• Toxicological Research
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• 제33권2호
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• pp.157-164
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• 2017

This study was to evaluate the age-dependent effects of caffeine exposure on the long bones and reproductive organs using male rats. A total of 15 immature male rats and 15 young adult male rats were allocated randomly to three groups: a control group and two groups fed caffeine with 120 and 180 mg/kg/day for 4 weeks. Exposure to caffeine at either dose significantly reduced body weight gain; a proportional reduction in muscle and fat mass in immature animals, whereas a selective reduction in fat mass with relatively preserved muscle mass in young adult animals. The long bones of immature rats exposed to caffeine were significantly shorter and lighter than those of control animals along with decreased bone minerals. However, there was no difference in the length or weight of the long bones in young adult rats exposed to caffeine. Exposure to caffeine reduced the size and absolute weight of the testes significantly in immature animals in comparison to control animals, but not in young adult animals exposed to caffeine. In contrast, the adrenal glands were significantly heavier in caffeine-fed young adult rats in comparison to control animals, but not in caffeine-fed immature rats. Our results clearly show that the negative effects of caffeine on the long bones and testes in rats are different according to the age of the rat at the time of exposure, and might therefore be caused by changes to organ sensitivity and metabolic rate at different developmental stages. Although the long bones and testes are more susceptible to caffeine during puberty, caffeine has negative effects on body fat, bone minerals and the adrenal glands when exposure occurs during young adulthood. There is a need, therefore, to educate the public the potential dangers of caffeine consumption during puberty and young adulthood.

• 대한한의학회지
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• 제21권1호
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• pp.84-90
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• 2000

Background and Purpose: Stroke in young adults is relatively uncommon. Only 3.7-14.4% of all strokes occur in patients aged 15-45 years. Stroke in young adults has more various and diverse possible causes than stroke in the elderly. We studied to gain further insight into both pathogenic and etiologic determinants in young adults with stroke. Methods : We retrospectively reviewed the medical records of 230 young patients aged 15-45 years who were admitted to the 2nd internal medicine department of Kyung Hee Oriental Medical Center with a diagnosis of stroke between May 1995 and May 1999. We analysed clinical features and diagnostic tests, such as brain imaging, cerebral angiography, echocardiography, 24 hours holter monitoring and other laboratory tests. Results : 1. Of 230 young patients with stroke aged 15-45 years(176 males(76.5%) and 54 females(23.5%)), 140 patients(60.9%) showed ischemic stroke and 90 patients(39.1 %) showed hemorragic stroke. 2. The most prevalent age group was from 40 to 45 years with 142 patients(61.7%) 3. The most frequent site of 140 ischemic stroke was MCA territory in 93 cases(66.4%) and Multiple, VA territory, PCA territory, ACA territory in order of frequency. 4. The most frequent site of 90 hemorrhagic stroke was basal galglia hemorrhage 57 cases(63.3%) and subcortical 13 cases(14.5%), pons, thalmus, subarachnoid, cerebellum in order of frequency. 5. The causes of hemorrhagic stroke were hypertension 49 cases(54.5%), arteriovenous malformation 7 cases(7.8%), ruptured aneurysm 4 cases(4.5%), angioma 3 cases(3.3%). 6. The risk factors of ischemic stroke were smoking, alcohol drinking, hyperlipidemia, hypertension, obesity, heart disease, history of CVA, diabetes mellitus, in order of frequency. 7. The comparison of risk factors between ischemic and hemorrhagic stroke: hypertension was prevalent in hemorrhagic stroke, heart disease and history of CVA were prevalent in ischemic stroke. Conclusions: From the above results, we found that stroke in young adults had various possible causes. Young adults with stroke deserve an extensive but tailored evaluation which include angiography and echocardiography for diagnosis.

• Human Ecology Research
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• 제54권6호
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• pp.611-620
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• 2016

This study examined how parent-child attachment, parental involvement in child rearing and instruction for children's effective use of a smart device reflect on young children's smart device overuse behavior. We collected questionnaires from 196 parents with children attending early childhood education institutions for the survey. Frequency analysis as well as Person correlation coefficient and regression analysis were conducted using IBM SPSS 21.0 statistics. The results showed that 91% of targeted young children were using a smart device and 78% first used them before age 5. As for time of use hours, 43.9% used their smart device from 30 minutes to 1 hour on average. In addition, parent-child attachment and father's involvement in child rearing were found to be inversely correlated to young children's smart device overuse. The result of hierarchical regression analysis on parent factors influencing young children's smart device overuse behavior indicated that mothers' contact-seeking behavior to young children, mother's involvement in learning and instruction for children's effective use of a smart device at home had beneficial effects. This study analyzed parent factors that influenced young children's smart device overindulgence. In addition, the baseline data of this study will be utilized to develop programs for the prevention and therapy to solve the smart device overindulgence as well as to establish young children's guidelines for using a smart device.

• Elastomers and Composites
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• 제42권3호
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• pp.143-150
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• 2007

본 연구에서는 고무제품의 수치 안정성과 성능유지에 직접적으로 영향을 미치는 중요한 특성 중 하나인 온도변화에 따른 고무재료의 경도변화를 고찰하였다. 새롭게 제작된 Inter-national Rubber Hardness Degree(IRHD, Normal type) 경도측정 시험기를 사용하여 미충전된 NR과 SBR 시편의 여러 온도에서 경도변화를 측정하였으며 Young's modulus 값과 비교하였다. NR과 SBR 모두 유리전이온도 근처에서 경도와 Young's modulus의 급격한 변화를 보였다. 온도가 증가함에 따라 경도와 Young's modulus 값이 증가하는 경향을 보였으며 이는 분자의 운동성과 엔트로피 영향으로 해석할 수 있다. 카본블랙과 실리카가 충전된 NR과 SBR의 경우 충전제의 함량이 증가함에 따라 경도에 미치는 온도의 영향이 감소함을 관찰하였다.

• 대한한의진단학회지
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• 제11권2호
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• pp.1-12
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• 2007

Objectives: The aim of the present investigation was to determine whether the finger photoplethysmographic waveform of a healthy young man will become analogous to those of healthy old men when the photoplethysmographic harmonic components in the young man decrease. Methods and Results: The finger photoplethysgmoraphy was measured in 21 old men over the age of 60 years and a young men. We acquired the representative pulse waveform of old man by averaging the finger photoplethysmographic waveforms measured in the old men. after the photoplethysmographic harmonic components in the young man were diminished with notch filtering, we compared the representative pulse waveform of old man and the pulse waveforms of which the harmonic components decreased in the young man. The finger photoplethysmographic waveform of the young man became analogous to those of the old men as the photoplethysmographic harmonic components in the young man were diminished with notch filtering. Conclusions: Decrease of the second harmonic component may be a precondition of typical age-related change of the pulse waveform.

• 한국운동역학회지
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• 제15권3호
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• pp.51-59
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• 2005

To examine the influence of aging on the mechanism of muscle fatigue, we compared the magnitude of central and peripheral fatigue in young and old women before, during and after a sustained submaximaI isometric contraction of elbow flexor muscles. Twelve women (6 young. $20.7{\pm}1.2$ years and 6 old, $68.8{\pm}29$ years) performed a contraction at 20% of maximal voluntary contraction (MVC) torque with their non-dominant arm. The old women were weaker than the young women, however their endurance time for the 20% contraction was longer compared with the young women ($1822{\pm}444$ vs. $1061{\pm}678$ sec, P <. 05). Both groups had a similar reduction in voluntary activation ratio (VA) during and after the fatiguing contraction. However, the old women showed much greater variability in VA before and after the contraction ($91.61{\pm}4.54%$ and $76.70{\pm}19.55\;%$ range of $79{\sim}99$ to $87{\sim}99%$ respectively) compared with the young women ($95.71{\pm}1.86\;%$ and $83.46{\pm}7.57\;%$ range of $39{\sim}75$ to $69{\sim}90%$, respectively). Furthermore, the EMG activity of the elbow flexor muscles and triceps brachii was greater for the old women compared with the young women throughout the fatiguing contraction, indicating different activation strategies with age. Indices of peripheral fatigue including twitch properties, showed that fatigue within the muscle was more rapid for the young women compared with the old women. These results suggest that although old women are weaker than young women, they have greater endurance due to mechanisms within muscle. Furthermore, old women showed great variability in their ability to optimally activate all muscle fiber compared with young women for an isometric contraction.

• Safety and Health at Work
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• 제10권1호
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• pp.3-20
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• 2019

This review aimed to identify risk factors for occupational accidents and illnesses among young workers in the Nordic countries and to attain knowledge on specific vulnerable groups within the young working force that may need special attention. We conducted a systematic review from 1994 to 2014 using five online databases. Of the 12,528 retrieved articles, 54 met the review criteria and were quality assessed, in which data were extracted focusing on identifying occupational safety, health risk factors, and vulnerable groups among the young workers. The review shows that mechanical factors such as heavy lifting, psychosocial factors such as low control over work pace, and organizational factors such as safety climate are all associated with increased injury risk for young Nordic workers. Results show that exposures to chemical substances were associated with skin reactions, e.g., hand eczema. Heavy lifting and awkward postures were risk factors for low back pain, and high job demands were risk factors for mental health outcomes. The review identified young unskilled workers including school drop-out workers as particularly vulnerable groups when it comes to occupational accidents. In addition, apprentices and young skilled workers were found to be vulnerable to work-related illnesses. It is essential to avoid stereotyping young Nordic workers into one group using only age as a factor, as young workers are a heterogeneous group and their vulnerabilities to occupational safety and health risks are contextual. Politicians, researchers, and practitioners should account for this complexity in the education, training and organization of work, and workplace health and safety culture.

• Asian-Australasian Journal of Animal Sciences
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• 제11권4호
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• pp.410-415
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• 1998

The effects of the proprotion of cows inseminated by young A. I. bulls on genetic improvement in the Japanese Holstein population were examined using a simulation technique. The proportion of recorded cows inseminated by young A. I. bulls was assumed to be from 10% to 100% of the total number of recorded cows. The expected total genetic improvement was estimated for all cows and recorded and non recorded cows. The effects of the above were remarkable in the schemes that proven sires were used to produce recorded and non recorded cows for a limited time. Also the increase in the rates for -the expected total genetic improvement was larger when the proportion of recorded cows that were inseminated by young A. I. bulls was about 10% to 40%. When the expected total genetic improvement was estimated for the entire population, we found that the highest values were in a range of about 40 to 60% recorded cows that were inseminated by young A. I. bulls. On the other hand, the expected total genetic improvement that was only estimated in recorded cows dramatically decreased for more than 40% of the recorded cows. The results of this study showed that the optimal proportion of recorded cows inseminated with young A. I. bulls should be about 30% in the Japanese Holstein population.

• 농촌지도와개발
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• 제26권4호
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• pp.181-191
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• 2019

The purpose of this study is to identify the characteristics of young farmers' residential location characteristics. Based on residential location theory and previous studies on the stated preference for residential environment of young farmers, this study develops a spatial econometrics model using housing and neighborhood variables, accessibility variables, natural environment variables and farm economics and management variables. The findings suggest that the higher rate of young farmers has a positive relationship with higher population density, higher housing price, closer distance to city centers and Eup districts compared to Myeon districts. In addition, areas which have higher rate of farmers with high sales and growing certain crops such as fruits and vegetables are revealed to have higher rate of young farmers. This study presents that maintaining rural vitality is also crucial for attracting young farmers to rural areas and remaining them in the farm as active agricultural workforce.

• 한국보육지원학회지
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• 제13권3호
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• pp.83-102
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• 2017

Objective: This study investigates the main effects and interaction effects of mother's reactions to young children's negative emotions on the children's problem behaviors. Methods: A total of 346 mothers with toddlers completed questionnaires, the data were analyzed using Pearson's correlation coefficient and multiple regression. Results: First, mothers' supportive response to young children's negative emotions, including expressive encouragement, emotion-focused reactions, and problem-focused reactions, showed negative relations with the children's internal and external problem behaviors. Mothers' unsupportive response to children's negative emotions, including distress reactions, minimization reactions, and punitive reactions, showed positive relations with the children's internal and external problem behaviors. Second, an interactive effect was observed. For external problem behavior, mothers' lower distress reactions accompanied by higher emotion-focused reactions, lower punitive reactions accompanied by higher emotion-focused reactions, lower distress reactions accompanied by higher problem-focused reactions, and lower punitive reactions accompanied by higher problem-focused reactions all decreased children′s problem behavior. However, for internal problem behavior, only mothers' lower distress reactions accompanied by higher emotion-focused reaction decreased children′s problem behavior. Conclusion/Implication: The main interaction effect on mothers' reaction to young children's negative emotional expression shows that preventive intervention is needed to address problem behavior.