• Computers and Concrete
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• 제11권1호
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• pp.39-49
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• 2013

The use of ground fly ash in concrete can increase the risk of slump loss due to the drastic surface change of the particles after the grinding treatment and the accelerated reaction compared to the untreated ash. This study is aimed at the early age hydration and time-dependent rheology changes of cement paste containing ground fly ash. An original fly ash is ground into different fineness and the hydration of cement paste containing the ground fly ash is monitored with the ultrasound propagation method. The zeta potentials of the solid particles are measured and the changes of rheological parameters of the cement pastes with time are analyzed with a rheometer. A particle packing model is used to probe packing of the solid particles. The results show that the early age hydration of the paste is strongly promoted by replacing Portland cement with fly ash up to 30 percent (by mass), causing increase of the yield stress of the paste. The viscosity of a paste containing ground fly ash is lower than that containing the untreated ash, which is explained by the denser packing of the solid particles.

• 대한치과의사협회지
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• 제9권10호
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• pp.611-615
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• 1971

The articular discs from temporomandibular joints of thirty men and women whose ages ranged between 20 and 70 years hve been used in this study. The articular discs of the temporomandibular joints of human postmortem material was examined individually by means of microscopic techniques. The following changes were seen: 1. With advancing age some of fibroblast was developed into chondroid cells. Which later may differentiate into true chondrocytes. 2. In young individuals the elastic fibers found only I relatively small numbers. With advancing age elastic fibers was increased in number. 3. With advancing age the arrangement of fibrous tissue are irregular and loosely separated. 4. In the discs, as well as in the fibrous tissue covering the articular surfaces, this cellular changes seems to be dependent upon mechanical influences.

• 수면정신생리
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• 제27권2호
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• pp.33-40
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• 2020

An infant's sleep varies considerably from that of adults in terms of structure, amount, and breathing pattern. After birth, sleep becomes evenly distributed throughout the day and night. Nighttime sleep gradually increases with the maturation of circadian rhythm, and sleep is gradually consolidated. Electroencephalography characteristics change with age, from early and dominant active (REM) sleep in newborns to increasing NREM sleep. Similar to other elements of growth, the upper respiratory tract and ribcage gradually increase in size with age, and respiratory control also improves. With these changes, sleep patterns also change. At this time that various sleep disorders may appear. Improved understanding of age-dependent changes in infant sleep can help determine the etiology and facilitate diagnosis of infant sleep diseases.

• Genomics & Informatics
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• 제12권4호
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• pp.208-215
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• 2014

Recently, new methods have been developed for estimating the current and recent changes in effective population sizes. Based on the methods, the effective population sizes of Korean populations were estimated using data from the Korean Association Resource (KARE) project. The overall changes in the population sizes of the total populations were similar to CHB (Han Chinese in Beijing, China) and JPT (Japanese in Tokyo, Japan) of the HapMap project. There were no differences in past changes in population sizes with a comparison between an urban area and a rural area. Age-dependent current and recent effective population sizes represent the modern history of Korean populations, including the effects of World War II, the Korean War, and urbanization. The oldest age group showed that the population growth of Koreans had already been substantial at least since the end of the 19th century.

• International Journal of Advanced Culture Technology
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• 제9권1호
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• pp.1-6
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• 2021

This study aims to test the relationship between the change in population size and population composition and crime changes. The analytical model includes variables representing changes in population size and population composition, three dependent variables for crime changes, and three control variables. Changes in popuvpdllation size and population composition are measured by indicators such as population size, gender, age groups, and immigrants and foreign workers, and crime changes by felonious, burglary, and violent crime volumes. The sample includes 154 cities and counties in South Korea, and the sample period is from 2010 to 2017. As a result of the analysis, I examine that the decrease in the number of young and men are likely to lead to a decline in felonious and violent crimes, but a high rate of the elderly and the increasing racial heterogeneity are likely to accelerate the fear and worries about crimes.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.347-357
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• 2020

This research aims to shed light on the technology adoption process and its drivers in the Vietnamese educational system. Research data was collected with an online questionnaire from more than 600 teachers in primary schools, secondary schools, high schools, colleges, and universities in Vietnam in 2020. Based on a holistic literature review, we develop a model of two extrinsic factors (global needs and school-infrastructure), and two intrinsic factors (teachers' technological literacy and their beliefs), which are correlated with the teachers' technological adoption. We measure the dependent variable by asking the teachers' ability and their efficacy to implement technology in teaching according to a Likert scale. With the support of SPSS_22 and STATA_2015, we find that over 70% of changes in technology adoption are explained by the changes in four independent variables and three control variables related to age, gender, and teaching-level of the teachers. Furthermore, these independent variables are significantly and positively associated with two dependent variables. However, a significant difference in technology integration ability can be seen among teachers' gender, age, and school-level. Specifically, male teachers seem to adopt technology at schools than female teachers better, and university teachers have the lowest level of technology adoption compared to other school-level teachers.

• Applied Microscopy
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• 제22권1호
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• pp.113-127
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• 1992

The present study was investigated to elucidate the effects of chlorambucil the heart tissue of various-aged rats. The male rats ranging from 3 to 36 months were used. The cytochemical and biochemical changes in myocardium of the rats were studied in the aspect of free radical roles in aging process. With the goals of evaluating the potential roles of free radicals in aging process, evidence was shought for alterations of myocardial lipid peroxide levels in control and chlorambucil treated rats. The result are summarized as follows: 1. Cytochemical studies showed that the activities of $Mg^{++}$-ATPase and succinic dehydrogenase increased with age. However, these enzyme activities were decreased with treatment of chlorambucil, when compared with control group. Interestingly it was observed that chlorambucil treatment increased the activity of acid phosphatase from 6 months upto 18 months, and decreased after 18 months. 2. The lipid peroxide level in myocatdium was increased with age; chlorambucil-treated group was higher than that of control group. 3. Age-dependent increase in activities of monoamine oxidase, xanthine oxidase and catalase was observed. But the increase of catalase activity was higher than that of monoamine oxidase and xanthine oxidase activity in control group. However, in chlorambucil-treated group, age-dependent decrease of these enzyme activities was observed, and catalase activity was more significant particularly with regard to other enzymes. In consequently, the morphological alterationsof myocardium due to chlorambucil treatment was exclusively observed. We demonstrate that this alteration is occured by lipid peroxidation upon chlorambucil treatment.

• Childhood Kidney Diseases
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• 제9권2호
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• pp.119-127
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• 2005

목 적 : 단백뇨 질환에서 볼 수 있는 사구체 상피세포(glomerular epithelial cells, GEpC) 족돌기 사이에 위치한 세극막(slit diaphragm)의 P-cadherin의 당뇨조건에 따른 병리학적 변화를 알아보고자 하였다. 방 법 : 백서 GEpC을 배양하고 고농도의 당과 후기당화합물(advanced glycosylation endproducts, AGE)을 적용하여 당뇨병 환경에 가까운 조건을 설정한 후, p-cadherin 단백양은 Western 분석으로, 유전자 표현의 변화는 RT-PCR로 관찰하였다. 실험군은 당의 농도를 5 또는 30mM로, AGE와 BSA를 첨가하고 osmotic control로서 당 5 mM에 mannitol 25 mM을 섞은 것을 조합하여 A5, A30, B5, B30, Aosm로 하였다. 결 과 : P-cadherin 단백양은 B5 결과를 대조군으로 비교하여 당을 첨가한 B30에서 50.4$\%$의 감소, AGE를 추가한 조건인 A5와 A30에서 각각 7.4$\%$와 30.4$\%$의 의미 있는 감소를 보였다. 또한 P-cadherin mRNA의 표현은 B30에서 40.3$\%$의 감소, A30에서 27.2$\%$의 의의 있는 감소를 보였다. 이러한 감소 소견은 osmotic control(Aosm)에서는 관찰할 수 없었다. 결 론 : 고농도의 당과 AGE에 의한 GEpC의 P-cadherin을 유전자 수준에서의 억제로 단백의 생성 감소를 초래함으로써, 당뇨환경에서 세극막 성분의 변화를 설명할 수 있으며, 추후 이의 변화 기전에 대한 연구가 필요할 것으로 사료된다.

• Applied Microscopy
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• 제20권2호
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• pp.127-159
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• 1990

This study was investigated to elucidate the effect of chlorambucil on the heart in aging rats. Male rat ranging in age from 3 to 36 months were used. Each age groups(3, 6, 12, 18, 24, 36 months) included control and chlorambucil treated rats. As a part of the study, the ultrastructural changes in the left ventricular myocardial cells were described by using the qualitative and morphometric techniques. The results are summarized as follows. Age associated ultrastructural changes included: an increase in vacuoles, protrusion of plasma membranes, lipid droplets, and lipofuscins in myocardium of control groups. These changes which begin to occur at 12 months and continue through 36 months. At the 36 months some instance of unusual formation of contraction band and separation of intercalated discs were encountered. Morever, these changes and contents with chlorambucil treatment were remarkably increased in comparison with control groups. Age-dependent changes of control group measured with morphometry were not observed in the volume densities of mitochondria and myofibrils. But there was increase in interstitium. On the other hand decrease in sarcoplasmic reticulum and T-tubule system. In chlorambucil treated groups, volume densities of mitochondria and interstitium were increased in comparison with those of the control groups. But sarcoplasmic reticulum and T-tubule system were remarkably decreased.

• 수면정신생리
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• 제15권2호
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• pp.77-81
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• 2008

배 경：수면은 크게 비렘수면(non-REM sleep)과 렘수면(REM sleep)으로 나눌 수 있으며 렘수면 중에는 근력의 소실로 상기도 확장 근육의 긴장도가 저하되고 상기도 저항은 증가하여 무호흡증이 발생하거나 악화될 수 있다. 폐쇄성 수면무호흡증 자체에 대해서는 이미 많은 부분이 알려져 왔으나 렘수면에만 특이적으로 나타나는 렘수면 의존성 폐쇄성 수면무호흡증(REM-dependent OSA)은 그 중요성이 간과되어 왔다. 본 연구에서는 REM-dependent OSA 환자들의 임상 특성과 수면 변인을 살펴보고자 하였다. 방 법：2004년 3월부터 2007년 2월까지 시립은평병원 수면검사실을 방문하여 경도나 중등도의 폐쇄성 수면무호흡증으로 진단받은(5$53.7{\pm}16.7$, 남성：42명)를 대상으로 하였다. REM-dependent OSA(AHIREM/AHINREM${\ge}$2) 환자군과 No REM-dependent OSA(AHIREM/AHINREM<2) 환자군의 임상적 특성과 수면 관련변인을 비교하였다. 통계분석은 Statistica 6.0 프로그램을 사용하였으며, 유의수준은 p<0.05로 하였다. 결 과：대상군 56명 중 21명(37.5%)가 REM-dependent OSA으로 진단되었다. 두 군사이의 연령, 성별, BMI (Body Mass Index)는 유의한 차이를 보이지 않았다. 성별, 연령, BMI, PLMI를 통제한 후, 수면 관련 변인 중 REMdependent OSA 환자군에서 AHI(Apnea Hypopnea Index), ODI(Oxygen Desaturation Index)가 유의하게 낮았다($12.1{\pm}6.4$ vs. $35.9{\pm}24.7$, p=0.010; $6.0{\pm}5.3$ vs. $24.0{\pm}20.4$, p=0.006, respectively, ANCOVA). REMdependent OSA 환자군에서유의하게 높은 2단계 수면이 관찰되었다($58.5{\pm}10.3$ vs. $51.2{\pm}13.2$, p=0.031, ANCOVA). REM-dependent OSA군으로 대상군을 한정하였을 때, 성별, 연령, BMI, PLMI를 통제한 후, 렘수면중 AHI는 전체 수면중 AHI, 비렘수면중 AHI, ODI와 유의미한 양의 상관관계를 보였다(r=0.720, p=0.001；r=750, p=0.001；r=0.749, p=0.001, partial correlation, respectively). 결 론 ：본 연구에서는 폐쇄성 수면무호흡증 환자 중 37.5%를 REM-dependent OSA 환자로 진단할 수 있었다. REM-dependent OSA 환자는 더 경한 정도의 수면 무호흡증을 보이는 경향이 있었으며, 2단계 수면 분율의 증가 같은 수면구조의 변화와 연관되어 있었다. 또한, 렘수면중의 무호흡은 산소포화도 저하와 연관되어 있었다.