Easy Preparation of Readily Self-Assembled High-Performance Graphene Oxide Fibers

Kim, Yern Seung,Kang, Jong Hun,Kim, Taehoon,Jung, Yeonsu,Lee, Kunsil,Oh, Jun Young,Park, Jisoo,Park, Chong Rae American Chemical Society 2014 Chemistry of materials Vol.26 No.19

<P>Graphene oxide (GO) was recently reported to assemble into one-dimensional fiber precursors that can be used to produce next-generation multifunctional graphene-based materials. This study describes the facile fabrication of GO fibers with excellent mechanical properties, utilizing a diamine cross-linker that forms ion bridges between the GO layers. Organic co-coagulants and postdrawing processes, which are usually employed in typical GO spinning processes, were not used here. The GO layers readily aligned along the spinning axis, and the GO formed closely packed structures in the fibers. The fibers displayed a Young’s modulus of 26.6 GPa and a maximal tensile strength of 384.3 MPa. The interlayer microstructure of the GO sheets could be tuned by modifying the structures of the cross-linking diamine groups, yielding a range of mechanical properties. These observations suggested that our newly developed GO fiber synthesis method could allow applications of graphene-based fibrous materials through GO surface chemistry modification approaches.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2014/cmatex.2014.26.issue-19/cm502614w/production/images/medium/cm-2014-02614w_0008.gif'></P>

탄소나노튜브 캐소드의 전계방출 및 열화특성에 미치는 페이스트의 조성과 분위기 가스의 영향

김동희,김태식,정원섭,김광호,손영국,조영래 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.3

서울의 Penicillinase Producing Neisseria gonorrhoeae 발생빈도(1998)

김재홍,김준호,반재용,이정우,황성주,정준규,정성태,강진문,조흔정,홍창의,정혜신,이한승,김이선,이봉길,이종호,선영우,한기덕,윤성필,이성훈,안종성,박석범,문승현,조항래,김형섭,류지호,황재영,박준홍,손상욱 한양대학교 의과대학 2001 한양의대 학술지 Vol.21 No.1

In recent years, gonorrhea has been pandemic and remains one of the most common STDs in the world, especially in developing countries. For the detection of a more effective therapeutic regimen and assessing the prevalence of Penicillinase Producing Neisseria gonorrhoeae(PPNG), we have been trying to study the patients who have visited the Venereal Disease Clinic of Choong-Ku Public Health Center in Seoul since 1980 by menas of the chromogenic cephalosporin method. In 1998, 93 strians of N. genorrhoeae were isolated, among which 60(64.5%) were PPNG. The prevalence of PPNG in Seoul, which had been decreased to 39% in 1996 after a peak of 74.3% in 1993, is increased to 64.5% in 1998.

Crucial Role of Oxidation Debris of Carbon Nanotubes in Subsequent End-Use Applications of Carbon Nanotubes

Kim, Yern Seung,Oh, Jun Young,Kim, Jae Ho,Shin, Min Ho,Jeong, Yo Chan,Sung, Sae Jin,Park, Jisoo,Yang, Seung Jae,Park, Chong Rae American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.20

<P>A facile purification method for oxidized carbon nanotubes (CNTs) is developed to preserve acidic carbon compounds (ACCs) for achieving high-quality dispersion of CNTs. The remaining ACCs, which originated from the surface destruction of CNTs during the oxidation process, are considered to play a crucial role in the dispersion of CNTs in water and various polar protic solvents. To elucidate the concrete role of ACCs, a direct titration method is applied to quantitatively investigate the degree of ionization of both CNTs and ACCs in their aqueous dispersion. While ACCs with strong carboxylic groups (pK(a) of around 2.9) are easily removed by the neutral or base washing of oxidized CNTs, which is common in the purification process, ACC-selective purification using acid washing preserves the ACCs attached to CNTs, thereby effectively stabilizing CNT dispersions in aqueous solutions. Additionally, the Hansen solubility parameters of ACC-preserved and ACC-removed CNTs were determined by the inverse gas chromatography method to estimate their miscibility in various solvents. The preserved ACCs significantly influenced the dispersibility of CNTs in polar protic solvents, which may widen the possible application of CNTs. Specifically, the ACC-preserved high-quality CNT dispersion produces high-performance CNT buckypaper with densely packed nanostructures. The Young's modulus and tensile strength of these buckypapers reach up to 12.0 and 91.0 MPa, respectively, which exceed those of ACC-removed CNTs in previous reports.</P>

조세회피와 발생액에 의한 이익조정이 회사채 신용등급에 미치는 영향

조영래(Cho, Young-Rae),김용(Kim, Yong) 한국산업비즈니스학회 2021 한국비즈니스연구 (비즈니스연구) Vol.5 No.1

본 연구에서는 2011년부터 2015년까지 유가증권시장에 상장된 기업들을 대상으로 신용등급이 상승하거나 또는 하락할 경우에 조세회피 및 발생액에 의한 이익조정이 회사채 신용등급에 어떠한 영향을 미치는 지를 분석하였다. 추가로 조세회피 및 이익조정의 지속성이 신용등급에 어떤 영향을 미치는지에 대해서도 분석하였다. 분석결과는 신용등급이 상승하는 경우에 조세회피가 1% 수준에서 유의적인 음(-)의 관계를 나타내었으며, 조세회피와 신용등급 상승의 상호작용변수는 유의적인 양(+)의 관계를 나타내었다. 이는 조세회피가 직전년도와 비교하여 신용등급이 상승하였을 때는 조세회피를 하려는 경향이 감소하기 때문이며, 또한 신용평가기관에서 신용등급이 상승할 때 조세회피는 감소할 것이라고 예측하여 보고된 이익을 그대로 반영하였기 때문이라고 판단된다. 그러나 신용등급이 하락하는 경우에는 이와 정반대의 결과를 도출하였다. 그러나 발생액에 의한 이익조정은 신용등급과 유의적인 관계를 나타내지 못하였다. 추가로 지속성이 회사채 신용등급에 영향을 미치는지를 검증하였는데, OLS회귀분석과 순서형 로짓회귀분석 모두 일부 이익조정(수정 Jones모형)의 경우 5% 수준에서 유의적인 음(-)의 관계를 나타내었다. 따라서 이익조정의 지속성은 신용등급에 부정적인 영향을 미친다고 볼 수 있다. 다만, 이들 관계는 측정치에 따라 차이가 나타나고 있다. 이러한 분석결과는 신용평가기관이 조세회피를 제대로 포착하지 못함으로써 신용위험을 왜곡시키고 나아가 신용등급에 대한 신뢰성을 떨어뜨릴 수 있다는 점을 시사하는 것으로 판단된다. This study empirically analyzed how tax avoidance affects bond credit ratings of listed companies on the korea exchange from 2011 to 2015. The results of this study are summarized as follows. First, the relationship between tax avoidance, earnings management and bond credit ratings was not statistically significant in all models. But In the case of a rise in bond credit rating, the relationship between the five years of accumulated cash effective tax rate(cashETR) were showed a significant negative(-) relationship at a 1% level. Also, if the bond credit rating declines, the results is the opposite of the case where the bond credit rating rises. Second, in determining whether continuous tax avoidance affects bond credit rating ratings, either the OLS analysis, or ordered logistics regression analysis, showed a significant negative(-) relationships only in the Jones Model at a 5% level. Third, The interaction effect of the decline in credit rating and persistence showed a significant negative(-) relationship at 1% level in all three models. Thus, the persistence of the tax avoidance can be seen to affect bond credit rating when combined with other factors that can interact. The results of this study suggest that many companies still avoid tax, but credit rating agencies are not able to capture them properly, thus distorting credit risk and decreasing credibility of credit rating.

극단 저체중 신생아에서의 동맥관 개존증 결찰술을 위한 진정맥 마취 경험 2례

최영균,고명진,이상은,조광래,김영환,임세훈,이정한,이근무,정순호,김영재,신치만 仁濟大學校 白病院 2010 仁濟醫學 Vol.31 No.-

Running title: Cases of anesthesia for extremely low birth weight infant. Extremely low birth weight infants (birth weight < 1000 g) are prone to various morbidities such as respiratory distress syndrome, intraventricular hemorrhage, periventricular leukomalacia, patent ductus arteriosus, necrotizing enterocolitis and retinopathy. To accomplish successful anesthetic management, many precautions must be continuously taken during the operation. First, inspired oxygen concentration should be adjusted to avoid oxygen toxicity. Second, body temperature must be maintained adequately. Third, hemodynamic parameters should be kept stable. We report 2 cases of successful anesthetic management for extremely low birth weight infant who underwent ligation of patent ductus arteriosus at the neonatal intensive care unit.

Rocuronium의 애별투여방법이 모지내전근의 이완에 미치는 영향

최영균,김승수,이원진,조광래,이상은,김영환,임세훈,이정한,이근무,정순호,김영재,신치만 인제대학교 2009 仁濟醫學 Vol.30 No.-

Objective : There are controversies in pnmmg technique of rocuronium whether it can or can't shorten the onset time. We want to compare the effects of two different priming doses and intervals of rocuronium. Materials and Methods : After giving propofol, 50 patients were randomly assigned to 5 groups. Group I received a placebo, followed 3 min later by rocuronium 0.6 mg/kg. Priming doses and intervals of Group II, Ill, N, V were 0.06 rng/kg and 2 min, 0.12 mg/kg and 2 min, 0.06 rug/kg and 3 min, 0.12 mg/kg and 3 min, respectively. Total dose of rocuronium was 0.6mg/kg. Train of four (TOF) count or ratio and 1st twitch height of TOF (T1) were monitored with 15 secondsintervals. TOF ratio of each groups just before bolus injection, duration for TOF count to reach zero and duration for Tl to reach 95% depression after bolus injection were compared. Results : Duration for TOF count to reach zero and duration for Tl to reach 95% depression after bolus injection were decreased in priming groups compared to Group 1 (P < 0.01) In group V, significant depression of TOF ratio just before bolus injection was seen (P < 0.05). Conclusion : Priming technique with rocuronium is effective method to shorten the onset of neuromuscular block. But priming dose of rocuronium itself could cause hypoxia and aspiration in awake patients and should be used carefully. Priming dose of rocuronium 0.06 mg/kg and 2 minutes interval maybe relatively safe method.

성인의 장중첩증에서 복부전산화단층촬영술의 유용성

김세웅,조영업,고영배,김원곤,김경국,김경래,우제홍,김미영 대한대장항문학회 1998 Annals of Coloproctolgy Vol.14 No.3

일 대학병원에 입원한 노년기 양극성 장애 환자의 인구학적 및 임상적 특징

조숙현(Sook Hyun Cho),정한용(Han Yong Jung),권영준(Young Jun Kwon),이소영(So Young Lee),김양래(Yang Rae Kim),김윤정(Yun Jung Kim) 대한노인정신의학회 2006 노인정신의학 Vol.10 No.2

Objectives : As the elderly population is continuing to increase, psychiatric diseases of the elderly are becoming an important social issue. This study looks into the demographical and clinical features of the elderly patients diagnosed with bipolar disorder in a University hospital. Methods : The study subjects include patients admissioned in the closed wards of Soonchunhyang Seoul hospital and Cheonan hospital from March, 2000 to February, 2005 who met the DSM-IV-TR criteria for bipolar disorder at the time of discharge. A total of 146 patients (76 men, 70 women) medical records were studied retrospectively. Subjects older than the age of 50 at time of admission were grouped as the old age group, whereas those who were younger than 50 as the young age group. Also among the old age group, those who had the first onset of episode under the age of 50 were grouped as the early onset group, whereas those who had the first onset after the age 50 were grouped as the late onset group. Results : The number of bipolar disorder patients in the young age group and old age group were 73 and 73 respectively. The number of early onset group and late onset group were 46 and 23 respectively. The old age group had a relatively higher incidence of bipolar II disorder than the young age group. Also in the old age group there was a higher incidence of hypomanic or depressive episode rather than manic episode compared to the young age group. And in the old age group psychotic symptoms were less common and the mean admission length shorter than the young age group. Additionally in the old age group treatment with Lithium monotherapy or with no mood stabilizers at all were relatively common. Among the old age group, late onset group had a higher rate of bipolar II disorder than the early onset group. Conclusion : This study shows differences in the demographical and clinical features among different age groups. But additional research would be required to determine whether the bipolar disorders in the elderly or late onset group are actually a different type of disorder from those of the young.

당뇨병 환자에서 혈장 Thrombin-Antithrombin Ⅲ 및 Plasmin-α_2-Plasmin Inhibitor 복합체의 임상적 의의

김경욱,김은숙,정상수,윤수지,박우일,이준희,남수연,안철우,문병수,김경래,차봉수,송영득,임승길,이현철,허갑범 대한당뇨병학회 2002 Diabetes and Metabolism Journal Vol.25 No.5

연구배경:당뇨병 환자에서 혈액응고 및 섬유소용해 체계의 이상경향이 있어 그 결과로 여러 혈관합병증의 발생위험이 높다는 사실은 널리 알려져 있다. 그 기전은 아직 확실히 밝혀지지 않았으나, 고혈당으로 인한 혈장 단백질들의 비효소성 당화작용이나 산화성 스트레스로 인한 유리 라티칼 작용으로 응고항진이나 섬유소용해 활성의 저하를 유발하는 것으로 생각되고 있다. 최근 응고 및 용해인자와 그 억제자의 복합체들의 증가가 이 상태를 비교적 예민하게 반영한다고 알려져 있다. 방법:본 연구에서는 당뇨병 환자 101명과 정상 대조군 20명에서 혈장내 thrombin­antithrombin complex(TAT)와 plasmin­α₂­plasmin inhibitor complex(PIC)를 측정하여 비교하고, 당뇨병 환자에서 미세혈관 합병증과 대혈관합병증의 유무에 따른 차이와, 이미 혈관 질환의 위험인자로 알려져 있는 인자들간의 상관성을 알아보고자 하였다. 결과:1. 환자의 분포를 살펴보면 혈관합병증이 있는 군은 85명, 혈관합병증이 없는 군은 16명이었고, 평균연령은 각각 57.9±14.1세, 49.9±16.6세로 혈관 합병증이 있는 군에서 더 나이가 많았고, 체질량지수는 23.2±3.4㎏/㎡, 24.1±3.4㎏/㎡로 두 군간 유의한 차이는 없었다. 또 두 군간의 혈압 및 HbA1c, 공복혈당 및 인슐린과 C­peptide, 총 콜레스테롤, 중성지방, HDL­콜레스테롤, Lp⒜는 유의한 차이가 없었고, 미세혈관합병증이 있는 군에서 당뇨병의 유병기간이 길었다. 2. TAT 및 PIC의 농도는 정상 대조군에서는 2.8±1.2 ng/mL, 240.4±69.7 ng/mL이었고, 당뇨병 환자군에서는 9.5±22.6 ng/mL, 472.2±258.7 ng/mL이었다. TAT와 PIC 모두 당뇨병 환자군에서 정상 대조군에 비해 유의하게 증가되어 있었고(p<0.001), TAT/PIC ratio는 두 군간 차이가 없었다. 3. 당뇨병 환자의 혈관합병증에 따른 TAT 및 PIC, fibrinogen 농도는 합병증이 없는 군은 각각 4.1±2.4ng/mL, 362.2±272.0ng/mL, 322.7±102.4mg/mL으로 PIC와 fibrinogen의 증가를 보였으나, 연령을 보정한 후에는 통계학적 유의성은 없었다. 또 대혈관 합병증군에서는 각각 6.0±4.9 ng/mL, 507.4±321.6 ng/mL, 427.1±194.7 mg/dL이었으며 미세·대혈관 합병증군에서는 10.4±6.4 ng/mL, 484.8±269.7 ng/mL, 388.4±132.4 mg/dL으로 TAT의 증가를 보였으나 역시 연령을 보정한 후에는 통계학적 유의성은 없었다. 4. 미세혈관합병증군에서 HbA1c(>8%)가 높은 군의 PIC 농도가 유의하게 높았고(p=0.049), 대혈관합병증군에서 HbA1c(>8%)가 높은 군의 총 콜레스테롤 농도가 유의하게 높았다(p=0.042). 5. 총 당뇨병 환자군에서 PIC는 fibrinogen과 HbA1c와 양의 상관관계를, BMI와 음의 상관관계를 보였으며(r=0.47, 0.31,-0.25), 혈관 합병증이 없는 당뇨병 환자군에서만 TAT는 HbA1c와 양의 상관관계를 보였다(r=0.67). 결론:이상의 결과에서 혈장 TAT 및 PIC 농도는 당뇨병 환자에서 정상 대조군에 비해 의미있게 증가되어 있었고, 당뇨병 환자군에서는 연령의 증가와 유병기간이 혈액응고항진 및 용해의 장애에 큰 역할을 함을 알 수 있었으며, 총 당뇨병 환자군에 PIC와 HbA1c와 양의 상관관계를, BMI와 음의 상관관계를 보였으며 혈관 합병증이 없는 당뇨병 환자군에서만 TAT는 HbA1c와 양의 상관관계를 보였다. 따라서 당뇨병 환자에서 혈액응고 및 용해의 장애가 동반되어 있다고 볼 수 있으며, 혈장 TAT 및 PIC는 혈관합병증으로의 진행을 예측하는 지표로서 유용하리라 생각된다. 또 혈당조절정도와 상관성이 있으므로 혈당조절후에 추적검사를 시행하여 합병증의 예방이 가능한지 추후 연구가 필요하리라 생각된다. Background : Abnormality of coagulation and fibrinolystic system is known as a predisposing factor of vascular complication in diabetes. Although the pathogenesis is not well known, non-enzymatic glycation reaction and the increase in production of free radicals due to an increased oxidative stress may be linked to the hypercoagulibility and hypofibrinolytic activity. As indices of abnormality in coagulation and firinolysis in peripheral blood, plasma thrombin-antithrombin Ⅲ complex (TAT) and plasmin-α_2-plasmin inhibitor complex (PIC) were measured. The purpose of this study was to clarify whether hypercoagulability exists in diabetic patients with or without vascular complication. Methods : In our study, we measured plasma thrombin-antithrombin Ⅲ compelx (TAT) and plasmin-α_2-plasmin inhibit or complex (PIC) in 101 diabetic subjects and 20 controls. Comparing TAT and PIC levels in diabetic microvascular complication group, diabetic macrovascular complication group and controls, we examined correlation between risk factors associated with diabetic vascular complication. Results : 1. The group with diabetic vascular complication was older than group without complication. There was no significant difference in BMI, blood pressure, HbA_ic, blood sugar level, insulin, C-peptide, serum creatinine, total cholesterol, triglyceride, HDL-cholesterol, Lp (a) between two groups. The group with diabetic microvascular complication had longer duration of diabetes. 2. Concentration of TAT and PIC were 2.8±1.2 ng/ mL, 240.4±69.7 ng/ mL in controls and 9.5±22.6 ng/ mL, 472.2±258.7 ng/ mL in diabetic patients, respectively. TAT and PIC were significantly higher in diabetic patients than in control (p<0.001). But TAT/PIC ratio was no significant difference between two groups. 3. In diabetic patients, concentration of TAT and PIC and fibrinogen were respectively 4.1±2.4 ng/ mL, 362.2±272.0 ng/ mL, 322.7±102.4 mg/ dL in group without vascular complication and 5.3±4.1 ng/ mL, 529.5±258.7 ng/ mL, 374.9±106.2 mg/ dL in group with microvascular complication, which group had increase in PIC and Fibrinogen but no significance after correction of age. Concentration of TAT and PIC and Fibrinogen were 60.±4.9 ng/ mL, 507.4±321.6 ng/ mL, 427.1±194.7 mg/ dL in macrovascular complication, and 10.4±6.7 mg/ mL, 484.8±269.7 ng/ mL, 388.4±132.4 mg/ dL in combined vascular complication which group showed increase of TAT but also had no significant increase after correction of age. 4. In diabetic microvascular complication patients, group of high HbA_1c (>8%) (p=0.049) had significant high PIC concentration. In diabetic macrovascular complication patients, group of high HbA_1c (>8%) (p=0.042) had significant high total cholesterol concentration. 5. In all diabetic patients, PIC was positively correlated with fibrinogen and HbA_1c and negatively correlated BMI (r=0.47, 0.31, -0.25). Only in daibetic patients without angiopathy, TAT was positively correlated with HbA_1c (r=0.67). Conclusion : In this study, plasma TAT and PIC concentration significantly increased in diabetic patients compared with controls, and PIC was increased in group with microvascular complication, TAT were increased in group with combined micro macrovascular complication. However, there was no significance relationship existed when correctinf for age. PIC was correlated with HbA_1c. TAT was correlated with HbA_1c only in the group without angiopathy. Abnormality of coagulation and fibrinolysis were combined in diabetes, plasma TAT and PIC can be used as an index of vascular complication. Also we found the correlation with the degree of the blood glucose control. Therefore we need follow up study for the possibility of prevention of vascular complication after controlling the blood glucose to age-matched patients (J Kor Diaabetes Asso 25:354~363, 2001).