Medical equipment can unintentionally allow the flow of power line current through the patient causing complete hemodynamic collapse without fibrillation. This study tests the hypothesis that static wall thickening ac...
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Medical equipment can unintentionally allow the flow of power line current through the patient causing complete hemodynamic collapse without fibrillation. This study tests the hypothesis that static wall thickening accompanies AC induced collapse via an isovolumic state. In 3 dogs, we delivered AC current stimulation ranging from 10-160 Hz and 10-1000 /spl mu/A to the right ventricle. A steerable, quadripolar catheter was placed in the apex of the left ventricle and deflected towards the basal region to measure left ventricular volume. Two dimensional, short-axis ultrasound images of the LV endocardial walls were recorded to measure wall thickness. Our results indicate that wall thickness during collapse is significantly greater than during systole (/spl Delta/ thickness =11.7/spl plusmn/12 mm, p<0.001) and diastole (/spl Delta/ thickness=23.6/spl plusmn/13 mm, p<0.001). In addition, the volume of the left ventricle is significantly smaller during collapse than the average volume during normal sinus rhythm (/spl Delta/ impedance=0.152/spl plusmn/0.006 no units, p<0.001).
A previous study has shown that the cross-sectional area of the left ventricular cavity (LV) increases immediately after defibrillation, suggesting that the defibrillation shock may cause relaxation. Since a single ar...
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A previous study has shown that the cross-sectional area of the left ventricular cavity (LV) increases immediately after defibrillation, suggesting that the defibrillation shock may cause relaxation. Since a single area slice may not reflect the entire myocardium, we wanted to test the relaxation hypothesis by evaluating volume. Ten to twenty defibrillation shocks were delivered in each of six dogs. A catheter was placed in the LV to measure intraventricular volume (IVV). Ultrasound images of the LV were recorded simultaneously with IVV. LV cavity area increased 13% (p<0.001) and IVV increased 4% (p<0.001) post-shock. Our results confirm that the heart is relaxing after defibrillation.
Discrete element method (DEM) was used to study sand-structure interaction. The effect of modeling parameters on formation of shear zones in structure-medium interfaces was also discussed. The results showed that the ...
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Discrete element method (DEM) was used to study sand-structure interaction. The effect of modeling parameters on formation of shear zones in structure-medium interfaces was also discussed. The results showed that the shear zone thickness increases as the surface roughness increases. Also, the shape of the shear zone shows greater curvature and undulations with the increase in degree of structure surface roughness.
An analysis has been performed on major components of a direct energy conversion system DIPEC (Direct Propellant Ionization Energy Conversion) for AIMStar (Antimatter-Initiated Microfusion Starship) propulsion applica...
An analysis has been performed on major components of a direct energy conversion system DIPEC (Direct Propellant Ionization Energy Conversion) for AIMStar (Antimatter-Initiated Microfusion Starship) propulsion applications to deep space. Results for distributed energies, efficiencies, thrust and 1sp are presented.
作者：
R. S. LakesDepartment of Engineering Physics
Engineering Mechanics Program Materials Science Program University of Wisconsin 147 ERB 1500 Engineering Drive Madison Wisconsin 53705
Composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher stiffness and mechanical damping tanδ than that of either constituent and exceeding conventional bounds. The causal mech...
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Composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher stiffness and mechanical damping tanδ than that of either constituent and exceeding conventional bounds. The causal mechanism is a greater deformation in and near the inclusions than the composite as a whole. Though a block of negative stiffness is unstable, negative stiffness inclusions in a composite can be stabilized by the surrounding matrix. Such inclusions may be made from single domains of ferroelastic material below its phase transition temperature or from prebuckled lumped elements.
The influence of compositional strain, transformation strain, and temperature on the competitive growth of three phases in a free standing, thin film is examined. A dynamical system, comprised of coupled Cahn-Hilliard...
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The influence of compositional strain, transformation strain, and temperature on the competitive growth of three phases in a free standing, thin film is examined. A dynamical system, comprised of coupled Cahn-Hilliard and Allen-Cahn equations, is developed and solved numerically using a dual-grid finite difference scheme. Numerical simulation shows that long-range elastic fields alter the kinetics of phase growth from that observed in stress free systems. Phases that are non-equilibrium phases in the absence of stress can stablize in the stressed film. The magnitudes of these effects are presented in a simple case.
The thermoelastic effect was used to produce high frequency, broadband ultrasound in water. A pulsed diode laser, followed by an erbium doped fiber amplifier, was focused onto a light absorbing film deposited on a gla...
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ISBN:
(纸本)0780371771
The thermoelastic effect was used to produce high frequency, broadband ultrasound in water. A pulsed diode laser, followed by an erbium doped fiber amplifier, was focused onto a light absorbing film deposited on a glass substrate. Conversion efficiency was improved by 18 dB using a polydimethylsiloxane (PDMS) film instead of a more commonly used metallic one. Radiation pattern measurements show that considerable energy is radiated at +/-45 degrees for frequencies beyond 75 MHz. These results show that the thermoelastic effect can be used to produce phased arrays for high frequency ultrasound imaging.
Over the past five years, Rose-Hulman has invested over $40M dollars creating an environment to encourage entrepreneurship in its graduates. Components of the educational, organizational, and physical infrastructure a...
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Over the past five years, Rose-Hulman has invested over $40M dollars creating an environment to encourage entrepreneurship in its graduates. Components of the educational, organizational, and physical infrastructure are described. These components include a course in entrepreneurship, internships with entrepreneurial companies, the Technology and Entrepreneurship Development (TED) program, Rose-Hulman Ventures (RHV), and the John T. Myers Center for Technological Research with Industry. Case studies of recent successes are presented.
A previous 2D ultrasound study (R.A. Malkin et al., 2001) suggested that there is relaxation of the myocardium after defibrillation. However, that 2D study could not measure activity occurring within the first 33 ms f...
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A previous 2D ultrasound study (R.A. Malkin et al., 2001) suggested that there is relaxation of the myocardium after defibrillation. However, that 2D study could not measure activity occurring within the first 33 ms following the shock. Thus, the objective of our study is to determine the left ventricular (LV) geometry during this period. Biphasic defibrillation shocks were delivered to seven dogs. 1D short-axis ultrasound images of the LV cavity were acquired, the boundary of the anterior and posterior endocardial walls was extracted and the distance between them computed from 32 ms before to 32 ms after the shock. The normalized mean pre- and post-shock slopes were 0.2 /spl plusmn/ 2.2 and 3.3 /spl plusmn/ 7.9 %/10 ms, respectively. The post-shock LV diameter slope is positive in the first 32 ms following both successful and unsuccessful defibrillation shocks (p<0.05). Therefore, our results confirm that the bulk of the myocardium is relaxing immediately after a defibrillation shock.
We have implemented a synthetic aperture beamformer for real-time 3D imaging using a network of digital signal processors. This system is capable of beamforming 6.6 million points per second. Using simulated acoustica...
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ISBN:
(纸本)0780371771
We have implemented a synthetic aperture beamformer for real-time 3D imaging using a network of digital signal processors. This system is capable of beamforming 6.6 million points per second. Using simulated acoustical inputs, the point response of the beamformer has been evaluated using the actual hardware. The output of the beamformer using pre-calculated inputs is in agreement with simulations. The dynamic range of the system as a function of noise at the inputs has been determined. The experimentally measured root-mean-square noise level of the A/Ds is less than 1 mV, which provides over 65 dB of noise-free dynamic range in the image. Calibrations to remove DC offsets, to correct for gain differences, and to correct for relative delays between channels have been developed. The relative delays can be calibrated to within less than 1/1000/sup th/ of a cycle. A real-time DC correction has been implemented, which corrects for the DC offsets introduced by the truncation error associated with the 16-bit fixed-point summing. The preliminary performance of the beamformer has been characterized using a limited number of narrowband inputs for beamforming. Images made at 650 frames per second using sine wave inputs are in good agreement with simulations.
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