831 results on '"Dong Seok Kim"'
Search Results
2. Novel, thalidomide-like, non-cereblon binding drug tetrafluorobornylphthalimide mitigates inflammation and brain injury
- Author
-
Daniela Lecca, Shih-Chang Hsueh, Weiming Luo, David Tweedie, Dong Seok Kim, Abdul Mannan Baig, Neil Vargesson, Yu Kyung Kim, Inho Hwang, Sun Kim, Barry J. Hoffer, Yung-Hsiao Chiang, and Nigel H. Greig
- Subjects
Neuroinflammation ,Thalidomide ,Cereblon ,Immunomodulatory imide drugs (IMiDs) ,Neurodegeneration ,Microglia ,Medicine - Abstract
Abstract Background Quelling microglial-induced excessive neuroinflammation is a potential treatment strategy across neurological disorders, including traumatic brain injury (TBI), and can be achieved by thalidomide-like drugs albeit this approved drug class is compromised by potential teratogenicity. Tetrafluorobornylphthalimide (TFBP) and tetrafluoronorbornylphthalimide (TFNBP) were generated to retain the core phthalimide structure of thalidomide immunomodulatory imide drug (IMiD) class. However, the classical glutarimide ring was replaced by a bridged ring structure. TFBP/TFNBP were hence designed to retain beneficial anti-inflammatory properties of IMiDs but, importantly, hinder cereblon binding that underlies the adverse action of thalidomide-like drugs. Methods TFBP/TFNBP were synthesized and evaluated for cereblon binding and anti-inflammatory actions in human and rodent cell cultures. Teratogenic potential was assessed in chicken embryos, and in vivo anti-inflammatory actions in rodents challenged with either lipopolysaccharide (LPS) or controlled cortical impact (CCI) moderate traumatic brain injury (TBI). Molecular modeling was performed to provide insight into drug/cereblon binding interactions. Results TFBP/TFNBP reduced markers of inflammation in mouse macrophage-like RAW264.7 cell cultures and in rodents challenged with LPS, lowering proinflammatory cytokines. Binding studies demonstrated minimal interaction with cereblon, with no resulting degradation of teratogenicity-associated transcription factor SALL4 or of teratogenicity in chicken embryo assays. To evaluate the biological relevance of its anti-inflammatory actions, two doses of TFBP were administered to mice at 1 and 24 h post-injury following CCI TBI. Compared to vehicle treatment, TFBP reduced TBI lesion size together with TBI-induction of an activated microglial phenotype, as evaluated by immunohistochemistry 2-weeks post-injury. Behavioral evaluations at 1- and 2-weeks post-injury demonstrated TFBP provided more rapid recovery of TBI-induced motor coordination and balance impairments, versus vehicle treated mice. Conclusion TFBP and TFNBP represent a new class of thalidomide-like IMiDs that lower proinflammatory cytokine generation but lack binding to cereblon, the main teratogenicity-associated mechanism. This aspect makes TFBP and TFNBP potentially safer than classic IMiDs for clinical use. TFBP provides a strategy to mitigate excessive neuroinflammation associated with moderate severity TBI to, thereby, improve behavioral outcome measures and warrants further investigation in neurological disorders involving a neuroinflammatory component. Graphical Abstract
- Published
- 2023
- Full Text
- View/download PDF
3. Electrochemically exfoliated graphite as a highly efficient conductive additive for an anode in lithium‐ion batteries
- Author
-
Dong Seok Kim, Jea Uk Lee, Sung Hyun Kim, and Jin‐Yong Hong
- Subjects
anodes ,conductive additives ,exfoliated graphene ,lithium‐ion batteries ,Production of electric energy or power. Powerplants. Central stations ,TK1001-1841 - Abstract
Abstract In this study, the electrochemical characteristics of an anode fabricated using exfoliated graphite (EG), which is mass‐produced using an electrochemical method, are evaluated to verify the potential of EG as a conductive additive. EG exhibits high electrical conductivity because of the sp2 bonding on the two‐dimensional plane; this conductivity provides a stable electrical pathway and promotes electron transfer in the anode. Furthermore, the small number of graphene layers in EG provide excellent mechanical properties (elastic modulus, tensile strength), which suppresses the volume expansion of the anode during lithiation; therefore, EG‐based anode exhibits high capacity retention and charge/discharge cycle stability. The EG with a large specific surface area improves energy density by decreasing the amount of the additive by more than 70% compared to conventional conductive additives and by simultaneously increasing the amount of the active material. The capacity of the electrode with 3.0 wt% EG reaches 376 mAh/g even after 200 cycles at 0.2 C and 99% of its initial reversible capacity. The rate performance of the electrode with 3.0 wt% EG was about 370 mAh/g at 5.0 C. These results confirm that EG can be used as a conductive additive to overcome the limitations of existing commercial conductive agents.
- Published
- 2023
- Full Text
- View/download PDF
4. Influence of oxidation on the electrochemical properties of silicon oxide-based carbon composites for anode materials of lithium-ion batteries
- Author
-
Dong Seok Kim, Sung Hyun Kim, and Jin-Yong Hong
- Subjects
Silicon oxide ,Magnesiothermic reduction ,Carbon layer ,Anode ,Lithium-ion batteries (LIBs) ,Chemistry ,QD1-999 - Abstract
A new type of silicon oxide-based carbon composite (SiOx@C) was developed to solve the prevalent challenges associated with conventional anode materials, such as pronounced volume fluctuations and inadequate electrical conductivity. The control of oxidation of SiOx was optimized to suppress the excessive formation of the solid electrolyte interphase (SEI) layer and eliminate the short circuits caused by volume variation. In addition, a uniform carbon layer could be formed on the surface of silicon oxide via the rotational chemical vapor deposition (r-CVD) method to improve electrical conductivity. The SiOx@C composites prevented the structural collapse caused by the volume variation of silicon with the buffering effect of the SEI layer produced by repeated charging and discharging. The discharge capacity was found to increase as the oxidation decreased. Particularly, the sample subjected to a reduction process at 700 °C for the SiOx-5h@C exhibited capacities ≥870 mAh g − 1 and excellent stability after 100 cycles at the current speed of 0.2 C.
- Published
- 2023
- Full Text
- View/download PDF
5. Analysis of low-level somatic mosaicism reveals stage and tissue-specific mutational features in human development.
- Author
-
Ja Hye Kim, Shinwon Hwang, Hyeonju Son, Dongsun Kim, Il Bin Kim, Myeong-Heui Kim, Nam Suk Sim, Dong Seok Kim, Yoo-Jin Ha, Junehawk Lee, Hoon-Chul Kang, Jeong Ho Lee, and Sangwoo Kim
- Subjects
Genetics ,QH426-470 - Abstract
Most somatic mutations that arise during normal development are present at low levels in single or multiple tissues depending on the developmental stage and affected organs. However, the effect of human developmental stages or mutations of different organs on the features of somatic mutations is still unclear. Here, we performed a systemic and comprehensive analysis of low-level somatic mutations using deep whole-exome sequencing (average read depth ~500×) of 498 multiple organ tissues with matched controls from 190 individuals. Our results showed that early clone-forming mutations shared between multiple organs were lower in number but showed higher allele frequencies than late clone-forming mutations [0.54 vs. 5.83 variants per individual; 6.17% vs. 1.5% variant allele frequency (VAF)] along with less nonsynonymous mutations and lower functional impacts. Additionally, early and late clone-forming mutations had unique mutational signatures that were distinct from mutations that originated from tumors. Compared with early clone-forming mutations that showed a clock-like signature across all organs or tissues studied, late clone-forming mutations showed organ, tissue, and cell-type specificity in the mutation counts, VAFs, and mutational signatures. In particular, analysis of brain somatic mutations showed a bimodal occurrence and temporal-lobe-specific signature. These findings provide new insights into the features of somatic mosaicism that are dependent on developmental stage and brain regions.
- Published
- 2022
- Full Text
- View/download PDF
6. Highly Concentrated, Conductive, Defect-free Graphene Ink for Screen-Printed Sensor Application
- Author
-
Dong Seok Kim, Jae-Min Jeong, Hong Jun Park, Yeong Kyun Kim, Kyoung G. Lee, and Bong Gill Choi
- Subjects
Graphene ink ,Fluid dynamics ,Screen printing ,Ion sensor ,Real-time monitoring ,Technology - Abstract
Highlights Ultrathin and defect-free graphene ink is prepared through a high-throughput fluid dynamics process, resulting in a high exfoliation yield (53.5%) and a high concentration (47.5 mg mL−1). A screen-printed graphene conductor exhibits a high electrical conductivity of 1.49 × 104 S m−1 and good mechanical flexibility. An electrochemical sodium ion sensor based on graphene ink exhibits an excellent potentiometric sensing performance in a mechanically bent state. Real-time monitoring of sodium ion concentration in sweat is demonstrated. Abstract Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices. However, the application of graphene fillers is limited by their restricted mass production and the low concentration of their suspensions. In this study, a highly concentrated and conductive ink based on defect-free graphene was developed by a scalable fluid dynamics process. A high shear exfoliation and mixing process enabled the production of graphene at a high concentration of 47.5 mg mL−1 for graphene ink. The screen-printed graphene conductor exhibits a high electrical conductivity of 1.49 × 104 S m−1 and maintains high conductivity under mechanical bending, compressing, and fatigue tests. Based on the as-prepared graphene ink, a printed electrochemical sodium ion (Na+) sensor that shows high potentiometric sensing performance was fabricated. Further, by integrating a wireless electronic module, a prototype Na+-sensing watch is demonstrated for the real-time monitoring of the sodium ion concentration in human sweat during the indoor exercise of a volunteer. The scalable and efficient procedure for the preparation of graphene ink presented in this work is very promising for the low-cost, reproducible, and large-scale printing of flexible and wearable electronic devices.
- Published
- 2021
- Full Text
- View/download PDF
7. A New Generation of IMiDs as Treatments for Neuroinflammatory and Neurodegenerative Disorders
- Author
-
Katherine O. Kopp, Margaret E. Greer, Elliot J. Glotfelty, Shih-Chang Hsueh, David Tweedie, Dong Seok Kim, Marcella Reale, Neil Vargesson, and Nigel H. Greig
- Subjects
immunomodulatory imide drugs (IMiDs) ,thalidomide ,pomalidomide ,neuroinflammation ,cereblon ,traumatic brain injury ,Microbiology ,QR1-502 - Abstract
The immunomodulatory imide drug (IMiD) class, which includes the founding drug member thalidomide and later generation drugs, lenalidomide and pomalidomide, has dramatically improved the clinical treatment of specific cancers, such as multiple myeloma, and it combines potent anticancer and anti-inflammatory actions. These actions, in large part, are mediated by IMiD binding to the human protein cereblon that forms a critical component of the E3 ubiquitin ligase complex. This complex ubiquitinates and thereby regulates the levels of multiple endogenous proteins. However, IMiD-cereblon binding modifies cereblon’s normal targeted protein degradation towards a new set of neosubstrates that underlies the favorable pharmacological action of classical IMiDs, but also their adverse actions—in particular, their teratogenicity. The ability of classical IMiDs to reduce the synthesis of key proinflammatory cytokines, especially TNF-α levels, makes them potentially valuable to reposition as drugs to mitigate inflammatory-associated conditions and, particularly, neurological disorders driven by an excessive neuroinflammatory element, as occurs in traumatic brain injury, Alzheimer’s and Parkinson’s diseases, and ischemic stroke. The teratogenic and anticancer actions of classical IMiDs are substantial liabilities for effective drugs in these disorders and can theoretically be dialed out of the drug class. We review a select series of novel IMiDs designed to avoid binding with human cereblon and/or evade degradation of downstream neosubstrates considered to underpin the adverse actions of thalidomide-like drugs. These novel non-classical IMiDs hold potential as new medications for erythema nodosum leprosum (ENL), a painful inflammatory skin condition associated with Hansen’s disease for which thalidomide remains widely used, and, in particular, as a new treatment strategy for neurodegenerative disorders in which neuroinflammation is a key component.
- Published
- 2023
- Full Text
- View/download PDF
8. Functionalization of petroleum pitch-based porous carbon foams and their application in radionuclides adsorption/decontamination
- Author
-
Dong Seok Kim, Sung Hyun Kim, and Jin-Yong Hong
- Subjects
Petroleum pitch ,Porous carbon ,Radionuclide ,Adsorption ,Decontamination ,Chemistry ,QD1-999 - Abstract
A porous carbon foam (P-CF) with high porosity and large pore volume is developed to offer an efficient scaffold for radionuclides adsorption/decontamination. The three-dimensional (3D) porous structure can be easily formed by carbonization of petroleum pitch. During the heat treatment process, the volatile components from the petroleum pitch create highly interconnected pores without any templates, blowing and foaming agents. In addition, Prussian Blue (PB) nanoparticles are introduced onto the surface of the P-CF by a simple hydrothermal method. By combining the enhanced binding affinity to radionuclides with the increased porosity, the synthesized PB@P-CF exhibits the enhanced adsorption capacity for the Cesium ion (133Cs). This study provides a feasible way to utilize residual oil for preparing functionalized porous carbon-based adsorbents for the removal of radionuclides from aqueous solutions. The superior adsorption behaviors of the PB@P-CF make them promising candidates for radioactive materials adsorption/decontamination.
- Published
- 2021
- Full Text
- View/download PDF
9. Activity of a Novel Anti-Inflammatory Agent F-3,6′-dithiopomalidomide as a Treatment for Traumatic Brain Injury
- Author
-
Shih Chang Hsueh, Michael T. Scerba, David Tweedie, Daniela Lecca, Dong Seok Kim, Abdul Mannan Baig, Yu Kyung Kim, Inho Hwang, Sun Kim, Warren R. Selman, Barry J. Hoffer, and Nigel H. Greig
- Subjects
pomalidomide ,immunomodulatory imide drugs (IMiDs) ,neuroinflammation ,traumatic brain injury ,cereblon ,Biology (General) ,QH301-705.5 - Abstract
Traumatic brain injury (TBI) is a major risk factor for several neurodegenerative disorders, including Parkinson’s disease (PD) and Alzheimer’s disease (AD). Neuroinflammation is a cause of later secondary cell death following TBI, has the potential to aggravate the initial impact, and provides a therapeutic target, albeit that has failed to translate into clinical trial success. Thalidomide-like compounds have neuroinflammation reduction properties across cellular and animal models of TBI and neurodegenerative disorders. They lower the generation of proinflammatory cytokines, particularly TNF-α which is pivotal in microglial cell activation. Unfortunately, thalidomide-like drugs possess adverse effects in humans before achieving anti-inflammatory drug levels. We developed F-3,6′-dithiopomalidomide (F-3,6′-DP) as a novel thalidomide-like compound to ameliorate inflammation. F-3,6′-DP binds to cereblon but does not efficiently trigger the degradation of the transcription factors (SALL4, Ikaros, and Aiolos) associated with the teratogenic and anti-proliferative responses of thalidomide-like drugs. We utilized a phenotypic drug discovery approach that employed cellular and animal models in the selection and development of F-3,6’-DP. F-3,6′-DP significantly mitigated LPS-induced inflammatory markers in RAW 264.7 cells, and lowered proinflammatory cytokine/chemokine levels in the plasma and brain of rats challenged with systemic LPS. We subsequently examined immunohistochemical, biochemical, and behavioral measures following controlled cortical impact (CCI) in mice, a model of moderate TBI known to induce inflammation. F-3,6′-DP decreased CCI-induced neuroinflammation, neuronal loss, and behavioral deficits when administered after TBI. F-3,6′-DP represents a novel class of thalidomide-like drugs that do not lower classical cereblon-associated transcription factors but retain anti-inflammatory actions and possess efficacy in the treatment of TBI and potentially longer-term neurodegenerative disorders.
- Published
- 2022
- Full Text
- View/download PDF
10. Thermodynamic Evaluation of Equilibrium Oxygen Composition of UO2-Mo Nuclear Fuel Pellet Under High Temperature Steam
- Author
-
Jae Ho Yang, Kun Woo Song, Dong Seok Kim, Dong-Joo Kim, Heung Soo Lee, Ji-Hae Yoon, and Yang-Hyun Koo
- Subjects
accident tolerant fuel ,UO2-Mo pellet ,steam oxidation ,equilibrium composition ,oxygen potential ,General Works - Abstract
Micro-plate or microcell UO2–Mo is considered a promising accident tolerant fuel candidate for water-cooled power reactors. In this work, we evaluated the anticipated oxidation behavior of a UO2–Mo system under high-temperature steam to understand the impact of Mo oxidation on the fuel degradation mechanism in the event of steam ingress through cracks in the cladding. The equilibrium oxygen compositions of UO2 and Mo in various steam atmospheres relevant to reactor operating conditions were predicted using thermodynamic calculations and then compared with previous results. The oxidation behavior of UO2–Mo pellets was discussed through thermodynamic calculations and in terms of kinetic parameters such as oxygen diffusion, fuel temperature profile, and pellet microstructure. Mo oxidation was found to have an insignificant effect on pellet integrity in a cladding leakage scenario under normal reactor operating conditions.
- Published
- 2021
- Full Text
- View/download PDF
11. Pharmacokinetics and efficacy of PT302, a sustained-release Exenatide formulation, in a murine model of mild traumatic brain injury
- Author
-
Miaad Bader, Yazhou Li, Daniela Lecca, Vardit Rubovitch, David Tweedie, Elliot Glotfelty, Lital Rachmany, Hee Kyung Kim, Ho-Il Choi, Barry J. Hoffer, Chaim G. Pick, Nigel H. Greig, and Dong Seok Kim
- Subjects
Mild traumatic brain injury ,PT302 ,Exenatide ,Exendin-4 ,Glucagon-like peptide-1 ,Incretin mimetic ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Traumatic brain injury (TBI) is a neurodegenerative disorder for which no effective pharmacological treatment is available. Glucagon-like peptide 1 (GLP-1) analogues such as Exenatide have previously demonstrated neurotrophic and neuroprotective effects in cellular and animal models of TBI. However, chronic or repeated administration was needed for efficacy. In this study, the pharmacokinetics and efficacy of PT302, a clinically available sustained-release Exenatide formulation (SR-Exenatide) were evaluated in a concussive mild (m)TBI mouse model. A single subcutaneous (s.c.) injection of PT302 (0.6, 0.12, and 0.024 mg/kg) was administered and plasma Exenatide concentrations were time-dependently measured over 3 weeks. An initial rapid regulated release of Exenatide in plasma was followed by a secondary phase of sustained-release in a dose-dependent manner. Short- and longer-term (7 and 30 day) cognitive impairments (visual and spatial deficits) induced by weight drop mTBI were mitigated by a single post-injury treatment with Exenatide delivered by s.c. injection of PT302 in clinically translatable doses. Immunohistochemical evaluation of neuronal cell death and inflammatory markers, likewise, cross-validated the neurotrophic and neuroprotective effects of SR-Exenatide in this mouse mTBI model. Exenatide central nervous system concentrations were 1.5% to 2.0% of concomitant plasma levels under steady-state conditions. These data demonstrate a positive beneficial action of PT302 in mTBI. This convenient single, sustained-release dosing regimen also has application for other neurological disorders, such as Alzheimer's disease, Parkinson's disease, multiple system atrophy and multiple sclerosis where prior preclinical studies, likewise, have demonstrated positive Exenatide actions.
- Published
- 2019
- Full Text
- View/download PDF
12. Repurposing Immunomodulatory Imide Drugs (IMiDs) in Neuropsychiatric and Neurodegenerative Disorders
- Author
-
Yoo Jin Jung, David Tweedie, Michael T. Scerba, Dong Seok Kim, Maria Francesca Palmas, Augusta Pisanu, Anna R. Carta, and Nigel H. Greig
- Subjects
IMiDs® ,neurodegenarative diseases ,neuropsychaitric disorders ,neuroinflammation ,thalidomide ,pomalidomide ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Neuroinflammation represents a common trait in the pathology and progression of the major psychiatric and neurodegenerative disorders. Neuropsychiatric disorders have emerged as a global crisis, affecting 1 in 4 people, while neurological disorders are the second leading cause of death in the elderly population worldwide (WHO, 2001; GBD 2016 Neurology Collaborators, 2019). However, there remains an immense deficit in availability of effective drug treatments for most neurological disorders. In fact, for disorders such as depression, placebos and behavioral therapies have equal effectiveness as antidepressants. For neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease, drugs that can prevent, slow, or cure the disease have yet to be found. Several non-traditional avenues of drug target identification have emerged with ongoing neurological disease research to meet the need for novel and efficacious treatments. Of these novel avenues is that of neuroinflammation, which has been found to be involved in the progression and pathology of many of the leading neurological disorders. Neuroinflammation is characterized by glial inflammatory factors in certain stages of neurological disorders. Although the meta-analyses have provided evidence of genetic/proteomic upregulation of inflammatory factors in certain stages of neurological disorders. Although the mechanisms underpinning the connections between neuroinflammation and neurological disorders are unclear, and meta-analysis results have shown high sensitivity to factors such as disorder severity and sample type, there is significant evidence of neuroinflammation associations across neurological disorders. In this review, we summarize the role of neuroinflammation in psychiatric disorders such as major depressive disorder, generalized anxiety disorder, post-traumatic stress disorder, and bipolar disorder, as well as in neurodegenerative disorders, such as Parkinson’s disease and Alzheimer’s disease, and introduce current research on the potential of immunomodulatory imide drugs (IMiDs) as a new treatment strategy for these disorders.
- Published
- 2021
- Full Text
- View/download PDF
13. 3,6′- and 1,6′-Dithiopomalidomide Mitigate Ischemic Stroke in Rats and Blunt Inflammation
- Author
-
Yan-Rou Tsai, Dong Seok Kim, Shih-Chang Hsueh, Kai-Yun Chen, John Chung-Che Wu, Jia-Yi Wang, Yi-Syue Tsou, Inho Hwang, Yukyung Kim, Dayeon Gil, Eui Jung Jo, Baek-Soo Han, David Tweedie, Daniela Lecca, Michael T. Scerba, Warren R. Selman, Barry J. Hoffer, Nigel H. Greig, and Yung-Hsiao Chiang
- Subjects
ischemic stroke ,3,6′-dithiopomalidomide ,1,6′-dithiopomalidomide ,pomalidomide ,cereblon ,inflammation ,Pharmacy and materia medica ,RS1-441 - Abstract
(1) Background: An important concomitant of stroke is neuroinflammation. Pomalidomide, a clinically available immunomodulatory imide drug (IMiD) used in cancer therapy, lowers TNF-α generation and thus has potent anti-inflammatory actions. Well-tolerated analogs may provide a stroke treatment and allow evaluation of the role of neuroinflammation in the ischemic brain. (2) Methods: Two novel pomalidomide derivatives, 3,6′-dithiopomalidomide (3,6′-DP) and 1,6′-dithiopomalidomide (1,6′-DP), were evaluated alongside pomalidomide in a rat middle cerebral artery occlusion (MCAo) stroke model, and their anti-inflammatory actions were characterized. (3) Results: Post-MCAo administration of all drugs lowered pro-inflammatory TNF-α and IL1-β levels, and reduced stroke-induced postural asymmetry and infarct size. Whereas 3,6′- and 1,6′-DP, like pomalidomide, potently bound to cereblon in cellular studies, 3,6′-DP did not lower Ikaros, Aiolos or SALL4 levels—critical intermediates mediating the anticancer/teratogenic actions of pomalidomide and IMiDs. 3,6′-DP and 1,6′-DP lacked activity in mammalian chromosome aberration, AMES and hERG channel assays –critical FDA regulatory tests. Finally, 3,6′- and 1,6′-DP mitigated inflammation across rat primary dopaminergic neuron and microglia mixed cultures challenged with α-synuclein and mouse LPS-challenged RAW 264.7 cells. (4) Conclusion: Neuroinflammation mediated via TNF-α plays a key role in stroke outcome, and 3,6′-DP and 1,6′-DP may prove valuable as stroke therapies and thus warrant further preclinical development.
- Published
- 2022
- Full Text
- View/download PDF
14. 3,6’-dithiopomalidomide reduces neural loss, inflammation, behavioral deficits in brain injury and microglial activation
- Author
-
Chih-Tung Lin, Daniela Lecca, Ling-Yu Yang, Weiming Luo, Michael T Scerba, David Tweedie, Pen-Sen Huang, Yoo-Jin Jung, Dong Seok Kim, Chih-Hao Yang, Barry J Hoffer, Jia-Yi Wang, and Nigel H Greig
- Subjects
traumatic brain injury ,neuroinflammation ,neurodegeneration ,pomalidomide ,3,6'-dithiopomalidomide ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Traumatic brain injury (TBI) causes mortality and disability worldwide. It can initiate acute cell death followed by secondary injury induced by microglial activation, oxidative stress, inflammation and autophagy in brain tissue, resulting in cognitive and behavioral deficits. We evaluated a new pomalidomide (Pom) analog, 3,6’-dithioPom (DP), and Pom as immunomodulatory agents to mitigate TBI-induced cell death, neuroinflammation, astrogliosis and behavioral impairments in rats challenged with controlled cortical impact TBI. Both agents significantly reduced the injury contusion volume and degenerating neuron number evaluated histochemically and by MRI at 24 hr and 7 days, with a therapeutic window of 5 hr post-injury. TBI-induced upregulated markers of microglial activation, astrogliosis and the expression of pro-inflammatory cytokines, iNOS, COX-2, and autophagy-associated proteins were suppressed, leading to an amelioration of behavioral deficits with DP providing greater efficacy. Complementary animal and cellular studies demonstrated DP and Pom mediated reductions in markers of neuroinflammation and α-synuclein-induced toxicity.
- Published
- 2020
- Full Text
- View/download PDF
15. Development status of microcell UO2 pellet for accident-tolerant fuel
- Author
-
Dong-Joo Kim, Keon Sik Kim, Dong Seok Kim, Jang Soo Oh, Jong Hun Kim, Jae Ho Yang, and Yang-Hyun Koo
- Subjects
Nuclear engineering. Atomic power ,TK9001-9401 - Abstract
A microcell UO2 pellet, as an accident-tolerant fuel pellet, is being developed to enhance the accident tolerance of nuclear fuels under accident conditions as well as the fuel performance under normal operation conditions.Improved capture-ability for highly radioactive and corrosive fission product (Cs and I) is the distinct feature of a ceramic microcell UO2 pellet, and the enhanced pellet thermal conductivity is that of a metallic microcell UO2 pellet. The fuel temperature can be effectively decreased by enhanced thermal conductivity.In this study, the material concepts of metallic and ceramic microcell UO2 pellets were designed, and the fabrication process of microcell UO2 pellets embodying the designed concept was developed. We successfully implemented the microcell UO2 pellets and produced microcell UO2 pellets.In addition, an assessment of the out-of-pile properties of a microcell UO2 pellet was performed, and the in-reactor performance and behavior of the developed microcell pellets were evaluated through a Halden irradiation test. According to the expectations, the excellent performance of the microcell UO2 pellets was confirmed by the online measurement data of the Halden irradiation test. Keywords: Accident-Tolerant Fuel, Fission Product Retention, Halden Irradiation Test, Microcell UO2 Pellet, Thermal Conductivity
- Published
- 2018
- Full Text
- View/download PDF
16. Effects of 8 Weeks of Inspiratory Muscle Training on Pulmonary Function and Maximum Inspiratory Pressure and Skill-related Physical Fitness in Women
- Author
-
Dong Seok Kim and Byeong Hwan Jeon
- Subjects
Inspiratory muscle training ,PImax ,Pulmonary function ,Skill-related physical fitness ,Sports ,GV557-1198.995 ,Physiology ,QP1-981 - Abstract
PURPOSE The purpose of this study was verifying effects of 8 weeks of inspiratory muscle training on pulmonary function and maximum inspiratory pressure and skill-related physical fitness in women. METHODS Participants were divided into two group; an inspiratory muscle training group (IMT, n = 8 ) and a placebo control group (CON, n = 8 ). The IMT group carried out inspiratory muscle training six days per week, 30 times a day. ‘Paired t-test’ for comparison between before and after result in each group. And ‘independent sample t-test’ for comparison value of before and after result in each groups (SPSS 23.0 Ver.). RESULTS As a results regarding maximum inspiratory pressure, IMT was shown to have a significant effect on peak S-index and peak inspiratory flow(PIF)(p< .001). IMT induced a significant improvement in Sit-up and Shuttle run(p< .01). CONCLUSIONS The results of the present study indicate that IMT is able to improve maximum inspiratory pressure and skill-related physical fitness in women. future studies should attempt to implement variations in methodology including, using male subjects, exercising for a different period of time and evaluating other fitness outcomes.
- Published
- 2018
- Full Text
- View/download PDF
17. 3,6′-Dithiopomalidomide Ameliorates Hippocampal Neurodegeneration, Microgliosis and Astrogliosis and Improves Cognitive Behaviors in Rats with a Moderate Traumatic Brain Injury
- Author
-
Pen-Sen Huang, Ping-Yen Tsai, Ling-Yu Yang, Daniela Lecca, Weiming Luo, Dong Seok Kim, Barry J. Hoffer, Yung-Hsiao Chiang, Nigel H. Greig, and Jia-Yi Wang
- Subjects
3,6′-dithiopomalidomide ,pomalidomide ,traumatic brain injury ,neurodegeneration ,cognitive deficits ,neuroinflammation ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Traumatic brain injury (TBI) is a leading cause of disability and mortality worldwide. It can instigate immediate cell death, followed by a time-dependent secondary injury that results from disproportionate microglial and astrocyte activation, excessive inflammation and oxidative stress in brain tissue, culminating in both short- and long-term cognitive dysfunction and behavioral deficits. Within the brain, the hippocampus is particularly vulnerable to a TBI. We studied a new pomalidomide (Pom) analog, namely, 3,6′-dithioPom (DP), and Pom as immunomodulatory imide drugs (IMiD) for mitigating TBI-induced hippocampal neurodegeneration, microgliosis, astrogliosis and behavioral impairments in a controlled cortical impact (CCI) model of TBI in rats. Both agents were administered as a single intravenous dose (0.5 mg/kg) at 5 h post injury so that the efficacies could be compared. Pom and DP significantly reduced the contusion volume evaluated at 24 h and 7 days post injury. Both agents ameliorated short-term memory deficits and anxiety behavior at 7 days after a TBI. The number of degenerating neurons in the CA1 and dentate gyrus (DG) regions of the hippocampus after a TBI was reduced by Pom and DP. DP, but not Pom, significantly attenuated the TBI-induced microgliosis and DP was more efficacious than Pom at attenuating the TBI-induced astrogliosis in CA1 and DG at 7D after a TBI. In summary, a single intravenous injection of Pom or DP, given 5 h post TBI, significantly reduced hippocampal neurodegeneration and prevented cognitive deficits with a concomitant attenuation of the neuroinflammation in the hippocampus.
- Published
- 2021
- Full Text
- View/download PDF
18. Effects of Proton Irradiation on the Current Characteristics of SiN-Passivated AlGaN/GaN MIS-HEMTs Using a TMAH-Based Surface Pre-Treatment
- Author
-
Young Jun Yoon, Jae Sang Lee, Jae Kwon Suk, In Man Kang, Jung Hee Lee, Eun Je Lee, and Dong Seok Kim
- Subjects
Gallium Nitride (GaN) ,proton irradiation ,surface pre-treatment ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
This study investigated the combined effects of proton irradiation and surface pre-treatment on the current characteristics of Gallium Nitride (GaN)-based metal-insulator-semiconductor high-electron-mobility-transistors (MIS-HEMTs) to evaluate the radiation hardness involved with the Silicon Nitride (SiN) passivation/GaN cap interface. The impact of proton irradiation on the static and dynamic current characteristics of devices with and without pre-treatment were analyzed with 5 MeV proton irradiation. In terms of transfer characteristics before and after the proton irradiation, the drain current of the devices without and with pre-treatment were reduced by an increase in sheet and contact resistances after the proton irradiation. In contrast with the static current characteristics, the gate-lag characteristics of the device with pre-treatment were significantly degenerated. In the device with pre-treatment, the hydrogen passivation for surface states of the GaN cap was formed by the pre-treatment and SiN deposition processes. Since the hydrogen passivation was removed by the proton irradiation, the newly created vacancies resulted in the degeneration of gate-lag characteristics. After nine months in an ambient atmosphere, the gate-lag characteristics of the device with pre-treatment were recovered because of the hydrogen recombination. These results demonstrated that the radiation hardness of MIS-HEMTs was affected by the SiN/GaN interface quality.
- Published
- 2021
- Full Text
- View/download PDF
19. Exendin-4 attenuates blast traumatic brain injury induced cognitive impairments, losses of synaptophysin and in vitro TBI-induced hippocampal cellular degeneration
- Author
-
Lital Rachmany, David Tweedie, Vardit Rubovitch, Yazhou Li, Harold W. Holloway, Dong Seok Kim, Whitney A. Ratliff, Jessica N. Saykally, Bruce A. Citron, Barry J. Hoffer, Nigel H. Greig, and Chaim G. Pick
- Subjects
Medicine ,Science - Abstract
Abstract Mild blast traumatic brain injury (B-TBI) induced lasting cognitive impairments in novel object recognition and less severe deficits in Y-maze behaviors. B-TBI significantly reduced the levels of synaptophysin (SYP) protein staining in cortical (CTX) and hippocampal (HIPP) tissues. Treatment with exendin-4 (Ex-4) delivered by subcutaneous micro-osmotic pumps 48 hours prior to or 2 hours immediately after B-TBI prevented the induction of both cognitive deficits and B-TBI induced changes in SYP staining. The effects of a series of biaxial stretch injuries (BSI) on a neuronal derived cell line, HT22 cells, were assessed in an in vitro model of TBI. Biaxial stretch damage induced shrunken neurites and cell death. Treatment of HT22 cultures with Ex-4 (25 to 100 nM), prior to injury, attenuated the cytotoxic effects of BSI and preserved neurite length similar to sham treated cells. These data imply that treatment with Ex-4 may represent a viable option for the management of secondary events triggered by blast-induced, mild traumatic brain injury that is commonly observed in militarized zones.
- Published
- 2017
- Full Text
- View/download PDF
20. Design and Analysis of Gallium Nitride-Based p-i-n Diode Structure for Betavoltaic Cell with Enhanced Output Power Density
- Author
-
Young Jun Yoon, Jae Sang Lee, In Man Kang, Jung Hee Lee, and Dong Seok Kim
- Subjects
betavoltaic cell ,Gallium Nitride (GaN) ,high-output power ,TCAD simulation ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
In this work, Gallium Nitride (GaN)-based p-i-n diodes were designed using a computer aided design (TCAD) simulator for realizing a betavoltaic (BV) cell with a high output power density (Pout). The short-circuit current density (JSC) and open-circuit voltage (VOC) of the 17 keV electron-beam (e-beam)-irradiated diode were evaluated with the variations of design parameters, such as the height and doping concentration of the intrinsic GaN region (Hi-GaN and Di-GaN), which influenced the depletion width in the i-GaN region. A high Hi-GaN and a low Di-GaN improved the Pout because of the enhancement of absorption and conversion efficiency. The device with the Hi-GaN of 700 nm and Di-GaN of 1 × 1016 cm−3 exhibited the highest Pout. In addition, the effects of native defects in the GaN material on the performances were investigated. While the reverse current characteristics were mainly unaffected by donor-like trap states like N vacancies, the Ga vacancies-induced acceptor-like traps significantly decreased the JSC and VOC due to an increase in recombination rate. As a result, the device with a high acceptor-like trap density dramatically degenerated the Pout. Therefore, growth of the high quality i-GaN with low acceptor-like traps is important for an enhanced Pout in BV cell.
- Published
- 2020
- Full Text
- View/download PDF
21. A New Treatment Strategy for Parkinson's Disease through the Gut–Brain Axis
- Author
-
Dong Seok Kim, Ho-Il Choi, Yun Wang, Yu Luo, Barry J. Hoffer, and Nigel H. Greig
- Subjects
Medicine - Abstract
Molecular communications in the gut–brain axis, between the central nervous system and the gastrointestinal tract, are critical for maintaining healthy brain function, particularly in aging. Epidemiological analyses indicate type 2 diabetes mellitus (T2DM) is a risk factor for neurodegenerative disorders including Alzheimer's disease (AD) and Parkinson's diseases (PD) for which aging shows a major correlative association. Common pathophysiological features exist between T2DM, AD, and PD, including oxidative stress, inflammation, insulin resistance, abnormal protein processing, and cognitive decline, and suggest that effective drugs for T2DM that positively impact the gut–brain axis could provide an effective treatment option for neurodegenerative diseases. Glucagon-like peptide-1 (GLP-1)-based antidiabetic drugs have drawn particular attention as an effectual new strategy to not only regulate blood glucose but also decrease body weight by reducing appetite, which implies that GLP-1 could affect the gut–brain axis in normal and pathological conditions. The neurotrophic and neuroprotective effects of GLP-1 receptor (R) stimulation have been characterized in numerous in vitro and in vivo preclinical studies using GLP-1R agonists and dipeptidyl peptidase-4 inhibitors. Recently, the first open label clinical study of exenatide, a long-acting GLP-1 agonist, in the treatment of PD showed long-lasting improvements in motor and cognitive function. Several double-blind clinical trials of GLP-1R agonists including exenatide in PD and other neurodegenerative diseases are already underway or are about to be initiated. Herein, we review the physiological role of the GLP-1R pathway in the gut–brain axis and the therapeutic strategy of GLP-1R stimulation for the treatment of neurodegenerative diseases focused on PD, for which age is the major risk factor.
- Published
- 2017
- Full Text
- View/download PDF
22. A case of hippocampal sclerosis diagnosed as cortical dysplasia due to preoperative brain MRI finding
- Author
-
Jun Seok Lee, Kyo Ryung Kim, Jeong Tae Kim, Min Jung Choi, Young Mock Lee, Heung Dong Kim, Joon Soo Lee, Dong Seok Kim, and Tae Seong Kim
- Subjects
Pediatrics ,RJ1-570 - Abstract
Hippocampal sclerosis (HS) is one of the most common features of intractable temporal lobe epilepsy. Generally it can be identified through brain magnetic resonance imaging (MRI) with high degree of sensitivity and specificity. Typical brain MRI findings of HS are hippocampal atrophy with hyperintense signal confined to the lesion. On the other hand cortical dysplasia exhibits blurring of the gray-white matter junction and abnormal white matter signal intensity. We present a case where preoperative brain MRI strongly suggested the presence of diffuse cortical dysplasia in the left temporal lobe but postoperative pathology revealed the temporal lesion to be unremarkable except for hippocampal sclerosis.
- Published
- 2010
- Full Text
- View/download PDF
23. Development of Lateral Flow Assay Based on Size-Controlled Gold Nanoparticles for Detection of Hepatitis B Surface Antigen
- Author
-
Dong Seok Kim, Yong Tae Kim, Seok Bok Hong, Jinwoon Kim, Nam Su Heo, Moon-Keun Lee, Seok Jae Lee, Byeong Il Kim, In Soo Kim, Yun Suk Huh, and Bong Gill Choi
- Subjects
gold ,nanoparticle ,hepatitis B surface antigen ,lateral flow assay ,conjugation ,Chemical technology ,TP1-1185 - Abstract
In this study, we developed lateral flow assay (LFA) biosensors for the detection of hepatitis B surface antigens using well-controlled gold nanoparticles (AuNPs). To enhance colorimetric signals, a seeded growth method was used for the preparation of size-controlled AuNPs with a narrow size distribution. Different sizes of AuNPs in the range of 342–137.8 nm were conjugated with antibodies and then optimized for the efficient detection of LFA biosensors. The conjugation stability was investigated by UV-vis spectroscopy of AuNP dispersion at various pH values and concentrations of antibody. Based on optimized conjugation conditions, the use of 42.7 ± 0.8 nm AuNPs exhibited superior performance for the detection of LFAs relative to other sizes of AuNPs.
- Published
- 2016
- Full Text
- View/download PDF
24. Federated regressive learning: Adaptive weight updates through statistical information of clients.
- Author
-
Dong Seok Kim, Shabir Ahmad, and Taeg Keun Whangbo
- Published
- 2024
- Full Text
- View/download PDF
25. Analysis of Impact of Renewable Power Generation Facilities using Large-capacity Data of GPS Time Synchronization PMU
- Author
-
Dong-Seok Kim and Chul-Won Park
- Subjects
Electrical and Electronic Engineering - Published
- 2023
26. Development Status of Control Rod Neutron Absorber Materials for Light Water Reactors with Extended Control Rod Lifetime and Enhanced Safety
- Author
-
Dong-Joo Kim, Jae Ho Yang, Dong Seok Kim, Ji-Hae Yoon, Heung Soo Lee, Kwang-Young Lim, and Jae-Yong Kim
- Subjects
Applied Mathematics ,General Mathematics - Abstract
The control rod neutron absorbers for light water reactors with extended control rod lifetime and enhanced safety are being developed. It is an innovative material concept that can extend the lifetime by reducing irradiation-induced swelling compared to the existing control rod neutron absorber materials by utilizing the oxide-based materials. Furthermore, it can enhance the safety by improving various characteristics such as oxidation, eutectic reaction, volatilization behaviors of neutron absorber material. First, the oxide-based composition composed of a combination of neutron absorbers and structure stabilizers has been designed as material candidates for neutron absorber materials for control rods. The preliminary manufacturability test of the designed neutron absorber material candidates, and it has been confirmed a possibility that the designed material candidates can be fabricated using the conventional ceramic manufacturing process. In addition, the neutronic calculation/analysis and various out-of-pile tests (neutron absorber phase stability, oxidation and corrosion resistance, interaction and eutectic reaction between neutron absorber material and control rod tube material, melting behavior, etc.) are in progress. It has been also preparing the in-reactor swelling test of the selected material candidates at the HANARO research reactor in KAERI.
- Published
- 2022
27. Treatment outcomes and prognostic factors of motorized 0.5-mm micropunch grafting with a skin-seeding technique for 83 cases of vitiligo in children
- Author
-
Jin Cheol, Kim, Dong Chan, Kim, Hee Young, Kang, and Dong Seok, Kim
- Subjects
Dermatology - Published
- 2023
28. Ultra-Low Level Somatic Mutations and Structural Variations in Focal Cortical Dysplasia Type II
- Author
-
Ja Hye Kim, Ji‐Hyung Park, Junehawk Lee, Jung Woo Park, Hyun Jung Kim, Won Seok Chang, Dong‐Seok Kim, Young Seok Ju, Eleonora Aronica, Jeong Ho Lee, Pathology, AII - Inflammatory diseases, and ANS - Cellular & Molecular Mechanisms
- Subjects
Neurology ,Neurology (clinical) - Abstract
Objective: Brain somatic mutations in mTOR pathway genes are a major genetic etiology of focal cortical dysplasia type II (FCDII). Despite a greater ability to detect low-level somatic mutations in the brain by deep sequencing and analytics, about 40% of cases remain genetically unexplained. Methods: We included 2 independent cohorts consisting of 21 patients with mutation-negative FCDII without apparent mutations on conventional deep sequencing of bulk brain. To find ultra-low level somatic variants or structural variants, we isolated cells exhibiting phosphorylation of the S6 ribosomal protein (p-S6) in frozen brain tissues using fluorescence-activated cell sorting (FACS). We then performed deep whole-genome sequencing (WGS; >90×) in p-S6 + cells in a cohort of 11 patients with mutation-negative. Then, we simplified the method to whole-genome amplification and target gene sequencing of p-S6 + cells in independent cohort of 10 patients with mutation-negative followed by low-read depth WGS (10×). Results: We found that 28.6% (6 of 21) of mutation-negative FCDII carries ultra-low level somatic mutations (less than 0.2% of variant allele frequency [VAF]) in mTOR pathway genes. Our method showed ~34 times increase of the average mutational burden in FACS mediated enrichment of p-S6 + cells (average VAF = 5.84%) than in bulky brain tissues (average VAF = 0.17%). We found that 19% (4 of 21) carried germline structural variations in GATOR1 complex undetectable in whole exome or targeted gene sequencing. Conclusions: Our method facilitates the detection of ultra-low level somatic mutations, in specifically p-S6 + cells, and germline structural variations and increases the genetic diagnostic rate up to ~80% for the entire FCDII cohort. ANN NEUROL 2023;93:1082–1093.
- Published
- 2023
29. Epilepsy with SLC35A2 Brain Somatic Mutations in Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia in Epilepsy (MOGHE)
- Author
-
Hee-Jeong Kang, Dong-Seok Kim, Se Hoon Kim, Jeong Ho Lee, Ara Ko, Se Hee Kim, Joon Soo Lee, Heung Dong Kim, and Hoon-Chul Kang
- Subjects
Neurology ,Pediatrics, Perinatology and Child Health ,Neurology (clinical) - Abstract
Purpose: This study presents the characteristics of patients with mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) with SLC35A2 somatic variants in the brain who underwent epilepsy surgery and showed clinical improvement in seizures. Methods: We collected 10 patients with SLC35A2 somatic mutations in the brain who underwent surgery to treat drug-resistant epilepsy at Severance Children’s Hospital from 2014 to 2019 and retrospectively reviewed their genetic profiles, neuropathologic results, clinical features, pre-operative evaluations, and post-operative outcomes.Results: Six of the 10 patients with SCL35A2 somatic mutations in the brain had Lennox Gastaut syndrome (LGS) evolving from infantile spasms (IS), three had LGS, and one had IS. The median value of variant allele frequencies (VAFs) was 5.7% (1.7% to 5.8%; range, 1.4% to 22.9%). Nonsense mutations were the most common (50%), followed by missense mutations (40%) and a splicing site mutation (10%). Eight patients (80%) had good post-operative outcomes, with freedom from disabling seizures in five (Engel class I) and rare disabling seizures in three (Engel class II). Four of the eight patients who could be assessed for social quotient (SQ) after surgery showed SQ improvements by 12.2±6.4. Although all patients were finally diagnosed with MOGHE, seven (70%) were initially diagnosed with gliosis, two with mild malformation of cortical development, and one with no abnormality.Conclusion: All patients with SCL35A2 brain somatic mutations, even with low VAFs, had refractory epilepsy such as LGS or IS, and were finally diagnosed with MOGHE. This report is the first in Korea to our knowledge.
- Published
- 2022
30. Lower Leg Abscess in Klebsiella pneumoniae Invasive Syndrome Caused by Hypervirulent Klebsiella pneumoniae: A Case Report
- Author
-
Dong Seok Kim and Dae-Yoo Kim
- Published
- 2022
31. Isomers of the Tomato Glycoalkaloids α-Tomatine and Dehydrotomatine: Relationship to Health Benefits
- Author
-
Nobuyuki Kozukue, Dong-Seok Kim, Suk-Hyun Choi, Masashi Mizuno, and Mendel Friedman
- Subjects
tomatoes ,tomato glycoalkaloids ,α-tomatine ,dehydrotomatine ,α-tomatine isomer ,dehydrotomatine isomer ,LC/MS analysis ,LC-(Q) TOF/MS analysis ,health benefits ,research needs ,Chemistry (miscellaneous) ,Organic Chemistry ,Drug Discovery ,Molecular Medicine ,Pharmaceutical Science ,Physical and Theoretical Chemistry ,Analytical Chemistry - Abstract
High-performance liquid chromatography (HPLC) analysis of three commercial tomatine samples and another isolated from green tomatoes revealed the presence of two small peaks in addition to those associated with the glycoalkaloids dehydrotomatine and α-tomatine. The present study investigated the possible structures of the compounds associated with the two small peaks using HPLC–mass spectrophotometric (MS) methods. Although the two peaks elute much earlier on chromatographic columns than the elution times of the known tomato glycoalkaloids dehydrotomatine and α-tomatine, isolation of the two compounds by preparative chromatography and subsequent analysis by MS shows the two compounds have identical molecular weights, tetrasaccharide side chains, and MS and MS/MS fragmentation patterns to dehydrotomatine and α-tomatine. We suggest the two isolated compounds are isomeric forms of dehydrotomatine and α-tomatine. The analytical data indicate that widely used commercial tomatine preparations and those extracted from green tomatoes and tomato leaves consist of a mixture of α-tomatine, dehydrotomatine, an α-tomatine isomer, and a dehydrotomatine isomer in an approximate ratio of 81:15:4:1, respectively. The significance of the reported health benefits of tomatine and tomatidine is mentioned.
- Published
- 2023
- Full Text
- View/download PDF
32. Mechanisms of the Device Property Alteration Generated by the Proton Irradiation in GaN-Based MIS-HEMTs Using Extremely Thin Gate Insulator
- Author
-
Sung-Jae Chang, Dong-Seok Kim, Tae-Woo Kim, Youngho Bae, Hyun-Wook Jung, Il-Gyu Choi, Youn-Sub Noh, Sang-Heung Lee, Seong-Il Kim, Ho-Kyun Ahn, Dong-Min Kang, and Jong-Won Lim
- Subjects
MIS-HEMT ,HfO2 ,General Chemical Engineering ,total ionizing dose effects ,Si3N4 ,radiation effects ,General Materials Science ,gate insulator ,displacement damages ,GaN ,proton - Abstract
Recently, we reported that device performance degradation mechanisms, which are generated by the γ-ray irradiation in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs), use extremely thin gate insulators. When the γ-ray was radiated, the total ionizing dose (TID) effects were generated and the device performance deteriorated. In this work, we investigated the device property alteration and its mechanisms, which were caused by the proton irradiation in GaN-based MIS-HEMTs for the 5 nm-thick Si3N4 and HfO2 gate insulator. The device property, such as threshold voltage, drain current, and transconductance varied by the proton irradiation. When the 5 nm-thick HfO2 layer was employed for the gate insulator, the threshold voltage shift was larger than that of the 5 nm-thick Si3N4 gate insulator, despite the HfO2 gate insulator exhibiting better radiation resistance compared to the Si3N4 gate insulator. On the other hand, the drain current and transconductance degradation were less for the 5 nm-thick HfO2 gate insulator. Unlike the γ-ray irradiation, our systematic research included pulse-mode stress measurements and carrier mobility extraction and revealed that the TID and displacement damage (DD) effects were simultaneously generated by the proton irradiation in GaN-based MIS-HEMTs. The degree of the device property alteration was determined by the competition or superposition of the TID and DD effects for the threshold voltage shift and drain current and transconductance deterioration, respectively. The device property alteration was diminished due to the reduction of the linear energy transfer with increasing irradiated proton energy. We also studied the frequency performance degradation that corresponded to the irradiated proton energy in GaN-based MIS-HEMTs using an extremely thin gate insulator.
- Published
- 2023
- Full Text
- View/download PDF
33. Geometry transition method to improve ray-tracing precision.
- Author
-
Dong-Seok Kim, Jae-Ho Nah, and Woo-Chan Park
- Published
- 2016
- Full Text
- View/download PDF
34. Changes and Chalenges in Special Admissions for Rural Students
- Author
-
Dong Seok Kim and Woo-jeong Shim
- Published
- 2022
35. Role of chronic neuroinflammation in neuroplasticity and cognitive function: A hypothesis
- Author
-
Daniela Lecca, Yoo Jin Jung, Michael T. Scerba, Inho Hwang, Yu Kyung Kim, Sun Kim, Sydney Modrow, David Tweedie, Shih‐Chang Hsueh, Dong Liu, Weiming Luo, Elliot Glotfelty, Yazhou Li, Jia‐Yi Wang, Yu Luo, Barry J. Hoffer, Dong Seok Kim, Ross A. McDevitt, and Nigel H. Greig
- Subjects
Amyloid beta-Peptides ,Neuronal Plasticity ,Tumor Necrosis Factor-alpha ,Epidemiology ,Health Policy ,Mice, Transgenic ,Mice, Inbred C57BL ,Mice ,Disease Models, Animal ,Psychiatry and Mental health ,Cellular and Molecular Neuroscience ,Cognition ,Developmental Neuroscience ,Alzheimer Disease ,Neuroinflammatory Diseases ,Animals ,Cognitive Dysfunction ,Microglia ,Neurology (clinical) ,Geriatrics and Gerontology - Abstract
Evaluating the efficacy of 3,6'-dithioPomalidomide in 5xFAD Alzheimer's disease (AD) mice to test the hypothesis that neuroinflammation is directly involved in the development of synaptic/neuronal loss and cognitive decline.Amyloid-β (Aβ) or tau-focused clinical trials have proved unsuccessful in mitigating AD-associated cognitive impairment. Identification of new drug targets is needed. Neuroinflammation is a therapeutic target in neurodegenerative disorders, and TNF-α a pivotal neuroinflammatory driver.AD-associated chronic neuroinflammation directly drives progressive synaptic/neuronal loss and cognitive decline. Pharmacologically mitigating microglial/astrocyte activation without altering Aβ generation will define the role of neuroinflammation in AD progression.Difficulty of TNF-α-lowering compounds reaching brain, and identification of a therapeutic-time window to preserve the beneficial role of neuroinflammatory processes.Microglia/astroglia are heavily implicated in maintenance of synaptic plasticity/function in healthy brain and are disrupted by Aβ. Mitigation of chronic gliosis can restore synaptic homeostasis/cognitive function.
- Published
- 2022
36. Investigation of Proton Irradiation-Enhanced Device Performances in AlGaN/GaN HEMTs
- Author
-
Chu-Young Cho, Eun Jin Kim, Jeong-Gil Kim, Jung-Hee Lee, and Dong-Seok Kim
- Subjects
Materials science ,Proton ,business.industry ,Transconductance ,proton irradiation ,hydrogen passivation ,Fluence ,Buffer (optical fiber) ,Electronic, Optical and Magnetic Materials ,TK1-9971 ,AlGaN/GaN ,Dispersion (optics) ,Optoelectronics ,Irradiation ,Electrical engineering. Electronics. Nuclear engineering ,Electrical and Electronic Engineering ,business ,Radiation hardening ,Layer (electronics) ,HEMT ,Biotechnology - Abstract
We have studied the effects of proton irradiation on the AlGaN/GaN HEMTs with AlN buffer layer as well as conventional GaN buffer layer. It was found that a short time proton irradiation (~ 50 sec) can promote beneficial effects on device performances, which results in great reduction in the off-state leakage current and the gate leakage current without degrading the output current and transconductance. The pulsed I-V measurement demonstrated that both devices exhibit greatly improved current dispersion characteristics and, particularly, the device with AlN buffer layer shows stronger radiation hardness than that of the device with GaN buffer layer. These interesting results are believed to be due to the hydrogen passivation with thermal annealing effect during the proton irradiation. It is expected that the proper irradiation condition such as fluence, energy, and time is crucial to improve the device performances, rather than to deteriorate the performances.
- Published
- 2022
37. Outcomes of intracranial germinoma—A retrospective multinational Asian study on effect of clinical presentation and differential treatment strategies
- Author
-
Kyung-Nam Koh, Ru Xin Wong, Dong-Eun Lee, Jung Woo Han, Hwa Kyung Byun, Hong In Yoon, Dong-Seok Kim, Chuhl Joo Lyu, Hyoung Jin Kang, Kyung Taek Hong, Joo Ho Lee, Il Han Kim, Ji Hoon Phi, Seung-Ki Kim, Tai-Tong Wong, Hsin-Lun Lee, I-Chun Lai, Yu-Mei Kang, Young-Shin Ra, Seung Do Ahn, Ho Joon Im, Wen Shen Looi, Sharon Yin Yee Low, Enrica Ee Kar Tan, Hyun Jin Park, Sang Hoon Shin, Hiroshi Fuji, Chang-Ok Suh, Yi-Wei Chen, and Joo-Young Kim
- Subjects
Salvage Therapy ,Cancer Research ,Oncology ,Brain Neoplasms ,Clinical Investigations ,Humans ,Germinoma ,Neurology (clinical) ,Pineal Gland ,Retrospective Studies - Abstract
Background This multinational study was conducted to report clinical presentations and treatment strategies in patients with intracranial germinomas across selected Asian centers, including failure patterns, risk factors, and outcomes. Methods A retrospective data collection and analysis of these patients, treated between 1995 and 2015 from eight healthcare institutions across four countries was undertaken. Results From the results, 418 patients were analyzed, with a median follow-up of 8.9 years; 79.9% of the patients were M0, and 87.6% had β-human chorionic gonadotropin values Conclusions Survival outcomes of patients with germinoma were excellent. Thus, the focus of treatment for intracranial germinoma should be on survivorship. Further studies are warranted to find the optimal intensity and volume of radiation, including the role of chemotherapy in the survival of patients with intracranial germinomas, considering age, primary tumor location, and extent of disease.
- Published
- 2021
38. Van der Waals Heterostructure of Hexagonal Boron Nitride with an AlGaN/GaN Epitaxial Wafer for High-Performance Radio Frequency Applications
- Author
-
Dong-Seok Kim, Jiye Kim, Jae Dong Lee, Hokyun Ahn, Hyun-Wook Jung, Si-Young Choi, Odongo Francis Ngome Okello, Jong Kyu Kim, Sung-Jae Chang, Youngjae Kim, Seokho Moon, Jaewon Kim, and Jong-Won Lim
- Subjects
Materials science ,Passivation ,business.industry ,Transistor ,Heterojunction ,High-electron-mobility transistor ,Chemical vapor deposition ,law.invention ,symbols.namesake ,Semiconductor ,law ,symbols ,Optoelectronics ,General Materials Science ,Wafer ,van der Waals force ,business - Abstract
While two-dimensional (2D) hexagonal boron nitride (h-BN) is emerging as an atomically thin and dangling bond-free insulating layer for next-generation electronics and optoelectronics, its practical implementation into miniaturized integrated circuits has been significantly limited due to difficulties in large-scale growth directly on epitaxial semiconductor wafers. Herein, the realization of a wafer-scale h-BN van der Waals heterostructure with a 2 in. AlGaN/GaN high-electron mobility transistor (HEMT) wafer using metal-organic chemical vapor deposition is presented. The combination of state-of-the-art microscopic and spectroscopic analyses and theoretical calculations reveals that the heterointerface between ∼2.5 nm-thick h-BN and AlGaN layers is atomically sharp and exhibits a very weak van der Waals interaction without formation of a ternary or quaternary alloy that can induce undesired degradation of device performance. The fabricated AlGaN/GaN HEMT with h-BN shows very promising performance including a cutoff frequency (fT) and maximum oscillation frequency (fMAX) as high as 28 and 88 GHz, respectively, enabled by an effective passivation of surface defects on the HEMT wafer to deliver accurate information with minimized power loss. These findings pave the way for practical implementation of 2D materials integrated with conventional microelectronic devices and the realization of future all-2D electronics.
- Published
- 2021
39. Effect of Fermented Sarco Oyster (Crassostrea gigas) Extract on Muscle Strength Enhancement in Postmenopausal Females: A Randomized, Double-Blind, Placebo-Controlled Trial
- Author
-
Kyoung-Min Rheu, Bae-Jin Lee, Woo-Hyeon Son, Dong-Seok Kim, Hyun-Tae Park, Min-Seong Ha, Byong-Hak Gong, and Byeong-Hwan Jeon
- Subjects
Health, Toxicology and Mutagenesis ,fermented oyster ,γ-aminobutyric acid ,insulin growth factor-1 ,muscle strength ,postmenopausal female ,dietary supplements ,sarcopenia ,Public Health, Environmental and Occupational Health - Abstract
A randomized controlled trial (RCT) was conducted to evaluate the effect of fermented sarco oysters (FSO) on muscle strength in postmenopausal females with low muscle mass. Fifty-two female participants were randomly divided into the experiment group (EG) or control group (CG). For 12 weeks, the EG was subjected to 1000 mg of FSO extract daily while the CG consumed the placebo extract. The muscle extension and flexion at an angular velocity of 60°/s and with respect to grip strength, body composition, and muscle growth-related blood factors were measured at the baseline and after the trial. The difference in the quadriceps muscle extension at an angular velocity of 60°/s, grip strength on both the left and right side, and insulin-like growth factor-1(IGF-1) between groups were significantly higher in the EG compared with the CG. However, no differences were found in body composition, blood pyruvate, lactate, or high-sensitivity C-reactive protein (hsCRP) concentration between the two groups. In conclusion, FSO supplements may improve muscle strength in postmenopausal females with relatively reduced muscle strength without a change in muscle mass.
- Published
- 2022
- Full Text
- View/download PDF
40. Targeting neuroinflammation reduces synaptic, neuronal and cognitive loss in 5xFAD Alzheimer mice
- Author
-
Daniela Lecca, Yoo Jin Yung, Michael T Scerba, David Tweedie, Shih Chang Hsueh, Barry Hoffer, Dong Seok Kim, Ross A McDevitt, and Nigel H Greig
- Subjects
Psychiatry and Mental health ,Cellular and Molecular Neuroscience ,Developmental Neuroscience ,Epidemiology ,Health Policy ,Neurology (clinical) ,Geriatrics and Gerontology - Published
- 2022
41. Enhanced anomalous magnetization in carbonyl iron by Ni+ ion beam irradiation
- Author
-
Hyemin Jang, Jaekwon Suk, Chorong Kim, Dong Seok Kim, Won-Je Cho, Jun Kue Park, and Jae Sang Lee
- Subjects
Multidisciplinary ,Materials science ,Morin transition ,Ion beam ,Physics::Instrumentation and Detectors ,Science ,Analytical chemistry ,Morin ,chemistry.chemical_compound ,Magnetization ,chemistry ,Ferromagnetism ,Phase (matter) ,Antiferromagnetism ,Physics::Accelerator Physics ,Medicine ,Irradiation - Abstract
We investigate the magnetic properties in carbonyl iron (CI) particles before and after Ni$$^{+}$$ + and H$$^{+}$$ + ion beam irradiation. Upon increasing temperatures, the saturation magnetization ($$M_{\text {s}}$$ M s ) in hysteresis loops exhibits an anomalous increase at a high temperature for the unirradiated and the Ni$$^{+}$$ + -beam-irradiated samples, unlike in H$$^{+}$$ + -beam-irradiated sample. Moreover, the magnetization values at low and high temperatures are more intense after Ni$$^{+}$$ + beam irradiation, whereas after H$$^{+}$$ + beam irradiation those are remarkably suppressed. Hematite ($$\alpha $$ α -Fe$$_{2}$$ 2 O$$_{3}$$ 3 ) phase introduced on the surface of our CI particles undergoes the Morin transition that was observed in our magnetization-temperature curves. The Morin transition causing canted antiferromagnetism above the Morin temperature was found in the unirradiated and Ni$$^{+}$$ + -beam-irradiated samples, but not in H$$^{+}$$ + -beam-irradiated sample. It is thus revealed that the CI particles undergoing the Morin transition cause the anomalous increase in $$M_{\text {s}}$$ M s . We may suggest that Ni$$^{+}$$ + ion beam increases uncompensated surface spins on the CI particles resulting in a more steep Morin transition and the intensified $$M_{\text {s}}$$ M s . Ion-beam irradiation may thus be a good tool for controlling the magnetic properties of CI particles, tailoring our work for future applications.
- Published
- 2021
42. Anti-inflammatory effects of DA-9601, an extract of Artemisia asiatica, on aceclofenac-induced acute enteritis
- Author
-
Sun Woo Jang, Hyung-Gun Kim, Chang Yell Shin, Dong-Seok Kim, Wonae Lee, Hak Rim Kim, and Ju Hwan Kim
- Subjects
Pharmacology ,Physiology ,medicine.drug_class ,Chemistry ,medicine.medical_treatment ,T cell ,FOXP3 ,Inflammation ,medicine.disease ,Anti-inflammatory ,Small intestine ,Enteritis ,Proinflammatory cytokine ,Cytokine ,medicine.anatomical_structure ,medicine ,medicine.symptom - Abstract
DA-9601 is an extract obtained from Artemisia asiatica, which has been reported to have anti-inflammatory effects on gastrointestinal lesions; however, its possible anti-inflammatory effects on the small intestine have not been studied yet. Therefore, in this study, we investigated the protective effects of DA-9601 against the ACF-induced small intestinal inflammation. Inflammation of the small intestine was confirmed by histological studies and the changes in the CD4+ T cell fraction induced by the inflammation-related cytokines, and the inflammatory reactions were analyzed. Multifocal discrete small necrotic ulcers with intervening normal mucosa were frequently observed after treatment with ACF. The expression of IL-6 , IL-17, and TNF-α genes was increased in the ACF group; however, it was found to have been significantly decreased in the DA-9601 treated group. In addition, DA-9601 significantly decreased the levels of proinflammatory mediators such as IL-1β, GMCSF, IFN-γ, and TNF-α; the anti-inflammatory cytokine IL-10, on the other hand, was observed to have increased. It is known that inflammatory mediators related to T cell imbalance and dysfunction continuously activate the inflammatory response, causing chronic tissue damage. The fractions of IFN-γ+ Th1 cells, IL-4+ Th2 cells, IL-9+ Th9 cells, IL-17+ Th17 cells, and Foxp3+ Treg cells were significantly decreased upon DA-9601 treatment. These data suggest that the inflammatory response induced by ACF is reduced by DA-9601 via lowering of the expression of genes encoding the inflammatory cytokines and the concentration of inflammatory mediators. Furthermore, DA-9601 inhibited the acute inflammatory response mediated by T cells, resulting in an improvement in ACF-induced enteritis.
- Published
- 2021
43. An on-chip soft-start technique of current-mode DC-DC converter for biomedical applications.
- Author
-
Dong Seok Kim, Jungmoon Kim, Jihwan Kim, and Chulwoo Kim
- Published
- 2010
- Full Text
- View/download PDF
44. RayCore: A Ray-Tracing Hardware Architecture for Mobile Devices.
- Author
-
Jae-Ho Nah, Hyuck-Joo Kwon, Dong-Seok Kim, Cheol-Ho Jeong, Jin-Hong Park, Tack-Don Han, Dinesh Manocha, and Woo-Chan Park
- Published
- 2014
- Full Text
- View/download PDF
45. Experimental and simulation study of power performance improvement of <scp>GaN PIN</scp> betavoltaic cell
- Author
-
Dong-Seok Kim, Jung-Hee Lee, In Man Kang, Young Jun Yoon, and Jae Sang Lee
- Subjects
Betavoltaics ,Fuel Technology ,Materials science ,Nuclear Energy and Engineering ,Depletion region ,Renewable Energy, Sustainability and the Environment ,business.industry ,Energy Engineering and Power Technology ,Optoelectronics ,Power performance ,E beam irradiation ,business ,p–n junction - Published
- 2021
46. Temporary Surgical Management of Intraventricular Hemorrhage in Premature Infants.
- Author
-
Eun-Kyung Park, Ja-Yoon Kim, Dong-Seok Kim, and Kyu-Won Shim
- Subjects
PREMATURE infants ,LOW birth weight ,INTRAVENTRICULAR hemorrhage ,WEIGHT gain ,INTRACRANIAL hemorrhage ,CEREBROSPINAL fluid shunts - Abstract
Post-hemorrhagic hydrocephalus (PHH) in preterm infant is common, life-threatening and the main cause of bad developmental outcomes. Ventriculoperitoneal (VP) shunt is used as the ultimate treatment for PHH. Low birth weight and low gestational age are the combination of worse prognostic factors while the single most important prognostic factor of VP shunting is age. Aggressive and early intervention have better effect in intraventricular hemorrhage and intracranial pressures control. It reduces infection rate and brain damage resulted in delayed shunt insertion. It is extremely important to let PHH infants get older and gain weight to have internal organs to be matured before undergoing VP shunt. As premature infants undergo shunt after further growth, shunt-related complications would be reduced. So temporary surgical intervention is critical for PHH infants to have them enough time until permanently shunted. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
47. Distributed Programming Developing Tool Based on Distributed Object Group Framework.
- Author
-
Chang-Won Jeong, Dong-Seok Kim, Geon-Yeob Lee, and Su-Chong Joo
- Published
- 2006
- Full Text
- View/download PDF
48. Ubiquitous Healthcare System Using Context Information Based on the DOGF.
- Author
-
Chang-Sun Shin, Dong-In Ahn, Dong-Seok Kim, and Su-Chong Joo
- Published
- 2006
- Full Text
- View/download PDF
49. Outcomes of intracranial non-germinomatous germ cell tumors: a retrospective Asian multinational study on treatment strategies and prognostic factors
- Author
-
Kyung Taek Hong, Jung Woo Han, Hiroshi Fuji, Hwa Kyung Byun, Kyung-Nam Koh, Ru Xin Wong, Hsin-Lun Lee, Hong In Yoon, Joo Ho Lee, Ji Hoon Phi, Seung-Ki Kim, Dong-Seok Kim, Chuhl Joo Lyu, Jung Yoon Choi, Hyoung Jin Kang, Yi-Wei Chen, Yi-Yen Lee, Ho Joon Im, Young-Shin Ra, Seung Do Ahn, Sharon Yin Yee Low, Wen Shen Looi, Hyeon Jin Park, Yang-Gun Suh, Chang-Ok Suh, Kyu-Chang Wang, Enrica Ee Kar Tan, Tai-Tong Wong, and Joo-Young Kim
- Subjects
Male ,Cancer Research ,Neurology ,Oncology ,Brain Neoplasms ,Humans ,Chorionic Gonadotropin, beta Subunit, Human ,Neurology (clinical) ,Germinoma ,Neoplasms, Germ Cell and Embryonal ,Child ,Prognosis ,Retrospective Studies - Abstract
Non-germinomatous germ cell tumors (NGGCTs) are rare pediatric conditions. This multicenter study using Asian multinational patient data investigated treatment outcomes and prognostic factors for NGGCTs.Medical records of 251 patients with NGGCTs treated from 1995 to 2015 were retrospectively analyzed from participating centers in Asian countries (Korea, Taiwan, Singapore, and Japan).The median follow up was 8.5 years (95% CI 7.8-9.9). In the total cohort, 5-year event-free survival (EFS) and overall survival (OS) rates were 78.2% and 85.4%, respectively. In 17.9% of the patients, diagnosis was determined by tumor markers alone (alpha-fetoprotein ≥ 10 ng/mL (Korea) or 25 ng/mL (Taiwan and Singapore), and/or β-human chorionic gonadotropin (β-hCG) ≥ 50 mIU/mL). Patients with immature teratomas and mature teratomas comprised 12.0% and 8.4%, respectively. The 5-year EFS rate was higher in patients with histologically confirmed germinoma with elevated β-hCG (n = 28) than those in patients with malignant NGGCTs (n = 127). Among malignant NGGCTs, patients with choriocarcinoma showed the highest 5-year OS of 87.6%, while yolk sac tumors showed the lowest OS (68.8%). For malignant NGGCT subgroups, an increase in serum β-hCG levels by 100 mIU/mL was identified as a significant prognostic factor associated with the EFS and OS.Our result shows excellent survival outcomes of overall CNS NGGCT. However, treatment outcome varied widely across the histopathologic subgroup of NGGCT. Hence, this study suggests the necessity for accurate diagnosis by surgical biopsy and further optimization of diagnosis and treatment according to the histopathology of NGGCTs. Future clinical trials should be designed for individualized treatments for different NGGCTs subsets.
- Published
- 2022
50. Fluorine improvement of MOSFET interface as revealed by RTS measurements and HRTEM.
- Author
-
Joo Hyung Kim, Jung Joo Kim, Chang-Eun Lee, Jong Ho Lee, Dong Seok Kim, Nam Joo Kim, Kwang Dong Yoo, and Heung-Soo Park
- Published
- 2013
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.