Annihilation reactions in two-dimensional percolation clusters: Effects of short-range interactions

Duplex scanning is becoming increasingly important in the diagnosis and follow-up of arterial lesions, though most surgeons and radiologists currently still prefer diagnostic angiography prior to percutaneous transluminal angioplasty (PTA). We performed PTA based on Duplex scanning alone in 31 selected patients during the last 6 months of 1991. Seventeen patients were treated for lower extremity ischemia and 14 for (a)-symptomatic stenosis in a peripheral bypass. Results of Duplex scanning were compared to the finding of PTA to assess the value of Duplex scanning done prior to PTA. Duplex scanning showed 51 lesions eligible for PTA, in 48 of 51 lesions (94%) the location as found with Duplex scanning was in agreement with the findings of the angiogram during PTA. Of a total of 31 patients scheduled for PTA, Duplex scanning predicted the indication for PTA adequately in 26 patients (84%). No complications were seen. Duplex scanning proved to be a valuable tool in the detection of lesions suitable for PTA. Furthermore, puncture site and route can be determined by means of Duplex scanning.     

Nonlinear preprocessing in short-range motion

The phenomenon of non-Fourier motion (visually perceived motion that cannot be explained simply on the basis of the autocorrelation structure of the visual stimulus) is well recognized, and is generally considered to be due to nonlinear preprocessing of the visual stimulus prior to a stage of standard motion analysis. We devised a sequence of novel visual stimuli in which the availability of a motion stimulus depends on the nature of the nonlinear preprocessing: an nth order stimulus Pn will generate a perception of motion if it is preprocessed by a nonlinearity of polynomial order n or greater, but not if preprocessed by a nonlinearity of polynomial order less than n. We found that unambiguous motion direction was perceived for P2, P3, and P4, but not for higher-order stimuli, and we measured the contrast thresholds for direction discrimination with superimposed noise. We found that an asymmetric compressive nonlinearity can, in a unified fashion, account for these results, while a purely quadratic nonlinearity or a rectification of the form T(p) = magnitude of p cannot. We compared velocity discrimination judgements for second-order non-Fourier stimuli (P2) with standard drifting gratings. Although velocity comparisons were veridical, uncertainties were greater for the non-Fourier stimuli. This could be reproduced by substituting a Fourier grating with superimposed noise for the non-Fourier grating. These findings are consistent with a single pathway which processes both Fourier and non-Fourier short-range motion, and are discussed in the context of other investigations which have been interpreted as demonstrating separate pathways.     

Thermal chemistry and short-range order in Co-Sb melts

The enthalpies of mixing for the liquid Co-Sb alloys are measured by isoperibolic calorimetry at 1600 K over the whole concentration range relative to liquid Sb and undercooled liquid Co. The minimal integral enthalpy of mixing is −6.3 ± 0.6 kJ/ mole at x_Co = 0.50. Activity of components, Gibbs energy, and the entropy of mixing are calculated using a short-range ordering model considering CoSb associates formed in molten Co-Sb alloys. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 96–101, 2007.