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31.
32.
The antibiotic activity of sulbenicillin and cefacetrile was determined after storage at -20 degrees C for up to 7 days in human gall-bladder and common duct bile. In gall-bladder bile, both drugs could not retain their initial activity after 3 days. The decay curves in antibiotic activity in the ductal bile revealed large variations, as given in Figs. 5 and 6. The 7th day activity of both drugs decreased with the rise in initial pH level of bile. Significant correlation was noted between bile acid concentration in bile and cefacetrile activity on the 7th day. 相似文献
33.
The synthesis of poly(lactic acid) through polycondensation of the lactic acid monomer gave weight average molecular weights (Mw) lower than 1.6 x 10(4), whereas ring-opening polymerization of lactides in bulk at 130 degrees C for 72 h using stannous octoate as catalyst in the concentration range from 0.003 to 0.8 wt% produced polylactides with viscosity average molecular weight (Mv) ranging from 2 x 10(4) to 6.8 x 10(5). The monomer conversion and Mv showed a maximum at a catalyst concentration around 0.05 wt%. The monomer conversion and Mv increased almost linearly with polymerization time up to a monomer conversion of 80%, but both the conversion and Mv decreased after passing through a maximum, when the polymerization reaction was allowed to proceed for longer periods of time. This time dependence was pronounced at higher polymerization temperatures. The decrease in Mv at prolonged polymerization and higher polymerization temperatures was attributed to thermal depolymerization of resultant polylactides, but no significant optical rotation of poly(L-lactide) was noticed. 相似文献
34.
35.
This study suggests an approach to investment risk analysis which provides a useful complement to more detailed analyses. The analyst specifies an appropriate distribution of cash flows and associated utility function from one of the four models suggested. Next, the risk adjusted present value of the investment stream is calculated using the simplified procedure outlined in the paper. Sensitivity analysis is then performed on the results to determine whether a more extensive analysis of the decision maker's risk preferences is called for. 相似文献
36.
Hyon Kook Myong 《Journal of Mechanical Science and Technology》2012,26(5):1347-1354
Two-dimensional multiphase flows with material interface due to density difference are numerically simulated on an unstructured grid system by a Navier-Stokes solver developed by Myong and Kim (2006), since numerical computation for these flows is still known to be difficult, especially if the interface separates fluids of large different densities. This solver employs an unstructured cell-centered method based on a conservative pressure-based finite volume method, since the unstructured grid approach makes the solver very flexible in dealing with complex boundaries, and adopts a high resolution method (CICSAM) in a volume of fluid (VOF) scheme for the accurate phase interface capturing. The test cases are the Rayleigh-Taylor instability (density ratio of 2), the oil bubble rising in a partially filled container (density ratio of 2), the air bubble rising in a fully filled container with bubble shedding (density ratio of 100) and the droplet splash (density ratio of about 1000), which are typical benchmark problems among multiphase flows with material interface due to density difference. The present results are compared with other numerical solutions found in the literature. The present method (solver) efficiently and accurately simulates complex interface flows such as multiphase flows with material interface due to both density difference and instability. 相似文献
37.
Yong Il Park Jeong Hyun Kim Kang Taek Lee Ki‐Seok Jeon Hyon Bin Na Jung Ho Yu Hyung Min Kim Nohyun Lee Seung Hong Choi Sung‐Il Baik Hyoungsu Kim Seung Pyo Park Beom‐Jin Park Young Woon Kim Sung Ho Lee Soo‐Young Yoon In Chan Song Woo Kyung Moon Yung Doug Suh Taeghwan Hyeon 《Advanced materials (Deerfield Beach, Fla.)》2009,21(44):4467-4471
38.
Park Hye-Jung Kim Ji-Youn Kim Hee Sook Lee Sang-Hyeon Jang Jeong Su Lee Mun Hyon 《Food science and biotechnology》2019,28(3):881-893
Food Science and Biotechnology - Commonly consumed fruit juices possess low inhibitory activity of angiotensin I-converting enzyme (ACE), which plays central role in elevation of blood pressure.... 相似文献
39.
Thermal characterization of polylactides 总被引:12,自引:0,他引:12
Three important thermal characteristics of polylactides have been measured and discussed. These are glass transition temperature, melting temperature, and degradation behaviour. The glass transition temperatures at infinite molecular weight for
- and
-optical isomers were 58 and 57°C, respectively. Melting temperature for the crystalline
-isomer was 184°C at infinite molecular weight. Number-average molecular weight, melt viscosity, differential scanning calorimetry, infra-red analysis and thermogravimetric analysis were used to study the degradation behaviour under different conditions. Polylactides were found to be highly sensitive to heat, especially at temperatures higher than 190°C. Most of the degradative reactions were thought to involve the highly concentrated ester bond on the main chain. These reactions included thermohydrolysis, depolymerization and cyclic oligomerization, intermolecular and intramolecular transesterifications. Low molecular weight compounds associated with the polymer seemed to play an important role in lowering the molecular weight at high temperatures, as well as the hydroxyl end group of the main chain. The compounds include water, monomers, oligomers, and polymerization catalysts. Removal of the non-polymeric contents and blocking the hydroxyl end-group enhanced the thermal stability of the polymers. The increased amount of the polymerization catalyst in the end product contributed to the degradative reactions. 相似文献
40.
Moon Il Kim Jungbae Kim Jinwoo Lee Sujeong Shin Hyon Bin Na Taeghwan Hyeon Hyun Gyu Park Ho Nam Chang 《Microporous and mesoporous materials》2008,111(1-3):18-23
α-Chymotrypsin (CT) and lipase (LP) were immobilized in SBA-15 mesoporous silica by crosslinking adsorbed enzymes. This simple approach resulted in one-dimensional crosslinked enzyme aggregates (CLEAs) in the linear pore channels of SBA-15, which was very effective in preventing the enzyme leaching and consequently improving the enzyme stability. Both CLEAs of CT and LP showed negligible activity decrease under harsh shaking condition for one week while the conventional approaches including adsorption and covalent attachment resulted in more than 50–90% enzyme inactivation under the same condition. This effective stabilization results from the bent pore structure of SBA-15 with a high aspect ratio, which prevents the leaching of one-dimensional CLEAs and thereby achieves the higher enzyme loading capacity. Along with the higher specific activity than that of adsorbed enzymes, this CLEA approach is much simpler than that of covalent attachment by obviating the tedious processes for silica functionalization and enzyme attachment. 相似文献