Raman signatures of spin-phonon coupling in a self-intercalated van der Waals magnet Mn3Si2Te6

Kwon Chang Il,Kim Kwangrae,Kim So Young,Susilo Resta A.,Kang Beomtak,Kim Kyoo,Kim Duck Young,Kim Jonghwan,Kim B.J.,Kim Jun Sung 한국물리학회 2023 Current Applied Physics Vol.53 No.-

We report the results of Raman spectroscopy on a self-intercalated van der Waals ferrimagnet Mn3Si2Te6. Using polarization-resolved Raman spectroscopy, we identify twelve phonon modes with Eg and A1g symmetries, in agreement with the first principle calculations. Below the ferrimagnetic transition temperature Tc ∼ 78 K, we observed a significant deviation of the phonon frequency from the anharmonic model, accompanied by a strong line broadening, indicating a substantial spin-phonon coupling in Mn3Si2Te6. Among twelve phonon modes, this spin-phonon coupling is found to be strong mostly in the out-of-plane vibrational modes. These results highlight the dominant role of the interlayer superexchange interaction in determining the magnetic properties, reflecting the self-intercalated van der Waals structure of Mn3Si2Te6.

Optimization of Operation Parameters for Direct Spring Loaded Pressure Relief Valve in a Pipeline System

Kim, Hyunjun,Kim, Sanghyun,Kim, Youngman,Kim, Jonghwan ASME International 2018 Journal of Pressure Vessel Technology Vol.140 No.5

UV-curing kinetics and performance development of <i>in situ</i> curable 3D printing materials

Kim, Ye Chan,Hong, Sungyong,Sun, Hanna,Kim, Myeong Gi,Choi, Kisuk,Cho, Jungkeun,Choi, Hyouk Ryeol,Koo, Ja Choon,Moon, Hyungpil,Byun, Doyoung,Kim, Kwang J.,Suhr, Jonghwan,Kim, Soo Hyun,Nam, Jae-Do Elsevier 2017 European polymer journal Vol.93 No.-

<P><B>Abstract</B></P> <P>As three-dimensional (3D) printing technology is emerging as an alternative way of manufacturing, the high resolution 3D printing device often requires systems such as drop jetting printing of <I>in situ</I> UV-curable photopolymers. Accordingly, the key issue is process control and its optimization to ensure dimensional accuracy, surface roughness, building orientation, and mechanical properties of printed structures, which are based on the time- and temperature-dependent glass transition temperature (<I>T<SUB>g</SUB> </I>) of the resin system under UV-curing. In this study, the UV-cure kinetics and <I>T<SUB>g</SUB> </I> development of a commercially available UV-curable acrylic resin system were investigated as a model system, using a differential scanning photocalorimeter (DPC). The developed kinetic model included the limited conversion of cure that could be achieved as a maximum at a specific isothermal curing temperature. Using the developed model, the <I>T<SUB>g</SUB> </I> was successfully described by a modified DiBenedetto equation as a function of UV curing. The developed kinetic model and <I>T<SUB>g</SUB> </I> development can be used to determine the 3D printing operating conditions for the overlay printing and <I>in situ</I> UV curing, which could ensure high-resolution and high-speed manufacturing with various UV-curing materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UV-cure kinetic analysis were applied to a commercial Multi-jet 3D printing material. </LI> <LI> The developed kinetic model included the limited conversion of cure by temperature. </LI> <LI> The <I>T<SUB>g</SUB> </I> was described by a modified DiBenedetto equation as a function of UV curing. </LI> <LI> The developed kinetic model showed an excellent agreement to isothermal experiments. </LI> <LI> The overlay printing time for each isothermal temperature was determined. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Staufen1-mediated mRNA decay induces Requiem mRNA decay through binding of Staufen1 to the Requiem 3′UTR

Kim, Min Young,Park, Jungyun,Lee, Jong Joo,Ha, Dae Hyun,Kim, Jonghwan,Kim, Chan Gil,Hwang, Jungwook,Kim, Chul Geun Oxford University Press 2014 Nucleic acids research Vol.42 No.11

<P>Requiem (REQ/DPF2) was originally identified as an apoptosis-inducing protein in mouse myeloid cells and belongs to the novel Krüppel-type zinc finger d4-protein family of proteins, which includes neuro-d4 (DPF1) and cer-d4 (DPF3). Interestingly, when a portion of the REQ messenger ribonucleic acid (mRNA) 3′ untranslated region (3′UTR), referred to as G8, was overexpressed in K562 cells, β-globin expression was induced, suggesting that the 3′UTR of REQ mRNA plays a physiological role. Here, we present evidence that the REQ mRNA 3′UTR, along with its <I>trans</I>-acting factor, Staufen1 (STAU1), is able to reduce the level of REQ mRNA via STAU1-mediated mRNA decay (SMD). By screening a complementary deoxyribonucleic acid (cDNA) expression library with an RNA–ligand binding assay, we identified STAU1 as an interactor of the REQ mRNA 3′UTR. Specifically, we provide evidence that STAU1 binds to putative 30-nucleotide stem–loop-structured RNA sequences within the G8 region, which we term the protein binding site core; this binding triggers the degradation of REQ mRNA and thus regulates translation. Furthermore, we demonstrate that siRNA-mediated silencing of either STAU1 or UPF1 increases the abundance of cellular REQ mRNA and, consequently, the REQ protein, indicating that REQ mRNA is a target of SMD.</P>

스타이렌-무수말레인산 그래프트 반응에 의한 폴리에틸렌 왁스의 극성 특성 향상

김정식(Jeongsik Kim),송지은(Jieun Song),임민지(Minji Im),김효철(Hyochul Kim),김종환(Jonghwan Kim),김형일(Hyung-Il Kim) 한국고분자학회 2018 폴리머 Vol.42 No.4

열분해 반응을 통해 제조된 비극성 폴리에틸렌 왁스에 스타이렌과 무수말레인산 단량체를 그래프트 반응시켜 극성을 가지는 기능성 왁스를 제조하였다. 그래프트 반응 인자에 따라 폴리에틸렌 왁스의 산도 변화를 조사하였다. 무수말레인산 단독으로 그래프트된 폴리에틸렌 왁스보다 스타이렌과 무수말레인산의 교대공중합을 통해 그래프트된 폴리에틸렌 왁스가 월등히 높은 산도를 나타내었다. 또한 가수분해를 추가적으로 진행한 폴리에틸렌 왁스는 산무수 물기의 카복실기 형성으로 더 높은 산도를 보여주었다. 개시제의 분해온도 영향으로 무수말레인산 단독으로 그래프트된 폴리에틸렌 왁스 합성에서는 디큐밀퍼옥사이드 개시제가 더 높은 산도를 나타냈다. 반면, 낮은 반응온도에서스타이렌과 무수말레인산 공중합체가 그래프트된 폴리에틸렌 왁스 합성에서는 벤조일퍼옥사이드 개시제가 더 높은 산도를 나타내었다. Polar functional polyethylene wax was prepared by grafting maleic anhydride and styrene monomers on nonpolar polyethylene wax which was produced by pyrolysis process. The acidity variation of polyethylene wax was investigated depending on the graft reaction variables. The polar functional polyethylene wax, which was prepared by grafting via alternating copolymerization of styrene and maleic anhydride, showed the significantly higher acid value compared to the polyethylene wax grafted with maleic anhydride alone. As the anhydride group of polar functional polyethylene wax was hydrolyzed to form carboxylic acid groups, the acid value of hydrolyzed functional polyethylene wax increased further. Due to the effect of initiator decomposition temperature, dicumyl peroxide resulted in the higher acid value of polyethylene wax in the grafting with maleic anhydride alone. On the other hand, benzoyl peroxide resulted in the higher acid value of polyethylene wax in the grafting with maleic anhydride and styrene together at lower temperature.

열분해 폴리에틸렌 왁스의 아크릴산 그래프트 반응 특성

김정식(Jeongsik Kim),김효철(Hyochul Kim),김종환(Jonghwan Kim),윤주한(Juhan Youn),김형일(Hyung-il Kim) 한국고분자학회 2017 폴리머 Vol.41 No.5

열분해 반응을 통해 제조된 비극성 폴리에틸렌 왁스에 대해 극성 아크릴산 단량체를 그래프트 반응시켜 기능성 첨가제를 제조하였고, 반응인자가 그래프트 효율에 미치는 영향을 조사하였다. 폴리에틸렌 왁스의 분자량이 작을수록 그래프트율이 증가하였다. 아크릴산 함량이 증가할수록 그래프트율이 증가하였으나 과량의 아크릴산 함량에서는 비극성 반응물과의 혼화성이 불량하여 그래프트율이 감소하였다. 반응시간이 증가하거나 반응온도가 증가함에 따라 폴리에틸렌 사슬에 그래프트 반응활성점이 증가하여 그래프트율이 향상되었다. 개시제로는 반감기가 더 긴 라디칼 개시제가 동일 반응조건에서 더 높은 그래프트율을 나타내었다. 그래프트율이 증가할수록 그래프트 폴리에틸렌 왁스의 유리전이온도는 감소하였다. Functional additives were prepared by grafting polar acrylic acid on nonpolar polyethylene wax which was produced by pyrolysis. The effect of reaction factors on grafting degree was investigated. The grafting degree increased as the molecular weight of polyethylene wax decreased. Although the grafting degree increased as acrylic acid content increased, the grafting degree became lower in case of excess acrylic acid content due to the incompatibility with nonpolar reaction medium. The grafting degree increased as both reaction temperature and reaction time increased because of the increased formation of reaction active sites on polyethylene chains. The radical initiator of longer half life gave the higher grafting degree at the same reaction conditions. Glass transition temperature of grafted polyethylene wax decreased as the grafting degree increased.

Isolation, structure elucidation, total synthesis, and biosynthesis of dermazolium A, an antibacterial imidazolium metabolite of a vaginal bacterium Dermabacter vaginalis

Hye Ryeong Kim,Jonghwan Kim,Jae Sik Yu,Bum Soo Lee,Ki Hyun Kim,Chung Sub Kim 대한약학회 2023 Archives of Pharmacal Research Vol.46 No.1

Dermabacter vaginalis is a human-derived bacterium isolated from vaginal fluid of a Korean female in 2016. Although several human-related species in Dermabacter genus have been reported there are few studies on their bioactive metabolites. Dermazolium A (1), a rare imidazolium metabolite, was isolated from D. vaginalis along with five known metabolites (2–6) and their chemical structures were determined by NMR, HRMS, and MS/MS data analysis. Feeding experiments using predicted precursors and biomimetic total synthesis of 1 corroborated its structure and led to suggestion of biosynthetic pathway of 1. Antibacterial tests on the isolated compounds showed that 1 is a mild antibacterial agent with MIC values of 41 µg/mL against methicillin-resistant Staphylococcus aureus (MRSA) USA300, Lacticaseibacillus paracasei subsp. paracasei KCTC 3510 and Brevibacterium epidermidis KCTC 3090.

Memristor 특성에 따른 MLP(Multi-layer perceptron) 학습률의 변화

김예빈(Yebin Kim),김경진(Gyeongjin Kim),김민지(Minji Kim),김설현(Seolhyeon Kim),염지윤(Jiyoon Yeom),이종환(Jonghwan Lee) 대한전기학회 2023 대한전기학회 학술대회 논문집 Vol.2023 No.11

레이저로 적층 제조한 금속 기지재 복합재료의 설계 및 제조 연구동향

김민겸 ( Min-kyeom Kim ),김태환 ( Taehwan Kim ),김주원 ( Ju-won Kim ),김동원 ( Dongwon Kim ),방영젠 ( Yongjian Fang ),노종환 ( Jonghwan No ),서종환 ( Jonghwan Suhr ) 한국복합재료학회 2021 Composites research Vol.34 No.4

금속 기지재 복합재료들(MMCs, Metal matrix composites)은 우수한 기계적 물성(강성, 강도, 마모 저항성, 경도 등)과 뛰어난 특성(열전도, 전기전도도, 부식 저항 등)으로 다양한 산업군에 활용되고 있다. 적층제조 기술이 발달함에 따라 복잡한 형상을 시간과 비용을 절약하여 제조할 수 있다는 이점으로, 적층 제조한 MMCs에 관한 연구가 활발하게 이루어지고 있다. 하지만 MMCs를 적층 제조할 경우, 다양한 원인들에 의해 여러 문제들이 발생할 수 있다. 따라서 본 연구에서는 다양한 MMCs의 특징들을 소개하고, 위의 문제들이 발생하는 원인을 고찰하여 소재와 Powder bed fusion (PBF) 공정 설계 관점에서 해결책을 제시하고자 한다. 본 논문은 향후 PBF 방식으로 적층 제조한 MMCs를 개발할 때 설계 및 제조 가이드라인을 제시하여 줄 수 있을 것이다. Metal matrix composites (MMCs) were widely used in various industries, due to the excellent properties: high strength, stiffness, wear resistance, hardness, thermal conductivity, electrical conductivity, etc. With additive manufacturing (AM) technology rapidly developed, AM MMCs have been actively investigated thanks to the cost- and time-saving manufacturing. However, several issues still need to be addressed before fabricating AM MMCs. Here, several types of MMCs were introduced and MMCs’ design methods to tackle the issues were suggested in a powder bed fusion (PBF) technique. The paper could come up with a guideline for the material and process design of MMCs in the PBF technique.

National Follow-up Survey of Preventable Trauma Death Rate in Korea

Kwon Junsik,Lee Myeonggyun,Moon Jonghwan,Huh Yo,Song Seoyoung,Kim Sora,Lee Seung Joon,Lim Borami,Kim Hyo Jin,Kim Yoon,il Kim Hyung,Yun Jung-Ho,Yu Byungchul,Lee Gil Jae,Kim Jae Hun,Kim Oh Hyun,Choi Woo 대한의학회 2022 Journal of Korean medical science Vol.37 No.50

Background: The preventable trauma death rate survey is a basic tool for the quality management of trauma treatment because it is a method that can intuitively evaluate the level of national trauma treatment. We conducted this study as a national biennial follow-up survey project and report the results of the review of the 2019 trauma death data in Korea. Methods: From January 1, 2019 to December 31, 2019, of a total of 8,482 trauma deaths throughout the country, 1,692 were sampled from 279 emergency medical institutions in Korea. All cases were evaluated for preventability of death and opportunities for improvement using a multidisciplinary panel review approach. Results: The preventable trauma death rate was estimated to be 15.7%. Of these, 3.1% were judged definitive preventable deaths, and 12.7% were potentially preventable deaths. The odds ratio for preventable traumatic death was 2.56 times higher in transferred patients compared to that of patients who visited the final hospital directly. The group that died 1 hour after the accident had a statistically significantly higher probability of preventable death than that of the group that died within 1 hour after the accident. Conclusion: The preventable trauma death rate for trauma deaths in 2019 was 15.7%, which was 4.2%p lower than that in 2017. To improve the quality of trauma treatment, the transfer of severe trauma patients to trauma centers should be more focused.