Recognition of shiny dielectric objects by analysing the polarization of reflected light

The degree of polarization of light reflected from a transparent or translucent object depends only upon the angle of incidence, refractive index and absorption coefficient of the material. It is therefore possible to determine the orientation of the surface normal from the direction of the plane of polarization. The feasibility of this is demonstrated both theoretically and practically by calculating and measuring the reflectance map of a sphere when viewed through a plane polarizing filter. Ambiguities in the mapping from radiance to orientation are removed by orienting the filter at three angles. The orientation of our objects is determined to within an uncertainty of less than seven degrees.     

Atrioventricular conduction during long-term follow-up of patients with sick sinus syndrome

BACKGROUND: It has been claimed that patients with sick sinus syndrome have an increased risk of developing AV block, but this has never been assessed prospectively. The aim of the present study was to evaluate in a prospective trial AV conduction during the long-term follow-up of patients with sick sinus syndrome. METHODS: Two hundred twenty-five consecutive patients with sick sinus syndrome and intact AV conduction were randomized to undergo single-chamber atrial pacing (110 patients) or single-chamber ventricular pacing (115 patients). Follow-up after 3 months and then yearly included measurement of the PQ interval and, in patients with atrial pacemakers, determination of the atrial stimulus-Q intervals at pacing rates of 100 and 120 bpm. The occurrence of AV block in the atrial group was recorded. During follow-up (mean, 5.5+/-2.4 years), there was no change in PQ interval in either group and no change in atrial stimulus-Q intervals or Wenckebach block point in the atrial group. Four of 110 patients in the atrial group developed grade 2 to 3 AV block that required upgrading of the pacemaker (0.6% per year). Two of these 4 patients had right bundle-branch block at pacemaker implantation. CONCLUSIONS: AV conduction, estimated as PQ interval and atrial stimulus-Q interval at atrial pacing rates of 100 and 120 bpm and the Wenckebach block point, remains stable during long-term follow-up. Thus, treatment with single-chamber atrial pacing is safe and can be recommended to patients with sick sinus syndrome without bundle-branch block.