Impedance Plethysmography as an Alternative Measure of Reactive Hyperemia.

Peripheral vascular flow in response to induced reactive hyperemia of the radial artery is used as a benchmark for non-invasive assessment of the endothelial function. As an alternative to standard modalities, this study investigates the suitability of impedance plethysmography to estimate peripheral vascular flow variations associated with the reactive hyperemia process. Results indicate a consistent variation of bio-impedance during the reactive hyperemia process at higher measurement frequencies and these variations are compatible with a standard tissue impedance model. Further, calculated features of bioimpedance has shown the capability of differentiating healthy and diabetic groups which is useful in estimating the endothelial dysfunction.

Using Biosignals for Objective Measurement of Presence in Virtual Reality Environments.

The concept of 'presence' in the context of virtual reality (VR) refers to the experience of being in the virtual environment, even when one is physically situated in the real world. Therefore, it is a key parameter of assessing a VR system, based on which, improvements can be made to it. To overcome the limitations of existing methods that are based on standard questionnaires and behavioral analysis, this study proposes to investigate the suitability of biosignals of the user to derive an objective measure of presence. The proposed approach includes experiments conducted on 20 users, recording EEG, ECG and electrodermal activity (EDA) signals while experiencing custom designed VR scenarios with factors contributing to presence suppressed and unsuppressed. Mutual Information based feature selection and subsequent paired t-tests used to identify significant variations in biosignal features when each factor of presence is suppressed revealed significant (p < 0.05) differences in the mean values of EEG signal power and coherence within alpha, beta and gamma bands distributed in specific regions of the brain. Statistical features showed a significant variation with the suppression of realism factor. The variations of activity in the temporal region lead to the assumption of insula activation which may be related to the sense of presence. Therefore, the use of biosignals for an objective measurement of presence in VR systems indicates promise.

Association Between DMSO and Sugars in the Sperm Cryopreservation of Pacu.

　　BACKGROUND: The cryopreservation protocol that has been developed exclusively for the preservation of the sperm of the species different. OBJECTIVE: this study was to evaluate the effect of the association of 10% DMSO with trehalose, raffinose, sucrose and lactose concentrations on the sperm cells of Piaractus mesopotamicus. MATERIALS AND METHODS: Sperms were collected from the animals through abdominal massage. The samples were diluted in the Beltsville Thawing Solution without different concentrations of other sugars (test conditions). Sixty days after the cryopreservation, cell movement analysis was performed using CASA. RESULTS: The results revealed that the parameters for total motility and motility period were superior when 100mM raffinose (P <0.05). The lateral displacement of the head was observed to be improved was 100mM lactose, 150mM sucrose and 150mM raffinose (P <0.05) as compared to treatment wherein lactose (0mM) was omitted. CONCLUSION: the results of our study indicated that the ideal parameters for cryopreservation, were obtained when the cryopreservation fluid contained 100mM raffinose in association with DMSO.

Limitations in the rapid extraction of evoked potentials using parametric modeling.

The rapid extraction of variations in evoked potentials (EPs) is of great clinical importance. Parametric modeling using autoregression with an exogenous input (ARX) and robust evoked potential estimator (REPE) are commonly used methods for extracting EPs over the conventional moving time average. However, a systematic study of the efficacy of these methods, using known synthetic EPs, has not been performed. Therefore, the current study evaluates the restrictions of these methods in the presence of known and systematic variations in EP component latency and signal-to-noise ratios (SNR). In the context of rapid extraction, variations of wave V of the auditory brainstem in response to stimulus intensity were considered. While the REPE methods were better able to recover the simulated model of the EP, morphology and the latency of the ARX-estimated EPs was a closer match to the actual EP than than that of the REPE-estimated EPs. We, therefore, concluded that ARX rapid extraction would perform better with regards to the rapid tracking of latency variations. By tracking simulated and empirically induced latency variations, we conclude that rapid EP extraction using ARX modeling is only capable of extracting latency variations of an EP in relatively high SNRs and, therefore, should be used with caution in low-noise environments. In particular, it is not a suitable method for the rapid extraction of early EP components such as the auditory brainstem potential.

Evaluation of wavelet techniques in rapid extraction of ABR variations from underlying EEG.

The aim of this study is to analyse an effective wavelet method for denoising and tracking temporal variations of the auditory brainstem response (ABR). The rapid and accurate extraction of ABRs in clinical practice has numerous benefits, including reductions in clinical test times and potential long-term patient monitoring applications. One method of achieving rapid extraction is through the application of wavelet filtering which, according to earlier research, has shown potential in denoising signals with low signal-to-noise ratios. The research documented in this paper evaluates the application of three such wavelet approaches on a common set of ABR data collected from eight participants. We introduced the use of the latency-intensity curve of ABR wave V for performance evaluation of tracking temporal variations. The application of these methods to the ABR required establishing threshold functions and time windows as an integral part of the research. Results revealed that the cyclic-shift-tree-denoising performed superior compared to other tested approaches. This required an ensemble of only 32 epochs to extract a fully featured ABR compared to the 1024 epochs with conventional ABR extraction based on linear moving time averaging.