Context-Based Path Prediction for Targets with Switching Dynamics

International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem...     

Exact radon rebinning algorithm for the long object problem in helical cone-beam CT

This paper addresses the long object problem in helical cone-beam computed tomography. We present the PHI-method, a new algorithm for the exact reconstruction of a region-of-interest (ROI) of a long object from axially truncated data extending only slightly beyond the ROI. The PHI-method is an extension of the Radon-method, published by Kudo, Noo, and Defrise in issue 43 of journal Physics in Medicine and Biology. The key novelty of the PHI-method is the introduction of a virtual object fpsi(x) for each value of the azimuthal angle psi in the image space, with each virtual object having the property of being equal to the true object f(x) in some ROI omegam. We show that, for each psi, one can calculate exact Radon data corresponding to the two-dimensional (2-D) parallel-beam projection of fpsi(x) onto the meridian plane of angle psi. Given an angular range of length pi of such parallel-beam projections, the ROI omegam can be exactly reconstructed because f(x) is identical to fpsi(x) in Omegam. Simulation results are given for both the Radon-method and the PHI-method indicating that 1) for the case of short objects, the Radon- and PHI-methods produce comparable image quality, 2) for the case of long objects, the PHI-method delivers the same image quality as in the short object case, while the Radon-method fails, and 3) the image quality produced by the PHI-method is similar for a large range of pitch values.     

Determination of the spatial variation of the carrier lifetime in aproton-irradiated Si n+-n-p+ diode byoptical-beam-induced current measurements

It is shown that the local carrier diffusion length can be obtained from optical-beam-induced current (OBIC) measurements on a diode structure with the p-n junction perpendicular to the surface by evaluating the local slope of the OBIC signal, when the light penetration depth is sufficient and when the sample can be considered semi-infinite. The method is applied to several n⁺-n-p⁺ diodes which were proton-irradiated at various proton fluxes. The measured lifetime profiles after proton irradiation are found to agree very well with defect profiles     

Sensations and brain processes

A hypothesis on the physiological conditions of consciousness is presented. It is assumed that the occurrence of states of consciousness causally depends on the formation of complex representational structures. Cortical neural networks that exhibit a high representational activity develop higher-order, self-referential representations as a result of self-organizing processes. The occurrence of such states is identical with the appearance of states of consciousness. The underlying physiological processes can be identified. It is assumed that neural assemblies instantiate mental representations; hence consciousness depends on the rate at which large active assemblies are generated. The formation of assemblies involves the activation of the N-methyl-D-aspartate receptor channel complex which controls different forms of synaptic plasticity including rapid changes of the connection strengths. The various causes of unconsciousness (e.g., anaesthetics or brain stem lesions) have a common denominator: they directly or indirectly inhibit the formation of assemblies.     

Thermophysical Properties of a Refrigerant Mixture of R365mfc (1,1,1,3,3-Pentafluorobutane) and Galden<Superscript>®</Superscript> HT 55 (Perfluoropolyether)

This work presents a comprehensive experimental study of various thermophysical properties of an azeotropic refrigerant mixture of 65 mass% R365mfc (1,1,1,3,3-pentafluorobutane) and 35 mass% Galden^? HT 55 (perfluoropolyether). Light scattering from bulk fluids has been applied for measuring both the thermal diffusivity and the speed of sound in the liquid and vapor phases under saturation conditions, between 293 K and the liquid–vapor critical point at 450.7 K. Furthermore, the speed of sound has been measured for the superheated-vapor phase along nine isotherms, between 393 and 523 K and up to a maximum pressure of about 2.5 MPa. For temperatures between 253 and 413 K, light scattering by surface waves on a horizontal liquid–vapor interface has been used for simultaneous determination of the surface tension and kinematic viscosity of the liquid phase. With light scattering techniques, uncertainties of less than ±2.0%, ±0.5%, ±1.5%, and ±1.5% have been achieved for the thermal diffusivity, sound speed, kinematic viscosity, and surface tension, respectively. In addition to vapor-pressure measurements between 304 and 448 K, the density was measured between 273 and 443 K using a vibrating-tube method. Here, measurements have been performed in the compressed- and saturated-liquid phases with uncertainties of ±0.3% and ±0.1%, respectively, as well as for the superheated vapor up to a maximum pressure of about 3 MPa with an uncertainty between ±0.3% and ±3%. Critical-point parameters were derived by combining the data obtained by different techniques.     

Spiral interpolation algorithms for multislice spiral CT--part II: measurement and evaluation of slice sensitivity profiles and noise at a clinical multislice system

The recently introduced multislice data acquisition for computed tomography (CT) is based on multirow detector design, increased rotation speed, and advanced z-interpolation and z-filtering algorithms. We evaluated slice sensitivity profiles (SSPs) and noise of a clinical multislice spiral CT (MSCT) scanner with M = 4 simultaneously acquired slices and adaptive axial interpolator (AAI) reconstruction software. SSPs were measured with a small gold disk of 50 microm thickness and 2-mm diameter located at the center of rotation (COR) and 100 mm off center. The standard deviation of CT values within a 20-cm water phantom was used as a measure of image noise. With a detector slice collimation of S = 1.0 mm, we varied spiral pitch p from 0.25 to 2.0 in steps of 0.025. Nominal reconstructed slice thicknesses were 1.25, 1.5, and 2.0 mm. For all possible pitch values, we found the full-width at half maximum (FWHM) of the respective sensitivity profile at the COR equivalent to the selected nominal slice thickness. The profiles at 100 mm off center are broadened less than 7 % on the average compared with the FWHM at the COR. In addition, variation of the full-width at tenth maximum (FWTM) at the COR was below 10% for p < or = 1.75. Within this range, image noise varied less than 10% with respect to the mean noise level. The slight increase in measured slice-width above p = 1.75 for nominal slice-widths of 1.25 and 1.50 mm is accompanied by a decrease of noise according to the inverse square root relationship. The MSCT system that we scrutinized provides reconstructed slice-widths and image noise, which can be regarded as constant within a wide range of table speeds. With respect to this, MSCT is superior to single-slice spiral CT. These facts can be made use of when defining and optimizing clinical protocols: the spiral pitch can be selected almost freely, and scan protocols can follow the diagnostic requirements without technical restrictions. In summary, MSCT offers constant image quality while scan times are reduced drastically. Volume scans with three-dimensional (3-D) isotropic resolution are routinely feasible for complete anatomical regions.     

Accuracy of visually and memory-guided antisaccades in man

Primary saccades to remembered targets are generally not precise, but rather undershoot target position. The major source of this saccadic undershoot may be (a) a memory-related process or (b) a poor spatial resolution in those processes which transfer the retinotopic target information into an intermediate memory-linked representation of space. The aim of this study was to investigate whether distortions of eye positions in the antisaccade task, which are characterized by inherent co-ordinate transformation processes, may completely account for the spatial inaccuracies of memory-guided antisaccades. The results show that the spatial inaccuracy of primary and secondary eye movements in the visually guided antisaccade task was comparable to that in the memory-guided antisaccade task. In both conditions, the direction error component was less dysmetric than the amplitude error component. Secondary eye movements were significantly corrective. This increase of eye position accuracy was achieved by reducing the amplitude error only. It is concluded from this study that at least some of the distortion of memory-guided saccades is due to inaccuracies in the sensorimotor co-ordinate transformations.     

Regional distribution of vascular resistance in two models of experimental renovascular hypertension

The data from 88 patients (pts) with aortic stenosis (AS) were reviewed to determine relationships between angina pectoris (AP) and coronary artery disease (CAD). Results of surgery performed in 81 of these pts was analyzed. All pts had coronary arteriograms, and lesions greater than or equal to 50% were considered significant. Fifty-nine pts had an aortic valve gradient measured at catheterization greater than or equal to 40 mmHg, and in 29 pts, AS was confirmed at operation. Sixty-eight pts (77%) experienced AP, and 32 had coexisting CAD (47%); 9 of 20 pts without AP had CAD (45%). There were no significant differences in the incidence of AP in pts divided into subgroups by the aortic valve gradient (40-50, 51-100, 101-200 mmHg) or age (40-59, 60-81 years). Also, no significant differences were found in the incidence or extent of CAD between the two age groups; the extent of CAD was similar regardless of the presence or absence of AP. In pts with AP (1) CAD was more likely in pts greater than or equal to 60 years of age; (2) CAD was less likely when the aortic valve gradient was greater than 100 mmHg, suggesting that AP in these pts was due to hemodynamically severe AS. All pts with 3-vessel CAD experienced AP, and the aortic valve gradient was less in these pts than in those with no CAD or less extensive CAD. In 19 pts with combined AS and CAD who had both the aortic valve replaced and a revascularization operation only 1 of pts died in the hospital, while 3 of 19 pts with combined AS and CAD who had aortic valve replacement alone died. In this study a significant number of pts with AS experienced AP, and the presence or absence of AP did not predict coexisting CAD. Coronary arteriography is recommended in the evaluation of pts greater than or equal to 40 years of age with AS. The operative mortality appears to be decreased in pts with AS and CAD who have combined surgery.     

Photoinduced surface crosslinking of superabsorbent polymer particles

Superabsorbent polymer particles, consisting of partly neutralized, slightly crosslinked poly(acrylic acid), have been surface‐crosslinked photochemically. Surface crosslinking is required for many applications of superabsorbent polymers, such as disposable diapers, to control the flow and absorption of liquids in the gel bed. Photoinduced surface crosslinking has been achieved under UV irradiation (200–300 nm) with (NH₄)₂S₂O₈ as a photoactivated crosslinking agent. In comparison with the currently used thermal ester bridging method for surface crosslinking, the new photochemical method generates superabsorbent particles with superior properties, such as an improved flow of liquid through the gel bed, which utilizes the entire gel bed. These improved properties have been shown by water absorption capacity studies, fluid flow dynamics, environmental scanning electron microscopy, and low‐energy ion‐scattering studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009