The effects of lossy compression on diagnostically relevant seizure information in EEG signals.

This paper examines the effects of compression on EEG signals, in the context of automated detection of epileptic seizures. Specifically, it examines the use of lossy compression on EEG signals in order to reduce the amount of data which has to be transmitted or stored, while having as little impact as possible on the information in the signal relevant to diagnosing epileptic seizures. Two popular compression methods, JPEG2000 and SPIHT, were used. A range of compression levels was selected for both algorithms in order to compress the signals with varying degrees of loss. This compression was applied to the database of epileptiform data provided by the University of Freiburg, Germany. The real-time EEG analysis for event detection automated seizure detection system was used in place of a trained clinician for scoring the reconstructed data. Results demonstrate that compression by a factor of up to 120:1 can be achieved, with minimal loss in seizure detection performance as measured by the area under the receiver operating characteristic curve of the seizure detection system.

Internal dynamics of human ubiquitin revealed by 13C-relaxation studies of randomly fractionally labeled protein.

The use of random, fractional 13C-enrichment combined with low pass filtration has allowed the determination of NMR relaxation parameters at an unprecedented number of sites within recombinant human ubiquitin. Essentially complete 1H, 13C, and 15N resonance assignments for the protein are reported. Carbon spin lattice and heteronuclear NOE relaxation data have been analyzed in the context of the Lipari-Szabo "model free" formalism. The generalized order parameters for 56 main chain alpha C-H vectors have been determined and are found to correspond to the highly restricted motion seen in previous studies of the motion of amide N-H vectors. In distinct contrast, the analysis presented here indicates an unexpected range of dynamics within the interior of the protein. The generalized order parameters of 45 methyl groups of human ubiquitin have been determined. The methyl groups of Thr and Ala residues show generalized order parameters ranging from the Woessner limit (0.111) to below 0.01. Generalized order parameters for all methyl groups of the seven isoleucine residues were determined. With one exception, the generalized order parameters of the gamma methyls were equal to or greater than the corresponding delta methyls, indicating higher mobility away from the main chain. Generalized order parameters for 11 methyl groups of leucine residues were also determined. In six of the seven cases where the generalized order parameters of both prochiral methyl groups were determined, the pro-R methyl consistently shows a higher value than the pro-S methyl group. Generalized order parameters for seven methyl groups of four valines were also determined. There is no apparent correlation of methyl group prochirality with the value of the generalized order parameter. These data have several implications and generally indicate that the interior of the protein is heterogeneously dynamic.