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91.
Statistical energy analysis (SEA) is commonly used in industry to predict high-frequency vibrational response of structures. Since only local modes are used in SEA, only high-frequency responses can be predicted. This study extends SEA to the middle-frequency region by additionally using global modes. Methods using impedance matrices that can be found by NASTRAN are developed. Then the results are post processed to determine coupling loss factors. 相似文献
92.
Prion proteins that have transformed from their normal cellular counterparts (PrPc) into infectious form (PrPres) are responsible for causing progressive neurodegenerative diseases in numerous species, such as bovine spongiform encephalopathy (BSE) in cattle (also known as mad cow disease), scrapie in sheep, and Creutzfeldt-Jakob disease (CJD) in humans. Due to a possible link between BSE and CJD it is highly desirable to develop non-invasive and ante mortem tests for the detection of prion proteins in bovine samples. Such ante mortem tests of all cows prior to slaughter will help to prevent the introduction of PrPres into the human food supply. Furthermore, detection of PrPres in donated blood will also help to prevent the transmission of CJD among humans through blood transfusion. In this study, we have continued development of a micromechanical resonator array that is capable of detecting PrPc in bovine blood serum. The sensitivity of the resonators for the detection of PrPc is further enhanced by the use of secondary mass labels. A pair of antibodies is used in a sandwich immunoassay format to immobilize PrPc on the surface of resonators and attach nanoparticles as secondary mass labels to PrPc. Secondary mass labeling is optimized in terms of incubation time to maximize the frequency shifts that correspond to the presence of PrPc on the surface of resonators. Our results show that a minimum of 200 pg mL−1 of PrPc in blood serum can be detected using micromechanical resonator arrays. 相似文献
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Barton RJ Smith KB Vincent HT 《The Journal of the Acoustical Society of America》2011,129(5):2772-2784
The properties of the scattered acoustic vector fields generated by simple spheres illuminated by monotonic continuous wave (CW) plane waves are investigated. Analytical solutions are derived from general acoustic pressure scattering models and analyzed for wave numbers in the resonance region. Of particular interest is the understanding of the characteristics of the scattered acoustic vector field in the near-to-far-field transition region. The separable active and reactive components of the acoustic intensity are used to investigate the structural features of the scattered field components. Numerical results are presented for the near and transition regions for a rigid sphere. A method of mapping nulls in the scattered intensity field components is described. The analysis is then extended to include a simple fluid-filled boundary and finally the evacuated thin-walled shell. Near field acoustic intensity field structures are compared against mechanical material properties of vacuous shells. The ability to extract scattered field features is illustrated with measurements obtained from a recent in-air experiment using an anechoic chamber and acoustic vector sensor probes to measure the scattered acoustic vector field from rigid spheres. 相似文献
98.
Harald Grosse Fedele Lizzi Harold Steinacker 《General Relativity and Gravitation》2011,43(9):2531-2539
We argue that some features of the standard model, in particular the fermion assignment and symmetry breaking, can be obtained in matrix model which describes noncommutative gauge theory as well as gravity in an emergent way. The mechanism is based on the presence of some extra (matrix) dimensions. These extra dimensions are different from the usual ones which give to a noncommutative geometry of the Grönewold-Moyal type, and are reminiscent of the Connes-Lott model, although the action is very different. 相似文献
99.
We provide a model for the remarkable stability of surface nanobubbles to bulk dissolution. The key to the solution is that the gas in a nanobubble is of Knudsen type. This leads to the generation of a bulk liquid flow which effectively forces the diffusive gas to remain local. Our model predicts the presence of a vertical water jet immediately above a nanobubble, with an estimated speed of ~3.3 m/s, in good agreement with our experimental atomic force microscopy measurement of ~2.7 m/s. In addition, our model also predicts an upper bound for the size of nanobubbles, which is consistent with the available experimental data. 相似文献
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