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Approved for public release; distribution is unlimited / The objective of this thesis is to synthesize signals with a dynamically change power spectral density, in a SDR transmitter, utilizing the most appropriate channels, modulation schemes and transmission rates for communication, based on the noise profile (AWGN plus interferences) of the link, in order to achieve performance within some predefined acceptable levels. The objective is obtained by simulation. / Major, Hellenic Army

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Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 208-214)

Experiments aimed at elucidating the identity of antigenic metabolites of practolol, using in vitro generated practolol metabolites and sera from practolol patients, were unsuccessful as none of the sera tested contained measurable concentrations of antimetabolite antibodies. Collaborative experiments with workers who had originally established the technique also failed to detect such antibodies. It was concluded, after follow up studies, that the active sera must have been used up or damaged during the original investigations. Rabbits and guinea-pigs, injected with the protein bound practolol metabolites did not respond by synthesising antimetabolite antibodies. The probable reason for the lack of response was the low concentration of hapten binding (1 metabolite molecule/6 protein molecules). A ratio of at least 10:1 is normally used in such experiments and ratios of greater than 100:1 are not uncommon. Neither in vitro generated metabolites of practolol nor chemical analogues, had any effect on human skin fibroblast growth or collagen synthesis in vitro. In contrast, practolol, propranolol and paracetamol all inhibited these fibroblasts functions in a dose related fashion. Cells from uninvolved skin of a psoriasis patient were more sensitive to the inhibitory actions of the two 3-receptor blocking drugs than fibroblasts obtained from a control volunteer but were less sensitive to paracetamol indicating a variation in the response to 3-receptor blocking drugs and that such changes in sensitivity need not be paralleled by chemically related compounds such as paracetamol. Practolol was not taken up by the fibroblasts to any great extent indieating that its site of action was the plasma membrane. Uptake of leucine was inhibited to the same extent as collagen synthesis suggesting that practolol may interfere with protein synthesis by limiting substrate availability. In vitro morphological studies are consistent with the idea that the three drugs act by different mechanisms although further studies are necessary to confirm this. The following conclusions can be drawn from the experimental findings. - The side effects of practolol are more likely to have been due to the parent molecule than to a metabolite. - The action of practolol is likely to have been an inhibitory, rather than a stimulatory, one. - Susceptible patients have an increased sensitfvity to practolol which could be reflected in the response of fibroblasts from such patients in vitro.

The results of a feasibility study of some new methods for reducing the bandwidth required for transmission of commercial-quality television are described in this thesis. It is shown that television requires a wide transmission bandwidth because of the broad frequency spectrum obtained in scanning scenes which contain abrupt changes of brightness at edges. An efficient method of coding these edges is therefore sought. The properties of the Gabor-type hologram are studied and it is shown that holograms may be used advantageously to code the picture edge information. A two-channel system is proposed and its construction and testing described. The low-frequency information is transmitted in conventional form on one channel and the high-frequency information in hologram form on the other channel. The test results support the theoretical prediction that the system can transmit television pictures with reduced bandwidth. However, the system is shown to have practical disadvantages largely caused by the necessity of making electro-optical conversions which cannot be performed in real time. In one of the alternative systems proposed here, a reduced bandwidth is made possible by transmitting the low-frequency information conventionally, and the edge pattern is scanned in a vertical direction to transmit the high frequencies. In a practical test, the system gave a bandwidth compression ratio of 6:1. As a basis for another possible system it is shown that because the edge pattern of typical pictures occupies only a small fraction of the raster area and exhibits a high degree of spatial correlation, bandwidth compression could be achieved by transmitting only this edge information. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This thesis is part of a feasibility study concerned with the application of the Gabor Hologram to a proposed method of bandwidth compression of television (video) signals obtainable by scanning a restricted class of two tone pictures: the experimental work consists of producing and improving on the Gabor type Holograms and demonstrating the reconstruction. The proposed television system will employ two channels. One channel would be used to transmit the signal obtained by scanning the picture normally; the bandwidth allowed for this channel, though, would be much less than the normal bandwidth: the other channel of equally reduced bandwidth would be used to transmit the signal obtained, again by normal scanning, from the Hologram. At the receiver, optical superposition of the two pictures obtained from the two channels would be made. For a certain restricted class of two tone pictures the distortion produced at the receiver by this method of picture transmission is anticipated to be negligible. The Fourier transform property of the Hologram is specially developed in order to complement the two channel television system. Considering the transform point of view it has been shown theoretically that the reconstruction lens suggested by Gabor is not necessary for the two step imaging process and a lensless system has been developed. It is demonstrated that better quality results can be obtained by using the modified process. In the experimental setup a positive lens necessary to widen the laser beam is used. The effect of the noisy Airy rings created by this lens is studied and a pinhole method of removing the noise has been suggested and its effectiveness demonstrated experimentally. Finally some examples of two step imaging using the modified lensless system are given. The detailed account of the experimental work is given to facilitate future work. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate