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排序方式: 共有164条查询结果,搜索用时 132 毫秒
161.
CM Kube H Du G Ghoshal JA Turner 《The Journal of the Acoustical Society of America》2012,132(1):EL43-EL48
In this article, the effects of uniaxial compressive loading on the ultrasonic scattering from polycrystalline grains are shown for 10 MHz ultrasound in annealed, 1018 steel. The results show a decreasing value of the stress-dependent backscatter coefficient for normal incident ultrasound when the compression loading is perpendicular to the scattering direction. The change due to scattering is about 2 orders of magnitude greater than changes observed by others using ultrasonic wavespeed measurements. It is anticipated that this research can serve as the basis for many methods associated with nondestructive determination of stress in structural materials. 相似文献
162.
Ultrasonic attenuation is important not only as a parameter for characterizing tissue but also for compensating other parameters that are used to classify tissues. Several techniques have been explored for estimating ultrasonic attenuation from backscattered signals. In the present study, a technique is developed to estimate the local ultrasonic attenuation coefficient by analyzing the time domain backscattered signal. The proposed method incorporates an objective function that combines the diffraction pattern of the source/receiver with the attenuation slope in an integral equation. The technique was assessed through simulations and validated through experiments with a tissue mimicking phantom and fresh rabbit liver samples. The attenuation values estimated using the proposed technique were compared with the attenuation estimated using insertion loss measurements. For a data block size of 15 pulse lengths axially and 15 beamwidths laterally, the mean attenuation estimates from the tissue mimicking phantoms were within 10% of the estimates using insertion loss measurements. With a data block size of 20 pulse lengths axially and 20 beamwidths laterally, the error in the attenuation values estimated from the liver samples were within 10% of the attenuation values estimated from the insertion loss measurements. 相似文献
163.
γ-Secretase (Gamma Secretase) is a potential drug target in Alzheimer's disease therapeutics. A sequel lead design study was undertaken on a series of bicyclononanes with an aim of identifying potent isofunctional chemotypes. Fragment-based bioisosteric replacement, which considers shape, chemistry, and electrostatics was carried out to mine over four million medicinally relevant fragments of Brood database. The resulting subset, thus, obtained was further mined using consensus QSAR developed from 2D and CoMFA, CoMSIA, GRIND (3D) QSAR predicted endpoints with superior statistical results. The employed consensus prediction and the predicted endpoint values were found to be in good agreement with the experimental values. The predictive ability of the generated model was validated using different statistical metrics, and similarity-based coverage estimation was carried out to define applicability boundaries. Few analogs designed, using the concept of bioisosterism, were found to be promising and could be considered for synthesis and subsequent screening. 相似文献
164.
Avnesh Kumari Sudesh Kumar Yadav Yogesh B. Pakade Vineet Kumar Bikram Singh Abha Chaudhary Subhash Chandra Yadav 《Colloids and surfaces. B, Biointerfaces》2011,82(1):224-232
The plant isolated antioxidant quercitrin has been encapsulated on poly-d,l-lactide (PLA) nanoparticles by solvent evaporation method to improve the solubility, permeability and stability of this molecule. The size of quercitrin-PLA nanoparticles is 250 ± 68 nm whereas that PLA nanoparticles is 195 ± 55 nm. The encapsulation efficiency of nanoencapsulated quercitrin evaluated by HPLC and antioxidant assay is 40%. The in vitro release kinetics of quercitrin under physiological condition reveals initial burst release followed by sustained release. Less fluorescence quenching is observed with equimolar concentration of PLA encapsulated quercitrin than free quercitrin. The presence of quercitrin specific peaks on FTIR of five times washed quercitrin loaded PLA nanoparticles provides an extra evidence for the encapsulation of quercitrin into PLA nanoparticles. These properties of quercitrin nanomedicine provide a new potential for the use of such less useful highly active antioxidant molecule towards the development of better therapeutic for intestinal anti-inflammatory effect and nutraceutical compounds. 相似文献