To compare the suitable working conditions of polypropylene(PP)and polycaprolactam(PA6)materials in actual use in automobiles,the effects of different temperature aging and different reagents on the mechanical propert...To compare the suitable working conditions of polypropylene(PP)and polycaprolactam(PA6)materials in actual use in automobiles,the effects of different temperature aging and different reagents on the mechanical properties of the two materials,such as tensile,bending,compression,and impact were studied.The results indicate that the short⁃term low⁃temperature environment had no much effect on the mechanical properties of PP and PA6.After long⁃term thermal aging at 80℃,the strength of PP and PA6 increased while their toughness decreased.After short⁃term thermal aging at 120℃,PP strength decreases and toughness increases,while PA6 strength increases and toughness decreases.The soaking of glass water and car shampoo had no much effect on the mechanical properties of PP,but had a significant impact on the mechanical properties of PA6.With the increase of soaking time,the strength of PA6 significantly decreases and the toughness significantly increases.The soaking of 95#gasoline had no much effect on the mechanical properties of PA6,but has a significant impact on the mechanical properties of PP.After 720 h of soaking,the retention rates of the tensile strength,bending strength,and compressive strength of PP were all less than 80%,while the retention rate of the impact strength of the cantilever beam was 160.4%.展开更多
Nowadays,it is clear that adult stem cells,also called as tissue stem cells,play a central role to repair and maintain the tissue in which they reside by their selfrenewal ability and capacity of differentiating into ...Nowadays,it is clear that adult stem cells,also called as tissue stem cells,play a central role to repair and maintain the tissue in which they reside by their selfrenewal ability and capacity of differentiating into distinct and specialized cells.As stem cells age,their renewal ability declines and their capacity to maintain organ homeostasis and regeneration is impaired.From a molecular perspective,these changes in stem cells properties can be due to several types of cell intrinsic injury and DNA aberrant alteration(i.e epigenomic profile)as well as changes in the tissue microenviroment,both into the niche and by systemic circulating factors.Strikingly,it has been suggested that aging-induced deterioration of stem cell functions may play a key role in the pathophysiology of the various agingassociated disorders.Therefore,understanding how resident stem cell age and affects near and distant tissues is fundamental.Here,we examine the current knowledge about aging mechanisms in several kinds of adult stem cells under physiological and pathological conditions and the principal aging-related changes in number,function and phenotype that determine the loss of tissue renewal properties.Furthermore,we examine the possible cell rejuvenation strategies.Stem cell rejuvenation may reverse the aging phenotype and the discovery of effective methods for inducing and differentiating pluripotent stem cells for cell replacement therapies could open up new possibilities for treating age-related diseases.展开更多
文摘To compare the suitable working conditions of polypropylene(PP)and polycaprolactam(PA6)materials in actual use in automobiles,the effects of different temperature aging and different reagents on the mechanical properties of the two materials,such as tensile,bending,compression,and impact were studied.The results indicate that the short⁃term low⁃temperature environment had no much effect on the mechanical properties of PP and PA6.After long⁃term thermal aging at 80℃,the strength of PP and PA6 increased while their toughness decreased.After short⁃term thermal aging at 120℃,PP strength decreases and toughness increases,while PA6 strength increases and toughness decreases.The soaking of glass water and car shampoo had no much effect on the mechanical properties of PP,but had a significant impact on the mechanical properties of PA6.With the increase of soaking time,the strength of PA6 significantly decreases and the toughness significantly increases.The soaking of 95#gasoline had no much effect on the mechanical properties of PA6,but has a significant impact on the mechanical properties of PP.After 720 h of soaking,the retention rates of the tensile strength,bending strength,and compressive strength of PP were all less than 80%,while the retention rate of the impact strength of the cantilever beam was 160.4%.
文摘Nowadays,it is clear that adult stem cells,also called as tissue stem cells,play a central role to repair and maintain the tissue in which they reside by their selfrenewal ability and capacity of differentiating into distinct and specialized cells.As stem cells age,their renewal ability declines and their capacity to maintain organ homeostasis and regeneration is impaired.From a molecular perspective,these changes in stem cells properties can be due to several types of cell intrinsic injury and DNA aberrant alteration(i.e epigenomic profile)as well as changes in the tissue microenviroment,both into the niche and by systemic circulating factors.Strikingly,it has been suggested that aging-induced deterioration of stem cell functions may play a key role in the pathophysiology of the various agingassociated disorders.Therefore,understanding how resident stem cell age and affects near and distant tissues is fundamental.Here,we examine the current knowledge about aging mechanisms in several kinds of adult stem cells under physiological and pathological conditions and the principal aging-related changes in number,function and phenotype that determine the loss of tissue renewal properties.Furthermore,we examine the possible cell rejuvenation strategies.Stem cell rejuvenation may reverse the aging phenotype and the discovery of effective methods for inducing and differentiating pluripotent stem cells for cell replacement therapies could open up new possibilities for treating age-related diseases.
