Nanoscale optical imaging of chromosomes with apertureless microscopy.

Near-field optical structure of the centromere region of undyed polytene chromosomes has been observed using an apertureless near-field optical microscope that detects the intensity of light scattered from an atomic force microscope tip under laser illumination. The centromere is of primary importance to the functioning of the chromosome in the cell during cell division. It is also particularly interesting for structural/optical studies since its DNA repeat sequences are highly conserved among organisms and it is possible that they play a part in the centromere self assembly (Clark and Wall 1996).

Observation of nanometer-scale optical property discrimination by use of a near-field scanning apertureless microscope.

We examine fundamental issues related to discriminating structural and optical features in near-field scanning apertureless microscopy. We report a series of controlled experiments with nanosphere-sized standard spheres in which we observed significant differences in resolution and structure between an atomic-force microscope image and a simultaneously acquired near-field optical (NFO) image. Further, in experiments that employed a mix of dyed and undyed nanospheres we found that we can observe differences in the same NFO image for adjacent nanospheres. Therefore we conclude that near-field scanning apertureless microscopy not only meets the criteria for a NFO image but also is capable of measuring optical properties below the diffraction limit. The two-point resolution was at least 200 nm when we were detecting optical phase and 50 nm when we were detecting optical intensity. The edge response was typically 15 nm, and the minimum observable features were of the order of 3 nm.

A feedforward artificial neural network based on quantum effect vector-matrix multipliers.

The vector-matrix multiplier is the engine of many artificial neural network implementations because it can simulate the way in which neurons collect weighted input signals from a dendritic arbor. A new technology for building analog weighting elements that is theoretically capable of densities and speeds far beyond anything that conventional VLSI in silicon could ever offer is presented. To illustrate the feasibility of such a technology, a small three-layer feedforward prototype network with five binary neurons and six tri-state synapses was built and used to perform all of the fundamental logic functions: XOR, AND, OR, and NOT.