Optoelectronic architecture for associative memory applicable to 2-D pattern comparison

A simple optoelectronic architecture is defined with capabilities of matching a test image (1-D or 2-D) with stored images. It is shown that if a test image and a complementary stored image together with complementary test image and stored image are compared optically, the emerging light intensity is minimum for the best match (i.e., shortest Hemming distance). This allows the suggested architecture to do efficient parallel comparison and to point out the best matched test image. If the image is presented in a two color scheme (say red-blue) and the memory images are stored in the complimentary color scheme transparency (i.e., blue-red), then a white light source allows comparison and detection of best matched image without the need for a separate set of complimentary images. A time-varying light intensity (or a time-varying thresholding voltage) source and an integrating-threshold device which switches its state when light input falls below a threshold value are two ingredients, which are used to select the best match in parallel. Grey level detection can also be implemented by the scheme. The architecture is also ideally suited to finding the closeness of match of two images.

Limitations of the lipid state hypothesis for atherosclerosis are revealed by X-ray diffraction measurements

The lipid state hypothesis proposes that liquid crystalline states of cholesteryl esters play a role in the development and persistence of the fatty streak lesions characteristic of atherosclerosis. We have tested several corollaries suggested by this hypothesis and find that the ensemble of droplets in atherosclerotic tissue are predominantly in the isotropic (fluid) state at 37.0 degrees C. Furthermore, the liquid-crystalline state transition behavior of these droplets is not influenced significantly by the distribution of component cholesteryl ester species. There are no significant correlations between the transition behavior of the droplets and the age, sex, or race of the subjects from which tissue samples were taken. These results show that the lipid state hypothesis is weak, and that the origin and persistence of fatty streak lesions in humans is probably dominated by other factors.

Quantum confined Stark effect of excitonic transitions in GaAs/AIGaAs MQW structures for implementation of neural networks: basic device requirements

We examine theoretically and experimentally the properties of two electrooptic devices based on quantum confined Stark effect of excitonic transitions. These two devices are shown to be critical in implementation of the Hopfield model as well as other neural type networks for associative memories. P-i(multiquantum wells)-n structures using GaAs/AlGaAs provide a controller-modulator device which has integrating-thresholding properties required of neurons. The p-i-n structures also provide programmable modulators which can serve as a synaptic mask. Using Monte Carlo techniques we examine an all-optical architecture to implement the Hopfield network. No external feedback-thresholding circuitry is required in this implementation due to special design of the controller-modulator device. Speed and stability issues of this architecture are also addressed. The computer simulation results provide valuable insight into how the controllermodulator device should be improved for better network implementation.

Interventional radiologic procedures in the management of the renal transplant patient

Interventional radiologic procedures have become an important adjunct to the management of the renal transplant patient. Numerous problems can be dealt with, and in our experience these have included the diagnosis and treatment of ureteric obstruction, dilatation of renal artery stenoses, drainage of abscesses, hematomas and lymphoceles, management of complications of pancreatitis and treatment of bleeding due to fistulas and pseudoaneurysms.

Production of xanthomegnin and viomellein by species of Aspergillus correlated with mycotoxicosis produced in mice

By using thin-layer chromatography and infrared spectroscopy, xanthomegnin and viomellein have been isolated and identified from species of the Aspergillus ochraceus group. A correlation was established between the occurrence of these fungal quinones in the fungal cultural products and the ability of these products to induce mycotoxicosis in mice. In addition, a method was employed to estimate the amount of xanthomegnin and viomellein produced by the fungi.

The effects of hydroquinone, hematin and heme-containing proteins on prostaglandin biosynthesis by methylcholanthrene-transformed mouse BALB/3T3 fibroblasts

Cultured methylcholanthrene-transformed 3T3 mouse fibroblasts secrete large amounts of prostaglandin into the medium. Prostaglandin biosynthesis by these cells can be stimulated by arachidonic acid and, to a much lesser extent, by glutathione and porphyrin. In the presence of hydroquinone, prostaglandin production is increased; the most striking increases are seen at concentrations that are lethal. Porphyrins, when added to cells in the presence of lethal levels of hydroquinone, inhibit stimulation of prostaglandin E2 synthesis but stimulate the production of prostaglandin F2alpha.

Electron spin resonance spin-label studies of intercalation of ethidium bromide and aromatic amine carcinogens in DNA

A spin-labeled technique has been developed for the study of carcinogen-DNA intercalation mechanisms utilizing a modified ethidium bromide as a model ligand and specifically synthesized spin labels of carcinogenic aromatic amines such as 2-aminofluorene, 2-aminoanthracene, and 6-aminochrysene. The technique takes advantage of the characteristic electron spin resonance anisotropy of the corresponding spin labels complexed with DNA. Analysis of the orientation-dependent information thus obtained has clearly shown that the lignad moieties in all 4 respective complexes are accommodated in adjacent base-pair layers of the DNA with the nitroxide reporter oriented in 1 preferential direction. The geometry of the nitroxide rings with respect to their respective constraining ligands in a particular complex appeared to be largely dependent upon the size of the ligand moiety and the position of the reporter attachment on the ligand molecule. A coplanar configuration is most favored for the spin labels in which the ligand moiety per se is a 3-fused ring with the nitroxide substituted at a position on or close to the longitudinal end of the ligand molecule. Temperature studies in which the heat-induced release of the bound label is monitored by electron spin resonance gives an accurate measure of the complex dissociation characteristics that appear to parallel the helical coil cooperative melting transition monitored by absorbance measurements. The extent of dissociation of the bound spin labels parallels almost exactly the melting, i.e., unzipping of the DNA double helix, suggesting that the spin labels are immobilized by intercalation at the site on the DNA directly involved in the maintenance of the double helical structure. Analysis of the electron spin resonance spectra of the complexes in terms of the extent of immobilization indicates that, for aromatic amine spin labels, two different binding species exist, one strongly immobilized presumably at a guanine-cytosine base-pair region and the other partially immobilized in a region other than guanine-cytosine base pair. Competitive binding of the labels with respect to their parent ligand and binding isotherm results show that nitroxide substitution does not affect the type of binding but does affect the extent of binding, i.e.. binding constant with the labeled compound having a lower affinity.