Effect of Strain Aging on Tensile Behavior and Properties of API X60, X70, and X80 Pipeline Steels

Sang‑In Lee,Seung‑Yong Lee,Seok Gyu Lee,Hwan Gyo Jung,Byoungchul Hwang 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

The effect of strain aging on tensile behavior and properties of API X60, X70, and X80 pipeline steels was investigated inthis study. The API X60, X70, and X80 pipeline steels were fabricated by varying alloying elements and thermomechanicalprocessing conditions. Although all the steels exhibited complex microstructure consisting of polygonal ferrite (PF), acicularferrite, granular bainite (GB), bainitic ferrite (BF), and secondary phases, they had different fractions of microstructuresdepending on the alloying elements and thermomechanical processing conditions. The tensile test results revealed that yieldingbehavior steadily changed from continuous-type to discontinuous-type as aging temperature increases after 1% pre-strain. After pre-strain and thermal aging treatment in all the steels, the yield and tensile strengths, and yield ratio were increased,while the uniform elongation and work hardening exponent were decreased. In the case of the X80 steel, particularly, thedecrease in uniform elongation was relatively small due to many mobile dislocations in PF, and the increase in yield ratiowas the lowest because a large amount of harder microstructures such as GB, BF, and coarse secondary phases effectivelyenhanced work hardening.

Extent of resection for T2N0 gallbladder carcinoma regarding concurrent extrahepatic bile duct resection

Sung-Chan Gwark,Shin Hwang,Ki-Hun Kim,Yong-Joo Lee,Kwang-Min Park,Chul-Soo Ahn,Deok-Bog Moon,Tae-Yong Ha,Gi-Won Song,Dong-Hwan Jung,Gil-Chun Park,Sung-Gyu Lee 한국간담췌외과학회 2012 한국간담췌외과학회지 Vol.16 No.4

Backgrounds/Aims: Gallbladder carcinoma (GBCa) T2 lesions are considered to be advanced tumors showing diverse features in tumor extent. When this T2 lesion does not involve the cystic duct and there is no evidence of lymph node metastasis, we have to consider what is the most reasonable extent of resection - that is, whether to perform concurrent extra-hepatic bile duct resection (EHBD) resection or not. This study intends to evaluate the adequacy of EHBD resection in patients undergoing resection for T2N0 GBCa. Methods: From our institutional database of GBCa, 48 cases of T2N0 GBCa who underwent R0 resection during November 1995 and August 2008 were selected. Patients who underwent prior laparoscopic cholecystectomy were excluded. Their medical records were reviewed retrospectively. Results: Their mean age was 63.2±83.3 years and females were 25. The mean serum CA19-9 level was 37.3±89.3 ng/ml. The extents of liver resection were wedge resection (n=36) and segment 4a+5 resection (n=12). Concurrent EHBD resection was performed in 16 (33.3%) patients. No fatal surgical complication occurred. The majority of tumor pathology was adenocarcinoma (n=42), with additional unusual types as papillary (n=3), saromatoid (n=1), signet ring cell (n=1) and adenosquamous (n=1) cancers. The overall survival rate was 87.1% at 1 year, 69.5% at 3 years and 61.7% at 5 years. After exclusion of mortalities not related to cancer, the overall patient survival rate was 89.6% at 1 year, 72.9% at 3 years and 64.7% at 5 years, with 3-year survival rates of 72% in the EHBD resection group and 69.2% in the non-resection group (p=0.661). Conclusions: The results of this study indicate that concurrent EHBD resection did not improve patient survival when R0 resection was achieved in patients with T2N0 GBCa. Therefore, routine EHBD resection may not be indicated for T2N0 GBCa unless the tumor is close to the cystic duct. (Korean J Hepatobiliary Pancreat Surg 2012;16:142-146)

Miniature J-T cryocooler using argon and nitrous oxide mixture

Hwang, Gyu-Wan,Jeong, Sang-Kwon The Korean Society of Superconductivity and Cryoge 2008 한국초전도저온공학회논문지 Vol.10 No.4

Miniature J-T cryocooler using nitrogen or argon has been widely adopted in cooling infrared sensor for space/military application and cryosurgery. Argon or nitrogen, however, has relatively low specific cooling power compared to nitrous oxide, but the ultimate operating temperature is much lower than nitrous oxide. On the other hand, nitrous oxide has large specific cooling power, but the operating temperature is limited to its boiling point (>183K). To compromise the different characteristics of these gases, the performance of miniature J-T cryocooler using argon and nitrous oxide mixture is investigated in this paper. Three different compositions of mixture (25/75, 50/50, and 75/25 molar fraction) are blended and tested. The results are compared with the experiments of pure argon and pure nitrous oxide. The experimental results show some encouraging potentiality of mixed refrigerant J-T cryocooler. The critical clogging problem, however, was observed with argon and nitrous oxide mixture, and the lowest achievable temperature with this mixture was limited to the freezing point of nitrous oxide. The paper discusses detailed clogging process of the mixture and suggests an alternative.

Gapped Nearly Free-Standing Graphene on an SiC(0001) Substrate Induced by Manganese Atoms

Hwang, Jinwoong,Lee, Ji-Eun,Kang, Minhee,Park, Byeong-Gyu,Denlinger, Jonathan,Mo, Sung-Kwan,Hwang, Choongyu The Korean Vacuum Society 2018 Applied Science and Convergence Technology Vol.27 No.5

The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angle-resolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene, that is observed in pristine graphene indicating intrinsic electron-doping by the substrate, completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases by the presence of manganese atoms, approaching the electron band structure calculated using the local density approximation method. The former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition. The latter suggests that its electronic correlations are efficiently screened, suggesting that the dielectric property of the substrate is modified by manganese atoms and indicating that electronic correlations in grpahene can also be tuned by foreign atoms. These results pave the way for promising device application using graphene that is semiconducting and charge neutral.

Selection of working fluid for cryosurgical probe considering biological heat transfer

Hwang, Gyu-Wan,Jeong, Sang-Kwon The Korean Society of Superconductivity and Cryoge 2007 한국초전도저온공학회논문지 Vol.9 No.4

This paper describes the sensitive cooling performance change of J-T refrigerator for cryosurgical probe due to its working fluid. The analytical results of using 50 bar nitrous oxide are compared with the case of 300 bar argon. Bio-heat equation is numerically solved to investigate the effect of the probe temperature and the cooling power of the J-T refrigerator. The refrigerator using 50 bar nitrous oxide has larger cooling power above 185 K than the one with 300 bar argon, which enables fast cooling at early stage of cryosurgery, but the biological tissue away from the probe tends to be cooled slowly after the probe reaches its lowest operating temperature. When the repeated freeze-thaw cycle is employed for main tissue destruction mechanism, using high pressure nitrous oxide is more advantageous than argon if the freezing operation is within 2-3 minutes. The probe with high pressure argon is more suitable for the case of longer freeze-thaw cycle with fewer repetitions.

Identification of Antiangiogenic Potential and Cellular Mechanisms of Napyradiomycin A1 Isolated from the Marine-Derived <i>Streptomyces</i> sp. YP127

Hwang, Ji Sun,Kim, Geum Jin,Choi, Hyun Gyu,Kim, Min Cheol,Hahn, Dongyup,Nam, Joo-Won,Nam, Sang-Jip,Kwon, Hak Choel,Chin, Jungwook,Cho, Sung Jin,Hwang, Hayoung,Choi, Hyukjae American Chemical Society and American Society of 2017 Journal of natural products Vol.80 No.8

<P>Angiogenesis is the process of new blood vessel formation. Excessive angiogenesis is a critical factor in the progression of cancer, macular degeneration, and other chronic inflammatory diseases. When investigating the effects of crude extracts of cultured marine microorganisms, an extract of the cultured Streptomyces sp. YP127 strain was found to inhibit human umbilical vein endothelial cell (HUVEC) tube formation. Bioassay-guided fractionation and spectroscopic data analyses led to the identification of napyradiomycin A1 (1) as an antiangiogenic component of the extract. Compound 1 inhibited HUVEC tube formation in a concentration-dependent manner. It inhibited endothelial cell proliferation but did not affect human dermal fibroblast proliferation. Compound 1 also suppressed migration and invasion of vascular endothelial cells. In addition, compound 1 suppressed vascular endothelial cadherin expression and increased the permeability of the endothelial cell membrane. These results suggested that compound 1 modulates cell permeability and inhibits the angiogenesis of endothelial cells.</P>

Switching of Photonic Crystal Lasers by Graphene

Hwang, Min-Soo,Kim, Ha-Reem,Kim, Kyoung-Ho,Jeong, Kwang-Yong,Park, Jin-Sung,Choi, Jae-Hyuck,Kang, Ju-Hyung,Lee, Jung Min,Park, Won Il,Song, Jung-Hwan,Seo, Min-Kyo,Park, Hong-Gyu American Chemical Society 2017 NANO LETTERS Vol.17 No.3

<P>Unique features of graphene have motivated the development of graphene-integrated photonic devices. In particular, the electrical tunability of graphene loss enables high-speed modulation of light and tuning of cavity resonances in graphene-integrated waveguides and cavities. However, efficient control of light emission such as lasing, using graphene, remains a challenge. In this work, we demonstrate on/off switching of single- and double-cavity photonic crystal lasers by electrical gating of a monolayer graphene sheet on top of photonic crystal cavities. The optical loss of graphene was controlled by varying the gate voltage V-g, with the ion gel atop the graphene sheet. First, the fundamental properties of graphene were investigated through the transmittance measurement and numerical simulations. Next, optically pumped lasing was demonstrated for a graphene-integrated single photonic crystal cavity at V-g below-0.6 V, exhibiting a low lasing threshold of -4801 mu W, whereas lasing was not observed at V-g above -0.6 V owing to the intrinsic optical loss of graphene. Changing quality factor of the graphene-integrated photonic crystal cavity enables or disables the lasing operation. Moreover, in the double-cavity photonic crystal lasers with graphene, switching of individual cavities with separate graphene sheets was achieved, and these two lasing actions were controlled independently despite the close distance of -2.2 mu m between adjacent cavities. We believe that our simple and practical approach for switching in graphene-integrated active photonic devices will pave the way toward designing high-contrast and ultracompact photonic integrated circuits.</P>

Olig2 is expressed late in human eosinophil development and controls Siglec-8 expression

Hwang, Sae Mi,Uhm, Tae Gi,Lee, Seol Kyung,Kong, Su-Kang,Jung, Kyung Hwa,Binas, Bert,Chai, Young Gyu,Park, Sung Woo,Chung, Il Yup Wiley (John WileySons) 2016 Journal of leukocyte biology Vol.100 No.4

<P>Oligodendrocyte transcription factor 2, a basic helix-loop-helix transcription factor that binds to E-box motifs, is known to have a key role in determining lineage specification of oligodendrocytes and motor neurons. In the present study, we report that oligodendrocyte transcription factor 2 is expressed in human eosinophils and involved in transcriptional activation of the gene encoding sialic acid binding immunoglobulin-like lectin 8 (Siglec-8), a late eosinophil-differentiation marker known to exert eosinophil apoptosis. When cord blood CD34(+) hematopoietic stem cells differentiated toward eosinophils during a 24-d culture period, oligodendrocyte transcription factor 2 protein was expressed in cord blood eosinophils on d 24, a time when cord blood eosinophils are considered fully differentiated, whereas it was not detectable on d 18 or at earlier time points. Oligodendrocyte transcription factor 2 protein was also abundantly expressed in human peripheral-blood eosinophils but not in neutrophils, monocytes, lymphocytes, or cord blood mast cells. RNA sequencing analysis showed that numerous genes, especially those encoding eosinophil surface molecules, were highly up-regulated along with OLIG2. Among the genes examined, SIGLEC-8 messenger RNA and protein were markedly downregulated in parallel with OLIG2 by an oligodendrocyte transcription factor 2 small interfering RNA or a short hairpin RNA, as evidenced by real-time polymerase chain reaction, fluorescence-activated cell sorting, and Western blot analyses. In reporter gene and chromatin immunoprecipitation experiments, an E-box in the first intron was found to stimulate SIGLEC-8 gene transcription and to bind oligodendrocyte transcription factor 2. Hence, at least one important aspect of eosinophil differentiation is regulated by oligodendrocyte transcription factor 2, a transcription factor that has not previously been reported, to our knowledge, in normal granulocytes.</P>

Long-term results of conjoined unification venoplasty for multiple portal vein branches of the right liver graft in living donor liver transplantations

Sung-Gyu Lee,Shin Hwang,Tae Yong Ha,Gi Won Song,Dong-Hwan Jung,Gil-Chun Park,Chul-Soo Ahn,Deok-Bog Moon,Ki Hun Kim,Young-In Yoon,Yo Han Park,Hui-Dong Cho,Yong-Kyu Chung,Sang-Hyun Kang,Jin-Uk Choi,Sung 대한이식학회 2019 Korean Journal of Transplantation Vol.33 No.4

Background: Autologous portal vein Y-graft (PYG) interposition has been the standard procedure for reconstruction of double portal vein (PV) orifices of right liver grafts during living donor liver transplantations. However, it has the disadvantage of being vulnerable to anastomotic stenosis. A refined technique of conjoined unification venoplasty (CUV) was developed to secure PV reconstruction. Methods: We reviewed the surgical outcomes in PV reconstructions using CUVs in 21 cases which were followed up for >3 years. Results: The mean age of recipients was 51.7±4.9 years. The model for end-stage liver disease score was 15.3±6.4. The graft-recipient weight ratio was 1.12±0.21. Recipient PYGs were harvested in all cases. All living donors were blood relatives or relatives through marriage with type III PV anomalies. The number of right liver graft PV orifices was two in 19 cases and three in two cases. For the central intervening vein patch, a PV segment was used in six cases, and an autologous greater saphenous vein patch was used in the remaining 15 cases. The 21 patient cohort displayed a 100% 4-year patient survival rate. None of them underwent any PV interventions including interventional stenting. Serial follow-up computed tomography scans revealed that the reconstructed PV showed early reshaping with a stable streamlined configuration for over 3 years. Conclusions: PV reconstruction using the CUV technique appears to be significantly more effective in preventing PV complications. We believe that CUV is a useful technique to reconstruct right liver grafts with multiple PV orifices.

Structural insights into the regulation of sialic acid catabolism by the <i>Vibrio vulnificus</i> transcriptional repressor NanR

Hwang, Jungwon,Kim, Byoung Sik,Jang, Song Yee,Lim, Jong Gyu,You, Dong-Ju,Jung, Hyun Suk,Oh, Tae-Kwang,Lee, Jie-Oh,Choi, Sang Ho,Kim, Myung Hee National Academy of Sciences 2013 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.110 No.30

<P>Pathogenic and commensal bacteria that experience limited nutrient availability in their host have evolved sophisticated systems to catabolize the mucin sugar N-acetylneuraminic acid, thereby facilitating their survival and colonization. The correct function of the associated catabolic machinery is particularly crucial for the pathogenesis of enteropathogenic bacteria during infection, although the molecular mechanisms involved with the regulation of the catabolic machinery are unknown. This study reports the complex structure of NanR, a repressor of the N-acetylneuraminate (nan) genes responsible for N-acetylneuraminic acid catabolism, and its regulatory ligand, N-acetylmannosamine 6-phosphate (ManNAc-6P), in the human pathogenic bacterium Vibrio vulnificus. Structural studies combined with electron microscopic, biochemical, and in vivo analysis demonstrated that NanR forms a dimer in which the two monomers create an arched tunnel-like DNA-binding space, which contains positively charged residues that interact with the nan promoter. The interaction between the NanR dimer and DNA is alleviated by the ManNAc-6P-mediated relocation of residues in the ligand-binding domain of NanR, which subsequently relieves the repressive effect of NanR and induces the transcription of the nan genes. Survival studies in which mice were challenged with a ManNAc-6P-binding-defective mutant strain of V. vulnificus demonstrated that this relocation of NanR residues is critical for V. vulnificus pathogenesis. In summary, this study presents a model of the mechanism that regulates sialic acid catabolism via NanR in V. vulnificus.</P>