• 대한기계학회논문집A
• /
• 제35권8호
• /
• pp.913-920
• /
• 2011

본 논문은 4-매 주자직 유리섬유/에폭시 적층 복합재가 적용된 철도차량 경량 대차프레임의 피로 수명 및 강도 평가에 대해 기술한다. 대차프레임 경량화 재질로 적용된 유리섬유/에폭시 4-매 주자직 적층 복합재료의 피로특성 평가를 위하여 경사, 위사 그리고 $0^{\circ}/90^{\circ}$ 방향으로 적층된 시험편에 대하여 인장-압축 피로시험을 수행하였다. 유리섬유/에폭시 4-매 주자직 적층 복합재료의 피로시험은 5Hz의 주파수, -1의 응력비(R), $10^7$의 피로수명을 갖도록 하였다. 또한, JIS E 4207의 하중조건에 따른 대차프레임의 피로강도 평가를 Goodman 선도를 통하여 수행하였다. 유리섬유/에폭시 적층 복합재 경량 대차프레임의 피로수명 및 강도 평가기준을 만족하였으며, 무게를 고려할 경우 기존 대차프레임 재질인 SM490A 금속재에 비하여 우수한 피로특성을 갖는다.

• Asian-Australasian Journal of Animal Sciences
• /
• 제15권5호
• /
• pp.725-731
• /
• 2002

This experiment was performed to understand the changes in plasma leptin in association with plasma IGF-1, body weight and ADG from early growing to late finishing stages of Holstein steers. Blood collection was performed by arterial vein puncture at selected monthly ages of 1 (54 kg), 2.6 (103 kg), 7.2 (205 kg), 13.5 (314 kg), 16.9 (414 kg), 22.2 (550 kg), 24.9 (626 kg) and 27.4 months (695 kg). The blood was analyzed for leptin using the multi-species leptin RIA with recombinant bovine leptin (rbleptin) as standard, plasma IGF-1 was also measured using RIA. Against the standard rbleptin, the multi-species Leptin RIA system's sensitivity, cross reactivity, slope and recovery of 41.0 ng/ml rbleptin in plasma were 4.9 ng/ml, 11.22%, -1.396 and 97.8%, respectively. Plasma leptin measured were more than 5.0 ng/ml, which enable multi-species RIA system to investigate plasma leptin in normal growing steers. Body weight resulted to a highly significant second-degree polynomial relationship with plasma leptin (q=0.54, p<0.0001) and plasma IGF-1 (q=0.44, p<0.0001) from 1 to 27.4 monthly ages. However, the second-degree polynomial curve of plasma leptin and IGF-1 differs showing a concave and convex curvilinear relationship, respectively. ADG was not significantly associated to plasma leptin (r=0.06, p>0.05) and plasma IGF=1 (r=0.06, p>0.05) from 1 to 27.4 monthly ages. Low coefficient, but significant associated increase of plasma leptin and IGF-1 (r=0.12, p<0.008) from 1 to 27.4 months was observed. The uncoordinated increases of plasma IGF-1 at growing and plasma leptin at fattening period, may indicate (1) indirect involvement of endogenous IGF-1 on leptin secretion, and (2) IGF-1 level may signify lean and bone accretion while plasma leptin may mirror body fatness across the monthly ages of Holstein steers.

• 대한영양사협회학술지
• /
• 제11권3호
• /
• pp.365-374
• /
• 2005

This study was conducted to compare the validity of obese index among body mass index(BMI), waist to hip ratio(WHR), and waist circumference(WC) and to determine which is the best in relation to cardiovascular risk factors of middle aged Korean(40-64yr).Data from the 1998 Korean Health and Nutrition Survey were used(N=3380). Anthropometric indices and cardiovascular risk factors were measured. Chi-square test, analysis of variance following duncan's multiple range test, partial correlation analysis, and Receiver Operator characteristic(ROC) curves were used in the analysis. There was a significant increasing trend in WHR, systolic blood pressure(SBP), high density lipoprotein cholesterol(HDL), and fasting blood sugar(FBS) with age categories of male and in BMI, WC, WHR, diastolic blood pressure(DBP), SBP, total cholesterol(TC), low density lipoprotein cholesterol(LDL), triglycerol(TG), and FBS with those of female. Specially female had the characteristics of upper body fat and systolic blood pressure risk(p<0.05). Proportions of subjects with lifestyle factors related to cardiovascular risk in overweight or upper body fat group were higher than that of normal group. Higher proportions of subjects were practiced exercise in upper body fat group of male than in other groups. Among 7 cardiovascular risk factors in partial correlation analysis, BMI had the highest correlation coefficient in 6 risk factors in male, whereas WC in 4 risk factors in female. Mean of each obese index according to cardiovascular risk groups except smoker was higher than that of normal(p<0.05). These trends were shown in upper body fat group and female. In ROC analysis of 12 risk factors and health conditions, the largest area under curve among obese indices for risk factors were BMI in male and WHR in female. The optimal cutoff values of each index(BMI: WHR: WC) for one or more cardiovascular risk factors were 23.13: 0.89: 85.35 in male and 23.57: 0.84: 78.35 in female. The results showed that cardiovascular risk factors were prevalent in middle aged Koreans within normal limits of obese indices like another Asians. For the identification of cardiovascular risk factors of middle aged Koreans, BMI for men and WHR for women are appropriate indices. But it is recommended that BMI, WHR, and WC, all three indices should be considered, when using these indices.

• 대한치과보철학회지
• /
• 제31권3호
• /
• pp.423-446
• /
• 1993

Titanium and its alloys are finding increasing use in medical devices and dental implants. The strong selling point of titanium is its resistance to the highly corrosive body fluids in which an implant must survive. This corrosion resistance is due to a tenacious passive oxide or film which exists on the metal's surface and renders it passive. Potentiodynamic polarization measurement is one of the most commonly used electro-chemical methods that have been applied to measure corrosion rates. And the potentiodynamic polarization test supplies detailed information such as open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. This study was designed to compare the corrosion resistance of the commonly used dental implant materials such as CP Ti, Ti-6A1-4V, Co-Cr-Mo alloy, and 316L stainless steel. And the effects of galvanic couples between titanium and the dental alloys were assessed for their useful-ness-as. materials for superstructure. The working electrode is the specimen , the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is made of carbon. In $N_2-saturated$ 0.9% NaCl solutions, the potential scanning was performed starting from -800mV (SCE) and the scan rate was 1 mV/sec. At least three different polarization measurements were carried out for each material on separate specimen. The galvanic corrosion measurements were conducted in the zero-shunt ammeter with an implant supraconstruction surface ratio of 1:1. The contact current density was recorded over a 24-hour period. The results were as follows : 1. In potential-time curve, all specimens became increasingly more noble after immersion in the test solution and reached between -70mV and 50mV (SCE) respectively after 12 hours. 2. The Ti and Ti alloy in the saline solution were most resistant to corrosion. They showed the typical passive behavior which was exhibited over the entire experimental range. Therefore no breakdown potentials were observed. 3. Comparing the rupture potentials, Ti and Ti alloy had the high(:st value (because their break-down potentials were not observed in this study potential range ) followed by Co-Cr-Mo alloy and stainless steel (316L). So , the corrosion resistance of titanium was cecellent, Co-Cr-Mo alloy slightly inferior and stainless steel (316L) much less. 4. The contact current density sinks faster than any other galvanic couple in the case of Ti/gold alloy. 5. Ag-Pd alloy coupled with Ti yielded high current density in the early stage. Furthermore, Ti became anodic. 6. Ti/Ni-Cr alloy showed a relatively high galvanic current and a tendency to increase.

• Journal of Animal Science and Technology
• /
• 제57권5호
• /
• pp.18.1-18.8
• /
• 2015

Background: Quantitative real time reverse transcription PCR (qRT-PCR) is one of the most important techniques for gene-expression analysis in molecular based studies. Selecting a proper internal control gene for normalizing data is a crucial step in gene expression analysis via this method. The expression levels of reference genes should be remained constant among cells in different tissues. However, it seems that the location of cells in different tissues might influence their expression. The purpose of this study was to determine whether the source of mesenchymal stem cells (MSCs) has any effect on expression level of three common reference genes (GAPDH, ${\beta}$-actin and ${\beta}2$-microglobulin) in equine marrow- and adipose-derived undifferentiated MSCs and consequently their reliability for comparative qRT-PCR. Materials and methods: Adipose tissue (AT) and bone marrow (BM) samples were harvested from 3 mares. MSCs were isolated and cultured until passage 3 (P3). Total RNA of P3 cells was extracted for cDNA synthesis. The generated cDNAs were analyzed by quantitative real-time PCR. The PCR reactions were ended with a melting curve analysis to verify the specificity of amplicon. Results: The expression levels of GAPDH were significantly different between AT- and BM-derived MSCs (p < 0.05). Differences in expression level of ${\beta}$-actin (P < 0.001) and B2M (P < 0.006.) between MSCs derived from AT and BM were substantially higher than GAPDH. In addition, the fold change in expression levels of GAPDH, ${\beta}$-actin and B2M in AT-derived MSCs compared to BM-derived MSCs were 2.38, 6.76 and 7.76, respectively. Conclusion: This study demonstrated that GAPDH and especially ${\beta}$-actin and B2M express in different levels in equine AT- and BM-derived MSCs. Thus they cannot be considered as reliable reference genes for comparative quantitative gene expression analysis in MSCs derived from equine bone marrow and adipose tissue.

• 한국잡초학회지
• /
• 제13권1호
• /
• pp.62-70
• /
• 1993

Quinclorac에 대한 벼와 피의 반응차(反應差)를 밝히기 위하여 벼 89품종과 피 30종들의 반응(反應), 단백질(蛋白質) 패턴에 미치는 영향, 약해(藥害) 발현부위(發現部位)의 해부학적(解剖學的) 관찰, 및 quinclorac을 흡수(吸收)한 벼와 피의 누출(漏出)이 토마토 생육에 미치는 영향 등을 조사하여 얻어진 결과를 요약하면 다음과 같다. 1. Quinclorac에 대한 피 종류간의 반응(反應)을 조사한 결과 Echinochloa crus-galli var. crus-galli가 E. crus-galli var. praticola나 E. oryzicola에 비해 상대적으로 내성(耐性) 반응(反應)을 보였다. E. crus-galli var. crus-galli 종내에서도 지방 수집종에 따라서 반응이 다르며 30g ai/ha 처리구에서 진주피가 무처리에 대한 신초길이가 90.5%, 건물 중이 37.8%인데 반하여, 이리피가 각각 19.1%, 14.4%로 가장 민감한 반응(反應)을 보였다. 한편, 벼는 추천처리약량(推薦處理藥量)과 추천약량(推薦藥量)의 10배량(300g ai/ha), 100배량(3,000g ai/ha) 처리시 나타나는 신초길이의 반응은 정규분포곡선(正規分布曲線)을 보였다. 2. Quinclorac은 같은 종내(種內)의 피간(진주피와 이리피)의 단백질(蛋白質) 패턴(SDS-PAGE) 변화에는 큰 영향을 미치지 않았다. 3. Quinclorac에 민감한 이리피의 약해부위(藥害部位)에서 생체막(生體膜) 와해현상(瓦解現象)이 전자현미경(電子顯微鏡)에 의해 관찰되었다. 4. 추청벼의 quinclorac 누출량(漏出量)이 피 보다 많았고 같은 종내(種內)의 피 간에서는 quinclorac에 내성(耐性)인 진주피에서 감수성(感受性)인 이리피보다 누출량(漏出量)이 많았다.

• 한국수학사학회지
• /
• 제25권4호
• /
• pp.53-67
• /
• 2012

오늘날, 우주비행궤도의 정밀계산은 매우 실용적인 학문이 되었다. 프엥카레의 천체역학의 주요 키워드는 적분불변, 주기해, 점근해, 특성지수, 단일값을 갖는 새로운 적분의 불가능성등으로 볼 수 있다. 적분불변은 모든 시간에 걸쳐서 일정한 적분 값을 유지하는 것을 말한다. 곡선의 호상에서 취한 적분은 2, 3차원으로 확장하였다. 고유치는 궤적의 형식에 따라서 분류되는 바 매듭, 초점들, 말 안장점, 중심과 같은 것이다. 주기해에서는 고유값에 해당하는 특성지수에 따라서 주기해를 갖는다고 하였다. 주기해의 안정성은 특성지수의 성질을 조사하는 것과 동일한 것이다. 분지라고 불리는 천체궤도의 카오스적 존재 가능성을 프엥카레는 예외적 궤도의 존재로 주장하였고, 이는 아다마르의 견해대로 우연에 의한 확률적 궤도의 존재를 말하는 것이다. 호모크리닉점의 존재는 삼체문제의 이중 점근해를 말하고, 이것은 궤적이 카오적임을 말해주는 것이다. 주어진 조건에 따라서 엑스포넨셜 함수의 고유값인 특성지수가 계속 변함으로, 매우 작은 간격에서도 분지들은 얻게 되고, 원래의 주기와는 다소 멀어지는 것이다. 주기해의 안정성문제는 특성지수를 연구하는 것과 같다. 프엥카레는 궤적의 거동이 선형변환의 고유값 성질에 의존하고 이 고유값들과 서로 다른 특이점들 사이에 매우 밀접한 관련이 있음을 발견하였다. 뷔른스, 질덴, 순드만, 힐, 다윈, 벌코프, 하이테커, 아다마르등의 이론전개는 프엥카레의 이론과 불가분의 관계를 갖는다.

• 대한임상독성학회지
• /
• 제19권2호
• /
• pp.72-82
• /
• 2021

Purpose: A high anion gap (AG) is known to be a significant risk factor for serious acid-base imbalances and death in acute poisoning cases. The strong ion difference (SID), or strong ion gap (SIG), has recently been used to predict in-hospital mortality or acute kidney injury (AKI) in patients with systemic inflammatory response syndrome. This study presents a comprehensive acid-base analysis in order to identify the predictive value of the SIG for disease severity in severe poisoning. Methods: A cross-sectional observational study was conducted on acute poisoning patients treated in the emergency intensive care unit (ICU) between December 2015 and November 2020. Initial serum electrolytes, base deficit (BD), AG, SIG, and laboratory parameters were concurrently measured upon hospital arrival and were subsequently used along with Stewart's approach to acid-base analysis to predict AKI development and in-hospital death. The area under the receiver operating characteristic curve (AUC) and logistic regression analysis were used as statistical tests. Results: Overall, 343 patients who were treated in the intensive care unit were enrolled. The initial levels of lactate, AG, and BD were significantly higher in the AKI group (n=62). Both effective SID [SIDe] (20.3 vs. 26.4 mEq/L, p<0.001) and SIG (20.2 vs. 16.5 mEq/L, p<0.001) were significantly higher in the AKI group; however, the AUC of serum SIDe was 0.842 (95% confidence interval [CI]=0.799-0.879). Serum SIDe had a higher predictive capacity for AKI than initial creatinine (AUC=0.796, 95% CI=0.749-0.837), BD (AUC=0.761, 95% CI=0.712-0.805), and AG (AUC=0.660, 95% CI=0.607-0.711). Multivariate logistic regression analyses revealed that diabetes, lactic acidosis, high SIG, and low SIDe were significant risk factors for in-hospital mortality. Conclusion: Initial SIDe and SIG were identified as useful predictors of AKI and in-hospital mortality in intoxicated patients who were critically ill. Further research is necessary to evaluate the physiological nature of the toxicant or unmeasured anions in such patients.

• Journal of Chest Surgery
• /
• 제55권2호
• /
• pp.143-150
• /
• 2022

Background: The effectiveness of extracorporeal membrane oxygenation (ECMO) for patients with refractory cardiogenic shock or cardiac arrest is being established, and serum lactate is well known as a biomarker of end-organ perfusion. We evaluated the efficacy of pre-ECMO lactate for predicting 6-month survival in patients with acute coronary syndrome (ACS) undergoing ECMO. Methods: We reviewed the medical records of 148 patients who underwent veno-arterial (VA) ECMO for ACS between January 2015 and June 2020. These patients were divided into survivors and non-survivors based on 6-month survival. All clinical data before and during ECMO were compared between the 2 groups. Results: Patients' mean age was 66.0±10.5 years, and 116 (78.4%) were men. The total survival rate was 45.9% (n=68). Cox regression analysis showed that the pre-ECMO lactate level was an independent predictor of 6-month mortality (hazard ratio, 1.210; 95% confidence interval [CI], 1.064-1.376; p=0.004). The area under the receiver operating characteristic curve of pre-ECMO lactate was 0.64 (95% CI, 0.56-0.72; p=0.002; cut-off value=9.8 mmol/L). Kaplan-Meier survival analysis showed that the cumulative survival rate at 6 months was significantly higher among patients with a pre-ECMO lactate level of 9.8 mmol/L or less than among those with a level exceeding 9.8 mmol/L (57.3% vs. 31.8%, p=0.0008). Conclusion: A pre-ECMO lactate of 9.8 mmol/L or less may predict a favorable outcome at 6 months in ACS patients undergoing VA-ECMO. Further research aiming to improve the accuracy of predictions of reversibility in patients with high pre-ECMO lactate levels is essential.

• Journal of Chest Surgery
• /
• 제56권4호
• /
• pp.244-251
• /
• 2023

Background: Extracorporeal membrane oxygenation (ECMO) has been widely used in patients with cardiorespiratory failure. The serum albumin level is an important prognostic marker in critically ill patients. We evaluated the efficacy of using pre-ECMO serum albumin levels to predict 30-day mortality in patients with cardiogenic shock (CS) who underwent venoarterial (VA) ECMO. Methods: We reviewed the medical records of 114 adult patients who underwent VA-ECMO between March 2021 and September 2022. The patients were divided into survivors and non-survivors. Clinical data before and during ECMO were compared. Results: Patients' mean age was 67.8±13.6 years, and 36 (31.6%) were female. The proportion of survival to discharge was 48.6% (n=56). Cox regression analysis showed that the pre-ECMO albumin level independently predicted 30-day mortality (hazard ratio, 0.25; 95% confidence interval [CI], 0.11-0.59; p=0.002). The area under the receiver operating characteristic curve of albumin levels (pre-ECMO) was 0.73 (standard error [SE], 0.05; 95% CI, 0.63-0.81; p<0.001; cut-off value=3.4 g/dL). Kaplan-Meier survival analysis showed that the cumulative 30-day mortality was significantly higher in patients with a pre-ECMO albumin level ≤3.4 g/dL than in those with a level >3.4 g/dL (68.9% vs. 23.8%, p<0.001). As the adjusted amount of albumin infused increased, the possibility of 30-day mortality also increased (coefficient=0.140; SE, 0.037; p<0.001). Conclusion: Hypoalbuminemia during ECMO was associated with higher mortality, even with higher amounts of albumin replacement, in patients with CS who underwent VA-ECMO. Further studies are needed to predict the timing of albumin replacement during ECMO.