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1

Variable rate particle filters for tracking applications  

Microsoft Academic Search

Here we describe recent advances in particle filtering algorithms and models for tracking of manoeuvring objects in clutter. The methods develop on the basic variable dimension particle filtering algorithms introduced in S.J. Godsill and J. Vermaak (2004), in which a new type of dynamical model is introduced whose state variables arrive at unknown times relative to the observation process (hence

Simon Godsill; Jaco Vermaak

2005-01-01

2

Heart rate variability and its clinical application for biofeedback  

Microsoft Academic Search

The heart rate variability test gives an incredibly accurate view of the autonomic nervous systems and the variableness of the heart. It shows the state of relative health. Heart rate variability shows the correspondence between specific physiological components and the frequency spectrum. The two components are the sympathetic and parasympathetic neural systems, which originate in the brain and effect organs

Nutan D Ahuja; V. Raghavan; Vikas Lath; Ashish til; Sreejit Pillai

2004-01-01

3

Basic notions of heart rate variability and its clinical applicability.  

PubMed

Autonomic nervous system (ANS) plays an important role in the regulation of the physiological processes of the human organism during normal and pathological conditions. Among the techniques used in its evaluation, the heart rate variability (HRV) has arising as a simple and non-invasive measure of the autonomic impulses, representing one of the most promising quantitative markers of the autonomic balance. The HRV describes the oscillations in the interval between consecutive heart beats (RR interval), as well as the oscillations between consecutive instantaneous heart rates. It is a measure that can be used to assess the ANS modulation under physiological conditions, such as wakefulness and sleep conditions, different body positions, physical training and also pathological conditions. Changes in the HRV patterns provide a sensible and advanced indicator of health involvements. Higher HRV is a signal of good adaptation and characterizes a health person with efficient autonomic mechanisms, while lower HRV is frequently an indicator of abnormal and insufficient adaptation of the autonomic nervous system, provoking poor patient's physiological function. Because of its importance as a marker that reflects the ANS activity on the sinus node and as a clinical instrument to assess and identify health involvements, this study reviews conceptual aspects of the HRV, measurement devices, filtering methods, indexes used in the HRV analyses, limitations in the use and clinical applications of the HRV. PMID:19768301

Vanderlei, Luiz Carlos Marques; Pastre, Carlos Marcelo; Hoshi, Rosângela Akemi; Carvalho, Tatiana Dias de; Godoy, Moacir Fernandes de

2009-01-01

4

An ASAE Meeting PresentationPaper Number: 051119 Variable Rate Nitrogen Application on Row Crop  

E-print Network

2 An ASAE Meeting PresentationPaper Number: 051119 Variable Rate Nitrogen Application on Row Crop at the 2005 ASAE Annual International Meeting Sponsored by ASAE Tampa Convention Center Tampa, Florida 17 - 20 July 2005 Abstract. Nitrogen fertilizer was applied to field-grown spinach using variable rate

Jones, Carol

5

Integrating GIS and GPS into a spatially-variable-rate herbicide application system  

NASA Astrophysics Data System (ADS)

A spatially variable rate herbicide application system was developed and a site-specific evaluation of its field performance and accuracy was conducted. The system was capable of automatically changing on-the-go the application rate of active ingredients (AI) to meet the requirements of current sprayer field location. A 4.2 ha field was sampled on an 18.3 m grid for soil texture and percent organic matter (%OM). The soil texture ranged from sandy loam to clay, while the %OM ranged from 0.98 to 2.73 percent. For the preemergence herbicide selected, a herbicide management table was used to determine the appropriate AI application rate for each area of the field depending on spatial variation of field parameter data (soil texture and %OM). For the sampled field, the AI application rate ranged from 3510 mL/ha to 5260 mL/ha. A geographical information system (GIS) software was utilized to develop a georeferenced map (management map) of field application rates. A direct nozzle injection field sprayer was equipped with a real-time differentially corrected global positioning system (DGPS). A control program was developed to retrieve the desired application rate from the GIS map utilizing position data (latitude and longitude) supplied by the DGPS system. The retrieved application rate was sent, in a voltage format, to a 21X datalogger which was used to change on-the-go the AI flow rate to correspond with the desired application rate at a specific sprayer ground speed and field position. Results revealed that the DGPS system maintained, on the average, an accuracy of one meter. However, a distance error of location determination produced by the DGPS system reached 30.84 m with a correction message age of 98 seconds. For the four application rates used in the study, the highest average application rate error (average difference between desired and calculated application rates) and CV values were 2.0 percent and 0.07 percent, respectively for the analyzed samples. The maximum application rate error was 14 percent for 96 percent of the field data points (96 percent of the time). These results showed that the control system was accurate in producing the desired application rate. On the average, the greatest reaction time of the system was 2.2 seconds. The spatial analysis showed that most application rate errors occurred near transition zones. These analysis also revealed that the contour lines of the calculated application rate maps followed the same pattern and coincide with the management map contour lines. The developed spatially variable rate herbicide application system was found to accurately reproduce the application rate management map in a repeatable fashion.

Al-Gaadi, Khalid Ali

1998-12-01

6

DRPIT: Data-Rate PSNR Information Table Computation and Its Application for Variable Rate Video Streaming  

Microsoft Academic Search

This paper describes a novel approach to represent the rate-distortion characteristics of an encoded media. This work is distinguished by three key contributions. The first is the introduction of the concept of data-rate PSNR information table (DRPIT), which facilitates for very fast packet scheduling during video streaming. Rate-distortion characteristic of the compressed video is extracted during preprocessing and is stored

Harendra Narayan; Dilip Sarkar; James W. Modestino

2006-01-01

7

Variable-rate analysis: transient and pseudosteady-state methods of interpretation and application  

E-print Network

~-RATE AHALYSIS: TRANSZENT AHD PSEIEXSTEAVl-STATE MEZK!% CP XFHEPRFMMN AMD APPLICATION A~ ss to style and oontent by . J. Iee (Cbsinsnn of CcmsaLttee) W. L. (Member) R. A. Vst~ger (Member) R. R. Berg (Membm) . D. Ucn Gonten ( of Depart) Variable...; My committee cbairamn, Qr. V. J, Lee, whose influence has guided me always to seek excellent in my life aud in my work; My feU. ov graduate students, for their ~ aud respect; And. to GocL, for giving me the ability as a man to contribute a work...

Blasingame, Thomas Alwin

2012-06-07

8

Discriminating noise from chaos in heart rate variability : application to prognosis in heart failure  

E-print Network

This thesis examines two challenging problems in chaos analysis: distinguishing deterministic chaos and stochastic (noise-induced) chaos, and applying chaotic heart rate variability (HRV) analysis to the prognosis of ...

Arzeno, Natalia M. (Natalia María Arzeno Soltero)

2007-01-01

9

Real-time variable rate Pix® application system using a plant height sensor  

E-print Network

The objective of this study was to develop a chemical application system that could measure plant size, determine the optimum chemical rate to apply and control that application. A plant height sensor, the MEPRT growth relationship software...

Beck, Andy Dwayne

2012-06-07

10

The application of surface plethysmography for heart rate variability analysis after GSM radiofrequency exposure  

Microsoft Academic Search

The aim of the present study was to test whether the electromagnetic field emitted by standard GSM mobile phones results in changes in heart rate (HR) and heart rate variability (HRV) of 35 healthy young male and female subjects. Two parallel signals, electrocardiogram and infrared surface plethysmogram were recorded and compared to test their validity for the analysis. Plethysmographic recording

Tamás Atlasz; Lóránd Kellényi; Péter Kovács; Norbert Babai; György Thuróczy; László Hejjel; István Hernádi

2006-01-01

11

Functional assessment of heart rate variability: physiological basis and practical applications  

Microsoft Academic Search

The autonomic nervous system dynamically controls the response of the body to a range of external and internal stimuli, providing physiological stability in the individual. With the progress of information technology, it is now possible to explore the functioning of this system reliably and non-invasively using comprehensive and functional analysis of heart rate variability. This method is already an established

Jiri Pumprla; Kinga Howorka; David Groves; Michael Chester; James Nolan

2002-01-01

12

Recurrence Plot Based Measures of Complexity and its Application to Heart Rate Variability Data  

E-print Network

The knowledge of transitions between regular, laminar or chaotic behavior is essential to understand the underlying mechanisms behind complex systems. While several linear approaches are often insufficient to describe such processes, there are several nonlinear methods which however require rather long time observations. To overcome these difficulties, we propose measures of complexity based on vertical structures in recurrence plots and apply them to the logistic map as well as to heart rate variability data. For the logistic map these measures enable us not only to detect transitions between chaotic and periodic states, but also to identify laminar states, i.e. chaos-chaos transitions. The traditional recurrence quantification analysis fails to detect the latter transitions. Applying our new measures to the heart rate variability data, we are able to detect and quantify the laminar phases before a life-threatening cardiac arrhythmia occurs thereby facilitating a prediction of such an event. Our findings could be of importance for the therapy of malignant cardiac arrhythmias.

N. Marwan; N. Wessel; U. Meyerfeldt; A. Schirdewan; J. Kurths

2002-01-29

13

Influence of QRS complex detection errors on entropy algorithms. Application to heart rate variability discrimination.  

PubMed

Signal entropy measures such as approximate entropy (ApEn) and sample entropy (SampEn) are widely used in heart rate variability (HRV) analysis and biomedical research. In this article, we analyze the influence of QRS detection errors on HRV results based on signal entropy measures. Specifically, we study the influence that QRS detection errors have on the discrimination power of ApEn and SampEn using the cardiac arrhythmia suppression trial (CAST) database. The experiments assessed the discrimination capability of ApEn and SampEn under different levels of QRS detection errors. The results demonstrate that these measures are sensitive to the presence of ectopic peaks: from a successful classification rate of 100%, down to a 75% when spikes are present. The discriminating capability of the metrics degraded as the number of misdetections increased. For an error rate of 2% the segmentation failed in a 12.5% of the experiments, whereas for a 5% rate, it failed in a 25%. PMID:23246085

Molina-Picó, Antonio; Cuesta-Frau, David; Miró-Martínez, Pau; Oltra-Crespo, Sandra; Aboy, Mateo

2013-04-01

14

Determinants of heart rate variability  

Microsoft Academic Search

Objectives. This study sought to examine clinical determinants of heart rate variability and to report normative reference values for eight heart rate variability measures.Background. Although the clinical implications of heart rate variability have been described, clinical determinants and normative values of heart rate variability measures have not been studied systematically in a large community-based population.Methods. The first 2 h of

Hisako Tsuji; Ferdinand J. Venditti; Emily S. Manders; Jane C. Evans; Martin G. Larson; Charles L. Feldman; Daniel Levy

1996-01-01

15

On rating curve variability in presence of movable bed and unsteady flow. Applications to Tuscan rivers.  

NASA Astrophysics Data System (ADS)

In common engineering practice, rating curves are obtained from direct stage-discharge measurements or, more often, from stage measurements coupled with flow simulations. The present work mainly focuses on the latter technique, where stage-measuring gauges are usually installed on bridges with flow conditions likely to be influenced by local geometry constraints. In such cases, backwater flow and flow transition to supercritical state may occur, influencing sediment transport capacity and triggering more intense changes in river morphology. The unsteadiness of the flow hydrograph may play an important role too, according to the velocity of its rising and falling limbs. Nevertheless, the simulations conducted to build a rating curve are often carried out with steady flow and fixed bed conditions where the afore-mentioned effects are not taken into account at all. Numerical simulations with mobile bed and different unsteady flow conditions have been conducted on some real case studies in the rivers of Tuscany (Italy), in order to assess how rating curves change with respect to the "standard" one (that is, the classical steady flow rating curve). A 1D finite volume numerical model (REMo, River Evolution Modeler) has been employed for the simulations. The model solves the 1D Shallow Water equations coupled with the sediments continuity equation in composite channels, where the overbanks are treated with fixed bed conditions while the main channel can either aggrade or be scoured. The model employs an explicit scheme with 2nd order accuracy in both space and time: this allows the correct handling of moderately stiff source terms via a local corrector step. Such capability is very important for the applications of the present work as it allows the modelling of abrupt contractions and jumps in bed bottom elevations which often occur near bridges. The outcomes of the simulations are critically analyzed in order to provide a first insight on the conditions inducing significant changes between the two types of rating curves.

Minatti, Lorenzo; Nicoletta De Cicco, Pina; Paris, Enio

2014-05-01

16

Application of heart-rate variability in patients undergoing weaning from mechanical ventilation  

PubMed Central

Introduction The process of weaning may impose cardiopulmonary stress on ventilated patients. Heart-rate variability (HRV), a noninvasive tool to characterize autonomic function and cardiorespiratory interaction, may be a promising modality to assess patient capability during the weaning process. We aimed to evaluate the association between HRV change and weaning outcomes in critically ill patients. Methods This study included 101 consecutive patients recovering from acute respiratory failure. Frequency-domain analysis, including very low frequency, low frequency, high frequency, and total power of HRV was assessed during a 1-hour spontaneous breathing trial (SBT) through a T-piece and after extubation after successful SBT. Results Of 101 patients, 24 (24%) had SBT failure, and HRV analysis in these patients showed a significant decrease in total power (P = 0.003); 77 patients passed SBT and were extubated, but 13 (17%) of them required reintubation within 72 hours. In successfully extubated patients, very low frequency and total power from SBT to postextubation significantly increased (P = 0.003 and P = 0.004, respectively). Instead, patients with extubation failure were unable to increase HRV after extubation. Conclusions HRV responses differ between patients with different weaning outcomes. Measuring HRV change during the weaning process may help clinicians to predict weaning results and, in the end, to improve patient care and outcome. PMID:24456585

2014-01-01

17

Econometric Methods for Fractional Response Variables with an Application to 401(K) Plan Participation Rates  

Microsoft Academic Search

We develop attractive functional forms and simple quasi-likelihood estimation methods for regression models with a fractional dependent variable. Compared with log-odds type procedures, there is no difficulty in recovering the regression function for the fractional variable, and there is no need to use ad hoc transformations to handle data at the extreme values of zero and one. We also offer

Leslie E. Papke; Jeffrey M. Wooldridge

1996-01-01

18

A comparison of crop data measured by two commercial sensors for variable-rate nitrogen application  

Microsoft Academic Search

Nitrogen (N) fertilizer rates applied spatially according to crop requirements can improve the efficiency of N use. The study\\u000a compares the performance of two commercial sensors, the Yara N-Sensor\\/FieldScan (Yara International ASA, Germany) and the\\u000a GreenSeeker (NTech Industries Inc., Ukiah, California, USA), for assessing the status of N in spring wheat (Triticum aestivum L.) and corn (Zea mays L.). Four

Nicolas Tremblay; Zhijie Wang; Bao-Luo Ma; Carl Belec; Philippe Vigneault

2009-01-01

19

Analysis of Heart Rate Variability  

Microsoft Academic Search

Spontaneous variability of heart-rate has been related to three major physiological originating factors: quasi-oscillatory fluctuations thought to arise in blood-pressure control, variable frequency oscillations due to thermal regulation, and respiration; frequency selective analysis of cardiac interbeat interval sequences allows the separate contributions to be isolated. Using this method, a laboratory and field study of the effects of mental work load

B. Mc A. SAYKRS

1973-01-01

20

Heart rate variability: a review  

Microsoft Academic Search

Heart rate variability (HRV) is a reliable reflection of the many physiological factors modulating the normal rhythm of the\\u000a heart. In fact, they provide a powerful means of observing the interplay between the sympathetic and parasympathetic nervous\\u000a systems. It shows that the structure generating the signal is not only simply linear, but also involves nonlinear contributions.\\u000a Heart rate (HR) is

U. Rajendra Acharya; Paul K. Joseph; N. Kannathal; Choo Min Lim; Jasjit S. Suri

2006-01-01

21

Validity of the ithlete(TM) Smart Phone Application for Determining Ultra-Short-Term Heart Rate Variability  

PubMed Central

The purpose of this investigation was to cross-validate the ithlete™ heart rate variability smart phone application with an electrocardiograph for determining ultra-short-term root mean square of successive R-R intervals. The root mean square of successive R-R intervals was simultaneously determined via electrocardiograph and ithlete™ at rest in twenty five healthy participants. There were no significant differences between the electrocardiograph and ithlete™ derived root mean square of successive R-R interval values (p > 0.05) and the correlation was near perfect (r = 0.99, p < 0.001). In addition, the ithlete™ revealed a Standard Error of the Estimate of 1.47 and Bland Altman plot showed that the limits of agreement ranged from 2.57 below to 2.63 above the constant error of ?0.03. In conclusion, the ithlete™ appeared to provide a suitably accurate measure of root mean square of successive R-R intervals when compared to the electrocardiograph measures obtained in the laboratory within the current sample of healthy adult participants. The current study lays groundwork for future research determining the efficacy of ithlete™ for reflecting athletic training status over a chronic conditioning period. PMID:24511344

Flatt, Andrew A.; Esco, Michael R.

2013-01-01

22

Economics of Variable Rate Lime in Indiana  

Microsoft Academic Search

In Indiana, variable rate application (VRA) of lime is often considered a good place to start site-specific management (SSM). This is because soil pH is one of the most variable of manageable soil characteristics in the state, the availability of essential nutrients is closely related to soil pH, and because spreaders can be retrofitted relatively inexpensively to do VRA. The

R. Bongiovanni; J. Lowenberg-Deboer

2000-01-01

23

Design of complex-valued variable digital filters and its application to the realization of arbitrary sampling rate conversion for complex signals  

Microsoft Academic Search

This paper studies the design of complex-valued variable digital filters (CVDFs) and their applications to the efficient arbitrary sample rate conversion for complex signals in software radio receivers. The design of CVDFs using either the minimax or least squares criteria is formulated as a convex optimization problem and solved using the second order cone programming (SOCP) or semidefinite programming (SDP).

K. M. Tsui; S. C. Chan; K. W. Tse

2004-01-01

24

[Application of linear and nonlinear characteristics of heart rate variability in assessment of autonomic nervous system activity].  

PubMed

Calculation of linear parameters, such as time-domain and frequency-domain analysis of heart rate variability (HRV), is a conventional method for assessment of autonomic nervous system activity. Nonlinear phenomena are certainly involved in the genesis of HRV. In a seemingly random signal the Poincaré plot can easily demonstrate whether there is an underlying determinism in the signal. Linear and nonlinear analysis methods were applied in the computer words inputting experiments in this study for physiological measurement. This study therefore demonstrated that Poincaré plot was a simple but powerful graphical tool to describe the dynamics of a system. PMID:25039132

Shi, Ping; Yu, Hongliu

2014-04-01

25

Design of complex-valued variable FIR digital filters and its application to the realization of arbitrary sampling rate conversion for complex signals  

Microsoft Academic Search

This brief studies the design of complex-valued variable digital filters (CVDFs) and their applications to the efficient arbitrary sample rate conversion for complex signals. The design of CVDFs using either the minimax or least-squares criteria is formulated as a convex optimization problem and solved using the second-order cone programming (SOCP). In addition, linear and convex quadratic inequality constraints can be

K. M. Tsui; S. C. Chan; K. W. Tse

2005-01-01

26

Method and system for spatially variable rate application of agricultural chemicals based on remotely sensed vegetation data  

NASA Technical Reports Server (NTRS)

Remotely sensed spectral image data are used to develop a Vegetation Index file which represents spatial variations of actual crop vigor throughout a field that is under cultivation. The latter information is processed to place it in a format that can be used by farm personnel to correlate and calibrate it with actually observed crop conditions existing at control points within the field. Based on the results, farm personnel formulate a prescription request, which is forwarded via email or FTP to a central processing site, where the prescription is prepared. The latter is returned via email or FTP to on-side farm personnel, who can load it into a controller on a spray rig that directly applies inputs to the field at a spatially variable rate.

Hood, Kenneth Brown (Inventor); Seal, Michael R. (Inventor); Lewis, Mark David (Inventor); Johnson, James William (Inventor)

2007-01-01

27

Method and apparatus for spatially variable rate application of agricultural chemicals based on remotely sensed vegetation data  

NASA Technical Reports Server (NTRS)

Remotely sensed spectral image data are used to develop a Vegetation Index file which represents spatial variations of actual crop vigor throughout a field that is under cultivation. The latter information is processed to place it in a format that can be used by farm personnel to correlate and calibrate it with actually observed crop conditions existing at control points within the field. Based on the results, farm personnel formulate a prescription request, which is forwarded via email or FTP to a central processing site, where the prescription is prepared. The latter is returned via email or FTP to on-side farm personnel, who can load it into a controller on a spray rig that directly applies inputs to the field at a spatially variable rate.

Hood, Kenneth Brown (Inventor); Seal, Michael R. (Inventor); Lewis, Mark David (Inventor); Johnson, James William (Inventor)

2004-01-01

28

Application of alpha/theta neurofeedback and heart rate variability training to young contemporary dancers: state anxiety and creativity.  

PubMed

As one in a series on the impact of EEG-neurofeedback in the performing arts, we set out to replicate a previous dance study in which alpha/theta (A/T) neurofeedback and heart rate variability (HRV) biofeedback enhanced performance in competitive ballroom dancers compared with controls. First year contemporary dance conservatoire students were randomised to the same two psychophysiological interventions or a choreology instruction comparison group or a no-training control group. While there was demonstrable neurofeedback learning, there was no impact of the three interventions on dance performance as assessed by four experts. However, HRV training reduced anxiety and the reduction correlated with improved technique and artistry in performance; the anxiety scale items focussed on autonomic functions, especially cardiovascular activity. In line with the putative impact of hypnogogic training on creativity A/T training increased cognitive creativity with the test of unusual uses, but not insight problems. Methodological and theoretical implications are considered. PMID:23684733

Gruzelier, J H; Thompson, T; Redding, E; Brandt, R; Steffert, T

2014-07-01

29

An Analysis of Heart Rate Variability  

Microsoft Academic Search

Proceeding from a formal definition of heart rate variability, some mathematical and statistical techniques from sampling statistics and time series analysis for the analytical evaluation of heart rate variability for ergonomics purposes are presented and compared. The concept of sampling statistics gives a measure of heart rate variability, arrived at by combining two measures, which were chosen according to a

H. LUCZAK; W. LAURIG

1973-01-01

30

Heart Rate Variability in Athletes  

Microsoft Academic Search

athletes from training status, different types of exercise training, sex and ageing, presented from both cross-sectional and longitudinal studies. The predictability of HRV in over-training, athletic condition and athletic performance is also included. Finally, some recommendations concerning the application of HRV methods in athletes are made. The cardiovascular system is mostly controlled by autonomic regulation through the activity of sympathetic

Bert Seps; Frank Beckers

2003-01-01

31

Variable rate CELP speech coding using widely variable parameter updates  

E-print Network

Code-excited, linear prediction (CELP) has become an accepted method for low bit rate, high quality coding of digital speech. The success of fixed rate CELP schemes has led to increased interest in variable rate techniques to provide lower average...

Moodie, Myron L.

2012-06-07

32

Heart rate variability in systemic hypertension  

Microsoft Academic Search

Low heart rate (HR) variability is a risk factor for cardiac mortality in various patient populations, but it has not been well established whether patients with long-standing hypertension have abnormalities in the autonomic modulation of HR. Time and frequency domain measures of HR variability were compared in randomly selected, age-matched populations of 188 normotensive and 168 hypertensive males (mean age

Heikki V. Huikuri; Antti Ylitalo; Sirkku M. Pikkujämsä; Markku J. Ikäheimo; K. E. Juhani Airaksinen; Asko O. Rantala; Mauno Lilja; Y. Antero Kesäniemi

1996-01-01

33

Chaotic analysis of fetal heart rate variability  

Microsoft Academic Search

Fetal heart rate variability has long been considered an indicator of fetal health, with a decrease in variability associated with the progression of disease. The purpose of this study was to develop an index of fetal health by applying the nonlinear analytic techniques of chaotic systems to measurements of the beat-to-beat intervals of the fetal heart. This study was carried

D. Borserio; H. Villanueva; J. Falconer

1994-01-01

34

Rater variables associated with ITER ratings.  

PubMed

Advocates of holistic assessment consider the ITER a more authentic way to assess performance. But this assessment format is subjective and, therefore, susceptible to rater bias. Here our objective was to study the association between rater variables and ITER ratings. In this observational study our participants were clerks at the University of Calgary and preceptors who completed online ITERs between February 2008 and July 2009. Our outcome variable was global rating on the ITER (rated 1-5), and we used a generalized estimating equation model to identify variables associated with this rating. Students were rated "above expected level" or "outstanding" on 66.4 % of 1050 online ITERs completed during the study period. Two rater variables attenuated ITER ratings: the log transformed time taken to complete the ITER [? = -0.06, 95 % confidence interval (-0.10, -0.02), p = 0.002], and the number of ITERs that a preceptor completed over the time period of the study [? = -0.008 (-0.02, -0.001), p = 0.02]. In this study we found evidence of leniency bias that resulted in two thirds of students being rated above expected level of performance. This leniency bias appeared to be attenuated by delay in ITER completion, and was also blunted in preceptors who rated more students. As all biases threaten the internal validity of the assessment process, further research is needed to confirm these and other sources of rater bias in ITER ratings, and to explore ways of limiting their impact. PMID:22777161

Paget, Michael; Wu, Caren; McIlwrick, Joann; Woloschuk, Wayne; Wright, Bruce; McLaughlin, Kevin

2013-10-01

35

Heart Rate Variability Malvin Carl Teich  

E-print Network

Heart Rate Variability Malvin Carl Teich Boston University and Columbia University http point processes Fractal-rate point processes S. B. Lowen and M. C. Teich, Fractal-Based Point Processes, Grasmere, UK, 2005 #12;CONGESTIVE HEART FAILURE INABILITY OF HEART TO INCREASE CARDIAC OUTPUT IN PROPORTION

Teich, Malvin C.

36

7 CFR 1735.33 - Variable interest rate loans.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Variable interest rate loans. 1735.33 Section...Loans § 1735.33 Variable interest rate loans. After June 10...certain variable rate loans at interest rates less than 5 percent but not...

2010-01-01

37

Rater Variables Associated with ITER Ratings  

ERIC Educational Resources Information Center

Advocates of holistic assessment consider the ITER a more authentic way to assess performance. But this assessment format is subjective and, therefore, susceptible to rater bias. Here our objective was to study the association between rater variables and ITER ratings. In this observational study our participants were clerks at the University of…

Paget, Michael; Wu, Caren; McIlwrick, Joann; Woloschuk, Wayne; Wright, Bruce; McLaughlin, Kevin

2013-01-01

38

Circadian rhythm of heart rate and heart rate variability  

PubMed Central

BACKGROUND—Measurements of heart rate variability (HRV) are increasingly used as markers of cardiac autonomic activity.?AIM—To examine circadian variation in heart rate and HRV in children.?SUBJECTS—A total of 57 healthy infants and children, aged 2 months to 15 years, underwent ambulatory 24 hour Holter recording. Monitoring was also performed on five teenagers with diabetes mellitus and subclinical vagal neuropathy in order to identify the origin of the circadian variation in HRV.?METHODS—The following variables were determined hourly: mean RR interval, four time domain (SDNN, SDNNi, rMSSD, and pNN50) and four frequency domain indices (very low, low and high frequency indices, low to high frequency ratio). A chronobiological analysis was made by cosinor method for each variable.?RESULTS—A significant circadian variation in heart rate and HRV was present from late infancy or early childhood, characterised by a rise during sleep, except for the low to high frequency ratio that increased during daytime. The appearance of these circadian rhythms was associated with sleep maturation. Time of peak variability did not depend on age. Circadian variation was normal in patients with diabetes mellitus.?CONCLUSION—We have identified a circadian rhythm of heart rate and HRV in infants and children. Our data confirm a progressive maturation of the autonomic nervous system and support the hypothesis that the organisation of sleep, associated with sympathetic withdrawal, is responsible for these rhythms.?? PMID:10906034

Massin, M.; Maeyns, K.; Withofs, N.; Ravet, F.; Gerard, P.; HEALY, M

2000-01-01

39

Changes in heart rate variability during fainting  

NASA Astrophysics Data System (ADS)

Studies of heart rate variability in people who faint may yield insights into normal physiologic mechanisms which probably are dynamic. These insights might be gained because fainting appears to be due to a breakdown of these mechanisms. Tilt table testing reliably induces fainting in patients with a history of fainting and can be used to study these mechanisms. During tilt tests ending in fainting heart rate changes markedly, with a loss of high-frequency components on power spectral analysis and a progressive slowing of overall sinus node discharge. These changes appear to be due to changes in efferent vagal nerve traffic. Several possible mechanisms of these changes in heart rate variability are discussed.

Sheldon, Robert; Riff, Kenneth

1991-10-01

40

ORAL PRESENTATION ABSTRACT Design of an Arterial Blood Pressure, Heart Rate Variability and Breathing Rate Measuring  

E-print Network

ORAL PRESENTATION ABSTRACT Design of an Arterial Blood Pressure, Heart Rate Variability can be used to calculate the instantaneous heart rate and consequently the heart rate variability blood pressure, brachial artery, breathing rate, heart rate variability, photodiode

Haykin, Simon

41

Modeling heart rate variability by stochastic feedback  

NASA Technical Reports Server (NTRS)

We consider the question of how the cardiac rhythm spontaneously self-regulates and propose a new mechanism as a possible answer. We model the neuroautonomic regulation of the heart rate as a stochastic feedback system and find that the model successfully accounts for key characteristics of cardiac variability, including the 1/f power spectrum, the functional form and scaling of the distribution of variations of the interbeat intervals, and the correlations in the Fourier phases which indicate nonlinear dynamics.

Amaral, L. A.; Goldberger, A. L.; Stanley, H. E.

1999-01-01

42

Quantitative analysis of heart rate variability  

Microsoft Academic Search

In the modern industrialized countries every year several hundred thousands of people diedue to the sudden cardiac death. The individual risk for this sudden cardiac death cannot bedefined precisely by common available, non-invasive diagnostic tools like Holter-monitoring,highly amplified ECG and traditional linear analysis of heart rate variability (HRV). Therefore,we apply some rather unconventional methods of nonlinear dynamics to analyse the

J. Kurths; A. Voss; P. Saparin; A. Witt; H. J. Kleiner; N. Wessel

1995-01-01

43

Measurement of heart-rate variability: Part 1—Comparative study of heart-rate variability analysis methods  

Microsoft Academic Search

A definition of heart-rate variability (h.r.v.) is given. The use of h.r.v. measurement in both clinical applications and\\u000a the neural cardiovascular research is discussed. For the latter applications, four different signals describing h.r.v. are\\u000a reviewed. It is shown that these signals are based on modifications of one model, namely the integral pulse frequency modulator.\\u000a In Part 2, a hardware device

O. Rompelman; A. J. R. M. Coenen; R. I. Kitney

1977-01-01

44

Heart Rate Variability - A Historical Perspective  

PubMed Central

Heart rate variability (HRV), the beat-to-beat variation in either heart rate or the duration of the R–R interval – the heart period, has become a popular clinical and investigational tool. The temporal fluctuations in heart rate exhibit a marked synchrony with respiration (increasing during inspiration and decreasing during expiration – the so called respiratory sinus arrhythmia, RSA) and are widely believed to reflect changes in cardiac autonomic regulation. Although the exact contributions of the parasympathetic and the sympathetic divisions of the autonomic nervous system to this variability are controversial and remain the subject of active investigation and debate, a number of time and frequency domain techniques have been developed to provide insight into cardiac autonomic regulation in both health and disease. It is the purpose of this essay to provide an historical overview of the evolution in the concept of HRV. Briefly, pulse rate was first measured by ancient Greek physicians and scientists. However, it was not until the invention of the “Physician’s Pulse Watch” (a watch with a second hand that could be stopped) in 1707 that changes in pulse rate could be accurately assessed. The Rev. Stephen Hales (1733) was the first to note that pulse varied with respiration and in 1847 Carl Ludwig was the first to record RSA. With the measurement of the ECG (1895) and advent of digital signal processing techniques in the 1960s, investigation of HRV and its relationship to health and disease has exploded. This essay will conclude with a brief description of time domain, frequency domain, and non-linear dynamic analysis techniques (and their limitations) that are commonly used to measure HRV. PMID:22144961

Billman, George E.

2011-01-01

45

Interaction between heart rate and heart rate variability.  

PubMed

Heart rate variability (HRV) is significantly associated with average heart rate (HR), therefore, HRV actually provides information on two quantities, that is, on HR and its variability. It is difficult to conclude which of these two plays a principal role in the HRV clinical value, or in other words, what is the HR contribution to the clinical significance of HRV. Moreover, the association between HRV and HR is both a physiological phenomenon and a mathematical one. The physiological HRV dependence on HR is determined by the autonomic nervous system activity, but the mathematical one is caused by the nonlinear relationship between RR interval and HR. By employing modification methods of the HRV and HR relationship, it is possible to investigate the HR contribution to the HRV clinical value. Recent studies have shown that the removal of the HR impact on HRV makes HRV more predictive for noncardiac death, however, the enhancement of this impact causes HRV to be a better predictor of cardiovascular mortality. Thus, HR seems to constitute a cardiovascular factor of the HRV predictive ability. HR also influences the reproducibility of HRV, therefore, HR changes should be considered when one compares HRV measurements in a given patient. This review summarizes methodological aspects of investigations of the HRV and HR interaction as well as latest observations concerning its clinical utility. The issues discussed in this article should also refer to any other heart rate dynamics analysis which indices are significantly associated with HR. PMID:24602150

Sacha, Jerzy

2014-05-01

46

The Effects of Specific Respiratory Rates on Heart Rate and Heart Rate Variability  

Microsoft Academic Search

In this study respiratory rates of 3, 4, 6, 8, 10, 12, and 14 breaths per minute were employed to investigate the effects of these rates on heart rate variability (HRV). Data were collected 16 times at each respiratory rate on 3 female volunteers, and 12 times on 2 female volunteers. Although mean heart rates did not differ among these

Hye-Sue Song; Paul M. Lehrer

2003-01-01

47

Soil variability in engineering applications  

NASA Astrophysics Data System (ADS)

Natural geomaterials, as soils and rocks, show spatial variability and heterogeneity of physical and mechanical properties. They can be measured by in field and laboratory testing. The heterogeneity concerns different values of litho-technical parameters pertaining similar lithological units placed close to each other. On the contrary, the variability is inherent to the formation and evolution processes experienced by each geological units (homogeneous geomaterials on average) and captured as a spatial structure of fluctuation of physical property values about their mean trend, e.g. the unit weight, the hydraulic permeability, the friction angle, the cohesion, among others. The preceding spatial variations shall be managed by engineering models to accomplish reliable designing of structures and infrastructures. Materon (1962) introduced the Geostatistics as the most comprehensive tool to manage spatial correlation of parameter measures used in a wide range of earth science applications. In the field of the engineering geology, Vanmarcke (1977) developed the first pioneering attempts to describe and manage the inherent variability in geomaterials although Terzaghi (1943) already highlighted that spatial fluctuations of physical and mechanical parameters used in geotechnical designing cannot be neglected. A few years later, Mandelbrot (1983) and Turcotte (1986) interpreted the internal arrangement of geomaterial according to Fractal Theory. In the same years, Vanmarcke (1983) proposed the Random Field Theory providing mathematical tools to deal with inherent variability of each geological units or stratigraphic succession that can be resembled as one material. In this approach, measurement fluctuations of physical parameters are interpreted through the spatial variability structure consisting in the correlation function and the scale of fluctuation. Fenton and Griffiths (1992) combined random field simulation with the finite element method to produce the Random Finite Element Method (RFEM). This method has been used to investigate the random behavior of soils in the context of a variety of classical geotechnical problems. Afterward, some following studies collected the worldwide variability values of many technical parameters of soils (Phoon and Kulhawy 1999a) and their spatial correlation functions (Phoon and Kulhawy 1999b). In Italy, Cherubini et al. (2007) calculated the spatial variability structure of sandy and clayey soils from the standard cone penetration test readings. The large extent of the worldwide measured spatial variability of soils and rocks heavily affects the reliability of geotechnical designing as well as other uncertainties introduced by testing devices and engineering models. So far, several methods have been provided to deal with the preceding sources of uncertainties in engineering designing models (e.g. First Order Reliability Method, Second Order Reliability Method, Response Surface Method, High Dimensional Model Representation, etc.). Nowadays, the efforts in this field have been focusing on (1) measuring spatial variability of different rocks and soils and (2) developing numerical models that take into account the spatial variability as additional physical variable. References Cherubini C., Vessia G. and Pula W. 2007. Statistical soil characterization of Italian sites for reliability analyses. Proc. 2nd Int. Workshop. on Characterization and Engineering Properties of Natural Soils, 3-4: 2681-2706. Griffiths D.V. and Fenton G.A. 1993. Seepage beneath water retaining structures founded on spatially random soil, Géotechnique, 43(6): 577-587. Mandelbrot B.B. 1983. The Fractal Geometry of Nature. San Francisco: W H Freeman. Matheron G. 1962. Traité de Géostatistique appliquée. Tome 1, Editions Technip, Paris, 334 p. Phoon K.K. and Kulhawy F.H. 1999a. Characterization of geotechnical variability. Can Geotech J, 36(4): 612-624. Phoon K.K. and Kulhawy F.H. 1999b. Evaluation of geotechnical property variability. Can Geotech J, 36(4): 625-639. Terzaghi K. 1943. Theoretical Soil Mechanics. New York: J

Vessia, Giovanna

2014-05-01

48

Detection of asphyxia using heart rate variability.  

PubMed

The long-term aims of this study are to find a parameter derived from the ECG that has a high sensitivity and specificity to asphyxia and, once we know or suspect that asphyxia occurred, to estimate how severe it was. We carried out a pilot study in which 24 adult Wistar rats were anaesthetised and subjected to controlled asphyxia for specified durations. We measured the pH, 'neurological score' and the ECG, extracting from this heart rate and heart rate variability (HRV). We have developed a technique capable of detecting asphyxia in less than 1 min, based on monitoring the ECG and estimating HRV by measuring the standard deviation of normal RR intervals (the RR interval is the time interval between two consecutive R-points of the QRS complex). In all cases the heart rate decreased and HRV increased, by an average of 46 +/- 33 ms in relation to the baseline, at the onset of asphyxia. The comparison of the base level of HRV after and before asphyxia shows promise for the estimation of the severity of the episode; however, the limitations of this study should be noted as they include the small size of the cohort and the methods of analysis. PMID:12507311

Boardman, A; Schlindwein, F S; Thakor, N V; Kimura, T; Geocadin, R G

2002-11-01

49

Variability analysis in low count rate sources. [in astrophysics  

NASA Technical Reports Server (NTRS)

A method, based on the chi-square statistics, is described for detecting pulselike time variability in low count rate sources observed with photon-counting instruments. This method can be used even in the presence of observational gaps, takes full advantage of the filtering effect due to binning with different bin sizes, and takes into account the arbitrariness introduced by the binning phase. The procedure developed to limit the dependence of the results on the binning phase and ensure statistically correct results is described along with the application of the proposed procedure to a model of a variable source. Monte Carlo simulations are used to show how the method can be used to derive the characteristic variability time scales and that the method is more sensitive than the nonparametric Kolmogorov-Smirnov test in detecting variability to a given confidence level.

Collura, A.; Maggio, A.; Sciortino, S.; Serio, S.; Vaiana, G. S.

1987-01-01

50

Quantitative analysis of heart rate variability  

NASA Astrophysics Data System (ADS)

In the modern industrialized countries every year several hundred thousands of people die due to sudden cardiac death. The individual risk for this sudden cardiac death cannot be defined precisely by common available, noninvasive diagnostic tools like Holter monitoring, highly amplified ECG and traditional linear analysis of heart rate variability (HRV). Therefore, we apply some rather unconventional methods of nonlinear dynamics to analyze the HRV. Especially, some complexity measures that are based on symbolic dynamics as well as a new measure, the renormalized entropy, detect some abnormalities in the HRV of several patients who have been classified in the low risk group by traditional methods. A combination of these complexity measures with the parameters in the frequency domain seems to be a promising way to get a more precise definition of the individual risk. These findings have to be validated by a representative number of patients.

Kurths, J.; Voss, A.; Saparin, P.; Witt, A.; Kleiner, H. J.; Wessel, N.

1995-03-01

51

Heart Rate Variability, Part 1: Poststroke Patients  

E-print Network

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Acupuncture has been reported to affect the human autonomic system. Within this pilot study, teleacupuncture between China and Austria is used for the first time for quantifying the effects of heart rate variability (HRV) in poststroke rehabilitation. Methods. In 29 Chinese post-stroke patients (15 f, 14 m; mean age ± SD 64.7 ± 11.3 years; range 40–80 years) electrocardiographic signals before, during, and after acupuncture at the acupoint Tongli (HT 5) were recorded in Harbin and analyzed in Graz using teleacupuncture via internet. HRV data were analyzed in the time and frequency domain, and a protocol from Austria was sent to the team in China immediately after the treatment and recording session. Results. Acupuncture does not change heart rate in the post-stroke patients; however, total HRV increased significantly (P teleacupuncture between China/Harbin and Austria/Graz over a distance of about 8,500 km is no longer a future vision; it has become reality. 1.

Lu Wang; Jan Valentini; Kazuo Sugimoto; Weiping Cheng; Guangyu Cheng; Haoming Geng; Ingrid Gaischek; Haixue Kuang; Gerhard Litscher

52

DEVELOPMENT OF A SEMI-CONTROLLER FOR A VARIABLE RATE FERTILIZER  

E-print Network

DEVELOPMENT OF A SEMI-CONTROLLER FOR A VARIABLE RATE FERTILIZER APPLICATOR Jianbin Ji 1 , Xiu Wang production, introduced a variable fertilizer controller which suits for a domestic food-producing areas to promote output. The variable rate fertilization controller combined with the current Chinese made

53

The Impact of Soil Sampling Errors on Variable Rate Fertilization  

SciTech Connect

Variable rate fertilization of an agricultural field is done taking into account spatial variability in the soil’s characteristics. Most often, spatial variability in the soil’s fertility is the primary characteristic used to determine the differences in fertilizers applied from one point to the next. For several years the Idaho National Engineering and Environmental Laboratory (INEEL) has been developing a Decision Support System for Agriculture (DSS4Ag) to determine the economically optimum recipe of various fertilizers to apply at each site in a field, based on existing soil fertility at the site, predicted yield of the crop that would result (and a predicted harvest-time market price), and the current costs and compositions of the fertilizers to be applied. Typically, soil is sampled at selected points within a field, the soil samples are analyzed in a lab, and the lab-measured soil fertility of the point samples is used for spatial interpolation, in some statistical manner, to determine the soil fertility at all other points in the field. Then a decision tool determines the fertilizers to apply at each point. Our research was conducted to measure the impact on the variable rate fertilization recipe caused by variability in the measurement of the soil’s fertility at the sampling points. The variability could be laboratory analytical errors or errors from variation in the sample collection method. The results show that for many of the fertility parameters, laboratory measurement error variance exceeds the estimated variability of the fertility measure across grid locations. These errors resulted in DSS4Ag fertilizer recipe recommended application rates that differed by up to 138 pounds of urea per acre, with half the field differing by more than 57 pounds of urea per acre. For potash the difference in application rate was up to 895 pounds per acre and over half the field differed by more than 242 pounds of potash per acre. Urea and potash differences accounted for almost 87% of the cost difference. The sum of these differences could result in a $34 per acre cost difference for the fertilization. Because of these differences, better analysis or better sampling methods may need to be done, or more samples collected, to ensure that the soil measurements are truly representative of the field’s spatial variability.

R. L. Hoskinson; R C. Rope; L G. Blackwood; R D. Lee; R K. Fink

2004-07-01

54

HEART RATE VARIABILITY AS DETERMINISM WITH JUMP STOCHASTIC PARAMETERS  

E-print Network

HEART RATE VARIABILITY AS DETERMINISM WITH JUMP STOCHASTIC PARAMETERS JIONGXUAN ZHENG, JOE SKUFCA of the system. Key words. heart rate variability, electrocardiography, next angle map, circle map, jump process, consistent with our expectation that heart rate variability should vary continuously . We find the resultant

Bollt, Erik

55

RESEARCH PAPER Complexity of heart rate variability predicts  

E-print Network

RESEARCH PAPER Complexity of heart rate variability predicts outcome in intensive care unit- 2014-308389 ABSTRACT Background Heart rate variability (HRV) has been proposed as a predictor of acute the autonomic nervous system and induces cardiovascular responses.1�3 Heart rate variability (HRV) has been

Hung, Shih-Hao

56

gHRV: Heart rate variability analysis made easy.  

PubMed

In this paper, the gHRV software tool is presented. It is a simple, free and portable tool developed in python for analysing heart rate variability. It includes a graphical user interface and it can import files in multiple formats, analyse time intervals in the signal, test statistical significance and export the results. This paper also contains, as an example of use, a clinical analysis performed with the gHRV tool, namely to determine whether the heart rate variability indexes change across different stages of sleep. Results from tests completed by researchers who have tried gHRV are also explained: in general the application was positively valued and results reflect a high level of satisfaction. gHRV is in continuous development and new versions will include suggestions made by testers. PMID:24854108

Rodríguez-Liñares, L; Lado, M J; Vila, X A; Méndez, A J; Cuesta, P

2014-08-01

57

Comparison of different threshold values r for approximate entropy: application to investigate the heart rate variability between heart failure and healthy control groups.  

PubMed

Approximate entropy (ApEn) is widely accepted as a complexity measure of the heart rate variability (HRV) signal, but selecting the criteria for the threshold value r is controversial. This paper aims to verify whether Chon's method of forecasting the r(max) is an appropriate one for the HRV signal. The standard limb lead ECG signals of 120 subjects were recorded for 10 min in a supine position. The subjects were divided into two groups: the heart failure (22 females and 38 males, median age 62.4 ± 12.6) and healthy control group (33 females and 27 males, median age 51.5 ± 16.9). Three types of ApEn were calculated: the ApEn(0.2) using the recommended constant r = 0.2, the ApEn(chon) using Chon's method and the ApEn(max) using the true r(max). A Wilcoxon rank sum test showed that the ApEn(0.2) (p = 0.267) and the ApEn(max) (p = 0.813) had no statistical differences between the two groups, while the ApEn(chon) (p = 0.040) had. We generated a synthetic database to study the effect of two influential factors (the signal length N and the ratio of short- and long-term variability sd(1)/sd(2)) on the empirical formula in Chon's method (Chon et al 2009 IEEE Eng. Med. Biol. Mag. 28 18-23). The results showed that the empirical formula proposed by Chon et al is a good method for analyzing the random signal, but not an appropriate tool for analyzing nonlinear signals, such as the logistic or HRV signals. PMID:21178247

Liu, Chengyu; Liu, Changchun; Shao, Peng; Li, Liping; Sun, Xin; Wang, Xinpei; Liu, Feng

2011-02-01

58

Study of time reversibility/irreversibility of cardiovascular data: theoretical results and application to laser Doppler flowmetry and heart rate variability signals  

NASA Astrophysics Data System (ADS)

Time irreversibility can be qualitatively defined as the degree of a signal for temporal asymmetry. Recently, a time irreversibility characterization method based on entropies of positive and negative increments has been proposed for experimental signals and applied to heart rate variability (HRV) data (central cardiovascular system (CVS)). The results led to interesting information as a time asymmetry index was found different for young subjects and elderly people or heart disease patients. Nevertheless, similar analyses have not yet been conducted on laser Doppler flowmetry (LDF) signals (peripheral CVS). We first propose to further investigate the above-mentioned characterization method. Then, LDF signals, LDF signals reduced to samples acquired during ECG R peaks (LDF_RECG signals) and HRV recorded simultaneously in healthy subjects are processed. Entropies of positive and negative increments for LDF signals show a nonmonotonic pattern: oscillations—more or less pronounced, depending on subjects—are found with a period matching the one of cardiac activity. However, such oscillations are not found with LDF_RECG nor with HRV. Moreover, the asymmetry index for LDF is markedly different from the ones of LDF_RECG and HRV. The cardiac activity may therefore play a dominant role in the time irreversibility properties of LDF signals.

Humeau-Heurtier, Anne; Mahé, Guillaume; Chapeau-Blondeau, François; Rousseau, David; Abraham, Pierre

2012-07-01

59

[Application of 5-second heart rate variability parameter based on poincare plot in real-time monitoring of the autonomic nervous system activity].  

PubMed

This study designed one index of HRV from Poincaré plot named 5SSD1 by the present authors, which can describe the characteristics of the heart rate dynamics with 5-second data. We also investigated the feasibility of its clinical application in real-time monitoring of the activity of autonomic nervous system. We studied 20 patients scheduled for oral maxillofacial surgery. ECG recording was obtained when kept awake and anesthetic states, respectively. We calculated the correlation coefficients between the 5SSD1 and the other quantitative indicators, such as 5-minute HRV in the time domain, the frequency domain, and the Poincaré plot families. The correlation between 5SSD1 and indicators, such as rMSSD, HF and SD1 of 5-minute HRV was significantly high, with r=0.995, 0.895, 0.996, respectively, at P<0.01 for all. However, the correlation between 5SSD1 and the other indicators of 5-minute HRV was relatively poor. It was proved that 5SSD1 could be used to assess the activities of the autonomic nervous system in real-time, and the stable and reliable results might play more roles in the clinical applications. PMID:21774231

Jia, Xiaoning; Shen, Dai; Li, Chuanyong

2011-06-01

60

Heart rate variability. Frequency domain analysis.  

PubMed

Experience with frequency domain analysis over the past two decades strongly suggests that it represents a unique, noninvasive tool for achieving a more precise assessment of autonomic function in both the experimental and clinical settings. Available studies indicate that the significance of the HF component is far better understood than that of the lower frequency components. In general, it is considered to reflect vagal activity, and because it is readily manipulated pharmacologically, is used as a an index of that activity. However, some caution is required because this parameter also is strongly influenced by the degree of coupling between respiration and heart rate, which, in turn, reflects the intensity of the respiratory effort as well as of parasympathetic activity. Respiratory pattern also can significantly influence HF power. The use of controlled breathing minimizes these problems, improves reproducibility of test findings, and also facilitates quantitative comparisons. The situation with respect to LF power is more complicated because it is modulated by both sympathetic and parasympathetic outflows (see previous discussion) as well as by other factors, including baroreceptor activity. Therefore, LF analysis per se cannot afford a precise delineation of the state of sympathetic activation. Determinations of the LF/HF ratio, an index of sympathovagal balance both under control conditions and in conjunction with interventions that maximize sympathetic and parasympathetic activity, provide additional insights, as do correlations between spectral activity and direct nerve recordings, plasma norepinephrine concentrations, and radionuclide imaging of adrenergic nerves. Renewed interest has recently been evinced in frequencies lower than 0.04 Hz in view of reports that the VLF portion of the spectrum (0.01-0.04 Hz) reflects a purer form of sympathetic activity than does the LF band. Despite the potential applicability to clinical problems, only very little is known about the physiologic basis of the VLF and ULF bands. Further study is required. However, it is important to note that meaningful determinations of VLF and ULF power may be difficult because decreases in frequency to such low levels are associated with an increasing propensity to violate the rules governing power spectral determinations (see previous discussion and appendix), violations that diminish reliability despite the most sophisticated preprocessing. It is also noteworthy that the reliability of spectral power determinations diminishes with decreases in the power of the signal and of the signal-to-noise ratio.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1504981

Ori, Z; Monir, G; Weiss, J; Sayhouni, X; Singer, D H

1992-08-01

61

12 CFR 619.9340 - Variable interest rate.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Variable interest rate. 619.9340 Section 619.9340 Banks and...SYSTEM DEFINITIONS § 619.9340 Variable interest rate. An interest rate on the outstanding loan balances, which may be...

2010-01-01

62

Heart Rate Variability and Work-Load Measurement  

Microsoft Academic Search

Heart rate variability is a result of the superimposition of different sources of variation which are systemized. Three parameters are used to describe the phenomenon of heart rate variation. The range of variation of these parameters is discussed using examples from both laboratory and field investigations. Analyses demonstrate a correlation between heart rate and their variability. Discussion of of the

W. ROHMERT; W. LAURIG; U. PHILIPP; H. LUCZAK

1973-01-01

63

Variable exhumation rates and variable displacement rates: Documenting recent slowing of Himalayan shortening in western Bhutan  

NASA Astrophysics Data System (ADS)

We link exhumational variability in space and time to the evolving geometry of the Himalayan fold-thrust belt in western Bhutan. By combining new and published geochronologic and thermochronologic data we document the burial age, peak temperatures and complete cooling history from 20 Ma to the present over an across-strike distance of ?125 km. These integrated cooling curves highlight windows of fast exhumation that vary spatially and temporally. We propose that pulses of fast exhumation are a result of structures that facilitate the vertical motion of material, illustrated in sequentially-restored cross sections. Due to a range of permissible geometries at depth, we explore and evaluate the impact of geometry on kinematics and rates of deformation. The linked cooling history and cross sections provide estimates of both magnitude and timing of thrust sheet displacement and highlight temporal variability in potential shortening rates. Structural and chronologic data illustrate a general north to south progression of Himalayan deformation, with emplacement of the Main Central thrust (MCT), Paro thrust and Shumar thrust by 12 to no later than 9 Ma. Two different geometries and kinematic scenarios for the Lesser Himalayan duplex are proposed. A north to south propagating duplex system requires that the southern portion of that system, south of the MCT, deformed and cooled by 9 Ma, leaving only the southernmost thrust sheets, including the Main Boundary and Main Frontal thrusts, to deform between 9 and 0 Ma. This limited post 9 Ma shortening would necessitate a marked slowdown in convergence accommodated on the Main Himalayan thrust. A two-tiered duplex system, which allows for the Paro window duplex and the southern Baxa duplex to form simultaneously, permits duplex formation and accompanying exhumation until 6 Ma. Limited cooling from ?200 °C to the surface post 6 Ma suggests either a decrease in shortening rates from 6 to 0 Ma or that duplex formation and exhumation are temporally decoupled. Our combined cooling curves highlight that the youngest cooling ages may not mark the fastest thrusting rates or the window of fastest exhumation. Instead, temporal variations in exhumation are best viewed through identifying transients in exhumation rate. We suggest that the strongest control on exhumation magnitude and variability is fold-thrust belt geometry, particularly the locations and magnitudes of footwall ramps, which can change over 10's of km distance. Balanced cross sections predict the location and magnitude of these ramps and how they vary in space and time, providing an untapped potential for testing permissible cross-section geometries and kinematics against measured cooling histories.

McQuarrie, Nadine; Tobgay, Tobgay; Long, Sean P.; Reiners, Peter W.; Cosca, Michael A.

2014-01-01

64

Measurement of heart rate variability: a clinical tool or a research toy?  

Microsoft Academic Search

OBJECTIVESThe objectives of this review are to discuss the diversity of mechanisms that may explain the association between heart rate (HR) variability and mortality, to appraise the clinical applicability of traditional and new measures of HR variability and to propose future directions in this field of research. There is a large body of data demonstrating that abnormal HR variability measured

Heikki V Huikuri; Timo Mäkikallio; K. E. Juhani Airaksinen; Raul Mitrani; Agustin Castellanos; Robert J Myerburg

1999-01-01

65

Normal Ranges of Heart Rate Variability During Infancy and Childhood  

Microsoft Academic Search

.   Heart rate variability is a noninvasive index of the neural activity of the heart. The present study examined heart rate\\u000a variability indices in 210 infants and children aged 3 days to 14 years to obtain normal ranges for all age classes. Heart\\u000a rate variability was measured by calculating mean RR interval over the length of the analysis, mean RR

M. Massin; G. von Bernuth

1997-01-01

66

[Some regularities of the pulse rate variability].  

PubMed

Histograms of heat rate for 878 persons of both sexes aged from 3 to 83 years have been analyzed. The total data sampling was more than one hundred thousand pulse beats. Summary bar charts (variance pulsograms) were built up separately for men and women. Within the range of 60-75 beat/min, the peaks with the beat rates corresponding to 60, 61, 63, 65, 68, and 75 beat/min were observed, their values being twice as big as those of the neighbouring ones. Within the range of 79-99 beat/min, minima were observed with beat rates of 79, 87, 91, 94, 97, and 99 beat/min. The distribution of these beat rates can be approximately described by the members of Fibonacci series from the determining beat rate of about 59-60 beat/min (maximuma) and about 101/102 beat/min towards a decrease in the beat rate (minima). The determining beat rates of about 60, 101, and 162 beat/min may be evidence of the hierarchy, which is also approximately described by the array close to the Fibonacci series. Within the range of 101 to 115 beat/min, the peaks for men are marked that correspond to the harmonic series with a period of 2 beat/min, i.e., 101, 103, 115 beat/min. PMID:21950077

Dudin, S A; Zandanova, G I

2011-01-01

67

Heart rate variability in mice with coronary heart disease  

E-print Network

Heart rate variability (HRV), the beat-to-beat fluctuation of the heart rate, is a non-invasive test that measures the autonomic regulation of the heart. Assessment of HRV has been shown to predict the risk of mortality ...

Zapanta, Laurence (Laurence F.)

2005-01-01

68

Validation of pulse rate variability as a surrogate for heart rate variability in chronically instrumented rabbits.  

PubMed

Heart rate variability (HRV) is a function of cardiac autonomic tone that is widely used in both clinical and animal studies. In preclinical studies, HRV measures are frequently derived using the arterial pulse waveform from an implanted pressure telemetry device, termed pulse rate variability (PRV), instead of the electrocardiogram signal in accordance with clinical guidelines. The acceptability of PRV as a surrogate for HRV in instrumented animals is unknown. Using rabbits implanted with intracardiac leads and chronically implanted pressure transducers, we investigated the correlation and agreement of time-domain, frequency-domain, and nonlinear indexes of HRV and PRV at baseline. We also investigated the effects of ventricular pacing and autonomic blockade on both measures. At baseline, HRV and PRV time- and frequency-domain parameters showed robust correlations and moderate to high agreement, whereas nonlinear parameters showed slightly weaker correlations and varied agreement. Ventricular pacing almost completely eliminated HRV, and spectral analysis of the PRV signal revealed a HRV-independent rhythm. After cardiac autonomic blockade with atropine or metoprolol, the changes in time- and non-normalized frequency-domain measures of PRV continued to show strong correlations and moderate to high agreement with corresponding changes in HRV measures. Blockade-induced changes in nonlinear PRV indexes correlated poorly with HRV changes and showed weak agreement. These results suggest that time- and frequency-domain measures of PRV are acceptable surrogates for HRV even in the context of changing cardiac autonomic tone, but caution should be used when nonlinear measures are a primary end point or when HRV is very low as HRV-independent rhythms may predominate. PMID:24791786

Pellegrino, Peter R; Schiller, Alicia M; Zucker, Irving H

2014-07-01

69

MULTIRESOLUTION WAVELET ANALYSIS OF HEART RATE VARIABILITY FOR  

E-print Network

MULTIRESOLUTION WAVELET ANALYSIS OF HEART RATE VARIABILITY FOR HEART-FAILURE AND HEART- viation OW,V(m) is found to be superior to two commonly used heart-rate-variability me~ures for diagnosing a study on a collection of elec- - irocardiograms from patients who suffer from conges- tive heart failure

Teich, Malvin C.

70

Heart rate variability in infants, children and young adults  

Microsoft Academic Search

Heart rate variability was studied in normal subjects age 1 month-24 years while awake and in active and quiet sleep using 24 h continuous recordings of the ECG. Variability was quantified by spectral analysis for the two frequency bands: low frequency (LF) 0.03–0.15 Hz, high frequency (HF) 0.15–0.6 Hz. Heart rate variability showed an age dependence, being in general an

John P. Finley; Sherwin T. Nugent

1995-01-01

71

Variable frequency drive applications guide  

SciTech Connect

Traditionally, fans and pumps have been designed to be capable of handling the maximum demand of the system in which they are installed. However, quite often the actual demand can vary and it can be much lower than the original design capacity. These situations have been corrected in the past through additions of outlet dampers to fans or throttling valves to pumps. While these can be effective and simple controls they severely affect the efficiency of the system. Variable frequency (speed) is the most efficient means of capacity control. The most cost effective method of achieving variable speed capacity control is using AC adjustable frequency drives. AC adjustable frequency controls convert any fixed speed AC motor into an adjustable speed device. Adjusting the speed of a motor, by controlling the frequency of the AC power to that motor, reduces its horsepower requirements. According to pump and fan laws, capacity is proportional to speed while horsepower is proportional to the cube of the speed. Therefore, by reducing the speed of an AC motor by 20 percent the horsepower requirement is reduced by nearly 50 percent. Reduced speed through variable frequency control allows for flexibility of meeting changing weather and comfort requirements without operating costly equipment at full capacity.

Laloudakis, D.J.

1991-10-01

72

Variability in ESL Essay Rating Processes: The Role of the Rating Scale and Rater Experience  

ERIC Educational Resources Information Center

Various factors contribute to variability in English as a second language (ESL) essay scores and rating processes. Most previous research, however, has focused on score variability in relation to task, rater, and essay characteristics. A few studies have examined variability in essay rating processes. The current study used think-aloud protocols…

Barkaoui, Khaled

2010-01-01

73

Heart Rate Variability Analysis Using Threshold of Wavelet Package Coefficients  

E-print Network

In this paper, a new efficient feature extraction method based on the adaptive threshold of wavelet package coefficients is presented. This paper especially deals with the assessment of autonomic nervous system using the background variation of the signal Heart Rate Variability HRV extracted from the wavelet package coefficients. The application of a wavelet package transform allows us to obtain a time-frequency representation of the signal, which provides better insight in the frequency distribution of the signal with time. A 6 level decomposition of HRV was achieved with db4 as mother wavelet, and the above two bands LF and HF were combined in 12 specialized frequencies sub-bands obtained in wavelet package transform. Features extracted from these coefficients can efficiently represent the characteristics of the original signal. ANOVA statistical test is used for the evaluation of proposed algorithm.

Kheder, G; Massoued, M Ben; Samet, M

2009-01-01

74

Intertemporal extraction of mineral resources under variable-rate taxes  

SciTech Connect

This analysis shows that variability in tax rates, whether for output, value, or profits taxes, may create allocation incentives that are qualitatively different from those under fixed-rate taxation. The differences appear in the order in which the various grades are extracted, the rate at which they are extracted, and the total quantity extracted. 13 references.

Conrad, R.F.; Hool, R.B.

1984-11-01

75

Noncontact imaging photoplethysmography to effectively access pulse rate variability  

NASA Astrophysics Data System (ADS)

Noncontact imaging photoplethysmography (PPG) can provide physiological assessment at various anatomical locations with no discomfort to the patient. However, most previous imaging PPG (iPPG) systems have been limited by a low sample frequency, which restricts their use clinically, for instance, in the assessment of pulse rate variability (PRV). In the present study, plethysmographic signals are remotely captured via an iPPG system at a rate of 200 fps. The physiological parameters (i.e., heart and respiration rate and PRV) derived from the iPPG datasets yield statistically comparable results to those acquired using a contact PPG sensor, the gold standard. More importantly, we present evidence that the negative influence of initial low sample frequency could be compensated via interpolation to improve the time domain resolution. We thereby provide further strong support for the low-cost webcam-based iPPG technique and, importantly, open up a new avenue for effective noncontact assessment of multiple physiological parameters, with potential applications in the evaluation of cardiac autonomic activity and remote sensing of vital physiological signs.

Sun, Yu; Hu, Sijung; Azorin-Peris, Vicente; Kalawsky, Roy; Greenwald, Stephen

2013-06-01

76

Comparative analysis of variables to measure recovery rates in streams  

Microsoft Academic Search

The authors assessed a series of chemical and biological variables for their abilities and cost effectiveness in determining recovery rates in streams. Using data gathered at the experimental streams of the Monticello Ecological Research Station, several water-quality variables (DO, pH, nutrients), macroinvertebrate densities, macrophyte biomass, and periphyton biomass, and several ecosystem-level variable (e.g., primary production) were compiled and analyzed. Water-quality

Gerald J. Niemi; Naomi E. Detenbeck; James A. Perry

1993-01-01

77

Factors Accounting for Variability in Superintendent Ratings of Academic Preparation  

ERIC Educational Resources Information Center

This study utilized findings from the 2010 decennial study of the school superintendent to determine the extent to which four predictor variables ("courses," "professor credibility," "size" [enrollment of employing school district], and "gender") accounted for variability in superintendent overall ratings of their academic preparation. The…

Kowalski, Theodore J.; Young, I. Phillip; McCord, Robert S.

2011-01-01

78

High Bit Rate Continuous-Variable Quantum Key Distribution  

E-print Network

Here, we demonstrate that a practical Continuous Variables Quantum Key Distribution (CVQKD) protocol relying on the Gaussian modulation of coherent states features secret key rates that cannot be achieved with standard qubit Discrete Variables (DV) QKD protocols. Notably, we report for the first time a practical postprocessing that allows to extract more than one bit of secret key per channel use.

Paul Jouguet; David Elkouss; Sébastien Kunz-Jacques

2014-06-04

79

High-bit-rate continuous-variable quantum key distribution  

NASA Astrophysics Data System (ADS)

Here, we demonstrate that a practical continuous-variable quantum key distribution (QKD) protocol relying on the Gaussian modulation of coherent states features secret key rates that cannot be achieved with standard qubit discrete-variable QKD protocols. Notably, we report a practical postprocessing that allows us to extract more than 1 bit of secret key per channel use.

Jouguet, Paul; Elkouss, David; Kunz-Jacques, Sébastien

2014-10-01

80

Mental Load and the Measurement of Heart Rate Variability  

Microsoft Academic Search

A number of studies concerning heart rate variability and mental load arereviewedIt is concluded that in paced choice reaction tasks the number of reversal pointsin the cardiotachogram is the most sensitive measure of the load of the task.This measure was strongly correlated with respirationSpectral analysis of heart rate variability revealed the existence of a frequency component at about 0·10 Hz, a

G. MULDER

1973-01-01

81

Risks and rewards of variable-rate debt.  

PubMed

Hospital and health system finance leaders should position their organizations to participate in the variable-rate market. To this end, one important step is to establish the right baseline variable-rate exposure target for the organization based on its credit and risk profile. Leaders also should be thoroughly familiar with the available products and understand the circumstances (pricing, terms, and embedded risk) under which the organization would be willing to deploy them within the overall capital structure. PMID:22616511

Jordahl, Eric A

2012-05-01

82

Variable-rate coding for meteor-burst communications  

Microsoft Academic Search

The performance of variable-rate Reed-Solomon error-control coding for meteor-burst communications is considered. The code rate is allowed to vary from codeword to codeword within each packet, and the optimum number of codewords per packet and optimum rates for the codewords are determined as a function of the length of the message and the decay rate for the meteor trail. The

M. B. Pursley; S. D. Sandberg

1989-01-01

83

Sympathetic reinnervation and heart rate variability after cardiac transplantation.  

PubMed Central

BACKGROUND: Heart rate variability is thought to measure autonomic modulation, but the relation has never been demonstrated directly in humans. AIM: To test the hypothesis that increased low frequency heart rate variability reflects sympathetic reinnervation after cardiac transplantation. PATIENTS: 24 cardiac transplant recipients at the time of routine surveillance coronary angiography two or more years after cardiac transplantation, and 10 controls with normal coronary arteries undergoing angiography for investigation of chest pain. SETTING: Regional cardiothoracic centre. METHODS: Sympathetic effector function at the sinus node was assessed by measuring the fall in cycle length for two minutes after injection of tyramine to the artery supplying the sinus node. Heart rate variability was measured from three-minute RR interval sequences at rest, during metronomic respiration, and before and after atropine. RESULTS: The logarithm of the low frequency component of heart rate variability during metronomic respiration was linearly related to the logarithm of the change in cycle length after injection of tyramine (R2 = 0.28, P = 0.007). Absolute units more accurately reflected sympathetic effector function than did normalised units or the ratio of low frequency to high frequency. Atropine did not affect high frequency heart rate variability in transplant recipients. CONCLUSIONS: The low frequency component of heart rate variability is directly related to sympathetic reinnervation to the sinus node. PMID:9227297

Lord, S. W.; Clayton, R. H.; Mitchell, L.; Dark, J. H.; Murray, A.; McComb, J. M.

1997-01-01

84

Measuring Task-related Changes in Heart Rate Variability  

Microsoft Academic Search

Small beat-to-beat differences in heart rate are the result of dynamic control of the cardiovascular system by the sympathetic and parasympathetic nervous systems. Heart rate variability (HRV) has been positively correlated with both mental and physical health. While many studies measure HRV under rest conditions, few have measured HRV during stressful situations. We describe an experimental protocol designed to measure

Ziev B. Moses; Linda J. Luecken; James C. Eason

2007-01-01

85

Heart rate variability in depressive and anxiety disorders  

Microsoft Academic Search

Loss of normal autonomic nervous system control of heart rate and rhythm is an important risk factor for adverse cardiovascular events. After myocardial infarction, reduction in beat-to-beat heart rate variability, a measure of cardiac autonomic innervation by the brain, is a strong predictor of death. With loss of vagal innervation, as is noted in patients with severe neuropathy and in

Jack M. Gorman; Richard P. Sloan

2000-01-01

86

Heart rate variability associated with particulate air pollution  

Microsoft Academic Search

Background: Epidemiologic studies have linked fine particulate air pollution with cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown. Changes in heart rate variability (HRV) may reflect changes in cardiac autonomic function and risk of sudden cardiac death. This study evaluated changes in mean heart rate and HRV in human beings associated with changes in exposure to particulate air pollution. Methods:

C. Arden Pope; Richard L. Verrier; Eric G. Lovett; Andrew C. Larson; Mark E. Raizenne; Richard E. Kanner; Joel Schwartz; G. Martin Villegas; Diane R. Gold; Douglas W. Dockery

1999-01-01

87

Changes in resting heart rate variability across the menstrual cycle.  

PubMed

Heart rate variability (HRV) is a noninvasive indicator of autonomic control. This study examines HRV changes across a normal menstrual cycle and proposes a novel piecewise function controlling for the effects of breathing on HRV spectral parameters. A resting ECG was collected from 13 women at five points in their menstrual cycle. Both heart rate and breathing rate increased across the cycle (p?variability decreased (p?=?.04). Use of the piecewise function for breathing rate in HRV spectral analysis was confirmed by a substantial increase in model goodness-of-fit. HRV spectral parameters, controlled for breathing with the piecewise function, confirm that the decrease in variability is likely due to a parasympathetic withdrawal, since high frequency HRV decreases (p?=?.02). PMID:24942292

Tenan, Matthew S; Brothers, R Matthew; Tweedell, Andrew J; Hackney, Anthony C; Griffin, Lisa

2014-10-01

88

Heart rate variability and severe brain damage: preliminary data  

Microsoft Academic Search

Severe brain damage may cause alterations of cardiovascular function: heart rate, particularly, require the integrity of the\\u000a vagal, sympathetic and central nervous systems. We studied brain-heart functional relation and neurovegetative modulation\\u000a by spectral analysis of heart rate variability (HRV). This technique allows separate evaluation of the sympathetic and vagal\\u000a components of heart rate modulation.\\u000a \\u000a In order to correlate changes in

Luigi G. Lacquaniti; Marco Irone; Stefano Barbacini; Fulgido Merlo; Paolo Demo; Carlo Pellegrin; Maurizio Dan

1993-01-01

89

Heart rate variability (HRV): an indicator of stress  

NASA Astrophysics Data System (ADS)

Heart rate variability (HRV) can be an important indicator of several conditions that affect the autonomic nervous system, including traumatic brain injury, post-traumatic stress disorder and peripheral neuropathy [3], [4], [10] & [11]. Recent work has shown that some of the HRV features can potentially be used for distinguishing a subject's normal mental state from a stressed one [4], [13] & [14]. In all of these past works, although processing is done in both frequency and time domains, few classification algorithms have been explored for classifying normal from stressed RRintervals. In this paper we used 30 s intervals from the Electrocardiogram (ECG) time series collected during normal and stressed conditions, produced by means of a modified version of the Trier social stress test, to compute HRV-driven features and subsequently applied a set of classification algorithms to distinguish stressed from normal conditions. To classify RR-intervals, we explored classification algorithms that are commonly used for medical applications, namely 1) logistic regression (LR) [16] and 2) linear discriminant analysis (LDA) [6]. Classification performance for various levels of stress over the entire test was quantified using precision, accuracy, sensitivity and specificity measures. Results from both classifiers were then compared to find an optimal classifier and HRV features for stress detection. This work, performed under an IRB-approved protocol, not only provides a method for developing models and classifiers based on human data, but also provides a foundation for a stress indicator tool based on HRV. Further, these classification tools will not only benefit many civilian applications for detecting stress, but also security and military applications for screening such as: border patrol, stress detection for deception [3],[17], and wounded-warrior triage [12].

Kaur, Balvinder; Durek, Joseph J.; O'Kane, Barbara L.; Tran, Nhien; Moses, Sophia; Luthra, Megha; Ikonomidou, Vasiliki N.

2014-05-01

90

Relationship of Heart Rate Variability to Parasympathetic Effect  

Microsoft Academic Search

Background—Baroreflex-mediated parasympathetic stimulation has variable effects on heart rate variability (HRV). We postulated that a quadratic function would describe the relationship between HRV and parasympathetic effect better than a linear function. Methods and Results—Twenty-nine normal volunteers (15 women; mean age 39 612 years) were studied after b-adrenergic blockade with intravenous propranolol. Five-minute ECG recordings were made during graded infusions of

Jeffrey J. Goldberger; Sridevi Challapalli; Roderick Tung; Michele A. Parker; Alan H. Kadish

2010-01-01

91

LF\\/(LF+HF) index in Ventricular Repolarization Variability correlated and uncorrelated with Heart Rate Variability  

Microsoft Academic Search

The purpose of this study, was to asses whether LF\\/(LF+HF) obtained from ventricular repolarization variability (VRV) reflects the state of sympathovagal balance. The VRV time series and heart rate variability (HRV) time series from seventy two electrocardiogram (ECG) records in four different autonomic nervous system (ANS) profiles (athletes, cardiac transplant patient, heart failure patients and normal subjects) were extracted. A

M. Altuve; S. Wong; G. Passariello; G. Carrault; A. Hernandez

2006-01-01

92

Heart rate variability interventions for concussion and rehabilitation  

PubMed Central

The study of heart rate variability (HRV) has emerged as an essential component of cardiovascular health, as well as a physiological mechanism by which one can increase the interactive communication between the cardiac and the neurocognitive systems (i.e., the body and the brain). It is well-established that lack of HRV implies cardiopathology, morbidity, reduced quality-of-life, and precipitous mortality. On the positive, optimal HRV has been associated with good cardiovascular health, autonomic nervous system (ANS) control, emotional regulation, and enhanced neurocognitive processing. In addition to health benefits, optimal HRV has been shown to improve neurocognitive performance by enhancing focus, visual acuity and readiness, and by promoting emotional regulation needed for peak performance. In concussed athletes and soldiers, concussions not only alter brain connectivity, but also alter cardiac functioning and impair cardiovascular performance upon exertion. Altered sympathetic and parasympathetic balance in the ANS has been postulated as a critical factor in refractory post concussive syndrome (PCS). This article will review both the pathological aspects of reduced HRV on athletic performance, as well as the cardiovascular and cerebrovascular components of concussion and PCS. Additionally, this article will review interventions with HRV biofeedback (HRV BFB) training as a promising and underutilized treatment for sports and military-related concussion. Finally, this article will review research and promising case studies pertaining to use of HRV BFB for enhancement of cognition and performance, with applicability to concussion rehabilitation. PMID:25165461

Conder, Robert L.; Conder, Alanna A.

2014-01-01

93

Two-Stage Variable Sample-Rate Conversion System  

NASA Technical Reports Server (NTRS)

A two-stage variable sample-rate conversion (SRC) system has been pro posed as part of a digital signal-processing system in a digital com munication radio receiver that utilizes a variety of data rates. The proposed system would be used as an interface between (1) an analog- todigital converter used in the front end of the receiver to sample an intermediatefrequency signal at a fixed input rate and (2) digita lly implemented tracking loops in subsequent stages that operate at v arious sample rates that are generally lower than the input sample r ate. This Two-Stage System would be capable of converting from an input sample rate to a desired lower output sample rate that could be var iable and not necessarily a rational fraction of the input rate.

Tkacenko, Andre

2009-01-01

94

Extension of colgate's passivity condition for variable-rate haptics  

Microsoft Academic Search

Colgate's passivity conditions for the virtual coupling and the virtual wall have been one of the most important results in haptics. However, due to its development being rooted in the frequency-domain, its theoretical justification has been limited to only uniform-rate haptics. In this paper, relying on analysis\\/derivation in the time-domain, we extend this Colgate's passivity condition to variable-rate haptics. We

Dongjun Lee

2009-01-01

95

Age and Heart Rate Variability After Soccer Games  

Microsoft Academic Search

To observe the effect of age on the changes in heart rate variability (HRV) of adult amateur athletes after playing a soccer game, 20 male were divided into two groups: middle-aged (n = 10, 35–55 years) and aged (n = 10, 56–75 years). Before and after 2-hour soccer games, HRV and blood pressure were recorded. In both groups heart rate

Shuchun Yu; Takasumi Katoh; Hiroshi Makino; Soichiro Mimuno; Shigehito Sato

2010-01-01

96

Heart Rate and Blood Pressure Variability: Implications for Psychiatric Research  

Microsoft Academic Search

Symptoms of anxiety suggest autonomic dysfunction and most of the psycho-tropic agents used to treat anxiety and affective disorders have strong autonomic effects. This article describes the utility and importance of analysis of heart rate and blood pressure time series to study cardiac autonomic function in psychiatric research. The variability of heart rate between 0.15 and 0.5 Hz is related

Vikram K. Yeragani

1995-01-01

97

Variability of Lekanesphaera monodi metabolic rates with habitat trophic status  

NASA Astrophysics Data System (ADS)

Regulation of metabolism is a common strategy used by individuals to respond to a changing environment. The mechanisms underlying the variability of metabolic rates in macroinvertebrates are of primary importance in studying benthic-pelagic energy transfer in transitional water ecosystems. Lekanesphaera monodi is an isopod endemic to transitional water ecosystems that can modify its metabolic rate in response to environmental changes. Therefore it is a useful model in studying the influence of environmental factors on metabolism. This study focused on the interpopulation variability of standard metabolic rates (SMR) in L. monodi populations sampled in three transitional water ecosystems differing in their trophic status. The standard metabolic rates of L. monodi individuals across the same range of body size spectra were inferred from oxygen consumption measurements in a flow-through respirometer in the three populations and a body condition index was assessed for each population. Habitat trophic status was evaluated by monthly measurement of the basic physical-chemical parameters of the water column in the ecosystems for one year. Standard metabolic rates showed high variability, ranging from 0.27 to 10.14 J d-1. Body size accounted for more than 38% of total variability. In terms of trophic status, individuals from the eutrophic ecosystem had significantly higher standard metabolic rates than individuals from the other ecosystems (SMR = 2.3 J d-1 in Spunderati Sud vs. 1.36 J d-1 in Alimini and 0.69 J d-1 in Acquatina). The body conditions index was also higher in the population from the eutrophic ecosystem. Results show that standard metabolic rates and growth rates are directly related to habitat productivity in accordance with the expectations of the food habits hypothesis. A possible extension of this hypothesis to benthic invertebrates is proposed.

Vignes, Fabio; Fedele, Marialaura; Pinna, Maurizio; Mancinelli, Giorgio; Basset, Alberto

2012-05-01

98

Variable-speech-rate audiometry for hearing aid evaluation  

Microsoft Academic Search

A new hearing aid evaluation method using variable-speech-rate audiometry (VSRA) was developed. VSRA was newly created based on the Japanese speech audiometry authorized by the Japan Audiological Society. The ordinary speech audiometry can not reveal a temporal factor in word discrimination ability of the hearing impaired. Since, with VSRA, we can compare several performance-intensity curves obtained from different speech-rate speech

Hiroshi Hosoi; Yoshiaki Tsuta; Takashi Nishida; Kiyotaka Murata; Fumihiko Ohta; Tsuyoshi Mekata; Yumiko Kato

1999-01-01

99

Heart rate variability study of childhood anxiety disorders  

PubMed Central

Background: The current study aims at assessment of heart rate variability among children and adolescents with childhood anxiety disorder, using the case-control design. Materials and Methods: The study was carried out at a tertiary care multispecialty hospital. It included 34 children and adolescents with diagnosis of childhood anxiety disorder, in the age range of eight to eighteen years, and 30 age- and sex-matched healthy controls. Heart-rate variability was studied using the standard protocol. Results: Significantly reduced variability of the heart rate was observed in both the time as well as frequency domains in the disorder group as compared to the control group. These findings indicate decreases in the sympathetic and parasympathetic activity in the disorder group, thus representing diminished physiological variability at rest. Conclusions: The notion of autonomic inflexibility, as seen in the current study, has important implications for stability in biological systems. The loss of variability in the physiological systems in general, and in the cardiovascular system in particular, has an association with a number of diseases and dysfunctions. PMID:21814416

Sharma, Rajiv Kumar; Balhara, Yatan Pal Singh; Sagar, Rajesh; Deepak, K. K.; Mehta, Manju

2011-01-01

100

Heart Rate Variability and Drawing Impairment in Hypoxemic COPD  

ERIC Educational Resources Information Center

We studied 54 patients with hypoxemic chronic obstructive pulmonary disease (COPD). The Mini Mental State Examination and the Mental Deterioration Battery were used for neuropsychological assessment. Heart rate variability (HRV) was assessed based on 24-h Holter ECG recording. Mann-Whitney test was used to compare HRV parameters of patients…

Incalzi, Raffaele Antonelli; Corsonello, Andrea; Trojano, Luigi; Pedone, Claudio; Acanfora, Domenico; Spada, Aldo; D'Addio, Gianni; Maestri, Roberto; Rengo, Franco; Rengo, Giuseppe

2009-01-01

101

Disk Scheduling for Variable-Rate Data Streams  

Microsoft Academic Search

We describe three disk scheduling algorithms that can be used in a multimedia server for sustaining a number of heterogeneous variable-rate data streams. A data stream is supported by repeatedly fetching a block of data from the storage device and storing it in a corresponding buffer. For each of the disk scheduling algorithms we give necessary and sufficient conditions for

Jan H. M. Korst; Verus Pronk; Pascal Coumans

1997-01-01

102

Epileptic Seizure Behaviour from the Perspective of Heart Rate Variability  

Microsoft Academic Search

Heart Rate Variability (HRV) analysis has gained much importance in recent years, as a technique to explore the activity of autonomic nervous system (ANS), and an important early marker for identifying different pathological conditions. Epilepsy is a disease which progressively involves cardiac autonomic activity. Our studies indicate that time domain, frequency domain and some nonlinear measures of HRV would be

Soroor Behbahani; Nader Jafarnia Dabanloo; Ali Motie Nasrabadi; Gholamreza Attarodi; Cesar A Teixeira; Antonio Dourado

2012-01-01

103

Depression, Heart Rate Variability, and Acute Myocardial Infarction  

Microsoft Academic Search

Background—Clinical depression is associated with an increased risk for mortality in patients with a recent myocardial infarction (MI). Reduced heart rate variability (HRV) has been suggested as a possible explanation for this association. The purpose of this study was to determine if depression is associated with reduced HRV in patients with a recent MI. Methods and Results—Three hundred eighty acute

Robert M. Carney; James A. Blumenthal; Phyllis K. Stein; Lana Watkins; Diane Catellier; Lisa F. Berkman; Susan M. Czajkowski; Christopher O'Connor; Peter H. Stone; Kenneth E. Freedland

104

Autonomic balance revisited: Panic anxiety and heart rate variability  

Microsoft Academic Search

The analysis of heart rate variability (HRV) is becoming widely used in clinical research to provide a window into autonomic control of HR. This technique has been valuable in elucidating the autonomic underpinnings of panic disorder (PD), a condition that is marked by reports of heart palpitations. A body of research has emerged that implicates a relative reduction in HRV

Bruce H. Friedman; JULIAN F. THAYERt

1998-01-01

105

Robust estimation of fetal heart rate variability using Doppler ultrasound  

Microsoft Academic Search

This paper presents a new measure of heart rate variability (HRV) that can be estimated using Doppler ultrasound techniques and is robust to variations in the angle of incidence of the ultrasound beam and the measurement noise. This measure employs the multiple signal characterization (MUSIC) algorithm which is a high-resolution method for estimating the frequencies of sinusoidal signals embedded in

Kumari L. Fernando; V. John Mathews; Michael W. Varner; Edward B. Clark

2003-01-01

106

Robust estimation of fetal heart rate variability using Doppler ultrasound  

Microsoft Academic Search

Heart rate variability (HRV) provides important information about the development of the cardiovascular system in fetuses. The paper presents a new measure of fetal HRV that can be estimated using Doppler ultrasound techniques. This measure employs the multiple signal characterization (MUSIC) algorithm which is a high-resolution method for estimating the frequencies of sinusoidal signals embedded in white noise from short-duration

K. L. Fernando; V. J. Mathews; M. W. Varner; E. B. Clark

2003-01-01

107

Heart Rate Variability: Effect of Exercise Intensity on Postexercise Response  

ERIC Educational Resources Information Center

The purpose of the present study was to investigate the influence of two exercise intensities (moderate and severe) on heart rate variability (HRV) response in 16 runners 1 hr prior to (-1 hr) and at +1 hr, +24 hr, +48 hr, and +72 hr following each exercise session. Time domain indexes and a high frequency component showed a significant decrease…

James, David V. B.; Munson, Steven C.; Maldonado-Martin, Sara; De Ste Croix, Mark B. A.

2012-01-01

108

Heart Rate Variability as an Index of Regulated Emotional Responding  

Microsoft Academic Search

The study of individual differences in emotional responding can provide considerable insight into interpersonal dynamics and the etiology of psychopathology. Heart rate variability (HRV) analysis is emerging as an objective measure of regulated emotional responding (generating emotional responses of appropriate timing and magnitude). This review provides a theoretical and empirical rationale for the use of HRV as an index of

Bradley M. Appelhans; Linda J. Luecken

2006-01-01

109

Ultraviolet variability of quasars: dependence on the accretion rate  

NASA Astrophysics Data System (ADS)

Aims: Although the variability in the ultraviolet and optical domain is one of the major characteristics of quasars, the dominant underlying mechanisms are still poorly understood. There is a broad consensus on the relationship between the strength of the variability and such quantities as time-lag, wavelength, luminosity, and redshift. However, evidence on a dependence on the fundamental parameters of the accretion process is still inconclusive. This paper is focused on the correlation between the ultraviolet quasar long-term variability and the accretion rate. Methods: We compiled a catalogue of about 4000 quasars including individual estimators for the variability strength derived from the multi-epoch photometry in the SDSS Stripe 82, virial black hole masses M derived from the Mg ii line, and mass accretion rates ? from the Davis-Laor scaling relation. Several statistical tests were applied to evaluate the correlations of the variability with luminosity, mass, Eddington ratio, and accretion rate. Results: We confirm the existence of significant anti-correlations between the variability estimator V and the accretion rate ?, the Eddington ratio ?, and the bolometric luminosity Lbol, respectively. The Eddington ratio is tightly correlated with ?. A weak, statistically not significant positive trend is indicated for the dependence of V on M. As a side product, we find a strong correlation of the radiative efficiency ? with M in our sample. We show via numerical simulations that this trend is most likely produced by selection effects in combination with the mass errors and the use of the scaling relation for ?. The anti-correlations of V with ?, ?, and Lbol cannot be explained in such a way. The strongest anti-correlation is found between V and ?. However, it is difficult to decide which of the quantities L,?, and ? is intrinsically correlated with V and which of the observed correlations of V are produced by the L - ? - ? relation. A V - ? anti-correlation is qualitatively expected for the strongly inhomogeneous accretion disks. We argue that the observed amplitudes of the variability at far-UV wavelengths, the stochastic nature of variability, and the variability time-scales are not adequately explained by the simple multi-temperature black-body model of a standard disk and suggest to check whether the strongly inhomogeneous disk model is capable of reproducing these observations better. The catalogue of quasars is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/560/A104

Meusinger, H.; Weiss, V.

2013-12-01

110

Complexity of the short-term heart-rate variability.  

PubMed

This work has proposed a methodology based on the concept of entropy rates to study the complexity of the short-term heart-rate variability (HRV) for improving risk stratification to predict sudden cardiac death (SCD) of patients with established ischemic-dilated cardiomyopathy (IDC). The short-term HRV was analyzed during daytime and nighttime by means of RR series. An entropy rate was calculated on the RR series, previously transformed to symbol sequences by means of an alphabet. A statistical analysis permitted to stratify high- and low-risk patients of suffering SCD, with a specificity (SP) of 95% and sensitivity (SE) of 83.3%. PMID:19914891

Valencia, Jose F; Vallverdú, Montserrat; Schroeder, Rico; Voss, Andreas; Vázquez, Rafael; Bayés de Luna, Antonio; Caminal, Pere

2009-01-01

111

Bouts of responding: the relation between bout rate and the rate of variable-interval reinforcement.  

PubMed Central

By nose poking a lighted key, rats obtained food pellets on either a variable-interval schedule of reinforcement or a schedule that required an average of four additional responses after the end of tile variable-interval component (a tandem variable-interval variable-ratio 4 schedule). With both schedule types, the mean variable interval was varied between blocks of sessions from 16 min to 0.25 min. Total rate of key poking increased similarly as a function of the reinforcer rate for the two schedule types, but response rate was higher with than without the four-response requirement. Analysis of log survivor plots of interresponse times showed that key poking occurred in bouts. The rate of initiating bouts increased as a function of reinforcer rate but was either unaffected or was decreased by adding the four-response requirement. Within-bout response rate was insensitive to reinforcer rate and only inconsistently affected by the four-response requirement. For both kinds of schedule, the ratio of bout time to between-bout pause time was approximately a power function of reinforcer rate, with exponents above and below 1.0. PMID:15113134

Shull, Richard L; Grimes, Julie A; Bennett, J Adam

2004-01-01

112

Efficient delivery techniques for variable-bit-rate multimedia  

NASA Astrophysics Data System (ADS)

Two key technologies enabling scalable on-demand delivery of stored multimedia content are work-ahead smoothing and multicast delivery. Work-ahead smoothing reduces the burstiness of variable bit rate streams, simplifying server and network resource allocation. Recent multicast delivery techniques such as patching or bandwidth skimming serve clients that request the same content close together in time with (partially) shared multicasts, greatly reducing required server bandwidth. Although previous studies of work-ahead smoothing have generally assumed very limited client buffer space, in a number of contexts of current interest (such as systems that have significant settop storage), it becomes feasible to fully smooth variable bit rate content. We quantify the start-up delay and settop storage requirements of full smoothing for a number of sample variable bit rate objects. We then evaluate a fundamental conflict between aggressive smoothing and the new multicast delivery techniques. Work-ahead smoothing requires sending data for high rate portions of an object earlier than it is needed for playback, while multicast techniques yield their greatest benefit when data is delivered within each stream as late as possible so that more clients can share reception of that data. A new multicast delivery technique is proposed that can accommodate aggressive smoothing with increased efficiency in comparison to previous techniques, particularly for high request rates.

Zhao, Yanping; Eager, Derek L.; Vernon, Mary K.

2001-12-01

113

Heart rate variability in normal and pathological sleep  

PubMed Central

Sleep is a physiological process involving different biological systems, from molecular to organ level; its integrity is essential for maintaining health and homeostasis in human beings. Although in the past sleep has been considered a state of quiet, experimental and clinical evidences suggest a noteworthy activation of different biological systems during sleep. A key role is played by the autonomic nervous system (ANS), whose modulation regulates cardiovascular functions during sleep onset and different sleep stages. Therefore, an interest on the evaluation of autonomic cardiovascular control in health and disease is growing by means of linear and non-linear heart rate variability (HRV) analyses. The application of classical tools for ANS analysis, such as HRV during physiological sleep, showed that the rapid eye movement (REM) stage is characterized by a likely sympathetic predominance associated with a vagal withdrawal, while the opposite trend is observed during non-REM sleep. More recently, the use of non-linear tools, such as entropy-derived indices, have provided new insight on the cardiac autonomic regulation, revealing for instance changes in the cardiovascular complexity during REM sleep, supporting the hypothesis of a reduced capability of the cardiovascular system to deal with stress challenges. Interestingly, different HRV tools have been applied to characterize autonomic cardiac control in different pathological conditions, from neurological sleep disorders to sleep disordered breathing (SDB). In summary, linear and non-linear analysis of HRV are reliable approaches to assess changes of autonomic cardiac modulation during sleep both in health and diseases. The use of these tools could provide important information of clinical and prognostic relevance. PMID:24137133

Tobaldini, Eleonora; Nobili, Lino; Strada, Silvia; Casali, Karina R.; Braghiroli, Alberto; Montano, Nicola

2013-01-01

114

Autonomic dysregulation in panic disorder and in post-traumatic stress disorder: application of power spectrum analysis of heart rate variability at rest and in response to recollection of trauma or panic attacks  

Microsoft Academic Search

Power spectral analysis (PSA) of heart rate variability (HRV) offers reliable assessment of cardiovascular autonomic responses, providing a ‘window’ onto the interaction of peripheral sympathetic and parasympathetic tone. Alterations in HRV are associated with various physiological and pathophysiological processes, and may contribute to morbidity and mortality. Previous studies of posttraumatic stress disorder (PTSD) found lower resting HRV in patients compared

Hagit Cohen; Jonathan Benjamin; Amir B. Geva; Mike A. Matar; Zeev Kaplan; Moshe Kotler

2000-01-01

115

Poincaré plot indexes of heart rate variability: relationships with other nonlinear variables.  

PubMed

The Poincaré plot for heart rate variability analysis is a technique considered geometrical and non-linear, that can be used to assess the dynamics of heart rate variability by a representation of the values of each pair of R-R intervals into a simplified phase space that describes the system's evolution. The aim of the present study was to verify if there is some correlation between SD1, SD2 and SD1/SD2 ratio and heart rate variability nonlinear indexes either in disease or healthy conditions. 114 patients with arterial coronary disease and 65 healthy subjects underwent 30 minute heart rate registration, in supine position and the analyzed indexes were as follows: SD1, SD2, SD1/SD2, Sample Entropy, Lyapunov Exponent, Hurst Exponent, Correlation Dimension, Detrended Fluctuation Analysis, SDNN, RMSSD, LF, HF and LF/HF ratio. Correlation coefficients between SD1, SD2 and SD1/SD2 indexes and the other variables were tested by the Spearman rank correlation test and a regression analysis. We verified high correlation between SD1/SD2 index and HE and DFA (?1) in both groups, suggesting that this ratio can be used as a surrogate variable. PMID:23755947

Hoshi, Rosangela Akemi; Pastre, Carlos Marcelo; Vanderlei, Luiz Carlos Marques; Godoy, Moacir Fernandes

2013-10-01

116

Physiological state characterization by clustering heart rate, heart rate variability and movement activity information  

Microsoft Academic Search

The objective is to identify whether it is possible to discriminate between normal and abnormal physiological state based on heart rate (HR), heart rate variability (HRV) and movement activity information in subjects with cardiovascular complications. HR, HRV and movement information were obtained from cardiac patients over a period of 6 weeks using an ambulatory activity and single lead ECG monitor.

Niranjan Bidargaddi; Antti Sarela; Ilkka Korhonen

2008-01-01

117

Heart Rate Conditioning in Newborn Infants: Relationships Among Conditionability, Heart Rate Variability, and Sex  

ERIC Educational Resources Information Center

Trace conditioning was evaluated in newborn infants by measurements of heart rate responses to a conditioned stimulus in anticipation of or in absence of the unconditioned stimulus. Data suggest females have higher levels of heart rate variability than males, which parallels their greater conditionability. (GO)

Stamps, Leighton E.; Porges, Stephen W.

1975-01-01

118

Direct observation of homoclinic orbits in human heart rate variability  

NASA Astrophysics Data System (ADS)

Homoclinic trajectories of the interbeat intervals between contractions of ventricles of the human heart are identified. The interbeat intervals are extracted from 24-h Holter ECG recordings. Three such recordings are discussed in detail. Mappings of the measured consecutive interbeat intervals are constructed. In the second and in some cases in the fourth iterate of the map of interbeat intervals homoclinic trajectories associated with a hyperbolic saddle are found. The homoclinic trajectories are often persistent for many interbeat intervals, sometimes spanning many thousands of heartbeats. Several features typical for homoclinic trajectories found in other systems were identified, including a signature of the gluing bifurcation. The homoclinic trajectories are present both in recordings of heart rate variability obtained from patients with an increased number of arrhythmias and in cases in which the sinus rhythm is dominant. The results presented are a strong indication of the importance of deterministic nonlinear instabilities in human heart rate variability.

?ebrowski, J. J.; Baranowski, R.

2003-05-01

119

Variable bit rate vector quantization of video images for packet-switched networks  

Microsoft Academic Search

The authors investigate a novel vector-quantized compression strategy that provides guaranteed image quality with variable bit rate and show its applicability to packet-switched networks. This preliminary study indicates that significant improvements in both picture quality and SNR value can be achieved. The technique can be refined by reducing the number of overhead bits for each block and by separating coding

E. Daly; T. R. Hsing

1988-01-01

120

Variable frame rate speech coding using optimal interpolation  

NASA Astrophysics Data System (ADS)

A VFR LPC vocoder using optimal interpolation is presented. In the encoder, some representative frames of an utterance are selected for transmission. In the decoder, LPC parameters of all untransmitted frames are restored by optimal interpolation. Simulation results show that this coding scheme outperforms the conventional VFR vocoder using linear interpolation. By incorporating contour quantization of gain and pitch information, a low variable-rate LPC vocoder is realized. An informal listening test shows that very high intelligible reconstructed speech was obtained at an average data rate of 300 bps.

Chen, Sin-Horng; Chung, Chii-Jen

1994-06-01

121

Heart rate variability in natural time and 1/f "noise"  

NASA Astrophysics Data System (ADS)

Several studies have shown that heart rate fluctuations exhibit the ubiquitous 1/f behavior which is altered in desease. Furthermore, the analysis of electrocardiograms in natural time reveals that important malfunctions in the complex system of the human heart can be identified. Here, we present a simple evolution model in natural time that exhibits the 1/fa behavior with a close to unity. The results of this model are consistent with a progressive modification of heart rate variability in healthy children and adolescents. The model results in complexity measures that separate healthy dynamics from patients as well as from sudden cardiac death individuals.

Sarlis, N. V.; Skordas, E. S.; Varotsos, P. A.

2009-07-01

122

Scaling and Ordering of Neonatal Heart Rate Variability  

NASA Astrophysics Data System (ADS)

By analyzing cardiac beat-to-beat intervals and interbeat increments, we find that-unlike adults-the difference in the pattern of interbeat increments in healthy and sick newborn infants is more due to a change in the amplitude and much less to a change in the ordering of the interbeat increments. This suggests that very low-frequency elements of neonatal and adult heart rate variability rise from fundamentally different mechanisms.

Aghili, Ali A.; Rizwan-Uddin, Rizwan-Uddin; Griffin, M. Pamela; Moorman, J. Randall

1995-02-01

123

Heart rate variability in exercising humans: effect of water immersion  

Microsoft Academic Search

Power spectrum analysis of heart-rate variability was made in seven men [mean age 22 (SEM 1) years] in head-out water immersion\\u000a (W) and in air (A, control) at rest and during steady-state cycling to maximal intensity (maximum oxygen uptake, V?O2max). At rest W resulted in a trebled increase in the total power (P?

Renza Perini; Stefania Milesi; Luca Biancardi; David R. Pendergast; Arsenio Veicsteinas

1998-01-01

124

Wavelet decomposition analysis of heart rate variability in aerobic athletes  

Microsoft Academic Search

Heart rate variability (HRV) can be quantified, among others, in the frequency domain using digital signal processing (DSP) techniques. The wavelet transform is an alternative tool for the analysis of non-stationary signals. The implementation of perfect reconstruction digital filter banks leads to multi resolution wavelet analysis. Software was developed in LabVIEW.In this study, the average power was compared at each

Dieter Verlinde; Frank Beckers; Dirk Ramaekers; André E. Aubert

2001-01-01

125

Heart rate variability and cognitive function: Effects of physical effort  

Microsoft Academic Search

This study investigated alterations in heart rate variability (HRV) and cognitive performance before and after physical effort, for 30 high-level track and field athletes (23 males and 7 females). Interbeat intervals were assessed at the baseline and during each task of a CogState cognitive battery (simple reaction time, choice reaction time, working memory, short-term memory and sustained attention). Time and

Caroline Di Bernardi Luft; Emílio Takase; David Darby

2009-01-01

126

Effects of bisoprolol on heart rate variability in heart failure  

Microsoft Academic Search

Analysis of heart rate variability (HRV) provides a noninvasive index of autonomic nervous system activity. HRV has been shown to be reduced in heart failure. Preliminary data indicate that ? blockers improve clinical status in patients with heart failure, but HRV improvement remains to be demonstrated. Fifty-four patients from the randomized double-blind, placebo-controlled Cardiac Insufficiency Bisoprolol Study were included in

Francoise Pousset; Xavier Copie; Philippe Lechat; Patrice Jaillon; Jean-Pierre Boissel; Martin Hetzel; Frédéric Fillette; Willem Remme; Louis Guize; Jean-Yves Le Heuzey

1996-01-01

127

Heart Rate Variability and Sustained Attention in ADHD Children  

Microsoft Academic Search

The major goal of the current study was to investigate the association between continuous performance tests (CPTs) and the heart rate variability (HRV) of attention deficit hyperactivity disorder (ADHD) children. The HRV, specifically the 0.10-Hz component, may be considered to be a psychophysiological index of effort allocation (motivation): The less effort the subject allocates, the greater the 0.10-Hz component. Results

Norbert Börger; Jaap van Der Meere; Arjen Ronner; Ed Alberts; Reint Geuze; Hans Bogte

1999-01-01

128

Heart Rate Variability and Disease Characteristics in Patients with COPD  

Microsoft Academic Search

Heart rate variability (HRV) is reduced in patients with chronic obstructive pulmonary disease (COPD). However, the relationships\\u000a among HRV and characteristics of COPD are unknown. The aim of this study was to characterize HRV in patients with COPD and\\u000a to verify the correlation of HRV measured during rest with disease severity and pulmonary, muscular, and functional impairment.\\u000a Thirty-one patients with

Carlos A. Camillo; Fabio Pitta; Heloíse V. Possani; Marcus V. R. A. Barbosa; Divina S. O. Marques; Vinícius Cavalheri; Vanessa S. Probst; Antonio F. Brunetto

2008-01-01

129

Heart rate variability and drawing impairment in hypoxemic COPD  

Microsoft Academic Search

We studied 54 patients with hypoxemic chronic obstructive pulmonary disease (COPD). The Mini Mental State Examination and the Mental Deterioration Battery were used for neuropsychological assessment. Heart rate variability (HRV) was assessed based on 24-h Holter ECG recording. Mann–Whitney test was used to compare HRV parameters of patients performing normally or abnormally on individual neuropsychological tasks. Spearman’s rho was used

Raffaele Antonelli Incalzi; Andrea Corsonello; Luigi Trojano; Claudio Pedone; Domenico Acanfora; Aldo Spada; Gianni D’Addio; Roberto Maestri; Franco Rengo; Giuseppe Rengo

2009-01-01

130

Non-linear and scale-invariant analysis of the Heart Rate Variability  

E-print Network

Human heart rate fluctuates in a complex and non-stationary manner. Elaborating efficient and adequate tools for the analysis of such signals has been a great challenge for the researchers during last decades. Here, an overview of the main research results in this field is given. The following question are addressed: (a) what are the intrinsic features of the heart rate variability signal; (b) what are the most promising non-linear measures, bearing in mind clinical diagnostic and prognostic applications.

Kalda, J; Vainu, M; Laan, M

2003-01-01

131

Heart Rate Variability During Early Adaptation to Space  

NASA Technical Reports Server (NTRS)

A recent report hypothesized that episodes of space motion sickness (SMS) were reliably associated with low frequency oscillations (less than 0.03 to less than 0.01 Hz) in heart rate variability. This paper archives a large data set for review of investigators in this field which may facilitate the evaluation of this hypothesis. Continuous recording of Electro-cardiography (ECG) and other measures were made for 6 to 12 hours per day (waking hours) of six Shuttle crewmembers for the first 3 mission days of two separate Shuttle flights. Spectral analyses of heart rate variability during approximately 200 hours of inflight is presented. In addition, nearly 200 hours of data collected on these same individuals during ground tests prior to the mission are presented. The Purpose of this Publication is to document the incidence of low frequency oscillations of heart rate in 4 people exposed to microgravity over a period of five days. In addition, this report contains spectral analyses of heart rate data collected on these same individuals during ground-based mission simulations. By archiving these data in this manner, it is our intention to make this information available to other investigators interested in studying this phenomena.

Toscano, W. B.; Cowings, P. S.

1994-01-01

132

Variable rate speech coder matching the needs of traffic reconfigurability  

NASA Astrophysics Data System (ADS)

Voice coding at variable rate could be a simple but effective way to obtain diversity schemes in satellite communications. A microprocessor based implementation of a multirate coder is illustrated. This device allows voice coding from a nominal rate of 9.6 Kbps (good speech quality) to a rate of 2.4 Kbps (standard vocoder quality). Two main tasks are the objective of the proposed system: (1) to maintain satisfactory voice quality (average standard quality) when the BER increases; and (2) to obtain a high degree of service by reducing to a minimum the number of satellite channels requested, while still maintaining an average fair quality. The analysis performed shows that this coder represents a significant advantage in low traffic zones and for remote area communications.

Mandarini, P.; Viola, R.

1985-10-01

133

Circadian Variation of Heart Rate Variability Across Sleep Stages  

PubMed Central

Study Objectives: Nocturnal cardiovascular events are more frequent at the beginning and end of the night. It was proposed that this pattern reflects the nocturnal distribution of sleep and sleep stages. Using heart rate variability (HRV), we recently showed an interaction between the circadian system and vigilance states on the regulation of cardiac rhythmicity. Here, we further investigate this interaction in order to clarify the specific effects of sleep stages on the regulation of the heart. Design: Participants underwent a 72-h ultradian sleep-wake cycle procedure in time isolation consisting of alternating 60-min wake episodes in dim light and 60-min nap opportunities in total darkness. Setting: Time isolation suite. Patients or participants: Fifteen healthy young participants; two were subsequently excluded. Interventions: N/A. Measurements and Results: The current study revealed that sleep onset and progression to deeper sleep stages was associated with a shift toward greater parasympathetic modulation, whereas rapid eye movement (REM) sleep was associated with a shift toward greater sympathetic modulation. We found a circadian rhythm of heart rate (HR) and high-frequency power during wakefulness and all non-REM sleep stages. A significant circadian rhythm of HR and sympathovagal balance of the heart was also observed during REM sleep. During slow wave sleep, maximal parasympathetic modulation was observed at ?02:00, whereas during REM sleep, maximal sympathetic modulation occurred in the early morning. Conclusion: The circadian and sleep stage-specific effects on heart rate variability are clinically relevant and contribute to the understanding of the degree of cardiovascular vulnerability during sleep. Citation: Boudreau P; Yeh WH; Dumont GA; Boivin DB. Circadian variation of heart rate variability across sleep stages. SLEEP 2013;36(12):1919-1928. PMID:24293767

Boudreau, Philippe; Yeh, Wei-Hsien; Dumont, Guy A.; Boivin, Diane B.

2013-01-01

134

Symbolic dynamics marker of heart rate variability combined with clinical variables enhance obstructive sleep apnea screening  

NASA Astrophysics Data System (ADS)

Many sleep centres try to perform a reduced portable test in order to decrease the number of overnight polysomnographies that are expensive, time-consuming, and disturbing. With some limitations, heart rate variability (HRV) has been useful in this task. The aim of this investigation was to evaluate if inclusion of symbolic dynamics variables to a logistic regression model integrating clinical and physical variables, can improve the detection of subjects for further polysomnographies. To our knowledge, this is the first contribution that innovates in that strategy. A group of 133 patients has been referred to the sleep center for suspected sleep apnea. Clinical assessment of the patients consisted of a sleep related questionnaire and a physical examination. The clinical variables related to apnea and selected in the statistical model were age (p < 10-3), neck circumference (p < 10-3), score on a questionnaire scale intended to quantify daytime sleepiness (p < 10-3), and intensity of snoring (p < 10-3). The validation of this model demonstrated an increase in classification performance when a variable based on non-linear dynamics of HRV (p < 0.01) was used additionally to the other variables. For diagnostic rule based only on clinical and physical variables, the corresponding area under the receiver operating characteristic (ROC) curve was 0.907 (95% confidence interval (CI) = 0.848, 0.967), (sensitivity 87.10% and specificity 80%). For the model including the average of a symbolic dynamic variable, the area under the ROC curve was increased to 0.941 (95% = 0.897, 0.985), (sensitivity 88.71% and specificity 82.86%). In conclusion, symbolic dynamics, coupled with significant clinical and physical variables can help to prioritize polysomnographies in patients with a high probability of apnea. In addition, the processing of the HRV is a well established low cost and robust technique.

Ravelo-García, A. G.; Saavedra-Santana, P.; Juliá-Serdá, G.; Navarro-Mesa, J. L.; Navarro-Esteva, J.; Álvarez-López, X.; Gapelyuk, A.; Penzel, T.; Wessel, N.

2014-06-01

135

Symbolic dynamics marker of heart rate variability combined with clinical variables enhance obstructive sleep apnea screening.  

PubMed

Many sleep centres try to perform a reduced portable test in order to decrease the number of overnight polysomnographies that are expensive, time-consuming, and disturbing. With some limitations, heart rate variability (HRV) has been useful in this task. The aim of this investigation was to evaluate if inclusion of symbolic dynamics variables to a logistic regression model integrating clinical and physical variables, can improve the detection of subjects for further polysomnographies. To our knowledge, this is the first contribution that innovates in that strategy. A group of 133 patients has been referred to the sleep center for suspected sleep apnea. Clinical assessment of the patients consisted of a sleep related questionnaire and a physical examination. The clinical variables related to apnea and selected in the statistical model were age (p?variable based on non-linear dynamics of HRV (p?variables. For diagnostic rule based only on clinical and physical variables, the corresponding area under the receiver operating characteristic (ROC) curve was 0.907 (95% confidence interval (CI)?=?0.848, 0.967), (sensitivity 87.10% and specificity 80%). For the model including the average of a symbolic dynamic variable, the area under the ROC curve was increased to 0.941 (95%?=?0.897, 0.985), (sensitivity 88.71% and specificity 82.86%). In conclusion, symbolic dynamics, coupled with significant clinical and physical variables can help to prioritize polysomnographies in patients with a high probability of apnea. In addition, the processing of the HRV is a well established low cost and robust technique. PMID:24985458

Ravelo-García, A G; Saavedra-Santana, P; Juliá-Serdá, G; Navarro-Mesa, J L; Navarro-Esteva, J; Álvarez-López, X; Gapelyuk, A; Penzel, T; Wessel, N

2014-06-01

136

General anesthesia suppresses normal heart rate variability in humans  

NASA Astrophysics Data System (ADS)

The human heart normally exhibits robust beat-to-beat heart rate variability (HRV). The loss of this variability is associated with pathology, including disease states such as congestive heart failure (CHF). The effect of general anesthesia on intrinsic HRV is unknown. In this prospective, observational study we enrolled 100 human subjects having elective major surgical procedures under general anesthesia. We recorded continuous heart rate data via continuous electrocardiogram before, during, and after anesthesia, and we assessed HRV of the R-R intervals. We assessed HRV using several common metrics including Detrended Fluctuation Analysis (DFA), Multifractal Analysis, and Multiscale Entropy Analysis. Each of these analyses was done in each of the four clinical phases for each study subject over the course of 24 h: Before anesthesia, during anesthesia, early recovery, and late recovery. On average, we observed a loss of variability on the aforementioned metrics that appeared to correspond to the state of general anesthesia. Following the conclusion of anesthesia, most study subjects appeared to regain their normal HRV, although this did not occur immediately. The resumption of normal HRV was especially delayed on DFA. Qualitatively, the reduction in HRV under anesthesia appears similar to the reduction in HRV observed in CHF. These observations will need to be validated in future studies, and the broader clinical implications of these observations, if any, are unknown.

Matchett, Gerald; Wood, Philip

2014-06-01

137

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING PARABOLIC FLIGHTS  

E-print Network

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were assessed in this study to assess the heart rate variability (HRV) and blood pres- sure variability (BPV). Due to gravity

138

Rates of profit as correlated sums of random variables  

NASA Astrophysics Data System (ADS)

Profit realization is the dominant feature of market-based economic systems, determining their dynamics to a large extent. Rather than attaining an equilibrium, profit rates vary widely across firms, and the variation persists over time. Differing definitions of profit result in differing empirical distributions. To study the statistical properties of profit rates, I used data from a publicly available database for the US Economy for 2009-2010 (Risk Management Association). For each of three profit rate measures, the sample space consists of 771 points. Each point represents aggregate data from a small number of US manufacturing firms of similar size and type (NAICS code of principal product). When comparing the empirical distributions of profit rates, significant ‘heavy tails’ were observed, corresponding principally to a number of firms with larger profit rates than would be expected from simple models. An apparently novel correlated sum of random variables statistical model was used to model the data. In the case of operating and net profit rates, a number of firms show negative profits (losses), ruling out simple gamma or lognormal distributions as complete models for these data.

Greenblatt, R. E.

2013-10-01

139

Heart rate variability and its relation to ventricular arrhythmias in congestive heart failure  

Microsoft Academic Search

BACKGROUND--It has been shown that heart rate variability is decreased in patients with congestive heart failure and that depressed heart rate variability is associated with a propensity to ventricular arrhythmias. Little is known, however, about heart rate variability in patients with both congestive heart failure and ventricular arrhythmias. METHODS--Spectral heart rate variability was analysed from 24 hour ambulatory electrocardiograms in

L. Fei; P. J. Keeling; J. S. Gill; Y. Bashir; D. J. Statters; J. Poloniecki; W. J. McKenna; A. J. Camm

1994-01-01

140

Long term effects of amlodipine on heart rate and heart rate variability in essential hypertensives  

Microsoft Academic Search

We studied the influence of long term therapy, in essential hypertensives, with the CCB amlodipine, on sympathetic and parasympathetic activity, by analyzing heart rate and heart rate variability. 28 patients (16 male, 12 female, mean age 60+9,7yrs) with essential hypertension (stage 1 or 2 according the sixth report of the JNC) received daily 5mg amlodipine as monotherapy. In those remaining

Ilias Zarkos; Gerasimos Livieratos; Irini Vrana; Padelis Sinnis; Nearchos Nearchou; Eleftherios A. Thireos

2001-01-01

141

Heart rate variability biofeedback: how and why does it work?  

PubMed

In recent years there has been substantial support for heart rate variability biofeedback (HRVB) as a treatment for a variety of disorders and for performance enhancement (Gevirtz, 2013). Since conditions as widely varied as asthma and depression seem to respond to this form of cardiorespiratory feedback training, the issue of possible mechanisms becomes more salient. The most supported possible mechanism is the strengthening of homeostasis in the baroreceptor (Vaschillo et al., 2002; Lehrer et al., 2003). Recently, the effect on the vagal afferent pathway to the frontal cortical areas has been proposed. In this article, we review these and other possible mechanisms that might explain the positive effects of HRVB. PMID:25101026

Lehrer, Paul M; Gevirtz, Richard

2014-01-01

142

Heart Rate Variability in Sleep-Related Migraine without Aura  

PubMed Central

Objectives: This is an observational study aimed to investigate the activity of autonomic nervous system during sleep in patients with sleep-related migraine. Methods: Eight consecutive migraineurs without aura were enrolled (6 women and 2 men), aged 30 to 62 years (mean 48.1 ± 9.3 years). Inclusion criteria were: high frequency of attacks (> 5 per month) and occurrence of more than 75% of the attacks during sleep causing an awakening. Patients were compared with a control group of 55 healthy subjects (23 men and 32 women, mean age 54.2 ± 13.0 years), and with a further control group of 8 age- and gender-matched healthy controls. Patient and controls underwent polysomnography and heart rate variability analysis. Results: A significant reduction of the LF/HF ratio during N2 and N3 sleep stages was observed in migraineurs compared with controls. No differences in sleep macrostructure were observed; cyclic alternating pattern (CAP) time and CAP rate were lower in migraineurs than in controls. Conclusions: These findings indicate a peculiar modification of the autonomic balance during sleep in sleep-related migraine. The reduction of LF/HF ratio in NREM sleep was observed in controls, but it was quantitatively much more evident in migraineurs. Changes in LF/HF could be consequent to an autonomic unbalance which could manifest selectively (or alternatively become more evident) during sleep. These findings, together with the reduction in CAP rate, could be an expression of reduced arousability during sleep in patients with sleep-related migraine. The simultaneous involvement of the autonomic, arousal, and pain systems might suggest involvement of the hypothalamic pathways. Citation: Vollono C; Gnoni V; Testani E; Dittoni S; Losurdo A; Colicchio S; Di Blasi C; Mazza S; Farina B; Della Marca G. Heart rate variability in sleep-related migraine without aura. J Clin Sleep Med 2013;9(7):707-714. PMID:23853566

Vollono, Catello; Gnoni, Valentina; Testani, Elisa; Dittoni, Serena; Losurdo, Anna; Colicchio, Salvatore; Di Blasi, Chiara; Mazza, Salvatore; Farina, Benedetto; Della Marca, Giacomo

2013-01-01

143

Heart rate variability is related to training load variables in interval running exercises  

Microsoft Academic Search

Overload principle of training states that training load (TL) must be sufficient to threaten the homeostasis of cells, tissues,\\u000a organs and\\/or body. However, there is no “golden standard” for TL measurement. The aim of the present study was to investigate\\u000a if post-exercise heart rate variability (HRV) could be used to evaluate TL of interval running exercises with different intensities\\u000a and

Piia Kaikkonen; Esa Hynynen; Theresa Mann; Heikki Rusko; Ari Nummela

144

New algorithm for variable-rate linear broadcast network coding  

Microsoft Academic Search

To adjust the variance of source rate in linear broadcast networks, global encoding kernels should have corresponding dimensions\\u000a to instruct the decoding process. The algorithm of constructing such global encoding kernels is to adjust heterogeneous network\\u000a to possible link failures. Linear algebra, graph theory and group theory are applied to construct one series of global encoding\\u000a kernels which are applicable

Yin Xia; Ti-yuan Zhang; Jia-qing Huang

2011-01-01

145

Heart rate variability in children with type 1 diabetes mellitus  

PubMed Central

OBJECTIVE: To gather current information about the effects of type 1 diabetes mellitus on children's cardiac autonomic behavior. DATA SOURCES: The search of articles was conducted on PubMed, Ibecs, Medline, Cochrane, Lilacs, SciELO and PEDro databases using the MeSH terms: "autonomic nervous system", "diabetes mellitus", "child", "type 1 diabetes mellitus", "sympathetic nervous system" and "parasympathetic nervous system", and their respective versions in Portuguese (DeCS). Articles published from January 2003 to February 2013 that enrolled children with 9-12 years old with type 1 diabetes mellitus were included in the review. DATA SYNTHESIS: The electronic search resulted in four articles that approached the heart rate variability in children with type 1 diabetes mellitus, showing that, in general, these children present decreased global heart rate variability and vagal activity. The practice of physical activity promoted benefits for these individuals. CONCLUSIONS: Children with type 1 diabetes mellitus present changes on autonomic modulation, indicating the need for early attention to avoid future complications in this group. PMID:25119762

Gardim, Camila Balsamo; de Oliveira, Bruno Affonso P.; Bernardo, Aline Fernanda B.; Gomes, Rayana Loch; Pacagnelli, Francis Lopes; Lorenconi, Roselene Modolo R.; Vanderlei, Luiz Carlos M.

2014-01-01

146

Heart-rate variability and precompetitive anxiety in swimmers.  

PubMed

The aim of this study was to test the utility of heart-rate variability (HRV) analyses as a noninvasive means of quantifying cardiac autonomic regulation during precompetitive anxiety situations in swimmers. Psychophysiological state evaluation of 10 volunteer swimmers (6 women and 4 men) was obtained by comparing baseline training condition (TC) with competition condition (CC). Self-evaluation of precompetitive somatic anxiety measured by CSAI-2 showed significant increase from the TC to CC. Analysis showed that during higher precompetitive anxiety level, a significant reduction in the timing (RMSSD), frequency (HFms2 and HFnu) and Poincaré plot (SD1) of heart-rate variability was observed, and a significant increase in the low frequency to high frequency ratio (LF/HF %). The results indicate a shift towards sympathetic predominance as a result of parasympathetic withdrawal. Our results provide an HRV analysis in a valid, useful and non-invasive way to evaluate the change of sympathovagal balance in presence of precompetitive stress. PMID:19861094

Cervantes Blásquez, Julio César; Rodas Font, Gil; Capdevila Ortís, Lluís

2009-11-01

147

Kramers-Moyal Expansion of Heart Rate Variability  

NASA Astrophysics Data System (ADS)

The first six Kramers-Moyal coefficients were extracted from human heart rate variability recordings. The method requires the determination of the Markov time and of the proper conditional probability densities. We analyzed heart rate data recorded in a group of ten young, healthy subjects. We obtained non-negligible higher order Kramers-Moyal (K-M) terms in 6 h nighttime parts of the 24 h recordings. This indicates that the data is a non-Gaussian process and probably a correlated signal. The analysis yielded important new insights into the character and distribution of the stochastic processes measured in healthy group. In the night hours, the dominant oscillation in the heart rate is the so called respiratory sinus arrhythmia (RSA) -- a physiological phenomenon in which respiration acts as a drive for the heart rate. Certain kinds of pathology may disrupt RSA. We compared nighttime recordings of the healthy group with those recorded in six patients with hypertrophic cardiomyopathy (HCM). HCM is generally a pathology of heart cells but abnormalities in autonomic regulation are also observed. Using the higher order Kramers-Moyal coefficients, we analyzed the skewness and kurtosis in the nighttime recordings for the normal subjects.

Petelczyc, M.; ?ebrowski, J. J.; Baranowski, R.

2009-05-01

148

Variable-speech-rate audiometry for hearing aid evaluation.  

PubMed

A new hearing aid evaluation method using variable-speech-rate audiometry (VSRA) was developed. VSRA was newly created based on the Japanese speech audiometry authorized by the Japan Audiological Society. The ordinary speech audiometry can not reveal a temporal factor in word discrimination ability of the hearing impaired. Since, with VSRA, we can compare several performance-intensity curves obtained from different speech-rate speech audiometries, the impact on the auditory system of each patient by the fast or slow speech rate could be easily determined. Taking the temporal factor of the auditory systems into consideration by using VSRA, hearing aid evaluation was performed for a master hearing aid with three types of signal processing and fitting for 36 hearing impaired subjects. Then hearing aid evaluation was performed using VSRA for a newly developed portable multi-function digital hearing aid with two types of signal processing and analog hearing aids which had been used by hearing-impaired patients. As a result, VSRA was useful for hearing aid evaluation, in particular, for cases when ordinary normal speech rate audiometry does not provide a significant difference in word discrimination scores. In addition, using VSRA revealed that amplitude compression is more effective for improvement of word discrimination than linear amplification. PMID:10077252

Hosoi, H; Tsuta, Y; Nishida, T; Murata, K; Ohta, F; Mekata, T; Kato, Y

1999-01-01

149

On the Primacy of Molecular Processes in Determining Response Rates under Variable-Ratio and Variable-Interval Schedules  

ERIC Educational Resources Information Center

This study focused on variables that may account for response-rate differences under variable-ratio (VR) and variable-interval (VI) schedules of reinforcement. Four rats were exposed to VR, VI, tandem VI differential- reinforcement-of-high-rate, regulated-probability-interval, and negative-feedback schedules of reinforcement that provided the same…

Tanno, Takayuki; Sakagami, Takayuki

2008-01-01

150

13 CFR 120.214 - What conditions apply for variable interest rates?  

Code of Federal Regulations, 2010 CFR

...What conditions apply for variable interest rates? 120.214 Section 120...to 7(a) Loans Maturities; Interest Rates; Loan and Guarantee Amounts...What conditions apply for variable interest rates? A Lender may use a...

2010-01-01

151

Multiscale Analysis of Heart Rate Variability: A Comparison of Different Complexity Measures  

E-print Network

Multiscale Analysis of Heart Rate Variability: A Comparison of Different Complexity Measures JING; published online 12 December 2009) Abstract--Heart rate variability (HRV) is an important dynamical variable parameter, the sample entropy, and the multiscale entropy. Keywords--Heart rate variability, Cardiovascular

Gao, Jianbo

152

Heart rate and heart rate variability responses to Tai Chi and jogging in Beijing and Graz  

PubMed Central

Background: Tai Chi is a famous training method in China, and jogging is a popular kind of exercise both in Austria and China. Nevertheless, there is little information concerning online monitoring of biosignals during both training activities in parallel. Within the last years innovative scientific monitoring tools for evaluating features of neurocardial fitness have been developed. Aims: The goal of this study was to demonstrate heart rate and heart rate variability analysis for the first time during Tai Chi and jogging. Volunteers and Methods: Continuous electrocardiographic monitoring over a period of 75 minutes was performed simultaneously in two healthy volunteers using the same type of equipment (medilog AR12 systems). Two healthy persons (both male, 49 years and 52 years, respectively), both hobby sportsmen, were monitored continuously during two resting periods before and after active sport and also during Tai Chi and jogging, respectively. Results: Data acquisition was performed without any technical problems in both subjects. Poincaré plots of sequential R-R intervals (beat to beat variability) show two ellipses of different shape and magnitude. During resting periods blood pressure effects can be clearly seen in one subject (jogging). The same effects, however reduced, are obvious in the other volunteer during Tai Chi. Conclusions: The present investigations during Tai Chi and jogging highlight the potential value of heart rate and heart rate variability monitoring even under difficult conditions. The innovative kind of analysis helps to show how well the human body reacts to sport, stress and recovery. PMID:22540068

Litscher, Gerhard; Zhang, Weibo; Huang, Tao; Wang, Lu

2011-01-01

153

Heart rate variability and sympathovagal balance: pharmacological validation  

PubMed Central

Rationale We validated heart rate (HR) and six time and six frequency domain measures of heart rate variability (HRV) as estimators of autonomic outflow in 44 young healthy male subjects. Gold standards for autonomic outflow were the Rosenblueth-Simeone factors m (sympathetic tone) and n (vagal tone), and the sympathovagal balance m·n, determined by two-stage complete autonomic blockade. Methods Rank correlations were computed between HR and the HRV measures obtained before autonomic blockade, and m, n and m·n. Also, the maximal mean performances (averaged sensitivity and specificity) for HR and HRV as discriminators between low and high values of m, n or m·n were computed. Results The spectral HRV measures showed less good correlations and performances than the time domain HRV measures. Correlations with sympathetic tone were all below 0.31. Respiratory sinus arrhythmia during 15 cycles/min metronome breathing was superior in estimating vagal tone and sympathovagal balance (correlations -0.71/-0.73; both performances 0.82), heart rate scored similarly for assessing the sympathovagal balance (correlation 0.71; performance 0.82). Conclusions It does not appear justified to evaluate HR or HRV in terms of sympathetic tone, vagal tone, or sympathovagal balance. HR and HRV are specifically weak in assessing sympathetic tone. Respiratory sinus arrhythmia during 15 cycles/min metronome breathing is superior in assessing vagal tone. Current HRV analysis techniques offer no advantages compared with HR in assessing the sympathovagal balance.

Bootsma, M.; Swenne, C.A.; Janssen, M.J.A.; Cats, V. Manger; Schalij, M.J.

2003-01-01

154

Music structure determines heart rate variability of singers.  

PubMed

Choir singing is known to promote wellbeing. One reason for this may be that singing demands a slower than normal respiration, which may in turn affect heart activity. Coupling of heart rate variability (HRV) to respiration is called Respiratory sinus arrhythmia (RSA). This coupling has a subjective as well as a biologically soothing effect, and it is beneficial for cardiovascular function. RSA is seen to be more marked during slow-paced breathing and at lower respiration rates (0.1 Hz and below). In this study, we investigate how singing, which is a form of guided breathing, affects HRV and RSA. The study comprises a group of healthy 18 year olds of mixed gender. The subjects are asked to; (1) hum a single tone and breathe whenever they need to; (2) sing a hymn with free, unguided breathing; and (3) sing a slow mantra and breathe solely between phrases. Heart rate (HR) is measured continuously during the study. The study design makes it possible to compare above three levels of song structure. In a separate case study, we examine five individuals performing singing tasks (1-3). We collect data with more advanced equipment, simultaneously recording HR, respiration, skin conductance and finger temperature. We show how song structure, respiration and HR are connected. Unison singing of regular song structures makes the hearts of the singers accelerate and decelerate simultaneously. Implications concerning the effect on wellbeing and health are discussed as well as the question how this inner entrainment may affect perception and behavior. PMID:23847555

Vickhoff, Björn; Malmgren, Helge; Aström, Rickard; Nyberg, Gunnar; Ekström, Seth-Reino; Engwall, Mathias; Snygg, Johan; Nilsson, Michael; Jörnsten, Rebecka

2013-01-01

155

Heart rate variability at different thermal comfort levels.  

PubMed

The mechanism of human thermal comfort is important for building a comfortable and healthy indoor environment. This paper analyzes human heart rate variability (HRV) at different thermal comfort levels and discusses the mechanism of human thermal comfort. A total of 33 subjects were divided in 3 groups. Under air temperatures of 21, 24, 26, 28, 29, and 30 degrees C, the subjects' electrocardiogram was recorded for 5 min. HRV (the ratio of absolute powers in low- and high-frequency bands, LF/HF ratio) was analyzed. LF/HF at discomfort level were significantly higher than that at comfort level (P < 0.05), despite the same thermal sensation. The results indicate that sympathetic activity plays an important role in subjects' thermal discomfort and the LF/HF ratio may be used as an indicator for human thermal comfort. PMID:18351379

Liu, Weiwei; Lian, Zhiwei; Liu, Yuanmou

2008-06-01

156

Heart Rate Variability Dynamics for the Prognosis of Cardiovascular Risk  

PubMed Central

Statistical, spectral, multi-resolution and non-linear methods were applied to heart rate variability (HRV) series linked with classification schemes for the prognosis of cardiovascular risk. A total of 90 HRV records were analyzed: 45 from healthy subjects and 45 from cardiovascular risk patients. A total of 52 features from all the analysis methods were evaluated using standard two-sample Kolmogorov-Smirnov test (KS-test). The results of the statistical procedure provided input to multi-layer perceptron (MLP) neural networks, radial basis function (RBF) neural networks and support vector machines (SVM) for data classification. These schemes showed high performances with both training and test sets and many combinations of features (with a maximum accuracy of 96.67%). Additionally, there was a strong consideration for breathing frequency as a relevant feature in the HRV analysis. PMID:21386966

Ramirez-Villegas, Juan F.; Lam-Espinosa, Eric; Ramirez-Moreno, David F.; Calvo-Echeverry, Paulo C.; Agredo-Rodriguez, Wilfredo

2011-01-01

157

Heart rate variability and motion sickness during forklift simulator driving.  

PubMed

The goal of the study was to determine the effect of a 1-h hour long forklift truck virtual simulator driving on the mechanism of autonomic heart rate (HR) regulation in operators. The participants were divided into 2 subgroups: subjects with no definite inclination to motion sickness (group A) and subjects with a definite inclination to motion sickness (group B). Holter monitoring of electrocardiogram (ECG) signal was carried out in all subjects during the virtual simulator driving. For 12 consecutive epochs of ECG signal, HR variability analysis was conducted in time and frequency domains. In subjects with a definite inclination to motion sickness after ~30 min of the driving, changes in parameter values were found indicating an increase in sympathetic and parasympathetic activity with parasympathetic dominance. PMID:22152505

Zu?ewicz, Krystyna; Saulewicz, Antoni; Konarska, Maria; Kaczorowski, Zbigniew

2011-01-01

158

Assessment of heart rate variability from speech analysis.  

PubMed

In this paper, various methods of heart beat variability assessment from speech analysis have been presented. Heart rate variability (HRV) is a physiological phenomenon where the time interval between heart beats varies. It is measured by the variation in the beat-to-beat interval. The present work deals with the HRV detection from speech parameters. RR-cycle detects one heart beat. Continuous monitoring of electrocardiograph for a span of time can provide HRV. More than 250 samples of normal informants as well as heart patients with enlarged heart have been collected during the four years of research work. The regular ECG and speech samples of the patient have been collected and analyzed. Further they had compared with the parameters of a normal healthy informant. Speech samples were collected through a microphone and subjected to be digitized. The required speech segmental have been extracted and analyzed through a DSP tool, PRAAT. ECG sample has been recorded through an ECG machine. A technique of HRV detection from speech analysis has been presented in this paper. The HRV detection from speech can be a very helpful tool in monitoring the functioning of human heart. PMID:25236132

Deshpande, Nivedita; Thakur, Kavita; Zadgaonkar, Arun S

2014-04-01

159

Estrogen can modulate menopausal women's heart rate variability.  

PubMed

The aim of our study was to compare the responses of heart rate variability (HRV) with two different types of hormonal substitution therapy (HT) in post-menopausal women (cross-sectional study) and to reveal an effect of HT shortly after beginning of its administration (follow-up study). To elucidate the influence of menopause and effects of different protocols of a HT on autonomic control of heart rate, we evaluated the heart rate variability (HRV) in 5 groups: premenopausal women (n=140), postmenopausal women without HT (n=360), women on HT with conjugated estrogen only (n=168), women on continuous combined estrogen-progesterone HT (n=117), and men (n=140). Frequency-domain of short-term stationary R-R intervals was performed to evaluate the total variance, low frequency power (LF; 0.04-0.15 Hz), high frequency power (HF; 0.15-0.40 Hz), portion of low frequency power (LF%) and ratio of LF to HF (LF/HF). Significantly lower portion of the LF was found in premenopausal women [46.9 (+/-2.7) nu] when compared to untreated postmenopausal women [54.3 (+/-2.9) nu] and men [55.2 (+/-3.0) nu]. Treatment by estrogen only was proved to decrease the LF% [40.1 (+/-2.1) nu] while no effect on HRV was observed in women treated with combination of estrogen and progesterone [57.2 (+/-3.1) nu]. Also the HF was lower in postmenopausal women [4.16 (+/-0.16) ms(2)] than in premenopausal women [4.79 (+/-0.22) ms(2)] and women treated with estrogen only [4.98 (+/-0.25) ms(2)] while in women treated with combined hormonal therapy the average value [3.99 (+/-0.21) ms(2)] did not significantly differ from that of untreated postmenopausal women. The follow-up study also proved increase of high frequency power already after two months of estrogen substitution therapy [4.86 (+/-0.14) ms(2) vs. 4.19 (+/-0.15) ms(2)]. These results suggest that higher vagal modulation of heart rate that seems typical for younger women becomes after menopause similar to that of men. We also proved a positive shift of HRV parameters toward more beneficial values as for a cardiovascular risk in postmenopausal women treated with estrogens but not in those treated by combined estrogen - progesterone substitution therapy. PMID:24329696

Yang, S-G; Ml?ek, M; Kittnar, O

2013-12-12

160

Influence of sound and light on heart rate variability.  

PubMed

The effects of acoustic and visual stimuli and their synergistic effects on heart rate variability including gender differences were investigated. Of particular interest was the influence of visual stimulus on heart rate variability during listening to simple sounds of different characters. Twelve male and 12 female university students were selected as subjects. The subjects listened at rest to 7 different figures of sound at loudness levels averaging 60 dB. Beat-to-beat R-R intervals were continuously recorded under the closed-eye condition (CEC) and the open-eye condition (OEC) prior to, during, and immediately after the exposure to acoustic stimuli. Low frequency (LF) power was defined over 0.04-0.15 Hz and high frequency (HF) power over 0.15-0.40 Hz. Cardiac autonomic function was estimated by plotting LF/HF in standard measure against HF in standard measure and by plotting LF/HF (%) against HF (%), accompanied by a demarcated central area. Values of LF/HF tended to be smaller under CEC than under OEC. Values of HF while listening to a 110 Hz sine wave under CEC were significantly greater than values for 880 Hz and 3520 Hz sine waves, or for 110 Hz or 880 Hz sawtooth waves, under OEC. Under CEC, values of HF for 7 figures of sound were greater in females than in males. The value of HF of sine wave for 110 Hz under CEC and OEC was significantly greater than that for white noise under the OEC. The results suggest that the cardiac parasympathetic nervous activity during auditory excitation increases with elimination of visual stimuli and tends to be greater in females than in males. PMID:17393762

Hori, Kiyokazu; Yamakawa, Masanobu; Tanaka, Nobuo; Murakami, Hiromi; Kaya, Mitsuharu; Hori, Seiki

2005-12-01

161

The relationship between resting heart rate variability and heart rate recovery  

Microsoft Academic Search

Objective  There is limited research available regarding a possible relationship between resting heart rate variability (HRV) and post-exercise\\u000a heart rate recovery (HRR). The aim of this study was to examine the relationship between resting HRV and HRR after maximal\\u000a exercise.\\u000a \\u000a \\u000a \\u000a Methods  Sixty-six college age men participated in this study. HRV was measured in a supine position before and for 30 min after a

Michael R. Esco; Michele S. Olson; Henry N. Williford; Daniel L. Blessing; David Shannon; Peter Grandjean

2010-01-01

162

Variable beam dose rate and DMLC IMRT to moving body anatomy  

SciTech Connect

Derivation of formulas relating leaf speeds and beam dose rates for delivering planned intensity profiles to static and moving targets in dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is presented. The analysis of equations determining algorithms for DMLC IMRT delivery under a variable beam dose rate reveals a multitude of possible delivery strategies for a given intensity map and for any given target motion patterns. From among all equivalent delivery strategies for DMLC IMRT treatments specific subclasses of strategies can be selected to provide deliveries that are particularly suitable for clinical applications providing existing delivery devices are used. Special attention is devoted to the subclass of beam dose rate variable DMLC delivery strategies to moving body anatomy that generalize existing techniques of such deliveries in Varian DMLC irradiation methodology to static body anatomy. Few examples of deliveries from this subclass of DMLC IMRT irradiations are investigated to illustrate the principle and show practical benefits of proposed techniques.

Papiez, Lech; Abolfath, Ramin M. [Department of Radiation Oncology, UTSouthwestern Medical Center, Dallas, Texas 75390 (United States)

2008-11-15

163

Effects of different training amplitudes on heart rate and heart rate variability in young rowers.  

PubMed

Vaz, MS, Picanço, LM, and Del Vecchio, FB. Effects of different training amplitudes on heart rate and heart rate variability in young rowers. J Strength Cond Res 28(10): 2967-2972, 2014-The aim of this study was to investigate the autonomic nervous system recovery and the psychological response as a result of 3 training amplitudes on heart rate (HR), heart rate variability (HRV), and rate of perceived exertion (RPE) in rowing. Eight young rowers (16.8 ± 1.4 years) performed, in a randomized fashion, 2 sessions of high-intensity interval training, with high and low amplitude and a continuous training (CT) session, with the same exercise duration (10 minutes) and mean intensity (60% of maximal stroke test). The data of HR, HRV, and RPE were collected 5 minutes before, immediately after each session, and 24 hours later. High amplitude promoted higher impact in maximum HR (p ? 0.05) and RPE (p < 0.001) when compared with CT. For the time domain HRV variable, there was a statistically significant difference between moments of rest (pretraining or post 24 hours) and posttraining in all training sessions. Originally, we conclude that training with higher load variation between effort and recovery impacts HRV, HR, and RPE with greater intensity, but the younger rowers were ready for new training sessions 24 hours after either training method. Coaches can use the polarized training method, observing the stimulus nature and time required for recovery, because it may be an adequate strategy for the development of rower's conditioning. PMID:24736775

Vaz, Marcelo S; Picanço, Luan M; Del Vecchio, Fabrício B

2014-10-01

164

Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing  

NASA Astrophysics Data System (ADS)

Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc™ deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to <=± 5°. This restriction requires the treatment arc to be broken into multiple sectors such that the local MU fluctuation within each sector is reduced, thereby lowering the angular deviation of the segments during redistribution. The converted CDR plans were delivered with a single gantry sweep as in the VDR plans but each sector was delivered with a different value of CDR. For four patient cases, including two head-and-neck, one brain and one prostate, all CDR plans developed with the variable spacing scheme produced similar dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was delivered with a different dose rate, extra mode-up time (xMOT) was needed between the transitions of the successive sectors during delivery. On average, the delivery times of the CDR plans were approximately less than 1 min longer than the treatment times of the VDR plans, with an average of about 0.33 min of xMOT per sector transition. The results have shown that VDR may not be necessary for single-arc IMAT. Using variable angular spacing, VDR RapidArc plans can be implemented into the clinics that are not equipped with the new VDR-enabled machines without compromising the plan quality or treatment efficiency. With a prospective optimization approach using variable angular spacing, CDR delivery times can be further minimized while maintaining the high delivery efficiency of single-arc IMAT treatment.

Tang, Grace; Earl, Matthew A.; Yu, Cedric X.

2009-11-01

165

Decreased heart rate variability in surgeons during night shifts  

PubMed Central

Background Heart rate variability (HRV) has been used as a measure of stress and mental strain in surgeons. Low HRV has been associated with death and increased risk of cardiac events in the general population. The aim of this study was to clarify the effect of a 17-hour night shift on surgeons’ HRV. Methods Surgeons were monitored prospectively with an ambulatory electrocardiography device for 48 consecutive hours, beginning on a precall day and continuing through an on-call (17-h shift) day. We measured HRV by frequency domain parameters. Results We included 29 surgeons in our analysis. The median pulse rate was decreased precall (median 64, interquartile range [IQR] 56–70 beats per minute [bpm]) compared with on call (median 81, IQR 70–91 bpm, p < 0.001). Increased high-frequency (HF) activity was found precall (median 199, IQR 75–365 ms2) compared with on call (median 99, IQR 48–177 ms2, p < 0.001). The low-frequency:high-frequency (LF:HF) ratio was lower precall (median 2.7, IQR 1.9–3.9) than on call (median 4.9, IQR 3.7–6.5, p < 0.001). We found no correlation between the LF:HF ratio and performance in laparoscopic simulation. Conclusion Surgeons working night shifts had a significant decrease in HRV and a significant increase in pulse rate, representing sympathetic dominance in the autonomic nervous system. Trial registration NCT01623674 (www.clinicaltrials.gov). PMID:25265102

Amirian, Ilda; Andersen, Lærke Toftegård; Rosenberg, Jacob; Gögenur, Ismail

2014-01-01

166

Relationship between age and heart rate variability in supine and standing postures: A study of spectral analysis of heart rate  

Microsoft Academic Search

We compared heart rate variability measures of 11 normal children (4–12 years) to 23 normal adults (21–43 years) to study the effect of age on heart rate variability measures. Children had a significantly higher supine and standing heart rate and lower supine and standing systolic diastolic blood pressure. Children also had a significantly higher supine standard deviation of HR, supine

V. K. Yeragani; R. Pohl; R. Berger; R. Balon; K. Srinivasan

1994-01-01

167

Fish Consumption, Sleep, Daily Functioning, and Heart Rate Variability  

PubMed Central

Study Objectives: This study investigated the effects of fatty fish on sleep, daily functioning and biomarkers such as heart rate variability (HRV), vitamin D status (serum 25-hydroxyvitamin D (25OHD), and eicosapentaenoic acid (EPA, 20:5n-3) + docosahexaenoic acid (DHA, 22:6n-3) in red blood cells. Moreover the relationship among sleep, daily functioning, HRV, vitamin D status, and levels of EPA+DHA was investigated. Methods: Ninety-five male forensic patients from a secure forensic inpatient facility in the USA were randomly assigned into a Fish or a Control group. The Fish group received Atlantic salmon three times per week from September to February, and the Control group was provided an alternative meal (e.g., chicken, pork, beef), but with the same nutritional value as their habitual diet, three times per week during the same period. Sleep (sleep latency, sleep efficiency, actual sleep time, and actual wake time), self-perceived sleep quality and daily functioning, as well as vitamin D status, EPA+DHA, and HRV, were assessed pre- and post-intervention period. Results: There was a significant increase in sleep latency from pre- to post-test in the Control group. The Fish group reported better daily functioning than the Control group during post-test. Fish consumption throughout the wintertime had also an effect on resting HRV and EPA+DHA, but not on vitamin D status. However, at post-test, the vitamin D status in the Fish group was still closer to the level regarded as optimal compared to the Control group. Vitamin D status correlated negatively with actual wake time and positively with sleep efficiency during pre-test, as well as positively with daily functioning and sleep quality during post-test. Finally, HRV correlated negatively with sleep latency and positively with daily functioning. Conclusions: Fish consumption seemed to have a positive impact on sleep in general and also on daily functioning, which may be related to vitamin D status and HRV. Citation: Hansen AL, Dahl L, Olson G, Thornton D, Graff IE, Frøyland L, Thayer JF, Pallesen S. Fish consumption, sleep, daily functioning, and heart rate variability. J Clin Sleep Med 2014;10(5):567-575. PMID:24812543

Hansen, Anita L.; Dahl, Lisbeth; Olson, Gina; Thornton, David; Graff, Ingvild E.; Frøyland, Livar; Thayer, Julian F.; Pallesen, Staale

2014-01-01

168

Circadian periodicity of heart rate variability in hospitalized angor patients.  

PubMed

The relationship between unstable angor (angina) and circadian periodicity of heart rate variability (HRV) was explored in a group of patients hospitalized in a coronary care unit (CCU). Patients were classified as normal (whose symptoms had non-cardiovascular origin, n=8), moderate angor (n=13) and severe angor (n=11). A fourth group of ambulatory healthy volunteers (n=12) was included. Individual 24 h Holter records were analyzed, mean RR and standard deviation of RR (SDNN) being obtained from 1 h-length windows. For frequency domain analysis, 5 min-length windows were employed. The spectral components analyzed were total power (spectral power between 0.01 and 0.5 Hz), low frequency power (LF: power between 0.04 and 0.15 Hz), and high frequency power (HF: power between 0.15 and 0.4 Hz). In addition, LF to HF areas ratio (L/H) was computed. Mesor, amplitude and acrophase for every 24 h rhythm were calculated by cosinor analysis. As compared to ambulatory controls, admission to the CCU diminished amplitude and phase-delayed the circadian oscillation of most HRV parameters, except for SDNN. Moderate angor patients showed decreased amplitude of RR and L/H and augmented amplitude of SDNN when compared to normal hospitalized subjects. A phase delay of about 1.5 h for RR intervals and a phase advance of 3.5-6 h for LFA and SDNN were found in the moderate angor group when compared to normal. Amplitude of 24 h variation of total power decreased in severely angor patients and the circadian oscillation of HF (an indicator of vagal control on the heart) became free running. A phase delay of 2.5 h in SDNN acrophase was found in severely affected patients when compared to moderate. The results indicate that severity of unstable angor correlates with desynchronization of parasympathetic control of heart rate. PMID:15944873

D'Negri, Carlos E; Marelich, Liliana; Vigo, Daniel; Acunzo, Rafael S; Girotti, Luis A; Cardinali, Daniel P; Siri, Leonardo Nicola

2005-06-01

169

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2012 CFR

... (ii) Step two: Construct the equivalent fixed rate debt instrument. The equivalent fixed rate debt instrument has terms that are...rate debt instrument, except that the equivalent fixed rate debt instrument provides for the...

2012-04-01

170

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2011 CFR

... (ii) Step two: Construct the equivalent fixed rate debt instrument. The equivalent fixed rate debt instrument has terms that are...rate debt instrument, except that the equivalent fixed rate debt instrument provides for the...

2011-04-01

171

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2013 CFR

... (ii) Step two: Construct the equivalent fixed rate debt instrument. The equivalent fixed rate debt instrument has terms that are...rate debt instrument, except that the equivalent fixed rate debt instrument provides for the...

2013-04-01

172

Ear acupressure, heart rate, and heart rate variability in patients with insomnia.  

PubMed

This high-tech "teleacupuncture study" describes a neurovegetative ear acupressure effect in patients with chronic insomnia by using heart rate variability analysis. Heart rate (HR) and heart rate variability (HRV) measurements in 31 patients (mean age?±?SD: 54.3?±?10.6 years) were performed under standardized conditions in Harbin, China, and the data analysis was performed in Graz, Austria. Similar to our previous clinical and basic teleacupuncture research works, the electrocardiograms (ECGs) were recorded by an HRV Medilog AR12 system during ear acupressure of the Shenmen point on the left ear. HR decreased significantly (P < 0.05) during and after acupressure stimulation. The effect was not visible after the first stimulation, rather it appeared in the phase following the second acupressure stimulation (10 min after the first stimulation). Total HRV showed significant stimulation-dependent increases (P < 0.05), immediately after each acupressure stimulation with a maximum after the third stimulation (20 min after the first stimulation), but there was no long-lasting effect. The present results can serve as a solid basis for the further investigations of auricular point stimulation for noninvasive complementary use in treating insomnia. PMID:23476702

Wang, Lu; Cheng, Weiping; Sun, Zhongren; Xu, Yangyang; Cheng, Guangyu; Gaischek, Ingrid; Kuang, Haixue; Litscher, Gerhard

2013-01-01

173

Ear Acupressure, Heart Rate, and Heart Rate Variability in Patients with Insomnia  

PubMed Central

This high-tech “teleacupuncture study” describes a neurovegetative ear acupressure effect in patients with chronic insomnia by using heart rate variability analysis. Heart rate (HR) and heart rate variability (HRV) measurements in 31 patients (mean age?±?SD: 54.3?±?10.6 years) were performed under standardized conditions in Harbin, China, and the data analysis was performed in Graz, Austria. Similar to our previous clinical and basic teleacupuncture research works, the electrocardiograms (ECGs) were recorded by an HRV Medilog AR12 system during ear acupressure of the Shenmen point on the left ear. HR decreased significantly (P < 0.05) during and after acupressure stimulation. The effect was not visible after the first stimulation, rather it appeared in the phase following the second acupressure stimulation (10 min after the first stimulation). Total HRV showed significant stimulation-dependent increases (P < 0.05), immediately after each acupressure stimulation with a maximum after the third stimulation (20 min after the first stimulation), but there was no long-lasting effect. The present results can serve as a solid basis for the further investigations of auricular point stimulation for noninvasive complementary use in treating insomnia. PMID:23476702

Wang, Lu; Cheng, Weiping; Sun, Zhongren; Xu, Yangyang; Cheng, Guangyu; Kuang, Haixue

2013-01-01

174

Heart rate variability in type 2 diabetes mellitus.  

PubMed

Heart rate variability (HRV) is a noninvasive measure of cardiac autonomic modulation. Time and frequency domain measures have primarily been examined in patients with type 2 diabetes mellitus (T2D). Not only do frequency domain HRV parameters tend to be reduced in T2D, but healthy individuals with low HRV are also more likely to develop T2D. Furthermore, patients with T2D with low HRV have an increased prevalence of complications and risk of mortality compared with those with normal autonomic function. These findings provide support for the use of HRV as a risk indicator in T2D. Exercise is considered an important component to T2D prevention and treatment strategies. To date, few studies have examined the changes in HRV with exercise in T2D. One study showed changes in resting HRV, two studies showed changes in HRV during or following acute stressors, and one study showed no changes in HRV but improvements in baroreflex sensitivity. The most pronounced changes in HRV were realized following the exercise intervention with the greatest frequency of supervised exercise sessions and with the greatest intensity and duration of exercise bouts. These findings suggest that exercise following current American College of Sports Medicine/American Diabetes Association guidelines may be important in the prevention and treatment of T2D to improve autonomic function and reduce the risk of complications and mortality. PMID:24580567

Stuckey, Melanie I; Petrella, Robert J

2013-01-01

175

Newborn seizure detection based on heart rate variability.  

PubMed

In this paper, we investigate the use of heart rate variability (HRV) for automatic newborn seizure detection. The proposed method consists of a sequence of processing steps, namely, obtaining HRV from the ECG, extracting a discriminating HRV feature set, selecting an optimal subset from the full feature set, and, finally, classifying the HRV into seizure/nonseizure using a supervised statistical classifier. Due to the fact that HRV signals are nonstationary, a set of time-frequency features from the newborn HRV is proposed and extracted. In order to achieve efficient HRV-based automatic newborn seizure detection, a two-phase wrapper-based feature selection technique is used to select the feature subset with minimum redundancy and maximum class discriminability. Tested on ECG recordings obtained from eight newborns with identified EEG seizure, the proposed HRV-based neonatal seizure detection algorithm achieved 85.7% sensitivity and 84.6% specificity. These results suggest that the HRV is sensitive to changes in the cardioregulatory system induced by the seizure, and therefore, can be used as a basis for an automatic seizure detection. PMID:19628449

Malarvili, M B; Mesbah, Mostefa

2009-11-01

176

Heart rate variability and cognitive function: effects of physical effort.  

PubMed

This study investigated alterations in heart rate variability (HRV) and cognitive performance before and after physical effort, for 30 high-level track and field athletes (23 males and 7 females). Interbeat intervals were assessed at the baseline and during each task of a CogState cognitive battery (simple reaction time, choice reaction time, working memory, short-term memory and sustained attention). Time and frequency domain measures of HRV were compared between conditions and between tasks. The results indicated differences in HRV between executive and non-executive tasks. There was a significant increase in sympathetic-modulation-related indices after physical effort. The differences between executive and non-executive tasks were the same in post-test. Correlations were found between HRV and cognitive performance, which differed by speed and accuracy. We conclude that HRV is related to cognitive demand and that the correlation between HRV and cognitive performance seems to be stronger after physical exercise. The results raise questions about the psychophysiological meaning of different HRV signals and this has implications for future research about the relationship between HRV and cognition. PMID:19632295

Luft, Caroline Di Bernardi; Takase, Emílio; Darby, David

2009-10-01

177

Stochastic time series analysis of fetal heart-rate variability  

NASA Astrophysics Data System (ADS)

Fetal Heart Rate(FHR) is one of the important features of fetal biophysical activity and its long term monitoring is used for the antepartum(period of pregnancy before labour) assessment of fetal well being. But as yet no successful method has been proposed to quantitatively represent variety of random non-white patterns seen in FHR. Objective of this paper is to address this issue. In this study the Box-Jenkins method of model identification and diagnostic checking was used on phonocardiographic derived FHR(averaged) time series. Models remained exclusively autoregressive(AR). Kalman filtering in conjunction with maximum likelihood estimation technique forms the parametric estimator. Diagnosrics perfonned on the residuals indicated that a second order model may be adequate in capturing type of variability observed in 1 up to 2 mm data windows of FHR. The scheme may be viewed as a means of data reduction of a highly redundant information source. This allows a much more efficient transmission of FHR information from remote locations to places with facilities and expertise for doser analysis. The extracted parameters is aimed to reflect numerically the important FHR features. These are normally picked up visually by experts for their assessments. As a result long term FHR recorded during antepartum period could then be screened quantitatively for detection of patterns considered normal or abnonnal. 1.

Shariati, M. A.; Dripps, J. H.

1990-06-01

178

Heart rate variability and drawing impairment in hypoxemic COPD.  

PubMed

We studied 54 patients with hypoxemic chronic obstructive pulmonary disease (COPD). The Mini Mental State Examination and the Mental Deterioration Battery were used for neuropsychological assessment. Heart rate variability (HRV) was assessed based on 24-h Holter ECG recording. Mann-Whitney test was used to compare HRV parameters of patients performing normally or abnormally on individual neuropsychological tasks. Spearman's rho was used to investigate the correlations between HRV parameters and neuropsychological scores, indexes of health status or COPD severity. Patients with defective performance at copying drawings with landmarks (CDL) test (N = 23) had lower very low frequency (VLF) power with respect to patients with normal performance (N = 31) (24 h: median 213; interquartile range 120-282 vs. 309; 188-431 ms2, p = 0.043; daytime: 202; 111-292 vs. 342; 194-397 ms2, p = 0.039). The CDL score correlated with the VLF power (24 h: rho = 0.27, p = 0.049; daytime: rho = 0.30, p = 0.028), and the normalized low frequency/high frequency (LF/HF) ratio (24 h: rho = 0.27, p = 0.05; daytime: rho = 0.33, p = 0.015). Sympathetic modulation decreased for increasing severity of COPD. In conclusion, drawing impairment correlates with depressed sympathetic modulation in patients with COPD, and both might be indexes of COPD severity. PMID:19261365

Antonelli Incalzi, Raffaele; Corsonello, Andrea; Trojano, Luigi; Pedone, Claudio; Acanfora, Domenico; Spada, Aldo; D'Addio, Gianni; Maestri, Roberto; Rengo, Franco; Rengo, Giuseppe

2009-06-01

179

Classification of heart rate variability in patients with mild hypertension.  

PubMed

The diagnostic performance of two pattern classification methods to detect hypertension was evaluated in a population of 29 mildly hypertensive and 20 normal subjects. The heart rate variability (HRV) signal of each subject was recorded during rest and isometric handgrip exercise. Feature vectors composed of up to 6 features from both the time and frequency domain representation of the HRV signal were constructed and applied to a Bayes' likelihood classifier and a voting k-nearest neighbours classifier. Each subject was classified as hypertensive or normal, and the classification compared to the clinical diagnosis for each subject. The diagnostic performance of each classifier/feature vector combination was evaluated using the leave-one-out method. The best performance of 90% correct classifications was achieved using a nearest neighbour classifier, a Euclidean distance metric and 3 features. The Bayes' classifier achieved a best performance of 84% correct classification. The work shows promise for the detection of the autonomic disturbance which precedes and accompanies the hypertensive state. PMID:9503692

Raymond, B; Taverner, D; Nandagopal, D; Mazumdar, J

1997-12-01

180

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING PARABOLIC FLIGHTS  

E-print Network

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were predominant during reduced gravity. For the mean heart rate, a non-monotonic relation was found, which can

181

Characterizing heart rate variability by scale-dependent Lyapunov exponent Jing Hu,1,2  

E-print Network

Characterizing heart rate variability by scale-dependent Lyapunov exponent Jing Hu,1,2 Jianbo Gao,1; accepted 18 May 2009; published online 30 June 2009 Previous studies on heart rate variability HRV using, since heart rate variability (HRV) may exhibit both nonlinear, and possibly chaotic, as well

Gao, Jianbo

182

Methodology for Multifractal Analysis of Heart Rate Variability: From LF/HF Ratio to Wavelet Leaders  

E-print Network

Methodology for Multifractal Analysis of Heart Rate Variability: From LF/HF Ratio to Wavelet introduction to the practical use of wavelet Leader based multifractal analysis to study heart rate variability to other standard characterizations of heart rate variability: (mono)fractal analysis, Hurst exponent

Gonçalves, Paulo

183

Brain Areas Controlling Heart Rate Variability in Tinnitus and Tinnitus-Related Distress  

E-print Network

Brain Areas Controlling Heart Rate Variability in Tinnitus and Tinnitus-Related Distress Sven in the central control of heart rate variability in tinnitus patients. Whereas the sympathovagal balance Heart Rate Variability in Tinnitus and Tinnitus-Related Distress. PLoS ONE 8(3): e59728. doi:10

O'Toole, Alice J.

184

Patients with uncomplicated coronary artery disease have reduced heart rate variability mainly affecting vagal tone  

Microsoft Academic Search

AIMTo investigate whether uncomplicated chronic coronary artery disease causes changes in heart rate variability and if so, whether the heart rate variability pattern is different from that described in patients with acute myocardial infarction.METHODSHeart rate variability was studied in 65 patients with angina who had no previous myocardial infarcts, no other diseases, and were on no drug that could influence

B Wennerblom; L Lurje; H Tygesen; R Vahisalo; ? Hjalmarson

2000-01-01

185

[Heart rate variability and physical exercise. Current status].  

PubMed

Heart rate variability (HRV) has long been used in risk stratification for sudden cardiac death and diabetic autonomic neuropathy. In recent years, both time and frequency domain indices of HRV also gained increasing interest in sports and training sciences. In these fields, HRV is currently used for the noninvasive assessment of autonomic changes associated with short-term and long-term endurance exercise training in both leisure sports activity and high-performance training. Furthermore, HRV is being investigated as a diagnostic marker of overreaching and overtraining.A large body of evidence shows that, in healthy subjects and cardiovascular patients of all ages (up to an age of 70 years), regular aerobic training usually results in a significant improvement of overall as well as instantaneous HRV. These changes, which are accompanied by significant reductions in heart rates both at rest and during submaximal exercise, reflect an increase in autonomic efferent activity and a shift in favor of enhanced vagal modulation of the cardiac rhythm. Regular aerobic training of moderate volume and intensity over a minimum period of 3 months seems to be necessary to ensure these effects, which might be associated with a prognostic benefit regarding overall mortality.At present, available data does not allow for final conclusions with respect to the usefulness of traditional HRV indices in assessing an individual's exercise performance and monitoring training load. The discrepant results published so far are due to several factors including insufficient study size and design, and different HRV methods. Large-sized and prospectively designed studies are necessary for clarification. It also remains to be seen, whether the traditional HRV indices prove useful in the diagnosis of overreaching and overtraining. Preliminary results, though promising, need to be confirmed in larger cohorts.A basic problem in HRV analysis is nonstationarity of the heart rate signal, which holds particularly true for exercise conditions. Whether, in these conditions, more robust nonlinear HRV methods offer a benefit has to be established in further work. PMID:17036185

Hottenrott, Kuno; Hoos, Olaf; Esperer, Hans Dieter

2006-09-01

186

Heart Rate Variability and Blood Pressure during Dynamic and Static Exercise at Similar Heart Rate Levels  

PubMed Central

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D2 was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity. PMID:24349546

Weippert, Matthias; Behrens, Kristin; Rieger, Annika; Stoll, Regina; Kreuzfeld, Steffi

2013-01-01

187

Estimating mental fatigue based on electroencephalogram and heart rate variability  

NASA Astrophysics Data System (ADS)

The effects of long term mental arithmetic task on psychology are investigated by subjective self-reporting measures and action performance test. Based on electroencephalogram (EEG) and heart rate variability (HRV), the impacts of prolonged cognitive activity on central nervous system and autonomic nervous system are observed and analyzed. Wavelet packet parameters of EEG and power spectral indices of HRV are combined to estimate the change of mental fatigue. Then wavelet packet parameters of EEG which change significantly are extracted as the features of brain activity in different mental fatigue state, support vector machine (SVM) algorithm is applied to differentiate two mental fatigue states. The experimental results show that long term mental arithmetic task induces the mental fatigue. The wavelet packet parameters of EEG and power spectral indices of HRV are strongly correlated with mental fatigue. The predominant activity of autonomic nervous system of subjects turns to the sympathetic activity from parasympathetic activity after the task. Moreover, the slow waves of EEG increase, the fast waves of EEG and the degree of disorder of brain decrease compared with the pre-task. The SVM algorithm can effectively differentiate two mental fatigue states, which achieves the maximum classification accuracy (91%). The SVM algorithm could be a promising tool for the evaluation of mental fatigue. Fatigue, especially mental fatigue, is a common phenomenon in modern life, is a persistent occupational hazard for professional. Mental fatigue is usually accompanied with a sense of weariness, reduced alertness, and reduced mental performance, which would lead the accidents in life, decrease productivity in workplace and harm the health. Therefore, the evaluation of mental fatigue is important for the occupational risk protection, productivity, and occupational health.

Zhang, Chong; Yu, Xiaolin

2010-01-01

188

Heart Rate Variability and Exercise in Aging Women  

PubMed Central

Abstract Background Our group has shown a positive dose-response in maximal cardiorespiratory exercise capacity (VO2max) and heart rate variability (HRV) to 6 months of exercise training but no improvement in VO2max for women ?60 years. Here, we examine the HRV response to exercise training in postmenopausal women younger and older than 60 years. Methods We examined 365 sedentary, overweight, hypertensive, postmenopausal women randomly assigned to sedentary control or exercise groups exercising at 50% (4?kcal/kg/week, [KKW]), 100% (8 KKW) and 150% (12 KKW) of the National Institutes of Health (NIH) Consensus Development Panel physical activity guidelines. Primary outcomes included time and frequency domain indices of HRV. Results Overall, our analysis demonstrated a significant improvement in parasympathetic tone (rMSSD and high frequency power) for both age strata at 8 KKW and 12 KKW. For rMSSD, the age-stratified responses were: control, <60 years, 0.20?ms, 95% confidence interval (CI)?2.40, 2.81; ?60 years, 0.07?ms, 95% CI ?3.64, 3.79; 4 KKW, <60 years, 3.67?ms, 95% CI 1.55, 5.79; ?60 years, 1.20?ms, 95% CI ?1.82, 4.22; 8-KKW, <60 years, 3.61?ms, 95% CI 0.88, 6.34; ?60 years, 5.75?ms, 95% CI 1.89, 9.61; and 12-KKW, <60 years, 5.07?ms, 95% CI 2.53, 7.60; ?60 years, 4.28?ms, 95% CI 0.42, 8.14. Conclusions VO2max and HRV are independent risk factors for cardiovascular disease (CVD) mortality. Despite no improvement in VO2max, parasympathetic indices of HRV increased in women ?60 years. This is clinically important, as HRV has important CVD risk and neurovisceral implications beyond cardiorespiratory function. PMID:21967166

Blair, Steven N.; Church, Timothy S.

2012-01-01

189

Population growth rates: issues and an application.  

PubMed Central

Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering. PMID:12396521

Godfray, H Charles J; Rees, Mark

2002-01-01

190

Heart rate variability and metabolic rate in healthy young adults with low birth weight  

PubMed Central

Objective: Low birth weight (LBW) is associated with obesity and a higher cardiovascular risk in adult life. Since autonomic dysfunction could be a pathophysiological factor for this association, we assessed the impact of LBW on cardiac autonomic activity and metabolic rate in young adulthood. We hypothesized that the autonomic tone could be coupled with the metabolic rate in subjects with LBW. Methods: Heart rate variability (HRV) from 24-hour Holter-electrocardiograms was measured in 15 healthy adults aged 20 to 30 years with LBW (<2500g at term) and 15 paired subjects with normal birth weight (NBW). The pairs were closely matched by gender, age, and body mass index. Resting energy expenditure was measured by indirect calorimetry and body composition by bioimpedance. Results: Global HRV parameters were significantly higher in the LBW group and a marked difference was observed in the long wave fluctuations of the frequency domain (very low frequency). These fluctuations were positively correlated with the resting energy expenditure per body weight in the LBW and negatively in the NBW group. Only in the LBW group HRV was closely related to body fat. Interpretation: This case-control study indicates that autonomous nervous function is not generally deteriorated in young adults with LBW and has a significant association with metabolic rate. Thus, it may be a determinant of the body weight regulation in this group. The higher cardiovascular risk in ageing individuals with LBW would therefore rather be a consequence of weight gain than of a primary autonomous nervous dysfunction. PMID:24224135

Weitz, Gunther; Bonnemeier, Hendrik; Sufke, Sven; Wellhoner, Peter; Lehnert, Hendrik; Dodt, Christoph

2013-01-01

191

Abstract Despite the exponential growth in heart rate variability (HRV) research, the reproducibility  

E-print Network

Abstract Despite the exponential growth in heart rate variability (HRV) research. The mean heart rate was more reproducible and could be more accu- rately estimated from very short segments be estimated accurately from short segments (Heart rate variability (HRV) Ã? Interbeat

192

Chemical evolution, stellar nucleosynthesis and a variable star formation rate  

NASA Astrophysics Data System (ADS)

The effects of a decreasing star formation rate (SFR) on the galactic abundances of elements produced in massive stars (M greater than or equal to 10 solar mass) is discussed. On the basis of a straightforward model of galactic evolution, a relation between the upper mass limit of type II supernovae (M/sub SN/) contributing to chemical evolution and the decline of the SFR (tau) is derived, when the oxygen abundance is determined only by massive stars. The additional requirement that all intermediate mass elements (Ne-Ti), which are also predominantly due to nucleosynthesis in massive stars, are produced in solar proportions leads to a unique value of M/sub SN/ and tau. The application of this method with abundance yields from Arnett (1978) and Woosley and Weaver (1986) resuults, however, in contradicting solutions: M/sub SN/ is approximately 45 solar mass, tau = infinity, and M/sub SN/ is approximately 15 solar mass, tau = 3 x 10 to the 9th power y. Thus, in order that this approach provide an effective probe of the SFR over the history of our galaxy it is essential that converging and more accurate predictions of the consequences of stellar and supernova nucleosynthesis will be forthcoming.

Olive, K. A.; Thielemann, F. K.; Truran, J. W.

1986-04-01

193

Who Uses Physician-Rating Websites? Differences in Sociodemographic Variables, Psychographic Variables, and Health Status of Users and Nonusers of Physician-Rating Websites  

PubMed Central

Background The number of physician-rating websites (PRWs) is rising rapidly, but usage is still poor. So far, there has been little discussion about what kind of variables influence usage of PRWs. Objective We focused on sociodemographic variables, psychographic variables, and health status of PRW users and nonusers. Methods An online survey of 1006 randomly selected German patients was conducted in September 2012. We analyzed the patients’ knowledge and use of online PRWs. We also analyzed the impact of sociodemographic variables (gender, age, and education), psychographic variables (eg, feelings toward the Internet, digital literacy), and health status on use or nonuse as well as the judgment of and behavior intentions toward PRWs. The survey instrument was based on existing literature and was guided by several research questions. Results A total of 29.3% (289/986) of the sample knew of a PRW and 26.1% (257/986) had already used a PRW. Younger people were more prone than older ones to use PRWs (t 967=2.27, P=.02). Women used them more than men (?2 1=9.4, P=.002), the more highly educated more than less educated people (?2 4=19.7, P=.001), and people with chronic diseases more than people without (?2 1=5.6, P=.02). No differences were found between users and nonusers in their daily private Internet use and in their use of the Internet for health-related information. Users had more positive feelings about the Internet and other Web-based applications in general (t 489=3.07, P=.002) than nonusers, and they had higher digital literacy (t 520=4.20, P<.001). Users ascribed higher usefulness to PRWs than nonusers (t 612=11.61, P<.001) and users trusted information on PRWs to a greater degree than nonusers (t 559=11.48, P<.001). Users were also more likely to rate a physician on a PRW in the future (t 367=7.63, P<.001) and to use a PRW in the future (t 619=15.01, P<.001). The results of 2 binary logistic regression analyses demonstrated that sociodemographic variables (gender, age, education) and health status alone did not predict whether persons were prone to use PRWs or not. Adding psychographic variables and information-seeking behavior variables to the binary logistic regression analyses led to a satisfying fit of the model and revealed that higher education, poorer health status, higher digital literacy (at the 10% level of significance), lower importance of family and pharmacist for health-related information, higher trust in information on PRWs, and higher appraisal of usefulness of PRWs served as significant predictors for usage of PRWs. Conclusions Sociodemographic variables alone do not sufficiently predict use or nonuse of PRWs; specific psychographic variables and health status need to be taken into account. The results can help designers of PRWs to better tailor their product to specific target groups, which may increase use of PRWs in the future. PMID:24686918

Bidmon, Sonja; Rottl, Johanna

2014-01-01

194

An Examination of the Relationship Between Resting Heart Rate Variability and Heart Rate Reactivity to a Mental Arithmetic Stressor  

Microsoft Academic Search

Resting heart rate variability can be an index of sympathetic or parasympathetic dominance, according to the frequency of the variability studied. Sympathetic dominance of this system has been linked to increased risk of cardiovascular disease (CVD). Similarly, rapid and dramatic increases in heart rate reactivity to a stressor task have also been suggested as indicating increased risk of CVD via

Christopher F. Sharpley; Peter Kamen; Maria Galatsis; Rod Heppel; Charles Veivers; Kim Claus

2000-01-01

195

Bouts of Responding: The Relation between Bout Rate and the Rate of Variable-Interval Reinforcement  

ERIC Educational Resources Information Center

By nose poking a lighted key, rats obtained food pellets on either a variable- interval schedule of reinforcement or a schedule that required an average of four additional responses after the end of the variable-interval component (a tandem variable-interval variable-ratio 4 schedule). With both schedule types, the mean variable interval was…

Shull, Richard L.; Grimes, Julie A.; Bennett, J. Adam

2004-01-01

196

Heart Rate Variability Analysis in the Assessment of Autonomic Function in Heart Failure.  

National Technical Information Service (NTIS)

Heart rate is not static but rather changes continuously in response to physical and mental demands. In fact, an invariant heart rate is associated with disease processes such as heart failure. Heart rate variability analysis is a noninvasive technique us...

M. J. De Jong, D. C. Randall

2004-01-01

197

SMOOTH VARIABLE STRUCTURE FILTERING: THEORY AND APPLICATIONS  

Microsoft Academic Search

Filtering strategies play an important role in estimation theory, and are used to extract knowledge of the true states typically from noisy measurements or observations made of the system. The name ‘filter’ is appropriate since it removes unwanted noise from the signal. In 2007, the smooth variable structure filter (SVSF) was introduced. This filter is based on the sliding mode

Stephen Andrew Gadsden

2011-01-01

198

Variable neighborhood search: Principles and applications  

Microsoft Academic Search

Systematic change of neighborhood within a possibly randomized local search algorithm yields a simple and effective metaheuristic for combinatorial and global optimization, called variable neighborhood search (VNS). We present a basic scheme for this purpose, which can easily be implemented using any local search algorithm as a subroutine. Its effectiveness is illustrated by solving several classical combinatorial or global optimization

Pierre Hansen; Nenad Mladenovic

2001-01-01

199

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2010 CFR

...rate of Bank's commercial paper. Variations in the value of this interest...payments based on the value of the 30-day commercial paper rate on each...be based on the values, as of the issue...of the 90-day commercial paper rate...

2010-04-01

200

Spectral analysis of heart rate variability in the sepsis syndrome  

Microsoft Academic Search

Sympathetic and parasympathetic activity was evaluated on 39 occasions in 17 patients with the sepsis syndrome, by measurement of the variation in resting heart rate using frequency spectrum analysis. Heart rate was recorded by electrocardiography and respiratory rate by impedance plethysmography. The sepsis syndrome was established on the basis of established clinical and physiological criteria. Subjects were studied, whenever possible,

Christopher S. Garrard; Dimitrios A. Kontoyannis; Massimo Piepoli

1993-01-01

201

Variable Frame Rate for Low Power Mobile Sign Language Communication  

E-print Network

of conversational sign lan- guage allow us to save power and bits: namely, lower frame rates are possible when one the frame rate during turn-taking is a good way to save power without sacrificing intelligibility to be even more quickly depleted. One way to save battery life is to encode videos at a lower frame rate (i

Anderson, Richard

202

Increased network efficiency for variable rate video streams in an Integrated Services Packet Network environment  

E-print Network

with a way to reserve a fixed quantity of network resources for their exclusive use. Most video encoders, however, are variable rate. This research describes a mechanism by which variable bit-rate, real-time video streams can be sent over a fixed rate...

Schroeder, Charles Grant

2012-06-07

203

Stress Classification by Separation of Respiratory Modulations in Heart Rate Variability using Orthogonal Subspace Projection*  

E-print Network

Stress Classification by Separation of Respiratory Modulations in Heart Rate Variability using of respiration on the heart rate is a phenomenon known as respiratory sinus arrhythmia. However, effects of respiration are often ignored in studies of heart rate variability. In this paper, we take respiratory

204

Reliability and Accuracy of Heart Rate Variability Metrics Versus ECG Segment Duration  

E-print Network

Reliability and Accuracy of Heart Rate Variability Metrics Versus ECG Segment Duration J. McNames1, Oregon Health & Science University, Portland, OR, USA Abstract-- Heart rate variability (HRV) has been used in many studies to assess the effects of autonomic regulation on the heart rate. A 1996 task force

205

Nonlinear Heart Rate Variability in a Healthy Population: Influence of Age  

E-print Network

Nonlinear Heart Rate Variability in a Healthy Population: Influence of Age S Vandeput1 , B Universiteit Leuven, Belgium Abstract Heart rate variability (HRV) measurements are used as markers of autonomic modulation of heart rate. Numerical noise titration was applied to a large healthy population

206

Heart rate variability in preterm neonates with and without abnormal cardiorespiratory events.  

E-print Network

Heart rate variability in preterm neonates with and without abnormal cardiorespiratory events The heart rate variability (HRV) of preterm neonates undergoing a polysomnography is ana- lyzed in relation experience abnormal cardiorespiratory events, based only on the heart rate recordings during periods without

207

Wrapper subset evaluation facilitates the automated detection of diabetes from heart rate variability measures  

E-print Network

Wrapper subset evaluation facilitates the automated detection of diabetes from heart rate heart rate variability measures. These data are well suited to the diagnosis of cardiac dysfunction that the detection of diabetes is feasible from heart rate variability measures. D. J. Cornforth, H. F. Jelinek, M. C

Teich, Malvin C.

208

Multifractal Analysis of Fetal Heart Rate Variability in Fetuses with and without Severe  

E-print Network

Multifractal Analysis of Fetal Heart Rate Variability in Fetuses with and without Severe Acidosis multifractal analysis of fetal heart rate (FHR) variability in fetuses with and without acidosis during labor and nonacidotic fetuses, independently from FHR pattern. KEYWORDS: Acidosis, fetal heart rate, labor, multifractal

Abry, Patrice

209

Large deviations estimates for the multiscale analysis of heart rate variability$,$$  

E-print Network

Large deviations estimates for the multiscale analysis of heart rate variability$,$$ Patrick physiological factors impacting the heart rate variability. Notwithstanding these considerable progresses, multi the relevance of this approach, on both theoretical objects and on human heart rate signals from the Physionet

Gonçalves, Paulo

210

Accurate R Peak Detection and Advanced Preprocessing of Normal ECG for Heart Rate Variability Analysis  

E-print Network

Accurate R Peak Detection and Advanced Preprocessing of Normal ECG for Heart Rate Variability, The Netherlands Abstract Heart rate variability (HRV) analysis is well-known to give information about the autonomic heart rate modula- tion mechanism. In order to avoid erroneous conclusions, it is of great

211

In vivo cardiac phase response curve elucidates human respiratory heart rate variability  

E-print Network

In vivo cardiac phase response curve elucidates human respiratory heart rate variability Published-related variation of the heart rate by S. Hales in 1733 and its first registration by C. Ludwig in 1847 [1], cardio of heart rate variability has become important in many medical fields as a diagnostically

Pikovsky, Arkady

212

Large deviations estimates for the multiscale analysis of heart rate variability$,$$  

E-print Network

Large deviations estimates for the multiscale analysis of heart rate variability$,$$ Patrick to characterize relevant physiological factors impacting the heart rate variability. Notwithstanding. In this article, we illustrate the relevance of this approach, on both theoretical objects and on human heart rate

Boyer, Edmond

213

1996 International Conference on Parallel Processing Analysis of Heart Rate Variability on a Massively Parallel  

E-print Network

1996 International Conference on Parallel Processing Analysis of Heart Rate Variability. The algorithm is used to compute the Kz entropy and correlation di- mension of experimental heart rate data (an be used as a measure of the heart rate variability and the level of chaos present in

Bhandarkar, Suchendra "Suchi" M.

214

Analysis of Heart Rate Variability Using Time-Varying Filtering of Heart Transplanted Patients  

E-print Network

Analysis of Heart Rate Variability Using Time-Varying Filtering of Heart Transplanted Patients the heart rate variability (HRV), obtained by using the time-varying integral pulse frequency modulation of the filtered modulation of the heart rate due to respiration is compared to the date of transplantation taking

Paris-Sud XI, Université de

215

Heart rate variability, trait anxiety, and perceived stress among physically fit men and women  

Microsoft Academic Search

Background: It is unclear from prior reports whether the relationships between self-ratings of anxiety or emotional stress and parasympathetic nervous system components of heart rate variability are independent of personality and cardiorespiratory fitness. We examined those relationships in a clinical setting prior to a standardized exercise test. Methods and results: Heart rate variability (HRV) was measured during 5 min of

Rod K. Dishman; Yoshio Nakamura; Melissa E. Garcia; Ray W. Thompson; Andrea L. Dunn; Steven N. Blair

2000-01-01

216

Tax Rate Variability and Public Spending as Sources of Indeterminacy  

E-print Network

of public spending, financed by labor income and consump- tion taxation, on the emergence of indeterminacy. We find that what is relevant for indeterminacy is the variability of the distortion in- troduced. Keywords: Indeterminacy, public spending, taxation, segmented asset markets. JEL Classification: E32, E63

Boyer, Edmond

217

Variable Speed Pumping: A Guide to Successful Applications; Executive Summary  

SciTech Connect

This document is the result of a collaboration between the Hydraulic Institute, Europump, and the U.S. DOE Industrial Technologies Program, and describes the cost and energy savings potential of pumping applications with variable duty requirements.

Not Available

2004-05-01

218

Discrete variable structure control and its application to ship autopilot  

Microsoft Academic Search

Purpose – In order to improve performance robustness of control systems, the discrete variable structure control (VSC) design for uncertain systems and its application to a ship autopilot are to be discussed in this paper. Design\\/methodology\\/approach – Discrete-time variable structure control (DVSC) becomes worth investigating and various DVSC methods have been suggested by many papers. The approach that used the

Huaishu Li; Lizhong Song; Yanhui Lai

2008-01-01

219

Playing a violent television game affects heart rate variability  

Microsoft Academic Search

Objective: To investigate how playing a violent\\/nonviolent television game during the evening affects sympathetic and parasympathetic reactions during and after playing as well as sleep quality during the night after playing. Subjects and Methods: In total, 19 boys, 12-15 years of age, played television games on two occasions in their homes and participated once without gaming. Heart rate, heart rate

Malena Ivarsson; Martin Anderson; Torbjörn Åkerstedt; Frank Lindblad

2009-01-01

220

26 CFR 1.1275-5 - Variable rate debt instruments.  

...restrictions on the maximum stated interest rate (cap), a restriction or restrictions on the...a qualified floating rate— (i) A cap, floor, or governor that is fixed throughout...term of the debt instrument; (ii) A cap or similar restriction that is not...

2014-04-01

221

Higher heart rate and reduced heart rate variability persist during sleep in chronic fatigue syndrome: A population-based study  

Microsoft Academic Search

Autonomic nervous system (ANS) dysfunction has been suggested in patients with chronic fatigue syndrome (CFS). In this study, we sought to determine whether increased heart rate (HR) and reduced heart rate variability (HRV) parameters observed in CFS patients during wakefulness persist during sleep. To this end, we compared heart rate (HR) and HRV as indicators of ANS function in CFS

Roumiana S. Boneva; Michael J. Decker; Elizabeth M. Maloney; Jin-Mann Lin; James F. Jones; Helgi G. Helgason; Christine M. Heim; David B. Rye; William C. Reeves

2007-01-01

222

Understanding garnet variability: Application of geometallurgy to diamonds and exploration  

NASA Astrophysics Data System (ADS)

Peridotitic and eclogitic garnets are a fundamental component in understanding mantle petrology, diamond petrogenesis, and the ascent of mantle materials in kimberlites. They are also critical in exploration programs, as the presence of mantle garnets at the earth's surface provides an indication of dispersion from a deeply derived magmatic carrier. The composition of these garnets further is used as an indicator of diamond prospectivity, on the basis of comparison with garnet compositions known to be in some degree of equilibrium with diamonds. For mantle xenoliths and kimberlites, optical microscopy, electron microprobe analysis (EPMA), and scanning electron microscopy (SEM) are the main tools used for understanding key mineralogical and textural variability relationships. Mineralogy and texture reflect diamond genesis, metasomatic alteration, fluid migration and manifestation, volcanological processes, peridotite disaggregation, and other manifestations of mantle processes that are observable, describable, and applicable in exploration and mining. Mineralogy and texture studies lead to further questions that are better addressed by higher resolution chemical analysis of isotopes and rare earth elements, or luminescence. Understanding mineralogical and textural variability is the primary geological input for geometallurgy (geomet), the field integrating the earth sciences with the extractive industries. The framework for geomet encompasses geology, mineralogy, deposit modeling and extraction methods for the optimum value return of resources, and it relies on the fact that the mineralogy and texture of rocks influence subsequent interpretation and downstream applications. Developments in this area have been made possible by the new generation of high-speed SEM-based quantitative mineralogical instruments, enabling the statistical assessment of thousands of grains or particles, or samples, and their application to models for exploration, ore deposits, or geomet. For diamonds, this means identification and quantification of large mineralogical and textural data sets, and gives the geologist more involvement in model development. In this study, peridotitic and eclogitic garnets were examined in situ and as xenocrysts to gain understanding of the mineralogical and textural variability of the grains using SEM-based quantitative mineralogy. For concentrate garnets, the new technology presented here is the development of mineral definitions that reflect SEM counts and correlate with EPMA data. Internal compositional variability is mapped across individual grains as compared to EPMA spot analysis; designations of G10-G9 compositions, for example, are more complex when viewed in terms of individual internal grain compositional variability. The new mineral lists based on percentages of Ca-Cr count rates are compared to unknown garnets from exploration samples, and digitally categorized into bins reflecting potential diamond prospectivity or secondary alteration, as desired. The high analysis rate (approx. 150 determinations/second) means the SEM-based technique can be faster and produce more statistical information for the geologist who is making the model assessment in the field. Combined with new nontoxic mineral separation methodology in the field and software on the geologist's laptop, a great deal of interpretation can be accommodated in the field, at a reduced cost for shipping large volumes of samples to a central laboratory. Geomet for diamonds provides the mechanism for thinking of the entirety of a project, and using the geological and mineralogical information to predict process implications.

Hoal, K. O.; Appleby, S. K.; Stammer, J. G.

2009-05-01

223

Consistency and variability among college students in rating their teachers and courses: A review and analysis  

Microsoft Academic Search

As indicated by the reliability of individual ratings, college students are only moderately consistent in rating their teachers and courses, although these modest interrater associations do produce substantial reliabilities for composite ratings when the ratings of at least 20 to 25 students in a class are averaged together. The patterning and correlates of variability of student ratings within classes are

Kenneth A. Feldman

1977-01-01

224

Dimensional analysis of heart rate variability in heart transplant recipients  

SciTech Connect

We discuss periodicities in the heart rate in normal and transplanted hearts. We then consider the possibility of dimensional analysis of these periodicities in transplanted hearts and problems associated with the record.

Zbilut, J.P.; Mayer-Kress, G.; Geist, K.

1987-01-01

225

Application of variable metric methods to structural synthesis  

NASA Technical Reports Server (NTRS)

Powell (1977, 1978), Biggs (1972, 1975), and Han (1976, 1977) have developed a class of variable metric methods which create an explicit, quadratic, subproblem which is to be solved for finding a search direction for design improvement. A one-dimensional search is then performed. The present paper has the objective to present this variable metric approach in the context of structural synthesis. The variable metric algorithm is modified for application to the structural synthesis problem. The application of the new procedure is illustrated with the aid of examples, taking into account a 10-bar planar truss, a 17-bar planar tower, and a cantilever beam.

Vanderplaats, G. N.; Sugimoto, H.

1985-01-01

226

A comparison between heart rate and heart rate variability as indicators of cardiac health and fitness  

PubMed Central

Quantification of cardiac autonomic activity and control via heart rate (HR) and heart rate variability (HRV) is known to provide prognostic information in clinical populations. Issues with regard to standardization and interpretation of HRV data make the use of the more easily accessible HR on its own as an indicator of autonomic cardiac control very appealing. The aim of this study was to investigate the strength of associations between an important cardio vascular health metric such as VO2max and the following: HR, HRV indicators, and HR normalized HRV indicators. A cross sectional descriptive study was done including 145 healthy volunteers aged between 18 and 22 years. HRV was quantified by time domain, frequency domain and Poincaré plot analysis. Indirect VO2max was determined using the Multistage Coopers test. The Pearson correlation coefficient was calculated to quantify the strength of the associations. Both simple linear and multiple stepwise regressions were performed to be able to discriminate between the role of the individual indicators as well as their combined association with VO2max. Only HR, RR interval, and pNN50 showed significant (p < 0.01, p < 0.01, and p = 0.03) correlations with VO2max. Stepwise multiple regression indicated that, when combining all HRV indicators the most important predictor of cardio vascular fitness as represented by VO2max, is HR. HR explains 17% of the variation, while the inclusion of HF (high frequency HRV indicator) added only an additional 3.1% to the coefficient of determination. Results also showed when testing the normalized indicators, HR explained of the largest percentage of the changes in VO2max (16.5%). Thus, HR on its own is the most important predictor of changes in an important cardiac health metric such as VO2max. These results may indicate that during investigation of exercise ability (VO2max) phenomena, quantification of HRV may not add significant value. PMID:24312058

Grant, Catharina C.; Murray, Carien; Janse van Rensburg, Dina C.; Fletcher, Lizelle

2013-01-01

227

A comparison between heart rate and heart rate variability as indicators of cardiac health and fitness.  

PubMed

Quantification of cardiac autonomic activity and control via heart rate (HR) and heart rate variability (HRV) is known to provide prognostic information in clinical populations. Issues with regard to standardization and interpretation of HRV data make the use of the more easily accessible HR on its own as an indicator of autonomic cardiac control very appealing. The aim of this study was to investigate the strength of associations between an important cardio vascular health metric such as VO2max and the following: HR, HRV indicators, and HR normalized HRV indicators. A cross sectional descriptive study was done including 145 healthy volunteers aged between 18 and 22 years. HRV was quantified by time domain, frequency domain and Poincaré plot analysis. Indirect VO2max was determined using the Multistage Coopers test. The Pearson correlation coefficient was calculated to quantify the strength of the associations. Both simple linear and multiple stepwise regressions were performed to be able to discriminate between the role of the individual indicators as well as their combined association with VO2max. Only HR, RR interval, and pNN50 showed significant (p < 0.01, p < 0.01, and p = 0.03) correlations with VO2max. Stepwise multiple regression indicated that, when combining all HRV indicators the most important predictor of cardio vascular fitness as represented by VO2max, is HR. HR explains 17% of the variation, while the inclusion of HF (high frequency HRV indicator) added only an additional 3.1% to the coefficient of determination. Results also showed when testing the normalized indicators, HR explained of the largest percentage of the changes in VO2max (16.5%). Thus, HR on its own is the most important predictor of changes in an important cardiac health metric such as VO2max. These results may indicate that during investigation of exercise ability (VO2max) phenomena, quantification of HRV may not add significant value. PMID:24312058

Grant, Catharina C; Murray, Carien; Janse van Rensburg, Dina C; Fletcher, Lizelle

2013-01-01

228

Review and classification of variability analysis techniques with clinical applications  

PubMed Central

Analysis of patterns of variation of time-series, termed variability analysis, represents a rapidly evolving discipline with increasing applications in different fields of science. In medicine and in particular critical care, efforts have focussed on evaluating the clinical utility of variability. However, the growth and complexity of techniques applicable to this field have made interpretation and understanding of variability more challenging. Our objective is to provide an updated review of variability analysis techniques suitable for clinical applications. We review more than 70 variability techniques, providing for each technique a brief description of the underlying theory and assumptions, together with a summary of clinical applications. We propose a revised classification for the domains of variability techniques, which include statistical, geometric, energetic, informational, and invariant. We discuss the process of calculation, often necessitating a mathematical transform of the time-series. Our aims are to summarize a broad literature, promote a shared vocabulary that would improve the exchange of ideas, and the analyses of the results between different studies. We conclude with challenges for the evolving science of variability analysis. PMID:21985357

2011-01-01

229

Biophysical characterization of the underappreciated and important relationship between heart rate variability and heart rate.  

PubMed

Heart rate (HR) variability (HRV; beat-to-beat changes in the R-wave to R-wave interval) has attracted considerable attention during the past 30+ years (PubMed currently lists >17 000 publications). Clinically, a decrease in HRV is correlated to higher morbidity and mortality in diverse conditions, from heart disease to fetal distress. It is usually attributed to fluctuation in cardiac autonomic nerve activity. We calculated HRV parameters from a variety of cardiac preparations (including humans, living animals, Langendorff-perfused heart, and single sinoatrial nodal cell) in diverse species, combining this with data from previously published articles. We show that regardless of conditions, there is a universal exponential decay-like relationship between HRV and HR. Using 2 biophysical models, we develop a theory for this and confirm that HRV is primarily dependent on HR and cannot be used in any simple way to assess autonomic nerve activity to the heart. We suggest that the correlation between a change in HRV and altered morbidity and mortality is substantially attributable to the concurrent change in HR. This calls for re-evaluation of the findings from many articles that have not adjusted properly or at all for HR differences when comparing HRV in multiple circumstances. PMID:25225208

Monfredi, Oliver; Lyashkov, Alexey E; Johnsen, Anne-Berit; Inada, Shin; Schneider, Heiko; Wang, Ruoxi; Nirmalan, Mahesh; Wisloff, Ulrik; Maltsev, Victor A; Lakatta, Edward G; Zhang, Henggui; Boyett, Mark R

2014-12-01

230

Separation of heart rate variability components of the autonomic nervous system by utilizing principal dynamic modes.  

PubMed

This work introduces a modified Principal Dynamic Modes (PDM) methodology using eigenvalue/eigenvector analysis to separate individual components of the sympathetic and parasympathetic nervous contributions to heart rate variability. We have modified the PDM technique to be used with even a single output signal of heart rate variability data, whereas the original PDMs required both input and output data. This method specifically accounts for the inherent nonlinear dynamics of heart rate control, which the current method of power spectrum density (PSD) is unable to do. Propranolol and atropine were administered to normal human volunteers intravenously to inhibit the sympathetic and parasympathetic activities, respectively. With separate applications of the respective drugs, we found a significant decrease in the amplitude of the waveforms that correspond to each nervous activity. Furthermore, we observed near complete elimination of these dynamics when both drugs were given to the subjects. Comparison of our method to the conventional low/high frequency ratio of PSD shows that PDM methodology provides much more accurate assessment of the autonomic nervous balance by separation of individual components of the autonomic nervous activities. The PDM methodology is expected to have an added benefit that diagnosis and prognostication of a patient's health can be determined simply via a non-invasive electrocardiogram. PMID:16519864

Chon, K H; Zhong, Y; Wang, H; Ju, K; Jan, K M

2006-04-01

231

Heart rate variability during respiratory pauses in puppies and dogs.  

PubMed

We studied the time course and change in heart rate during respiratory pauses in puppies (3-4 wk) and young adult dogs. We measured ventilation and ventilatory pattern using barometric plethysmography and recorded the respiratory rate (RR) interval using a pre-processor with an accuracy of 0.2 ms. During tidal breathing, the fluctuations in RR interval were an order of magnitude smaller in the puppy than in the dog. During respiratory pauses in dogs, the RR interval increased sharply, stabilized around the level of expiration of previous breaths, and dropped immediately with the subsequent inspiratory effort. The time course of the change in heart rate was different in the puppy: there was a gradual increase in the RR interval during the entire course of the pause and the maximum RR interval reached was substantially higher than during expiration of previous breaths. Our results suggest that 1) the change in heart rate at the outset of respiratory pauses is too fast to be related to blood gas changes in both puppies and dogs and 2) the mechanisms responsible for the vagal gating of heart rate during tidal breathing and during respiratory pauses are not well developed in early life in the puppy. PMID:3658551

Haddad, G G; Jeng, H J; Lai, T L

1987-09-01

232

26 CFR 26.2641-1 - Applicable rate of tax.  

Code of Federal Regulations, 2010 CFR

... Applicable rate of tax. The rate of tax applicable to any GST (applicable rate) is determined by multiplying the maximum Federal estate tax rate in effect at the time of the GST by the inclusion ratio (as defined in § 26.2642-1)....

2010-04-01

233

Heart rate variability as determinism with jump stochastic parameters.  

PubMed

We use measured heart rate information (RR intervals) to develop a one-dimensional nonlinear map that describes short term deterministic behavior in the data. Our study suggests that there is a stochastic parameter with persistence which causes the heart rate and rhythm system to wander about a bifurcation point. We propose a modified circle map with a jump process noise term as a model which can qualitatively capture such this behavior of low dimensional transient determinism with occasional (stochastically defined) jumps from one deterministic system to another within a one parameter family of deterministic systems. PMID:23906210

Zheng, Jiongxuan; Skufca, Joseph D; Bollt, Erik M

2013-08-01

234

Regression Discontinuity Designs with Multiple Rating-Score Variables  

ERIC Educational Resources Information Center

In the absence of a randomized control trial, regression discontinuity (RD) designs can produce plausible estimates of the treatment effect on an outcome for individuals near a cutoff score. In the standard RD design, individuals with rating scores higher than some exogenously determined cutoff score are assigned to one treatment condition; those…

Reardon, Sean F.; Robinson, Joseph P.

2012-01-01

235

Erosion rate variability in steady state landscapes: sources  

E-print Network

runoff from adjacent basin · Decreased runoff on the scavenged side · Effects erosion rates over sub landscape structure #12;Drainage area capture: positive feedback for migration · Migrating divide captures to ­ slope failures, temporary sediment storage, and propagating knickpoints · Drainage capture: positive

Paola, Chris

236

Multiport solid-state imager characterization at variable pixel rates  

Microsoft Academic Search

The imaging performance of an 8-port Full Frame Transfer Charge Coupled Device (FFT CCD) as a function of several parameters including pixel clock rate is presented. The device, model CCD-13, manufactured by English Electric Valve (EEV), is a 512 X 512 pixel array designed with four individual programmable bidirectional serial registers and eight output amplifiers permitting simultaneous readout of eight

George J. Yates; Kevin L. Albright; Bojan T. Turko

1993-01-01

237

Variable-clock-rate A/D converter  

NASA Technical Reports Server (NTRS)

Analog-to-digital (A/D) converter operates at two different rates (slow and fast) so that low amplitude noise is reduced without loss of transient response. During tracking, when sensitivity is important, slow clock reduces noise. In search mode, when signal may change rapidly, fast clock ensures rapid response.

Lipoma, P. C.

1980-01-01

238

Variability in Nest Survival Rates and Implications to Nesting Studies  

NSDL National Science Digital Library

The Northern Prairie Wildlife Research Center (NPWRC) has posted several new biological resources on the Web. This resource, by A.T. Klett and Douglas H. Johnson, is based on a 1982 publication in the Auk [99:77-87] and examines nests of Mallard (Anas platyrhynchos) and Blue-winged Teal (A. discors) to evaluate potential biases in hatch-rate estimates. All resources may be downloaded as .zip files.

Johnson, Douglas H.; Klett, A. T.

1982-01-01

239

The effect of depression on heart rate variability during pregnancy  

Microsoft Academic Search

Depression during pregnancy has been associated with a number of adverse outcomes, but the underlying physiological mechanisms\\u000a involved remain unclear. The purpose of this study was to examine the effects of maternal depression during pregnancy on the\\u000a autonomic modulation of heart rate, in a naturalistic setting. Eighty-one pregnant women were studied between 25 and 31 weeks\\u000a of gestation and were identified

Alison K. Shea; Markad V. Kamath; Alison Fleming; David L. Streiner; Keith Redmond; Meir Steiner

2008-01-01

240

Spatial variability in the degradation rate of isoproturon in soil  

Microsoft Academic Search

Thirty samples of soil were taken at 50-m intersections on a grid pattern over an area of 250×200 m within a single field with nominally uniform soil characteristics. Incubations of isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) under standard conditions (15oC; ?33 kPa soil water potential) indicated considerable variation in degradation rate of the herbicide, with the time to 50% loss (DT50) varying from 6.5

A. Walker; M. Jurado-Exposito; G. D. Bending; V. J. R. Smith

2001-01-01

241

Effects of Smoking Cessation on Heart Rate Variability Among Long-Term Male Smokers  

E-print Network

Effects of Smoking Cessation on Heart Rate Variability Among Long-Term Male Smokers Christopher B Cigarette smoking has been shown to adverse- ly affect heart rate variability (HRV), suggesting dysregula- tion of cardiac autonomic function. Conversely, smoking cessation is posited to improve cardiac

Meston, Cindy

242

Development of a Matlab Software for Analysis of Heart Rate Variability  

E-print Network

of the nervous system increases the heart rhythm, resulting in shorter beat intervals. The parasympathetic branchDevelopment of a Matlab Software for Analysis of Heart Rate Variability João Luiz Azevedo de, Brazil, 70510-900 e-mail: adson@unb.br Abstract--The analysis of heart rate variability (HRV) signals

Carvalho, João Luiz

243

THE INFLUENCE OF TRAINING ON HEART RATE VARIABILITY IN HEALTHY OLDER ADULTS  

Microsoft Academic Search

The effect of one-year physical training on heart rate variability in older adults was evaluated in 14 healthy men (age > 55 year). Measures of heart rate variability were obtained in both time and frequency domain. Ten- minute ECG recordings were made in supine position and in standing position. A progressive climbing exertion test till exhaustion was performed to estimate

B. Seps; F. Beckers; D. Ramaekers; A. E. Aubert

2001-01-01

244

Traffic Models and Admission Control for Variable Bit Rate Continuous Media Transmission with Deterministic Service \\Lambda  

E-print Network

descriptions that give rise to efficient call admission algorithms that provide high resource utilization. Unfortunately these algorithms are unable to generate high resource utilization when offered variable bit rateTraffic Models and Admission Control for Variable Bit Rate Continuous Media Transmission

Massachusetts at Amherst, University of

245

From pain to stress evaluation using Heart Rate Variability analysis: Development of an evaluation platform  

Microsoft Academic Search

Heart Rate Variability analysis has been shown in several studies to measure the Autonomic Nervous System tone, which is strongly influenced by pain, stress or anxiety. We have previously described and developed an Analgesia\\/Nociception Index for pain measurement during surgical procedure. This index based on a heart rate variability analysis can be considered as a vagal tone index and used

J. De jonckheere; R. Logier; R. Jounwaz; R. Vidal; M. Jeanne

2010-01-01

246

Heart rate variability: sleep stage, time of night, and arousal influences  

Microsoft Academic Search

Spectral analysis was used to assess heart rate variability in consecutive 5-min epochs during the night in 12 normal adults. Simultaneous time coding of EEG and digitized EKG allowed examination of heart rate variability as a function of sleep stage, time of night and presence of EEG arousal. The results replicated previous studies in showing increases in high frequency components

M. H. Bonnet; D. L. Arand

1997-01-01

247

Decreased heart rate variability in survivors of sudden cardiac death not associated with coronary artery disease  

Microsoft Academic Search

BACKGROUND--Although heart rate variability has already been studied in survivors of sudden cardiac death secondary to coronary artery disease, an assessment of heart rate variability in survivors of sudden cardiac death not associated with coronary artery disease has not been made. METHODS--10 patients with aborted sudden cardiac death not associated with coronary artery disease (seven patients with primary ventricular fibrillation

J Singh; M. H. Anderson; D. Katritsis; J. Sneddon; D. J. Statters; M. Malik; A. J. Camm

1994-01-01

248

Heart rate variability in rats with chronic hypoxic pulmonary hypertension  

Microsoft Academic Search

The precise role of pulmonary hypertension as a possible factor inducing a decrease in heart rate variability is poorly known. Spectral analysis of heart rate variability (HRV) was carried out in 21 Wistar rats before and after exposure to normoxia (N=10) or to 3 weeks of hypobaric hypoxia inducing chronic pulmonary hypertension and right ventricular hypertrophy (N=11). Continuous ECG was recorded

L. Fauchier; A. Melin; V. Eder; D. Antier; P. Bonnet

2006-01-01

249

Physical activity is a major contributor to the ultra low frequency components of heart rate variability  

Microsoft Academic Search

OBJECTIVETo investigate the link between changes in level of physical activity and the pattern of heart rate variability during long term ambulatory monitoring.DESIGNHeart rate variability was measured simultaneously with a quantitative indicator of muscle activity by electromyography (EMG) in five men and five women while they did activities typical of daily life or while they rested for 2–3 hours. Spectral

J M Serrador; H C Finlayson; R L Hughson

1999-01-01

250

Visual discrimination learning in dwarf goats and associated changes in heart rate and heart rate variability.  

PubMed

We studied visual discrimination learning in a group of Nigerian dwarf goats using a computer-based learning device which was integrated in the animals' home pen. We conducted three consecutive learning tasks (T1, T2 and T3), each of which lasted for 13 days. In each task, a different set of four visual stimuli was presented on a computer screen in a four-choice design. Predefined sequences of stimulus combinations were presented in a pseudorandom order. Animals were rewarded with drinking water when they chose the positive stimulus by pressing a button next to it. Noninvasive measurements of goats' heartbeat intervals were carried out on the first and the last 2 days of each learning task. We analysed heart rate (HR) and heart rate variability (HRV) of resting animals to study sustained physiological effects related to general learning challenge rather than acute excitement during an actual learning session. The number of trials to reach the learning criterion was 1000 in T1, when visual stimuli were presented to the goats for the first time, but decreased to 210 in T2 and 240 in T3, respectively. A stable plateau of correct choices between 70% and 80% was reached on Day 10 in T1, on Day 8 in T2 and on Day 6 in T3. We found a significant influence of the task and of the interaction between task and day on learning success. Whereas HR increased throughout T1, this relationship was inverted in T2 and T3, indicating different effects on the HR depending on how familiar goats were with the learning task. We found a significant influence of the task and the interaction between task and time within the task on HRV parameters, indicating changes of vagal activity at the heart. The results suggest that changes in HR related to learning were predominantly caused by a withdrawal of vagal activity at the heart. With regard to nonlinear processes in heartbeat regulation, increased deterministic shares of HRV indicated that the animals did not really relax until the end of T3. Comparing changes of HR and HRV in T3 and in a subsequent postexperiment (PE), we assume a positive effect of such cognitive challenges once the task had been learned by the animals. PMID:15327907

Langbein, Jan; Nürnberg, G; Manteuffel, G

2004-09-30

251

VARIABLE FIRING RATE OIL BURNER USING PULSE FUEL FLOW CONTROL.  

SciTech Connect

The residential oil burner market is currently dominated by the pressure-atomized retention head burner, which has an excellent reputation for reliability and efficiency. In this burner, oil is delivered to a fuel nozzle at pressures from 100 to 150 psi. In addition, to atomizing the fuel, the small, carefully controlled size of the nozzle exit orifice serves to control the burner firing rate. Burners of this type are currently available at firing rates of more than 0.5 gallons-per-hour (70,000 Btu/hr). Nozzles have been made for lower firing rates, but experience has shown that such nozzles suffer rapid fouling of the necessarily small passages, leading to bad spray patterns and poor combustion performance. Also, traditionally burners and the nozzles are oversized to exceed the maximum demand. Typically, this is figured as follows. The heating load of the house on the coldest day for the location is considered to define the maximum heat load. The contractor or installer adds to this to provide a safety margin and for future expansion of the house. If the unit is a boiler that provides domestic hot water through the use of a tankless heating coil, the burner capacity is further increased. On the contrary, for a majority of the time, the heating system is satisfying a much smaller load, as only rarely do all these demands add up. Consequently, the average output of the heating system has to be much less than the design capacity and this is accomplished by start and stop cycling operation of the system so that the time-averaged output equals the demand. However, this has been demonstrated to lead to overall efficiencies lower than the steady-state efficiency. Therefore, the two main reasons for the current practice of using oil burners much larger than necessary for space heating are the unavailability of reliable low firing rate oil burners and the desire to assure adequate input rate for short duration, high draw domestic hot water loads. One approach to solve this problem is to develop a burner, which can operate at two firing rates, with the lower rate being significantly lower than 0.5 gallons per hour. This paper describes the initial results of adopting this approach through a pulsed flow nozzle. It has been shown that the concept of flow modulation with a small solenoid valve is feasible. Especially in the second configuration tested, where the Lee valve was integrated with the nozzle, reasonable modulation in flow of the order of 1.7 could be achieved. For this first prototype, the combustion performance is still not quite satisfactory. Improvements in operation, for example by providing a sharp and positive shut-off so that there is no flow under low pressures with consequent poor atomization could lead to better combustion performance. This could be achieved by using nozzles that have shut off or check valves for example. It is recommended that more work in cooperation with the valve manufacturer could produce a technically viable system. Marketability is of course a far more complex problem to be addressed once a technically viable product is available.

KRISHNA,C.R.; BUTCHER,T.A.; KAMATH,B.R.

2004-10-01

252

Heart rate and heart rate variability during a novel object test and a handling test in young horses  

Microsoft Academic Search

Forty-one Dutch Warmblood immature horses were used in a study to quantify temperamental traits on the basis of heart rate (HR) and heart rate variability (HRV) measures. Half of the horses received additional training from the age of 5 months onwards; the other half did not. Horses were tested at 9, 10, 21 and 22 months of age in a

E. K. Visser; C. G. van Reenen; M. B. H. Schilder; J. H. Knaap; A. Barneveld; H. J. Blokhuis

2002-01-01

253

Human heart rate variability relation is unchanged during motion sickness  

NASA Technical Reports Server (NTRS)

In a study of 18 human subjects, we applied a new technique, estimation of the transfer function between instantaneous lung volume (ILV) and instantaneous heart rate (HR), to assess autonomic activity during motion sickness. Two control recordings of ILV and electrocardiogram (ECG) were made prior to the development of motion sickness. During the first, subjects were seated motionless, and during the second they were seated rotating sinusoidally about an earth vertical axis. Subjects then wore prism goggles that reverse the left-right visual field and performed manual tasks until they developed moderate motion sickness. Finally, ILV and ECG were recorded while subjects maintained a relatively constant level of sickness by intermittent eye closure during rotation with the goggles. Based on analyses of ILV to HR transfer functions from the three conditions, we were unable to demonstrate a change in autonomic control of heart rate due to rotation alone or due to motion sickness. These findings do not support the notion that moderate motion sickness is manifested as a generalized autonomic response.

Mullen, T. J.; Berger, R. D.; Oman, C. M.; Cohen, R. J.

1998-01-01

254

Variable Rate Variable Power MIMO System for Integrated Voice and Data Services  

Microsoft Academic Search

We propose an adaptive rate and power allocation algorithm for integrated voice and data services in a multiple input multiple output (MIMO) system. Given the available power at the MIMO transmitter is limited, the voice service is given the highest priority and appropriate power is allocated to satisfy the bit error rate (BER) requirement for voice transmission. Based on the

Lay Teen Ong; Sangarapillai Lambotharan

2006-01-01

255

MODELING THE ASSOCIATION BETWEEN HEART RATE VARIABILITY AND ILLNESS IN ELITE SWIMMERS  

E-print Network

MODELING THE ASSOCIATION BETWEEN HEART RATE VARIABILITY AND ILLNESS IN ELITE SWIMMERS Philippe;43(6):1063-70" DOI : 10.1249/MSS.0b013e318204de1c #12;ABSTRACT Purpose: To determine whether heart rate variability (high frequency- HF; 0.15 Hz-0.40Hz, low frequency-LF; 0.04-0.15 Hz and HF/LF ratio) of heart rate

Paris-Sud XI, Université de

256

Short-term heart rate variability during a cognitive challenge in young and older adults  

Microsoft Academic Search

Background: attention-demanding tasks cause changes in the autonomic modulation of cardiac function. Heart rate variability, an index of autonomic modulation of heart rate, decreases with age. Objective: to examine heart rate variability in elderly and young participants at rest and during an attention- demanding task. Methods: we assessed 16 old participants (ages 72-91) and 16 college-age (ages 20-25) participants for

ROBERT WOOD; B RIAN MARAJ; C. MATTHEW LEE; R AFAEL REYES

2002-01-01

257

A constant air flow rate control of blower for residential applications  

Microsoft Academic Search

This paper presents a technique to control a blower for residential applications at a constant air flow rate using an induction motor drive. The control scheme combines a variable volt\\/hertz ratio inverter drive and an average motor current regulation loop to achieve the control of the motor torque-speed characteristics, and consequently control of the air flow rate of the blower

Sheng-Ming Yang

1997-01-01

258

A constant air flow rate control of blower for residential applications  

Microsoft Academic Search

This paper presents a technique to control a blower for residential applications at constant air flow rate using an induction motor drive. The control scheme combines a variable volt\\/hertz ratio inverter drive and an average motor current regulation loop to achieve control of the motor torque-speed characteristics, consequently controlling the air flow rate of the blower which the motor is

Sheng-Ming Yang

1998-01-01

259

Conventional heart rate variability analysis of ambulatory electrocardiographic recordings fails to predict imminent ventricular fibrillation  

NASA Technical Reports Server (NTRS)

OBJECTIVES. The purpose of this report was to study heart rate variability in Holter recordings of patients who experienced ventricular fibrillation during the recording. BACKGROUND. Decreased heart rate variability is recognized as a long-term predictor of overall and arrhythmic death after myocardial infarction. It was therefore postulated that heart rate variability would be lowest when measured immediately before ventricular fibrillation. METHODS. Conventional indexes of heart rate variability were calculated from Holter recordings of 24 patients with structural heart disease who had ventricular fibrillation during monitoring. The control group consisted of 19 patients with coronary artery disease, of comparable age and left ventricular ejection fraction, who had nonsustained ventricular tachycardia but no ventricular fibrillation. RESULTS. Heart rate variability did not differ between the two groups, and no consistent trends in heart rate variability were observed before ventricular fibrillation occurred. CONCLUSIONS. Although conventional heart rate variability is an independent long-term predictor of adverse outcome after myocardial infarction, its clinical utility as a short-term predictor of life-threatening arrhythmias remains to be elucidated.

Vybiral, T.; Glaeser, D. H.; Goldberger, A. L.; Rigney, D. R.; Hess, K. R.; Mietus, J.; Skinner, J. E.; Francis, M.; Pratt, C. M.

1993-01-01

260

Reduced Heart Rate Variability in Social Anxiety Disorder: Associations with Gender and Symptom Severity  

PubMed Central

Background Polyvagal theory emphasizes that autonomic nervous system functioning plays a key role in social behavior and emotion. The theory predicts that psychiatric disorders of social dysfunction are associated with reduced heart rate variability, an index of autonomic control, as well as social inhibition and avoidance. The purpose of this study was to examine whether heart rate variability was reduced in treatment-seeking patients diagnosed with social anxiety disorder, a disorder characterized by social fear and avoidance. Methods Social anxiety patients (n?=?53) were recruited prior to receiving psychological therapy. Healthy volunteers were recruited through the University of Sydney and the general community and were matched by gender and age (n?=?53). Heart rate variability was assessed during a five-minute recording at rest, with participants completing a range of self-report clinical symptom measures. Results Compared to controls, participants with social anxiety exhibited significant reductions across a number of heart rate variability measures. Reductions in heart rate variability were observed in females with social anxiety, compared to female controls, and in patients taking psychotropic medication compared to non-medicated patients. Finally, within the clinical group, we observed significant associations between reduced heart rate variability and increased social interaction anxiety, psychological distress, and harmful alcohol use. Conclusions The results of this study confirm that social anxiety disorder is associated with reduced heart rate variability. Resting state heart rate variability may therefore be considered a marker for social approach-related motivation and capacity for social engagement. Additionally, heart rate variability may provide a useful biomarker to explain underlying difficulties with social approach, impaired stress regulation, and behavioral inhibition, especially in disorders associated with significant impairments in these domains. PMID:23936207

Alvares, Gail A.; Quintana, Daniel S.; Kemp, Andrew H.; Van Zwieten, Anita; Balleine, Bernard W.; Hickie, Ian B.; Guastella, Adam J.

2013-01-01

261

Variable Selection and Grouping in a Paper Machine Application  

Microsoft Academic Search

This paper describes the possibilities of variable selection in large-scale industrial systems. It introduces knowledge-based, data-based and model-based methods for this purpose. As an example, Case-Based Reasoning application for the evaluation of the web break sensitivity in a paper machine is introduced. The application uses Linguistic Equations approach and basic Fuzzy Logic. The indica- tor combines the information of on-line

Timo Ahola; Esko Juuso; Kauko Leiviskä

2007-01-01

262

Multiphase Electric Machines for Variable-Speed Applications  

Microsoft Academic Search

Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been

Emil Levi

2008-01-01

263

An Evaluation of Alternative Disk Scheduling Techniques in Support of Variable Bit Rate Continuous Media  

Microsoft Academic Search

. A number of recent studies have investigated scheduling techniquesin support of variable bit rate (VBR) video. When compared withconstant bit rate (CBR) video, VBR has a lower storage and bandwidthrequirement while providing the same quality of images. However, a VBRvideo clip might exhibit a significant variance in the bit rate required tosupport its continuous display. The previous studies have

Jaber Al-marri; Shahram Ghandeharizadeh

1998-01-01

264

A new cardiac nervous system model for heart rate variability analysis  

Microsoft Academic Search

Heart rate variability (HRV) provides a noninvasive means of quantifying cardiac autonomic activity. Imbalances in autonomic activity between the sympathetic and parasympathetic systems accompany a number of cardiac disorders. This paper provides new results in mathematically modeling the cardiac nervous system responsible for fluctuations in heart rate. These results clearly demonstrate the differing varieties of heart rate fluctuations over a

M. Brennan; M. Palaniswami; P. W. Kamen

1998-01-01

265

Economically Optimal Controlled Variables for Parallel Units Application to  

E-print Network

Economically Optimal Controlled Variables for Parallel Units ­ Application to Chemical Reactors transfer area to volume [Luyben, 2007], or where deactivation of the catalyst requires regular catalyst has the advantage that it is very simple, but it will give rise to economic losses when the operating

Skogestad, Sigurd

266

Scaling-up crop models for climate variability applications  

Microsoft Academic Search

Although most dynamic crop models have been developed and tested for the scale of a homogeneous plot, applications related to climate variability are often at broader spatial scales that can incorporate considerable heterogeneity. This study reviews issues and approaches related to applying crop models at scales larger than the plot. Perfect aggregate prediction at larger scales requires perfect integration of

J. W. Hansen; J. W. Jones

2000-01-01

267

Effort—reward imbalance, heart rate, and heart rate variability: the cardiovascular risk in young finns study  

Microsoft Academic Search

Background: Work stress indicated by effort—reward imbalance is hypothesized to cause autonomic arousal, which, if prolonged\\u000a or frequent, could contribute to cardiovascular pathology. However, only limited empirical evidence on this mechanism is available.\\u000a Purpose: This study examined associations between effort-reward imbalance, heart rate (HR), and heart rate variability (HRV).\\u000a Method: The participants were 457 women and 406 men (mean age

Mirka Hintsanen; Marko Elovainio; Sampsa Puttonen; Mika Kivimäki; Tuomas Koskinen; Olli T. Raitakari; Liisa Keltikangas-Järvinen

2007-01-01

268

Dynamic cardiovagal response to motion sickness: A point-process heart rate variability study  

E-print Network

A visual display of stripes was used to examine cardiovagal response to motion sickness. Heart rate variability (HRV) was investigated using dynamic methods to discern instantaneous fluctuations in reaction to stimulus and ...

Brown, Emery N.

269

Band-phase-randomized surrogate data reveal high-frequency chaos in heart rate variability  

E-print Network

We propose a new band-phase-randomized surrogate data method to evaluate the chaotic dynamics in the high (HF) and low frequency (LF) bands of heart rate variability (HRV) in healthy subjects. The chaotic strength of normal ...

Li, Cheng

270

Heart rate variability and respiratory sinus arrhythmia assessment of affective states by bivariate autoregressive spectral analysis  

E-print Network

The study of emotions elicited by human-computer interactions is a promising field that could lead to the identification of specific patterns of affective states. We present a heart rate variability (HRV) assessment of the ...

Magagnin, Valentina

271

PARTICULATE MATTER AND HEART RATE VARIABILITY AMONG ELDERLY RETIREES: THE BALTIMORE 1998 PM STUDY  

EPA Science Inventory

This study investigates the reported relationship between ambient fine particle pollution and impaired cardiac autonomic control in the elderly. Heart rate variability (HRV) among 56 elderly (mean age 82) nonsmoking residents of a retirement center in Baltimore County, Maryland,...

272

New Insights into the Relationship Between Poincare Plot Geometry and Linear Measures of Heart Rate Variability.  

National Technical Information Service (NTIS)

The Poincare plot is an emerging Heart Rate Variability (HRV) analysis technique, the geometry of which has been shown to distinguish between healthy and unhealthy subjects in clinical settings. The Poincare plot is able to display nonlinear aspects of th...

M. Brennan, M. Palaniswami, P. Kamen

2001-01-01

273

Association of depression witk reduced heart rate variability in coronary artery disease  

Microsoft Academic Search

Decreased heart rate (HR) variability is an independent risk factor for mortality in cardiac populations. Clinical depression has also been associated with adverse outcomes in patients with coronary artery disease (CAD). This study tests the hypothesis that depressed patients with CAD have decreased HR variability compared with nondepressed CAD patients. Nineteen patients with angiographically documented CAD and either major or

Robert M. Carney; Roger D. Saunders; Kenneth E. Freedland; Phyllis Stein; Michael W. Rich; Allan S. Jaffe

1995-01-01

274

Heart Rate Variability in Idiopathic Dilated Cardiomyopathy: Characteristics and Prognostic Value  

Microsoft Academic Search

Objectives. This study was designed to evaluate heart rate variability (HRV) in patients with idiopathic dilated cardiomyopathy (IDC), to determine its correlation with hemodynamic variables and ventricular arrhythmias and to evaluate its prognostic value in IDC.Background. Previous studies have shown that HRV could predict arrhythmic events in patients after infarction, but the characteristics of HRV in IDC have not been

Laurent Fauchier; Dominique Babuty; Pierre Cosnay; Marie Laurence Autret; Jean Paul Fauchier

1997-01-01

275

Can coseismic stress variability suppress seismicity shadows? Insights from a rate-and-state friction  

E-print Network

stress value at every grid point, these results suggest that an estimate of the likely stress variabilityCan coseismic stress variability suppress seismicity shadows? Insights from a rate mechanism driving the seismicity at these timescales. The lack of correlation between the stress unloading

276

Combining neuro-fuzzy and chaos methods for intelligent time series analysis-case study of heart rate variability  

Microsoft Academic Search

The paper introduces a way of using chaos theory and a particular fuzzy neural network, called FuNN, for building adaptive, intelligent information systems. The use of the proposed connectionist-based methodology is illustrated through a biomedical application of heart rate variability (HRV) analysis. It is demonstrated that a multi-scale fractal analysis of HRV data can be used for characterisation and prediction

R. Kozma; N. K. Kasabov; J. A. Swope; M. J. A. Williams

1997-01-01

277

Changes in blood pressure and heart rate variability during dental surgery  

Microsoft Academic Search

The objective of the present study was to determine the changes in blood pressure, pulse rate, and heart rate variability during dental surgery. The study included 40 patients, 19 to 74 years of age (mean age: 42.7 ± 3.0 years), who underwent tooth extraction at our hospital. Holter electrocardiographic monitoring was used to determine the power spectrum of R-R variability

Kiyoshi Matsumura; Keiko Miura; Yutaka Takata; Hideo Kurokawa; Minoru Kajiyama; Isao Abe; Masatoshi Fujishima

1998-01-01

278

Adaptive neuro-fuzzy estimation of autonomic nervous system parameters effect on heart rate variability  

Microsoft Academic Search

Heart rate signal can be used as certain indicator of heart disease. Spectral analysis of heart rate variability (HRV) signal\\u000a makes it possible to partly separate the low-frequency (LF) sympathetic component, from the high-frequency (HF) vagal component\\u000a of autonomic cardiac control. Here, we used two important features to characterize the nonlinear fluctuations in the heart\\u000a variability signal (HRV): cardiac vagal

D. Petkovi?; Ž. ?ojbaši?

279

Heart Rate Variability Responses of a Preterm Infant to Kangaroo Care  

Microsoft Academic Search

Objective: To examine the effect of kangaroo care on heart rate variability in a healthy preterm infant. Design: Case study. Setting: Private room on a postpartum unit. Participant: A mother-preterm infant dyad. Intervention: Kangaroo (skin-to-skin) care. Main Outcome Measure: Heart rate variability, a noninvasive measurement of the sympathetic and parasympathetic components of the autonomic nerv- ous system's influence on heart

Gail C. McCain; Susan M. Ludington-Hoe; Joan Y. Swinth; Anthony J. Hadeed

280

Coping with Limitation of Bedside Measurement Instrumentation for Reliable Assessment of Fetal Heart Rate Variability  

Microsoft Academic Search

Estimation of the instantaneous variability of the fetal heart rate (FHR) is affected by the autocorrelation techniques commonly\\u000a used in Doppler ultrasound channel of today’s fetal monitors. Considerably decrease of short-term variability have been noted,\\u000a which is quite surprising because the fetal monitors determine the fetal heart rate with quite satisfying accuracy in relation\\u000a to the reference direct fetal electrocardiography.

Janusz Wrobel; Janusz Jezewski; Krzysztof Horoba

2008-01-01

281

Effects of head-down bed rest on complex heart rate variability: Response to LBNP testing  

NASA Technical Reports Server (NTRS)

Head-down bed rest is used to model physiological changes during spaceflight. We postulated that bed rest would decrease the degree of complex physiological heart rate variability. We analyzed continuous heart rate data from digitized Holter recordings in eight healthy female volunteers (age 28-34 yr) who underwent a 13-day 6 deg head-down bed rest study with serial lower body negative pressure (LBNP) trials. Heart rate variability was measured on a 4-min data sets using conventional time and frequency domain measures as well as with a new measure of signal 'complexity' (approximate entropy). Data were obtained pre-bed rest (control), during bed rest (day 4 and day 9 or 11), and 2 days post-bed rest (recovery). Tolerance to LBNP was significantly reduced on both bed rest days vs. pre-bed rest. Heart rate variability was assessed at peak LBNP. Heart rate approximate entropy was significantly decreased at day 4 and day 9 or 11, returning toward normal during recovery. Heart rate standard deviation and the ratio of high- to low-power frequency did not change significantly. We conclude that short-term bed rest is associated with a decrease in the complex variability of heart rate during LBNP testing in healthy young adult women. Measurement of heart rate complexity, using a method derived from nonlinear dynamics ('chaos theory'), may provide a sensitive marker of this loss of physiological variability, complementing conventional time and frequency domain statistical measures.

Goldberger, Ary L.; Mietus, Joseph E.; Rigney, David R.; Wood, Margie L.; Fortney, Suzanne M.

1994-01-01

282

Assessment of mental stress in warmblood horses: heart rate variability in comparison to heart rate and selected behavioural parameters  

Microsoft Academic Search

The aim of the study was to investigate whether heart rate variability (HRV) could assess alterations of the autonomic nervous system (ANS) at different levels of excitement. The behavioural and physiological responses of 20 warmblood horses to a challenging ground exercise task were studied. Prior to the experiment, the horses were evaluated at rest and during forward walking (FW). The

T. R. Rietmann; A. E. A. Stuart; P. Bernasconi; M. Stauffacher; J. A. Auer; M. A. Weishaupt

2004-01-01

283

Twenty-Four Hour Time Domain Heart Rate Variability and Heart Rate: Relations to Age and Gender Over Nine Decades  

Microsoft Academic Search

Objectives. This study sought to define the effects of age and gender effects on the normal range of time domain heart rate variability (HRV) over nine decades in healthy subjects.Background. Low HRV is considered an independent marker of mortality risk. However, the age-related decline in HRV may limit its predictive value, particularly in the elderly. Delineation of the range of

Ken Umetani; Donald H Singer; Rollin McCraty; Mike Atkinson

1998-01-01

284

Spatial heterogeneity within the plough layer: high variability of N 2O emission rates  

Microsoft Academic Search

The spatial heterogeneity and the temporal variability of N2O emission rates were examined in an arable soil. The N2O emission rates were measured using soil cover boxes. Rates were measured systematically at regular distances (7m) on a sampling grid (9 rows×9 columns) across a field plot site (60×63m). There were two sampling periods, one before (March, 4 flux rate measurements)

Manuela Röver; Otto Heinemeyer; Jean Charles Munch; Ernst-August Kaiser

1999-01-01

285

Variable dual-frequency electrostatic wave launcher for plasma applications  

NASA Astrophysics Data System (ADS)

A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example—generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently—with a high adaptability to a number of plasma dynamics and heating applications.

Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

2011-12-01

286

Variable dual-frequency electrostatic wave launcher for plasma applications.  

PubMed

A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example--generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently--with a high adaptability to a number of plasma dynamics and heating applications. PMID:22225213

Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

2011-12-01

287

Parathyroidectomy and Heart Rate Variability in Patients with Stage 5 CKD  

PubMed Central

Summary Background and objectives Lower heart rate variability implies increased risk of cardiovascular disease. This study aimed to evaluate the relationship between mineral metabolism and heart rate variability and longitudinal changes of heart rate variability after parathyroidectomy in stage 5 CKD patients. Design, setting, participants, & measurements This cross-sectional study included 118 stage 5 CKD patients, 87 controls, and a prospective study in two subgroups classified as successful (n=17) and unsuccessful (n=4) parathyroidectomy follow-up enrolled from March of 2011 to December of 2012. Blood examination and 24-hour Holter for heart rate variability were measured. Results Most heart rate variability indices were lower in stage 5 CKD patients. In multivariate stepwise regression models, serum intact parathyroid hormone was correlated with mean normal-to-normal R–R intervals, mean heart rate, and very low frequency, serum calcium was correlated with SD of 5-minute average of normal R–R intervals, and serum phosphorus was correlated with very low frequency and low frequency/high frequency. Compared with baseline, the successful parathyroidectomy subgroup had significant improvements in mean normal-to-normal R–R intervals, mean heart rate, SD of normal-to-normal R–R intervals, SD of 5-minute average of normal R–R intervals, very low frequency, high frequency, and low frequency/high frequency. There was no significant change of heart rate variability in patients after unsuccessful parathyroidectomy. Conclusions Disorders of mineral metabolism are associated with decreased heart rate variability in stage 5 CKD. Successful parathyroidectomy may contribute to reverse this cardiovascular disease risk in severe secondary hyperparathyroidism patients. PMID:23660181

Zhang, Jing; Yu, Xiangbao; Sun, Bin; Bai, Jianling; Wei, Yongyue; Zha, Xiaoming; Cui, Yiyao; Zeng, Ming; Zhang, Jingjing; Liu, Jia; Mao, Huijuan; Zhang, Bo; Ren, Haibin; Ge, Yifei; Xu, Xueqiang; Shen, Zhixiang; Xing, Changying; Cao, Kejiang

2013-01-01

288

Fast FSR variable selection with applications to clinical trials.  

PubMed

A new version of the false selection rate variable selection method of Wu, Boos, and Stefanski (2007, Journal of the American Statistical Association 102, 235-243) is developed that requires no simulation. This version allows the tuning parameter in forward selection to be estimated simply by hand calculation from a summary table of output even for situations where the number of explanatory variables is larger than the sample size. Because of the computational simplicity, the method can be used in permutation tests and inside bagging loops for improved prediction. Illustration is provided in clinical trials for linear regression, logistic regression, and Cox proportional hazards regression. PMID:18945266

Boos, Dennis D; Stefanski, Leonard A; Wu, Yujun

2009-09-01

289

Correlation of heart rate variability with cardiac functional and metabolic variables in cyclists with training induced left ventricular hypertrophy  

Microsoft Academic Search

OBJECTIVETo examine the correlation between heart rate variability and left ventricular mass in cyclists with an athlete’s heart.METHODSLeft ventricular mass and diastolic function were determined at rest and myocardial high energy phosphates were quantified at rest and during atropine–dobutamine stress in 12 male cyclists and 10 control subjects, using magnetic resonance techniques. Ambulatory 24 hour ECG recordings were obtained, and

B M Pluim; C A Swenne; A H Zwinderman; A C Maan; A van der Laarse; J Doornbos; E E Van der Wall

1999-01-01

290

Effect of meal content on heart rate variability and cardiovascular reactivity to mental stress  

PubMed Central

Little is known about transient effects of foods and nutrients on reactivity to mental stress. In a randomized crossover study of healthy adults (n = 20), we measured heart rate variability (respiratory sinus arrhythmia), blood pressure, and other hemodynamic variables after three test meals varying in type and amount of fat. Measurements were collected at rest and during speech and cold pressor tasks. There were significant post-meal changes in resting diastolic blood pressure (?4%), cardiac output (+18%), total peripheral resistance (?17%), and interleukin-6 (?27%). Heart rate variability and hemodynamic reactivity to stress was not affected by meal content. We recommend that future studies control for time since last meal and continue to examine effects of meal content on heart rate variability. PMID:22236402

Sauder, Katherine A.; Johnston, Elyse R.; Skulas-Ray, Ann C.; Campbell, Tavis S.; West, Sheila G.

2012-01-01

291

Effects of practice and preferred rate on perceived exertion, metabolic variables and movement control  

Microsoft Academic Search

One interesting feature of motor skill learning and control is our propensity to reduce the metabolic energy cost of achieving the task goal with practice and, if unconstrained, to adapt movements to task constraints using an energy-efficient preferred mode. This study investigated the effects of preferred rate and practice on metabolic variables, ratings of perceived exertion (RPE) and movement control.

W. A Sparrow; K. M Hughes; A. P Russell; P. F Le Rossignol

1999-01-01

292

Short-term analysis of heart-rate variability of adapted wavelet transforms  

Microsoft Academic Search

The purpose of this study is to characterize the heart rate variability (HRV) signal in the frequency domain by using wavelet and cosine packets. Here, the authors introduce the adapted wavelet transform methods to analyze heart-rate fluctuations. These methods were chosen because the components in the signals can be analyzed and quantified at different scales, e.g., long windows can be

U. Wiklund; M. Akay; U. Niklasson

1997-01-01

293

Fuel toxicity on Isochrysis galbana and a coastal phytoplankton assemblage: Growth rate vs. variable fluorescence  

Microsoft Academic Search

Laboratory cultures of the flagellate Isochrysis galbana and a coastal phytoplankton assemblage were used to assess the feasibility of variable fluorescence (Fv), measured by means of fast repetition rate fluorometry, as endpoint to monitor the effect of fuel on microalgae as compared to phytoplankton growth rate. Parallel changes in cell size of I. galbana and taxonomic composition of the natural

P. Pérez; E. Fernández; R. Beiras

2010-01-01

294

Fixed Or Variable Rate Choice In The Commercial Bank Business Loan Market  

Microsoft Academic Search

We study the choice available to business borrowers and lenders between fixed rate and variable rate bank loans. Unlike previous studies that examine residential mortgage loans, this analysis examines commercial and industrial loans. Business loans differ in attributes from mortgage loans and hence provide an opportunity to test determinants of the mortgage loan choice decision for other loan types. The

Manoj Athavale; Robert O. Edmister

295

Multiscale regularity analysis of the Heart Rate Variability: stratification of cardiac death risk  

Microsoft Academic Search

Subjects with ischemic dilated cardiomiopathy tend to suffer episodes of sudden cardiac death, thus risk stratification is essential to establish an adequate therapy for the patients. In this work, a new methodology was proposed for the study of the heart rate variability by using a multiscale analysis based on the concept of entropy rates, for improving risk prediction in cardiac

J. F. Valencia; M. Vallverdu; I. Cygankiewicz; A. Voss; R. Vazquez; A. Bayés de Luna; P. Caminal

2007-01-01

296

Cardiac Autonomic Regulation under Hypnosis Assessed by Heart Rate Variability: Spectral Analysis and Fractal Complexity  

Microsoft Academic Search

Objective: This study examined the effects of hypnosis on autonomic cardiac control. We hypothesized a modification of autonomic modulation of the heart rate with an enhanced vagal tone during hypnosis compared to baseline. Methods: In 12 healthy subjects (6 men and 6 women, 22.2 ± 1.0 years of age) ECG was recorded at baseline and during hypnosis. Heart rate variability

André E. Aubert; Bart Verheyden; Frank Beckers; Jan Tack; Joris Vandenberghe

2009-01-01

297

Validation of a new control system for Elekta accelerators facilitating continuously variable dose rate  

SciTech Connect

Purpose: Elekta accelerators controlled by the current clinically used accelerator control system, Desktop 7.01 (D7), uses binned variable dose rate (BVDR) for volumetric modulated arc therapy (VMAT). The next version of the treatment control system (Integrity) supports continuously variable dose rate (CVDR) as well as BVDR. Using CVDR opposed to BVDR for VMAT has the potential of reducing the treatment time but may lead to lower dosimetric accuracy due to faster moving accelerator parts. Using D7 and a test version of Integrity, differences in ability to control the accelerator, treatment efficiency, and dosimetric accuracy between the two systems were investigated. Methods: Single parameter tests were designed to expose differences in the way the two systems control the movements of the accelerator. In these tests, either the jaws, multi leaf collimators (MLCs), or gantry moved at constant speed while the dose rate was changed in discrete steps. The positional errors of the moving component and dose rate were recorded using the control systems with a sampling frequency of 4 Hz. The clinical applicability of Integrity was tested using 15 clinically used VMAT plans (5 prostate, 5 H and N, and 5 lung) generated by the SmartArc algorithm in PINNACLE. The treatment time was measured from beam-on to beam-off and the accuracy of the dose delivery was assessed by comparing DELTA4 measurements and PINNACLE calculated doses using gamma evaluation. Results: The single parameter tests showed that Integrity had an improved feedback between gantry motion and dose rate at the slight expense of MLC control compared to D7. The single parameter test did not reveal any significant differences in the control of either jaws or backup jaws between the two systems. These differences in gantry and MLC control together with the use of CVDR gives a smoother Integrity VMAT delivery compared to D7 with less abrupt changes in accelerator motion. Gamma evaluation (2% of 2 Gy and 2 mm) of the calculated doses and DELTA4 measured doses corrected for systematic errors showed an average pass rate of more than 97.8% for both D7, Integrity BVDR, and Integrity CVDR deliveries. Direct comparisons between the measured doses using strict gamma criteria of 0.5% and 0.5 mm showed excellent agreement between D7 and Integrity delivered doses with average pass rates above 95.7%. Finally, the Integrity control system resulted in a significant 35% (55 {+-} 13 s) reduction in treatment time, on average. Conclusions: Single parameter tests showed that the two control systems differed in their feedback loops between MLC, gantry, and dose rate. These differences made the VMAT deliveries more smooth using the new Integrity treatment control system, compared to the current Desktop 7.01. Together with the use of CVDR, which results in less abrupt changes in dose rate, this further increases the smoothness of the delivery. The use of CVDR for VMAT with the Integrity desktop results in a significant reduction in treatment time compared to BVDR with an average reduction of 35%. This decrease in delivery time was achieved without compromising the dosimetric accuracy.

Bertelsen, Anders; Lorenzen, Ebbe L.; Brink, Carsten [Institute of Clinical Research, University of Southern Denmark, Odense DK-5000, Denmark and Laboratory of Radiation Physics, Odense University Hospital, Odense DK-5000 (Denmark)

2011-08-15

298

Continuously variable transmission: Assessment of applicability to advance electric vehicles  

NASA Technical Reports Server (NTRS)

A brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. The CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. The arrangement and function of several CVT concepts are cited along with their current developmental status. The results of preliminary design studies conducted on four CVT concepts for use in advanced electric vehicles are discussed.

Loewenthal, S. H.; Parker, R. J.

1981-01-01

299

Removal of Respiratory Influences From Heart Rate Variability in Stress Monitoring  

Microsoft Academic Search

This paper addresses a major weakness of traditional heart-rate-variability (HRV) analysis for the purpose of moni- toring stress: sensitivity to respiratory influences. To address this issue, a linear system-identification model of the cardiorespiratory system using commercial heart rate monitors and respiratory sensors was constructed. Subtraction of respiratory driven fluc- tuations in heart rate leads to a residual signal where the

Jongyoon Choi; Ricardo Gutierrez-Osuna

2011-01-01

300

Relation of heart rate recovery to heart rate variability in persons with paraplegia  

Microsoft Academic Search

Purpose  Heart rate recovery (HRR) after treadmill exercise testing is an index of cardiac autonomic activity in non-disabled persons,\\u000a but it is unknown if this is also the case in individuals with spinal cord injury (SCI). We investigated the relationship\\u000a between HRR after maximal arm exercise testing and resting autonomic activity in persons with paraplegia.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  A total of 17 (male n = 9,

Sae Young Jae; Kevin S. Heffernan; Miyoung Lee; Bo Fernhall

2011-01-01

301

Probabilistic pipe fracture evaluations for leak-rate-detection applications  

SciTech Connect

Regulatory Guide 1.45, {open_quotes}Reactor Coolant Pressure Boundary Leakage Detection Systems,{close_quotes} was published by the U.S. Nuclear Regulatory Commission (NRC) in May 1973, and provides guidance on leak detection methods and system requirements for Light Water Reactors. Additionally, leak detection limits are specified in plant Technical Specifications and are different for Boiling Water Reactors (BWRs) and Pressurized Water Reactors (PWRs). These leak detection limits are also used in leak-before-break evaluations performed in accordance with Draft Standard Review Plan, Section 3.6.3, {open_quotes}Leak Before Break Evaluation Procedures{close_quotes} where a margin of 10 on the leak detection limit is used in determining the crack size considered in subsequent fracture analyses. This study was requested by the NRC to: (1) evaluate the conditional failure probability for BWR and PWR piping for pipes that were leaking at the allowable leak detection limit, and (2) evaluate the margin of 10 to determine if it was unnecessarily large. A probabilistic approach was undertaken to conduct fracture evaluations of circumferentially cracked pipes for leak-rate-detection applications. Sixteen nuclear piping systems in BWR and PWR plants were analyzed to evaluate conditional failure probability and effects of crack-morphology variability on the current margins used in leak rate detection for leak-before-break.

Rahman, S.; Ghadiali, N.; Paul, D.; Wilkowski, G. [Battelle, Columbus, OH (United States)

1995-04-01

302

Suboccipital Decompression Enhances Heart Rate Variability Indices of Cardiac Control in Healthy Subjects  

PubMed Central

Abstract Objectives Osteopathic manipulative treatment (OMT) focused on the upper cervical spine is theorized to affect the function of the vagus nerve and thereby influence the parasympathetic branch of the autonomic nervous system. This study was designed to determine the acute effect of upper cervical spine manipulation on cardiac autonomic control as measured by heart rate variability. Design Nineteen healthy, young adult subjects underwent three different experimental interventions administered in random order: cervical OMT, sham manipulation, and time control. Six minutes of electrocardiographic data were collected before and after each intervention, and heart rate variability was assessed by both time-domain and frequency-domain measures. Results No differences in resting heart rate or any measure of heart rate variability were observed between the baseline periods prior to each intervention. The OMT protocol resulted in an increase in the standard deviation of the normal-to-normal intervals (0.12±0.082 seconds, p<0.01), an increase in the high frequency spectral power (p=0.03), and a decrease in the low/high frequency spectral ratio (p=0.01) relative to the sham and time control conditions. No significant differences between sham and time control were observed (p>0.11 for all variables). Conclusions These data support the hypothesis that upper cervical spine manipulation can acutely affect measures of heart rate variability in healthy individuals. PMID:22994907

Giles, Paul D.; Hensel, Kendi L.; Pacchia, Christina F.

2013-01-01

303

Inhalation of ultrafine carbon particles alters heart rate and heart rate variability in people with type 2 diabetes  

PubMed Central

Background Diabetes may confer an increased risk for the cardiovascular health effects of particulate air pollution, but few human clinical studies of air pollution have included people with diabetes. Ultrafine particles (UFP, ?100 nm in diameter) have been hypothesized to be an important component of particulate air pollution with regard to cardiovascular health effects. Methods 17 never-smoker subjects 30–60 years of age, with stable type 2 diabetes but otherwise healthy, inhaled either filtered air (0–10 particles/cm3) or elemental carbon UFP (~107 particles/cm3, ~50 ug/m3, count median diameter 32 nm) by mouthpiece, for 2 hours at rest, in a double-blind, randomized, crossover study design. A digital 12-lead electrocardiogram (ECG) was recorded continuously for 48 hours, beginning 1 hour prior to exposure. Results Analysis of 5-minute segments of the ECG during quiet rest showed reduced high-frequency heart rate variability with UFP relative to air exposure (p?=?0.014), paralleled by non-significant reductions in time-domain heart rate variability parameters. In the analysis of longer durations of the ECG, we found that UFP exposure increased the heart rate relative to air exposure. During the 21- to 45-hour interval after exposure, the average heart rate increased approximately 8 beats per minute with UFP, compared to 5 beats per minute with air (p?=?0.045). There were no UFP effects on cardiac rhythm or repolarization. Conclusions Inhalation of elemental carbon ultrafine particles alters heart rate and heart rate variability in people with type 2 diabetes. Our findings suggest that effects may occur and persist hours after a single 2-hour exposure. PMID:25028096

2014-01-01

304

Autonomic effects of refractory epilepsy on heart rate variability in children: influence of intermittent vagus nerve stimulation  

E-print Network

Autonomic effects of refractory epilepsy on heart rate variability in children: influence HRV Heart rate variability LFnu Low-frequency normalized units SWS Slow-wave sleep VNS Vagus nerve heart rate variability in children with refractory epilepsy and the influence of VNS on this parameter

305

Abstract--Heart rate variability (HRV) measures have been used to assess autonomic cardiac regulation. The standard  

E-print Network

Abstract--Heart rate variability (HRV) measures have been used to assess autonomic cardiac. The HF peak, while promising, would require further studies. Keywords--Heart rate variability (HRV), electrocardiogram (ECG) I. INTRODUCTION Heart rate variability (HRV) has been used to assess the level of autonomic

306

Abstract--The analysis of heart rate variability (HRV) signals is an important tool for studying the autonomic nervous  

E-print Network

Abstract-- The analysis of heart rate variability (HRV) signals is an important tool for studying this balance varies with time. This work presents a tool for time-frequency analysis of heart rate variability a tool for time-frequency analysis of heart rate variability (HRV), which was developed in Matlab 6

Carvalho, João Luiz

307

Prognostic value of heart rate variability for sudden death and major arrhythmic events in patients with idiopathic dilated cardiomyopathy  

Microsoft Academic Search

OBJECTIVEThis study was designed to evaluate the prognostic value of heart rate variability for sudden death, resuscitated ventricular fibrillation or sustained ventricular tachycardia in patients with idiopathic dilated cardiomyopathy.BACKGROUNDPrevious studies have shown that heart rate variability could predict arrhythmic events and sudden death in postinfarction patients, but the prognostic value of heart rate variability for arrhythmic events or sudden death

Laurent Fauchier; Dominique Babuty; Pierre Cosnay; Jean Paul Fauchier

1999-01-01

308

The Association of Heart Rate Variability with Parkinsonian Motor Symptom Duration  

PubMed Central

Purpose Impaired cardiovascular autonomic regulation is a non-motor symptom of Parkinson's disease (PD) and may increase long-term morbidity. This study applied frequency-domain analysis of heart rate variability (HRV) to understand the progression of sympathetic and parasympathetic cardiac regulation in patients with PD. Materials and Methods In this cross-sectional study, 21 male and 11 female Taiwanese patients with advanced PD and 32 healthy gender- and age-matched subjects were enrolled. To minimize artifacts due to subject motion, daytime electrocardiograms for 5 minutes were recorded in awake patients during levodopa-on periods and controls. Using fast Fourier transformation, heart rate variables were quantified into a high-frequency power component [0.15-0.45 Hz, considered to reflect vagal (parasympathetic) regulation], low-frequency power component (0.04-0.15 Hz, reflecting mixed sympathetic and parasympathetic regulation), and low-frequency power in normalized units (reflecting sympathetic regulation). The significance of between-group differences was analyzed using the paired t-test. Pearson correlation analysis and stepwise regression analysis were applied to assess the correlation of patient age, PD duration, and disease severity (represented by the Unified Parkinson's Disease Rating Scale) with each heart rate variables. Results Impaired HRV is significantly correlated with the duration of PD, but not with disease severity and patient age. Meanwhile, parasympathetic heart rate variable is more likely than sympathetic heart rate variable to be affected by PD. Conclusion PD is more likely to affect cardiac parasympathetic regulation than sympathetic regulation by time and the heart rate variables have the association with Parkinsonian motor symptom duration. PMID:25048488

Harnod, Dorji; Wen, Shu-Hui; Chen, Shin-Yuan

2014-01-01

309

Evaluation of cardiac autonomic functions in patients with ankylosing spondylitis via heart rate recovery and heart rate variability  

Microsoft Academic Search

Objective  The aim of this study was to evaluate heart rate variability (HRV) and heart rate recovery (HRR) in otherwise healthy ankylosing\\u000a spondlitis (AS) patients and control subjects.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  A total of 28 patients with AS and 30 volunteers matched for age and sex were enrolled. All subjects underwent HRV analysis,\\u000a exercise testing (ET), and transthoracic echocardiography. HRR indices were calculated by

Ergun Baris Kaya; Sercan Okutucu; Hakan Aksoy; Ugur Nadir Karakulak; Erol Tulumen; Oya Ozdemir; Fatma Inanici; Kudret Aytemir; Giray Kabakci; Lale Tokgozoglu; Hilmi Ozkutlu; Ali Oto

2010-01-01

310

Determining the causes of fault slip rate variability for Northern Apennine thrusts on intermediate timescales  

NASA Astrophysics Data System (ADS)

Documenting fault slip rate variability on intermediate (10^4-10^5 yr) timescales is crucial for understanding the process-linkages of short-term (10^1-10^3 yr) and long-term (10^6 yr) patterns of deformation; however, the lack of long records of fault slip with 10^4-10^5 yr resolution presents a major barrier to understanding the underlying process responsible for slip rate variability at those timescales. Taking advantage of spectacular, continuous exposure of growth strata, we document 10^4-10^5 yr resolution records of unsteady fault slip for the past 3.0 myr for three unconnected, shallow blind thrust anticlines growing along the Northern Apennine mountain front, Italy. Fault slip rates for these thrusts were determined from progressive restorations of marine and continental growth strata deposited on the anticlinal limbs. These restorations were supported by subsurface corre-lations of the measured growth sections in order to constrain the fold geometries and kin-ematics. Magnetostratigraphy, cyclostratigraphy, cosmogenic radionuclide (CRN) burial dating, and optically stimulated luminescence (OSL) burial dating provided the high-resolution age models for the growth sections. Slip histories determined from our pro-gressive restorations indicate that all three of the thrust faults exhibited high-frequency slip rate variability. This variability is typically manifest by longer periods of decelerated fault slip punctuated by shorter periods of accelerated fault slip, typically lasting between 80-200 kyr. During times when slip rates were slow, growth strata geometries show ac-celerated slip was accommodated by more foreland structures, suggesting slip partitioning at 10^4-10^5 yr timescales. This high frequency variability is superimposed on a low frequency slip rate variability manifest by an overall deceleration in slip on the shallow thrusts since 3.0 myr. Major decelerations in slip rates were coincident with the activation of thick-skinned thrusting in the Apennines, representing a dynamic reorganization of the Apennine wedge. This suggests two separate causes for slip rate variability on Apennines thrusts: a high-frequency variability that is likely due to processes internal to the wedge, such as slip partitioning, and a low frequency variability that is probably caused by exter-nal forces affecting the entire Apennine wedge.

Gunderson, K. L.; Anastasio, D. J.; Pazzaglia, F. J.

2012-12-01

311

Determinants of the variability of heart rate measures during a competitive period in young soccer players  

Microsoft Academic Search

Measurements of exercise heart rate (HRex), HR recovery (HRR) and HR variability (HRV) are used as indices of training status. However, the day-to-day variability\\u000a of these indices throughout a competitive soccer period is unknown. On 14 occasions during a 3-week competition camp, 18 under\\u000a 15 (U15) and 15 under 17 (U17) years soccer players performed a 5-min submaximal run, followed

Martin Buchheit; Alberto Mendez-Villanueva; Marc J. Quod; Nicholas Poulos; Pitre Bourdon

2010-01-01

312

December 2002 Issue #10 2002 Determining Biosolid Application Rates  

E-print Network

December 2002 Issue #10 ­ 2002 Determining Biosolid Application Rates Richard Wolkowski, Extension Chapter NR 204 regulates biosolid (sewage sludge) management in Wisconsin. It requires that University of a crop production pro-gram. Most biosolid application rates are based on the nitrogen (N) need

Balser, Teri C.

313

Workshop on Thermonuclear Reaction Rates for Astrophysics Applications  

E-print Network

Workshop on Thermonuclear Reaction Rates for Astrophysics Applications 24-25 November 2011, Athens circular for the Workshop on Thermonuclear Reaction Rates for Astrophysics Applications, to be held-of-the-art astrophysics models to the nuclear physics needs with special emphasis on the role and determination

314

School Counselors as Social Capital: The Effects of High School College Counseling on College Application Rates  

ERIC Educational Resources Information Center

Using social capital theory as a framework, the authors examined data from the Educational Longitudinal Study of 2002 (Ingels, Pratt, Rogers, Siegel, & Stutts, 2004) to investigate how student contact with high school counselors about college information and other college-related variables influence students' college application rates. In addition…

Bryan, Julia; Moore-Thomas, Cheryl; Day-Vines, Norma L.; Holcomb-McCoy, Cheryl

2011-01-01

315

Reduced heart rate variability is associated with worse cognitive performance in elderly Mexican Americans.  

PubMed

Reduced heart rate variability is a strong predictor of cardiovascular risk factors, cardiovascular events, and mortality and thus may be associated with cognitive neurodegeneration. Yet, this has been relatively unexplored, particularly in minority populations with high cardiovascular burden. We used data from the Sacramento Area Latino Study on Aging to examine the cross-sectional association of reduced heart rate variability with cognitive function among elderly Mexican Americans. A total of 869 participants (mean age, 75 years; 59% women) had their 6-minute heart rate variability measured using an ECG monitor and respiration pacer in response to deep breathing. We used the mean circular resultant, known as R bar, as a measure of heart rate variability and categorized it into quartiles (Q1 to Q4 of R bar: reduced to high heart rate variability). Cognitive function was assessed using the modified Mini-Mental State Examination, a 100-point test of global cognitive function, and the Spanish and English verbal learning test, a 15-point test of verbal memory recall. In fully adjusted linear regression models, participants in quartile 1 had a 4-point lower modified Mini-Mental State Examination score (P<0.01), those in quartile 2 had a 2-point lower score (P=0.04), and those in quartile 3 had a 1-point lower score (P=0.35) compared with those in the highest quartile of R bar. Reduced R bar was not associated with verbal memory. Our results suggest that reduced heart rate variability is associated with worse performance on the test of global cognitive function, above and beyond traditional cardiovascular risk factors. PMID:24144650

Zeki Al Hazzouri, Adina; Haan, Mary N; Deng, Yingzi; Neuhaus, John; Yaffe, Kristine

2014-01-01

316

Low-frequency heart rate variability is related to the breath-to-breath variability in the respiratory pattern.  

PubMed

Changes in heart rate variability (HRV) at "respiratory" frequencies (0.15-0.5?Hz) may result from changes in respiration rather than autonomic control. We now investigate if the differences in HRV power in the low-frequency (LF) band (0.05-0.15?Hz, HRV(LF)) can also be predicted by respiration variability, quantified by the fraction of tidal volume power in the LF (V(LF,n)). Three experimental protocols were considered: paced breathing, mental effort tasks, and a repeated attentional task. Significant intra- and interindividual correlations were found between changes in HRV(LF) and V(LF,n) despite all subjects having a respiratory frequency above the LF band. Respiratory parameters (respiratory period, tidal volume, and V(LF,n)) could predict up to 79% of HRV(LF) differences in some cases. This suggests that respiratory variability is another mechanism of HRV(LF) generation, which should be always monitored, assessed, and considered in the interpretation of HRV changes. PMID:24423137

Beda, Alessandro; Simpson, David M; Carvalho, Nadja C; Carvalho, Alysson Roncally S

2014-02-01

317

A new measure of acceleration of heart rate: dependence on age and comparison with time domain conventional heart rate variability measures  

E-print Network

A new measure of acceleration of heart rate: dependence on age and comparison with time domain conventional heart rate variability measures Giuseppe Germanò, M.D., Gianfranco Piccirillo, M.D., *Camillo The heart rate variability (HRV) results from a variety of factors that are not purely stochastic

Cammarota, Camillo

318

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 53, NO. 1, JANUARY 2006 1 Recent Advances in Heart Rate Variability  

E-print Network

in Heart Rate Variability Signal Processing and Interpretation OVER the past 30 years, heart rate which issued a seminal paper: "Heart rate variability: standards of measure- ment, physiological proposed in the post-partum period, as well as for monitoring ECG and heart rate characteristics

319

Does fractality in heart rate variability indicate the development of fetal neural processes?  

NASA Astrophysics Data System (ADS)

By using an improved detrended fluctuation analysis we studied the scaling behaviour of 53 long-term series of fetal heart rate fluctuations. Our results suggest that fractality begins to arise around 24 weeks of normal human gestation and that this condition, showing some additional developments, seems to be preserved during gestation. This may provide new evidence of a role played by cortical-to-subcortical pathways in the long-term fractal nature of heart rate variability data.

Echeverría, J. C.; Woolfson, M. S.; Crowe, J. A.; Hayes-Gill, B. R.; Piéri, Jean F.; Spencer, C. J.; James, D. K.

2004-10-01

320

Stretching increases heart rate variability in healthy athletes complaining about limited muscular flexibility  

Microsoft Academic Search

An increase in muscular flexibility, as well as a significant beneficial effect on heart rate and heart rate variability (HRV), was observed in healthy male athletes after performing a standardized 15-minute stretching-program over a period of 28 days. We believe the HRV increase to be due, at least in part, to the improved vagal and\\/or diminished sympathetic control. Therefore, we

Michael Mueck-Weymann; G. Janshoff; H. Mueck

2004-01-01

321

Quantification and variability analysis of bacterial cross-contamination rates in common food service tasks.  

PubMed

This study investigated bacterial transfer rates between hands and other common surfaces involved in food preparation in the kitchen. Nalidixic acid-resistant Enterobacter aerogenes B199A was used as a surrogate microorganism to follow the cross-contamination events. Samples from at least 30 different participants were collected to determine the statistical distribution of each cross-contamination rate and to quantify the natural variability associated with that rate. The transfer rates among hands, foods, and kitchen surfaces were highly variable, being as low as 0.0005% and as high as 100%. A normal distribution was used to describe the variability in the logarithm of the transfer rates. The mean +/- SD of the normal distributions were, in log percent transfer rate, chicken to hand (0.94 +/- 0.68), cutting board to lettuce (0.90 +/- 0.59), spigot to hand (0.36 +/- 0.90), hand to lettuce (-0.12 +/- 1.07), prewashed hand to postwashed hand (i.e., hand washing efficiency) (-0.20 +/- 1.42), and hand to spigot (-0.80 +/- 1.09). Quantifying the cross-contamination risk associated with various steps in the food preparation process can provide a scientific basis for risk management efforts in both home and food service kitchens. PMID:11198444

Chen, Y; Jackson, K M; Chea, F P; Schaffner, D W

2001-01-01

322

Blumlein configuration for high-repetition-rate pulse generation of variable duration and polarity using synchronized switch control.  

PubMed

Blumlein generators are used in different applications such as radars, lasers, and also recently in various biomedical studies, where the effects of high-voltage nanosecond pulses on biological cells are evaluated. In these studies, it was demonstrated that by applying high-voltage nanosecond pulses to cells, plasma membrane and cell organelles are permeabilized. As suggested in a recent publication, the repetition rate and polarity of nanosecond high-voltage pulses could have an important effect on the electropermeabilization process, and consequently, on the observed phenomena. Therefore, we designed a new Blumlein configuration that enables a higher repetition rate of variable duration of either bipolar or unipolar high-voltage pulses. We achieved a maximal pulse repetition rate of 1.1 MHz. However, theoretically, this rate could be even higher. We labeled endocytotic vesicles with lucifer yellow and added propidium iodide to a cell suspension for testing the cell plasma membrane integrity, so we were able to observe the permeabilization of endocytotic vesicles and the cell plasma membrane at the same time. The new design of pulse generator was built, verified, and also tested in experiments. The resulting flexibility and variability allow further in vitro experiments to determine the importance of the pulse repetition rate and pulse polarity on membrane permeabilization -- both of the cell plasma membrane as well as of cell organelle membranes. PMID:19635688

Rebersek, Matej; Kranjc, Matej; Pavliha, Denis; Batista-Napotnik, Tina; Vrtacnik, Danilo; Amon, Slavko; Miklavcic, Damijan

2009-11-01

323

Detection of Obstructive Sleep Apnea through Auditory Display of Heart Rate Variability  

E-print Network

Detection of Obstructive Sleep Apnea through Auditory Display of Heart Rate Variability M Ballora the diagnosis of obstructive sleep apnea as a problem of orchestration and melody. 1. Introduction The auditory an extensive set of list and array processing operations, as well as a method for generating ("spawning

324

Atypical Pupillary Light Reflex and Heart Rate Variability in Children with Autism Spectrum Disorder  

ERIC Educational Resources Information Center

We investigated pupillary light reflex (PLR) in 152 children with ASD, 116 typically developing (TD) children, and 36 children with non-ASD neurodevelopmental disorders (NDDs). Heart rate variability (HRV) was measured simultaneously to study potential impairments in the autonomic nervous system (ANS) associated with ASD. The results showed that…

Daluwatte, Chathuri; Miles, Judith H.; Christ, Shawn E.; Beversdorf, David Q.; Takahashi, T. Nicole; Yao, Gang

2013-01-01

325

Heart Rate Variability during Social Interactions in Children with and without Psychopathology: A Meta-Analysis  

ERIC Educational Resources Information Center

Background: The inability to regulate autonomic activity during social interactions is believed to contribute to social and emotional dysregulation in children. Research has employed heart rate variability (HRV) during both socially engaging and socially disengaging dyadic tasks between children and adults to assess this. Methods: We conducted a…

Shahrestani, Sara; Stewart, Elizabeth M.; Quintana, Daniel S.; Hickie, Ian B.; Guastella, Adam J.

2014-01-01

326

Field Validity of Heart Rate Variability Metrics Produced by QRSTool and CMetX  

ERIC Educational Resources Information Center

Interest in heart rate variability (HRV) metrics as markers of physiological and psychological health continues to grow beyond those with psychophysiological expertise, increasing the importance of developing suitable tools for researchers new to the field. Allen, Chambers, and Towers (2007) developed QRSTool and CMetX software as simple,…

Hibbert, Anita S.; Weinberg, Anna; Klonsky, E. David

2012-01-01

327

Fetal Heart Rate and Variability: Stability and Prediction to Developmental Outcomes in Early Childhood  

ERIC Educational Resources Information Center

Stability in cardiac indicators before birth and their utility in predicting variation in postnatal development were examined. Fetal heart rate and variability were measured longitudinally from 20 through 38 weeks gestation (n = 137) and again at age 2 (n = 79). Significant within-individual stability during the prenatal period and into childhood…

DiPietro, Janet A.; Bornstein, Marc H.; Hahn, Chun-Shin; Costigan, Kathleen; Achy-Brou, Aristide

2007-01-01

328

Hierarchical Structure in Healthy and Diseased Heart Rate Variability in Humans  

E-print Network

It is shown that the heart rate variability (HRV) in healthy and diseased humans possesses a hierarchical structure of the She-Leveque (SL) form. This structure, first found in measurements in turbulent fluid flows, implies further details in the HRV multifractal scaling. The potential of diagnosis is also discussed based on the characteristics derived from the SL hierarchy.

Emily S. C. Ching; D. C. Lin; C. Zhang

2003-12-12

329

Childhood Psychopathology and Autonomic Dysregulation: Exploring the Links Using Heart Rate Variability  

ERIC Educational Resources Information Center

Changes in cardiovascular reactivity have been used as a psychophysiological marker of various emotional states in both children and adults. Recent decades have seen increasing use of heart rate variability as a non-invasive marker of cardiac autonomic function and of central processes involved in autonomic function regulation. Developmental…

Srinivasan, Krishnamachari

2007-01-01

330

Identifying Genetic Variants for Heart Rate Variability in the Acetylcholine Pathway  

PubMed Central

Heart rate variability is an important risk factor for cardiovascular disease and all-cause mortality. The acetylcholine pathway plays a key role in explaining heart rate variability in humans. We assessed whether 443 genotyped and imputed common genetic variants in eight key genes (CHAT, SLC18A3, SLC5A7, CHRNB4, CHRNA3, CHRNA, CHRM2 and ACHE) of the acetylcholine pathway were associated with variation in an established measure of heart rate variability reflecting parasympathetic control of the heart rhythm, the root mean square of successive differences (RMSSD) of normal RR intervals. The association was studied in a two stage design in individuals of European descent. First, analyses were performed in a discovery sample of four cohorts (n?=?3429, discovery stage). Second, findings were replicated in three independent cohorts (n?=?3311, replication stage), and finally the two stages were combined in a meta-analysis (n?=?6740). RMSSD data were obtained under resting conditions. After correction for multiple testing, none of the SNPs showed an association with RMSSD. In conclusion, no common genetic variants for heart rate variability were identified in the largest and most comprehensive candidate gene study on the acetylcholine pathway to date. Future gene finding efforts for RMSSD may want to focus on hypothesis free approaches such as the genome-wide association study. PMID:25384021

Riese, Harriette; Munoz, Loretto M.; Hartman, Catharina A.; Ding, Xiuhua; Su, Shaoyong; Oldehinkel, Albertine J.; van Roon, Arie M.; van der Most, Peter J.; Lefrandt, Joop; Gansevoort, Ron T.; van der Harst, Pim; Verweij, Niek; Licht, Carmilla M. M.; Boomsma, Dorret I.; Hottenga, Jouke-Jan; Willemsen, Gonneke; Penninx, Brenda W. J. H.; Nolte, Ilja M.; de Geus, Eco J. C.; Wang, Xiaoling; Snieder, Harold

2014-01-01

331

The power spectral analysis of heart rate variability in athletes during exercise  

Microsoft Academic Search

In this study the effect of the autonomic nervous system (ANS) on heart rate variability (HRV) during dynamic exercise was assessed for 3 athletes and 7 nonathletes with power spectral analysis. The power spectrum of HRV was estimated using FFT and Burg's Maximum Entropy Method. The activities of ANS were quantified by determining the parameters such as low frequency power

K. S. Shin; H. Minamitani; S. Onishi; H. Yamazaki; M. H. Lee

1993-01-01

332

Central hemodynamic and heart rate variability parameters in athletes during different training programs  

Microsoft Academic Search

Central hemodynamic and heart rate variability (HRV) parameters were assessed in highly qualified athletes differing in the\\u000a types of their training programs at relative rest. During endurance (the endurance group, n = 27) and strength (the strength group, n = 17) trainings, the total peripheral resistance (TPR) was decreased by 15% (p = 0.003) in the endurance group and by

A. Yu. Mal’tsev; A. A. Mel’nikov; A. D. Vikulov; K. S. Gromova

2010-01-01

333

Power Spectral Analysis of Heart Rate Variability in Adolescent Male Athletes  

Microsoft Academic Search

Background: Cardiac autonomic nervous activities (CANA) deteriorate with age, obesity, sedentary life style and in various cardiac and noncardiac disease conditions. Regular physical exercise may improve CANA in health and diseases. Power spectral analysis (PSA) of Heart rate variability (HRV) is one of the most promising newer techniques to quantify CANA. Objective: To analyze HRV by Power Spectral method in

Alom M; Begum N; Ferdousi S; Begum S; Ali T

2009-01-01

334

Heart rate variability in soccer players with mitral valve prolapse or benign arrhythmia  

Microsoft Academic Search

Numerous studies have reported increased cardiac vagal activity in well endurance-trained athletes. However, no clear data exist regarding the cardiac autonomic activity in athletes with common cardiovascular findings, such as mild mitral valve prolapse (MVP) and transient benign arrhythmias. Therefore, the purpose of this study was to investigate and compare the cardiac autonomic outflow by heart rate variability (HRV) analysis

N. Koutlianos; E. Kouidi; A. Deligiannis

2004-01-01

335

Heart rate variability and autonomic activity at rest and during exercise in various physiological conditions  

Microsoft Academic Search

The rhythmic components of heart rate variability (HRV) can be separated and quantitatively assessed by means of power spectral analysis. The powers of high frequency (HF) and low frequency (LF) components of HRV have been shown to estimate cardiac vagal and sympathetic activities. The reliability of these spectral indices, as well as that of LF\\/HF ratio as a marker of

Renza Perini; Arsenio Veicsteinas

2003-01-01

336

Analysis of twenty-four hour heart rate variability in patients with panic disorder  

Microsoft Academic Search

Growing evidence suggests that alterations in autonomic function contribute to the pathophysiology of panic disorder (PD). This retrospective study employed 24-h heart rate variability (HRV) analysis of Holter records to compare autonomic function in PD patients (n=38) with healthy, age- and gender-matched controls. Both time and frequency domain measures were calculated, and a circadian rhythm analysis was performed. The SDNN

Rollin McCraty; Mike Atkinson; Dana Tomasino; William P. Stuppy

2001-01-01

337

Electrocardiogram analysis using a combination of statistical, geometric, and nonlinear heart rate variability features  

Microsoft Academic Search

ObjectiveThe paper addresses a common and recurring problem of electrocardiogram (ECG) classification based on heart rate variability (HRV) analysis. Current understanding of the limits of HRV analysis in diagnosing different cardiac conditions is not complete. Existing research suggests that a combination of carefully selected linear and nonlinear HRV features should significantly improve the accuracy for both binary and multiclass classification

Alan Jovic; Nikola Bogunovic

2011-01-01

338

An integrated diabetic index using heart rate variability signal features for diagnosis of diabetes  

Microsoft Academic Search

Electrocardiogram (ECG) signals are difficult to interpret, and clinicians must undertake a long training process to learn to diagnose diabetes from subtle abnormalities in these signals. To facilitate these diagnoses, we have developed a technique based on the heart rate variability signal obtained from ECG signals. This technique uses digital signal processing methods and, therefore, automates the detection of diabetes

U. Rajendra Acharya; Oliver Faust; S. Vinitha Sree; Dhanjoo N. Ghista; Sumeet Dua; Paul Joseph; V. I. Thajudin Ahamed; Nittiagandhi Janarthanan; Toshiyo Tamura

2011-01-01

339

The use of intraallelic variability for testing neutrality and estimating population growth rate.  

PubMed Central

To better understand the forces affecting individual alleles, we introduce a method for finding the joint distribution of the frequency of a neutral allele and the extent of variability at closely linked marker loci (the intraallelic variability). We model three types of intraallelic variability: (a) the number of nonrecombinants at a linked biallelic marker locus, (b) the length of a conserved haplotype, and (c) the number of mutations at a linked marker locus. If the population growth rate is known, the joint distribution provides the basis for a test of neutrality by testing whether the observed level of intraallelic variability is consistent with the observed allele frequency. If the population growth rate is unknown but neutrality can be assumed, the joint distribution provides the likelihood of the growth rate and leads to a maximum-likelihood estimate. We apply the method to data from published data sets for four loci in humans. We conclude that the Delta32 allele at CCR5 and a disease-associated allele at MLH1 arose recently and have been subject to strong selection. Alleles at PAH appear to be neutral and we estimate the recent growth rate of the European population to be approximately 0.027 per generation with a support interval of (0.017-0.037). Four of the relatively common alleles at CFTR also appear to be neutral but DeltaF508 appears to be significantly advantageous to heterozygous carriers. PMID:11404347

Slatkin, M; Bertorelle, G

2001-01-01

340

Particulate matter and heart rate variability among elderly retirees: the Baltimore 1998 PM study  

Microsoft Academic Search

This study investigates the relationship between ambient fine particle pollution and impaired cardiac autonomic control in the elderly. Heart rate variability (HRV) among 56 elderly (mean age 82) nonsmoking residents of a retirement center in Baltimore County, Maryland, was monitored for 4 weeks, from July 27 through August 22, 1998. The weather was seasonally mild (63–84°F mean daily temperature) with

JOHN CREASON; LUCAS NEAS; DEBRA WALSH; RON WILLIAMS; LINDA SHELDON; DUANPING LIAO; CARL SHY

2001-01-01

341

Multiscale multifractal analysis of heart rate variability recordings with a large number of occurrences of arrhythmia  

NASA Astrophysics Data System (ADS)

Human heart rate variability, in the form of time series of intervals between heart beats, shows complex, fractal properties. Recently, it was demonstrated many times that the fractal properties vary from point to point along the series, leading to multifractality. In this paper, we concentrate not only on the fact that the human heart rate has multifractal properties but also that these properties depend on the time scale in which the multifractality is measured. This time scale is related to the frequency band of the signal. We find that human heart rate variability appears to be far more complex than hitherto reported in the studies using a fixed time scale. We introduce a method called multiscale multifractal analysis (MMA), which allows us to extend the description of heart rate variability to include the dependence on the magnitude of the variability and time scale (or frequency band). MMA is relatively immune to additive noise and nonstationarity, including the nonstationarity due to inclusions into the time series of events of a different dynamics (e.g., arrhythmic events in sinus rhythm). The MMA method may provide new ways of measuring the nonlinearity of a signal, and it may help to develop new methods of medical diagnostics.

Giera?towski, J.; ?ebrowski, J. J.; Baranowski, R.

2012-02-01

342

Fractal Analysis of Heart Rate Variability and Mortality After an Acute Myocardial Infarction  

Microsoft Academic Search

The recently developed fractal analysis of heart rate (HR) variability has been suggested to provide prognostic information about patients with heart failure. This pro- spective multicenter study was designed to assess the prognostic significance of fractal and traditional HR vari- ability parameters in a large, consecutive series of sur- vivors of an acute myocardial infarction (AMI). A con- secutive series

Jari M. Tapanainen; Poul Erik; Bloch Thomsen; Lars Køber; Christian Torp-Pedersen; Timo H. Makikallio; Kai S. Lindgren; Heikki V. Huikuri

2002-01-01

343

HEART RATE VARIABILITY IN RODENTS ? USES AND CAVEATS IN TOXICOLOGICAL STUDIES  

EPA Science Inventory

Heart rate variability (HRV) is a measure of cardiac pacing dynamics that has recently garnered a great deal of interest in environmental health studies. While the use of these measures has become popular, much uncertainty remains in the interpretation of results, both in terms ...

344

Discrete Scale Invariance in the Cascade Heart Rate Variability Of Healthy Humans  

E-print Network

Evidence of discrete scale invariance (DSI) in daytime healthy heart rate variability (HRV) is presented based on the log-periodic power law scaling of the heart beat interval increment. Our analysis suggests multiple DSI groups and a dynamic cascading process. A cascade model is presented to simulate such a property.

Lin, D C

2004-01-01

345

Improved Heart Rate Variability Signal Analysis from the Beat Occurrence Times According to the IPFM Model  

Microsoft Academic Search

The heart rate variability (HRV) is an extended tool to analyze the mechanisms controlling the cardiovascular system. In this paper, the integral pulse frequency modulation model (IPFM) is assumed. It generates the beat occurrence times from a modulating signal. This signal is thought to represent the autonomic nervous system action, mostly studied in its frequency components. Different spectral estimation methods

Javier Mateo; Pablo Laguna

2000-01-01

346

Independent and incremental prognostic value of heart rate variability in patients with chronic heart failure  

Microsoft Academic Search

Background Decreased heart rate variability (HRV), indicating derangement in cardiac autonomic control, has been reported in patients with chronic heart failure. However, the independent and incremental prognostic value of HRV over clinical data and measures of left ventricular dysfunction has been less thoroughly investigated. This study was designed to evaluate the predictive value of HRV and Poincaré plots as assessed

Domenico Bonaduce; Mario Petretta; Fortunato Marciano; Maria L. E. Vicario; Claudio Apicella; Maria A. E. Rao; Emanuele Nicolai; Massimo Volpe

1999-01-01

347

Association of hyperglycemia with reduced heart rate variability (The Framingham Heart Study)  

Microsoft Academic Search

This study was designed to examine the association of heart rate variability (HRV) with blood glucose levels in a large community-based population. Previous reports have shown HRV to be reduced in diabetics, suggesting the presence of abnormalities in neural regulatory mechanisms. There is scant information about HRV across the spectrum of blood glucose levels in a population-based cohort. One thousand

Jagmeet P Singh; Martin G Larson; Christopher J O’Donnell; Peter F Wilson; Hisako Tsuji; Donald M Lloyd-Jones; Daniel Levy

2000-01-01

348

Evaluation of Association Between Demographic Variables with Smoking Rate in Rural Cultures  

Microsoft Academic Search

Objective-Smoking remains the single most important modifiable risk factor for cardiovascular disease and also the leading preventable cause of death. There have been a good many studes on the association between demographic variables and smoking rate in urban areas; however, very little has been done in rural areas. Methods- This cross-sectional study was conducted on 1375 individuals randomly selected from

H. Farshidi; M. Nikparvar; S. Abedini; D. Saed

349

Evaluation of Heart Rate Variability by Using Wavelet Transform and a Recurrent Neural Network.  

National Technical Information Service (NTIS)

The purpose of this paper is to evaluate the physical and mental stress based on the physiological index, and a new evaluation method of heart rate variability is proposed. This method combines the wavelet transform with a recurrent neural network. The fe...

O. Fukuda, Y. Nagata, K. Homma, T. Tsuji

2001-01-01

350

RELIABILITY AND QUALITY OF ULTRASOUND MEASUREMENTS OF FETAL HEART RATE VARIABILITY  

Microsoft Academic Search

This work was aimed at assessment of usability of Doppler ultrasound method for the analysis of fetal heart rate variability at a level of single heart beats. The purpose of this study was to check if today fetal monitors provide the signal of accuracy comparable with an electrocardiography method. The virtual instrumentation software for measurement system and processing of acquired

Janusz WRÓBEL; Tomasz KUPKA; Adam MATONIA; Krzysztof HOROBA

2003-01-01

351

EXPOSURE TO CONCENTRATED AMBIENT PARTICLES IN DETROIT ALTERS HEART RATE VARIABILITY IN SPONTANEOUSLY HYPERTENSIVE RATS  

EPA Science Inventory

Elevations in airborne particulate matter (PM) are linked to increased mortality and morbidity in humans with cardiopulmonary disease. Clinical studies show that PM is associated with altered heart rate variability (HRV) and suggests that loss of autonomic control may underlie ca...

352

Ethnicity and Type D personality as predictors of heart rate variability  

Microsoft Academic Search

This study examined the relationship between Type D personality and heart rate variability (HRV) during three guided imagery experiences (baseline, stressful, and uplifting) in a non-medical sample. The interaction between African-American ethnicity and Type D personality was predictive of both low and high frequency HRV during stressful imagery experiences. The importance of identifying group influences when assessing psychological and cardiovascular

Luci A. Martin; Joseph A. Doster; Joseph W. Critelli; Paul L. Lambert; Michael Purdum; Catherine Powers; Michael Prazak

2010-01-01

353

Bilateral Hegu Acupoints Have the Same Effect on the Heart Rate Variability of the Healthy Subjects  

PubMed Central

Background. The specificity of acupuncture points (acupoints) is one of the key concepts in traditional acupuncture theory, but the question of whether there is adequate scientific evidence to prove or disprove specificity has been vigorously debated in recent years. Acupoint laterality is an important aspect of acupoint specificity. Data is particularly scarce regarding the laterality of the same channel, namesake acupoint located on opposite sides of the body. Our previous study results suggest that Neiguan acupoint (PC6) has the laterality. The aim of this study was to investigate whether Hegu (LI4) also has laterality from the perspective of heart rate variability. Methods. A total of twenty-eight healthy female volunteers were recruited for this study and were randomly separated into the group I (n = 14) and the group II (n = 14) according to the register order. In the group I, left LI4 was stimulated in the first epoch and the right LI4 was stimulated in the second epoch. In the group II, right LI4 was stimulated in the first epoch and left LI4 was stimulated in the second epoch. Electrocardiogram was recorded and heart rate variability was analyzed. Results. The results show that there were no significant differences of heart rate variablity between the group I and the group II in the time domain and in the frequency domain. Conclusions. Bilateral Hegu acupoints have the same effect on the heart rate variability of the healthy subjects. PMID:25057272

Yuying, Tian; Shuyong, Jia; Wenting, Zhou; Weibo, Zhang

2014-01-01

354

The Effect of Listening to Specific Musical Genre Selections on Measures of Heart Rate Variability  

ERIC Educational Resources Information Center

University students (N = 30) individually listened to the Billboard 100 top-ranked musical selection for their most and least liked musical genre. Two minutes of silence preceded each musical listening condition, and heart rate variability (HRV) was recorded throughout. All HRV measures decreased during music listening as compared with silence.…

Orman, Evelyn K.

2011-01-01

355

Metabolic Syndrome and Short-Term Heart Rate Variability in Adults with Intellectual Disabilities  

ERIC Educational Resources Information Center

Metabolic syndrome (MetS) increases the risk of cardiovascular events. Heart rate variability (HRV) represents autonomic functioning, and reduced HRV significantly increases cardiovascular mortality. The aims of the present paper are to assess the prevalence of MetS in adults with intellectual disabilities (ID), the difference in short-term HRV…

Chang, Yaw-Wen; Lin, Jin-Ding; Chen, Wei-Liang; Yen, Chia-Feng; Loh, Ching-Hui; Fang, Wen-Hui; Wu, Li-Wei

2012-01-01

356

Effect of Heart Rate Variability on Defensive Reaction and Eating Disorder Symptomatology in Chocolate Cravers  

Microsoft Academic Search

The study examines the effect of heart rate variability (HRV) on the cardiac defence response (CDR) and eating disorder symptomatology in chocolate cravers. Female chocolate cravers (n = 36) and noncravers (n = 36) underwent a psychophysiological test to assess their HRV during a 5-min rest period, followed by three trials to explore the CDR, elicited by an intense white

Sonia Rodríguez-Ruiz; Elisabeth Ruiz-Padial; Nieves Vera; Carmen Fernández; Lourdes Anllo-Vento; Jaime Vila

2009-01-01

357

Intra-task variability of trunk coordination during a rate-controlled bipedal dance jump  

Microsoft Academic Search

In this study, we investigated trunk coordination during rate-controlled bipedal vertical dance jumps. The aims of the study were to investigate the pattern of coordination and the magnitude of coordination variability within jump phases and relative to phase-defining events during the jump. Lumbar and thoracic kinematics were collected from seven dancers during a series of jumps at 95 beats per

Jo Armour Smith; Adam Siemienski; John M. Popovich Jr; Kornelia Kulig

2011-01-01

358

Intra-task variability of trunk coordination during a rate-controlled bipedal dance jump  

Microsoft Academic Search

In this study, we investigated trunk coordination during rate-controlled bipedal vertical dance jumps. The aims of the study were to investigate the pattern of coordination and the magnitude of coordination variability within jump phases and relative to phase-defining events during the jump. Lumbar and thoracic kinematics were collected from seven dancers during a series of jumps at 95 beats per

Jo Armour Smith; Adam Siemienski; John M. Popovich Jr; Kornelia Kulig

2012-01-01

359

Cartesian thrust allocation algorithm with variable direction thrusters, turn rate limits and singularity avoidance  

E-print Network

thrust slowly and/or reverse the direction of the generated thrust, minimizing the power consumptionCartesian thrust allocation algorithm with variable direction thrusters, turn rate limits Abstract-- The literature on thrust allocation algorithms that is currently available usually focuses

Johansen, Tor Arne

360

Heart Rate Variability in Patients with Sleep-Related Breathing Disorders  

Microsoft Academic Search

The increased mortality among patients with obstructive sleep apnea syndrome has been explained in part by the increased incidence of arterial and pulmonary hypertension. A decreased heart rate variability (HRV) has been shown to be associated with an increased mortality as well. We investigated 53 patients, admitted to the hospital for chest pain for sleep-related breathing disorders (SRBD) with an

Torsten Bauer; Santiago Ewig; Harald Schäfer; Elvira Jelen; Hayder Omran; Berndt Lüderitz

1996-01-01

361

Heart rate variability in sarcoidosis: a frequency domain analysisB  

Microsoft Academic Search

Background: Little is known about autonomic dysfunction in patients with sarcoidosis. Heart rate variability (HRV) studies provide information regarding sympathetic and vagal tone and are both noninvasive and relatively simple to perform. The objective of this study was to compare HRV in sarcoidosis patients and in healthy controls. Methods: We prospectively analyzed data from 12 sarcoidosis patients and 12 healthy

Israel Heller; Aharon Isakov; Ofer Barnea; Joel Greif; Marcel Topilsky

362

Combined Heart Rate Variability and Pulse Oximetry Biofeedback for Chronic Obstructive Pulmonary Disease: Preliminary Findings  

Microsoft Academic Search

The purpose of this study was to examine the feasibility of an intervention that included heart rate variability (HRV) biofeedback and walking with pulse oximetry feedback to improve functioning and quality of life for patients with chronic obstructive pulmonary disease (COPD). Twenty patients with COPD participated in 5 weekly sessions of HRV biofeedback and 4 weekly sessions of walking practice

Nicholas D. Giardino; Leighton Chan; Soo Borson

2004-01-01

363

GENDER-RELATED DIFFERENCES IN NONLINEAR INDICES OF HEART RATE VARIABILITY  

Microsoft Academic Search

The effect of day-night variations was evaluated in both a female and a male population of healthy subjects. A total of 239 subjects were included in this study, of which 119 male and 120 female. 24 hour Holter recordings were used to analyze heart rate variability. Power spectral indices (total power, low and high frequency power) were calculated together with

F. Beckers; D. Ramaekers; A. E. Aubert

2001-01-01

364

The Chronic Effect of Rilmenidine on Heart Rate Variability in Patients with Mild Hypertension  

Microsoft Academic Search

The purpose of this study was to evaluate the chronic effect of rilmenidine on time domain indexes of heart rate variability in patients with mild hypertension. Twenty patients (12 males, eight females; mean age, 47 yr; age range, 38-55 yr), with untreated and newly diagnosed mild hypertension were studied. There was no evidence of diseases other than hypertension. All patients

Beyhan Eryonucu; Mehmet S. Ulgen; Mehmet Bilge; Niyazi Güler; Ahmet Güne?

2002-01-01

365

Cardiac denervation occurs independent of orthostatic hypotension and impaired heart rate variability in Parkinson's disease  

Microsoft Academic Search

Patients with idiopathic Parkinson's disease (PD) have impaired sympathetically mediated neurocirculatory innervation. Here we analyzed the correlation between cardiac 123I-metaiodobenzylguanidine (MIBG) uptake, orthostatic hypotension and heart rate variability in treated patients with PD. Orthostatic hypotension (OH) as a hallmark of sympathetic neurocirculatory failure was found with a high prevalence in PD. PD is known to affect cardiac innervation, resulting in

C.-A. Haensch; H. Lerch; J. Jörg; S. Isenmann

2009-01-01

366

Exposure to wood smoke increases arterial stiffness and decreases heart rate variability in humans  

PubMed Central

Background Emissions from biomass combustion are a major source of indoor and outdoor air pollution, and are estimated to cause millions of premature deaths worldwide annually. Whilst adverse respiratory health effects of biomass exposure are well established, less is known about its effects on the cardiovascular system. In this study we assessed the effect of exposure to wood smoke on heart rate, blood pressure, central arterial stiffness and heart rate variability in otherwise healthy persons. Methods Fourteen healthy non-smoking subjects participated in a randomized, double-blind crossover study. Subjects were exposed to dilute wood smoke (mean particle concentration of 314±38 ?g/m3) or filtered air for three hours during intermittent exercise. Heart rate, blood pressure, central arterial stiffness and heart rate variability were measured at baseline and for one hour post-exposure. Results Central arterial stiffness, measured as augmentation index, augmentation pressure and pulse wave velocity, was higher after wood smoke exposure as compared to filtered air (p < 0.01 for all), and heart rate was increased (p < 0.01) although there was no effect on blood pressure. Heart rate variability (SDNN, RMSSD and pNN50; p = 0.003, p < 0.001 and p < 0.001 respectively) was decreased one hour following exposure to wood smoke compared to filtered air. Conclusions Acute exposure to wood smoke as a model of exposure to biomass combustion is associated with an immediate increase in central arterial stiffness and a simultaneous reduction in heart rate variability. As biomass is used for cooking and heating by a large fraction of the global population and is currently advocated as a sustainable alternative energy source, further studies are required to establish its likely impact on cardiovascular disease. Trial registration ClinicalTrials.gov, NCT01488500 PMID:23742058

2013-01-01

367

Testing the Effect of Metabolic Rate on DNA Variability at the IntraSpecific Level  

Microsoft Academic Search

We tested the metabolic rate hypothesis (whereby rates of mtDNA evolution are postulated to be mediated primarily by mutagenic by-products of respiration) by examining whether mass-specific metabolic rate was correlated with root-to-tip distance on a set of mtDNA trees for the springtail Cryptopygus antarcticus travei from sub-Antarctic Marion Island.Using Bayesian analyses and a novel application of the comparative phylogenetic method,

Angela McGaughran; Barbara R. Holland

2010-01-01

368

A variable data rate satellite user terminal for multimedia communication able to react against weather impairments (DASIA 2002)  

NASA Astrophysics Data System (ADS)

In the frame of Ground Segment products LABEN - a Finmeccanica Company - is developing an advanced Satellite User Terminal for Multimedia Communication able to react against weather impairments. LABEN has been responsible during the Phase B for the design of the Resource Sharing Experiment (RSE) Earth Terminal of the DAVID Program (ASI). The RSE shall demonstrate conceptual and operational feasibility of the variable data rate link with a LEO satellite (DAVID). This abstract wants to provide a brief description of the proposed system and to outline the near future evolution of these Multimedia Earth Terminals linked to new services and applications.

Bux, W.; Ferrari, M.; D'Ambrosio, A.

2002-07-01

369

26 CFR 26.2641-1 - Applicable rate of tax.  

Code of Federal Regulations, 2011 CFR

...2641-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) ESTATE AND GIFT TAXES GENERATION-SKIPPING TRANSFER TAX REGULATIONS UNDER THE TAX REFORM ACT OF 1986 § 26.2641-1 Applicable rate of tax. The...

2011-04-01

370

Effects of variability and rate on battery charge storage and lifespan  

NASA Astrophysics Data System (ADS)

The growing prevalence of hybrid and electric vehicles, intermittent renewable energy sources, and other complex power systems has triggered a rapid increase in demand for energy storage. Unlike portable electronic devices, whose batteries can be recharged according to a pre-determined protocol simply by plugging them into the wall, many of these applications are characterized by highly variable charge and demand profiles. The central objective of this work is to assess the impact of power distribution and frequency on battery behavior in order to improve overall system efficiency and lifespan in these variable power applications. We first develop and experimentally verify a model to describe the trade-off between battery charging power and energy stored to assess how varying power input affects battery efficiency. This relationship is influenced both by efficiency losses at high powers and by premature voltage cutoffs, which contribute to incomplete battery charging and discharging. We experimentally study the impact of variable power on battery aging in lead-acid, nickel metal hydride, lithium-ion and lithium iron phosphate batteries. As a case study we focus on off-grid wind systems, and analyze the impact of both power distribution and frequency on charge acceptance and degradation in each of these chemistries. We suggest that lithium iron phosphate batteries may be more suitable for off-grid electrification projects than standard lead-acid batteries. We experimentally assess the impact of additional variable charging parameters on battery performance, including the interplay between efficiency, frequency of power oscillations, state-of-charge, incomplete charging and path dependence. We develop a frequency-domain model for hybrid energy storage systems that couples non-stationary frequency analysis of variable power signals to a frequency-based metric for energy storage device performance. The experimental and modeling work developed herein can be utilized to optimize energy storage system design and control algorithms for variable power applications.

Krieger, Elena Marie

371

A Conceptual Evaluation of Sustainable Variable-Rate Agricultural Residue Removal  

SciTech Connect

Agricultural residues have near-term potential as a feedstock for bioenergy production, but their removal must be managed carefully to maintain soil health and productivity. Recent studies have shown that subfield scale variability in soil properties (e.g., slope, texture, and organic matter content) that affect grain yield significantly affect the amount of residue that can be sustainably removed from different areas within a single field. This modeling study examines the concept of variable-rate residue removal equipment that would be capable of on-the-fly residue removal rate adjustments ranging from 0 to 80%. Thirteen residue removal rates (0% and 25–80% in 5% increments) were simulated using a subfield scale integrated modeling framework that evaluates residue removal sustainability considering wind erosion, water erosion, and soil carbon constraints. Three Iowa fields with diverse soil, slope, and grain yield characteristics were examined and showed sustainable, variable-rate agricultural residue removal that averaged 2.35, 7.69, and 5.62 Mg ha-1, respectively. In contrast, the projected sustainable removal rates using rake and bale removal for the entire field averaged 0.0, 6.40, and 5.06 Mg ha-1, respectively. The modeling procedure also projected that variable-rate residue harvest would result in 100% of the land area in all three fields being managed in a sustainable manner, whereas Field 1 could not be sustainably managed using rake and bale removal, and only 83 and 62% of the land area in Fields 2 and 3 would be managed sustainably using a rake and bale operation for the entire field. In addition, it was found that residue removal adjustments of 40 to 65% are sufficient to collect 90% of the sustainably available agricultural residue.

David J. Muth, Jr.; K. M. Bryden

2012-10-01

372

Do physiological and pathological stresses produce different changes in heart rate variability?  

PubMed Central

Although physiological (e.g., exercise) and pathological (e.g., infection) stress affecting the cardiovascular system have both been documented to be associated with a reduction in overall heart rate variability (HRV), it remains unclear if loss of HRV is ubiquitously similar across different domains of variability analysis or if distinct patterns of altered HRV exist depending on the stressor. Using Continuous Individualized Multiorgan Variability Analysis (CIMVA™) software, heart rate (HR) and four selected measures of variability were measured over time (windowed analysis) from two datasets, a set (n = 13) of patients who developed systemic infection (i.e., sepsis) after bone marrow transplant (BMT), and a matched set of healthy subjects undergoing physical exercise under controlled conditions. HR and the four HRV measures showed similar trends in both sepsis and exercise. The comparison through Wilcoxon sign-rank test of the levels of variability at baseline and during the stress (i.e., exercise or after days of sepsis development) showed similar changes, except for LF/HF, ratio of power at low (LF) and high (HF) frequencies (associated with sympathovagal modulation), which was affected by exercise but did not show any change during sepsis. Furthermore, HRV measures during sepsis showed a lower level of correlation with each other, as compared to HRV during exercise. In conclusion, this exploratory study highlights similar responses during both exercise and infection, with differences in terms of correlation and inter-subject fluctuations, whose physiologic significance merits further investigation. PMID:23908633

Bravi, Andrea; Green, Geoffrey; Herry, Christophe; Wright, Heather E.; Longtin, Andre; Kenny, Glen P.; Seely, Andrew J. E.

2013-01-01

373

Heart rate variability during REM and non-REM sleep in preterm neonates with and without abnormal cardiorespiratory events  

E-print Network

Heart rate variability during REM and non-REM sleep in preterm neonates with and without abnormal rate variability Preterm neonates Nonlinear analysis Sleep state Noise titration Aim: Analyse heart: To quantify nonlinear HRV, the numerical noise titration technique is used, adapted to neonatal heart rate

374

Abstract--Heart rate variability (HRV) is frequently used to measure autonomic nervous system (ANS) activity. However,  

E-print Network

1 of 4 Abstract--Heart rate variability (HRV) is frequently used to measure autonomic nervous frequency (HF) ratio with little change in mean heart rate. Results suggest that nicotine affects both components may yield erroneous results. Keywords--Autonomic regulation, heart rate variability, Lomb

375

On the Accretion Rates of SW Sextantis Nova-like Variables  

NASA Astrophysics Data System (ADS)

We present accretion rates for selected samples of nova-like variables having IUE archival spectra and distances uniformly determined using an infrared method by Knigge. A comparison with accretion rates derived independently with a multiparametric optimization modeling approach by Puebla et al. is carried out. The accretion rates of SW Sextantis nova-like systems are compared with the accretion rates of non-SW Sextantis systems in the Puebla et al. sample and in our sample, which was selected in the orbital period range of three to four and a half hours, with all systems having distances using the method of Knigge. Based upon the two independent modeling approaches, we find no significant difference between the accretion rates of SW Sextantis systems and non-SW Sextantis nova-like systems insofar as optically thick disk models are appropriate. We find little evidence to suggest that the SW Sex stars have higher accretion rates than other nova-like cataclysmic variables (CVs) above the period gap within the same range of orbital periods.

Ballouz, Ronald-Louis; Sion, Edward M.

2009-06-01

376

Experiences with leak rate calculations methods for LBB application  

SciTech Connect

In this paper, three leak rate computer programs for the application of leak before break analysis are described and compared. The programs are compared to each other and to results of an HDR Reactor experiment and two real crack cases. The programs analyzed are PIPELEAK, FLORA, and PICEP. Generally, the different leak rate models are in agreement. To obtain reasonable agreement between measured and calculated leak rates, it was necessary to also use data from detailed crack investigations.

Grebner, H.; Kastner, W.; Hoefler, A.; Maussner, G. [and others

1997-04-01

377

Segmentation and classification of capnograms: application in respiratory variability analysis.  

PubMed

Variability analysis of respiratory waveforms has been shown to provide key insights into respiratory physiology and has been used successfully to predict clinical outcomes. The current standard for quality assessment of the capnogram signal relies on a visual analysis performed by an expert in order to identify waveform artifacts. Automated processing of capnograms is desirable in order to extract clinically useful features over extended periods of time in a patient monitoring environment. However, the proper interpretation of capnogram derived features depends upon the quality of the underlying waveform. In addition, the comparison of capnogram datasets across studies requires a more practical approach than a visual analysis and selection of high-quality breath data. This paper describes a system that automatically extracts breath-by-breath features from capnograms and estimates the quality of individual breaths derived from them. Segmented capnogram breaths were presented to expert annotators, who labeled the individual physiological breaths into normal and multiple abnormal breath types. All abnormal breath types were aggregated into the abnormal class for the purpose of this manuscript, with respiratory variability analysis as the end-application. A database of 11?526 breaths from over 300 patients was created, comprising around 35% abnormal breaths. Several simple classifiers were trained through a stratified repeated ten-fold cross-validation and tested on an unseen portion of the labeled breath database, using a subset of 15 features derived from each breath curve. Decision Tree, K-Nearest Neighbors (KNN) and Naive Bayes classifiers were close in terms of performance (AUC of 90%, 89% and 88% respectively), while using 7, 4 and 5 breath features, respectively. When compared to airflow derived timings, the 95% confidence interval on the mean difference in interbreath intervals was ± 0.18 s. This breath classification system provides a fast and robust pre-processing of continuous respiratory waveforms, thereby ensuring reliable variability analysis of breath-by-breath parameter time series. PMID:25389703

Herry, C L; Townsend, D; Green, G C; Bravi, A; Seely, A J E

2014-12-01

378

Variable reluctance harvester for applications in railroad monitoring  

NASA Astrophysics Data System (ADS)

We present the design, realization, and testing of a variable reluctance energy harvester for the detection of moving ferromagnetic parts, e.g. the wheels of a train while passing over a train passage detector. Measurements were done to determine the output voltage, the energy output per event and the power output with the frequency of the moving ferromagnetic body. Results are compared with finite element analysis (FEA) to estimate the change in magnetic flux and the output voltages. A maximum energy output of 131 ?J per pulse was measured for a simulated condition of a train wheel passing with a speed of 81.5 km/h, which results in a mean output power of 5.9 mW, with a spacing of 10 mm between wheel and the reluctance circuit. This shows that the variable reluctance principle, a well-known method used for numerous sensor applications, is also a comfortable, energy-autonomous and reliable method to detect passing train wheels or other moving ferromagnetic parts, with a simple setup and fairly high useable output power.

Kroener, M.; Ravindran, S. K. T.; Woias, P.

2013-12-01

379

Cepheid variables and their application to the cosmological distance scale  

NASA Astrophysics Data System (ADS)

In the current era of "precision cosmology", measuring the expansion rate of the Universe (Hubble constant, or H 0) more accurately and precisely helps to better constrain the properties of dark energy. Cepheid-based distances are a critical step in the Extragalactic Distance Scale and have been recently used to measure H 0 with a total uncertainty of only 3.4%. I will present my work on Cepheid variables in three different galaxies as part of this effort. NGC 4258 is a galaxy with a very precise and accurate distance (3% uncertainty) based on radio interferometric observations of water masers orbiting its central massive black hole. Therefore, it can be used to obtain a robust absolute calibration of the Cepheid Period-Luminosity relation. I analyzed observations of NGC 4258 obtained at Gemini North over four years and increased the number of long-period Cepheids (P>45 days) known in this galaxy. NGC 5584 was the host of type Ia SN 2007af. I applied a difference imaging technique to Hubble Space Telescope (HST) observations of this galaxy and discovered several hundred Cepheids. I compared my results with previous work based on traditional PSF photometry. The distance estimates of the two samples matched within the errors of the measurements, and so the difference imaging technique was a success. Additionally, I validated the first "white-light" variability search with the HST F350LP filter for discovering Cepheids. NGC 4921 is located in the heart of the Coma cluster at a distance of about 100Mpc. I conducted a search for Cepheid variables using HST, extending the reach of Hubble by a factor of 3 relative to previous Cepheid work. Since Coma is in the Hubble flow, this approach eliminates the need for a secondary distance indicator and enables a direct determination of H0 based exclusively on a Cepheid distance. I present preliminary results from this challenging project.

Hoffman, Samantha Leigh

380

Necessary conditions for the optimality of variable rate residual vector quantizers  

NASA Technical Reports Server (NTRS)

Residual vector quantization (RVQ), or multistage VQ, as it is also called, has recently been shown to be a competitive technique for data compression. The competitive performance of RVQ reported in results from the joint optimization of variable rate encoding and RVQ direct-sum code books. In this paper, necessary conditions for the optimality of variable rate RVQ's are derived, and an iterative descent algorithm based on a Lagrangian formulation is introduced for designing RVQ's having minimum average distortion subject to an entropy constraint. Simulation results for these entropy-constrained RVQ's (EC-RVQ's) are presented for memory less Gaussian, Laplacian, and uniform sources. A Gauss-Markov source is also considered. The performance is superior to that of entropy-constrained scalar quantizers (EC-SQ's) and practical entropy-constrained vector quantizers (EC-VQ's), and is competitive with that of some of the best source coding techniques that have appeared in the literature.

Kossentini, Faouzi; Smith, Mark J. T.; Barnes, Christopher F.

1993-01-01

381

Power spectrum analysis of fetal heart rate variability using the abdominal maternal electrocardiogram.  

PubMed

A signal analysis procedure is described for obtaining the power spectrum of the fetal and maternal heart rates as recorded from the abdomen. This technique, which includes the subtraction of an averaged maternal ECG waveform using a cross-correlation function and the fast Fourier transform algorithm, enables the detection of all the fetal QRS complexes in spite of their coincidence with the maternal ECGs. The power spectrum of the fetal heart rates (FHR) obtained from 15 women at 32-41 weeks gestation were studied and two indices were measured which are related to the long term and short term variabilities in the FHR signal. It was found that quantitative evaluation of the FHR variability can be obtained using power spectrum analysis. PMID:2319767

Abboud, S; Sadeh, D

1990-03-01

382

A New Approach to Detect Congestive Heart Failure Using Short-Term Heart Rate Variability Measures  

PubMed Central

Heart rate variability (HRV) analysis has quantified the functioning of the autonomic regulation of the heart and heart's ability to respond. However, majority of studies on HRV report several differences between patients with congestive heart failure (CHF) and healthy subjects, such as time-domain, frequency domain and nonlinear HRV measures. In the paper, we mainly presented a new approach to detect congestive heart failure (CHF) based on combination support vector machine (SVM) and three nonstandard heart rate variability (HRV) measures (e.g. SUM_TD, SUM_FD and SUM_IE). The CHF classification model was presented by using SVM classifier with the combination SUM_TD and SUM_FD. In the analysis performed, we found that the CHF classification algorithm could obtain the best performance with the CHF classification accuracy, sensitivity and specificity of 100%, 100%, 100%, respectively. PMID:24747432

Wang, Qian; Zhou, GuangMin; Wang, Ying; Jiang, Qing

2014-01-01

383

Effects of Variable Inflationary Conditions on AN Inventory Model with Inflation-Proportional Demand Rate  

NASA Astrophysics Data System (ADS)

The inflation rate in the most of the previous researches has been considered constant and well-known over the time horizon, although the future rate of inflation is inherently uncertain and unstable, and is difficult to predict it accurately. Therefore, A time varying inventory model for deteriorating items with allowable shortages is developed in this paper. The inflation rates (internal and external) are time-dependent and demand rate is inflation-proportional. The inventory level is described by differential equations over the time horizon and present value method is used. The numerical example is given to explain the results. Some particular cases, which follow the main problem, will discuss and the results will compare with the main model by using the numerical examples. It has been achieved which shortages increases considerably in comparison with the case of without variable inflationary conditions.

Mirzazadeh, Abolfazl

2009-08-01

384

Effect of high-frequency jet ventilation on heart rate variability  

Microsoft Academic Search

We investigated the effects of high-frequency jet ventilation (HFJV) on heart rate variability in nine patients during fentanyl\\u000a (10?g·kg?1) anesthesia using power spectral density analysis. ECG and arterial pressure were recorded during intermittent positive pressure\\u000a ventilation (IPPV) (tidal volume 8 ml·kg?1, respiratory rate 0.25 Hz) and during HFJV [5 Hz, 2.5 kg·(cm2)?1]. The R-R interval time series obtained were analyzed

Junken Koh; Masahide Shinzawa; Yoshihiro Kosaka

1996-01-01

385

Moderate physical exercise increases cardiac autonomic nervous system activity in children with low heart rate variability  

Microsoft Academic Search

Object Our objective was to investigate the effect of a long-term moderate exercise program on cardiac autonomic nervous system (ANS) activity in healthy children. Methods Three hundred and five children aged 6–11 years participated in a 12-month school-based exercise training program (130–140 bpm, 20 min\\/day, 5 days\\/week). Cardiac ANS activities were measured using heart rate variability (HRV) power spectral analysis in resting conditions. Following

Narumi Nagai; Taku Hamada; Tetsuya Kimura; Toshio Moritani

2004-01-01

386

Body mass index is related to autonomic nervous system activity as measured by heart rate variability  

Microsoft Academic Search

Autonomic nervous system activity is involved in body weight regulation. We assessed whether the body mass index (BMI) is related to the autonomic nervous system activity as assessed by heart rate variability (HRV). Twenty-five adult normotensive, euglycemic healthy males (M) and females (F) were studied (M\\/F=13\\/12). BMI was assessed in each individual. HRV was assessed and the domains of low

A Molfino; A Fiorentini; L Tubani; M Martuscelli; F Rossi Fanelli; A Laviano

2009-01-01

387

On-line prediction of nonstationary variable-bit-rate video traffic  

Microsoft Academic Search

In this paper, we propose a model-based bandwidth prediction scheme for variable-bit-rate (VBR) video traffic with regular group of pictures (GOP) pattern. Multiplicative ARIMA (autoregressive integrated moving-average) process called GOP ARIMA (ARIMA for GOP) is used as a base stochastic model, which consists of two key ingredients: prediction and model validity check. For traffic prediction, we deploy a Kalman filter

Sungjoo Kang; Seongjin Lee; Youjip Won; Byeongchan Seong

2010-01-01

388

Heart Rate Variability Reflects Self-Regulatory Strength, Effort, and Fatigue  

Microsoft Academic Search

Experimental research reliably demonstrates thatself-regulatorydeficitsareaconsequenceofpriorself- regulatory effort. However, in naturalistic settings, al- though people know that they are sometimes vulnerable to saying, eating, or doing the wrong thing, they cannot ac- curately gauge their capacity to self-regulate at any given time. Because self-regulation and autonomic regulation colocalize in the brain, an autonomic measure, heart rate variability (HRV), could provide an

Suzanne C. Segerstrom; Lise Solberg Nes

2007-01-01

389

Effect of meditation on scaling behavior and complexity of human heart rate variability  

E-print Network

The heart beat data recorded from samples before and during meditation are analyzed using two different scaling analysis methods. These analyses revealed that mediation severely affects the long range correlation of heart beat of a normal heart. Moreover, it is found that meditation induces periodic behavior in the heart beat. The complexity of the heart rate variability is quantified using multiscale entropy analysis and recurrence analysis. The complexity of the heart beat during mediation is found to be more.

Sarkar, A

2006-01-01

390

Agreement of two different methods for measurement of heart rate variability  

Microsoft Academic Search

.   Background: The widespread use of affordable devices with sufficient precision for measurement of heart rate variability (HRV) might\\u000a lead to early detection of abnormalities in a large number of high-risk patients and athletes. The purpose of this study was\\u000a to determine the limits of agreement of two devices for measuring HRV parameters differing in price and assumed precision.\\u000a Subjects

Martin Radespiel-Tröger; Robert Rauh; Christine Mahlke; Tim Gottschalk; Michael Mück-Weymann

2003-01-01

391

Effect of lecturing to 200 students on heart rate variability and alpha-amylase activity  

Microsoft Academic Search

The aim of this study was to examine cardiovascular [heart rate variability (HRV)] and autonomic nervous system activation\\u000a (by evaluating salivary alpha-amylase activity) that occur in professors both to, and after, the delivery of a lecture to\\u000a 200 students and to determine whether gender is an influencing factor upon response. Fifty-two participants (26 women and\\u000a 26 men) collected eight unstimulated

Edith Filaire; Hugues Portier; Alain Massart; Luis Ramat; Anna Teixeira

2010-01-01

392

Study of the Effect of Short-Time Cold Stress on Heart Rate Variability  

Microsoft Academic Search

The present work focuses on whether the heart rate variability (HRV) evaluated during the cold stress is different from that\\u000a in the control condition. In fifteen subjects (12M & 3F, aging 21–24 yrs), a fiveminute ECG record was performed in the room\\u000a temperature condition (27°C), and the other fiveminute ECG record was then measured in the cold stress during which

J.-J. Wang; C.-C. Chen

393

Spectral Analysis of Heart Rate Variability in the ICU: A Measure of Autonomic Function  

Microsoft Academic Search

Beat-to-beat heart rate variability (HRV) is a measure of autonomic nervous system activity, which can be quantified using frequency domain analysis. Despite its potential utility, routine serial analysis of HRV in an ICU setting has rarely been attempted. We have developed an automated system for real-time spectral analysis of HRV and have utilized this system to study the effect of

Robert J. Winchell; David B. Hoyt

1996-01-01

394

Power-Law Relationship of Heart Rate Variability as a Predictor of Mortality in the Elderly  

Microsoft Academic Search

Background—The prognostic role of heart rate (HR) variability analyzed from 24-hour ECG recordings in the general population is not well known. We studied whether analysis of 24-hour HR behavior is able to predict mortality in a random population of elderly subjects. Methods and Results—A random sample of 347 subjects of $65 years of age (mean, 7366 years) underwent a comprehensive

Heikki V. Huikuri; Timo H. Makikallio; K. E. Juhani Airaksinen; Tapio Seppanen; Pauli Puukka; Ismo J. Raiha; Leif B. Sourander

395

Screening of Obstructive Sleep Apnea Syndrome by Heart Rate Variability Analysis  

Microsoft Academic Search

Background—Enhanced nocturnal heart rate variability (HRV) has been evoked in sleep-related breathing disorders. However, its capacity to detect obstructive sleep apnea syndrome (OSAS) has not been systematically determined. Thus, we evaluated the discriminant power of HRV parameters in a first group of patients (G1) and validated their discriminant capacity in a second group (G2). Methods and Results—In G1, 39 of

Frederic Roche; Jean-Michel Gaspoz; Isabelle Court-Fortune; Pascal Minini; Vincent Pichot; David Duverney; Frederic Costes; Jean-Claude Barthelemy

2010-01-01

396

Short-Term Heart Rate Variability Strongly Predicts Sudden Cardiac Death in Chronic Heart Failure Patients  

Microsoft Academic Search

Background—The predictive value of heart rate variability (HRV) in chronic heart failure (CHF) has never been tested in a comprehensive multivariate model using short-term laboratory recordings designed to avoid the confounding effects of respiration and behavioral factors. Methods and Results—A multivariate survival model for the identification of sudden (presumably arrhythmic) death was developed with data from 202 consecutive patients referred

Maria Teresa La Rovere; Gian Domenico Pinna; Roberto Maestri; Andrea Mortara; Soccorso Capomolla; Oreste Febo; Roberto Ferrari; Mariella Franchini; Marco Gnemmi; Cristina Opasich; Pier Giorgio Riccardi; Egidio Traversi; Franco Cobelli

397

Orthostatic influence on heart rate and blood pressure variability in trained persons with tetraplegia  

Microsoft Academic Search

To examine the orthostatic influence on heart rate and blood pressure variability in persons with tetraplegia playing wheelchair\\u000a basketball, ten trained persons with tetraplegia, ten untrained persons with tetraplegia, and ten able-bodied participated\\u000a in this study. Spectrum analysis of the ECG R–R interval and blood-pressure on a beat-by-beat basis during head-up tilt 60°\\u000a sitting were performed. The ratio of the

Yasuko Otsuka; Norihiro Shima; Toshio Moritani; Kuniharu Okuda; Kyonosuke Yabe

2008-01-01

398

A greedy tree growing algorithm for the design of variable rate vector quantizers [image compression  

Microsoft Academic Search

A technique for directly designing a variable-rate tree-structured vector quantizer by growing the tree one node at a time rather than one layer at time is presented. The technique is a natural extension of a tree growing method for decision trees. When the tree is pruned with a generalized algorithm for optimally pruning trees, improvement is measured in the signal-to-noise

Eve A. Riskin; Robert M. Gray

1991-01-01

399

Improvement of menopausal symptoms with acupuncture not reflected in changes to heart rate variability  

Microsoft Academic Search

HypothesisStudies indicate that menopausal symptoms are relieved by acupuncture. Additional studies have suggested that acupuncture may affect heart rate variability (HRV). This paper reports a pilot study that investigated whether menopausal symptoms responded to acupuncture, and if changes in the spectral analysis of HRV, either suppression of low frequency or augmentation of high frequency bands, corresponded with symptom report.Methods\\/interventions12 healthy

Cheryl L Wright; Mikel Aickin

2011-01-01

400

Effects of dynamic resistance training on heart rate variability in healthy older women  

Microsoft Academic Search

  \\u000a Twenty healthy women aged between 65 and 74 years, trained three times a week, for 16 weeks, on a cycle ergometer, to determine\\u000a the effects of dynamic resistance training on heart rate variability (HRV). Subjects were allocated to two training groups,\\u000a high (HI, n=10) and low (LO, n=10) intensity. The HI group performed eight sets of 8 revolutions at 80% of the

Roberta Forte; Giuseppe De Vito; Francesco Figura

2003-01-01

401

Quantitative Poincaré plot analysis of heart rate variability: effect of endurance training  

Microsoft Academic Search

The aim of the study was to evaluate the effectiveness of the Poincaré plot analysis of heart rate variability (HRV) in observing endurance training-induced changes. Four 10-min manoeuvres were performed (supine lying, standing, steady state exercising and subsequent recovery) by eight control subjects before and after a short-term endurance training and by eight subjects trained for at least 3 years. HRV

Laurent Mourot; Malika Bouhaddi; Stéphane Perrey; Jean-Denis Rouillon; Jacques Regnard

2004-01-01

402

Increased heart rate variability and executive performance after aerobic training in the elderly  

Microsoft Academic Search

This study examined the effects of two short physical training programs on various parameters of heart rate variability (HRV)\\u000a and on executive performance in older people. Twenty-four sedentary men and women aged 65–78 years were randomly assigned\\u000a to an aerobic exercise program or a stretching program three times a week for 12 weeks. Resting HRV was measured in time and\\u000a frequency domains

Cédric T. Albinet; Geoffroy Boucard; Cédric A. Bouquet; Michel Audiffren

2010-01-01

403

Effect of high intensity intermittent training on heart rate variability in prepubescent children  

Microsoft Academic Search

The purpose of this study was to observe the effect of high intermittent exercise training on children’s heart rate variability\\u000a (HRV). Thirty-eight children (age 9.6 ± 1.2 years) were divided into an intermittent (IT, n = 22) and a control group (CON, n = 16). At baseline and after a 7-week training period, HRV parameters, peak oxygen consumption $$ (\\\\dot{V}{\\\\text{O}}_{{2{\\\\text{peak}}}} ) $$ and maximal aerobic velocity (MAV)

François-Xavier Gamelin; Georges Baquet; Serge Berthoin; Delphine Thevenet; Cedric Nourry; Stéphane Nottin; Laurent Bosquet

2009-01-01

404

Optimal remediation with well locations and pumping rates selected as continuous decision variables  

Microsoft Academic Search

The design of a pump-and-treat groundwater remediation system can be solved as an optimization problem. A common approach in this formulation is to minimize the total cost of the pump-and-treat system, while defining the locations and extraction or injection rates of the candidate pumping wells as continuous decision variables. With this choice, the degree of freedom added to the optimization

J. Guan; M. M. Aral

1999-01-01

405

Heart rate variability during waking and sleep in healthy males and females  

Microsoft Academic Search

Study Objectives: The study goal was to investigate autonomic activity with heart rate variability analysis during different sleep stages in males and females. Design: The study utilized a 2 Groups (males, females) X 4 States (waking, stage 2 sleep, stage 4 sleep, rapid-eye movement sleep) mixed design with one repeated, within-subjects factor (i.e., state). Setting: The study was carried out

S. Eisenbruck; Michael J. Harnish; William C. Orr; Thomas N. Lynn

1999-01-01

406

Stochastic analysis of heart rate variability and its relation to echocardiography parameters in hypertrophic cardiomyopathy patients  

Microsoft Academic Search

The heart rate variability of 10 healthy males (age 26 - 4\\/+ 3 y) and 49 patients with hypertrophic cardiomyopathy (HCM) (25 males, 24 females, age 29.5 - 11.5\\/+ 10.5 y) was studied. We applied Kramers-Moyal expansion to extract the drift and diffusion terms of the Langevin equation for the RR interval time series. These terms may be used for

M. Petelczyc; J. J. Zebrowski; R. Baranowski; L. Chojnowska

2010-01-01

407

Heart rate variability in hypertrophic obstructive cardiomyopathy: association with functional classification and left ventricular outflow gradients  

Microsoft Academic Search

Background: The aim of this study was to investigate cardiac autonomic control in patients with hypertrophic obstructive cardiomyopathy (HOCM) and to assess the indexes of heart rate variability (HRV) in relation to the clinical and echocardiographic features. Methods and results: Twenty-three patients (17 male, six female: mean age 43±11) with HOCM and 18 healthy volunteers were included. M-mode and two-dimensional

Oben Döven; Tamer Sayin; Muharrem Güldal; Remzi Karao?uz; Dervi? Oral

2001-01-01

408

Heart rate variability during dynamic exercise in elderly males and females  

Microsoft Academic Search

It has been proposed that cardiac control is altered in the elderly. Power spectral analysis of heart rate variability (HRV)\\u000a was performed on 12 male and 11 female elderly subjects (mean age 74?years) while at rest in supine and sitting positions,\\u000a and at steady states during 5?min of exercise (35–95% peak oxygen consumption, V?O2peak). There were no differences in power,

Renza Perini; Stefania Milesi; Nadine M. Fisher; David R. Pendergast; Arsenio Veicsteinas

2000-01-01

409

Analysis of long term heart rate variability: methods, 1/f scaling and implications  

NASA Technical Reports Server (NTRS)

The use of spectral techniques to quantify short term heart rate fluctuations on the order of seconds to minutes has helped define the autonomic contributions to beat-to-beat control of heart rate. We used similar techniques to quantify the entire spectrum (0.00003-1.0 Hz) of heart rate variability during 24 hour ambulatory ECG monitoring. The ECG from standard Holter monitor recordings from normal subjects was sampled with the use of a phase locked loop, and a heart rate time series was constructed at 3 Hz. Frequency analysis of the heart rate signal was performed after a nonlinear filtering algorithm was used to eliminate artifacts. A power spectrum of the entire 24 hour record revealed power that was inversely proportional to frequency, 1/f, over 4 decades from 0.00003 to 0.1 Hz (period approximately 10 hours to 10 seconds). Displaying consecutive spectra calculated at 5 minute intervals revealed marked variability in the peaks at all frequencies throughout the 24 hours, probably accounting for the lack of distinct peaks in the spectra of the entire records.

Saul, J. P.; Albrecht, P.; Berger, R. D.; Cohen, R. J.

1988-01-01

410

Association between Heart Rate Variability, Blood Pressure and Autonomic Activity in Cyclic Alternating Pattern during Sleep  

PubMed Central

Study Objectives: Cyclic alternating pattern (CAP) is frequently followed by changes in heart rate (HR) and blood pressure (BP), but the sequential associations between CAP and autonomic nerve activity have not been studied. The study aimed to reveal the precise changes in heart rate variability (HRV) during phase A of the CAP cycle. Design: Polysomnography was recorded according to the CAP Atlas (Terzano, 2002), and BP and electrocardiogram were simultaneously recorded. The complex demodulation method was used for analysis of HRV and evaluation of autonomic nerve activity. Setting: Academic sleep laboratory. Participants: Ten healthy males. Measurements and Results: The increase in HR (median [first quartile – third quartile]) for each subtype was as follows: A1, 0.64 (-0.30 to 1.69), A2, 1.44 (0.02 to 3.79), and A3, 6.24 (2.53 to 10.76) bpm (A1 vs. A2 P < 0.001, A1 vs. A3 P < 0.001, A2 vs. A3 P < 0.001). The increase in BP for each subtype was as follows: A1, 1.23 (-2.04 to 5.75), A2, 1.76 (-1.46 to 9.32), and A3, 12.51 (4.75 to 19.94) mm Hg (A1 vs. A2 P = 0.249, A1 vs. A3 P < 0.001, A2 vs. A3 P < 0.001). In all of phase A, the peak values for HR and BP appeared at 4.2 (3.5 to 5.4) and 8.4 (7.0 to 10.3) seconds, respectively, after the onset of phase A. The area under the curve for low-frequency and high-frequency amplitude significantly increased after the onset of CAP phase A (P < 0.001) and was higher in the order of subtype A3, A2, and A1 (P < 0.001). Conclusions: All phase A subtypes were accompanied with increased heart rate variability, and the largest heart rate variability was seen in subtype A3, while a tendency for less heart rate variability was seen in subtype A1. Citation: Kondo H; Ozone M; Ohki N; Sagawa Y; Yamamichi K; Fukuju M; Yoshida T; Nishi C; Kawasaki; Mori; Kanbayashi T; Izumi M; Hishikawa Y; Nishino S; Shimizu T. Association between heart rate variability, blood pressure and autonomic activity in cyclic alternating pattern during sleep. SLEEP 2014;37(1):187-194. PMID:24470707

Kondo, Hideaki; Ozone, Motohiro; Ohki, Noboru; Sagawa, Yohei; Yamamichi, Keiichirou; Fukuju, Mitsuki; Yoshida, Takeshi; Nishi, Chikako; Kawasaki, Akiko; Mori, Kaori; Kanbayashi, Takashi; Izumi, Motomori; Hishikawa, Yasuo; Nishino, Seiji; Shimizu, Tetsuo

2014-01-01

411

Association of auricular pressing and heart rate variability in pre-exam anxiety students.  

PubMed

A total of 30 students scoring between 12 and 20 on the Test Anxiety Scale who had been exhibiting an anxious state > 24 hours, and 30 normal control students were recruited. Indices of heart rate variability were recorded using an Actiheart electrocardiogram recorder at 10 minutes before auricular pressing, in the first half of stimulation and in the second half of stimulation. The results revealed that the standard deviation of all normal to normal intervals and the root mean square of standard deviation of normal to normal intervals were significantly increased after stimulation. The heart rate variability triangular index, very-low-frequency power, low-frequency power, and the ratio of low-frequency to high-frequency power were increased to different degrees after stimulation. Compared with normal controls, the root mean square of standard deviation of normal to normal intervals was significantly increased in anxious students following auricular pressing. These results indicated that auricular pressing can elevate heart rate variability, especially the root mean square of standard deviation of normal to normal intervals in students with pre-exam anxiety. PMID:25206734

Wu, Wocao; Chen, Junqi; Zhen, Erchuan; Huang, Huanlin; Zhang, Pei; Wang, Jiao; Ou, Yingyi; Huang, Yong

2013-03-25

412

Controlling Variable Emittance (MEMS) Coatings for Space Applications  

NASA Technical Reports Server (NTRS)

Small spacecraft, including micro and nanosats, as they are envisioned for future missions, will require an alternative means to achieve thermal control due to their small power and mass budgets. One of the proposed alternatives is Variable Emittance (Vari-E) Coatings for spacecraft radiators. Space Technology-5 (ST-5) is a technology demonstration mission through NASA Goddard Space Flight Center (GSFC) that will utilize Vari-E Coatings. This mission involves a constellation of three (3) satellites in a highly elliptical orbit with a perigee altitude of approximately 200 kilometers and an apogee of approximately 38,000 kilometers. Such an environment will expose the spacecraft to a wide swing in the thermal and radiation environment of the earth's atmosphere. There are three (3) different technologies associated with this mission. The three technologies are electrophoretic, electrochromic, and Micro ElectroMechanical Systems (MEMS). The ultimate goal is to make use of Van-E coatings, in order to achieve various levels of thermal control. The focus of this paper is to highlight the Vari-E Coating MEMS instrument, with an emphasis on the Electronic Control Unit responsible for operating the MEMS device. The Test & Evaluation approach, along with the results, is specific for application on ST-5, yet the information provides a guideline for future experiments and/or thermal applications on the exterior structure of a spacecraft.

Farrar, D.; Schneider, W.; Osiander, R.; Champion, J. L.; Darrin, A. G.; Douglas, Donya; Swanson, Ted D.

2003-01-01

413

Heart rate and heart rate variability in resistant versus controlled hypertension and in true versus white-coat resistance.  

PubMed

Sympathetic nervous system has an important role in resistant hypertension. Heart rate (HR) is a marker of sympathetic activity, but its association with resistant hypertension has not been assessed. We aimed to evaluate differences in HR values and variability between resistant and controlled patients and between true and white-coat resistant hypertensives (RHs). We compared office and ambulatory HR, nocturnal dip and s.d. in 14,627 RHs versus 11,951 controlled patients (on ? 3 drugs) and in 8730 true (24 h blood pressure (BP) ? 130 and/or 80 mm Hg) versus 4825 white-coat (24-h BP < 130/80 mm Hg) RHs. After adjusting for age, gender, body mass index, diabetes status and beta blocker use, HR values and variability were significantly elevated in resistant versus controlled patients and in true versus white-coat RHs. In logistic regression models, after adjustment for confounders, office HR (odds ratio for each increase in tertile: 1.337; 95% confidence interval: 1.287-1.388; P < 0.001), nocturnal dip (0.958; 0.918-0.999; P = 0.035) and night time s.d. (1.115; 1.057-1.177; P = 0.013) were all significantly associated with the presence of resistant hypertension. Moreover, night time HR (1.160; 1.065-1.265; P < 0.001), nocturnal dip (0.876; 0.830-0.925; P < 0.001) and 24-h s.d. (1.148; 1.092-1.207; P < 0.001) were all significantly associated with true resistant hypertension. In conclusion, both increased HR and variability are associated with resistant hypertension and with true resistance. These suggest the involvement of the sympathetic nervous system in the development of resistance to antihypertensive treatment. PMID:24401954

de la Sierra, A; Calhoun, D A; Vinyoles, E; Banegas, J R; de la Cruz, J J; Gorostidi, M; Segura, J; Ruilope, L M

2014-07-01

414

Assessment of cardiac autonomic functions by heart rate recovery, heart rate variability and QT dynamicity parameters in patients with acromegaly.  

PubMed

Cardiovascular complications are the most common causes of morbidity and mortality in acromegaly. However, there is little data regarding cardiac autonomic functions in these patients. Herein, we aimed to investigate several parameters of cardiac autonomic functions in patients with acromegaly compared to healthy subjects. We enrolled 20 newly diagnosed acromegalic patients (55% female, age:45.7 ± 12.6 years) and 32 age- and gender-matched healthy subjects. All participants underwent 24 h Holter recording. Heart rate recovery (HRR) indices were calculated by subtracting 1st, 2nd and 3rd minute heart rates from maximal heart rate. All patients underwent heart rate variability (HRV) and QT dynamicity analysis. Baseline characteristics were similar except diabetes mellitus and hypertension among groups. Mean HRR1 (29.2 ± 12.3 vs 42.6 ± 6.5, p = 0.001), HRR2 (43.5 ± 15.6 vs 61.1 ± 10.8, p = 0.001) and HRR3 (46.4 ± 16.2 vs 65.8 ± 9.8, p = 0.001) values were significantly higher in control group. HRV parameters as, SDNN [standard deviation of all NN intervals] (p = 0.001), SDANN [SD of the 5 min mean RR intervals] (p = 0.001), RMSSD [root square of successive differences in RR interval] (p = 0.001), PNN50 [proportion of differences in successive NN intervals >50 ms] (p = 0.001) and high-frequency [HF] (p = 0.001) were significantly decreased in patients with acromegaly; but low frequency [LF] (p = 0.046) and LF/HF (p = 0.001) were significantly higher in acromegaly patients. QTec (p = 0.009), QTac/RR slope (p = 0.017) and QTec/RR slope (p = 0.01) were significantly higher in patients with acromegaly. Additionally, there were significant negative correlation of disease duration with HRR2, HRR3, SDNN, PNN50, RMSSD, variability index. Our study results suggest that cardiac autonomic functions are impaired in patients with acromegaly. Further large scale studies are needed to exhibit the prognostic significance of impaired autonomic functions in patients with acromegaly. PMID:23553172

Dural, Muhammet; Kabakc?, Giray; C?nar, Ne?e; Erba?, Tomris; Canpolat, U?ur; Gürses, Kadri Murat; Tokgözo?lu, Lale; Oto, Ali; Kaya, Ergün Bar??; Yorgun, Hikmet; Sahiner, Levent; Da?delen, Selçuk; Aytemir, Kudret

2014-04-01

415

The interpretation of very high frequency band of instantaneous pulse rate variability during paced respiration  

PubMed Central

Background Pulse rate (PR) indicates heart beat rhythm and contains various intrinsic characteristics of peripheral regulation. Pulse rate variability (PRV) is a reliable method to assess autonomic nervous system function quantitatively as an effective alternative to heart rate variability. However, the frequency range of PRV is limited by the temporal resolution of PR based on heart rate and it is further restricted the exploration of optimal autoregulation frequency based on spectral analysis. Methods Recently, a new novel method, called instantaneous PRV (iPRV), was proposed. iPRV breaks the limitation of temporal resolution and extends the frequency band. Moreover, iPRV provides a new frequency band, called very high frequency band (VHF; 0.4-0.9 Hz). Results The results showed that the VHF indicated the influences of respiratory maneuvers (paced respiration at 6-cycle and 30-cycle) and the nonstationary condition (head-up tilt; HUT). Conclusions VHF is as a potential indication of autoregulation in higher frequency range and with peripheral regulation. It helps for the frequency exploration of cardiovascular autoregulation. PMID:24750578

2014-01-01

416

Usefulness of the heart-rate variability complex for predicting cardiac mortality after acute myocardial infarction  

PubMed Central

Background Previous studies indicate that decreased heart-rate variability (HRV) is related to the risk of death in patients after acute myocardial infarction (AMI). However, the conventional indices of HRV have poor predictive value for mortality. Our aim was to develop novel predictive models based on support vector machine (SVM) to study the integrated features of HRV for improving risk stratification after AMI. Methods A series of heart-rate dynamic parameters from 208 patients were analyzed after a mean follow-up time of 28 months. Patient electrocardiographic data were classified as either survivals or cardiac deaths. SVM models were established based on different combinations of heart-rate dynamic variables and compared to left ventricular ejection fraction (LVEF), standard deviation of normal-to-normal intervals (SDNN) and deceleration capacity (DC) of heart rate. We tested the accuracy of predictors by assessing the area under the receiver-operator characteristics curve (AUC). Results We evaluated a SVM algorithm that integrated various electrocardiographic features based on three models: (A) HRV complex; (B) 6 dimension vector; and (C) 8 dimension vector. Mean AUC of HRV complex was 0.8902, 0.8880 for 6 dimension vector and 0.8579 for 8 dimension vector, compared with 0.7424 for LVEF, 0.7932 for SDNN and 0.7399 for DC. Conclusions HRV complex yielded the largest AUC and is the best classifier for predicting cardiac death after AMI. PMID:24886422

2014-01-01

417

Evaluation of modulations in heart rate variability caused by a composition of herbal extracts.  

PubMed

The purpose of this prospective, placebo-controlled, randomized double-blind study was the examination of changes of the basic vegetative rhythms due to Cardiodoron, a composition of extracts of blossoms from Primula officinalis and Onopordon acanthium and from the herbs of Hyoscyamus niger. In its clinical use it is known as a modulating medicine in the treatment of functional disturbances of the cardiovascular system. With use of Holter monitoring, 24-h ECG recordings were obtained from 100 healthy subjects of whom 50 took the composition and 50 a placebo. Heart rate variability was evaluated from the 24-h ECGs by means of a power spectral analysis based on the Fast Fourier Transformation (FFT). Regulative influences on the rhythmic system due to the medicine were found. After four weeks of medication half of the verum group showed a tendency to an increased variability in the low and high frequency range at night (LFn: 0.04-0.15 Hz, HFn: 0.15-0.4 Hz) in contrast to the placebo group. The mean heart rate at night (HRn) showed a tendency towards a normalization in the verum group: in subjects with a low HRn the heart rate was increased and in subjects with a high HRn the heart rate was decreased. This effect could not be observed in the placebo group. After two further weeks without any medication this difference between verum and placebo was abolished. PMID:10858869

Cysarz, D; Schürholz, T; Bettermann, H; Kümmell, H C

2000-05-01

418

Defining asymmetry in heart rate variability signals using a Poincaré plot.  

PubMed

The asymmetry in heart rate variability is a visibly obvious phenomenon in the Poincaré plot of normal sinus rhythm. It shows the unevenness in the distribution of points above and below the line of identity, which indicates instantaneous changes in the beat to beat heart rate. The major limitation of the existing asymmetry definition is that it considers only the instantaneous changes in the beat to beat heart rate rather than the pattern (increase/decrease). In this paper, a novel definition of asymmetry is proposed considering the geometry of a 2D Poincaré plot. Based on the proposed definition, traditional asymmetry indices--Guzik's index (GI), Porta's index (PI) and Ehlers' index (EI)--have been redefined. In order to compare the effectiveness of the new definition, all indices have been calculated for RR interval series of 54 subjects with normal sinus rhythm of 5 min and 30 min duration. The new definition resulted in a higher prevalence of normal subjects showing asymmetry in heart rate variability. PMID:19812453

Karmakar, C K; Khandoker, A H; Gubbi, J; Palaniswami, M

2009-11-01

419

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine  

Microsoft Academic Search

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim

Rosangela Poletto; Andrew M. Janczak; Ruth M. Marchant-Forde; Jeremy N. Marchant-Forde; Donald L. Matthews; Carol A. Dowell; Daniel F. Hogan; Lynetta J. Freeman; Donald C. Lay

2011-01-01

420

Applicability and efficacy of variable light in schools.  

PubMed

There is a range of reliable, empirical data on the effects of special lighting techniques on the performance of adults in the work environment in the literature. However, these studies have not adequately addressed the effects of lighting on school children in the classroom environment. In the present study, the effect of variable lighting (VL) i.e., lighting that is variable in illuminance and color temperature, was studied in the classroom using a variety of student performance and attitude measures. Two classrooms each in two separate schools were studied over a period of nine months; one class in each school served as an intervention group, and a parallel class in each school served as a control group. The effects of the individual VL programs were assessed using standardized test modules. The overall effect was measured using standardized surveys of students and teachers given at the beginning and the end of the project. The results showed that the students made fewer errors, particularly fewer errors of omission, on a standardized test of attention under the VL "Concentrate" program. Reading speed, as measured using standardized reading tests, rose significantly. Reading comprehension also improved, but this improvement was not statistically significant. In contrast, the achievement motivation of the students and the classroom atmosphere did not change over the nine-month period. Overall, the students and teachers rated VL positively and found it useful during lessons. These results are in line with previous research findings. Thus, VL represents an environmental factor that can be useful to optimize general learning conditions in schools in the future. PMID:22001491

Barkmann, Claus; Wessolowski, Nino; Schulte-Markwort, Michael

2012-02-01

421

Increase Effect of Available Transfer Capability by Dynamic Rating Application  

NASA Astrophysics Data System (ADS)

As the deregulated environment of power systems has been spread in the world, it is essential to operate power systems efficiently and economy. Under the environments, with the advance of communication technologies and sensors, the so-called dynamic rating is now to be realized. The dynamic rating is a method which determines accurate ratings by utilizing real-time information such as conductor temperatures, ambient temperatures and wind speeds. The dynamic rating is considered to increase the thermal capacities of overhead transmission lines and therefore take on importance in the deregulated electric power industry. The importance of the dynamic rating lies mainly in the area of Available Transfer Capability (ATC) improvement. In this paper, the validity of the proposed dynamic rating application is shown from the viewpoint of ATC, especially, ATC with thermal constraints. In addition, the possibilities of ATC estimations using sensitivities are verified on the purpose of reducing calculating time, considering the importance of real time simulation of ATC.

Miura, Masaki; Satoh, Takuya; Iwamoto, Shinichi; Kurihara, Ikuo

422

Microgravity alters respiratory sinus arrhythmia and short-term heart rate variability in humans  

NASA Technical Reports Server (NTRS)

We studied heart rate (HR), heart rate variability (HRV), and respiratory sinus arrhythmia (RSA) in four male subjects before, during, and after 16 days of spaceflight. The electrocardiogram and respiration were recorded during two periods of 4 min controlled breathing at 7.5 and 15 breaths/min in standing and supine postures on the ground and in microgravity. Low (LF)- and high (HF)-frequency components of the short-term HRV (< or =3 min) were computed through Fourier spectral analysis of the R-R intervals. Early in microgravity, HR was decreased compared with both standing and supine positions and had returned to the supine value by the end of the flight. In microgravity, overall variability, the LF-to-HF ratio, and RSA amplitude and phase were similar to preflight supine values. Immediately postflight, HR increased by approximately 15% and remained elevated 15 days after landing. LF/HF was increased, suggesting an increased sympathetic control of HR standing. The overall variability and RSA amplitude in supine decreased postflight, suggesting that vagal tone decreased, which coupled with the decrease in RSA phase shift suggests that this was the result of an adaptation of autonomic control of HR to microgravity. In addition, these alterations persisted for at least 15 days after return to normal gravity (1G).

Migeotte, P-F; Prisk, G. Kim; Paiva, M.; West, J. B. (Principal Investigator)

2003-01-01

423

Correlations between indices of heart rate variability in healthy children and children with congenital heart disease.  

PubMed

Heart rate variability, as determined from 24-hour Holter recordings, represents a noninvasive parameter for studying the autonomic control of the heart. It decreases with certain disease states characterized by autonomic dysfunction such as congestive heart failure. No study in healthy or cardiac children has been performed to determine the correlations between and within time and frequency domain indices of heart rate variability. We examined five time domain (SDNN, SDNNi, SDANNi, rMSSD and pNN50) and five frequency domain measures (ULF, VLF, LF, HF and balance LF/HF) in 200 healthy children and 200 children with congenital heart disease, aged 3 days to 14 years. All measures were significantly correlated with each other. However, the strength of correlation varied greatly. Our data show that variables strongly dependent on vagal tone (rMSSD, pNN50 and HF) were highly correlated (r value > 0.90), as well as SDNN and SDANNi. We conclude that certain time and frequency domain indices correlate so strongly with each other that they can act as surrogates for each other. PMID:10449882

Massin, M M; Derkenne, B; von Bernuth, G

1999-01-01

424

Pseudospark switches for high repetition rates and high current applications  

Microsoft Academic Search

The state-of-the-art of pseudospark switch (PSS) development is reported. In addition to the replacement of thyratrons for high power applications in TE-gas-discharge lasers, PSSs have been tested at high repetition rates up to 2 kHz. In order to minimize the erosion rate and to reduce total switch inductance, multichannel PSSs with various geometrical configurations have been investigated: linear, coaxial, and

K. Frank; O. Almen; P. Bickel; J. Christiansen; A. Gortler; W. Hartmann; C. Kozlik; A. Linsenmeyer; H. Loscher; F. Peter; A. Schwandner; R. Stark

1992-01-01

425

Intravenous cannulation of adolescents does not affect the modulation of autonomic tone assessed by heart rate and blood pressure variability  

Microsoft Academic Search

Invasive arterial monitoring alters autonomic tone. The effects of intravenous (IV) insertion are less clear. The author assessed the effects of IV insertion on autonomic activity in patients aged 11 to 19 years prior to head-up tilt by measuring heart rate, blood pressure, heart rate variability, blood pressure variability, and baroreceptor gain before and after IV insertion with continuous electrocardiography

Julian M. Stewart

2000-01-01

426

Abstract--Time-frequency analysis of heart rate variability (HRV) makes it easier to evaluate how the balance  

E-print Network

spectrogram. The analysis of heart rate variability (HRV) is important when studying the autonomic nervousAbstract--Time-frequency analysis of heart rate variability (HRV) makes it easier to evaluate how the balance between the sympathetic and parasympathetic influences on heart rhythm varies with time. The auto

Carvalho, João Luiz

427

Evaluation of the Effect of Heat Exposure on the Autonomic Nervous System by Heart Rate Variability and Urinary Catecholamines  

Microsoft Academic Search

Evaluation of the Effect of Heat Exposure on the Autonomic Nervous System by Heart Rate Variability and Urinary Catecholamines: Shinji YAMAMOTO, et al. Department of Hygiene, Yamaguchi University Graduate School of Medicine—The aim of this study was to investigate the usefulness of heart rate variability (HRV) and urinary catecholamines (CA) as objective indices of heat stress effect. We examined physiological

Shinji Yamamoto; Mieko Iwamoto; Masaiwa Inoue; Noriaki Harada

2007-01-01

428

Prognostic value of reduced heart rate variability after myocardial infarction: clinical evaluation of a new analysis method  

Microsoft Academic Search

The relation between heart rate variability, measured from standard 24 hour electrocardiogram recordings in patients convalescent after a myocardial infarction, and the occurrence of sudden death and spontaneous, symptomatic, sustained ventricular tachycardia were assessed in a consecutive series of 177 patients admitted with acute myocardial infarction and surviving to 7 days. In addition to the analysis of heart rate variability,

T R Cripps; M Malik; T G Farrell; A J Camm

1991-01-01

429

Comparison of the acute effects of salbutamol and terbutaline on heart rate variability in adult asthmatic patients  

Microsoft Academic Search

Comparison of the acute effects of salbutamol and terbutaline on heart rate variability in adult asthmatic patients. B. Eryonucu, K. Uzun, N.Guler, M. Bilge. #ERS Journals Ltd 2001. ABSTRACT: This study investigated the effects of b2-adrenergic agonist therapy on heart rate variability (HRV) in adult asthmatic patients by using frequency domain measures of HRV. A randomized crossover design was used.

B. Eryonucu; K. Uzun; N. Güler; M. Bilge

2001-01-01

430

Heart rate variability from short electrocardiographic recordings predicts mortality from all causes in middle-aged and elderly men  

Microsoft Academic Search

Low heart rate variability is associated with high risk of sudden death in myocardial infarction patients. This has been attributed to unfavorable autonomic cardiac control. In the present study, the predictive value of heart rate variability for sudden death, mortality from coronary heart disease, and from all causes was investigated in the general population, using brief electrocardiographic recordings. From 1960

Jacqueline M. Dekker; Evert G. Schouten; Peter Klootwijk; Jan Pool; Cees A. Swenne; Daan Kromhout

1997-01-01

431

Abstract--Cardiovascular variables such as heart rate (HR) and blood pressure (BP) are robustly regulated by an  

E-print Network

Abstract--Cardiovascular variables such as heart rate (HR) and blood pressure (BP) are robustly-5]. For instance, several authors have used the time series of heart rate (HR) and blood pressure (BP) to obtain involve many variables which are both subject to noise and interaction via feedback. The resulting

Chen, Yiling

432

Severe depression is associated with markedly reduced heart rate variability in patients with stable coronary heart disease  

Microsoft Academic Search

Objective: The purpose of this study was to investigate the relationship between depression and heart rate variability in cardiac patients. Methods: Heart rate variability was measured during 24-hour ambulatory electrocardiographic (ECG) monitoring in 40 medically stable out-patients with documented coronary heart disease meeting current diagnostic criteria for major depression, and 32 nondepressed, but otherwise comparable, patients. Patients discontinued ?-blockers and

Phyllis K Stein; Robert M Carney; Kenneth E Freedland; Judith A Skala; Allan S Jaffe; Robert E Kleiger; Jeffrey N Rottman

2000-01-01

433

Effects of controlled breathing, mental activity and mental stress with or without verbalization on heart rate variability  

Microsoft Academic Search

OBJECTIVESTo assess whether talking or reading (silently or aloud) could affect heart rate variability (HRV) and to what extent these changes require a simultaneous recording of respiratory activity to be correctly interpreted.BACKGROUNDSympathetic predominance in the power spectrum obtained from short- and long-term HRV recordings predicts a poor prognosis in a number of cardiac diseases. Heart rate variability is often recorded

Luciano Bernardi; Joanna Wdowczyk-Szulc; Cinzia Valenti; Stefano Castoldi; Claudio Passino; Giammario Spadacini; Peter Sleight

2000-01-01

434

Studying radon exhalation rates variability from phosphogypsum piles in the SW of Spain.  

PubMed

Nearly 1.0 × 10(8) tonnes of phosphogypsum were accumulated during last 50 years on a 1,200 ha disposal site near Huelva town (SW of Spain). Previous measurements of exhalation rates offered very variable values, in such a way that a worst case scenario could not be established. Here, new experimental data coupled to numerical simulations show that increasing the moisture contents or the temperature reduces the exhalation rate whilst increasing the radon potential or porosity has the contrary effect. Once the relative effects are compared, it can be drawn that the most relevant parameters controlling the exhalation rate are radon potential (product of emanation factor by (226)Ra concentration) and moisture saturation of PG. From wastes management point of view, it can be concluded that piling up the waste increasing the height instead of the surface allows the reduction of the exhalation rate. Furthermore, a proposed cover here is expected to allow exhalation rates reductions up to 95%. We established that the worst case scenario corresponds to a situation of extremely dry winter. Under these conditions, the radon exhalation rate (0.508 Bqm(-2)s(-1)) would be below though close to the upper limit established by U.S.E.P.A. for inactive phopsphogypsum piles (0.722 Bqm(-2)s(-1)). PMID:25194815

López-Coto, I; Mas, J L; Vargas, A; Bolívar, J P

2014-09-15

435

INTERANNUAL VARIABILITY OF NORTH AMERICAN MONSOON HYDROCLIMATE AND APPLICATION TO WATER MANAGEMENT IN THE  

E-print Network

i INTERANNUAL VARIABILITY OF NORTH AMERICAN MONSOON HYDROCLIMATE AND APPLICATION TO WATER of the North American Monsoon Hydroclimate and Application to Water Management in the Pecos River Basin written Variability of the North American Monsoon Hydroclimate and Application to Water Management in the Pecos River

436

The relation of aerobic fitness to cognitive control and heart rate variability: a neurovisceral integration study.  

PubMed

This aim of the present study was to investigate relationships between aerobic fitness, sympathetic and parasympathetic cardiac control using pre-ejection period (PEP) and high frequency heart rate variability (HF HRV), and performance on a task requiring variable amounts of cognitive control. Fifty-six participants completed a modified-version of the Eriksen flanker task while PEP and HF HRV were collected. A graded maximal exercise test was subsequently used to measure aerobic fitness by assessing maximal oxygen uptake. Results indicated a significant relation of fitness to reaction time performance. Although no fitness differences were observed in resting state PEP or HF HRV, higher fit adults exhibited greater task-induced parasympathetic cardiac control. However, no significant mediation was found for HF HRV on the fitness-cognitive control relationship, suggesting other mediators may be important. These findings highlight the role of aerobic fitness in enhancing integrated autonomic and neurocognitive health. PMID:24560874

Alderman, Brandon L; Olson, Ryan L

2014-05-01

437

Seismologic applications of GRACE time-variable gravity measurements  

NASA Astrophysics Data System (ADS)

The Gravity Recovery and Climate Experiment (GRACE) has been measuring temporal and spatial variations of mass redistribution within the Earth system since 2002. As large earthquakes cause significant mass changes on and under the Earth's surface, GRACE provides a new means from space to observe mass redistribution due to earthquake deformations. GRACE serves as a good complement to other earthquake measurements because of its extensive spatial coverage and being free from terrestrial restriction. During its over 10 years mission, GRACE has successfully detected seismic gravitational changes of several giant earthquakes, which include the 2004 Sumatra-Andaman earthquake, 2010 Maule (Chile) earthquake, and 2011 Tohoku-Oki (Japan) earthquake. In this review, we describe by examples how to process GRACE time-variable gravity data to retrieve seismic signals, and summarize the results of recent studies that apply GRACE observations to detect co- and post-seismic signals and constrain fault slip models and viscous lithospheric structures. We also discuss major problems and give an outlook in this field of GRACE application.

Li, Jin; Chen, Jianli; Zhang, Zizhan

2014-04-01

438

Third component in cataclysmic variables: Additional mechanism for accretion rate changes?  

NASA Astrophysics Data System (ADS)

An additional mechanism for variability of the characteristics of cataclysmic variables owed to accretion rate changes is discussed. Small variations of the distance between the components owed to the presence of a third body -- brown dwarf or a giant planet -- may cause much larger response amplified by a strong dependence of the accretion rate on the radius excess of the Roche lobe-filling secondary as well as by the irradiation. This mechanism makes accretion rate variations more complicated as compared with the models of solar-type activity of the secondary. One of the proposed candidates is EM Cyg, where a 3000-day cyclicity was found (Chinarova & Andronov 1996). A contribution of the red dwarf third body was detected in the emission from EM Cyg by North et al. (2001), but it is not clear, whether this star is physically related to the cataclysmic binary. Variations of the outburst cycle length are also seen in X Leo, AB Dra, IR Gem, AY Lyr, LL Lyr and some other stars. Another candidate is V792 Cyg, where a switch of the seasonal mean outburst cycle from 25--29d to ?39d was detected (Chinarova & Andronov 2000).

Andronov, I. L.; Chinarova, L. L.

2002-01-01

439

The Relationship between Menopausal Symptoms and Heart Rate Variability in Middle Aged Women  

PubMed Central

Background The study of the correlation of menopausal symptoms with heart rate variability (HRV) has not been adequate. The aim of this study was to investigate the relationship between postmenopausal symptoms measured by the menopause rating scale (MRS) and HRV. Methods We assessed postmenopausal symptoms (using MRS) with age, BMI, educational status, occupation, marital status, alcohol and caffeine consumption, smoking history, exercise, duration of sleep and amenorrhea, degree of anxiety and depression, menarcheal age, and heart rate variability. For evaluation of HRV, the record of electrocardiogram for 5 minutes in the resting state was divided into temporal categories and frequency categories, and analyzed. Results No significant differences in age, BMI, duration of amenorrhea, heart rate, systolic blood pressure, diastolic blood pressure, fasting blood sugar, triglyceride, and high-density lipoprotein were observed between two groups, which were divided according to menopausal symptoms. Low frequency/high frequency (LF/HF) ratio was significantly higher in symptomatic women, compared with asymptomatic women (P < 0.05). No significant differences of HRV index by the severity of postmenopausal symptoms were observed. LF/HF ratio of HRV parameters showed a significant increase in moderate or severe degree of "hot flashes" and "sleep problem" score (P < 0.05). Anxiety scale in symptomatic women was significantly higher than in asymptomatic women (P < 0.05). Conclusion The above data suggest that postmenopausal symptoms are associated with altered autonomic control of heart rate. In particular, hot flashes and sleep problems in moderate or severe degree are related to increase of sympathetic nerve activity. PMID:22745867

Lee, Jin Oh; Kang, Sung Goo; Kim, Se Hong; Park, Seo Jin

2011-01-01

440

Heart rate variability on antihypertensive drugs in black patients living in sub-Saharan Africa  

PubMed Central

Background Compared with Caucasians, African Americans have lower heart rate variability (HRV) in the high-frequency domain, but there are no studies in blacks born and living in Africa. Methods In the Newer versus Older Antihypertensive agents in African Hypertensive patients trial (NCT01030458), patients (30–69 years) with uncomplicated hypertension (140–179/90–109 mmHg) were randomized to single-pill combinations of bisoprolol/hydrochlorothiazide (R) or amlodipine/valsartan (E). 72 R and 84 E patients underwent 5-min ECG recordings at randomization and 8, 16 and 24 weeks. HRV was determined by fast Fourier transform and autoregressive modelling. Results Heart rate decreased by 9.5 beats/min in R patients with no change in E patients (? 2.2 beats/min). R patients had reduced total (? 0.13 ms²; p = 0.0038) and low-frequency power (? 3.6 nu; p = 0.057), higher high-frequency (+ 3.3 nu; p = 0.050) and a reduced low- to high-frequency ratio (? 0.08; p = 0.040). With adjustment for heart rate, these differences disappeared, except for the reduced low-frequency power in the R group (? 4.67 nu; p = 0.02). Analyses confined to 39 R and 47 E patients with HRV measurements at all visits or based on autoregressive modelling were confirmatory. Conclusion In native black African patients, antihypertensive drugs modulate HRV, an index of autonomous nervous tone. However, these effects were mediated by changes in heart rate except for low-frequency variability, which was reduced on beta blockade independent of heart rate. PMID:24066715

Osakwe, Chukwunomso E.; Jacobs, Lotte; Anisiuba, Benedict C.; Ndiaye, Mouhamado B.; Lemogoum, Daniel; Ijoma, Chinwuba K.; Kamdem, Marius M.; Thijs, Lutgarde; Boombhi, Hilaire J.; Kaptue, Joseph; Kolo, Philip M.; Mipinda, Jean B.; Odili, Augustine N.; Ezeala-Adikaibe, Birinus; Kingue, Samuel; Omotoso, Babatunde A.; Ba, Serigne A.; Ulasi, Ifeoma I.; M’buyamba-Kabangu, Jean-Rene

2014-01-01

441

Children's Sleep and Autonomic Function: Low Sleep Quality Has an Impact on Heart Rate Variability  

PubMed Central

Objectives: Short sleep duration and poor sleep quality in children have been associated with concentration, problem behavior, and emotional instability, but recently also with disrupted autonomic nervous function, which predicts cardiovascular health. Heart rate variability (HRV) was used as noninvasive indicator of autonomic function to examine the influence of sleep. Design: Cross-sectional and longitudinal observational study on the effect of sleep on HRV Participants: Belgian children (5-11 years) of the ChiBS study in 2010 (N = 334) and 2011 (N = 293). Interventions: N/A. Methods: Sleep duration was reported and in a subgroup sleep quality (efficiency, latency, awakenings) was measured with accelerometry. High-frequency (HF) power and autonomic balance (LF/HF) were calculated on supine 5-minute HRV measurements. Stress was measured by emotion and problem behavior questionnaires. Sleep duration and quality were used as HRV predictors in corrected cross-sectional and longitudinal regressions. Stress was tested as mediator (intermediate pathway) or moderator (interaction) in sleep-HRV associations. Results: In both cross-sectional and longitudinal analyses, long sleep latency could predict lower HF (parasympathetic activity), while nocturnal awakenings, sleep latency, low sleep efficiency, and low corrected sleep duration were related to higher LF/HF (sympathetic/parasympathetic balance). Parental reported sleep duration was not associated with HRV. The significances remained after correction for stress. Stress was not a mediator, but a moderator (enhancer) in the relationship between sleep quality and HRV. Conclusions: Low sleep quality but not parent-reported low sleep duration leads to an unhealthier heart rate variability pattern (sympathetic over parasympathetic dominance). This stresses the importance of good sleep quality for cardiovascular health in children. Citation: Michels N; Clays E; De Buyzere M; Vanaelst B; De Henauw S; Sioen I. Children's sleep and autonomic function: low sleep quality has an impact on heart rate variability. SLEEP 2013;36(12):1939-1946. PMID:24293769

Michels, Nathalie; Clays, Els; De Buyzere, Marc; Vanaelst, Barbara; De Henauw, Stefaan; Sioen, Isabelle

2013-01-01

442

Intelligent real-time CCD data processing system based on variable frame rate  

NASA Astrophysics Data System (ADS)

In order to meet the need of image shooting with CCD in unmanned aerial vehicles, a real-time high resolution CCD data processing system based on variable frame rate is designed. The system is consisted of three modules: CCD control module, data processing module and data display module. In the CCD control module, real-time flight parameters (e.g. flight height, velocity and longitude) should be received from GPS through UART (Universal Asynchronous Receiver Transmitter) and according to the corresponding flight parameters, the variable frame rate is calculated. Based on the calculated variable frame rate, CCD external synchronization control impulse signal is generated in the control of FPGA and then CCD data is read out. In the data processing module, data segmentation is designed to extract ROI (region of interest), whose resolution is equal to valid data resolution of HDTV standard conforming to SMPTE (1080i). On one hand, Ping-pong SRAM storage controller is designed in FPGA to real-time store ROI data. On the other hand, according to the need of intelligent observing, changeable window position is designed, and a flexible area of interest is obtained. In the real-time display module, a special video encoder is used to accomplish data format conversion. Data after storage is packeted to HDTV format by creating corresponding format information in FPGA. Through inner register configuration, high definition video analog signal is implemented. The entire system has been implemented in FPGA and validated. It has been used in various real-time CCD data processing situations.

Chen, Su-ting

2009-07-01

443

Bivalve growth rate and isotopic variability across the Barents Sea Polar Front  

NASA Astrophysics Data System (ADS)

Analysis of bivalve shell increments provides a means to reconstruct long-term patterns in growth histories and assess factors that regulate marine ecosystems, while tissue stable isotopes are indicators of food sources and trophic dynamics. We examined shell growth patterns and tissue stable isotopic composition (?13C and ?15N) of the hairy cockle (Ciliatocardium ciliatum) in the northwest Barents Sea to evaluate the influence of different water masses and the Polar Front on growth rates and food sources and to assess the influence of climatic variability on ecological processes over seasonal to decadal scales. Shell growth rates were highest in Atlantic water, intermediate in Arctic water, and lowest at the Polar Front. Temporal patterns of ontogenetically-adjusted growth (SGI) were negatively correlated with the Atlantic Multidecadal Oscillation (AMO), local precipitation and ice-free days. The highest growth occurred during colder periods with more sea ice, while lower growth was associated with warmer periods and less sea ice. Stable isotope values of lipid-extracted tissues from Atlantic water cockles were enriched in ?13C by up to 2.1‰ and ?15N by 1.5‰ compared to animals from Arctic waters. Distinct seasonal and water mass variations in stable isotopic values reflect spatial and temporal variability in food supplies to the bivalves in this region on small spatial scales. Overall, Atlantic waters supported the highest growth rates, the most complex trophic webs, and the greatest sensitivity to interannual variability in environmental conditions. Bivalves from Arctic waters were the most distinct of the three groups in their response to regional climate forcing and local environmental manifestations of those conditions. The Polar Front exhibits growth and isotopic characteristics predominantly of the Atlantic domain. These results demonstrate that integrating results of sclerochronological and stable isotopic analyses of benthic bivalves provide independent, corroborative lines of evidence and added insight into the ecological function of these systems when assessing potential effects of changes in water mass distributions in the Barents Sea.

Carroll, Michael L.; Ambrose, William G.; Locke V, William L.; Ryan, Stuart K.; Johnson, Beverly J.

2014-02-01

444

Sampling Rate of Heart Rate Variability Impacts the Ability to Detect Acidemia in Ovine Fetuses Near-Term  

PubMed Central

Background: To evaluate the impact of sampling rate on the predictive capability of continuous fetal heart rate (FHR) variability (fHRV) monitoring for detecting fetal acidemia during labor, we tested the performance of the root mean square of successive differences (RMSSD) in R–R intervals from the ECG when acquired with the sampling rate of 4?Hz currently available in FHR monitors, in comparison to the gold standard of 1000?Hz. Methods: Near-term ovine fetuses (N?=?9) were chronically prepared with precordial electrodes for recording ECG, vascular catheters for blood sampling, and an umbilical cord occluder. For 1?min every 2.5?min, animals underwent mild partial umbilical cord occlusions (UCO)?×?1?h, moderate partial UCO?×?1?h, then complete UCO?×?2?h, or until arterial pH reached <7.00. Arterial blood samples were drawn at baseline and every 20?min during the UCO series. RMSSD was calculated continuously in 5?min windows using an automated, standardized system (CIMVA.com). Results are presented as mean?±?SEM with significance assumed for p?rate of 4?Hz used clinically, RMSSD remained unchanged until terminally when the nadir pH was reached. For early detection of fetal acidemia during labor, more sensitive means of acquiring FHR are therefore recommended than currently deployed, e.g., trans-abdominal fetal ECG. PMID:24829897

Durosier, L. Daniel; Green, Geoffrey; Batkin, Izmail; Seely, Andrew J.; Ross, Michael G.; Richardson, Bryan S.; Frasch, Martin G.

2014-01-01

445

Sympathetic nervous system representation in time and frequency domain indices of heart rate variability  

Microsoft Academic Search

This study evaluated the contributions of sympathetic and parasympathetic modulation to heart rate variability during situations\\u000a in which vagal and sympathetic tone predominated. In a placebo-controlled, randomized, double blind blockade study, six young\\u000a healthy male individuals received propranolol (0.2?mg?·?kg?1), atropine (0.04?mg?·?kg?1), propranolol plus atropine, or placebo infusions over 4 days. Time-domain indices were calculated during 40?min of rest\\u000a and 20?min

Carisi A. Polanczyk; Luis E. P. Rohde; Ruy S. Moraes; Elton L. Ferlin; Cristina Leite; Jorge P. Ribeiro

1998-01-01

446

Acute effects on heart rate variability when exposed to hand transmitted vibration and noise  

Microsoft Academic Search

Objectives  This study investigates possible acute effects on heart rate variability (HRV) when people are exposed to hand transmitted\\u000a vibration and noise individually and simultaneously.\\u000a \\u000a \\u000a \\u000a Methods  Ten male and 10 female subjects were recruited by advertisement. Subjects completed a questionnaire concerning their work\\u000a environment, general health, medication, hearing, and physical activity level. The test started with the subject resting for\\u000a 15 min while

Bodil Björ; Lage Burström; Marcus Karlsson; Tohr Nilsson; Ulf Näslund; Urban Wiklund

2007-01-01

447

Interval training in elderly men increases both heart rate variability and baroreflex activity  

Microsoft Academic Search

\\u000a Abstract\\u000a \\u000a Aims\\u000a   Autonomic nervous system activity decreases continuously with age and appears to be a powerful predictor of disease and death. Attempts are thus made to reactivate autonomic drive with the intent of improving health.\\u000a Methods\\u000a   We assessed maximal oxygen consumption (VO2max), auto- nomic nervous system activity by heart rate variability (HRV) analysis and spontaneous cardiac baroreflex activity (SBR) in

Vincent Pichot; Frédéric Roche; Christian Denis; Martin Garet; David Duverney; Frédéric Costes; Jean-Claude Barthélémy

2005-01-01

448

Marital Status and Heart Rate Variability in Patients with Suspected Coronary Artery Disease  

Microsoft Academic Search

Background  Married individuals are at reduced risk of cardiovascular disease morbidity and mortality. Recent research indicates that\\u000a impaired heart rate variability (HRV) may contribute to cardiovascular disease morbidity and mortality and has also been associated\\u000a with social isolation.\\u000a \\u000a \\u000a \\u000a Purpose  We investigated associations between HRV and marital status in patients with suspected coronary artery disease (CAD).\\u000a \\u000a \\u000a \\u000a Methods  Eighty-eight patients who were being investigated for

Gemma Randall; Mimi R. Bhattacharyya; Andrew Steptoe

2009-01-01

449

Association between Frequency Domain Heart Rate Variability and Unplanned Readmission to Hospital in Geriatric Patients  

Microsoft Academic Search

Background  An accurate prediction of unplanned readmission (UR) after discharge from hospital can facilitate physician's decision making\\u000a processes for providing better quality of care in geriatric patients. The objective of this study was to explore the association\\u000a of cardiac autonomic functions as measured by frequency domain heart rate variability (HRV) and 14-day UR in geriatric patients.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Patients admitted to the geriatric

Jui-Kun Chiang; Chin-Hua Fu; Terry BJ Kuo; Malcolm Koo

2011-01-01

450

Association between heart rate variability and training response in sedentary middle-aged men  

Microsoft Academic Search

The effect of exercise training on heart rate variability (HRV) and improvements in peak oxygen consumption (\\u000a$$\\\\dot V{\\\\text{O}}_{\\\\text{2}} $$\\u000a\\u000apeak) was examined in sedentary middle-aged men. The HRV and absolute and relative\\u000a$$\\\\dot V{\\\\text{O}}_{\\\\text{2}} $$\\u000a\\u000apeak of training (n = 19) and control (n = 15) subjects were assessed before and after a 24-session moderate intensity exercise training programme.

Stephen H. Boutcher; Phyllis Stein

1995-01-01

451

Calculation of vaporization rates assuming various rate determining steps: Application to the resistojet  

NASA Technical Reports Server (NTRS)

The various steps that could control the vaporization rate of a material are discussed. These steps include the actual vaporization, flow rate of matrix gas, chemical reaction, gas diffusion, and solid state diffusion. The applicable equations have been collected from diverse appropriate sources, and their use is explained. Rate equations are derived for conditions where more than one step is rate controlling. Calculations are made for two model materials: rhenium which vaporizes congruently, and tantalum carbide which vaporizes incongruently. The case of vaporization under thermal gradient conditions is also treated. The existence of a thermal gradient in the resistojet means that the vaporization rate of a material may be only one thousandth of that predicted under isothermal conditions. Calculations show that rhenium might have a 100,000 hr lifetime at temperature in a 2500 C resistojet. Tantalum carbide would have a life of only 660 sec under similar conditions.

May, C. E.

1984-01-01

452

Atypical pupillary light reflex and heart rate variability in children with autism spectrum disorder.  

PubMed

We investigated pupillary light reflex (PLR) in 152 children with ASD, 116 typically developing (TD) children, and 36 children with non-ASD neurodevelopmental disorders (NDDs). Heart rate variability (HRV) was measured simultaneously to study potential impairments in the autonomic nervous system (ANS) associated with ASD. The results showed that the ASD group had significantly longer PLR latency, reduced relative constriction amplitude, and shorter constriction/redilation time than those of the TD group. Similar atypical PLR parameters were observed in the NDD group. A significant age effect on PLR latency was observed in children younger than 9 years in the TD group, but not in the ASD and NDD groups. Atypical HRV parameters were observed in the ASD and NDD groups. A significant negative correlation existed between the PLR constriction amplitude and average heart rate in children with an ASD, but not in children with typical development. PMID:23248075

Daluwatte, Chathuri; Miles, Judith H; Christ, Shawn E; Beversdorf, David Q; Takahashi, T Nicole; Yao, Gang

2013-08-01

453

Biomedical Teleacupuncture between China and Austria Using Heart Rate Variability-Part 2: Patients with Depression.  

PubMed

It has been shown in previous studies that the autonomic nervous system can be affected by acupuncture. Within this study, teleacupuncture between China and Austria is used for quantifying the effects of heart rate (HR) and heart rate variability (HRV) in 33 Chinese patients (27 females, 6 males; mean age ± SD 49.5 ± 13.1 years; range 22-72 years) suffering from depression. Electrocardiographic signals before, during, and after acupuncture at the acupoint Baihui (GV20) were recorded in Harbin and analyzed in Graz using teleacupuncture. HRV data were analyzed in the time and frequency domain. Mean HR decreased significantly (P < 0.05) during and after acupuncture, whereas total HRV increased significantly after the third acupuncture stimulation period (P < 0.05) and also 5-10 minutes after (P < 0.05) acupuncture. The study shows that HRV could be a useful parameter for quantifying clinical effects of acupuncture on the autonomic nervous system. PMID:22570670

Litscher, Gerhard; Cheng, Guangyu; Wang, Lu; Cheng, Weiping; Su, Hang; Niu, Qianqian; Zou, Tianyu; Wang, Yongyue; Feng, Xiao; Gaischek, Ingrid; Sheng, Zemin; Kuang, Haixue

2012-01-01

454

Biomedical Teleacupuncture between China and Austria Using Heart Rate Variability--Part 2: Patients with Depression  

PubMed Central

It has been shown in previous studies that the autonomic nervous system can be affected by acupuncture. Within this study, teleacupuncture between China and Austria is used for quantifying the effects of heart rate (HR) and heart rate variability (HRV) in 33 Chinese patients (27 females, 6 males; mean age ± SD 49.5 ± 13.1 years; range 22–72 years) suffering from depression. Electrocardiographic signals before, during, and after acupuncture at the acupoint Baihui (GV20) were recorded in Harbin and analyzed in Graz using teleacupuncture. HRV data were analyzed in the time and frequency domain. Mean HR decreased significantly (P < 0.05) during and after acupuncture, whereas total HRV increased significantly after the third acupuncture stimulation period (P < 0.05) and also 5–10 minutes after (P < 0.05) acupuncture. The study shows that HRV could be a useful parameter for quantifying clinical effects of acupuncture on the autonomic nervous system. PMID:22570670

Litscher, Gerhard; Cheng, Guangyu; Wang, Lu; Cheng, Weiping; Su, Hang; Niu, Qianqian; Zou, Tianyu; Wang, Yongyue; Feng, Xiao; Gaischek, Ingrid; Sheng, Zemin; Kuang, Haixue

2012-01-01