• Title/Summary/Keyword: 노화

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Recent Trends on Telomerase Activators, Sirtuin Activators, and Senolytics as a Potential Anti-aging Agent (잠재적인 항노화제로 텔로머레이즈 활성화제, 서르튜언 활성화제, 세노릭틱스에 대한 최신 동향)

  • Kim, Moon-Moo
    • Journal of Life Science
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    • v.30 no.9
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    • pp.819-825
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    • 2020
  • All living organisms exhibit the characteristics of aging, such as skin wrinkle formation, muscle degeneration, cataracts, and hair graying as the number of aged cells increases over time. Senescence, which is known as a key cause of aging, is directly related to the aging of living organisms because cells are aged by external and internal factors and eventually cell proliferation is stopped. Senescence is caused by the gradual shortening of the telomere with cell division, and lifespan is determined by the length of the telomere. Recently, it has been found that the histone deacetylase, which can influence gene expression, is not only involved in yeast but also deeply involved in anti-aging mechanisms in both C. elegans and humans. It was also discovered that old cells play a decisive role in the aging phenomenon, and it has been reported that it is possible to promote the proliferation of young cells and delay aging by removing these senescent cells from the inside. Therefore, in order to develop potential anti-aging agents in the future, research should begin with an in-depth study of telomerase activators, sirtuin activators, and senolytics.

Change of Physical Properties of Binder Extracted from after Artificial Aging of Asphalt Concretes (아스팔트 콘크리트의 노화 후 추출한 바인더의 물리적 특성 변화)

  • Kim, Kwang-Woo;Doh, Young-Soo;Kim, Sung-Woon
    • International Journal of Highway Engineering
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    • v.4 no.4 s.14
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    • pp.53-66
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    • 2002
  • Asphalt binder characteristics in asphalt mixture are changed due to aging. However. depending upon aggregate and binder used, asphalt mixture dose not show the same level of stiffness and brittleness under the same ageing level. The factors affecting Physical Properties change of the asphalt binder within aged asphalt concrete are not well known and there is limited study which is dealing with this topic This study dealt with evaluation of physical properties of asphalt binder recovered from the mixtures after short-term and long-term aging. Two asphalts. two aggregates. two gradations and four polymers were used to make 32 mixture combinations. The mixtures were prepared and aged artificially in a forced draft oven. The measured physical properties included absolute viscosity, kinematic viscosity and penetration. Statistical analyses were carried out to find out the factor(s) having a significant effect on change of physical property of asphalt binder due to asphalt mixture aging. The results of study shown that aggregate, gradation and polymer had a significant effect on change of physical properties of asphalt binder.

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The Effects of Physical Aging of PSF/AS4 Laminate on Fatigue (PSF/AS4 복합재료의 가속노화가 피로강도에 미치는 영향)

  • Kim, Hyung-Won
    • Composites Research
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    • v.19 no.4
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    • pp.1-6
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    • 2006
  • The effects of aging on fatigue of PSF/AS4 laminates tvas studied using the new energy release rate analysis. The analysis by the variational mechanics has been useful in providing fracture mechanics interpretation of matrix microcracking in cross-ply laminates. This paper describes the changes of the critical energy release rate ${\Delta}Gmc$(microcracking toughness) about the variation of the aging period during fatigue loading. The master plot by modified Pans-law gives a characterization of a material system's resistance to microcrack formation. PSF/AS4 $[0/902]_s$ laminates were aged at four different temperatures based on the glass transition temperature for 60 days. At all temperatures, the toughness decreased with aging time. The decrease of the toughness at higher temperature was faster than at lower temperature. To assess the effects of aging on fatigue, the unaged laminates were compared with the laminates which were aged for 60 days at $170^{\circ}C$ near $180^{\circ}C\;T_g$. The slope of dD/dN versus A 6u, of the aged laminates was lower than that of the unaged laminates. There was a significant shift of the aged data to formation of microcracks at the lower values of ${\Delta}G_m$.

Natural Aging Effect on the Fiber Tensile Strength of Carbon Epoxy Pressure Vessel (자연 노화에 따른 카본 에폭시 압력용기의 섬유 인장 강도 변화)

  • Hwang, Tae-Kyung;Park, Jae-Byum;Kim, Hyoung-Geun;Doh, Young-Dae
    • Composites Research
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    • v.20 no.2
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    • pp.1-9
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    • 2007
  • To evaluate and investigate the aging characteristics and the structural service lifetime of the CFV(carbon fiber pressure vessel), natural aging tests were carried out using the CFVs, which had been placed and aged at outdoor and indoor laboratories for 10 and 15 years, respectively. To obtain the probabilistic characteristics of ageing characteristics in aged CFVs, inner pressure loading test was conducted with ring specimens taken from aged CFVs. And, to observe the interface morphology of aged CFVs, the micro-photographs were taken by SEM microscope and the fractured interfaces between the carbon fiber and the matrix resin were scrutinized. Based on the Weibull parameters of the tensile failure strain of aged CFVs, the degradation of the 10 and the 15 year aged CFV occur by 19% and 23%, respectively, and the effect of the placement, whether being placed inside the laboratory or not, is not so significant. However, the outer layer protection, such as painting, is found very advantageous to prevent CFV from aging.

Effects of Thermal Aging of Natural Rubber Bearing on Seismic Performance of Bridges (천연고무받침의 열 노화가 교량 내진성능에 미치는 영향)

  • Oh, Ju;Jung, Hie-Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.3
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    • pp.855-864
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    • 2013
  • The dynamic characteristics of natural rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear properties. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they inevitably end up facing damage. A main cause of aging like this is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have some effects on shear stiffness, energy absorption, and equivalent damping coefficients of the bearings. Furthermore, a deterioration in the dynamic properties of the natural rubber bearings caused by the thermal aging was applied to an actual bridge and then the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the natural rubber bearings caused by the thermal aging bring only a minor effect on the seismic performance of bridges.

Influence of Aging of Lead Rubber Bearing on Seismic Performance of Bridges (납고무받침의 노화가 교량의 내진성능에 미치는 영향)

  • Park, Seong-Kyu;Oh, Ju
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.2A
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    • pp.109-116
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    • 2012
  • The dynamic properties of lead rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear qualities. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they can end up inevitably facing damage. A main cause of such aging is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings with each other before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have an effect on shear stiffness, energy absorption, and equivalent damping coefficients. Furthermore, a decline in the dynamic properties of the lead rubber bearings by means of the thermal aging process was applied to an actual bridge and the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the lead rubber bearings have a minor effect on the seismic performance of bridges.

Relationship between Leaf Senescence and Photosynthate Translocation during Grain filling in Barley (대맥의 등숙기간중 엽신의 노화와 동화산물의 전류와의 관계)

  • 남윤일;구본철;연규복;맹돈재
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.36 no.1
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    • pp.34-40
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    • 1991
  • The study aimed to investigate the relationship between the rates of leaf senescence and photosynthate translocation at post-anthesis. Seven barley varieties were observed at Suweon in 1988-89. The varieties differed significantly in the number of leaves survived and the rate of photosynthate transolcation with the progress of grain filling. The rate of grain filling was higher in the fast leaf sene-scencing varieties than the slow senescencing ones. There was a close coincidence between the rates of grain filling and $\^$14/c translocation into grains. Photosynthesis was higher in the fast leaf senescencing varieties at early stage of grain filling, but the reverse phenomenon was observed at the late stage of grain filling. The grain yield of fast senescencing varieties was higher than that of slow ones.

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Establishment of Hygrothermal Aging Mechanism via Thermal Analysis and Extraction of Reaction Kinetics of Ti Metal-based Pyrotechnic Materials (티타늄 금속 기반의 파이로테크닉 물질에 대한 열분석 및 반응특성 추출을 통한 열·수분 노화 메커니즘 구축)

  • Oh, Juyoung;Yoh, Jai-ick
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.9
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    • pp.759-769
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    • 2021
  • For aerospace propulsion systems, Titanium Hydride Potassium Perchlorate (THPP) is a material commonly used as a pyrotechnic initiator that generates gas when energy is supplied or as a supplement charge for NASA standard initiator (NSI). However, when the energetic materials are stored for a long time, it faces the problem of 'aging'. In this study, changes in thermodynamic properties of THPP aged under various humidity environments were identified through thermal analysis and surface analysis. First, a considerable amount of cracks on the surface of the oxidant was found in the aged THPPs. Particularly, when the humidity level increased, the number and length of the cracks rapidly increased. Also, the deterioration of Viton was found only in the thermally aged sample whereas the oxidation of the fuel was more pronounced in the hygrothermally aged samples. The extracted kinetic parameters of THPP on the reaction progress vary greatly by the humidity level, indicating that moisture significantly changes the performance and combustion reaction of THPP, which may eventually result in a reduced lifespan.

Viability Determination of Pinus rigida Seeds Using Artificially Accelerated Aging (노화처리를 이용한 리기다소나무 종자의 활력 평가)

  • Han, Sim-Hee;Koo, Yeong-Bon;Kim, Chan-Soo;Oh, Chang-Young;Song, Jeong-Ho
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.8 no.1
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    • pp.10-14
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    • 2006
  • We tested the seed viability of Pinus rigida using accelerated aging to discover optimum times and temperatures far artificially accelerated aging. Seeds were artificially aged at different temperatures and during different tines. The seed viability was affected by the accelerated aging and by temperature with a decline in germination and seed vigor. The aging index of P. rigida seed was 0.31 at $35^{\circ}C$ and seed viability was nearly lost after aging treatment at $40^{\circ}C$ for 15 days. The optimum temperature of P. rigida far the aging test was decided to be approximately $37^{\circ}C$ on the basis of the aging index. Inorganic materials and conductivity of leaching solution from aging seeds increased with the increase of aging period. The accelerated aging test was considered to be a suitable method to evaluate the seed viability of tree species. Because seed characters are much different among tree species, however, more studies need to be done to discover the optimum conditions for aging by tree species.

Gender Difference of the Influencing Factors on Successful Aging among Rural Community-dwelling Korean Elders (남성노인과 여성노인의 성공적 노화 영향요인)

  • Kim, Hee Kyung
    • 한국노년학
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    • v.32 no.3
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    • pp.819-834
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    • 2012
  • The purpose of this study was to examine the degree of successful aging and to investigate influencing factors of it in elderly to types of gender. Subjects were 73 male elderly and 77 female elderly, total 150 elderly living at K city in C province, from May to June, 2012. The data were analyzed using the SPSS Win 18.0 program for $X^2$ test, t-test, Pearson's correlation coefficients and multiple regression analysis. The correlated factors of successful aging among male elders included life satisfaction(r=.525, p<.001), family support(r=.355, p=.004), depression(r=-.555, p<.001) and loneliness(r=-.437, p<.001). Those of successful aging among female elders included life satisfaction(r=.607, p<.001), leisure satisfaction(r=.679, p<.001), family support(r=.784, p<.001), depression(r=-.516, p<.001), loneliness(r=-.644, p<.001) and self-transcendence(r=.576, p<.001). Life satisfaction and depression were statistically significant influencing factors of successful aging in male elders. Especially in the cases of female elders, life satisfaction, depression, family support and self-transcendence affected to successful aging. Life satisfaction, depression, family support, and self-transcendence were explained 52.9% in perception of successful aging among elders. This study suggests that life satisfaction, depression, family support, and self-transcendence will be considered in enhancing the successful aging promoting care and welfare designed for types of gender.