The shallow-cavity crossed-slot antenna is a UHF radiator designed primarily for use on a high-speed aircraft operating as the airborne terminal in a satellite-to-air communications link. The requirements, design analysis and performance characteristics are described. The antenna's shallow profile makes it attractive either as a "paste-on" or flush-mounted type radiator. Near-hemispherical radiation coverage is provided.
Embryonic porcine brain tissue from the lateral ganglionic eminence was transplanted into the adult rat hippocampus to determine whether fetal striatal cells could survive, differentiate, and integrate in a heterotopic site. The hippocampus, a common site of epileptic seizure activity, was chosen to determine if fetal striatal cells could supply inhibitory GABAergic neurons that may serve to block seizures. Cells were either implanted with a single deposit using a standard metal cannula or by five smaller disseminated deposits with a glass micropipette. At 20-24 weeks, animals immunosuppressed with cyclosporin showed long-term survival of porcine cells in the adult hippocampus. Analysis by immunohistochemistry and in situ hybridization showed that the grafts contained glial and neuronal cell types, including GABAergic neurons within graft core and networks of porcine neuronal fibers extending from the graft into the host parenchyma. In addition, a marker of porcine presynaptic terminals, synaptobrevin, was abundant within the grafts and was found associated with hippocampal structures and cell layers suggesting functional integration of grafted cells within the host. The survival of xenografts in the hippocampus and potential integration of inhibitory components provides evidence that these grafts may serve as an internal negative feedback mechanism to quench epileptiform activity.
The 440-Mcps conical-scan tracker at the Millstone Hill radar site has been converted to an L-band 12-horn monopulse tracker utilizing a Cassegrain optics reflector system. The amplitude sensing monopulse feed illuminates a 10-foot subreflector and thence an 84-foot-diameter paraboloid with linear or either sense of circular polarization. This system conversion increased the capabilities of the radar complex in that higher antenna gain and increased tracking sensitivity are obtained. The merits of the 12-horn system have been proven with actual results substantiating the theoretical predictions. This report discusses the design considerations and final performance characteristics of the overall antenna system and its individual components.
The shallow-cavity crossed-slot antenna is a UHF radiator designed primarily for use on a high-speed aircraft operating as the airborne terminal in a satellite-to-air communications link. The requirements, design analysis and performance characteristics are described. The antenna's shallow profile makes it attractive either as a "paste-on" or flush-mounted type radiator. Near-hemispherical radiation coverage is provided.
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