Optimal detection of visual evoked potentials

The authors consider the problem of detecting visual evoked potentials (VEP's). A matched subspace filter is applied to the detection of the VEP and is demonstrated to perform better than a number of other evoked potential detectors. Unlike single-harmonic detectors, the matched subspace filter (MSF) detector is suitable for detecting multiharmonic VEP's. Moreover, the MSF is optimal in the uniformly most powerful sense for multiharmonic signals with unknown noise variance     

'Sheltered disruption' of Neurospora crassa MOM22, an essential component of the mitochondrial protein import complex

MOM22 is a component of the protein import complex of the mitochondrial outer membrane of Neurospora crassa. Using the newly developed procedure of 'sheltered disruption', we created a heterokaryotic strain harboring two nuclei, one with a null allele of the mom-22 gene and the other with a wild-type allele. Homokaryons bearing the mom-22 disruption could not be isolated, suggesting that mom-22 is an essential gene. The mutant nucleus can be forced to predominate in the heterokaryon through the use of specific nutritional and inhibitor resistance markers. Cultivation of the heterokaryon under conditions favoring the mutant nucleus resulted in selective depletion of MOM22. MOM22-depleted cells did not grow and contained mitochondria with an altered morphology and protein composition. Protein import into isolated, MOM22-depleted mitochondria was abolished for most precursor proteins destined for all subcompartments. In contrast, precursors of MOM19, MOM22 and MOM72 became inserted normally into the outer membrane, defining a novel MOM22-independent import pathway which remained intact in mutant mitochondria. Furthermore, the specific binding of the ADP/ATP carrier to the outer membrane was unaffected, but subsequent transport across the outer membrane did not occur. Our data show that MOM22 is an essential component of Neurospora cells specifically required for the biogenesis of mitochondria.     

Nutrition and cognitive development

While ultrasound has been well accepted as an accurate test for the diagnosis of both femoral and popliteal deep venous thrombosis (DVT), its role in the detection of calf DVT has been less clear. There have been variable results between studies in the accuracy of colour Doppler or compression sonographic techniques in demonstrating calf DVT. Many of these studies have suffered from high rates of technically inadequate examinations. Power Doppler (colour Doppler energy) has a higher sensitivity than conventional colour Doppler. It should therefore allow the detection of slow venous flow in patent vessels, that may not be demonstrated by conventional colour Doppler. This should decrease the number of technically inadequate examinations as well as decreasing the false-positive rate of the test. A prospective blinded reader study was undertaken comparing power Doppler to the gold standard venography, in the diagnosis of isolated calf deep venous thrombosis (DVT). Both examinations were successfully performed in 50 patients, in whom proximal DVT had been excluded by compression ultrasonography. Fifteen patients had positive evidence of an isolated calf DVT on the gold standard technique, venography. Power Doppler demonstrated a sensitivity of 100%, a specificity of 79%, a positive predictive value of 71% and a negative predictive value of 100%, in detecting an isolated calf DVT. There were no technically inadequate ultrasound examinations. Where venous flow is demonstrated, power Doppler is a highly accurate test in excluding a calf DVT. The specificity of the test, however, is limited, as the absence of flow does not always signify a DVT.     

Chemical reactions between aluminum and fly ash during synthesis and reheating of Al-fly ash composite

Thermodynamic analysis indicates that there is the possibility of chemical reactions between aluminum melt and cenosphere fly ash particles. These particles contain alumina, silica, and iron oxide, which, during solidification processing of aluminum-fly ash composites or during holding of such composites at temperatures above the melting temperature of aluminum, are likely to undergo chemical reduction. These chemical reactions between the fly ash and molten aluminum have been studied by metallographic examination, differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and X-ray analysis after holding the aluminum-fly ash composites for different periods above the liquidus temperature. The experiments indicate that there is progressive reduction of silica and mullite in the fly ash, and formation of alumina with holding time of composites at a temperature of 850 °C. The walls of the cenosphere fly ash particles progressively disintegrate into discrete particles as the reaction progresses. The rate of chemical reaction was high at the start of holding the composite at a temperature of 850 °C, and then the rate significantly decreased with time. The reaction was almost complete after 10 hours.     

Person identification using multiple cues

This paper presents a person identification system based on acoustic and visual features. The system is organized as a set of non-homogeneous classifiers whose outputs are integrated after a normalization step. In particular, two classifiers based on acoustic features and three based on visual ones provide data for an integration module whose performance is evaluated. A novel technique for the integration of multiple classifiers at an hybrid rank/measurement level is introduced using HyperBF networks. Two different methods for the rejection of an unknown person are introduced. The performance of the integrated system is shown to be superior to that of the acoustic and visual subsystems. The resulting identification system can be used to log personal access and, with minor modifications, as an identity verification system