84 research outputs found
Automated Risk Identification of Myocardial Infarction Using Relative Frequency Band Coefficient (RFBC) Features from ECG
Various structural and functional changes associated with ischemic (myocardial infarcted) heart cause amplitude and spectral changes in signals obtained at different leads of ECG. In order to capture these changes, Relative Frequency Band Coefficient (RFBC) features from 12-lead ECG have been proposed and used for automated identification of myocardial infarction risk. RFBC features reduces the effect of subject variabilty in body composition on the amplitude dependent features. The proposed method is evaluated on ECG data from PTB diagnostic database using support vector machine as classifier. The promising result suggests that the proposed RFBC features may be used in the screening and clinical decision support system for myocardial infarction
Cathode fall characteristics in a dc atmospheric pressure glow discharge
Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the authors and the American Institute of Physics. This article appeared in the Journal of Applied Physics and may be found at: http://link.aip.org/link/?JAPIAU/94/5504/1Atmospheric pressure glow discharges are attractive for a wide range of material-processing
applications largely due to their operation flexibility afforded by removal of the vacuum system.
These relatively new atmospheric plasmas are nonequilibrium plasmas with gas temperature around
100 °C and electron temperature in the 1–10 eV range. Their appearance is characteristically diffuse
and uniform, and their temporal features are repetitive and stable. Of the reported numerical studies
of atmospheric glow discharges, most are based on the hydrodynamic approximation in which
electrons are assumed to be in equilibrium with the local electric field. Spectroscopic and electrical
measurements suggest however that the cathode fall region is fundamentally nonequilibrium. To this
end we consider a hybrid model that treats the cathode fall region kinetically but retains a
hydrodynamic description for the region between the thin cathode fall layer and the anode. Using
this hybrid model, a helium discharge system excited at dc is studied numerically for a very wide
current density range that spans from Townsend dark discharge, through normal glow discharge, to
abnormal glow discharge. Numerical results confirm many distinct characteristics of glow
discharges and compare well with that of low-pressure glow discharges. Generic relationships, such
as that between the electric field and the current density, are also established and are in good
agreement with experimental data. This hybrid model is simple and insightful as a theoretical tool
for atmospheric pressure glow discharges
Physiological and autonomic stress responses after prolonged sleep restriction and subsequent recovery sleep in healthy young men
Purpose Sleep restriction is increasingly common and associated with the development of health problems. We investigated how the neuroendocrine stress systems respond to prolonged sleep restriction and subsequent recovery sleep in healthy young men. Methods After two baseline (BL) nights of 8 h time in bed (TIB), TIB was restricted to 4 h per night for five nights (sleep restriction, SR, n = 15), followed by three recovery nights (REC) of 8 h TIB, representing a busy workweek and a recovery weekend. The control group (n = 8) had 8 h TIB throughout the experiment. A variety of autonomic cardiovascular parameters, together with salivary neuropeptide Y (NPY) and cortisol levels, were assessed. Results In the control group, none of the parameters changed. In the experimental group, heart rate increased from 60 +/- 1.8 beats per minute (bpm) at BL, to 63 +/- 1.1 bpm after SR and further to 65 +/- 1.8 bpm after REC. In addition, whole day low-frequency to-high frequency (LF/HF) power ratio of heart rate variability increased from 4.6 +/- 0.4 at BL to 6.0 +/- 0.6 after SR. Other parameters, including salivary NPY and cortisol levels, remained unaffected. Conclusions Increased heart rate and LF/HF power ratio are early signs of an increased sympathetic activity after prolonged sleep restriction. To reliably interpret the clinical significance of these early signs of physiological stress, a follow-up study would be needed to evaluate if the stress responses escalate and lead to more unfavourable reactions, such as elevated blood pressure and a subsequent elevated risk for cardiovascular health problems.Peer reviewe
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