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381.
382.
Irwin A. Wiehe 《Journal of Dispersion Science and Technology》2013,34(3):431-435
The value of the average molecular weight of petroleum asphaltenes continues to be controversial. Usually the disagreement is about the measurement of a single asphaltene fraction when the need is for a consistent picture that comprises all fractions of petroleum and includes chemical changes during processing. By using one of the better solvents for carbonaceous materials, o‐dichlorobenzene, at the maximum instrument temperature, vapor pressure osmometry provides a consistent measurement of number average molecular weight not achieved by any other technique. This average molecular weight is consistent among petroleum fractions and gives predictable changes in asphaltene molecular weight with thermal processing. 相似文献
383.
Martin JJ Cardamone JM Irwin PL Brown EM 《Colloids and surfaces. B, Biointerfaces》2011,88(1):354-361
We report for the first time the stabilization of silver nanoparticles in good yield, average diameter 3.5 nm, using wool keratin hydrolysates as stabilizers. The nanoparticles are extremely stable as a suspension and can be lyophilized into a powder and easily reconstituted in solvent with no change in spectral properties relative to the initial suspension. The nanoparticles interact with nitrogen and oxygen moieties of the keratin hydrolysates under the pH conditions used in the synthesis and appear to act as cross-linkers between adjacent chains. The product has excellent handling properties which we believe will make it a very attractive biocompatible coating/additive, providing prolonged antimicrobial efficacy to a wide variety of products such as textiles, plastics, paints, orthopedic devices and others. 相似文献
384.
The preservation of static balance in both upright- and hand-stance is maintained by the projection of center of mass (CM) motion within the region of stability at the respective base of support. This study investigated, from a degrees of freedom (DF) perspective, whether the stability of the CM in both upright- and hand-stances was predicted by the respective dispersion and time-dependent regularity of joint (upright stance—ankle, knee, hip, shoulder, neck; hand stance—wrist, elbow, shoulder, neck) angle and position. Full body three-dimensional (3D) kinematic data were collected on 10 advanced level junior female gymnasts during 30 s floor upright- and hand-stands. For both stances the amount of the dispersion of joint angle and sway motion was higher than that of the CM and center of pressure (CP) with an inverse relation to time-dependent irregularity (SampEn). In upright-standing the variability of neck motion in the anterior–posterior direction was significantly greater than that of most joints consistent with the role of vision in the control of quiet upright posture. The findings support the proposition that there are both task specific and general properties to the global CM control strategy in the balance of upright- and hand-standing induced by the different active skeletal-muscular organization and the degeneracy revealed in the multiple distributional variability patterns of the joint angle and position in 3D. 相似文献