ingnyol Jin, Ho-Sung Yoon
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.41007
Abstract: The hat shock transcription factor HSF1 inthe yeast Saccharomyces cerevisiae regulates a wide range of genes and functions in diverse cellular reactions. To investigate the physiological response of HSF1 inthe presence of menadione (MD) in S. cerevisiae KNU 5377Y3, wild-type (k3wt) and isogenic hsf1 mutant (k3h1) cells were introduced. HSF1 was induced when k3wt cells were exposed to the superoxide-generating agent MD and k3h1 cells were hypersensitive to MD. Under MD stress, k3h1 cells down-regulated the expression of metabolic enzymes (Hxk, Fba1, Pgk1, Eno2, and Adh1), antioxidant enzymes (Trx2 and porin), and molecular chaperones and their cofactors (Hsp104, Ssb1, Hsp60, Hsp42, Hsp26, Hsp12, Cpr1, and Sti1). In addition, k3h1 cells increased cellular hydroperoxide levels and protein carbonylation under MD stress as compared to k3wt cells. However, there was a moderate difference in the wild-type (b3wt) and mutant (b3h1) cells derived from S. cerevisiae S288Cunder the same conditions. Thus, these results show that HSF1 is an important component of the stress response system, acting as an activator of cell rescue genes in S. cerevisiae KNU5377Y3, and its expression protects the cells from MD-induced oxidative damage by maintaining redox homeostasis and proteostasis in the presence of MD.
The Expression of Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases in Idiopathic Interstitisal Pneumonia  [PDF]
Ji Young Shin, Yu Jin Kim, Sun Young Kyung, Seung Yeon Ha, Sung Hwan Jeong
Open Journal of Respiratory Diseases (OJRD) , 2014, DOI: 10.4236/ojrd.2014.43014
Abstract:
Background: Idiopathic interstitial pneumonia is characterized by fibroblast proliferation and extracellular matrix (ECM) accumulation. Matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) have been shown to regulate remodeling of the ECM, which indicates that they are important factors in the process of lung fibrosis. Therefore, we evaluated the expression of MMPs and TIMPs in tissues obtained from patients with idiopathic interstitial pneumonia and control tissues. Methods: Thirty-seven patients who were diagnosed with IIP (22: IPF, 13: NSIP, 2: COP) and 5 controls were enrolled in this study. The MMP-2 and -9 activity in lung tissue obtained from these patients was analyzed using gelatin zymography and the levels of TIMP-1 and -2 were measured by western blotting. We also evaluated the expression of MMP-2 and -9, as well as that of TIMP-1 and -2 in lung tissue using immunohistochemistry. Results: The levels of MMP-2 and MMP-9 were significantly increased in patients with IPF compared to those with NSIP and COP. The activities of TIMP-1 and -2 were also higher in patients with IPF than NSIP/COP patients and control subjects. There were no significant differences observed in the activities of MMPs and TIMPs obtained from patients with NSIP/COP and control subjects. The immunohistochemical analysis showed that TIMP-2 and MMP-2 were strongly stained at the fibroblasts of the fibroblastic foci in patients with IPF. Conclusions: These results suggest that over-expression of gelatinases and TIMPs in patients with IPF are important factors in the irreversible fibrosis that is associated with lung parenchyma.
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