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931.
932.
Asha Chaubey Manju Gerard V. S. Singh B. D. Malhotra 《Applied biochemistry and biotechnology》2001,96(1-3):303-311
Tetraethylorthosilicate (TEOS)-derived sol-gel films were utilized for the immobilization of lactate dehydrogenase (LDH) by
physical adsorption and sol-gel/LDH/sol-gel sandwich configuration. An attempt was made to ascertain the optimum pH and temperature
for the immobilized LDH. It was shown that TEOS-derived sol-gel films containing physically adsorbed LDH exhibited linearity
from 0.5 to 4 mM, whereas those containing LDH in sandwich configuration showed linearity from 0.5 to 3 mM
l-lactate. These sol-gel films, immobilized with LDH, were found to be stable for about 4 weeks at 4–10°C. 相似文献
933.
Sunee Srihiranpullop Piyasan Praserthdam Tharathon Mongkhonsi 《Reaction Kinetics and Catalysis Letters》2001,72(1):125-131
The cooperative effect on catalyst deactivation of Pt-based catalysts for dehydrogenation reaction was investigated using the combination of Pt-based/SiO2 and Al2O3. The presence of the effect was confirmed by reaction test, CO adsorption, H2-TPD and TPO. Considering conversion, active site, H2 uptake and the nature and amount of coke, interestingly, the physical mixture of Pt-based catalyst supported on SiO2 with 100-120 mesh and Al2O3 60-80 mesh was similar to Pt-based Al2O3. The concept of combination of two catalytic functions, acidity and metallic species, will certainly provide the possibility of better catalyst design. 相似文献
934.
Xiao Mei LI Ying Hong WANG Mao LIN* Institute of Materia Medica Chinese Academy of Medical Sciences Perking Union Medical College Beijing 《中国化学快报》2001,(7)
Continuous investigation on stilbenoids from the lianas of Gnetum pendulum1 resulted in the isolation of a new dimer, Gnetupendin C (1), a cis-2, 3-dihydrobenzofuran dimer of resveratrol and oxyresveratrol.Gnetupendin C (1) was obtained as yellowish amorphous power, [(] -220.0 (c 0.100, MeOH). UV (c 0.02, MeOH) (max (log (): 222 (4.5), 288 (sh), 310 (sh), 327 (4.4) nm. The high resolution EIMS, m/z 470.1344, agreed with a molecular formula of C28H22O7 (requires 470.1366) and the 1H NM… 相似文献
935.
936.
In this paper, we examine the rheological and the structural properties of different types of gelatin networks, physical, chemical and both. The physical gel is due to the formation of collagen type triple helices when cooling the solutions. Chemically crosslinked gels are obtained with a reagent, in our case the bis(vinylsulfonyl)methane (BVSM), kindly provided by Kodak Industrie (France). Each BVSM molecule provides two covalent bonds. The chemical reaction was followed by microcalorimetry (MicroDSC III from Setaram, Caluire, France). The relation between shear moduli and crosslinking for the three types of gels is discussed, in relation with theoretical models of randomly crosslinked systems. 相似文献
937.
938.
939.
我国大科学工程项目LAMOST巡天计划每观测夜能获取多达数万条天体光谱数据,天文学家通过对天体光谱的分析观察可以获取有效的天文信息用于天文学或天体物理学的研究。而针对海量数据,寻找自动方法分析天体光谱并进行天体各种物理参数的测量就具有重要研究意义和价值。这一课题也吸引了许多学者进行研究,但目前所尝试的算法和相应结果仍然需要进一步改进,针对这一需求深入研究了核岭回归(KRR)方法在恒星大气物理参数(包括有效温度、表面重力和金属丰度)自动测量方面的应用,特别是在我国大科学工程项目LAMOST所释放光谱数据上的应用。核岭回归是岭回归算法的进一步发展,而岭回归是最小二乘方法的一种变形,其具有解决高维多重共线性问题的能力。所以KRR方法适合于处理高维的天体光谱信息,从LAMOST的第五期释放数据中随机选择了2万条被识别为恒星的光谱数据用于实验测试,该数据既包含低信噪比数据,也包含高信噪比数据(g,r,i波段平均信噪比最低至6.7,最高到793)。首先,本文对光谱进行预处理,包括三个步骤:(1)利用小波变换对光谱数据进行去噪处理;(2)因为LAMOST采用的是后期修正的流量定标设计,所以还通过流量归一化来避免部分光谱流量值不准确的问题;(3)由于每条光谱维数高达数千维,利用主成分分析方法(PCA)对光谱进行了降维。然后,利用KRR方法建立了光谱数据和标准化后的三大参数值之间的回归模型。最后,通过设计进行不同的组合实验对KRR算法模型进行了测试分析,并与经典算法支持向量回归(SVR)进行了对比。综合所有实验结果显示KRR方法对应的有效温度、表面重力和金属丰度的测试平均绝对误差分别为82.9897 K,0.1858 dex和0.1211 dex,优于SVR的144.2308 K,0.1886 dex和0.1246 dex。特别是KRR在温度测试结果上有较大优势,由此表明KRR方法能够有效地应用于天体光谱特别是恒星光谱参数的自动测量处理中。 相似文献
940.
The physical aging behavior, time‐dependent densification, of thin polystyrene (PS) films supported on silicon are investigated using ellipsometry for a large range of molecular weights (MWs) from Mw = 97 to 10,100 kg mol?1. We report an unexpected MW dependence to the physical aging rate of h < 80‐nm thick films not present in bulk films, where samples made from ultra‐high MWs ≥ 6500 kg mol?1 exhibit on average a 45% faster aging response at an aging temperature of 40 °C compared with equivalent films made from (merely) high MWs ≤ 3500 kg mol?1. This MW‐dependent difference in physical aging response indicates that the breadth of the gradient in dynamics originating from the free surface in these thin films is diminished for films of ultra‐high MW PS. In contrast, measures of the film‐average glass transition temperature T g(h) and effective average film density (molecular packing) show no corresponding change for the same range of film thicknesses, suggesting physical aging may be more sensitive to differences in dynamical gradients. These results contribute to growing literature reports signaling that chain connectivity and entropy play a subtle, but important role in how glassy dynamics are propagated from interfaces. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1224–1238 相似文献