Statistical Analysis of Functional MRI Data in the Wavelet Domain

The use of the wavelet transform is explored for the detection of differences between brain functional magnetic resonance images (fMRI's) acquired under two different experimental conditions. The method benefits from the fact that a smooth and spatially localized signal can be represented by a small set of localized wavelet coefficients, while the power of white noise is uniformly spread throughout the wavelet space. Hence, a statistical procedure is developed that uses the imposed decomposition orthogonality to locate wavelet-space partitions with large signal-to-noise ratio (SNR), and subsequently restricts the testing for significant wavelet coefficients to these partitions. This results in a higher SNR and a smaller number of statistical tests, yielding a lower detection threshold compared to spatial-domain testing and, thus, a higher detection sensitivity without increasing type I errors. The multiresolution approach of the wavelet method is particularly suited to applications where the signal bandwidth and/or the characteristics of an imaging modality cannot be well specified. The proposed method was applied to compare two different fMRI acquisition modalities. Differences of the respective useful signal bandwidths could be clearly demonstrated; the estimated signal, due to the smoothness of the wavelet representation, yielded more compact regions of neuroactivity than standard spatial-domain testing

Trypanosomiasis challenge estimation in The Gambia using the Berenil index: Comparison between zebu and N'Dama

The Berenil provides a means of estimating the trypanosomiasis challenge presented to cattle independent of, and therefore complementary to, the collection of tsetse data and of prevalence rates of infection in cattle. In areas where trypanotolerant cattle predominate, the Berenil Index has seldom been used as an independent assessment of trypanosomiasis challenge. An experimental protocol applied to sentinel herds of trypanotolerant and trypanosusceptible cattle in three regions of different tsetse challenge in The Gambia is described. Problems associated with the standardisation of the procedure are discussed and interim results are presented. The different challenges as measured by the Berenil Index are compared with those of tsetse derived data, and also compared to the trypanosome prevalence in local cattle. The Berenil Indices produced correspond well with these methods of estimating challenge. Indices range from no treatments per year to in excess of monthly treatments, depending on region and on breef of animal. The trypanosusceptible breed shows higher indices than trypanotolerant animals. Possible explanations for this difference are discussed

Decentralized Model Predictive Control for Networks of Linear Systems with Coupling Delay

This paper presents a new dissipativity-based decentralized model predictive control strategy for networks of linear systems suffering from a bounded coupling delay. The notion of delay-robust dissipativity is introduced and applied to the development of interconnection stability conditions. The dissipation inequality of system trajectories is converted into a prognostic stability constraint for the optimization problem of model predictive control to guarantee the system stability. A recursive feasibility condition is derived for the constrained optimization problem, which is formulated in a semi-definite program. A numerical example of an interconnected three-unit process system is provided for illustrations. © 2013 Springer Science+Business Media New York