Effect of Heat Treatment on Microstructure and Fracture Behavior of STS304-Zr Alloys for Metal Waste Forms

Three kinds of STS304-Zr alloys were fabricated by varying the Zr content, and their microstructure and fracture properties were analyzed. Moreover, we performed heat treatment to improve their properties and studied their microstructure and fracture properties. The microstructure of the STS304-Zr alloys before and after the heat treatment process consisted of α-Fe and intermetallics: Zr(Cr, Ni, Fe)2 and Zr6Fe23. The volume fraction of the intermetallics increased with an increasing Zr content. The 11Zr specimen exhibited the lowest hardness and fine dimples and cleavage facets in a fractured surface. The 15Zr specimen had high hardness and fine cleavage facets. The 19Zr specimen had the highest hardness and large cleavage facets. After the heat treatment process, the intermetallics were spheroidized and their volume fraction increased. In addition, the specimens after the heat treatment process, the Laves phase (Zr(Cr, Ni, Fe) 2) decreased, the Zr6Fe23 phase increased and the Ni concentration in the intermetallics decreased. The hardness of all the specimens after the heat treatment process decreased because of the dislocations and residual stresses in α-Fe, and the fine lamellar shaped eutectic microstructures changed into large α-Fe and spheroidized intermetallics. The cleavage facet size increased because of the decomposition of the fine lamellarshaped eutectic microstructures and the increase in spheroidized intermetallics.11Yscopuskc

과거 10년간의 Neisseria gonorrhoeae 분리와 penicillinase 생성 및 항균제 감수성에 관한 연구

보건학과/석사[한글] 임질은 성병중 흔한 것이지만 우리나라에 있어서의 환자 발생수는 파악이 되어 있지 않다. Penicillinase-producing Neisseria gonorrhoeae(PPNG)의 출현은 임질의 증가를 염려하게 하고 있도 또한 치료약의 선택을 어렵게 하고 있다. 이 연구에서는 연세의료원의 1975년에서 1984년의 부인과 검체와 눈 검체에서의 임균분리와 근년의 PPNG의 비율을 검토하였고 최근 분리된 임균의 항균제 감수성을 한천 희석법으로 시험하여 다음과 같은 결과를 얻었다. 1. 이 기간에 한국인 여자환자의 생식기 검체의 4.8%(340명)와 눈 검체의 3.3%(43명)에서 임균이 분리되었다. 분리수는 1975년에 가장 많았고 그 이후 약간의 감소 경향을 보였다. 2. 남자 생식기에서는 20대가 60.6%, 여자는 30대가 40.3%, 눈 검체에서는 1/12세 미만에서 69.8%가 분리되었다. 3. 한국인 환자에서의 최초의 PPNG는 1979년에 분리되었고 1983년에는 그 비율이 38.6%에 달하였으며 1984년에는 19.5%이었다. 4. Penicillin G의 MIC는 non-PPNG에 대해 2㎍/ml 이하였으나 PPNG에 대해서는 4㎍/ml 이상이었다. β-lactamase 생성에 관계없이 spectinomycin의 MIC는 32㎍/ml 이하이고 cef operazone, cefotaxime, moxalactam의 MIC는 대단히 낮았다. 5. Non-PPNG는 13.6%가 penicillin G에, 75%가 tetracycline에 감수성이었고, PPNG는 81.3%가 tetracycline에 감수성이었다. Spectinomycin등 다른 모든 항균제는 시험균주 모두가 감수성이었다. 이 연구에서 임질이 드물지 않은 성병임에는 화가 없으며, 감염되었음을 모르는 임신부가 계속해서 있고, PPNG의 비율은 상당히 높으며, tetracycline 내성균주가 흔하다는 결론을 얻었다. [영문] Incidence of gonorrhea Is difficult to estimate in Korea. A gradual increase of the penicillin-resistant strains and the emergence of β-lactamase-producting strains(PPNG) became a serious problem in many parts of the world. In this study, an analysis was made on the isolation of Neisseria gonorrhoeae obtained at Yonsei Medical center from 1975 to 1984. The follwing results were obtained. 1. Among the female genital specimens of Korean, 4.8%(340 patients) yielded gonococci. The isolation rate from eye specimens was 3.3%(43 patients). The number of isolation was greatest in 1975 and thereafter it was slightly decreased. 2. The isolation rate was highest in genital specimens of 20-29 year old group tn male. while in female it was 30-39 year old group. Majority (69.8%) of the eye isolates came from infants aged less than one month old. 3. The first PPNG from Korean was isolated in 1979. The proportion reached 38.6% of all gonococci in 1983 and then slight decline to 19.5% was noted in 1984. 4. The MIC of penicillin G against non-PPHG was ≤ 2 ㎍/ml, while against PPNG it was ≥ 4 ㎍/ml. Regardless of the β-lactamase production, the MIC of spectinomycin was ≤ 32 ㎍/ml and those of cefoperazone, cefotaxime and moxalactam were all very low. 5. The prevalence of isolates susceptible to penicillin G was 13.6% of non-PPNG and to tetracycline 75% of non-PPNG and 81.3% of PPNG. All of the isolates tested were susceptible to spectinomycin and rest of antimicrobial agent. From this study it is concluded that gonorrhea remaines to be a relatively common serious infection in Korean, some pregnant women are not aware of their infections, and that PPNG is quite prevalent arid tetracycline resistant strains are very common.restrictio

Combination of sorafenib and sodium diethylthiocarbamate synergistically induce cell death in hepatitis B virus derived liver cancer via suppression of the PI3K/Akt/mTOR pathway

목적: 본 연구는 디설피람 유도체인 DDC (sodium diethyldithiocarbamate)를 소라페닙과 조합하여 B형간염 유래 간암세포에서의 항암 작용 가능성을 확인하고자 하였다. 대상 및 방법: 간암 조직과 세포주에서 실시간 폴리머아제 연쇄반응(qRT-PCR)과 면역블롯팅(immunoblotting)을 사용하여 초과산화이온1 (SOD1)과 B형간염 바이러스 단백질(HBx)의 발현 수준을 확인하였다. B형간염 양성 간암세포와 B형간염 음성 간암 세포에서 PI3K/Akt/mTOR 경로를 비교하였다. 소라페닙과 DDC 조합요법에서 세포 생존율, 활성산소 수준 및 세포자멸사 지표들을 평가했고, 소라페닙과 DDC 의 경구 공급과 관련하여 이종이식 생체 내 실험을 수행하였다. 결과: 환자 조직 검체와 B형간염 양성 세포에서 HBx와 SOD1의 발현이 증가되어 있었으며 둘 사이에 유의한 상관관계가 있었다. DDC 치료는 HepG2.2.15 세포에서 SOD1과 HBx의 발현을 효과적으로 감소시켰다. DDC와 소라페닙의 조합요법은 HBx의 발현을 감소시켰다. 소라페닙은 B형간염 양성 세포에서 PI3K/Akt/mTOR 경로를 억제하였으며, 이는 DDC에 의해 더 강화되어 암세포 생존율을 감소시켰다. 그러나 세포자멸사 지표들의 유의한 증가를 보이지는 않았다. 이종이식 생체 내 실험에서 소라페닙과 DDC 조합요법의 경구 투약은 종양의 성장을 억제하였다. 결론: DDC와 소라페닙의 조합요법은 B형간염 유래 간암세포에서 SOD1과 PI3K/Akt/mTOR 경로에 효과적으로 작용한다. 이 조합요법은 SOD1의 발현을 감소시키고, 산화 스트레스를 유도하며, 세포 생존율을 억제함으로써 B형간염 유래 간암세포의 치료에 효과적인 전략이 될 수 있다.|Background/Aims: This study explored the anti-cancer potential of combining sodium diethyldithiocarbamate (DDC), a disulfiram derivative, with sorafenib in HBV-positive liver cancer cells. Methods: We assessed the expression levels of SOD1 and HBx using qRT-PCR and immunoblotting in liver cancer samples and cell lines. The PI3K/Akt/mTOR pathway was compared between HBV-positive and HBV-negative liver cancer cells. Cell viability, levels of reactive oxygen species, and apoptotic markers were examined in response to sorafenib and DDC combination treatment. Furthermore, we conducted an in vivo xenograft experiment involving oral gavage of sorafenib and DDC. Results: Patient tissue samples and cells that were positive for HBV showed increased expressions of HBx and SOD1, with a significant correlation between the two. DDC treatment effectively reduced the expression of SOD1 and HBx in HepG2.2.15 cells. When combined, DDC and sorafenib synergistically decreased the expression of HBx. Sorafenib inhibited the PI3K/Akt/mTOR pathway in HBV-positive cells, and this inhibition was further enhanced by DDC, leading to decrease in cancer cell viability. However, the apoptotic markers did not show a significant increase. In an in vivo xenograft model, the combined oral administration of sorafenib and DDC synergistically inhibited tumor growth. Conclusions: The combination of DDC and sorafenib effectively targets SOD1 and the PI3K/Akt/mTOR pathway in HBV-positive liver cancers. By reducing SOD1 expression, inducing oxidative stress, and suppressing cell viability, this combination therapy presents a promising strategy for the treatment of HBV-related liver cancers.Docto

A Study on the Joining of TiA1 Intermetallic Compound by Brazing

본 연구에서는 Al을 삽입금속으로 사용하여 브레이징법으로 접합한 TiAl 금속간화홥물의 접합특성에 대하여 조사하였다. 삽입금속인 Al과 모재인 TiAl과의 반응에 의해 접합계면에서는 반응생성층으로서 경도가 모재보다 높고 취약한 TiAl₃가 형성되었으며, 접합온도가 600℃로 낮았거나 가열속도가 30K/min으로 너무 빠를 경우에는 반응생성층내에 void와 미소균열과 같은 접합결함이 존재하였다. 이와 같은 접합결함들은 700℃보다 높은 온도에서 접합하거나 가열속도를 10K/min보다 낮게 하여 접합한 경우에는 나타나지 않았다. 한편 접합체의 기계적 성질의 향상을 위하여 접합 후 Ar가스 분위기에서 열처리를 행한결과, 1300℃에서 3시간 동안 열처리를 했을 경우 모재와의 조성의 균일화가 완전히 이루어지지 않았으며 또한 반응생성층의 형태도 변화가 없었다. 그러나 1350℃에서 3시간 동안 열처리한 결과 조성의 균일화와 함께 반응생성층은 ??단상으로 변하였으며, 반응생성층의 미소경도는 층상조직인 모재의 미소경도보다 조금 낮게 나타났다.In this study, Joining properties of TiAl intermetallic compound bonded by brazing method using an insert metal of Al foil were investigated. A brittle reaction product layer. TiAl₃was formed at the joining interface and its microhardness was very higher than that of base metal. When the specimen was bonded at low temperature of 600℃ or with high heating rate of 30K/min respectively, joining defects like void and micro-crack were formed in the in the inside of reaction layer. These joining defects were disapeared when the speciment had been bonded at higher temperature than 700℃ or with lower heating rate than 10K/min. For the purpose of improving the mechanical properties of joints, effects of the post-bond heat treatment in Ar gas atmosphere on microstructure and hardness distribution of the bonded speciment were studied. When the joint was geat-treated at 1300℃ for 3 hr, homogenization of the compositions in the joining interface region was not achieved completely and morpholgy of the reaction product layer was still remained without morphological change. However, when the joint was heat-treated at 1350℃ for 3 hr, homogenization of the compositions in the joining interface region was achieved and the reaction product layer changed to γ single phase. And micro-vickers hardness of reaction layer region was slightly lower than that of base metal.In this study, Joining properties of TiAl intermetallic compound bonded by brazing method using an insert metal of Al foil were investigated. A brittle reaction product layer. TiAl₃was formed at the joining interface and its microhardness was very higher than that of base metal. When the specimen was bonded at low temperature of 600℃ or with high heating rate of 30K/min respectively, joining defects like void and micro-crack were formed in the in the inside of reaction layer. These joining defects were disapeared when the speciment had been bonded at higher temperature than 700℃ or with lower heating rate than 10K/min. For the purpose of improving the mechanical properties of joints, effects of the post-bond heat treatment in Ar gas atmosphere on microstructure and hardness distribution of the bonded speciment were studied. When the joint was geat-treated at 1300℃ for 3 hr, homogenization of the compositions in the joining interface region was not achieved completely and morpholgy of the reaction product layer was still remained without morphological change. However, when the joint was heat-treated at 1350℃ for 3 hr, homogenization of the compositions in the joining interface region was achieved and the reaction product layer changed to γ single phase. And micro-vickers hardness of reaction layer region was slightly lower than that of base metal

Effects of sirolimus in the treatment of unresectable infantile hemangioma and vascular malformations in children: A single-center experience

Objective: Recently, sirolimus has emerged as a safe and effective treatment modality for unresectable vascular lesions. In the present study, we investigated the effectiveness and safety of sirolimus from our early experience with patients with unresectable vascular anomalies. Methods: The medical records and radiologic images of all patients with unresectable vascular anomalies treated with sirolimus at our center from January 2018 to November 2019 were retrospectively reviewed. All patients were administered oral doses of sirolimus 0.8 mg/m(2) every 12 hours as the initial dose, followed by maintenance of a target serum concentration (5-10 ng/mL) with therapeutic drug monitoring. Results: Six patients with unresectable vascular anomalies were treated with sirolimus for >= 10 months. Their median age at the initiation of sirolimus treatment was 17 months (range, 8-67 months). The median duration of treatment was 13 months (range, 10-16 months). One patient had a good response, four had an intermediate response, and one had no response to sirolimus therapy. None of the patients had discontinued sirolimus therapy because of adverse effects. Conclusions: Sirolimus can be used effectively and safely for patients with unresectable vascular anomalies. However, further prospective studies are warranted to evaluate the long-term effects of sirolimus and clarify the indications for early intervention

Efficacy and safety of autologous adipose tissue-derived stem cell therapy for children with refractory Crohn's complex fistula: a Phase IV clinical study

Purpose: Autologous adipose tissue-derived stem cells (ASCs) have been proposed for patients with refractory Crohn disease, but research is lacking in pediatric patients. This Phase IV study evaluated the efficacy and safety of ASCs in children with refractory Crohn's fistulae. Methods: Patients with a refractory Crohn's fistula who did not have conventional therapy for more than 3 months or with a recurrent complex Crohn's fistula were included. All patients were at least 14 years old. Patients with infection, poor condition, or active Crohn disease with a disease activity index of 450 and above were excluded. Five patients were treated with ASCs from 2014 to 2015 in Asan Medical Center. ASC administration was adjusted according to fistula size (1 mL per cm(2)). We evaluated the efficacy and safety 8 weeks after injection and followed patients for 6 months. Results: Fistulae were healed in 4 patients by 8 weeks after ASC injection. Of these 4 patients, 1 had complete fistula closure and sustainability after 6 months. The other 3 with healing effects had less than 50% fistula closure by 6 months. None of these 4 patients have persistent fistulae. One patient had no healing effect, and seton ligation was performed 8 months after ASC injection. There were no adverse effects related to ASC administration. Conclusion: ASC therapy is a simple and well-tolerated therapeutic option for children with refractory Crohn's complex fistulae. Complete closure was well-sustained. However, more data from a larger number of patients are needed

Effect of Vanadium and Boron on Microstructure and Low Temperature Impact Toughness of Bainitic Steels

In this study, three kinds of bainitic steels are fabricated by controlling the contents of vanadium and boron. High vanadium steel has a lot of carbides and nitrides, and so, during the cooling process, acicular ferrite is well formed. Carbides and nitrides develop fine grains by inhibiting grain growth. As a result, the low temperature Charpy absorbed energy of high vanadium steel is higher than that of low vanadium steel. In boron added steel, boron segregates at the prior austenite grain boundary, so that acicular ferrite formation occurs well during the cooling process. However, the granular bainite packet size of the boron added steel is larger than that of high vanadium steel because boron cannot effectively suppress grain growth. Therefore, the low temperature Charpy absorbed energy of the boron added steel is lower than that of the low vanadium steel. HAZ (heat affected zone) microstructure formation affects not only vanadium and boron but also the prior austenite grain size. In the HAZ specimen having large prior austenite grain size, acicular ferrite is formed inside the austenite, and granular bainite, bainitic ferrite, and martensite are also formed in a complex, resulting in a mixed acicular ferrite region with a high volume fraction. On the other hand, in the HAZ specimen having small prior austenite grain size, the volume fraction of the mixed acicular ferrite region is low because granular bainite and bainitic ferrite are coarse due to the large number of prior austenite grain boundaries

베이나이트계 후판의 HAZ 미세조직과 저온 충격 인성의 상관관계

In this study, the correlation between HAZ microstructure and low temperature impact toughness of bainitic steel plates was investigated. The Steel with high carbon content and finish cooling temperature has a higher volume fraction and large packet size of granular bainite compared to the steel with low carbon content and finish cooling temperature. The room temperature tensile properties of the two steels are similar, mostly because the microstructure is composed of acicular ferrite having fine grains. On the other hand, the low temperature Charpy absorbed energy of two steels showed a big difference. As the test temperature decreased, the Charpy absorbed energy of the steel with high carbon content and finish cooling temperature decreased more rapidly than the steel with low carbon content and finish cooling temperature. This is due to the high volume fraction of granular bainite and large packet size of granular bainite in the steel with high content and finish cooling temperature. HAZ specimens have a very complex microstructure with a mixture of acicular ferrite, granular bainite, and bainitic ferrite through the rapid cooling process. In the HAZ specimen with high carbon content, more volume fraction of granular bainite + bainitic ferrite was formed, and the packet size of granular bainite + bainitic ferrite was also coarse. Because of this result, the HAZ speci?men with high carbon content has low Charpy absorbed energy compared to the HAZ specimen with low carbon content