ORGANIC DUST IN THE INTERSTELLAR MEDIUM

KWOK, SUN The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

The traditional view of dust in the interstellar medium is that it is made of graphite and silicates. In this paper, we discuss the evidence for complex organics being a major component of interstellar dust. Comparison between astronomical infrared spectra and laboratory spectra of amorphous carbonaceous materials suggests that organics of mixed aromatic-aliphatic structures are widely present in circumstellar, interstellar, and galactic environments. Scenarios for the synthesis of these compounds in the late stages of stellar evolution are presented.

PLANETARY NEBULAE: NEW CHALLENGES IN THE 21ST CENTURY

KWOK SUN The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2

Athough planetary nebulae (PNe) have been discovered for over 200 years, it was not until 30 years ago that we arrived at a basic understanding of their origin and evolution. Even today, with observations covering the entire electromagnetic spectrum from radio to X-ray, there are still many unanswered questions on their structure and morphology. In this review, we summarize recent theoretical and observational advances in PNe research, and discuss the roles of PNe in the chemical (atomic, molecular, and solid-state) enrichment of the galaxy and as tracers of the large scale structure of the Universe.

Retinoic acid attenuates Sjögren’s syndrome via regulation of IL-17 producing CCR9+T cells and Salivary gland inflammation

Sun-Hee Hwang,Jin Seok Woo,SeungCheon Yang,Jin-Sil Park,JeongWon Choi,Kun Hee Lee,Seung-Ki Kwok,Sung-Hwan Park,Mi-La Cho 한국실험동물학회 2021 한국실험동물학회 학술발표대회 논문집 Vol.2021 No.7

Previous studies have evaluated the roles of T and B cells in the pathogenesis of Sjögren’s syndrome (SS); however, their relationships with age-dependent and metabolic abnormalities remain unclear. We examined the impacts of changes associated with aging or metabolic abnormalities on populations of T and B cells and SS disease severity. To investigate the effects of retinoic acid (RA) on SS disease severity, we examined serum levels of RA following RA administration to NOD/ShiLtJ mice, which are a spontaneous type 1 diabetes (T1D) SS animal model. The serum retinoic acid (RA) level was examined in NOD/ShiLtJ mice and SS patients. We detected increased populations of IL-17-producing T and B cells in the salivary glands of NOD/ShiLtJ mice. Inflammation-induced human submandibular gland cell death, determined based on p-MLKL and RIPK3 expression levels, was significantly increased by IL-17 treatment. Among IL-17-expressing cells in the salivary gland, peripheral blood, and spleen, the α4β7 (gut-homing integrin)-negative population was significantly increased in aged NOD/ShiLtJ mice. The α4β7-positive population markedly increased in the intestines of aged NOD/ShiLtJ mice following RA treatment. The therapeutic efficacy of RA was also confirmed in the SS animal model. Serum levels of RA were significantly lower in SS patients than in the healthy control group. A significant increase in α4β7-negative IL-17-expressing cells in salivary glands may be involved in the onset and progression of SS. These results suggest the potential therapeutic utility of RA in SS treatment.

Rational combination therapy with PARP and MEK inhibitors capitalizes on therapeutic liabilities in <i>RAS</i> mutant cancers

Sun, Chaoyang,Fang, Yong,Yin, Jun,Chen, Jian,Ju, Zhenlin,Zhang, Dong,Chen, Xiaohua,Vellano, Christopher P.,Jeong, Kang Jin,Ng, Patrick Kwok-Shing,Eterovic, Agda Karina B.,Bhola, Neil H.,Lu, Yiling,Wes American Association for the Advancement of Scienc 2017 Science translational medicine Vol.9 No.392

<P>Mutant <I>RAS</I> has remained recalcitrant to targeted therapy efforts. We demonstrate that combined treatment with poly(adenosine diphosphate–ribose) polymerase (PARP) inhibitors and mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitors evokes unanticipated, synergistic cytotoxic effects in vitro and in vivo in multiple <I>RAS</I> mutant tumor models across tumor lineages where <I>RAS</I> mutations are prevalent. The effects of PARP and MEK inhibitor combinations are independent of <I>BRCA1/2</I> and <I>p53</I> mutation status, suggesting that the synergistic activity is likely to be generalizable. Synergistic activity of PARP and MEK inhibitor combinations in <I>RAS</I> mutant tumors is associated with (i) induction of BIM-mediated apoptosis, (ii) decrease in expression of components of the homologous recombination DNA repair pathway, (iii) decrease in homologous recombination DNA damage repair capacity, (iv) decrease in DNA damage checkpoint activity, (v) increase in PARP inhibitor–induced DNA damage, (vi) decrease in vascularity that could increase PARP inhibitor efficacy by inducing hypoxia, and (vii) elevated PARP1 protein, which increases trapping activity of PARP inhibitors. Mechanistically, enforced expression of FOXO3a, which is a target of the RAS/MAPK pathway, was sufficient to recapitulate the functional consequences of MEK inhibitors including synergy with PARP inhibitors. Thus, the ability of mutant <I>RAS</I> to suppress FOXO3a and its reversal by MEK inhibitors accounts, at least in part, for the synergy of PARP and MEK inhibitors in <I>RAS</I> mutant tumors. The rational combination of PARP and MEK inhibitors warrants clinical investigation in patients with <I>RAS</I> mutant tumors where there are few effective therapeutic options.</P>

Design of 1500V solar inverter stack beyond megawatt in NPC1 topology

Xin Hao,Kwok-Wai Ma,Jia Zhao,Xin-Yu Sun 전력전자학회 2017 전력전자학술대회 논문집 Vol.2017 No.7

This paper describes a design concept of NPC1 power stack for 1500VDC megawatt level solar inverter. This stack uses three latest half-bridge IGBT modules with highest power density and operation junction temperature, which enable realization of power level beyond 1MW without paralleling. Critical design concept on loop inductance is explained. Dynamic characteristics are verified by double-pulse test. Thermal characteristics and output power limits are verified by thermal test. Temperature-sensitive component on PCB as output power constraint is identified. Different PCB repositioning solutions are tested to give the overall output power thermal derating curves, which enable output power of 1.15MW at TA=55°C with 15°C thermal margin. The power stack characteristic and performance change under different thermal environment is further analyzed.

Semi-Lagrangian Reproducing Kernel Particle Method for Slope Stability Analysis and Post-Failure Simulation

On-Lei Annie Kwok,Pai-Chen Guan,Wei-Po Cheng,Chien-Ting Sun 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.1

Slope stability analyses are often performed using Limit Equilibrium Methods (LEMs) and Finite Element Method (FEM). However, these methods can only model the slope condition up to the point of failure. Meshfree methods, which do not require amesh or a grid in the simulation process, have the potential to model the post-failure slope behavior as mesh tangling would not occurto cause numerical instability and non-convergence. Hence, while retaining the benefits of conventional numerical schemes,meshfree method can be more advantageous when problems with large deformation are encountered. In this paper, Semi-LagrangianReproducing Kernel Particle Method (SLRKPM), which is a type of meshfree method, is extended to analyze geomechanicsproblems such as the stability of a slope and post failure slope behavior. The results from SLRKPM agree well with those fromconvention methods (LEMs and FEM) in terms of factor-of-safety and failure surface. In addition, SLRKPM is able to simulate theslope failure process and successfully capture the development of shear band. This proves that SLRKPM has a significant advantageover FEM when dealing with problems involving large deformation and failure of geomaterials.

Soluble Fas ligand inhibits angiogenesis in rheumatoid arthritis

Kim, Wan-Uk,Kwok, Seung-Ki,Hong, Kyung-Hee,Yoo, Seung-Ah,Kong, Jin-Sun,Choe, Jongseon,Cho, Chul-Soo BioMed Central 2007 ARTHRITIS RESEARCH AND THERAPY Vol.9 No.2

<P>The characteristics of rheumatoid arthritis (RA) pathology include the infiltration of inflammatory leukocytes, the proliferation of synovial cells, and the presence of extensive angiogenesis, referred to as rheumatoid pannus. Fas ligand is critical to the homeostatic regulation of the immune response, but its role in the angiogenic process of RA remains to be defined. In this study, we investigated whether soluble Fas ligand (sFasL) induces synoviocyte apoptosis and regulates angiogenesis of endothelial cells in RA. The levels of sFasL were elevated in the synovial fluids of RA patients when compared to those of osteoarthritis (OA) patients, and they correlated inversely with vascular endothelial growth factor<SUB>165 </SUB>(VEGF<SUB>165</SUB>) concentrations. sFasL, ranging from 10 to 100 ng/ml, induced the apoptosis of RA fibroblast-like synoviocytes (FLS) <I>in vitro</I>, and thereby decreased VEGF<SUB>165 </SUB>production. In addition, sFasL inhibited VEGF<SUB>165</SUB>-induced migration and chemotaxis of endothelial cells to basal levels in a manner independent of the Fas-mediated cell death. sFasL dose-dependently suppressed the VEGF<SUB>165</SUB>-stimulated increase in pAkt expression in endothelial cells, which might be associated with its anti-migratory effect on endothelial cells. Moreover, sFasL strongly inhibited neovascularization in the Matrigel plug <I>in vivo</I>. Our data suggest that sFasL shows anti-angiogenic activity within RA joints not only by inducing apoptosis of VEGF<SUB>165</SUB>-producing cells but also by blocking VEGF<SUB>165</SUB>-induced migration of endothelial cells, independent of Fas-mediated apoptosis.</P>

면역 적격 환자에서 복벽에 발생한 결핵성 농양 1 예

곽승기(Seung Ki Kwok),장우임(U Im Chang),이태규(Tae Kyu Lee),추교영(Kyo Young Choo),김진일(Jin Il Kim),박수헌(Soo Heon Park),한준열(Joon Yeol Han),김재광(Jae Kwang Kim),정규원(Kyu Won Chung),선희식(Hee Sik Sun) 대한소화기학회 2001 대한소화기학회지 Vol.38 No.3

Tuberculosis of the abdominal wall is relatively uncommon and most cases were caused by a spread of the infection from tuberculous abdominal lymph nodes. Autopsy studies have shown abdominal wall involvement in less than 1% of patients who died of tuberculosis. We have experienced a case of the tuberculous abscess in the abdominal wall. A 21-year-old woman was admitted for the evaluation of a soft mass at the right upper abdomen. A 15×5×4 cm sized abscess in the abdominal wall was detected by ultrasonogram and CT. Abscess was drained by ultrasonogram-guided aspiration. The confirmed diagnosis of tuberculous abscess was made by means of polymerase chain reaction of the aspirated fluid from the mass. The patient was successfully treated with anti-tuberculosis therapy of four drug regimens. To our knowledge, this is the first report of tuberculous abscess developed in the abdominal wall in Korea. (Korean J Gastroenterol 2001;38:220-223)

Impact of interleukin-21 in the pathogenesis of primary Sjogren's syndrome: increased serum levels of interleukin-21 and its expression in the labial salivary glands

Kang, Kwi Young,Kim, Hyun-Ok,Kwok, Seung-Ki,Ju, Ji Hyeon,Park, Kyung-Su,Sun, Dong-Il,Jhun, Joo Yeon,Oh, Hye Jwa,Park, Sung-Hwan,Kim, Ho-Youn BioMed Central 2011 ARTHRITIS RESEARCH AND THERAPY Vol.13 No.5

<P><B>Introduction</B></P><P>Interleukin (IL)-21 is a cytokine that controls the functional activity of effector T helper cells and the differentiation of Th17 cells, and promotes B-cell differentiation. To test whether IL-21 participates in the pathogenesis of primary Sjögren's syndrome (SS), serum IL-21 level was measured and IL-21 expression in the labial salivary glands (LSG) was examined.</P><P><B>Methods</B></P><P>Serum IL-21 levels in 40 primary SS, 40 rheumatoid arthritis (RA), and 38 systemic lupus erythematosus (SLE) patients and 20 healthy controls were measured. Serum IL-21 levels of SS patients were assessed for correlations with laboratory data, including anti-nuclear antibody, anti-Ro/La antibodies, globulin, immunoglobulin (Ig) class, and IgG subclass. LSGs from 16 primary SS and 4 controls with sicca symptoms were evaluated for IL-21 and IL-21 receptor (IL-21R) expression by immunohistochemistry. Confocal microscopy was performed to further characterize the IL-21 positive cells.</P><P><B>Results</B></P><P>Primary SS patients had significantly higher serum IL-21 levels than controls, and these increments correlated positively with levels of IgG, IgG1. Serum IgG1 levels correlated with anti-Ro antibody titers. Immunohistochemical analyses showed that lymphocytic foci and the periductal area of the LSGs from SS patients expressed high levels of IL-21 and lower levels of IL-21R, whereas the control LSGs showed minimal expression of both antigens. The more the lymphocyte infiltrated, IL-21expression in LSGs showed a tendency to increase. Confocal microscopic analyses revealed that IL-21 expressing infiltrating lymphocytes in the LSGs of SS patients also expressed CXCR5.</P><P><B>Conclusions</B></P><P>Primary SS is associated with high serum IL-21 levels that correlate positively with serum IgG, especially IgG1, levels. The expression of IL-21 is increased as more lymphocytes infiltrated in LSGs. These observations suggest that IL-21 may play an important role in primary SS pathogenesis.</P>

Combinatory treatment using tacrolimus and a STAT3 inhibitor regulate Treg cells and plasma cells

Park, Jin-Sil,Kim, Sung-Min,Hwang, Sun-Hee,Choi, Si-Young,Kwon, Ji Ye,Kwok, Seung-Ki,Cho, Mi-La,Park, Sung-Hwan SAGE Publications 2018 International journal of immunopathology and pharm Vol.32 No.-

<P>Systemic lupus erythematosus (SLE; lupus) is a prototypical autoimmune disease characterized by circulating autoantibodies to nuclear antigens and immune complex deposition, resulting in damage to target organs. To investigate the effects of tacrolimus (TAC) on effector T cells and B cells, we examined its involvement in the development of effector T cells, germinal center (GC) B cells, and plasma cells in an in vitro system using wild-type (WT) and lupus-prone mice. The population of T helper (Th) 1, Th2, and Th17 cells interleukin (IL)-17-producing T (Th17) cells and the production of interferon-γ and interleukin-17A IL-17A were suppressed by TAC. TAC also reduced the population of regulatory T (Treg) cells; however, a combination treatment with the signal transducer and activator of transcription 3 (STAT3) inhibitor STA-21 promoted the population of Treg cells. TAC also suppressed the populations of GC B cells and plasma cells synergistically with STA-21. These findings suggest that the application of TAC with a STAT3 signal inhibitor may provide benefits in SLE treatment.</P>