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Results 301 - 350 of 643
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Prokhorov M D - - 2003
For the cases of spontaneous respiration and paced respiration with a fixed frequency and linearly increasing frequency, we investigate synchronization between three main rhythmic processes governing the cardiovascular dynamics in humans, namely, the main heart rhythm, respiration, and the process whose fundamental frequency is close to 0.1 Hz. The analysis ...
Joyce E - - 2003
Some species of bacteria produce colonies and spores which agglomerate in spherical clusters (Bacillus subtilis) and this serves as a protection for the organisms inside against biocidal attack. Flocs of fine particles e.g. clay can entrap bacteria which can also protect them against the biocides. It is because of problems ...
Ernst Matthias - - 2003
Low-power XiX proton decoupling under fast magic-angle spinning is introduced. The method is applicable if the MAS frequency exceeds the proton-proton interactions. For rigid organic solids this is the case for MAS frequencies above approximately 40 kHz. It is shown that the quality of the decoupling as well as the ...
Kurokawa Yoshika - - 2003
This study is a reexamination of the possibility that exposure to extremely low frequency alternating magnetic field (ELF-MF) may influence heart rate (HR) or its variability (HRV) in humans. In a wooden room (cube with 2.7-m sides) surrounded with wire, three series of experiments were performed on 50 healthy volunteers, ...
O'Suilleabhain Padraig E - - 2003
BACKGROUND: Thalamic deep brain stimulation ameliorates essential and parkinsonian tremors refractory to medications. Stimulus voltage, polarity configuration, frequency, and pulsewidth can each be adjusted in order to optimize tremor control and maximize battery life. The relative impacts of these programmable variables have not previously been quantified. METHODS: The thalamus of ...
Aoyagi Naoko - - 2003
The effects of such behavioral factors as physical activity, food intake, and circadian rhythm on long-term heart rate variability (HRV) in humans remain poorly understood. We therefore studied their effects on HRV using a constant-routine protocol that included simultaneous core body temperature (CBT) correction. Seven healthy subjects completed the constant-routine ...
Cimponeriu Adrian - - 2003
First identified in the 1930s (Ferris et al., 1936 and Wiggers and Wegria, 1939), the concept of vulnerability applies perfectly to biological oscillators. We can safely say that vulnerability is an inherent property of any excitable media. The duration of vulnerable period (VP) (the time interval during which single stimuli ...
Sharott Andrew - - 2003
Primary orthostatic tremor (POT) is a rare disorder characterised by an intense sense of unsteadiness upon standing and a 16-Hz tremor in which the timing between tremor bursts in different muscles (unilateral and bilateral) remains constant. Hitherto, similar EMG activity has not been described in healthy subjects and it has ...
Kreiman Jody - - 2003
Vocal tremors characterize many pathological voices, but acoustic-perceptual aspects of tremor are poorly understood. To investigate this relationship, 2 tremor models were implemented in a custom voice synthesizer. The first modulated fundamental frequency (F0) with a sine wave. The second provided irregular modulation. Control parameters in both models were the ...
Jaberzadeh Shapour - - 2003
Spectral analysis of jaw acceleration confirmed that the human mandible 'trembles' at a peak frequency around 6 Hz when held in its rest position and at other stationary jaw openings. The 6 Hz tremor increased during very slow movements of the mandible, but other lower-frequency peaks became prominent during more ...
Tubani Luigi - - 2003
Eight patients with cluster headache were studied by evaluating the heart rate variability on the basis of 24-hour ECG monitoring performed during attacks (critic periods) to demonstrate if any imbalance of the autonomic nervous system was present and to determine its temporal correlation, if any, with the attack. The same ...
Nadareishvili K Sh - - 2002
Temporal and spectral parameters of heart rate variability were studied as criteria for classification of mature Chinchilla rabbit population according to their basal neurovegetative status. The absolute values of total spectral power density and individual frequency bands differed significantly in vagotonics and sympathotonics. However, standardized spectral power distributions in high-, ...
De Biasi Mariella - - 2002
Most visceral organs are under the control of the autonomic nervous system (ANS). Information on the state and function of these organs is constantly relayed to the central nervous system (CNS) by sensory afferent fibers. The CNS integrates the sensory inputs and sends neural commands back to the organ through ...
Min Seong-Won - - 2002
BACKGROUND: The aim of the current study was to investigate the changes in the power spectral pattern of the heart rate variability of fetal lambs during acute hypoxia and the possible value of power spectral analysis as a quantitative fetal monitoring method. METHODS: Acutely instrumented eight fetal lambs in the ...
Burgess Don E - - 2003
This study explores the functional association between renal sympathetic nerve traffic (NT) and arterial blood pressure (BP) in the very-low-frequency range (i.e., <0.1 Hz). NT and BP (n = 6) or BP alone (n = 17) was recorded in unanesthetized rats (n = 6). Data were collected for 2-5 h, ...
Dromey Christopher - - 2002
The effect of tremor on phonation is to modulate an otherwise steady sound source in its amplitude, fundamental frequency, or both. The severity of untreated vocal tremor has been reported to change under certain conditions that may be related to muscle tension. In order to better understand the phenomenon of ...
Hoeland K - - 2002
Innovative fibre-optic sensor technology for measuring the movement of the myocardial walls, and from this the heart chamber volumes, was developed. An optical fibre, with a mirror at its end, is inserted into a catheter located in the heart. An opto-electrical control unit positioned outside the heart contains both the ...
Le Mével Jean-Claude - - 2002
This study was conducted on unanesthetized rainbow trout equipped with two ECG electrodes and with an intracerebroventricular (i.c.v.) micro-guide. The ECG signal was recorded during three experimental sessions of 30 min and the heart rate variability (HRV) spectral analysis was performed during stabilized periods of recording. The first recording session ...
Takanokura Masato - - 2002
To investigate the influence of gravity on physiological tremor during a holding stretch of the finger, tremor during immersion of the finger in liquids was measured. Liquids with various densities and various coefficients of viscosity were used. Tremor was detected using an acceleration sensor, and power spectrum analysis was performed ...
Frydrychowski Andrzej F - - 2002
This paper presents technical foundations for a new technique of near-infrared transillumination-backscattering sounding, which is designed to enable noninvasive detection and monitoring of changes in the width of the subarachnoid space (SAS) and magnitude of cerebrovascular pulsation in humans. The key novelty of the technique is elimination of influence of ...
Malliani Alberto - - 2002
Power spectrum analysis of cardiovascular signal variability, and in particular of the RR period (heart rate variability), is a widely used procedure for the investigation of autonomic cardiovascular control and/or target function impairment. However, a correct methodology is essential to extract the information embedded in the frequency domain. This article ...
Yang Tsui Fen - - 2002
OBJECTIVE: The prevalence of bowel and bladder dysfunction, hyperhidrosis, and poor cardiopulmonary endurance is higher for children with cerebral palsy than for the general population. The purpose of this study was to investigate the autonomic function for patients with cerebral palsy. DESIGN: Thirty patients with cerebral palsy and 30 control ...
Burne J A - - 2002
This study statistically evaluated a set of commonly measured tremor parameters to determine their individual and combined ability to discriminate between essential tremor (ET) and Parkinsonian tremor (PT). Accelerometer and surface electromyographic (EMG) records of moderate to severe upper limb tremor in 20 patients with ET and 22 patients with ...
Van den Aardweg Joost G - - 2002
The background of this study was the hypothesis that respiratory variability is influenced by chemoreflex regulation. In search for periodicities in the variability due to instability of the respiratory control system, spectral analysis was applied to breath-to-breath variables in 19 healthy subjects at rest. During room-air breathing, coherent oscillations in ...
Moriya K - - 2002
Six emu hatchlings were non-invasively measured for electrocardiogram (ECG) from their chest wall using flexible electrodes, and the instantaneous heart rate (IHR) was determined from ECG throughout the first week of post-hatching life. Although the baseline heart rate (HR) was low, approximately 100-200 beats per min (bpm), compared with chick ...
Cammann Henning - - 2002
Spectral analysis of R-R Interval time series is increasingly used to determine periodic components of heart rate variability (HRV). Particular diagnostic relevance is assigned to a low-frequency (LF) component, associated with blood pressure regulation, and a high-frequency (HF) component, also referred to as respiratory sinus arrhythmia (RSA) in the HRV ...
Burkhard Pierre R - - 2002
Based on the hypothesis that rhythmical, tremor-like movements produced by normal subjects might be influenced by similar central oscillatory neuronal networks believed to determine the features of the pathologic tremors of Parkinson's disease (PD) or Essential Tremor (ET) patients, we examined the neurophysiological characteristics of a tremor mimicked by normal ...
Schapker Heidi - - 2002
Most animals assess the environment in which they live and alter their behavior according to various stimuli. When the animal does not make significant behavioral changes, as measured by bodily movements, the animal may be characterized as unresponsive to a given stimulus. This study demonstrates that when behavioral movements of ...
Matsuoka Shingo - - 2002
A respiratory and activity recording system has been developed for monitoring health conditions and living patterns, such as activity/rest time periods and general activity level. The system employs a piezoelectric sensor, a low-power operational amplifier, a low-power 8-bit microcomputer and a 512 KB EEPROM. The piezoelectric sensor, whose electrical polarization ...
Sollers John J JJ - - 2002
Recently, time-frequency analysis has become very popular for examining non-stationary time series and for researching fast changing phenomena. We used the smoothed-pseudo Wigner-Ville distribution to model the underlying dynamic autonomic nervous system changes during the intracarotid sodium amobarbital (ISA) or so-called Wada test. The Wada test involves injecting sodium amobarbitol ...
Ueda Toshiyuki - - 2002
Heart rate (HR) variability is important with respect to disease prognosis and the effects of drugs. Lorenz scatterplots provide a simple way to evaluate HR variability visually. The relation of Lorenz scatterplots to frequency-domain HR variability was examined in 75 Holter recordings and in simulated HR trends. The length of ...
Seps B - - 2002
During parabolic flight short periods of microgravity and hypergravity are created. During standing position time domain analysis showed higher vagal modulation of the autonomic nervous system in microgravity compared to hypergravity. We hypothesised that this behaviour could better be unravelled by analysis of frequency domain heart rate variability (HRV) techniques. ...
Zhuravlev Yuri E - - 2002
BACKGROUND: Quantitative analysis of fetal heart rate variability (HRV) can be used to investigate the neural control mechanisms of fetal cardiac activity. However, conventional power spectrum methods do not reveal the full complexity of the time-varying sympatho-vagal balance in the fetus. AIM: This study was carried out to explore alternative ...
Gamero L G - - 2002
Analysis of heart rate variability (HRV) is a valuable, non-invasive method for quantifying autonomic cardiac control in humans. Frequency-domain analysis of HRV involving myocardial ischaemic episodes should take into account its non-stationary behaviour. The wavelet transform is an alternative tool for the analysis of non-stationary signals. Fourteen patients have been ...
Brixius K - - 2001
BACKGROUND: Force of contraction (FOC) frequency-dependently increases in multicellular muscle strip preparations of human nonfailing myocardium, whereas FOC declines in human failing myocardium with increasing stimulation frequency. We investigated whether these characteristics can be observed in single isolated myocytes. METHODS AND RESULTS: Isolated multicellular muscle strip preparations and single isolated ...
Larsen P D - - 2001
In a group of spontaneously breathing anaesthetized subjects, we examined the ability of simple spectral and non-linear methods to detect the presence of cardioventilatory coupling in heart rate time series. Using the proportional Shannon entropy (H(RI-1)) of the RI(-1) interval (interval between inspiration and the preceding ECG R wave) as ...
Chan H L - - 2001
The spectral characteristics of heart rate variability (HRV) are related to the modulation of the autonomic nervous system. As the physiological condition is changed by such external stimuli such as drugs, postural changes, and anesthesia, or by internal deregulation such as in syncope, adjective autonomic responses could alter HRV characteristics. ...
Iyengar AKS - - 2001
Quantification of heart valve leaflet deformation during the cardiac cycle is essential in understanding normal and pathological valvular function, as well as in the design of replacement heart valves. Due to the technical complexities involved, little work to date has been performed on dynamic valve leaflet motion. We have developed ...
Masaoka Y - - 2001
Respiratory patterns are influenced by cortical and limbic factors and generated by a complex interaction between metabolic requirements and their behavioral effects. Our previous results showed that the temporal pole and the amygdala in the limbic system are related to anxiety and associated with an increase of respiratory frequency, especially ...
Sláma K - - 2001
Regulation of autonomic physiological functions has been investigated by means of multisensor electronic methods, including electrocardiographic recording of heartbeat, strain-gauge recording of extracardiac hemocoelic pulsations (EHPs), anemometric recording of air passage through spiracles and respirographic recording of O(2) consumption and CO(2) output. Pupae of Cydia exhibit continuous respiration without remarkable ...
Vaillancourt D E - - 2001
OBJECTIVES: The study examines the time-dependent structure of force tremor to investigate two hypotheses: (1), the regularity of tremor can help in discriminating normal aging from that of Parkinson's disease (PD); and (2), there is increased tremor regularity with increases in the severity of PD. METHODS: Eight young (21-29 years), ...
Takanokura M - - 2001
The acceleration signal produced by physiological tremor from four different upper limb segments (the finger, hand, forearm and upper limb) was measured by an acceleration sensor during holding posture and was analyzed by power spectrum analysis. Two prominent peaks appeared in the power spectrum, suggesting that the tremor in the ...
Baillard C - - 2001
Heart rate variability (HRV) can be assessed through a time frequency analysis, the smoothed pseudo Wigner-Ville transformation (SPWVT). Such an analysis has allowed the calculation of ICF, a frequential index, extremely sensitive to the modulation of the sympatho-vagal balance. The use of ICF has been applied in the present study ...
Fallen E L - - 2001
The frequency composition of a continuous time series of R-R intervals may be viewed as the phasic output of a central processing system intimately dependent on sensory input from a variety of afferent sources. While different measures of heart rate variability permit a glimpse into the autonomic efferent limb of ...
Accurso V - - 2001
Cardiovascular neural regulation is an integrated response to a continuous interaction of inhibitory and excitatory stimuli. Neural control of the circulation appears to be coded simultaneously in different modalities as amplitude (strength of signal or tonic activity) and frequency (oscillatory or phasic activity). Changes in tonic activity appear to be ...
Delyukov A - - 2001
Meteorotropic associations of heart rate (HR) and HR variability (HRV) were investigated in a clinically healthy 48-year-old man in Kiev. His electrocardiogram (ECG) was determined over 50 days by fitting him with an ambulatorily wearable device; various natural physical environmental variables were also monitored. The mean inter-beat interval, the standard ...
Kettunen J - - 2001
We examined the use and potential of quantifying instantaneous heart rate variability (HRV) using a joint time-frequency and time-domain methods. These new techniques are promising, because they provide tools to quantify nonstationary, beat-by-beat changes in HRV components, and are therefore flexible with respect to the design of experimental protocols. A ...
Kohsaka M - - 2001
To investigate the effects of evening bright light on the autonomic nervous system, heart rate variability (HRV) during sleep was analyzed in dim light (DL) and bright light (BL) conditions. We recorded polysomnography in nine healthy young women aged 20-21 years. Time series of % delta power was calculated in ...
Zaza A - - 2001
Clinical indexes of autonomic activity are based on the analysis of sinus cycle length and of its variability. A common assumption underlying this practice is that neural activity and cycle length may be linearly related. Recent experimental evidence suggests that such an assumption may not be correct; indeed, the relation ...
Deuschl G - - 2001
Tremor is defined as rhythmic oscillatory activity of body parts. Four physiological basic mechanisms for such oscillatory activity have been described: mechanical oscillations; oscillations based on reflexes; oscillations due to central neuronal pacemakers; and oscillations because of disturbed feedforward or feedback loops. New methodological approaches with animal models, positron emission ...
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