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511.
Conditions for conducting excipient compatibility studies via isothermal microcalorimetry were explored using model reactions. The resulting recommended procedure for rapid and practical screening consisted of using binary mixtures (100 mg of each component), the addition of 20% (w/w) water, and monitoring the mixture at 50°C for 3 days using an isothermal microcalorimeter. The correlation between calorimetric excipient compatibility results and formulation stability was investigated for two developmental drugs. A comparison of calorimetric results to actual formulation stability suggested that it was possible to predict relative stability within functional classes. However, caution should be exercised in such predictions, because apparent reaction enthalpies were found to vary three-fold among excipients in the same functional class. Based on these observations, a two-step procedure is suggested for efficient development of stable formulations. First, excipient compatibility screening should be conducted using a rapid calorimetric technique. The calorimetric results are then used to evaluate relative risk of incompatibility for each excipient within a particular functional class. The calorimetric data and the functional requirements of the dosage form are then integrated in developing a limited number of model formulations that are likely to succeed from both a performance and a stability perspective. The second step of the process is to conduct traditional HPLC-based accelerated stability studies on the limited number of model formulations. 相似文献
512.
细胞相容性聚氨酯的合成及其细胞相容性研究 总被引:6,自引:0,他引:6
在紫外光和过氧化氢的共同作用下,过氧化氢基团被引人到聚氨酯膜(PU)表面.将丙烯酸羟乙酯(HEA)吸附于氧化后的PU膜表面,在紫外光下实现了膜表面的接枝,并考察了接枝膜的表面性能.人体脐带静脉内皮细胞粘附和生长的研究表明,HEA接枝后的PU表面细胞粘附率显著提高,细胞的生长速率加快,增值率提高. 相似文献
513.
Tsutomu Takeichi Tarek Agag Rachib Zeidam 《Journal of polymer science. Part A, Polymer chemistry》2001,39(15):2633-2641
Benzoxazine monomer (Ba) was blended with soluble poly(imide‐siloxane)s in various weight ratios. The soluble poly(imide‐siloxane)s with and without pendent phenolic groups were prepared from the reaction of 2,2′‐bis(3,4‐dicarboxylphenyl)hexafluoropropane dianhydride with α,ω‐bis(aminopropyl)dimethylsiloxane oligomer (PDMS; molecular weight = 5000) and 3,3′‐dihydroxybenzidine (with OH group) or 4,4′‐diaminodiphenyl ether (without OH group). The onset and maximum of the exotherm due to the ring‐opening polymerization for the pristine Ba appeared on differential scanning calorimetry curves around 200 and 240 °C, respectively. In the presence of poly(imide‐siloxane)s, the exothermic temperatures were lowered: the onset to 130–140 °C and the maximum to 210–220 °C. The exotherm due to the benzoxazine polymerization disappeared after curing at 240 °C for 1 h. Viscoelastic measurements of the cured blends containing poly(imide‐siloxane) with OH functionality showed two glass‐transition temperatures (Tg's), at a low temperature around ?55 °C and at a high temperature around 250–300 °C, displaying phase separation between PDMS and the combined phase consisting of polyimide and polybenzoxazine (PBa) components due to the formation of AB‐crosslinked polymer. For the blends containing poly(imide‐siloxane) without OH functionalities, however, in addition to the Tg due to PDMS, two Tg's were observed in high‐temperature ranges, 230–260 and 300–350 °C, indicating further phase separation between the polyimide and PBa components due to the formation of semi‐interpenetrating networks. In both cases, Tg increased with increasing poly(imide‐siloxane) content. Tensile measurements showed that the toughness of PBa was enhanced by the addition of poly(imide‐siloxane). Thermogravimetric analysis showed that the thermal stability of PBa also was enhanced by the addition of poly(imide‐siloxane). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2633–2641, 2001 相似文献
514.
515.
何济位 《浙江大学学报(理学版)》2003,30(1):7-11,18
设H既是一个代数,同时又是一个余代数(不必是双代数),证明了当模HM和余模M^H满足适当条件时,H为Hopf代数,并且HM^H为Hopf模;在一般的情况下,若H是双代数,则可以构作H的商双代数-↑H,使M成为-↑H上的Hopf模,另外,从已知的双代数出发,可以构造新的Pentagon方程的解。 相似文献
516.
锡青铜网增强锡青铜基自润滑复合材料的机械和摩擦学性能研究 总被引:4,自引:2,他引:4
采用粉末冶金工艺制备了锡青铜网增强的锡青铜基自润滑复合材料,考察了锡青铜网对复合材料机械性能和摩擦学性能的影响.研究表明:锡青铜网对研制材料的增强作用主要是由于锡青铜网与基体界面相容性良好,热膨胀系数相近,界面结合强度高,从而减少了增强体与基体之间的裂纹或空隙,且网状金属丝间的筋结与支撑提高了材料的断裂能所致;加入一定量的金属网片提高了材料的耐磨性,但金属网片含量过高会导致转移膜的破坏,从而增大摩擦系数,降低复合材料的强度和耐磨性能. 相似文献
517.
Chifei Wu Tada‐Aki Yamagishi Yoshiaki Nakamoto Shin‐Ichiro Ishida Koh‐Hei Nitta 《Journal of Polymer Science.Polymer Physics》2000,38(22):2943-2953
The influences of the molecular weight and chlorine content of chlorinated polyethylene (CPE) on the dynamic mechanical propertiesof an organic hybrid consisting of CPE and 3,9‐bis[1,1‐dimethyl‐2{β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy}ethyl]‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) were investigated. All CPE/AO‐80 hybrids clearly exhibited two kinds of relaxations, and their magnitudes varied according to the molecular weight and chlorine content of CPE. This was due to a change in the ratio of AO‐80 molecules dispersed in the CPE‐rich domain and the AO‐80‐rich domain. A comparison of the jump intensity in differential scanning calorimetry curves with the maximum value of the second tan δ peak demonstrated that the second relaxation was caused by the dissociation of intermolecular hydrogen bonding within the AO‐80‐rich domain. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2943–2953, 2000 相似文献
518.
The miscibility of polycarbonate PC and poly(butylene terephthalate) PBT is controversially discussed in the literature. Partial miscibility has been generally found in melt blends of the two polymers. However, in solution cast blends they were found to be immiscible. It is known that the transesterification takes place in the melt. Copolyesters formed by the transesterification change the compatibility of PC and PBT. In this work PC/PBT melt blends of various composition were investigated in dependence on the copolyester content by means of DSC and NMR. It can be shown that the time regime of the thermal treatment in the melt determines the transesterification degree. The PBT crystallization behavior is strongly influenced by both the PC and copolyester content. The glass transition temperatures of the PBT-rich and PC-rich phase approach each other with the increasing copolyester content. The analysis of the glass transition behavior permits the conclusion that PC and PBT are inherently immiscible provided that the copolyester content is exactly zero. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2161–2168, 1997 相似文献
519.
520.
Yuyan Guo Tao Gao Chuncheng Li Qiaoxin Guo Shuang Sun Dayu Yang Fang Fang Shaowa Lü 《Biomedical chromatography : BMC》2022,36(5):e5321
To evaluate the detoxification effect of a combination of Radix Glycyrrhizae (GU) and Semen Strychni (SN) from toxicokinetics and drug tissue distribution perspectives, decoctions of processed SN and codecoction of SN and GU (SGN) were prepared, and an HPLC-ESI-MS/MS method was developed to monitor the severe exposure level in 1-month toxicokinetics and tissue distribution experiments to detect brucine and strychnine in rats. The toxicokinetic characteristics and tissue distribution before and after the addition of GU were analyzed. The method was successfully applied to evaluate the toxicokinetics and tissue distribution before and after the combination of SN and GU. The results show that GU decreased the blood concentration of toxic components in SN, and a double peak was observed in the drug time curve. The results of tissue distribution show that a combination of GU and SN significantly decreased the accumulation of toxic substances in metabolic organs and accelerated the clearance of toxic substances in the brain. These results provide a reference for the toxicity reduction mechanism of GU combined with SN. 相似文献