Calcium-dependent calmodulin binding to cholinergic synaptic vesicles.

Calmodulin is a major nerve terminal protein and a potential mediator of calcium-dependent nerve terminal functions. Calcium-dependent calmodulin binding has been reported in secretory membrane preparations including chromaffin granules and crude rat brain vesicles. Here we demonstrate a calcium-dependent calmodulin-binding site on cholinergic synaptic vesicles from electric organ. It is saturable with high affinity (KD = 10 nM; Bmax = 80 pmol/mg). The binding is inhibited by trifluoperazine (I50 = 8 microM) and is at least 1000-fold specific for calmodulin over troponin C. Association and dissociation rates (k = 3.1 X 10(6) M-1S-1; k-1 = 1.3 X 10(-2) S-1) are consistent with the dissociation constant measured at equilibrium. Intact synaptic vesicles bind to calmodulin immobilized on polyacrylamide matrix, suggesting that the binding site is cytoplasmically oriented in the vesicle population. Intact synaptic vesicles bind calmodulin up to 80-fold more effectively than do side fractions from the vesicle purification. The quantitative difference is largely due to latency of binding sites since it disappears when the binding is assayed in detergent. Binding of calmodulin to proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows that a subset of nerve terminal and electric organ calmodulin-binding proteins are found in synaptic vesicles.

Matched filters for bin picking.

Currently, a major difficulty for the widespread use of robots in assembly and material handling comes from the necessity of feeding accurately positioned workpieces to robots. ``Bin picking'' techniques help reduce this constraint. This paper presents the application of matched filters for enabling robots with vision to acquire workpieces randomly stored in bins. This approach complements heuristic methods already reported. The concept of matched filter is an old one. Here, however, it is redefined to take into account robot end-effector features, in terms of geometry and mechanics. In particular, the proposed filters match local workpiece structures where the robot end-effector is likely to grasp successfully and hold workpieces. The local nature of the holdsites is very important as computation costs are shown to vary with the fifth power of structure size. In addition, the proposed filters tend to have a narrow angular bandwidth. An example, which features a parallel-jaw hand is developed in detail, using both statistical and Fourier models. Both approaches concur in requiring a very small number of filters (typically four), even if a good orientation accuracy is expected (two degrees). Success rates of about 90 percent in three or fewer attempts have been experimentally obtained on a system which includes a small minicomputer, a 128 × 128 pixel solidstate camera, a prototype Cartesian robot, and a ``universal'' parallel-jaw hand.

Error analysis of surface normals determined by radiometry.

Surface normals can be computed from three images of a workpiece taken under three distinct lighting conditions without requiring surface continuity. Radiometric methods are susceptible to systematic errors such as: errors in the measurement of light source orientations; mismatched light source irradiance; detector nonlinearity; the presence of specular reflection or shadows; the spatial and spectral distribution of incident light; surface size, material, and microstructure; and the length and properties of the light source to target path. Typically, a 1° error in surface orientation of a Lambertian workpiece is caused by a 1 percent change in image intensity due to variations in incident light intensity or a 1° change in orientation of a collimated light source. Tests on a white nylon sphere indicate that by using modest error prevention and calibration schemes, surface angles off the camera axis can be computed within 5°, except at edge pixels. Equations for the sensitivity of surface normals to major error sources have been derived. Results of surface normal estimation and edge extraction experiments on various non-Lambertian and textured workpieces are also presented.