-Surface waves with a frequency of 0.5-2.5 Hz were generated on a homogeneously fluidized bed. The propagation velocity and rate of attenuation of the induced pressure fluctuations were measured using signal averaging techniques. The measured wave velocity and attenuation rate correlated well with predictions based on a theory which considers the bed as an incompressible liquid with low viscosi...

Planar g-scintigraphy is often used to quantify pulmonary deposition patterns from aerosol inhalers. The results are quite different from those obtained using 3-dimensional PET and SPECT. The purpose of this study was to characterize the effects of scatter and tissue attenuation on the distribution of radiolabeled aerosol as measured by planar scintigraphy using Monte Carlo simulations. This st...

BACKGROUND Most large cohort studies have used a food frequency questionnaire (FFQ) for assessing dietary intake. Several biomarker studies, however, have cast doubt on whether the FFQ has sufficient precision to allow detection of moderate but important diet-disease associations. We use data from the Observing Protein and Energy Nutrition (OPEN) study to compare the performance of a FFQ with t...

Background: In this study, a method for linear attenuation coefficient calculation was introduced.Methods: Linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. The calculation was done for Cerrobend as a common radiotherapy modifier and Mercury.Results: The values...

Background: Photon attenuation as an inevitable physical phenomenon influences on the diagnostic information of SPECT images and results to errors in accuracy of quantitative measurements. This can be corrected via different physical or mathematical approaches. As the correction equation in mathematical approaches is nonlinear, in this study a new method of linearization called ‘Piece ...

amplitudes of seismic waves decrease with distance according to anelastic properties of the earth and geometrical spreading. the attenuation of ground-motion amplitudes in the frequency domain is an important problem in engineering seismology. it is of particular practical interest in the regions such as zagros (iran). the zagros fold- thrust belt, as a part of alpine- himalayan orogenic belt i...

UNLABELLED Planar gamma-scintigraphy is often used to quantify pulmonary deposition patterns from aerosol inhalers. The results are quite different from those obtained using 3-dimensional PET and SPECT. The purpose of this study was to characterize the effects of scatter and tissue attenuation on the distribution of radiolabeled aerosol as measured by planar scintigraphy using Monte Carlo simul...

We used a CT program "density mask" outlining areas with attenuation values less than -910 HU, to indicate areas of emphysema on a chest CT and to provide an overall percentage of lung involvement by emphysema. The "density mask" quantitation of emphysema was previously shown to correlate well with the pathologic assessment of emphysema in patients undergoing lung resection. We compared the CT ...

This paper is concerned with the use of leaky Lamb waves for the nondestructive evaluation (NDE) of damage in anisotropic materials such as fiber-reinforced composites. Two fundamental acoustic properties of the material, namely, the wave speed and attenuation have been measured. Stiffness is deduced from the wave speed. The damage mode selected for this study is matrix cracking. As expected, t...

Forty lumberjacks who had used a chain saw for 0-20 years and who had no general disease affecting the bones were studied by measuring the thenar muscle blood flow of both hands by the 133-Xe local clearance method. Bone mineral in the left forearm in the region of cancellous and cortical bone was assessed by the 241-Am gamma ray attenuation method. Virbration was found to decrease the blood fl...