Noninvasive brain-actuated control of a mobile robot by human EEG

Brain activity recorded noninvasively is sufficient to control a mobile robot if advanced robotics is used in combination with asynchronous electroencephalogram (EEG) analysis and machine learning techniques. Until now brain-actuated control has mainly relied on implanted electrodes, since EEG-based systems have been considered too slow for controlling rapid and complex sequences of movements. We show that two human subjects successfully moved a robot between several rooms by mental control only, using an EEG-based brain-machine interface that recognized three mental states. Mental control was comparable to manual control on the same task with a performance ratio of 0.74.     

Second-order advantage achieved with four-way fluorescence excitation-emission-kinetic data processed by parallel factor analysis and trilinear least-squares. Determination of methotrexate and leucovorin in human urine

Four-way fluorescence data recorded by following the kinetic evolution of excitation-emission fluorescence matrices (EEMs) have been analyzed by parallel factor analysis and trilinear least-squares algorithms. These methodologies exploit the second-order advantage of the studied data, allowing analyte concentrations to be estimated even in the presence of an uncalibrated fluorescent background. They were applied to the simultaneous determination of the components of the anticancer combination of methotrexate and leucovorin in human urine samples. Both analytes were converted into highly fluorescent compounds by oxidation with potassium permanganate, and the kinetics of the reaction was continuously monitored by recording full EEM of the samples at different reaction times. A commercial fast scanning spectrofluorometer has been used for the first time to measure the four-way EEM kinetic data. The rapid scanning instrument allows the acquisition of a complete EEM in 12 s at a wavelength scanning speed of 24 000 nm/min. The emission spectra were recorded from 335 to 490 nm at 5-nm intervals, exciting from 255 to 315 nm at 6-nm intervals. Ten successive EEMs were measured at 72-s intervals, to follow the fluorescence kinetic evolution of the mixture components. Good recoveries were obtained in synthetic binary samples and also in spiked urine samples. The excitation, emission, and kinetic time profiles recovered by both chemometric techniques are in good agreement with experimental observations.     

Electroplated Au-GaAs1?xPx and Au-Ga1?xAlxAs Schottky barriers

A novel technique based on pulse electroplating and surface treatment with very slow etching rate solutions has been applied to fabricate Au Schottky barriers on GaAs1?xPx and Ga1?xAlxAs. Device characteristics are compared to the behaviour of vacuum-deposited barriers. The present technique allows a simple and fast procedure to obtain Schottky barriers for material evaluation and device applications.     

New learning rules for the ASSOM network

The ASSOM is a self-organising neural network with the capability of adapting to linear subspaces. Here we propose two new methods to train the ASSOM network. A nonlinear system of equations is derived for network training. This system can be solved by a gradient-based approach or by the Levenberg–Marquardt method. Each of these two approaches gives a different learning rule. A comparison is carried out among the original Kohonens method and the proposed learning rules. Experimental results are reported, including a convergence speed experiment and a speech processing application, which show that the new learning rules have better performance than the original one.     

Input-output statistical independence in divisive normalization models of V1 neurons

Simoncelli and co-workers have proposed statistically-derived nonlinear divisive normalization models of the primary visual cortex (V1) that are consistent with the hypothesis that sensory systems are adapted to the signals to which they are exposed. In this paper, we present a more rigorous mathematical formulation and analysis of these statistically-derived models in terms of mutual information as a metric for statistical independence. We prove that the ad hoc choice of divisive normalization parameters proposed by Simoncelli and co-workers does not guarantee statistical independence between the output responses, but interestingly such choice does guarantee that each output response is statistically independent of almost all the linear inputs. This holds for the two different models of natural image statistics analysed theoretically, and is consistent with empirical results obtained on a set of natural images.     

Wideband numerical modeling for vertical-cavity surface-emitting laser Bragg reflectors

We present a novel, to our knowledge, scheme for vertical-cavity surface-emitting laser Bragg reflectors modeling in wideband systems, which notably improves accuracy and numerical efficiency. These Bragg reflectors are characterized as digital filters and then are approximated by use of autoregressive moving-average models. The features of the models are analyzed in terms of the predicted error in the frequency domain, keeping it below 0.1% over a 85-nm range. The numerical structure allows the Bragg reflectors to be integrated accurately into dynamic models of tunable lasers and amplifiers.     

Surfactant to dye binding degree-based methodology for the determination of ionic amphiphilic compounds

A new analytical measurement parameter based on the effect of amphiphilic substances on the degree of binding of a surfactant to dye molecules, which induce the formation of surfactant premicellar aggregates, is presented. The theory for dye-surfactant intermolecular interactions in mixed surfactant systems, which assumes a mononuclear model for the formation of dye-induced premicellar aggregates, has been used to derive an expression that provides linear calibrations for the determination of amphiphilic compounds. The dye-surfactant interactions involved have been investigated, and the variables affecting the measurement analytical parameter have been discussed. The analytical applicability of the surfactant-dye binding degree method is demonstrated by quantifying major anionic surfactants at the nanograms-per-milliliter level and determining the total concentration of these amphiphilic substances in sewage samples (average recoveries ranged from 98 to 102%).     

A comparative study of anodic tantalum pentoxide and high-pressure sputtered titanium oxide

In this work we present a new method to fabricate improved TiO₂ films by using a high-pressure sputtering system. In order to minimize the damage induced in the substrate surface by the ion bombardment, a high chamber pressure of 100 Pa is used, which is very much higher than typical values in conventional systems. We present results obtained by X-ray diffraction and FTIR spectroscopy. Moreover, we will compare the properties of the resulting TiO₂-insulator-metal capacitors with those of anodic Ta₂O₅. Very thin films of TiO₂ have been obtained with a very promising quality for future electron device fabrication.