Ultrathin compound semiconductor on insulator layers for high performance nanoscale transistors

Over the past several years, the inherent scaling limitations of electron devices have fueled the exploration of high carrier mobility semiconductors as a Si replacement to further enhance the device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been actively studied, combining the high mobility of III-V semiconductors and the well-established, low cost processing of Si technology. This integration, however, presents significant challenges. Conventionally, heteroepitaxial growth of complex multilayers on Si has been explored. Besides complexity, high defect densities and junction leakage currents present limitations in the approach. Motivated by this challenge, here we utilize an epitaxial transfer method for the integration of ultrathin layers of single-crystalline InAs on Si/SiO2 substrates. As a parallel to silicon-on-insulator (SOI) technology14,we use the abbreviation "XOI" to represent our compound semiconductor-on-insulator platform. Through experiments and simulation, the electrical properties of InAs XOI transistors are explored, elucidating the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Importantly, a high quality InAs/dielectric interface is obtained by the use of a novel thermally grown interfacial InAsOx layer (~1 nm thick). The fabricated FETs exhibit an impressive peak transconductance of ~1.6 mS/{\mu}m at VDS=0.5V with ON/OFF current ratio of greater than 10,000 and a subthreshold swing of 107-150 mV/decade for a channel length of ~0.5 {\mu}m

Quantification of radial arterial pulse characteristics change during exercise and recovery

It is physiologically important to understand the arterial pulse waveform characteristics change during exercise and recovery. However, there is a lack of a comprehensive investigation. This study aimed to provide scientific evidence on the arterial pulse characteristics change during exercise and recovery. Sixty-five healthy subjects were studied. The exercise loads were gradually increased from 0 to 125 W for female subjects and to 150 W for male subjects. Radial pulses were digitally recorded during exercise and 4-min recovery. Four parameters were extracted from the raw arterial pulse waveform, including the pulse amplitude, width, pulse peak and dicrotic notch time. Five parameters were extracted from the normalized radial pulse waveform, including the pulse peak and dicrotic notch position, pulse Area, Area1 and Area2 separated by notch point. With increasing loads during exercise, the raw pulse amplitude increased significantly with decreased pulse period, reduced peak and notch time. From the normalized pulses, the pulse Area, pulse Area1 and Area2 decreased, respectively, from 38 ± 4, 61 ± 5 and 23 ± 5 at rest to 34 ± 4, 52 ± 6 and 13 ± 5 at 150-W exercise load. During recovery, an opposite trend was observed. This study quantitatively demonstrated significant changes of radial pulse characteristics during different exercise loads and recovery phases

Airflow Dynamics of Human Jets: Sneezing and Breathing - Potential Sources of Infectious Aerosols

10.1371/journal.pone.0059970PLoS ONE84

Cardiorespiratory Phase-Coupling Is Reduced in Patients with Obstructive Sleep Apnea

Cardiac and respiratory rhythms reveal transient phases of phase-locking which were proposed to be an important aspect of cardiorespiratory interaction. The aim of this study was to quantify cardio-respiratory phase-locking in obstructive sleep apnea (OSA). We investigated overnight polysomnography data of 248 subjects with suspected OSA. Cardiorespiratory phase-coupling was computed from the R-R intervals of body surface ECG and respiratory rate, calculated from abdominal and thoracic sensors, using Hilbert transform. A significant reduction in phase-coupling was observed in patients with severe OSA compared to patients with no or mild OSA. Cardiorespiratory phase-coupling was also associated with sleep stages and was significantly reduced during rapid-eye-movement (REM) sleep compared to slow-wave (SW) sleep. There was, however, no effect of age and BMI on phase coupling. Our study suggests that the assessment of cardiorespiratory phase coupling may be used as an ECG based screening tool for determining the severity of OSA

Apnea in preterm newborns: determinants, pathophysiology, effects on cardiovascular parameters and treatment

Apnea, especially in preterm newborns (AoP) is one of the common problems encountered at neonatal units. Numerous factors are likely to play a role in the etiology of apnea. Recent data sugest a role for genetic predisposition of AoP. It seems, that physiological rather than pathological immaturity of the respiratory, or cardiorespiratory control, play a major part in the pathophysiology of AoP. Immaturity of the brainstem, cerebral cortex, receptors of the lungs and the airways as well as of the chemoreceptors contribute to the development of apnea in preterm newborns. Several neurotransmitters (GABA, adenosin, endorphins) and their maturational changes are including in pathogenesis of apnea, too. The instability of the upper airway in preterm infants, asynchrony of musculature of the upper airway and diaphragm, pathological changes in the upper airway and malformations of the central nervous system might also contribute to the occurrence and severity of AoP. In newborns, apnea occurs more frequently in active sleep than in quiet sleep and the frequency of apnea in active sleep is higher in the warm conditions. Durations of apnea correlate with the body heat loss. Cardiovascular changes during apnea - bradycardia, peripheral vasoconstriction and various changes in peripheral blood flow and pressure occur together with changes in ECG. The standard clinical management of apnea includes non-pharmacological treatment (eliciting arousal reactions and reflex breathing by mechanical skin, or mucosa stimulations), pharmacological treatment (methylxanthines are preferred) and application of continuous positive airway pressure (CPAP) or in severe apnea - mechanical ventilation

The effect of orthostasis on recurrence quantification analysis of heart rate and blood pressure dynamics

The purpose of this paper is to investigate the effect of orthostatic challenge on recurrence plot based complexity measures of heart rate and blood pressure variability (HRV and BPV). HRV and BPV complexities were assessed in 28 healthy subjects over 15 min in the supine and standing positions. The complexity of HRV and BPV was assessed based on recurrence quantification analysis. HRV complexity was reduced along with the HRV magnitude after changing from the supine to the standing position. In contrast, the BPV magnitude increased and BPV complexity decreased upon standing. Recurrence quantification analysis (RQA) of HRV and BPV is sensitive to orthostatic challenge and might therefore be suited to assess changes in autonomic neural outflow to the cardiovascular system.M Javorka, Z Turianikova, I Tonhajzerova, K Javorka and M Baumer

The effect of orthostatic stress on multiscale entropy of heart rate and blood pressure

Cardiovascular control acts over multiple time scales, which introduces a significant amount of complexity to heart rate and blood pressure time series. Multiscale entropy (MSE) analysis has been developed to quantify the complexity of a time series over multiple time scales. In previous studies, MSE analyses identified impaired cardiovascular control and increased cardiovascular risk in various pathological conditions. Despite the increasing acceptance of the MSE technique in clinical research, information underpinning the involvement of the autonomic nervous system in the MSE of heart rate and blood pressure is lacking. The objective of this study is to investigate the effect of orthostatic challenge on the MSE of heart rate and blood pressure variability (HRV, BPV) and the correlation between MSE (complexity measures) and traditional linear (time and frequency domain) measures. MSE analysis of HRV and BPV was performed in 28 healthy young subjects on 1000 consecutive heart beats in the supine and standing positions. Sample entropy values were assessed on scales of 1–10. We found that MSE of heart rate and blood pressure signals is sensitive to changes in autonomic balance caused by postural change from the supine to the standing position. The effect of orthostatic challenge on heart rate and blood pressure complexity depended on the time scale under investigation. Entropy values did not correlate with the mean values of heart rate and blood pressure and showed only weak correlations with linear HRV and BPV measures. In conclusion, the MSE analysis of heart rate and blood pressure provides a sensitive tool to detect changes in autonomic balance as induced by postural change.Zuzana Turianikova, Kamil Javorka, Mathias Baumert, Andrea Calkovska, and Michal Javork

Short-term heart rate complexity is reduced in patients 14 with type 1 diabetes mellitus

Copyright © 2008 International Federation of Clinical Neurophysiology Published by Elsevier Ireland Ltd.Objective The aim of this study was to test whether new heart rate variability (HRV) complexity measures provide diagnostic information regarding early subclinical autonomic dysfunction in diabetes mellitus (DM). Methods HRV in DM type 1 patients (n = 17, 10f, 7m) aged 12.9–31.5 years (duration of DM 12.4 ± 1.2 years) was compared to a control group of 17 healthy matched probands. The length of R–R intervals was measured over 1 h using a telemetric ECG system. In addition to linear measures, we assessed HRV complexity measures, including multiscale entropy (MSE), compression entropy and various symbolic dynamic measures (Shannon and Renyi entropies, normalized complexity index (NCI), and pattern classification). Results HRV magnitude was significantly reduced in patients with DM. Several HRV complexity parameters (MSE at scales 2–4, Renyi entropy, NCI) were also significantly reduced in diabetics. MSE indices and compression entropy did not correlate with linear measures. Conclusions The magnitude and complexity of HRV are reduced in young patients with DM, indicating vagal dysfunction. Significance The quantification of HRV complexity in combination with its magnitude may provide an improved diagnostic tool for cardiovascular autonomic neuropathy in DM.Michal Javorka, Zuzana Trunkvalterova, Ingrid Tonhajzerova, Jana Javorkova, Kamil Javorka and Mathias Baumerthttp://www.elsevier.com/wps/find/journaldescription.cws_home/601528/description#descriptio

Changes in Heart Rate Variability and Complexity in Young Patients with Type 1 Diabetes Mellitus after A 17 Month Follow-Up

The objective of this study was to investigate short-term changes in cardiovascular autonomic dysregulation in young patients with Type 1 diabetes mellitus (DM)