An optical scattering method, which measures the size, number, and type of microemboli located in flowing whole blood, is described. A perturbation solution to the one speed radiative transport equation is used to mod...
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An optical scattering method, which measures the size, number, and type of microemboli located in flowing whole blood, is described. A perturbation solution to the one speed radiative transport equation is used to model the scattering geometry. The approximate two-parameter phase function is used to investigate scattering characteristics of microemboli. The nature of microemboli is determined by comparing the scattered intensity ratio in two forward directions, while the size and number are determined by considering intensities scattered perpendicularly to the incident direction. This method has been tested with several sizes of polystyrene spheres, air bubbles, and blood dots. The results showed excellent agreement with calculations.
A thorough understanding of fundamental microwave absorption mechanisms in ionic crystalline solids is important for microwave sintering of ceramics, as well as the design of high speed electronic packaging, advanced ...
A thorough understanding of fundamental microwave absorption mechanisms in ionic crystalline solids is important for microwave sintering of ceramics, as well as the design of high speed electronic packaging, advanced radomes, etc. Of particular importance to these applications are how the density and type of crystalline defects affect the dominant microwave absorption mechanisms. We have designed experiments to measure microwave absorption in NaCl samples with controlled variations in defect conditions(pure, point defects, dislocations and grain boundaries) at different temperatures (20-400 °C) and frequencies (2-20 GHz). Initial results are reported and discussed.
This paper presents a comparison of H/sub /spl infin////spl mu/-synthesis sliding-mode that was done for heading and depth control of the Draper Laboratory/MIT Sea Grant Sea Squirt autonomous underwater vehicle (AUV)....
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This paper presents a comparison of H/sub /spl infin////spl mu/-synthesis sliding-mode that was done for heading and depth control of the Draper Laboratory/MIT Sea Grant Sea Squirt autonomous underwater vehicle (AUV). The approximate decoupling of the AUV heading and depth dynamics allowed us to have decoupled heading and depth designs for both the H/sub /spl infin////spl mu/-synthesis and the sliding-mode methodologies. The H/sub /spl infin////spl mu/-synthesis based controllers and the sliding-mode based controllers were implemented and tested by using a simulation of the AUV full order nonlinear model (including thruster and sensor dynamics). We analyzed the performance of the controllers (for a simultaneous depth and maneuver) over the approximate range of axial velocities commanded by the AUV. The performance of the controllers in the face of additive sensor noise was also analyzed.
A second generation, contrast sensitive silicon retina is reported in this paper. The architecture and organization is inspired by the outer plexiform processing in the vertebrate retina. Current-mode subthreshold MOS...
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A second generation, contrast sensitive silicon retina is reported in this paper. The architecture and organization is inspired by the outer plexiform processing in the vertebrate retina. Current-mode subthreshold MOS design techniques are employed to obtain high performance and energetic efficiency. The system has been fabricated with 230/spl times/210 pixels on a 1/spl times/1 cm die in a 1.2 /spl mu/m n-well double metal, double poly, digital oriented CMOS technology. The chip incorporates 590,000 transistors, 48,000 pixels, operating in subthreshold/transition region with power dissipation of 50 mW when powered from a 5 V power supply. The pixel has a frequency response of 100 kHz.
The authors address the analysis of three dimensional shape and shape change in nonrigid biological objects imaged via a stereo light microscope (SLM). Most existing stereo or motion analysis techniques cannot be appl...
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The authors address the analysis of three dimensional shape and shape change in nonrigid biological objects imaged via a stereo light microscope (SLM). Most existing stereo or motion analysis techniques cannot be applied to microscopic biological images because they usually lack salient features. The authors propose an integrated approach for the reconstruction of 3D structures and motion analysis for scenes where only a few informative features are available. The key components of this framework are: (1) image registration, (2) region-of-interest extraction, and (3) stereo and motion analysis using a cooperative spatial and temporal matching process. The authors describe these three stages of processing and illustrate the efficacy of the proposed approach using real images of a live frog's ventricle. The reconstructed dynamic 3-D structures of the ventricle are demonstrated in the authors' experimental results.< >
The technique of serial optical sectioning by laser scanning confocal microscopy (LSCM), in conjunction with off-line digital image analysis, was used to quantize the morphological changes occurring during angiogenesi...
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The technique of serial optical sectioning by laser scanning confocal microscopy (LSCM), in conjunction with off-line digital image analysis, was used to quantize the morphological changes occurring during angiogenesis and revascularization of pancreatic islets transplanted at the renal subcapsular site in rats. The process consisted of in-vivo imaging of the microvasculature which was optically enhanced by the administration of a fluorescent probe into the circulating blood. Serial two-dimensional (2-D) optical sections were obtained through the vascular bed at varying z-intervals in order to perform a computer reconstruction of the complete three-dimensional (3-D) morphology. Image processing algorithms such as gray level thresholding, median filtering, skeletonization, region labeling and template matching were applied to compute the vessel density, lengths and diameters of the neovasculature, and the tortuosity index.< >
Raman spectroscopy and x-ray diffraction are used to characterize Gallium Nitride (GaN) films grown on (100) Gallium Arsenide (GaAs) substrates. Reflection X-ray diffraction data from (200) planes of GaAs and cubic Ga...
Raman spectroscopy and x-ray diffraction are used to characterize Gallium Nitride (GaN) films grown on (100) Gallium Arsenide (GaAs) substrates. Reflection X-ray diffraction data from (200) planes of GaAs and cubic GaN are presented. The linewidth of the cubic GaN diffraction peak is shown to be a strong function of the growth temperature. Raman spectra are presented for a series of samples grown at different temperatures. Raman scattering is characterized by strong peaks at 560 cm-1 and at 736 cm-1, corresponding to TO and LO phonon modes of cubic GaN, respectively. An additional, unexplained feature at 768 cm-1 is clearly observed in Raman spectra of c-GaN samples grown at lower temperatures. The polarization dependence of the intensity of the GaN LO phonon mode is presented and compared with the GaAs LO phonon mode to establish the relative orientation of the c-GaN epitaxy on GaAs.
The authors characterize electrostatic and other polymer-polymer interactions within an ultracentrifuge cell using a new electrochemical transport model. Applying conservation of mass and momentum of solutes and solve...
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The authors characterize electrostatic and other polymer-polymer interactions within an ultracentrifuge cell using a new electrochemical transport model. Applying conservation of mass and momentum of solutes and solvent, and Maxwell's equations valid in the electroquasistatic limit, together with initial and boundary conditions on solute (and electrolyte) distribution, the authors predict the transient (nonequilibrium) and equilibrium solute (and electrolyte) distributions, net charge density, electric field, and electrostatic potential profiles. This model represents a significant advance ever the Lamm equation (and its extensions) (H. Fujita, 1962), which describe polymer-polymer interactions phenomenologically (using empirical virial coefficients) (L.W. Nichol et al., 1967).< >
We analyze the performance of the real-time system for 3D reconstruction of cardiac structures from successive 2D B-scan ultrasound images acquired using the Tilt Echo technique, developed by Buckey et al. (1987, 1993...
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We analyze the performance of the real-time system for 3D reconstruction of cardiac structures from successive 2D B-scan ultrasound images acquired using the Tilt Echo technique, developed by Buckey et al. (1987, 1993). This system is used to evaluate cardiac performance parameters such as stroke volume and ventricular mass. The design of such a real-time system involves consideration of two features, viz. the accuracy of the 3D reconstructions generated by the system, and the timing behavior of the system. We describe the procedure to test the accuracy of the system and present results to demonstrate the accuracy of reconstruction. We analyze the timing behavior of the system based on simulations using Modechart. We verify that the system design satisfies the real-time constraints.< >
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