Development of a low-cost silica-titania optical platform for integrated photonics applications.

This paper investigates a highly attractive platform for an optical waveguide system based on silica-titania material. The paper is organized into two parts. In the first part, an experimental study on the development of an optical waveguide system is conducted via the sol-gel dip-coating method, and the optical characterization of the waveguide system is performed at a visible wavelength. This system is capable of operating from visible to near-IR wavelength ranges. The experimental results prove the dominance of this waveguide platform due to its low-cost, low loss, and easy to develop integrated optics systems. The numerical analysis of a one-dimensional Photonic crystal waveguide optical filter based on the silica-titania platform is considered in the second part of the paper by utilizing the 2D-finite element method (2D-FEM). A Fabry-Perot structure is also analyzed for refractive index sensing applications. We believe that the results presented in this work will be valuable in the realization of low-cost photonic integrated circuits based on the silica-titania platform.

Real-time sleep-wake scoring in the rat using a single EEG channel.

A new method of analysis of sleep in the rat based on the electrocorticogram (ECoG) is described. Three states, awake (W), nonrapid eye movement (NREM) and rapid eye movement (REM) sleep are automatically classified by the system. After amplification of the ECoG over a restricted bandwidth (3.18-25 Hz) and sampling at 512 Hz, the data are processed in 8-second epochs by a microcomputer, which generates three statistical and two harmonic variables. Each 8-second epoch is thus compressed into five numerical values occupying 10 bytes of memory. Epochs for each state of vigilance are identified by an expert observer to produce three reference models. The program classifies each epoch into the appropriate state by the least quadratic distance. The system was validated by comparing the results with a visual analysis of polygraph recordings. The agreement between the program and the two independent scorers for 24-hour tracings of six rats was 83% for REM sleep, 96% for W and 97% for NREM sleep.

Adult rat vigilance states discrimination by artificial neural networks using a single EEG channel.

Two multilayer neural networks were designed to discriminate vigilance states (waking, paradoxical sleep, and non-REM sleep) in the rat using a single parieto-occipital EEG derivation. After filtering (bandwidth 3.18-25 Hz) and digitization at 512 HZ, the EEG signal was segmented into eight second epochs. Five variables (three statistical, two temporal) were extracted from each epoch. The first network computed an epoch by epoch classification, while the second network also utilized contextual information from contiguous epochs. A specific postprocessing procedure was developed to enhance the vigilance state discrimination of the neural networks designed and especially paradoxical sleep state estimation. The classifications made by the networks (with or without the postprocessing procedure) for six rats were compared to these made by two human experts using EMG and EEG informations on 63,000 epochs. High rates of agreement (> 90%) between humans and neural networks classifications were obtained. In view of its development possibilities and its applicability to other signals, this method could prove of value in biomedical research.

Continuous quantitative monitoring of spontaneous opiate withdrawal: locomotor activity and sleep disorders.

The time course of drug abstinence is not readily amenable to examination using intermittent observations, because abstinence is known to interfere with circadian rhythms of general activity. Accordingly, we propose a model for continuous assessment of spontaneous withdrawal without any intervention by the investigator. This model is based on the automatic recording of locomotor activity. Experiments were performed in rectangular activity cages equipped with two infrared photoelectric cells. In a parallel experiment, to confirm the locomotor activity effects, continuous monitoring of EEG activities was achieved from two cortical and one reference electrodes. Morphine dependence was induced by intraperitoneal injections of increasing doses of morphine twice daily for 10 days (from 5 up to 90 mg/kg). Behavioral and EEG activities were recorded for 8 to 10 days following the last injection of morphine. Although control rats displayed a typical locomotor activity pattern characterized by nocturnal hyperactivity that was markedly reduced during the light phase, opiate abstinent rats developed a constant motor activity during the first 3 or 4 postinjection days and that was associated with a drastic reduction of overall rapid eye movement sleep (REM) and non-REM sleep and with an increase of waking (W). Although morphine-abstinent rats slowly resumed a normal circadian cycle after the fourth day in terms of horizontal activity, REMS, NREMS and W, long-term effects were revealed by the permanent motor instability recorded during both the light and the dark phases when the total amount of photocell counts was considered, and by the perturbation of the circadian rhythm of the ratio of REM sleep to total sleep time. Automatic continuous recording of total motor behavior appears to be a useful index with which to follow, over an extended period of time, the acute and long-term consequences of opiate abstinence. Therefore, long-term withdrawal-induced changes in activity could be a suitable model for the validation of antiabstinence therapies.

IR laser induced spectral kinetics of AgGaGe3Se8:Cu chalcogenide crystals.

The possibility to operate by optical spectra near the absorption edge gap was discovered for the AgGaGe3Se8:Cu semiconducting chalcogenide crystals under influence of microsecond CO2 laser with pulse energy 60 mJ operating at wavelength 10.6 µm. An occurrence of substantial photoinduced optical density was observed at wavelengths in the spectral range of 610-620 nm. Introducing of Cu ions leads to substantial spectral asymmetry in the observed spectra. The process achieves its maximum value after the 80-120 s of CO2 laser treatment and relaxes with almost irreversible changes after the same time. The contribution of thermo heating did not exceed 5-6%. Only the irreversible changes of the sample's surface topography were observed during the CO2 laser treatment, which do not influence the treatment. So the surface states do not play a principal role and the effect is prevailingly originated from the. The observed effect may be used for control of the CO2 laser power density.

Computer-assisted ABR interpretation using the automatic construction of the latency-intensity curve.

In this paper, we present a new computerised technique for the automatic construction of the latency intensity curve (LI curve). We take a pattern recognition approach determined by a priori information. We use knowledge gained from the audiogram and from physiological considerations. Therefore, we consider all recordings at different intensities as well as results from the extraction of a single auditory brainstem response (ABR) at a given stimulus intensity. We tested our method successfully: it allows us to prevent misrecognition errors in response detection or in latency measurements. Automatic recognition of the waves and recognition by the ear, nose and throat (ENT) specialist coincided in at least 90 per cent of cases. For wave V, the average deviation between the response thresholds given by our automatic recognition algorithm and those given by the ENT specialist was 5 dB, and the average deviation of the latencies was 0.05 ms.