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71.
The effect of clay content, homogenization RPM, and pH on the mechanical and barrier properties of fish gelatin/nanoclay composite films was investigated. The addition of 5% nanoclay (w/w) increased the tensile strength from 30.31 ± 2.37 MPa to 40.71 ± 3.30 MPa. The 9 g clay/100 g gelatin film exhibited the largest improvements in oxygen and water barrier properties. Oxygen permeability decreased from 402.8 × 10−6 ± 0.7 × 10−6 g m/m2 day atm to 114.4 × 10−6 ± 16.2 × 10−6 g m/m2 day atm and the water vapor permeability decreased from 31.2 × 10−3 ± 1.6 × 10−3 ng m/m2 s Pa to 8.1 × 10−3 ± 0.1 × 10−3 ng m/m2 s Pa. The XRD and TEM observation suggested that the ultrasonication treatment (30 min at 40% output) resulted in exfoliation of the silicates. 相似文献
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73.
An important issue concerning the use of soft contact lenses is comfort, which, among other factors, has been related to the
level of friction between the anterior side of the lens and the inner eyelid. Although several studies have been carried out
to investigate the frictional properties of contact lenses, these have not taken the physiological environment of the eye
into account. In use, lenses are in contact with proteins present in tears, with corneal cells and with the palpebral conjunctiva
(clear membrane on inner eyelid). The focus of this study was to establish a biologically relevant measurement protocol for
the investigation of friction of contact lenses that would mimic the eye’s physiological environment. By optimizing parameters
such as the composition of the friction counter surface, the lubricant solution, the normal load and the velocity, an ideal
protocol and setup for microtribological testing could be established and used to perform a comparative study of various commercially
available soft contact lenses. 相似文献
74.
R. C. Nelson D. A. Sergatskov R. V. Duncan 《Journal of Low Temperature Physics》2002,126(1-2):649-654
Measurements of the magnetic sensitivity of thin sputtered films of PdMn alloy demonstrate the viability of this material for high resolution thermometry. The thinnest films (thickness 1.0 m) show significant domain scale noise below the Curie Temperature, Tc, while thicker films (thickness 10 m) show reliable non-hysteretic behavior throughout the temperature range of interest. The thin films show the effects of demagnetization with the field perpendicular to the surface, but a fine screen in this orientation shows good response with no evidence of saturation and a manageable degree of demagnetization. 相似文献
75.
G. Stanley Hall influenced several social movements that had great implications for child wellbeing: the Child Study, Parent Education, and Child Welfare Movements. However, while Hall laid much of the foundation for the field of scientific child study and policy-relevant research, his legacy is virtually nonexistent. The current article reviews the life and contributions of G. Stanley Hall, and the dual role Hall played in history as a revered leader of the Child Study Movement and a controversial figure in the landscape of early child psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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77.
An improved approach to updating the electric field in simulations of Coulomb gases using the local lattice technique introduced by Maggs and Rossetto [A.C. Maggs, V. Rossetto, Phys. Rev. Lett. 88 (2002) 196402] is described and tested. Using the Fast Fourier Transform (FFT) an independent configuration of electric fields subject to Gauss' law constraint can be generated in a single update step. This FFT based method is shown to outperform previous approaches to updating the electric field in the simulation of a basic test problem in electrostatics of strongly correlated systems. 相似文献
78.
Point-tracked quantitative analysis of left ventricular surface motion from 3-D image sequences 总被引:1,自引:0,他引:1
Shi P Sinusas AJ Constable RT Ritman E Duncan JS 《IEEE transactions on medical imaging》2000,19(1):36-50
We propose and validate the hypothesis that we can use differential shape properties of the myocardial surfaces to recover dense field motion from standard three-dimensional (3-D) image sequences (MRI and CT). Quantitative measures of left ventricular regional function can be further inferred from the point correspondence maps. The noninvasive, algorithm-derived results are validated on two levels. First, the motion trajectories are compared to those of implanted imaging-opaque markers of a canine model in two imaging modalities, where subpixel accuracy is achieved. Second, the validity of using motion parameters (path length and thickness changes) for detecting myocardial injury area is tested by comparing algorithms derived results to postmortem analysis TTC staining of myocardial tissue, where the achieved Pearson product-moment correlation value is 0.968. 相似文献
79.
T Skarzynski DH Kim WJ Lees CT Walsh K Duncan 《Canadian Metallurgical Quarterly》1998,37(8):2572-2577
MurA (UDP-GlcNAc enolpyruvyl transferase), the first enzyme in bacterial peptidoglycan biosynthesis, catalyzes the enolpyruvyl transfer from phosphoenolpyruvate (PEP) to the 3'-OH of UDP-GlcNAc by an addition-elimination mechanism that proceeds through a tetrahedral ketal intermediate. The crystal structure of the Cys115-to-Ala (C115A) mutant of Escherichia coli MurA complexed with a fluoro analogue of the tetrahedral intermediate revealed the absolute configuration of the adduct and the stereochemical course of the reaction. The fluorinated adduct was generated in a preincubation of wild-type MurA with (Z)-3-fluorophosphoenolpyruvate (FPEP) and UDP-GlcNAc and purified after enzyme denaturation. The fluorine substituent stabilizes the tetrahedral intermediate toward decomposition by a factor of 10(4)-10(6), facilitating manipulation of the adduct. The C115A mutant of MurA was utilized to avoid the microheterogeneity that arises in the wild-type MurA from the attack of Cys115 on C-2 of FPEP in competition with the formation of the fluorinated adduct. The crystal structure of the complex was determined to 2.8 A resolution, and the absolute configuration at C-2 of the adduct was found to be 2R. Thus, addition of the 3'-OH of UDP-GlcNAc is to the 2-si face of FPEP, corresponding to the 2-re face of PEP. Given the previous observation that, in D2O, the addition of D+ to C-3 of PEP proceeds from the 2-si face [Kim, D. H., Lees, W. J., and Walsh, C. T. (1995) J. Am. Chem. Soc. 117, 6380-6381], the addition across the double bond of PEP is anti. Also, because the overall stereochemical course has been shown to be either anti/syn or syn/anti [Lees, W. J., and Walsh, C. T. (1995) J. Am. Chem. Soc. 117, 7329-7337], it now follows that the stereochemistry of elimination of H+ from C-3 and Pi from C-2 of the tetrahedral intermediate of the reaction is syn. 相似文献
80.