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The spectra of Rayleigh scattering of M?ssbauer radiation (RSMR) and M?ssbauer absorption by globular macromolecules are calculated. The dependence of the spectra parameters on hydration is modeled with the account for thermal low-frequency vibrations of the particles constituting the globule. Deformational motions of the macromolecule fragments leading to deviations from its equilibrium spherical shape are considered introducing collective dynamical variables governed by Langevin equations with random sources of external forces. The macromolecule is modeled by a double-layered sphere: a rigid (elastic) core is surrounded by a porous hydration shell filled with fluid. The dynamical properties of the bound water inside the shell are described by the Debye-Brinkman equations. The degree of hydration is introduced by means of a combination of the mass coefficients of the porous shell with fluid and the mass coefficients in the limiting cases when the flow inside the shell is "frozen" and in the case of free flow. The hydration-dependent Lamb-M?ssbauer factor and the elastic fraction of the RSMR are calculated and compared with experimental data from the literature. 相似文献
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Hilger I Trost R Reichenbach JR Linß W Lisy MR Berndt A Kaiser WA 《Nanotechnology》2007,18(13):135103
The aim of this study was to assess whether Her-2/neu expressing tumour cells can be detected in vitro as well as in animal tumour models with magnetic resonance imaging at 1.5?T. Magnetic nanoparticles (with relaxivities R 1, R 2 of 3.7 ± 0.4?(mM?s)(-1), 277 ± 32?(mM?s)(-1) at 21?°C, respectively) coupled to anti-Her-2/neu antibodies or gamma globulin IgG (high or non-affinity probe, respectively) were used. After incubation of Her-2/neu expressing cells (SKBR3) with high or non-affinity probes (20?min), values of R 1 = 0.34 ± 0.02?(mM?s)(-1) and R 2 = 63.02 ± 30?(mM?s)(-1) were obtained. Electron microscopy and atomic absorption spectrometry examinations verified the presence of relatively high iron levels in cells incubated with the high affinity probe compared to controls. For in vivo MRI, high or non-affinity probes (≈1.7?mg Fe/animal) were injected into the tail vein of mice (n = 16) bearing SKBR3 tumours. A distinct decrease in the normalized MR signal ratio between tumour and reference area (approximately -17 ± 2%) after application of the high affinity probe was observed. In conclusion, in vivo detection of Her-2/neu expressing tumours is feasible in a clinical MR scanner by using immunoconjugated magnetic nanoparticles. 相似文献
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Yobas L. Huff M.A. Lisy F.J. Durand D.M. 《Journal of microelectromechanical systems》2001,10(2):187-196
Recent success of microelectromechanical systems (MEMS) in projection displays have raised similar expectation for an efficient, low power, affordable, full-page and pneumatic tactile display. Such design has not been achieved by the conventional technology but could bring significant improvement to current refreshable Braille displays. This paper demonstrates a novel bulk-micromachined electrostatic microvalve suitable for a pneumatic tactile display. The microvalve, a silicon perforated diaphragm juxtaposed to a silicon inlet orifice, requires relatively low closing voltage against a large supply differential pressure and flow rate, i.e., 72.9 V-rms for 19.3 kPa and 85 mi/min. Such an attractive characteristic is due to its unique curved-compliant structure that has, unlike other electrostatic microvalves, no tolerance for any initial air gap between its electrodes. As a design tool, a mechanical model of the microvalve is introduced based on the lubrication theory and large plate deflection theory. The model is established on a steady-state coupled field problem of fluid-solid mechanics. Reynolds and von-Karman equations were simultaneously solved for the microvalve geometry by finite difference approximation and double Fourier series expansion. The results of the model and experiments are compared and found to be in good agreement with a relative error less than 10% 相似文献
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Yobas L. Durand D.M. Skebe G.G. Lisy F.J. Huff M.A. 《Journal of microelectromechanical systems》2003,12(3):252-263
We introduce a novel integrable and electrostatic microvalve for the purpose of enabling a pneumatic refreshable Braille display system (RBDS). Physical design parameters of the microvalve such as orifice size, beam length, number of beams and beam profile are experimentally explored and found promising for use with the RBDS. Particularly, one design with an orifice of 70 /spl mu/m/spl times/70 /spl mu/m, beam length of 665 /spl mu/m, and beam count of 20 is electrostatically closed against a differential pressure of 82.7 kPa with an applied voltage of 68 V-rms. Also introduced is a steady-state mechanical model of the microvalve established on a coupled solution of fluid and solid domains. The model and experimental test results have been used to calculate the unknown discharge coefficient, elastic deflection, and entrance pressure. The model reveals that some of the designs have remarkably low discharge coefficient and entrance pressure, implying that pressure loss occurs mostly through and around the inlet port even at fairly large supply pressures. Experimental observations concerning the practical use of the microvalve are discussed. 相似文献
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