An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly（α-methylstyrene）（PαMS） chains is studied, in which the effect of large side group...An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly（α-methylstyrene）（PαMS） chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.展开更多
The photodegradation of irradiated thin films of poly (para-methylstyrene) with 265 nm radiations in the presence of airand as a function of irradiation time has been studied using UV-VIS, fluorescence and FT-IR Spect...The photodegradation of irradiated thin films of poly (para-methylstyrene) with 265 nm radiations in the presence of airand as a function of irradiation time has been studied using UV-VIS, fluorescence and FT-IR Spectroscopic techniques. The influence of phthalate and terephthalate plasticizers on stability of poly (para-methylstyrene) towards irradiations was also investigated. Blending with phthalate plasticizers was found to cause a higher efficiency of photodegradation than that obtained in doping with terephthalate plasticizers. The intensity of absorption was also found to increase with time of irradiation and in change in the shape of the spectra at longer wavelength, thus indicating a possibility of photodegradation of polymer chains. The analysis of the FT-IR spectra of the irradiated and non-irradiated samples, shows a predominant absorption associated with carbonyl compounds with 1740 cm-1. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra, have provided an evidence for the photodegradation as well as photo-oxidation of polymeric chains. The presence of the plasticizer in the polymer backbone was found to accelerate the photodegradation of polymeric chains.展开更多
The SHP-A1 type catalyst for hydrogenation of α-methylstyrene(AMS)developed by the SINOPEC Shanghai Petrochemical Research Institute(SPRI)has been successfully applied in the No.1 phenol unit at the Third Chemical Pl...The SHP-A1 type catalyst for hydrogenation of α-methylstyrene(AMS)developed by the SINOPEC Shanghai Petrochemical Research Institute(SPRI)has been successfully applied in the No.1 phenol unit at the Third Chemical Plant of Yanshan Petrochemical Company at the first attempt of commissioning.The said catalyst is the first AMS hydrogenation catalyst developed展开更多
背景:目前运动疗法是非药物治疗腰痛的有效方法,运动疗法可通过骨骼和肌肉之间的机械-化学偶联维持腰椎的稳定,但目前尚无关于运动疗法通过机械-化学偶联缓解慢性非特异性下背痛之间研究进展及最佳治疗方案的明确阐述。目的:综述运动疗...背景:目前运动疗法是非药物治疗腰痛的有效方法,运动疗法可通过骨骼和肌肉之间的机械-化学偶联维持腰椎的稳定,但目前尚无关于运动疗法通过机械-化学偶联缓解慢性非特异性下背痛之间研究进展及最佳治疗方案的明确阐述。目的:综述运动疗法时椎旁肌通过机械-化学偶联影响腰椎稳定性进而缓解慢性非特异性下背痛的相关研究进展,以及目前运动疗法治疗慢性非特异性下背痛的最佳方案。方法:在万方数据库、中国知网、维普、Web of Science和PubMed数据库进行文献检索,以“慢性非特异性下背痛,腰椎稳定,椎旁肌,运动疗法”为中文检索词,以“chronic nonspecific low back pain,lumbar stabilization,paravertebral muscle,exercise therapy”为英文检索词,检索各数据库建库至2024年1月发表的相关文献,最终纳入93篇文献进行归纳总结。结果与结论:运动疗法可以通过适当的机械刺激作用于椎旁肌和骨骼并使其产生相应的变化。运动疗法主要通过机械-化学偶联方式来提高椎旁肌的质量,进而维持腰椎稳定,从而更好地缓解慢性非特异性下背痛,是慢性非特异性下背痛的重要干预措施。但是,对于运动疗法通过腰椎稳定来治疗慢性非特异性下背痛的确切有效方案尚无明确报道。个体化运动方案的制定对于慢性非特异性下背痛的治疗和预后尤为重要。同一个体的肌肉质量与骨骼质量是密切相关的,影像学评估椎旁肌的质量和体积对于疾病的发现和干预具有重要意义。展开更多
背景:阿尔茨海默病患者存在严重的脑能量障碍,近年来基于酮体干预的脑能量拯救策略在阿尔茨海默病的治疗中越来越受到重视。目的:探讨β-羟基丁酸能否改善β淀粉样蛋白1-42(β-amyloid protein 1-42,Aβ_(1-42))诱导的小鼠海马神经元HT2...背景:阿尔茨海默病患者存在严重的脑能量障碍,近年来基于酮体干预的脑能量拯救策略在阿尔茨海默病的治疗中越来越受到重视。目的:探讨β-羟基丁酸能否改善β淀粉样蛋白1-42(β-amyloid protein 1-42,Aβ_(1-42))诱导的小鼠海马神经元HT22细胞能量障碍。方法:将HT22细胞分为4组,分别为对照组、β-羟基丁酸组、Aβ_(1-42)组、Aβ_(1-42)+β-羟基丁酸组。使用相应试剂盒检测HT22细胞的存活率、ATP水平、α-酮戊二酸脱氢酶活性、Na^(+)K^(+)-ATP酶活性、线粒体膜电位及活性氧水平。结果与结论:与对照组相比,Aβ_(1-42)组HT22细胞的存活率、ATP水平、α-酮戊二酸脱氢酶活性、Na^(+)K^(+)-ATP酶活性、线粒体膜电位均显著降低(P<0.05),活性氧水平显著升高(P<0.05)。与Aβ_(1-42)组相比,Aβ_(1-42)+β-羟基丁酸组HT22细胞的存活率、ATP水平、α-酮戊二酸脱氢酶活性、Na^(+)K^(+)-ATP酶活性、线粒体膜电位均显著升高(P<0.05),活性氧水平显著降低(P<0.05)。结果表明:β-羟基丁酸提高了线粒体生物能量功能和细胞存活率,最终改善了Aβ_(1-42)诱导的HT22细胞能量障碍。展开更多
文摘An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly（α-methylstyrene）（PαMS） chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.
文摘The photodegradation of irradiated thin films of poly (para-methylstyrene) with 265 nm radiations in the presence of airand as a function of irradiation time has been studied using UV-VIS, fluorescence and FT-IR Spectroscopic techniques. The influence of phthalate and terephthalate plasticizers on stability of poly (para-methylstyrene) towards irradiations was also investigated. Blending with phthalate plasticizers was found to cause a higher efficiency of photodegradation than that obtained in doping with terephthalate plasticizers. The intensity of absorption was also found to increase with time of irradiation and in change in the shape of the spectra at longer wavelength, thus indicating a possibility of photodegradation of polymer chains. The analysis of the FT-IR spectra of the irradiated and non-irradiated samples, shows a predominant absorption associated with carbonyl compounds with 1740 cm-1. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra, have provided an evidence for the photodegradation as well as photo-oxidation of polymeric chains. The presence of the plasticizer in the polymer backbone was found to accelerate the photodegradation of polymeric chains.
文摘The SHP-A1 type catalyst for hydrogenation of α-methylstyrene(AMS)developed by the SINOPEC Shanghai Petrochemical Research Institute(SPRI)has been successfully applied in the No.1 phenol unit at the Third Chemical Plant of Yanshan Petrochemical Company at the first attempt of commissioning.The said catalyst is the first AMS hydrogenation catalyst developed
文摘背景:目前运动疗法是非药物治疗腰痛的有效方法,运动疗法可通过骨骼和肌肉之间的机械-化学偶联维持腰椎的稳定,但目前尚无关于运动疗法通过机械-化学偶联缓解慢性非特异性下背痛之间研究进展及最佳治疗方案的明确阐述。目的:综述运动疗法时椎旁肌通过机械-化学偶联影响腰椎稳定性进而缓解慢性非特异性下背痛的相关研究进展,以及目前运动疗法治疗慢性非特异性下背痛的最佳方案。方法:在万方数据库、中国知网、维普、Web of Science和PubMed数据库进行文献检索,以“慢性非特异性下背痛,腰椎稳定,椎旁肌,运动疗法”为中文检索词,以“chronic nonspecific low back pain,lumbar stabilization,paravertebral muscle,exercise therapy”为英文检索词,检索各数据库建库至2024年1月发表的相关文献,最终纳入93篇文献进行归纳总结。结果与结论:运动疗法可以通过适当的机械刺激作用于椎旁肌和骨骼并使其产生相应的变化。运动疗法主要通过机械-化学偶联方式来提高椎旁肌的质量,进而维持腰椎稳定,从而更好地缓解慢性非特异性下背痛,是慢性非特异性下背痛的重要干预措施。但是,对于运动疗法通过腰椎稳定来治疗慢性非特异性下背痛的确切有效方案尚无明确报道。个体化运动方案的制定对于慢性非特异性下背痛的治疗和预后尤为重要。同一个体的肌肉质量与骨骼质量是密切相关的,影像学评估椎旁肌的质量和体积对于疾病的发现和干预具有重要意义。
文摘背景:阿尔茨海默病患者存在严重的脑能量障碍,近年来基于酮体干预的脑能量拯救策略在阿尔茨海默病的治疗中越来越受到重视。目的:探讨β-羟基丁酸能否改善β淀粉样蛋白1-42(β-amyloid protein 1-42,Aβ_(1-42))诱导的小鼠海马神经元HT22细胞能量障碍。方法:将HT22细胞分为4组,分别为对照组、β-羟基丁酸组、Aβ_(1-42)组、Aβ_(1-42)+β-羟基丁酸组。使用相应试剂盒检测HT22细胞的存活率、ATP水平、α-酮戊二酸脱氢酶活性、Na^(+)K^(+)-ATP酶活性、线粒体膜电位及活性氧水平。结果与结论:与对照组相比,Aβ_(1-42)组HT22细胞的存活率、ATP水平、α-酮戊二酸脱氢酶活性、Na^(+)K^(+)-ATP酶活性、线粒体膜电位均显著降低(P<0.05),活性氧水平显著升高(P<0.05)。与Aβ_(1-42)组相比,Aβ_(1-42)+β-羟基丁酸组HT22细胞的存活率、ATP水平、α-酮戊二酸脱氢酶活性、Na^(+)K^(+)-ATP酶活性、线粒体膜电位均显著升高(P<0.05),活性氧水平显著降低(P<0.05)。结果表明:β-羟基丁酸提高了线粒体生物能量功能和细胞存活率,最终改善了Aβ_(1-42)诱导的HT22细胞能量障碍。
