分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-04-06
摘要: It is generally difficult to predict the cell structure foamed from a binary polymer blend compared to a single polymer, as many factors in polymer blends add to the complexity of the foaming process without easy control, such as blend morphology, blend v
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-04-06
摘要: As the main component of the tire treads, styrene butadiene rubber (SBR) is widely used to make tire tread for cars in the rubber industry; understanding the friction and wear properties of tire tread rubber is important to improve the safety of the cars.
分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-12
摘要: p53 is an important tumor suppressor and stress response mediator. Proper control of p53 level and activity is tightly associated with its function. Posttranslational modifications and the interactions with Mdm2 and Mdm4 are major mechanisms controlling p53 activity and stability. As p53 protein is short-lived and hardly detectable in unstressed situations, less is known on its basal level expression and the corresponding controlling mechanisms in vivo. In addition, it also remains obscure how p53 expression might contribute to its functional regulation. In this study, we established bacterial artificial chromosome transgenic E.coli beta-galactosidase Z gene reporter mice to monitor p53 expression in mouse tissues and identify important regulatory elements critical for the expression in vivo. We revealed preferentially high level of p53 reporter expressions in the proliferating, but not the differentiated compartments of the majority of tissues during development and tissue homeostasis. In addition, tumors as well as regenerating tissues in the p53 reporter mice also expressed high level of beta-gal. Furthermore, both the enhancer box sequence (CANNTG) in the p53 promoter and the 3' terminal untranslated region element were critical in mediating the high-level expression of the reporter. We also provided evidence that cellular myelocytomatosis oncogene was a critical player regulating p53 mRNA expression in proliferating cells and tissues. Finally, we found robust p53 activation preferentially in the proliferating compartment of mouse tissues upon DNA damage and the proliferating cells exhibited an enhanced p53 response as compared with cells in a quiescent state. Together, these results suggested a highly regulated expression pattern of p53 in the proliferating compartment controlled by both transcriptional and posttranscriptional mechanisms, and such regulated p53 expression may impose functional significance upon stress by setting up a precautionary mode in defense of cellular transformation and tumorigenesis.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Two series of poly(ester imide)s derived from bis(trimellitic acid anhydride) phenyl ester (TAHQ) and bis[(3,4- dicarboxylic anhydride) phenyl] terephthalate (PAHP), as well as poly(ether imide)s based on hydroquinone diphthalic anhydride (HQDPA), were synthesized with aromatic diamines via solution polycondensation. These polyimide films were transparent with an ultraviolet-visible absorption cut-off wavelength below 375 nm, and with tensile strengths of 42.0–83.8 MPa, tensile moduli of 2.5–4.7 GPa and elongations at break of 2.1–5.4%. Compared with the poly(ether imide)s, the poly(ester imide)s showed higher glass transition temperatures (Tg), lower water absorption (WA) and lower temperature of 5% weight loss (Td5%). Moreover, the poly(ester imide)s derived from PAHP with a low electron affinity of 2.04 eV by theoretical calculation achieved better transparency, lower WA and slightly lower Tg than the corresponding TAHQ- based poly(ester imide)s.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this paper, we present a systematic investigation on the shape memory/change effect in a double network nanocomposite tough hydrogel. Water-content dependency of the response of this hydrogel to heating and wetting by water is confirmed. Since this hydrogel is tough (even after being fully wetted in water) and has a relatively lower swelling ratio, apart from conventional shape memory/change effect as in ordinary hydrogels, additional features have been realized. These features include heating induced shape memory effect utilizing the absorbed water as the transition component, mechano-responsive shape change effect after water wetting and water-induced shape memory effect.