No description available.

No description available.

No description available.

No description available.

Speech coding at 64 and 32 Kb/s is well developed and standardized. The next bit rate of interest is at 16 Kb/s. Although. standardization has yet to be made, speech coding at 16 Kb/s is fairly well developed. The existing coders can produce good quality speech at rates as low as about 9.6 Kb/s. At present the major research area is at 8 to 4.8 Kb/s. This work deals first of all with enhancing the quality andkcomplexity of some of the most promising coders at 16 to 9.6 Kb/s as well as proposing new alternative coders. For this purpose coders operating at 16 Kb/s and 12 to 9.6 Kb/s have been grouped together and optimized for their corresponding bit rates. The second part of the work deals with the possibilities of coding the speech signals at lower rates than 9.6 Kb/s. Therefore, coders which produce good quality speech at bit rates 8 to 4.8 Kb/s have been designed and simulated. As well as designing coders to operate at rates below 32 Kb/s. it is very important to test them. Coders operating at 32 Kb/s and above contain only quantization noise and usually have large signal to noise ratios (SNR). For this reason their SNR's may be used for comparison of the coders. However, for the coders operating at 16 Kb/s and below this is not so and hence subjective testing is necessary for true comparison of the coders. The final part of this work deals with the subjective testing of 6 coders, three at 16 Kb/s and the other three at 9.6 Kb/s.

No description available.

No description available.

This thesis is concerned with the processing of time domain signals received by a single sensor. An example of such signals is the radar return, which is used in one way or another to estimate the power spectral density a frequency representation of the power of the signal in order that we can pick up and track the moving targets. since the POWER SPECTRAL DENSITY ESTIMATION is a fundamental tool in digital signal processing, the theory of the different approaches to PSDE is given in the Literature review chapter. The aim of this research is to develop a technique for the Power Spectral Density Estimation (PSDE) of multiple signals in white noise, which has high resolution capability and less frequency estimation errors. Hence, the various techniques mentioned above are tested for their detection, resolution capabilities and performance. Finally the different parameters affecting the resolution and detection capabilities of the Eigen Vector Decomposition Techniques (EVDT) for PSDE are studied in some depth.

The application of the proteomic approach has facilitated efforts directed toward the mapping of the entire Arabidopsis cell wall proteome. Proteins were sequentially extracted from purified cell walls using 0.2 M CaC1(_2) followed by a urea buffer. The extracts were resolved via large format two dimensional polyacrylamide gel electrophoresis (2-D PAGE) and were visualised via Coomassie brilliant blue staining. The aim was to identify and characterise as many cell wall proteins as possible, with the hope of identifying novel cell wall proteins. Out of 325 spots visualised on the 2-D polyacrylamide gel, 144 gave a positive protein identification representing 104 different proteins. The identified proteins were divided into 3 categories. The first category included proteins that have been previously identified as plant cell wall proteins. The second category was designated to include novel cell wall proteins (hypothetical proteins) and the third category was made up of proteins, which had recognised functions, but had never hitherto been known to be secreted to the extracellular matrix. Among the identified novel cell wall proteins there were several that shared high homology with protein kinases. These proteins possessed all the characteristics of secreted polypeptides, such as the cleavable N-terminal signal peptide, and were found to lack both the transmembrane domain and the endoplasmic reticulum retention tetrapeptides (HDEL and KDEL). These observations suggested that, as in animal cells, plant cells had extracellular protein kinase activity (phosphorylation). This was supported by the recent discovery that plant cells secrete ATP to the extracellular matrix (Thomas et al., 2000). Verification of the occurrence of extracellular protein kinase activity was further strengthened by the identification of phosphorylated bona fide cell wall proteins and stress responses caused by the depletion extracellular ATP.

No description available.