Study on Microstructure and Mechanical Properties of the Al–25Cr–5Si (at%) Alloy Powder Using Gas-Atomization and SPS Process

Yong‑Ho Kim,Hyo‑Sang Yoo,Jeong‑Han Lee,Ik‑Hyun Oh,Hyun‑Kuk Park,Hyeon‑Taek Son 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In order to investigate the microstructure and mechanical properties on Al–25Cr–5Si (at%) alloy, a mixed powder with pureelements and an alloy powder using a gas atomization process were used. Fine and high purity Al–25Cr–5Si (at%) alloypowder was successfully prepared by gas atomization and densified using a spark plasma sintering (SPS) process. The overallpowder size distribution of the mixed Al, Cr, and Si elemental powders was in the range of 10–15 μm. The atomized Al–Cr–Sialloy powder was fine and spherical in morphology and difficult to be formed by intermetallic formation. Densification wasclearly confirmed at 1000 °C, with almost isolated pores formed, by clear removal of pores between particles, deformationof particles, an increase in the number of contacts, and a change in size between particles. As a result of XRD analysis ofthe sintered compacts, single phase was observed using the mixed powder, but the compact using gas atomization remainedthe alloy phase even at the process temperature. The Vickers hardness of the compacts by mixed powder was observed at59.70 Hv and the compact using gas atomized powders on the temperature 1000 °C of the Vickers hardness increased to702.6 Hv. The compressive yield strength of the compact with mixed powder was 195.24 MPa and the compressive strengthof the compact with gas atomized powder increased to 802.07 MPa. It is considered not to be decomposed by the AlCrSi,Al13Cr4Si4and Al8Cr5phases sintering process, resulting from the improvement of mechanical properties.

Prevalence of Chronic Obstructive Pulmonary Disease in Korea: The Result of Forth Korean National Health and Nutrition Examination Survey

( Yong Il Hwang ),( Kwang Ha Yoo ),( Seung Soo Sheen ),( Joo Hun Park ),( Sang-Ha Kim ),( Ho Il Yoon ),( Sung Chul Lim ),( Shin Yup Lee ),( Jae Yong Park ),( Seoung Ju Park ),( Ki Hyun Seo ),( Ki Uk K 대한결핵 및 호흡기학회 2011 Tuberculosis and Respiratory Diseases Vol.71 No.5

Background: Chronic obstructive pulmonary disease (COPD) is a major cause of chronic morbidity and mortality throughout the world and is the only major disease that is continuing to increase in both prevalence and mortality. The second Korean National Health and Nutrition Survey revealed that the prevalence of COPD in Korean subjects aged ≥45 years was 17.2% in 2001. Further surveys on the prevalence of COPD were not available until 2007. Here, we report the prevalence of spirometrically detected COPD in Korea, using data from the fourth Korean National Health and Nutrition Survey (KNHANES IV) which was conducted in 2007∼2009. Methods: Based on the Korean Statistical Office census that used nationwide stratified random sampling, 10,523 subjects aged ≥40 years underwent spirometry. Place of residence, levels of education, income, and smoking status, as well as other results from a COPD survey questionnaire were also assessed. Results: The prevalence of COPD (defined as forced expiratory volume in 1 sec/forced vital capacity <0.7 in subjects aged ≥40 years) was 12.9% (men, 18.7%; women, 7.5%). In total, 96.5% of patients with COPD had mild-to-moderate disease; only 2.5% had been diagnosed by physicians, and only 1.7% had been treated. The independent risk factors for COPD were smoking, advanced age, and male gender. Conclusion: The prevalence of COPD was 12.9% in the KNHANES IV data. Most patients with COPD were undiagnosed and untreated. Based on these results, a strategy for early COPD intervention is warranted in high risk subjects.

Synthesis and Characterization of the Temperature/pH-Sensitive Polymers for Drug Delivery Systems

Yoo, Mi-Kyong,Sung, Yong-Kiel 동국대학교 자연과학연구원 2000 자연과학연구 논문집 Vol.5 No.-

The stimuli-sensitive polymers were synthesized by copolymerizing varying ratios of N-isopropyl acrylamide(NIPAAm) and acrylic acid(AAc). The influence of polyelectrolytes on the lower critical solution temperatures(LCSTs) of these temperature/pH sensitive polymers was investigated in the pH range of 2∼12. The polyelectrolyte complexes were prepared by mixing poly(NIPAAm-co-AAc) as anionic polyelectrolyte with poly(allyl amine)(PAA) or poly(L-lysine)(PLL) as cationic polyelectrolytes, respectively. The effect of polyelectrolyte complex formation on the conformation of PLL was studied as a function of temperature by means of circular dichroism(CD). Swelling ratio of poly(NIPAAm-co-AAc) hydrogels as a function of pH at various temperature was obtained by measuring the weight of the hydrogels in buffer solutions. The LCSTs of the poly(NIPAAm-co-AAc) were strongly affected by pH, polyelectrolyte solutes, AAc content, and charge density. The influence of more hydrophobic PLL as a polyelectrolyte on the cloud point of PNIPAAm/water in the copolymer was stronger than that of poly(allyl amine)(PAA). Indomethacin was loaded into these hydrogels and their drug release characteristics were determined under various temperature and pH conditions using UV/Vis spectrophotometer.

Effect of Curcuma longa Hot Water Extract on Activity of Neuronal Cells Related to Oxidative Stress

Yong-Byung Chae(채용병),Kyung Tae Chung(정경태),Sung-Goo Kim(김성구),Byung-Hong Yoo(유병홍),Moon-Moo Kim(김문무) 한국생명과학회 2012 생명과학회지 Vol.22 No.5

본 연구의 목적은 인지기능을 가진 약효제를 발굴하는 것이다. 본 연구에서는 토끼의 간과 신경세포로부터 각각 유래한 angiotension converting enzyme과 acetylcholinesterase에 대한 강황 열수추출물(CLWE)의 억제효과뿐만 아니라 항산화 효과가 조사되었다. 이리하여 먼저 산화적 스트레스와 연관이 있는 환원력과 DPPH radical, superoxide anion, hydroxyl radical, lipid peroxidation에 대한 CLEW의 소거능 및 DNA 산화에 대한 보호효과를 평가하였다. CLEW는 환원력 뿐만 아니라 본 연구에서 시험된 활성산소종 중에서 특히 superoxide anion의 소거능이 가장 우수한 것으로 나타났다. 더욱이 CLEW는 0.25% 이상의 농도에서 angiotensin converting enzyme 활성을 억제효과를 발휘하는 것으로 나타났다. 신경세포에서 CLEW는 또한 산화적 스트레스와 nitric oxide 유발을 억제하였다. 그러므로 이상의 결과는 CLEW의 항산화 효과와 신경세포 보호효과를 입증하여, 이것이 사람의 신경건강을 위한 천연생물소재로 잠재적인 가능성을 가지고 있을 것으로 시사한다. The aim of this study is to screen a therapeutic agent with a cognitive function. The inhibitory effect of Curcuma longa hot water extract (CLWE) on the angiotension-converting enzyme and acetylcholinesterase derived from rabbit lungs and neural cells (PC12), as well as its antioxidant effect, was investigated in this study. Thus, for the first time, the direct scavenging effect of CLWE on DPPH radicals, superoxide anions, hydroxyl radicals, lipid peroxidation, reducing power, and the protective effect of DNA oxidation related to oxidative stress was evaluated in vitro. In addition, it was observed that CLWE especially exhibited a scavenging effect on reducing power and superoxide anions in this study. CLWE showed a protective effect on DNA oxidation produced by hydroxyl radicals. Furthermore, CLWE inhibited the activity of angiotensin-converting enzymes above 0.25%. Additionally, the extract inhibited oxidative stress and inducible nitric oxide in neuronal cells. Therefore, these results demonstrated that CLWE has antioxidant activity and neuronal cell protective effects, suggesting that it may have great potential as a natural source for human health.

Value of pelvic examination and imaging modality for the evaluation of tumor size on cervical cancer

Yoo-Kyung Lee,Seung-Su Han,Jae Weon Kim,Noh-Hyun Park,Yong-Sang Song,Soon-Beom Kang 대한부인종양학회 2008 Journal of Gynecologic Oncology Vol.19 No.2

Objective: The purpose of this study was to compare the accuracy of pelvic examination versus imaging modality such as computed tomography (CT) or magnetic resonance imaging (MRI) in the measurement of the tumor size of invasive cervical carcinoma based on pathologic findings. Methods: Patients with stage Ib-II cervical cancer who underwent primary surgical treatment between January 2003 and December 2005 were evaluated retrospectively. One hundred three consecutive patients aged 24 to 81 years (mean age, 50.6 years), who had not received any treatment previously were included in this study. Accuracy of preoperative CT or MRI versus pelvic examination in the measurement of tumor size was compared based on pathologic findings. All patients were examined and staged clinically by the gynecologic oncologist. Surgery was performed within 2 weeks after imaging studies. The data were analyzed using descriptive statistics. Results: The largest diameter of the tumor measured by pathologic findings was 2.76±1.76 cm. Based on pathologic findings, accuracy was estimated by the degree of agreement with a difference of <0.5 or 1.0 cm between the measurements of tumor size obtained by pelvic examination and imaging modality. Pelvic examination and imaging modality had an accuracy of 46.6% and 39.8%, respectively, with a difference of <0.5 cm, and an accuracy of 72.8% and 55.3%, respectively, with a difference of <1.0 cm. Correlation with pathologic findings was higher for pelvic examination (rs=0.680) than for imaging modality (rs=0.410). In determining the size of tumor mass differentiating >4.0 cm from ≤4.0 cm, imaging modality showed higher accuracy than pelvic examination. Conclusion: For the patients with stage Ib to II cervical cancer, pelvic examination is superior to imaging modality with regard to evaluation of the tumor size. However, imaging modality may be accurate for evaluating bulky tumors of cervical cancer. Objective: The purpose of this study was to compare the accuracy of pelvic examination versus imaging modality such as computed tomography (CT) or magnetic resonance imaging (MRI) in the measurement of the tumor size of invasive cervical carcinoma based on pathologic findings. Methods: Patients with stage Ib-II cervical cancer who underwent primary surgical treatment between January 2003 and December 2005 were evaluated retrospectively. One hundred three consecutive patients aged 24 to 81 years (mean age, 50.6 years), who had not received any treatment previously were included in this study. Accuracy of preoperative CT or MRI versus pelvic examination in the measurement of tumor size was compared based on pathologic findings. All patients were examined and staged clinically by the gynecologic oncologist. Surgery was performed within 2 weeks after imaging studies. The data were analyzed using descriptive statistics. Results: The largest diameter of the tumor measured by pathologic findings was 2.76±1.76 cm. Based on pathologic findings, accuracy was estimated by the degree of agreement with a difference of <0.5 or 1.0 cm between the measurements of tumor size obtained by pelvic examination and imaging modality. Pelvic examination and imaging modality had an accuracy of 46.6% and 39.8%, respectively, with a difference of <0.5 cm, and an accuracy of 72.8% and 55.3%, respectively, with a difference of <1.0 cm. Correlation with pathologic findings was higher for pelvic examination (rs=0.680) than for imaging modality (rs=0.410). In determining the size of tumor mass differentiating >4.0 cm from ≤4.0 cm, imaging modality showed higher accuracy than pelvic examination. Conclusion: For the patients with stage Ib to II cervical cancer, pelvic examination is superior to imaging modality with regard to evaluation of the tumor size. However, imaging modality may be accurate for evaluating bulky tumors of cervical cancer.

Synergistic effects of N-acetylcysteine and Retinoic acid on Dopaminergic Neuronal Differentiation of P19 EC stem cell via PI3-kinase pathway

Yoo Hun Noh,Do Yeon Lee,Jang Il Kim,Ji Young Yun,Do Hee Kim,Yong Min Kim,Yoon Hee Jung,Kyung Yong Kim,Sung Su Kim,Won Bok Lee 대한체질인류학회 2006 대한체질인류학회 학술대회 연제 초록 Vol.49 No.-

Effect of Hydrophobicity on Polymer Complex for the Cloud-point of PNIAAm Copolymers

SUNG, YONG-KIEL,YOO, Mi-KYONG 동국대학교 자연과학연구원 1996 자연과학연구 논문집 Vol.1 No.-

Random copolymers of acrylic acid(AAc) and N-isopropylacrylamide(NIPAAm) were synthesized by free-radical polymerization. The copolymers were characterized for their temperature- and pH-responsive behavior by cloud-point experiment. The influence of polyelectrolyte on the lower critical solution temperature(LCST) of pH/temperature sensitive polymer was investigated in the range of pH 2-12. A polyelectrolyte complex was prepared by mixing poly(NIPAAm-co-AAc) and poly(L-lysine)(PLL) solutions as anionic and cationic polyelectrolytes, respectively. The influence of PLL on the cloud-point of PNIPAAm was more stronger than that of poly(allyl amine)(PAA). One plausible explanation of the result is that as the side chain length increases from C1 for PAA to C4 for PLL, the hydrophobicity of polyelectolyte complex increases, indicating that more stronger dehydration occurs around PNIPAAm. The LCSTs PNIPAAm in poly(NIPAAm-co-AAc) were strongly affected by the pH and type of polyelectrolyte solutes.

Interaction between Poly(L-lysine) and Poly(N-isopropyl acrylamide-co-acrylic acid) in Aqueous Solution

Sung, Yong-Kiel,Yoo, Mi-Kyong,Cho, Chong-Su The Polymer Society of Korea 2000 Korea polymer journal Vol.8 No.1

A series of pH/temperature sensitive polymers were synthesized by copolymerizing N-isopro-pyl acrylamide(NIPAAm) and acrylic acid(AAc) . The influence of polyelectrolyte between poly(allyl amine) (PAA) and poly(L-lysine)(PLL) on the lower critical solution temperature(LCST) of pH/temperature sensitive polymer was compared in the range of pH 2∼12. The LCST of PNIPAAm/water in aqueous poly(NIPAAm-co-AAc) solution was determined by cloud point measurements. A polyelectrolyte complex was prepared by mixing poly(NIPAAm-co-AAc) with poly(allyl amine) (PAA) or poly(L-lysine) (PLL) solutions as anionic and cationic polyelectrolytes, respectively. The effect of polyelectrolyte complex formation on the conformation of PLL was studied as a function of temperature by means of circular dichroism(CD). The cloud points of PNIPAAm in the aqueous copolymers solutions were stongly affected by pH, the presence of polyelectrolyte solute, AAc content, and charge density. The polyelectrolyte complex was formed at neutral condition. The influence of more hydrophobic PLL as a polyelectrolyte on the cloud point of PNIPAAm in the aqueous copolymer solution was stronger than that of poly(allyl amine)(PAA). Although polymer-polymer complex was formed between poly(NIPAAm-co-AAc) and PLL, the conformational change of PLL did not occur due to steric hinderance of bulky N-isopropyl groups of PNIPAAm.

Neonatal Sepsis and Meningitis Caused by Neisseria meningitidis Serogroup B: a Case Report

Yoo Na Kim,Yong-Sung Choi,차성호 대한소아감염학회 2018 Pediatric Infection and Vaccine Vol.25 No.3

Sepsis and meningitis caused by Neisseria meningitidis are rare in neonates, but neonatal sepsis and meningitis are associated with a high rate of mortality. Meningococcal disease is commonly reported in older children and adolescents and is known to be more prevalent in community settings. In this study, a 16-day-old neonate was diagnosed with serogroup B meningococcal sepsis and meningitis. The baby was treated with antibiotics at the early stages of the infection and was discharged in good condition without any complications. This case report can serve to raise awareness of the incidence and importance of meningococcal infection in neonates, especially serogroup B.

A Study on Maritime Traffic Characteristics according to Water Time(Multte)

Sang-Lok Yoo,Cho-Young Jeong,Jae-Yong Jeong 해양환경안전학회 2015 해양환경안전학회지 Vol.21 No.5

본 연구는 물때에 따른 교통특성을 분석하여 선박통항관리 개발에 필요한 자료를 제공하고자 한다. 목포항의 1년간 선박자동식별장치 자료를 사용하였다. 물때에 따른 교통량을 분석하기 위해 목포항의 1년간의 선박자동식별장치의 양력 데이터를 음력으로 변환한 후, 서해안의 구전 물때를 적용하였다. 연구 결과, 출항선박은 2-3물때 교통량이 7물때 보다 약 23-24% 많고, 입항선박은 12-13물때 교통량이 9물때 보다 약 29-33 % 많았다. 특히, 시간의 변화에 따른 물때별 변동지수는 sine 함수의 형태로 변화하였다. 본 연구는 물때에 따른 선박통항관리 개발에 필요한 기초자료로 활용될 수 있을 것으로 판단된다. This study seeks to analyze ships traffic characteristics according to water time in order to provide the necessary data for efficient traffic management development. To analyze maritime traffic volume according to water time, 1 year amount of solar calendar data were converted into lunar calendar, and then applied the traditional water time system of West Sea by using AIS(Automatic Identification System) observation data gathered in Mokpo port for a year of 2013. As a result, it was found herein that the number of outbound ships was larger on the 2nd-3rd water times than the 7th water times by 23-24 %. And the number of inbound ships was higher on the 12th-13th water times than the 9th water time by 29-33 %. The hourly variation index of inbound and outbound ships according to time, in particular, was found to change in the form of sine function model. This study is expected to serve as a necessary basic material for development of maritime traffic management according to water time.