Sample records for variable rate applications

  1. Verification of a variable rate sprayer for nursery liner applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An experimental variable-rate sprayer designed for liner applications was tested by comparing its spray deposit and coverage, and droplet density inside canopies of six nursery liner varieties with constant-rate applications. Spray samplers, including water sensitive papers (WSP) and nylon screens, ...

  2. Development of variable-rate sprayer for nursery liner applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sensor-guided application technologies are needed to achieve constant spray deposition for the rapid growth of nursery liner trees during a growing season. An experimental real-time variable-rate sprayer that implemented 20 Hz ultrasonic sensors and pulse width modulation (PWM) solenoid valve-contro...

  3. Evaluation of Application Accuracy and Performance of a Hydraulically Operated Variable-Rate Aerial Application System

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An aerial variable-rate application system consisting of a DGPS-based guidance system, automatic flow controller, and hydraulically controlled pump/valve was evaluated for response time to rapidly changing flow requirements and accuracy of application. Spray deposition position error was evaluated ...

  4. Mathematic models of water application for a variable rate irrigating hill-seeder

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variable rate irrigating hill-seeder can adjust water application automatically according to the difference in soil moisture content in the field to alleviate drought and save water. Two key problems to realize variable rate water application are how to determine the right amount of water for the ...

  5. [Analysis of heart rate variability. Mathematical description and practical application].

    PubMed

    Sammito, S; Böckelmann, I

    2015-03-01

    The analysis of heart rate variability (HRV) has recently become established as a non-invasive measurement for estimation of demands on the cardiovascular system. The HRV reflects the interaction of the sympathetic and parasympathetic nervous systems and allows the influence of the autonomic nervous system on the regulation of the cardiovascular system to be mathematically described. This review explicates the analysis method of HRV for time, frequency and non-linear methods as well as the range of parameters and the demand on acquisition time. The necessity and possibilities of artefact correction and advice for the selection of a reasonable acquisition period are discussed and standard values for selected HRV parameters are presented. PMID:25298003

  6. Partial budget analysis of variable-rate nitrogen application on dryland spring wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural producers can use variable-rate application technology to vary nitrogen (N) fertilizer within fields. This study was conducted to estimate changes in net returns from implementation of variable-rate N management (VNM) on hard red spring wheat (Triticum aestivum L.). Net return from un...

  7. Runoff Water Quality Impact of Variable Rate Sidedress Nitrogen Application

    Microsoft Academic Search

    R. D. Harmel; A. L. Kenimer; S. W. Searcy; H. A. Torbert

    2004-01-01

    In recent years, precision agriculture has received attention from producers, agribusiness, and governmental agencies in an effort to increase profitability and protect the environment. Many aspects of precision agriculture, such as soil fertility, application technology, and economic factors, have received substantial research attention; however, other aspects of precision agriculture have not been well documented. One important issue that warrants increased

  8. A Ferrofluidic Magnetic Micropump for Variable-Flow-Rate Applications

    NASA Astrophysics Data System (ADS)

    Lee, Chia-Yen; Leong, Jik-Chang; Wang, Yao-Nan; Fu, Lung-Ming; Chen, Sih-Jia

    2012-04-01

    A novel micropump is proposed comprising two ferrofluidic plugs contained within a circular poly(methyl methacrylate) (PMMA) microchannel and a permanent magnet positioned beneath one of the plugs and driven by a rotating stepping motor. The ferrofluidic plugs are immiscible with the sample fluid. Thus, as the stepping motor rotates, the sample trapped between the two plugs is driven through the circular microchannel and exits the pump via the outlet diffuser. Meanwhile, more sample fluid is drawn into the microchannel on the inlet side. As a result, a continuous pumping effect is achieved. It is shown that the flow rate in the proposed device can be easily controlled by adjusting the rotational velocity of the stepping motor. In addition, for a constant motor velocity, the flow rate can be improved by increasing the circular channel width. The experimental results show that a maximum flow rate of 93 µl/min is obtained given a channel width of 1000 µm and a rotational velocity of 8 rpm. In addition, it is shown that the pump is capable of developing a maximum pressure head of 75 mm water (0.66 kPa) with channel width of 500 µm.

  9. A variable rate speech compressor for mobile applications

    NASA Technical Reports Server (NTRS)

    Yeldener, S.; Kondoz, A. M.; Evans, B. G.

    1990-01-01

    One of the most promising speech coder at the bit rate of 9.6 to 4.8 kbits/s is CELP. Code Excited Linear Prediction (CELP) has been dominating 9.6 to 4.8 kbits/s region during the past 3 to 4 years. Its set back however, is its expensive implementation. As an alternative to CELP, the Base-Band CELP (CELP-BB) was developed which produced good quality speech comparable to CELP and a single chip implementable complexity as reported previously. Its robustness was also improved to tolerate errors up to 1.0 pct. and maintain intelligibility up to 5.0 pct. and more. Although, CELP-BB produces good quality speech at around 4.8 kbits/s, it has a fundamental problem when updating the pitch filter memory. A sub-optimal solution is proposed for this problem. Below 4.8 kbits/s, however, CELP-BB suffers from noticeable quantization noise as a result of the large vector dimensions used. Efficient representation of speech below 4.8 kbits/s is reported by introducing Sinusoidal Transform Coding (STC) to represent the LPC excitation which is called Sine Wave Excited LPC (SWELP). In this case, natural sounding good quality synthetic speech is obtained at around 2.4 kbits/s.

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

    Microsoft Academic Search

    Khalid Ali Al-Gaadi

    1998-01-01

    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

  11. Variable-rate nitrogen application algorithm based on canopy reflected spectrum and its influence on wheat

    NASA Astrophysics Data System (ADS)

    Liang, Hongxia; Zhao, Chunjiang; Huang, Wenjiang; Liu, Liangyun; Wang, Jihua; Ma, Youhua

    2005-01-01

    This study was to develop the time-specific and time-critical method to overcome the limitations of traditional field sampling methods for variable rate fertilization. Farmers, agricultural managers and grain processing enterprises are interested in measuring and assessing soil and crop status in order to apply adequate fertilizer quantities to crop growth. This paper focused on studying the relationship between vegetation index (OSAVI) and nitrogen content to determine the amount of nitrogen fertilizer recommended for variable rate management in precision agriculture. The traditional even rate fertilizer management was chosen as the CK. The grain yield, ear numbers, 1000-grain weight and grain protein content were measured among the CK, uniform treatments and variable rate fertilizer treatments. It indicated that variable rate fertilization reduced the variability of wheat yield, ear numbers and dry biomass, but it didn't increased crop yield and grain protein content significantly and did not decrease the variety of 1000-grain weight, compared to traditional rate application. The nitrogen fertilizer use efficiency was improved, for this purpose, the variable rate technology based on vegetation index could be used to prevent under ground water pollution and environmental deterioration.

  12. Integrating Spray Plane-Based Remote Sensing and Rapid Image Processing with Variable-Rate Aerial Application

    Microsoft Academic Search

    Steven J. Thomson; Randy R. Price; Lowrey A. Smith

    A remote sensing and variable rate application system was configured for agricultural aircraft. This combination system has the potential of providing a completely integrated solution for all aspects of aerial site-specific application and includes remote sensing, image processing and georegistration, prescription generation, and variable-rate application. A missing link has been the ability to rapidly process and georeference images obtained during

  13. Possible forms of heart-rate variability and their application: use of heart-rate variability in assessment of surgical patients

    Microsoft Academic Search

    T.-Y. Slonim; M. Slonim; G. Daychman; L. Roytblat; I. Ovsyshcher

    1997-01-01

    A new approach has been proposed for the estimation of variables based on Heart Rate Variability during a surgical operation. The following variables, Heart Rate Variability Index, Normalized Inert Rate Variability Index and Integral Estimation have been introduced and used for the analysis and estimation of surgical procedures in 7 patients. All variables have a clear physical meaning; they are

  14. Zone mapping application for precision-farming: a decision support tool for variable rate application

    Microsoft Academic Search

    Xiaodong Zhang; Lijian Shi; Xinhua Jia; George Seielstad; Craig Helgason

    2010-01-01

    A web-based decision support tool, zone mapping application for precision farming (ZoneMAP, http:\\/\\/zonemap.umac.org), has been developed to automatically determine the optimal number of management zones and delineate them using satellite\\u000a imagery and field data provided by users. Application rates, such as of fertilizer, can be prescribed for each zone and downloaded\\u000a in a variety of formats to ensure compatibility with

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

    E-print Network

    Beck, Andy Dwayne

    2001-01-01

    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...

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

    E-print Network

    Beck, Andy Dwayne

    2001-01-01

    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...

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

    PubMed Central

    Flatt, Andrew A.; Esco, Michael R.

    2013-01-01

    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

  18. Change Rates and Prevalence of a Dichotomous Variable: Simulations and Applications

    PubMed Central

    Brinks, Ralph; Landwehr, Sandra

    2015-01-01

    A common modelling approach in public health and epidemiology divides the population under study into compartments containing persons that share the same status. Here we consider a three-state model with the compartments: A, B and Dead. States A and B may be the states of any dichotomous variable, for example, Healthy and Ill, respectively. The transitions between the states are described by change rates, which depend on calendar time and on age. So far, a rigorous mathematical calculation of the prevalence of property B has been difficult, which has limited the use of the model in epidemiology and public health. We develop a partial differential equation (PDE) that simplifies the use of the three-state model. To demonstrate the validity of the PDE, it is applied to two simulation studies, one about a hypothetical chronic disease and one about dementia in Germany. In two further applications, the PDE may provide insights into smoking behaviour of males in Germany and the knowledge about the ovulatory cycle in Egyptian women. PMID:25749133

  19. Autonomic dysfunction in patients with fibromyalgia: Application of power spectral analysis of heart rate variability

    Microsoft Academic Search

    Hagit Cohen; Lily Neumann; Margarita Shore; Marianne Amir; Yair Cassuto; Dan Buskila

    2000-01-01

    Objectives:To assess the interaction between the sympathetic and parasympatheticsystems in patients with fibromyalgia syndrome (FM), using power spectrum analysis (PSA) of heart rate variability (HRV). In addition, we explored the association between HRV, measures of tenderness, FM symptoms, physical function, psychological well being and quality of life.

  20. DYNAMIC TESTING OF GPS RECEIVERS ON AGRICULTURAL AIRCRAFT FOR REMOTE SENSING AND VARIABLE-RATE AERIAL APPLICATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global Positioning System (GPS) receivers and GPS-based swath guidance systems are used on agricultural aircraft for remote sensing, airplane guidance, and to support variable-rate aerial application of crop inputs such as insecticides, cotton growth regulators, and defoliants. Agricultural aircraf...

  1. Compensating inherent linear move water application errors using a variable rate irrigation system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous move irrigation systems such as linear move and center pivot irrigate unevenly when applying conventional uniform water rates due to the towers/motors stop/advance pattern. The effect of the cart movement pattern on linear move water application is larger on the first two spans which intr...

  2. Progress and Field Evaluation of Aerial Variable-Rate Systems for Liquid Application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flow control systems for aerial spraying have been evaluated at the USDA, ARS, CPSRU over the past 12 years. Early experiments were designed to evaluate the ability of flow controllers to provide a desired application rate regardless of changes in ground speed. More recent testing has focused on var...

  3. Determinants of heart rate variability

    Microsoft Academic Search

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

    1996-01-01

    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

  4. Dynamic Testing of GPS Receivers on Agricultural Aircraft for Remote Sensing and Variable-Rate Aerial Application

    Microsoft Academic Search

    Steven J. Thomson; Lowrey A. Smith

    2006-01-01

    Global Positioning System (GPS) receivers and GPS-based swath guidance systems are used on agricultural aircraft for remote sensing, airplane guidance, and to support variable-rate aerial application of crop inputs such as insecticides, cotton growth regulators, and defoliants. Agricultural aircraft travel at much greater speeds than ground equipment (65 m\\/s, typically), so longitudinal (along-track) error in GPS-derived position is likely to

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

    E-print Network

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

    2002-05-21

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  7. FIELD TESTING OF A VARIABLE RATE SPRINKLER AND CONTROL SYSTEM FOR SITE-SPECIFIC WATER AND NUTRIENT APPLICATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development and implementation of site-specific sprinkler irrigation management has been limited due to the lack of variable rate sprinklers. Thirty-two prototype variable rate sprinklers were constructed and field tested on a three-span linear-move irrigation system. An algorithm was developed for...

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

    E-print Network

    Blasingame, Thomas Alwin

    1986-01-01

    for Constant Rate Post ? Transient Flaw Dresden, Vertically Fractured Reservoirs Canventianal Analysis for Constant Wellhcue Pressure post-Transient Flow Drawdown, Homogeneous ~airs 155 158 List of Figures (Continued) SS Conventiona1 Analysis...

  9. Crop Sensors to Control Variable-Rate N Applications: Five Years of On-Farm Demonstrations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimal N fertilizer rate often varies widely from year to year, field to field, and place to place within a field. Site-specific N management is needed to meet crop needs without over-fertilizing. Crop sensors are an option for site-specific N management that potentially can account for year-specif...

  10. Analysis of Heart Rate Variability

    Microsoft Academic Search

    B. Mc A. SAYKRS

    1973-01-01

    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

  11. Heart rate variability: a review

    Microsoft Academic Search

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

    2006-01-01

    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

  12. Active crop canopy sensor optimal spatial scale for in-season variable-rate nitrogen application in corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Active crop canopy reflectance sensors have shown to be an efficient method for assessing spatially-variable crop nitrogen (N) need and controlling remedial in-season N applications in wheat. Recently, these sensors have been studied for N application in corn. This study will be conducted during the...

  13. Economics of Variable Rate Lime in Indiana

    Microsoft Academic Search

    R. Bongiovanni; J. Lowenberg-Deboer

    2000-01-01

    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

  14. Crop growth and soil water spatial variability under a variable rate center pivot

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision agriculture has mostly emphasized variable-rate nutrients, seeding, and pesticide applications. More recently, variable-rate irrigation equipment has been developed to explore the potential for managing irrigation spatially. Managing irrigation spatially can enhance water conservation and ...

  15. Heart rate variability in weightlifters

    Microsoft Academic Search

    E. V. Oreshnikov; V. F. Tihonov; T. V. Agafonkina

    2009-01-01

    On the basis of the literature and original data, heart rate variability (HRV) in weightlifters has been studied. The results\\u000a showed that the distribution mode (a parameter of mathematical analysis that is equal to the most frequent length of RR intervals)\\u000a indicates the intensity of physical exercise. Specific changes in the autonomic balance in athletes as dependent on their\\u000a degree

  16. PERFORMANCE OF AN AERIAL VARIABLE-RATE APPLICATION SYSTEM WITH A HYDRAULICALLY POWERED CHEMICAL PUMP AND SPRAY VALVE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The performance was evaluated for a variable-rate system that consisted of a SATLOC M3 with AirTrac software with WAAS corrected DGPS (5 Hz position update) and an AutoCal II automatic flow controller. This system was installed on an Air Tractor 402B equipped with an auxiliary hydraulic package tha...

  17. An Analysis of Heart Rate Variability

    Microsoft Academic Search

    H. LUCZAK; W. LAURIG

    1973-01-01

    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

  18. [The efficiency of Lyapko applicators usage in the treatment of patients with comorbidity of hypertension and chronic pancreatitis based on the heart rate variability].

    PubMed

    Medvid', I I; Babinets', L S; Herasymets', I I

    2014-11-01

    Efficiency of the acupressure methodics of Lyapko applicators including in the treatment of patients with comorbidity of hypertension and chronic pancreatitis is estimated based on the study of the dynamics of the clinic and the state of autonomic nervous system using heart rate variability. The significant autonomic disorders were found in the studied group. More pronounced effect of this method of acupuncture was confirmed for the treatment of comorbidity of the studied pathologies, especially with regard to autonomic disorders. PMID:25528844

  19. Heart Rate Variability Biofeedback for Major Depression

    Microsoft Academic Search

    Maria Karavidas

    Heart rate variability for the treatment of major depression is a novel, alternative approach that can offer symptom reduction with minimal-to-no noxious side effects. The following material will illustrate some of the work being conducted at our laboratory to demonstrate the efficacy of heart rate variability. Namely, results will be presented regarding our published work on an initial open-label study

  20. Variable-rate variable-power MQAM for fading channels

    Microsoft Academic Search

    Andrea J. Goldsmith; Soon-Ghee Chua

    1997-01-01

    We propose a variable-rate and variable-power MQAM modulation scheme for high-speed data transmission over fading channels. We first review results for the Shannon capacity of fading channels with channel side information, where capacity is achieved using adaptive transmission techniques. We then derive the spectral efficiency of our proposed modulation. We show that there is a constant power gap between the

  1. [Heart rate: clinical variable and risk marker].

    PubMed

    Custodis, F; Reil, J-C; Schirmer, S H; Adam, O; Möhlenkamp, S; Laufs, U; Böhm, M

    2014-08-01

    Heart rate is an easily accessible clinical variable with wide-ranging prognostic impact. Elevated resting heart rate predicts an elevated cardiovascular risk. Epidemiological studies demonstrate a relevant association between heart rate and survival in individuals without diagnosed cardiovascular disease and with cardiovascular disease like hypertension, coronary artery disease (CAD) and heart failure. Whereas a goal directed pharmacological heart rate reduction is not supported by clinical evidence for primary prevention it plays a prognostic role for patients with CAD? and chronic heart failure. Moreover heart rate can be characterized as an independent risk factor for patients with heart failure and potentially for those with CAD. As a result the common guidelines recommend heart rate reduction as a target of therapy. PMID:25093954

  2. Multiagent Learning Using a Variable Learning Rate

    E-print Network

    Bowling, Michael

    Multiagent Learning Using a Variable Learning Rate Michael Bowling, Manuela Veloso Computer Science require determining a course of action for each agent just as in single-agent domains. Machine learning of specifying appropriate behaviors for an agent. In particular, through learning an agent can discover

  3. Rater Variables Associated with ITER Ratings

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  4. Breathing frequency bias in fractal analysis of heart rate variability

    Microsoft Academic Search

    Pandelis Perakakis; Michael Taylor; Eduardo Martinez-Nieto; Ioanna Revithi; Jaime Vila

    2009-01-01

    Detrended Fluctuation Analysis (DFA) is an algorithm widely used to determine fractal long-range correlations in physiological signals. Its application to heart rate variability (HRV) has proven useful in distinguishing healthy subjects from patients with cardiovascular disease. In this study we examined the effect of respiratory sinus arrhythmia (RSA) on the performance of DFA applied to HRV. Predictions based on a

  5. Evaluation of a center pivot variable rate irrigation system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Uniformity of water distribution of a variable rate center pivot irrigation system was evaluated. This 4-span center-pivot system was configured with 10 water application zones along its 766 ft-long lateral. Two experiments were conducted for the uniformity tests. In one test, a constant water appli...

  6. Modeling and Analysis of a Variable Bit Rate Video Multiplexer

    Microsoft Academic Search

    Gopalakrishnan Ramamurthy; Bhaskar Sengupta

    1992-01-01

    The authors develop a new analytic model for a variable bit rate video source, which can model a variety of video applications by a suitable choice of model parameters. Using the model they studied the performance of a video multiplexer that multiplexes several full motion video sources. The video sources were assumed to use a layered coding technique. A service

  7. Heart rate variability and intima media thickness

    Microsoft Academic Search

    Nanna Hurwitz Eller; Birgitta Malmberg; Peter Bruhn

    2006-01-01

    Increased activity in the sympathetic nervous system is part of the physiological stress response and is expressed in the\\u000a heart rate variability (HRV). The objective of this study was to examine associations of HRV and intima media thickness (IMT).\\u000a In 2002, satisfactory measurements of HRV of 78 voluntary participants were made, both during a stress test and during sleep.\\u000a IMT

  8. Multiscale power analysis for heart rate variability

    NASA Astrophysics Data System (ADS)

    Zeng, Peng; Liu, Hongxing; Ni, Huangjing; Zhou, Jing; Xia, Lan; Ning, Xinbao

    2015-06-01

    We first introduce multiscale power (MSP) method to assess the power distribution of physiological signals on multiple time scales. Simulation on synthetic data and experiments on heart rate variability (HRV) are tested to support the approach. Results show that both physical and psychological changes influence power distribution significantly. A quantitative parameter, termed power difference (PD), is introduced to evaluate the degree of power distribution alteration. We find that dynamical correlation of HRV will be destroyed completely when PD>0.7.

  9. Variability of Recombination Rates in Higher Plants

    Microsoft Academic Search

    Elisabeth Esch; Renate Horn

    \\u000a Recombination and chiasma frequency, like other features of meiosis, are subject to various genetic control mechanisms. Here,\\u000a we give an overview of the genetic and environmental factors as well as the genomic structures that play a role for the variability\\u000a of recombination rates in plant genomes. Suppressed or greatly reduced recombination is observed in chromosomal regions that\\u000a contain repetitive sequences

  10. Quantitative analysis of heart rate variability

    Microsoft Academic Search

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

    1995-01-01

    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

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

    Microsoft Academic Search

    Hye-Sue Song; Paul M. Lehrer

    2003-01-01

    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

  12. Heart Rate Variability – A Historical Perspective

    PubMed Central

    Billman, George E.

    2011-01-01

    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

  13. Variable Effects of Physical Training of Heart Rate Variability, Heart Rate Recovery, and Heart Rate Turbulence in Chronic Heart Failure

    Microsoft Academic Search

    EWA PIOTROWICZ; RAFA? BARANOWSKI; MA?GORZATA PIOTROWSKA; TOMASZ ZIELI?SKI; RYSZARD PIOTROWICZ

    2009-01-01

    Background: Heart rate variability (HRV), heart rate turbulence (HRT), and heart rate recovery (HRR), indices that reflect autonomic nervous system (ANS) activity, are outcome predictors in patients with chronic heart failure (CHF). It is not clear, however, whether they reflect the same components of ANS activity. No study has examined the effects of physical training (PT) training on HRV, HRT,

  14. 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

  15. 7 CFR 1735.33 - Variable interest rate loans.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 2011-01-01 false Variable interest rate loans. 1735.33 ...PROGRAM Types of Loans § 1735.33 Variable interest rate loans. After June...to November 1, 1993, RUS made certain variable rate loans at interest rates less...

  16. 7 CFR 1735.33 - Variable interest rate loans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 2010-01-01 false Variable interest rate loans. 1735.33 ...PROGRAM Types of Loans § 1735.33 Variable interest rate loans. After June...to November 1, 1993, RUS made certain variable rate loans at interest rates less...

  17. Heart rate and heart rate variability in subjectively reported insomnia.

    PubMed

    Spiegelhalder, Kai; Fuchs, Lena; Ladwig, Johannes; Kyle, Simon D; Nissen, Christoph; Voderholzer, Ulrich; Feige, Bernd; Riemann, Dieter

    2011-03-01

    According to epidemiological studies, insomnia is associated with cardiovascular mortality. However, it is yet to be determined whether this link is mediated by known cardiovascular risk factors. The current study aimed at investigating the association between primary insomnia, defined as subjectively reported sleep disturbance in the absence of any other pathology or substance intake, and alterations in polysomnographically determined nocturnal heart rate (HR) and heart rate variability (HRV). A total of 4,581 nocturnal short-term electrocardiographic recordings (5 min each) from 104 participants (58 with primary insomnia, 46 healthy controls) were evaluated for HR as well as for time and frequency domain measures of HRV. In the primary insomnia group, we found a lower wake-to-sleep HR reduction and a lower standard deviation of RR intervals (SDNN) compared to healthy controls. However, between-group differences in resting HR were not found, and previous results of an increase in sympathovagal balance and a decrease in parasympathetic nocturnal activity in objectively determined insomnia could not be confirmed in our sample of self-report insomnia patients. When restricting our analyses to insomnia patients with objectively determined short sleep duration, we found reduced parasympathetic activity as indicated by decreased high frequency power of HRV, as well as decreased root mean square of successive RRI differences (RMSSD) and percentage of successive RRIs that differ by more than 50 ms (pNN50) values. A lower wake-to-sleep HR reduction and alterations in HRV variables might, at least partially, mediate the increased rates of cardiovascular morbidity and mortality observed in insomnia patients. PMID:20626615

  18. Variability of Evolutionary Rates of DNA

    PubMed Central

    Gillespie, John H.

    1986-01-01

    A statistical analysis of DNA sequences from four nuclear loci and five mitochondrial loci from different orders of mammals is described. A major aim of the study is to describe the variation in the rate of molecular evolution of proteins and DNA. A measure of rate variability is the statistic R, the ratio of the variance in the number of substitutions to the mean number. For proteins, R is found to be in the range 0.16 < R < 35.55, thus extending in both directions the values seen in previous studies. An analysis of codons shows that there is a highly significant excess of double substitutions in the first and second positions, but not in the second and third or first and third positions. The analysis of the dynamics of nucleotide evolution showed that the ergodic Markov chain models that are the basis of most published formulas for correcting for multiple substitutions are incompatible with the data. A bootstrap procedure was used to show that the evolution of the individual nucleotides, even the third positions, show the same variation in rates as seen in the proteins. It is argued that protein and silent DNA evolution are uncoupled, with the evolution at both levels showing patterns that are better explained by the action of natural selection than by neutrality. This conclusion is based primarily on a comparison of the nuclear and mitochondrial results. PMID:3744027

  19. Acupuncture regulates the heart rate variability.

    PubMed

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

    2015-04-01

    Acupuncture is widely used in clinical practice. According to traditional acupuncture theory, the Neiguan acupoint (PC6) is one of the most commonly used acupoints and is indicated for treating cardiovascular-related disorders. We present the case of a 27-year-old female who had been diagnosed with ventricular septal defect and had undergone surgery to repair the defect at the age of 11 years. The patient had no obvious symptoms, such as palpitations and difficulty breathing. However, while performing electrocardiography (ECG), we found that she suffered from arrhythmia, and therefore, we treated her by acupuncture at the left PC6. An ECG monitor was used to record data during the entire acupuncture procedure, which was divided into the following three segments: prior to, during, and after acupuncture. Various indices of heart rate variability (HRV) were then determined and analyzed. The results indicate that acupuncture can regulate the HRV effectively; however, more studies are needed to confirm this finding. PMID:25952126

  20. 12 CFR 560.210 - Disclosures for variable rate transactions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 false Disclosures for variable rate transactions. 560.210 Section...Transactions § 560.210 Disclosures for variable rate transactions. A savings association...described at 12 CFR 226.20(c) for variable rate transactions, as described...

  1. 12 CFR 560.210 - Disclosures for variable rate transactions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 false Disclosures for variable rate transactions. 560.210 Section...Transactions § 560.210 Disclosures for variable rate transactions. A savings association...described at 12 CFR 226.20(c) for variable rate transactions, as described...

  2. Soil variability in engineering applications

    NASA Astrophysics Data System (ADS)

    Vessia, Giovanna

    2014-05-01

    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

  3. gHRV: Heart rate variability analysis made easy.

    PubMed

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

    2014-08-01

    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

  4. Heart rate variability in smokers, sedentary and aerobically fit individuals

    Microsoft Academic Search

    Dympna Gallagher; Thomas Terenzi; Ronald de Meersman

    1992-01-01

    To test the hypothesis that certain lifestyles may affect cardiovascular regulatory mechanisms, heart rate variability (HRV) among three age-matched groups with different lifestyles (smoking, sedentary and aerobically fit) were compared. Heart rate variability was defined as the difference in heart rate during inhalation vs. exhalation. Heart rate was obtained from normal RR intervals, using a continuous electrocardiogram recording, while subjects

  5. 12 CFR 619.9340 - Variable interest rate.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...and Banking 6 2010-01-01 2010-01-01 false Variable interest rate. 619.9340 Section 619.9340 Banks and...ADMINISTRATION FARM CREDIT SYSTEM DEFINITIONS § 619.9340 Variable interest rate. An interest rate on the outstanding loan...

  6. 12 CFR 619.9340 - Variable interest rate.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...and Banking 6 2011-01-01 2011-01-01 false Variable interest rate. 619.9340 Section 619.9340 Banks and...ADMINISTRATION FARM CREDIT SYSTEM DEFINITIONS § 619.9340 Variable interest rate. An interest rate on the outstanding loan...

  7. 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)

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

    2012-07-01

    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.

  8. An efficient software implementation of a variable rate modem

    NASA Technical Reports Server (NTRS)

    Mantha, Ramesh; Hunt, Andrew; Crozier, Stewart

    1995-01-01

    This paper describes the software implementation of the baseband portion of a variable rate modem. The modem can handle arbitrary symbol rates with a fixed input/output sample rate. This approach reduces hardware complexity related to external clock generation circuitry, offers complete flexibility in the selection of symbol rates, and conveniently accommodates symbol timing and symbol rate corrections.

  9. Variable word rate N-grams 

    E-print Network

    Gotoh, Yoshihiko; Renals, Steve

    The rate of occurrence of words is not uniform but varies from document to document. Despite this observation, parameters for conventional N-gram language models are usually derived using the assumption of a constant word rate. In this paper we...

  10. [Some regularities of the pulse rate variability].

    PubMed

    Dudin, S A; Zandanova, G I

    2011-01-01

    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

  11. Comparative analysis of variables to measure recovery rates in streams

    SciTech Connect

    Niemi, G.J. (Univ. of Minnesota-Duluth, MN (United States). Natural Resources Research Inst.); Detenbeck, N.E. (U.S. Environmental Protection Agency, Duluth, MN (United States). Environmental Research Lab.-Duluth); Perry, J.A. (Univ. of Minnesota-St. Paul, MN (United States). Dept. of Forest Resources)

    1993-09-01

    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 variables were relatively inexpensive to measure, and many would be relatively easily collected for assessing recovery rates; however, their overall explanatory power for determining recovery of streams, especially biological phenomena, was limited. Several biological variables, including gross primary production, respiration, leaf litter decomposition rates, macroinvertebrate richness, and Collembola density, could be measured reasonably well and required relatively small sample sizes for detecting recovery rates. However, collection of most of these variables was more costly than collection of chemical water-quality variables. The ultimate determination of which variables to measure in assessing recovery in a given ecosystem will need to be based on the disturbances being examined, the importance of the variables to stream health, and the available monetary resources. Generally, comprehensive analyses of recovery rates for a variety of aquatic systems will greatly increase their ability to develop a framework for predicting recovery rates and ultimately improving the quality of the environment.

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

    PubMed Central

    Pellegrino, Peter R.; Schiller, Alicia M.

    2014-01-01

    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

  13. A fixed/variable bit-rate data compression architecture

    NASA Technical Reports Server (NTRS)

    Zweigle, Gregary C.; Venbrux, Jack; Yeh, Pen-Shu

    1993-01-01

    A VLSI architecture for an adaptive data compression encoder capable of sustaining fixed or variable bit-rate output has been developed. There are three modes of operation: lossless with variable bit-rate, lossy with fixed bit-rate and lossy with variable bit-rate. For lossless encoding, the implementation is identical to the USES chip designed for Landsat 7. Obtaining a fixed bit-rate is achieved with a lossy DPCM algorithm using adaptive, nonuniform scalar quantization. In lossy mode, variable bit-rate coding uses the lossless sections of the encoder for post-DPCM entropy coding. The encoder shows excellent compression performance in comparison to other current data compression techniques. No external tables or memory are required for operation.

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

    ERIC Educational Resources Information Center

    Barkaoui, Khaled

    2010-01-01

    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…

  15. Economic and Environmental Benefits of Canopy Sensing for Variable-Rate Nitrogen Corn Fertilization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrogen (N) available to support corn production can be highly variable within fields. Canopy reflectance sensing for assessing crop N health has been proposed as a technology on which to base top-dress variable-rate N application. The objective of this research in Missouri and Nebraska was to eval...

  16. Diversification and biogeography of Juniperus (Cupressaceae): variable diversification rates and

    E-print Network

    Adams, Robert P.

    Diversification and biogeography of Juniperus (Cupressaceae): variable diversification rates: biogeography, disjunctions, Juniperus, Madrean-Tethyan vegetation, tertiary relict floras. Summary · A central and diversification history of Juniperus, which occurs in semi-arid habitats through much of the Northern Hemisphere

  17. Smoluchowski Equations for Agglomeration in Conditions of Variable Temperature and Pressure and a New Scaling of Rate Constants: Application to Nozzle-Beam Expansion.

    PubMed

    Chaiken, J; Goodisman, J; Kornilov, O

    2015-07-01

    The Smoluchowski equations provide a rigorous and efficient means for including multiple kinetic pathways when modeling coalescence growth systems. Originally written for a constant temperature and volume system, the equations must be modified if temperature and pressure vary during the coalescence time. In this paper, the equations are generalized, and adaptations appropriate to the situation presented by supersonic nozzle beam expansions are described. Given rate constants for all the cluster-cluster reactions, solution of the Smoluchowski equations would yield the abundances of clusters of all sizes at all times. This is unlikely, but we show that if these rate constants scale with the sizes of the reacting partners, the asymptotic (large size and large time) form of the cluster size distribution can be predicted. Experimentally determined distributions for He fit the predicted asymptotic distribution very well. Deviations between predicted and observed distributions allow identification of special cluster sizes that is, magic numbers. Furthermore, fitting an observed distribution to the theoretical form yields the base agglomeration cross section, from which all cluster-cluster rate constants may be obtained by scaling. Comparing the base cross section to measures of size and reactivity gives information about the coalescence process. PMID:26067086

  18. TID Effects in Space-like Variable Dose Rates

    NASA Technical Reports Server (NTRS)

    Harris, Richard D.

    2008-01-01

    The degradation of the LM193 dual voltage comparator has been studied with different types of TID dose rates. These include several different constant dose rates and a variable dose rate that simulates the behavior of a solar flare. The varying dose rate of a solar flare is the type of real total dose exposure that a space mission might see in lunar or Martian orbit. A comparison of these types of dose rates is made to explore how well the constant dose rates used for typical part testing predicts the performance during a simulated space-like mission.

  19. Variable frequency drive applications guide

    SciTech Connect

    Laloudakis, D.J.

    1991-10-01

    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.

  20. Comparison of TID Effects in Space-Like Variable Dose Rates and Constant Dose Rates

    NASA Technical Reports Server (NTRS)

    Harris, Richard D.; McClure, Steven S.; Rax, Bernard G.; Evans, Robin W.; Jun, Insoo

    2008-01-01

    The degradation of the LM193 dual voltage comparator has been studied at different TID dose rate profiles, including several different constant dose rates and a variable dose rate that simulates the behavior of a solar flare. A comparison of results following constant dose rate vs. variable dose rates is made to explore how well the constant dose rates used for typical part testing predict the performance during a simulated space-like mission. Testing at a constant dose rate equal to the lowest dose rate seen during the simulated flare provides an extremely conservative estimate of the overall amount of degradation. A constant dose rate equal to the average dose rate is also more conservative than the variable rate. It appears that, for this part, weighting the dose rates by the amount of total dose received at each rate (rather than the amount of time at each dose rate) results in an average rate that produces an amount of degradation that is a reasonable approximation to that received by the variable rate.

  1. Constraints on variable bit-rate video for ATM networks

    Microsoft Academic Search

    Amy R. Reibman; Barry G. Haskell

    1992-01-01

    Constraints on the encoded bit rate of a video signal that are imposed by a channel and encoder and decoder buffers are considered. Conditions that ensure that the video encoder and decoder buffers do not overflow or underflow when the channel can transmit a variable bit rate are presented. Using these conditions and a commonly proposed network-user contract, the effect

  2. Characteristics of Resonance in Heart Rate Variability Stimulated by Biofeedback

    Microsoft Academic Search

    Evgeny G. Vaschillo; Bronya Vaschillo; Paul M. Lehrer

    2006-01-01

    As we previously reported, resonant frequency heart rate variability biofeedback increases baroreflex gain and peak expiratory flow in healthy individuals and has positive effects in treatment of asthma patients. Biofeedback readily produces large oscillations in heart rate, blood pressure, vascular tone, and pulse amplitude via paced breathing at the specific natural resonant frequency of the cardiovascular system for each individual.

  3. Fetal heart rate and fetal heart rate variability in Lipizzaner broodmares.

    PubMed

    Baska-Vincze, Boglárka; Baska, Ferenc; Szenci, Ottó

    2015-03-01

    Monitoring fetal heart rate (FHR) and fetal heart rate variability (FHRV) helps to understand and evaluate normal and pathological conditions in the foal. The aim of this study was to establish normal heart rate reference values for the ongoing equine pregnancy and to perform a heart rate variability (HRV) time-domain analysis in Lipizzaner mares. Seventeen middle- and late-term (days 121-333) pregnant Lipizzaner mares were examined using fetomaternal electrocardiography (ECG). The mean FHR (P = 0.004) and the standard deviation of FHR (P = 0.012) significantly decreased during the pregnancy. FHR ± SD values decreased from 115 ± 35 to 79 ± 9 bpm between months 5 and 11. Our data showed that HRV in the foal decreased as the pregnancy progressed, which is in contrast with the findings of earlier equine studies. The standard deviation of normal-normal intervals (SDNN) was higher (70 ± 25 to 166 ± 108 msec) than described previously. The root mean square of successive differences (RMSSD) decreased from 105 ± 69 to 77 ± 37 msec between the 5th and 11th month of gestation. Using telemetric ECG equipment, we could detect equine fetal heartbeat on day 121 for the first time. In addition, the large differences observed in the HR values of four mare-fetus pairs in four consecutive months support the assumption that there might be 'high-HR' and 'low-HR' fetuses in horses. It can be concluded that the analysis of FHR and FHRV is a promising tool for the assessment of fetal well-being but the applicability of these parameters in the clinical setting and in studs requires further investigation. PMID:25655416

  4. Heart rate variability (HRV): an indicator of stress

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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].

  5. USE OF VARIABLE-RATE TECHNOLOGY FOR AGRONOMIC AND ENVIRONMENTAL PHOSPHORUS-BASED LIQUID SWINE MANURE MANAGEMENT

    Microsoft Academic Search

    David J. Wittry; Antonio P. Mallarino

    Land application is the most common method for utilizing manure produced by the livestock industry. Manure applications at rates that exceed crop P removal are increasing soil-test P (STP) in many regions. Precision agriculture methods and variable-rate (VR) application can improve nutrient management and provide an environmentally responsible method to distribute manure. This study used a strip- trial methodology and

  6. Analysis of the heart rate variability using stress tests

    Microsoft Academic Search

    S. V. Bozhokin; I. M. Shchenkova

    2008-01-01

    A new parameter, CS\\u000a \\u000a n\\u000a (t) (CardStress), a quantitative characteristic of the changes in the cardiovascular regulatory mechanisms based on the relative\\u000a decrease in the heart rate variability during a functional test, is proposed. Analysis of the heart rate variability was performed\\u000a in patients exposed to non-steady-state (acutely increasing) normobaric hypoxic hypoxia induced by rebreathing. The new parameter\\u000a was compared

  7. Heart rate variability interventions for concussion and rehabilitation.

    PubMed

    Conder, Robert L; Conder, Alanna A

    2014-01-01

    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

  8. Variability of Lekanesphaera monodi metabolic rates with habitat trophic status

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  9. 13 CFR 120.214 - What conditions apply for variable interest rates?

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 false What conditions apply for variable interest rates? 120.214 Section 120... § 120.214 What conditions apply for variable interest rates? A Lender may use a variable rate of interest, upon SBA's...

  10. 13 CFR 120.214 - What conditions apply for variable interest rates?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 false What conditions apply for variable interest rates? 120.214 Section 120... § 120.214 What conditions apply for variable interest rates? A Lender may use a variable rate of interest, upon SBA's...

  11. Hierarchical structure in healthy and diseased human heart rate variability

    NASA Astrophysics Data System (ADS)

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

    2004-05-01

    It is shown that the healthy and diseased human heart rate variability (HRV) 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.

  12. Analysis of Heart Rate Variability in Space Medicine

    Microsoft Academic Search

    R. M. Baevskii

    2002-01-01

    Space medicine was one of the first fields of science and practice to use the analysis of the heart rate variability (HRV) for obtaining new scientific information and solving the tasks of exercising medical control over humans working under extreme conditions. The theoretical basis of HRV analysis and different approaches to the assessment of the data obtained are presented in

  13. Variable-Rate Universal Slepian-Wolf Coding with Feedback

    E-print Network

    Variable-Rate Universal Slepian-Wolf Coding with Feedback Shriram Sarvotham, Dror Baron Abstract-- Traditional Slepian-Wolf coding assumes known statistics and relies on asymptotically long redundant bits in the encoding process. In this paper, we develop a universal scheme for Slepian-Wolf coding

  14. Segmentation of heart rate variability in different physical activities

    Microsoft Academic Search

    H. L. Chan; C. H. Lin; Y. L. Ko

    2003-01-01

    Heart rate variability is due to the interaction of sympathetic and parasympathetic nervous system. The spectral analysis of HRV provides a noninvasive probe to assess the function of the autonomic nervous system. The recording of physiological signals on free-moving subjects provides a useful tool to evaluate the autonomic states in the daily activities, but the information of activities is lack

  15. Robust estimation of fetal heart rate variability using Doppler ultrasound

    Microsoft Academic Search

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

    2003-01-01

    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

  16. Robust estimation of fetal heart rate variability using Doppler ultrasound

    Microsoft Academic Search

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

    2003-01-01

    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

  17. MULTIRESOLUTION WAVELET ANALYSIS OF HEART RATE VARIABILITY FOR

    E-print Network

    Teich, Malvin C.

    MULTIRESOLUTION WAVELET ANALYSIS OF HEART RATE VARIABILITY FOR HEART-FAILURE AND HEART, heart-transplant patients, and nor- mal subjects, using wavelet-based multiresolution tech- niques is nonstationary, reflecting biological adaptability. Multiresolution wavelet analysis [4, 5, 6, 7, 8] provides

  18. Heart Rate Variability: Effect of Exercise Intensity on Postexercise Response

    ERIC Educational Resources Information Center

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

    2012-01-01

    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…

  19. Tax Rate Variability and Public Spending as Sources of Indeterminacy

    E-print Network

    Boyer, Edmond

    Tax Rate Variability and Public Spending as Sources of Indeterminacy Teresa Lloyd-Braga1 , Leonor of public spending, financed by labor income and consump- tion taxation, on the emergence of indeterminacy of a public good. We show that the degree of public spend- ing externalities affects the combinations between

  20. Spectral Analysis of Heart Rate Variability in Sleep

    Microsoft Academic Search

    P. BUŠEK; J. OPAVSKÝ; J. SALINGER; S. NEVŠÍMALOVÁ

    2005-01-01

    Summary Spectral analysis of heart rate variability (HRV) during overnight polygraphic recording was performed in 11 healthy subjects. The total spectrum power, power of the VLF, LF and HF spectral bands and the mean R-R were evaluated. Compared to Stage 2 and Stage 4 non-REM sleep, the total spectrum power was significantly higher in REM sleep and its value gradually

  1. Ordinal pattern statistics for the assessment of heart rate variability

    NASA Astrophysics Data System (ADS)

    Graff, G.; Graff, B.; Kaczkowska, A.; Makowiec, D.; Amigó, J. M.; Piskorski, J.; Narkiewicz, K.; Guzik, P.

    2013-06-01

    The recognition of all main features of a healthy heart rhythm (the so-called sinus rhythm) is still one of the biggest challenges in contemporary cardiology. Recently the interesting physiological phenomenon of heart rate asymmetry has been observed. This phenomenon is related to unbalanced contributions of heart rate decelerations and accelerations to heart rate variability. In this paper we apply methods based on the concept of ordinal pattern to the analysis of electrocardiograms (inter-peak intervals) of healthy subjects in the supine position. This way we observe new regularities of the heart rhythm related to the distribution of ordinal patterns of lengths 3 and 4.

  2. Development of variable-rate precision spraying systems for tree crop production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Excessive pesticides are often applied to target and non-target areas in orchards and nurseries, resulting in greater production costs, worker exposure to unnecessary pesticide risks, and adverse contamination of the environment. To improve spray application efficiency, two types of variable-rate pr...

  3. A rumor spreading model with variable forgetting rate

    NASA Astrophysics Data System (ADS)

    Zhao, Laijun; Xie, Wanlin; Gao, H. Oliver; Qiu, Xiaoyan; Wang, Xiaoli; Zhang, Shuhai

    2013-12-01

    A rumor spreading model with the consideration of forgetting rate changing over time is examined in small-world networks. The mean-field equations are derived to describe the dynamics of rumor spreading in small-world networks. Further, numerical solutions are conducted on LiveJournal, an online social blogging platform, to better understand the performance of the model. Results show that the forgetting rate has a significant impact on the final size of rumor spreading: the larger the initial forgetting rate or the faster the forgetting speed, the smaller the final size of the rumor spreading. Numerical solutions also show that the final size of rumor spreading is much larger under a variable forgetting rate compared to that under a constant forgetting rate.

  4. Erosion Rate Variability in Steady State Landscapes: Sources and Implications

    NASA Astrophysics Data System (ADS)

    Hasbargen, L.; Paola, C.

    2002-12-01

    Drainage basins experiencing long term uplift and erosion can evolve to a statistically stable form (a steady state), where the average erosion rate balances the average uplift rate. The possibility that this state develops has been demonstrated by numerical and experimental models, and by some natural drainage basins. In this paper we investigate erosion rate variability in numerical and physical experiments of drainage basin scale erosion. For numerical models, the ultimate state at steady forcing conditions is a landscape that erodes everywhere at the same rate. Prior to reaching this static steady state, numerical landscapes undergo some evolution, such that the landscape experiences adjustments that lead to lateral movement of ridges and valleys, and subsequent stabilization of the network. For small scale physical experiments, such adjustments at statistical steady state can be prolonged, and a static steady state is never reached. We focus on several mechanisms that result in local variability of erosion rate for landscapes at a statistical steady state. Such mechanisms include 1) upstream area capture; 2) hillslope failures; 3) knickpoint generation and propagation; and 4) temporary deposition in valleys. Each mechanism operates at varying time scales. Upstream area capture typically involves closure of a valley, with higher erosion rates on hillslopes in adjacent valleys, and occurs over longer time scales. Divide migration is an integral part of upstream area capture. Hillslope failures are shorter time scale processes, and involve local fluctuations in erosion rate. In our physical experiments, we have observed episodes of widespread deposition in valleys, followed by knickpoint generation and excavation of the stored sediment. Such cycles occur over the time required for a knickpoint to propagate through the network. Temporary depositional cycles in our experiment are autocyclic, that is, they arise from local process interactions. The interaction of these processes leads to fairly significant variances in erosion rate across the landscape. Characteristic patterns of erosion rate exist for ridge migration, and to a lesser degree, for temporary sediment storage and knickpoint propagation. Hillslope failure patterns do not appear to have any structure. Advances in topographic measurement, surface exposure dating, and rock exhumation rates are offering the possibility that we can measure erosion rates in field settings on a very detailed basis. Theoretical and experimental data can provide valuable insights for interpreting erosion rate variability in natural settings.

  5. Heart rate variability in normal and pathological sleep.

    PubMed

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

    2013-01-01

    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

  6. Influence of travel speed on spray deposition uniformity from an air-assisted variable-rate sprayer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A newly developed LiDAR-guided air-assisted variable-rate sprayer for nursery and orchard applications was tested at various travel speeds to compare its spray deposition and coverage uniformity with constant-rate applications. Spray samplers, including nylon screens and water-sensitive papers (WSP)...

  7. Response-rate differences in variable-interval and variable-ratio schedules: An old problem revisited

    PubMed Central

    Cole, Mark R.

    1994-01-01

    In Experiment 1, a variable-ratio 10 schedule became, successively, a variable-interval schedule with only the minimum interreinforcement intervals yoked to the variable ratio, or a variable-interval schedule with both interreinforcement intervals and reinforced interresponse times yoked to the variable ratio. Response rates in the variable-interval schedule with both interreinforcement interval and reinforced interresponse time yoking fell between the higher rates maintained by the variable-ratio schedule and the lower rates maintained by the variable-interval schedule with only interreinforcement interval yoking. In Experiment 2, a tandem variable-interval 15-s variable-ratio 5 schedule became a yoked tandem variable-ratio 5 variable-interval x-s schedule, and a tandem variable-interval 30-s variable-ratio 10 schedule became a yoked tandem variable-ratio 10 variable-interval x-s schedule. In the yoked tandem schedules, the minimum interreinforcement intervals in the variable-interval components were those that equated overall interreinforcement times in the two phases. Response rates did not decline in the yoked schedules even when the reinforced interresponse times became longer. Experiment 1 suggests that both reinforced interresponse times and response rate–reinforcement rate correlations determine response-rate differences in variable-ratio 10 and yoked variable-interval schedules in rats. Experiment 2 suggests a minimal role for the reinforced interresponse time in determining response rates on tandem variable-interval 30-s variable-ratio 10 and yoked tandem variable-ratio 10 variable-interval x-s schedules in rats. PMID:16812732

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

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

    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.

  9. Patient classification based on pre-hospital heart rate variability

    Microsoft Academic Search

    Pavitra Padmanabhan; Zhiping Lin; Guang-Bin Huang; M. E. H. Ong

    2008-01-01

    Heart rate variability (HRV) is a non-invasive measurement that has shown promise as an indicator of cardiovascular, respiratory and metabolic dynamics. In this study, three different classification techniques, i.e. extreme learning machine (ELM), support vector machine (SVM) and back-propagation based neural network (BP), were investigated to classify HRV signals obtained from electrocardiograms (ECGs) of critically ill patients seen at the

  10. Variable rate vector quantization for medical image compression

    Microsoft Academic Search

    EVE A. RISKIN; TOM LOOKABAUGH; PHILIP A. CHOU; ROBERT M. GRAY

    1990-01-01

    Three techniques for variable-rate vector quantizer design are applied to medical images. The first two are extensions of an algorithm for optimal pruning in tree-structured classification and regression due to Breiman et al. The code design algorithms find subtrees of a given tree-structured vector quantizer (TSVQ), each one optimal in that it has the lowest average distortion of all subtrees

  11. SINGLE DOSE OF TIOTROPIUM DOES NOT EFFECT HEART RATE VARIABILITY

    Microsoft Academic Search

    Mehmet Unlu; Mehmet Melek; Fatma Fidan; Celal Kilit; Levent Tetik; Dayimi Kaya

    2006-01-01

    Aim: Anticholinergic drugs may alter cardiac autonomic modulation. The aim of this study was to investigate the effects of inhaled tiotropium on heart rate variability (HRV). Methods: A randomized, double-blind, crossover design study was conducted on 11 healthy volunteers. Tiotropium or placebo was administered in two different testing sessions. Time domain parameters; mean R-R interval (mean-RR), the standard deviation of

  12. Heart rate variability of children with mitral valve prolapse

    Microsoft Academic Search

    Lin Han; Ting Fei Ho; William CL Yip; Kit Yee Chan

    2000-01-01

    Studies have indicated that adult patients with mitral valve prolapse (MVP) may have autonomic dysfunction. The purpose of this study was to evaluate heart rate variability (HRV) in children with MVP. Sixty-seven children with MVP (ages 6 to 18 years; 30 boys and 37 girls) were consecutively studied and subdivided into those with or without symptoms. Thirty-seven normal age-matched children

  13. Nearest-neighbor based wavelet entropy rate measures for intrapartum fetal heart rate variability.

    PubMed

    Spilka, J; Roux, S G; Garnier, N B; Abry, P; Goncalves, P; Doret, M

    2014-01-01

    The interpretation and analysis of intrapartum fetal heart rate (FHR), enabling early detection of fetal acidosis, remains a challenging signal processing task. The ability of entropy rate measures, amongst other tools, to characterize temporal dynamics of FHR variability and to discriminate non-healthy fetuses has already been massively investigated. The present contribution aims first at illustrating that a k-nearest neighbor procedure yields estimates for entropy rates that are robust and well-suited to FHR variability (compared to the more commonly used correlation-integral algorithm). Second, it investigates how entropy rates measured on multiresolution wavelet and approximation coefficients permit to improve classification performance. To that end, a supervised learning procedure is used, that selects the time scales at which entropy rates contribute to discrimination. Significant conclusions are obtained from a high quality scalp electrode database of nearly two thousands subjects collected in a French public university hospital. PMID:25570576

  14. Erosion Rate Variability due to Tectonic Reorganization of River Networks

    NASA Astrophysics Data System (ADS)

    Willett, Sean; Yang, Rong; Chen, Chia-Yu; Goren, Liran

    2015-04-01

    Many tectonically active landscapes show disparate erosion rates and geomorphic characteristics. In particular, elevated low-relief landscapes are often interpreted as "relict" and are assumed to reflect pre-uplift tectonic conditions. We argue that tectonic deformation of the Earth's surface induces changes in the river channel network through capture and divide migration. Loss of drainage area leads to lower erosion rate through lower discharge and thus to higher surface uplift rates as erosion fails to keep up with tectonic uplift. The positive feedback of area loss amplifies these variations producing high-elevation, low relief, low erosion-rate branches of a river network that could be misconstrued as relic landscapes. We demonstrate this process through numerical models. Models that include surface strain increase variance of erosion rate as predicted. We test this idea through analysis of river profiles of tectonically active landscapes in the eastern Tibetan plateau transition and in the Central Range of Taiwan. In every case examined, we find no common uplift history and widespread evidence that divides surrounding relic landscapes are moving inward, pirating drainage area and lowering erosion rates. This argues against temporal changes in uplift rate and supports the model for in situ generation of variability of these landscapes.

  15. Heart Rate Variability During Early Adaptation to Space

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  16. Compact solid state high repetition rate variable amplitude pulse generator

    Microsoft Academic Search

    Scott J. Pendleton; Daniel Singleton; Andras Kuthi; Martin A. Gundersen

    2009-01-01

    Presented is a solid state high repetition-rate pulse generator with adjustable output amplitude, together with a resonant LC charger. This pulse generator was designed for transient plasma production for ignition and other aerospace plasma applications. The design of the pulse-forming network makes use of commercially available insulated gate bipolar transistors (IGBT) switching a capacitor bank into a METGLAS transformer together

  17. Applicability and variability of liver stiffness measurements according to probe position

    Microsoft Academic Search

    Patrick Ingiliz; Kim Pav Chhay; Pascal Lebray; Yen Ngo; Yves Benhamou; Dominique Thabut; Vlad Ratziu; Mona Munteanu; Dominique Roulot; Thierry Poynard

    2009-01-01

    AIM: To investigate the liver stiffness measurement (LSM) applicability and variability with reference to three probe positions according to the region of liver biopsy. METHODS: The applicability for LSM was defined as at least 10 valid measurements with a success rate greater than 60% and an interquartile range\\/median LSM < 30%. The LSM variability compared the inter-position concordance and the

  18. Heart rate variability during cycloergometric exercise or judo wrestling eliciting the same heart rate level

    Microsoft Academic Search

    François Cottin; François Durbin; Yves Papelier

    2004-01-01

    This study compared heart rate variability (HRV) in ten male judokas between two types of exercise eliciting the same near-maximal average heart rate (HR): judo wrestling vs. cycloergometric bout. Beat-to-beat RR intervals were recorded during (1) a 4-min judo randori (wrestling); (2) a 4-min cycloergometric exercise eliciting maximal oxygen consumption ( V?O 2MAX). Time series were analyzed both by short

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  20. [Study of exercise heart rate variability based on correlation dimension].

    PubMed

    Li, Xia; Kang, Tianliang; Quan, Haiying; Liu, Jinghua; Xu, Jin; Tian, Xin

    2009-10-01

    This paper is mainly devoted to the relationship between the correlation dimension (CD) of exercise heart rate variability (EHRV) and the status of cardiovascular function. Hypertensive patients and healthy people were enrolled in two contrast groups. Dynamic electrocardiograph (ECG) in step exercise was recorded. EHRV was extracted by wavelet transform. The CDs in the whole course of exercise and in three stages of exercise were calculated, the three stages being named rest-before-exercise, during-exercise, and after-exercise. SPSS software was used for statistical analysis. The results revealed all the CDs showed significant difference between two groups except that in the stage of during exercise. By discrimination analysis, the average correct rate was 92.2%. It indicated that the CD in stress status probably could be an effective non-linear parameter for assessing cardiovascular function status. PMID:19947468

  1. Heart Rate Variability in Sleep-Related Migraine without Aura

    PubMed Central

    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

    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

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

    Microsoft Academic Search

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

    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

  3. Can Photoplethysmography Variability Serve as an Alternative Approach to Obtain Heart Rate Variability Information?

    Microsoft Academic Search

    Sheng Lu; He Zhao; Kihwan Ju; Kunson Shin; Myoungho Lee; Kirk Shelley; Ki H. Chon

    2008-01-01

    Heart rate variability (HRV), extracted from an electrocardiogram, is known to be a noninvasive indicator reflecting the dynamic\\u000a interplay between perturbations to cardiovascular function and the dynamic response of the cardiovascular regulatory system.\\u000a Photoplethysmography (PPG) is a noninvasive method to monitor arterial oxygen saturation on a continuous basis. Given the\\u000a rich cardiovascular information in the PPG signal, and the ubiquity

  4. ARTiiFACT: a tool for heart rate artifact processing and heart rate variability analysis

    Microsoft Academic Search

    Tobias Kaufmann; Stefan Sütterlin; Stefan M. Schulz; Claus Vögele

    The importance of appropriate handling of artifacts in interbeat interval (IBI) data must not be underestimated. Even a single\\u000a artifact may cause unreliable heart rate variability (HRV) results. Thus, a robust artifact detection algorithm and the option\\u000a for manual intervention by the researcher form key components for confident HRV analysis. Here, we present ARTiiFACT, a software\\u000a tool for processing electrocardiogram

  5. Heart Rate Variability Dynamics for the Prognosis of Cardiovascular Risk

    PubMed Central

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

    2011-01-01

    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

  6. Heart rate variability at different thermal comfort levels.

    PubMed

    Liu, Weiwei; Lian, Zhiwei; Liu, Yuanmou

    2008-06-01

    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

  7. Does Baseline Heart Rate Variability Reflect Stable Positive Emotionality?

    PubMed

    Silvia, Paul J; Jackson, Bryonna A; Sopko, Rachel S

    2014-11-01

    Several recent studies have found significant correlations, medium in effect size, between baseline heart rate variability (HRV) and measures of positive functioning, such as extraversion, agreeableness, and trait positive affectivity. Other research, however, has suggested an optimal level of HRV and found nonlinear effects. In the present study, a diverse sample of 239 young adults completed a wide range of measures that reflect positive psychological functioning, including personality traits, an array of positive emotions (measured with the Dispositional Positive Emotions Scale), and depression, anxiety, and stress symptoms (measured with the DASS and CESD). HRV was measured with a 6-minute baseline period and quantified using many common HRV metrics (e.g., respiratory sinus arrhythmia, root mean square of successive differences, and others), and potentially confounding behavioral and lifestyle variables (e.g., BMI, caffeine and nicotine use, sleep quality) were assessed. Neither linear nor non-linear effects were found, and the effect sizes were small and near zero. The findings suggest that the cross-sectional relationship between HRV and positive experience deserves more attention and meta-analytic synthesis. PMID:25147421

  8. Isoprene and monoterpene emission rate variability: Observations with Eucalyptus and emission rate algorithm development

    NASA Astrophysics Data System (ADS)

    Guenther, Alex B.; Monson, Russell K.; Fall, Ray

    1991-06-01

    Variability in the emission rates of isoprene and monoterpenes from individual leaves of Eucalyptus globulus was investigated with a laboratory gas exchange system and an environmental control leaf cuvette. For individual leaves, with constant environmental conditions, short-term (1 hour) fluctuations in isoprene emission rates were less than 3% while day-to-day fluctuations averaged 14%. Leaf-to-leaf variations were much larger (62%). Fluctuations with time and leaf-to-leaf variability in CO2 assimilation rates were of the same order as isoprene, while monoterpene variations were higher. Leaf age was identified as one of the factors contributing to leaf-to-leaf variability in CO2 assimilation and isoprene and monoterpene emission rates. Monoterpene emission rates were not influenced by light intensity or CO2 mixing ratio. The observed temperature dependence was the same for ?-pinene and 1,8-cineole (an oxygenated monoterpene) and is similar to the temperature dependence of monoterpene emission rates reported by other investigators. Isoprene emissions were slightly dependent on humidity (1-3% increase in emission per 10% increase in relative humidity) and responded only to very low (<100 ppm) or very high (>600 ppm) CO2 mixing ratios. Isoprene emission was associated with the abaxial leaf side, which contains stomatal pores, while monoterpenes were emitted primarily from the adaxial side, which lacks stomatal pores. The temperature and light dependence of isoprene emission closely resembles relationships observed for electron transport in plant chloroplasts. For this reason, we have used a mechanistic electron transport model as the basis for an empirical isoprene emission rate model. The emission rate variation predicted by this model was within 10% of observed values for 62% of the 255 observations at light-saturated conditions and temperatures between 23° and 33°C. The entire data base includes over 600 observations at leaf temperatures ranging between 12° and 50°C and light intensities between 0 and 2000 ?mol m-2 s-1. Nearly two thirds of the emission rates predicted for the entire data base were within a factor of 1.25, and 89% were within a factor of 2. The algorithms developed in this study provide a solid physiological basis for future efforts to model the biogenic flux of isoprene and monoterpenes into the atmosphere.

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

    E-print Network

    Gonçalves, Paulo

    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

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

    E-print Network

    Gao, Jianbo

    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

  11. Testing the Effect of Metabolic Rate on DNA Variability at the Intra-Specific Level

    PubMed Central

    McGaughran, Angela; Holland, Barbara R.

    2010-01-01

    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, we did not find significant evidence that contemporary metabolic rates directly correlate with mutation rate (i.e., root-to-tip distance) once the underlying phylogeny is taken into account. However, we did find significant evidence that metabolic rate is dependent on the underlying mtDNA tree, or in other words, lineages with related mtDNA also have similar metabolic rates. We anticipate that future analyses which apply this methodology to datasets with longer sequences, more taxa, or greater variability will have more power to detect a significant direct correlation between metabolic rate and mutation rate. We conclude with suggestions for future analyses that would extend the preliminary approach applied here, in particular highlighting ways to tease apart oxidative stress effects from the effects of population size and/or selection coefficients operating on the molecular evolutionary rate. PMID:20300626

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

    PubMed Central

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

    2014-01-01

    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

  13. Emissions variability processor (EMVAP): design, evaluation, and application.

    PubMed

    Paine, Robert; Szembek, Carlos; Heinold, David; Knipping, Eladio; Kumar, Naresh

    2014-12-01

    Emissions of pollutants such as SO2 and NOx from external combustion sources can vary widely depending on fuel sulfur content, load, and transient conditions such as startup, shutdown, and maintenance/malfunction. While monitoring will automatically reflect variability from both emissions and meteorological influences, dispersion modeling has been typically conducted with a single constant peak emission rate. To respond to the need to account for emissions variability in addressing probabilistic 1-hr ambient air quality standards for SO2 and NO2, we have developed a statistical technique, the Emissions Variability Processor (EMVAP), which can account for emissions variability in dispersion modeling through Monte Carlo sampling from a specified frequency distribution of emission rates. Based upon initial AERMOD modeling of from 1 to 5 years of actual meteorological conditions, EMVAP is used as a postprocessor to AERMOD to simulate hundreds or even thousands of years of concentration predictions. This procedure uses emissions varied hourly with a Monte Carlo sampling process that is based upon the user-specified emissions distribution, from which a probabilistic estimate can be obtained of the controlling concentration. EMVAP can also accommodate an advanced Tier 2 NO2 modeling technique that uses a varying ambient ratio method approach to determine the fraction of total oxides of nitrogen that are in the form of nitrogen dioxide. For the case of the 1-hr National Ambient Air Quality Standards (NAAQS, established for SO2 and NO2), a "critical value" can be defined as the highest hourly emission rate that would be simulated to satisfy the standard using air dispersion models assuming constant emissions throughout the simulation. The critical value can be used as the starting point for a procedure like EMVAP that evaluates the impact of emissions variability and uses this information to determine an appropriate value to use for a longer-term (e.g., 30-day) average emission rate that would still provide protection for the NAAQS under consideration. This paper reports on the design of EMVAP and its evaluation on several field databases that demonstrate that EMVAP produces a suitably modest overestimation of design concentrations. We also provide an example of an EMVAP application that involves a case in which a new emission limitation needs to be considered for a hypothetical emission unit that has infrequent higher-than-normal SO2 emissions. Implications: Emissions of pollutants from combustion sources can vary widely depending on fuel sulfur content, load, and transient conditions such as startup and shutdown. While monitoring will automatically reflect this variability on measured concentrations, dispersion modeling is typically conducted with a single peak emission rate assumed to occur continuously. To realistically account for emissions variability in addressing probabilistic 1-hr ambient air quality standards for SO2 and NO2, the authors have developed a statistical technique, the Emissions Variability Processor (EMVAP), which can account for emissions variability in dispersion modeling through Monte Carlo sampling from a specified frequency distribution of emission rates. PMID:25562935

  14. 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) Æ Interbeat

  15. Noninvasive Sudden Death Risk Stratification: Heart Rate Variability and Turbulence, and QT Dynamicity

    Microsoft Academic Search

    Antonio Vincenti; Stefano Pedretti

    Variability in sinus-rhythm pacemaker activity over time is a major physiological characteristic of heart-rate behavior, and\\u000a many cardiovascular and metabolic conditions result in a change in heart rate variability. The numerous studies of time- and\\u000a frequency-dependent variability have improved our knowledge of the physiological and pathological patterns of heart-rate variability\\u000a (HRV). The standard deviation of 24-h mean RR value (SDNN),

  16. Extraction of Heart Rate Variability from Smartphone Photoplethysmograms

    PubMed Central

    Peng, Rong-Chao; Zhou, Xiao-Lin; Lin, Wan-Hua; Zhang, Yuan-Ting

    2015-01-01

    Heart rate variability (HRV) is a useful clinical tool for autonomic function assessment and cardiovascular diseases diagnosis. It is traditionally calculated from a dedicated medical electrocardiograph (ECG). In this paper, we demonstrate that HRV can also be extracted from photoplethysmograms (PPG) obtained by the camera of a smartphone. Sixteen HRV parameters, including time-domain, frequency-domain, and nonlinear parameters, were calculated from PPG captured by a smartphone for 30 healthy subjects and were compared with those derived from ECG. The statistical results showed that 14 parameters (AVNN, SDNN, CV, RMSSD, SDSD, TP, VLF, LF, HF, LF/HF, nLF, nHF, SD1, and SD2) from PPG were highly correlated (r > 0.7, P < 0.001) with those from ECG, and 7 parameters (AVNN, TP, VLF, LF, HF, nLF, and nHF) from PPG were in good agreement with those from ECG within the acceptable limits. In addition, five different algorithms to detect the characteristic points of PPG wave were also investigated: peak point (PP), valley point (VP), maximum first derivative (M1D), maximum second derivative (M2D), and tangent intersection (TI). The results showed that M2D and TI algorithms had the best performance. These results suggest that the smartphone might be used for HRV measurement. PMID:25685174

  17. Extraction of heart rate variability from smartphone photoplethysmograms.

    PubMed

    Peng, Rong-Chao; Zhou, Xiao-Lin; Lin, Wan-Hua; Zhang, Yuan-Ting

    2015-01-01

    Heart rate variability (HRV) is a useful clinical tool for autonomic function assessment and cardiovascular diseases diagnosis. It is traditionally calculated from a dedicated medical electrocardiograph (ECG). In this paper, we demonstrate that HRV can also be extracted from photoplethysmograms (PPG) obtained by the camera of a smartphone. Sixteen HRV parameters, including time-domain, frequency-domain, and nonlinear parameters, were calculated from PPG captured by a smartphone for 30 healthy subjects and were compared with those derived from ECG. The statistical results showed that 14 parameters (AVNN, SDNN, CV, RMSSD, SDSD, TP, VLF, LF, HF, LF/HF, nLF, nHF, SD1, and SD2) from PPG were highly correlated (r > 0.7, P < 0.001) with those from ECG, and 7 parameters (AVNN, TP, VLF, LF, HF, nLF, and nHF) from PPG were in good agreement with those from ECG within the acceptable limits. In addition, five different algorithms to detect the characteristic points of PPG wave were also investigated: peak point (PP), valley point (VP), maximum first derivative (M1D), maximum second derivative (M2D), and tangent intersection (TI). The results showed that M2D and TI algorithms had the best performance. These results suggest that the smartphone might be used for HRV measurement. PMID:25685174

  18. Classification of heart rate variability in patients with mild hypertension.

    PubMed

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

    1997-12-01

    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

  19. Heart rate variability as a biomarker of fibromyalgia syndrome

    PubMed Central

    Staud, Roland

    2009-01-01

    Fibromyalgia (FM) is a chronic pain syndrome characterized by widespread mechanical tenderness, fatigue, nonrefreshing sleep and depressed mood. Several biological abnormalities have been described in FM patients, including elevated substance P in the cerebrospinal fluid, increased CNS sensitivity to painful and nonpainful stimuli and pervasive dysfunction of the autonomic nervous system (ANS). Such ANS abnormalities include, but are not limited to: tachycardia, postural intolerance, Raynaud’s phenomenon, and diarrhea or constipation. Heart rate variability (HRV) analysis of FM patients can be used to assess ANS dysfunction, specifically related to sympathovagal balance, which has provided evidence for nonabating sympathetic hyperactivity in this chronic pain population. Although not specific for FM, ANS dysfunction can be readily determined by HRV analysis requiring only computer analysis of electrocardiogram recordings by commercially available software. HRV has been shown to correlate with FM pain and is sensitive to change; in particular, pain related to physical and mental stressors. Thus, ANS dysfunction as assessed by HRV analysis may serve as a useful biomarker, and may become part of future FM diagnostic criteria and serve as a surrogate end point in clinical trials. PMID:19890437

  20. Heart rate variability in patients with untreated Parkinson's disease.

    PubMed

    Kallio, M; Haapaniemi, T; Turkka, J; Suominen, K; Tolonen, U; Sotaniemi, K; Heikkilä, V P; Myllylä, V

    2000-11-01

    The aim of this study was to evaluate cardiovascular responses as a marker of autonomic nervous system (ANS) disturbances in patients with untreated Parkinson's disease (PD) and to assess the relationship between them and the clinical characteristics of PD. The ANS functions were investigated in 50 patients with PD and 55 healthy subjects by measuring standard cardiovascular autonomic reflexes and heart rate variability (HRV) at rest using spectral analysis (the autoregressive model and the fast Fourier transformation), the percentage of the counts of beat-to-beat variation greater than 50 ms and the fractal dimension. Significantly attenuated HRV and deficient blood pressure reaction to tilting were found in the PD patient group. The patients with hypokinesia/rigidity as the initial symptom of PD had a more pronounced HRV deficit than those with tremor onset. Untreated PD patients suffer significant failure in cardiovascular nervous system regulation, and in patients with hypokinesia/rigidity as their initial disease manifestation the risk of this ANS dysfunction is high. However, in the early stages of PD these changes did not reach significance at individual level. PMID:11136353

  1. Nicotine Acutely Inhibits Erectile Tumescence by Altering Heart Rate Variability

    PubMed Central

    Harte, Christopher B.

    2014-01-01

    Objective To examine potential mechanisms underlying nicotine’s effects on male sexual arousal by exploring the mediating role of heart rate variability (HRV). Methods The sample comprised 22 healthy, nicotine-naïve men (Mage = 20.91 years; SD = 2.43). Data were taken from a double-blind, randomized, placebo-controlled, crossover trial previously completed and published elsewhere. During each laboratory visit, time-domain parameters of HRV (standard deviation of normal-to-normal [NN] intervals [SDNN], square root of the mean squared difference of successive NN intervals [RMSSD], percent of NN intervals for which successive heartbeat intervals differed by at least 50 ms [pNN50]) were assessed, as well as objective (via penile plethysmography) and subjective indices of sexual arousal. Results Acute nicotine ingestion (compared to placebo) was associated with dysregulated sympathovagal balance, which in turn was related to relatively reduced erectile tumescence. HRV did not mediate relations between nicotine intake and self-reported indices of sexual arousal. Conclusions HRV mediated the association between nicotine ingestion and erectile capacity. Findings suggest that dysfunctional cardiac autonomic tone may be an underlying mechanism by which nicotine exerts its deleterious effects on erectile health. PMID:24642073

  2. Heart rate variability: a tool to explore the sleeping brain?

    PubMed Central

    Chouchou, Florian; Desseilles, Martin

    2014-01-01

    Sleep is divided into two main sleep stages: (1) non-rapid eye movement sleep (non-REMS), characterized among others by reduced global brain activity; and (2) rapid eye movement sleep (REMS), characterized by global brain activity similar to that of wakefulness. Results of heart rate variability (HRV) analysis, which is widely used to explore autonomic modulation, have revealed higher parasympathetic tone during normal non-REMS and a shift toward sympathetic predominance during normal REMS. Moreover, HRV analysis combined with brain imaging has identified close connectivity between autonomic cardiac modulation and activity in brain areas such as the amygdala and insular cortex during REMS, but no connectivity between brain and cardiac activity during non-REMS. There is also some evidence for an association between HRV and dream intensity and emotionality. Following some technical considerations, this review addresses how brain activity during sleep contributes to changes in autonomic cardiac activity, organized into three parts: (1) the knowledge on autonomic cardiac control, (2) differences in brain and autonomic activity between non-REMS and REMS, and (3) the potential of HRV analysis to explore the sleeping brain, and the implications for psychiatric disorders. PMID:25565936

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

    Microsoft Academic Search

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

    2000-01-01

    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

  4. Exercise Training Improves Heart Rate Variability after Methamphetamine Dependency

    PubMed Central

    Dolezal, Brett A.; Chudzynski, Joy; Dickerson, Daniel; Mooney, Larissa; Rawson, Richard A.; Garfinkel, Alan; Cooper, Christopher B.

    2014-01-01

    Purpose Heart rate variability (HRV) reflects a healthy autonomic nervous system and is increased with physical training. Methamphetamine dependence (MD) causes autonomic dysfunction and diminished HRV. We compared recently abstinent MD participants with age-matched, drug free controls (DF) and also investigated whether HRV can be improved with exercise training in the MD participants. Methods In 50 participants (MD=28; DF=22) resting heart rate (R-R intervals) was recorded over 5 min while seated using a monitor affixed to a chest strap. Previously reported time-domain (SDNN, RMSSD, pNN50) and frequency-domain (LFnu, HFnu, LF/HF) parameters of HRV were calculated with customized software. MD were randomized to thrice weekly exercise training (ME=14) or equal attention without training (MC=14) over 8 weeks. Groups were compared using paired and unpaired t-tests. Statistical significance was set at P?0.05. Results Participant characteristics were matched between groups: age 33±6 years; body mass 82.7±12 kg, BMI 26.8±4.1 kg•min?2, mean±SD. Compared with DF, the MD group had significantly higher resting heart rate (P<0.05), LFnu, and LF/HF (P<0.001) as well as lower SDNN, RMSSD, pNN50 and HFnu (all P<0.001). At randomization, HRV indices were similar between ME and MC groups. However, after training, the ME group significantly (all P<0.001) increased SDNN (+14.7±2.0 ms, +34%), RMSSD (+19.6±4.2 ms, +63%), pNN50 (+22.6±2.7%, +173%), HFnu (+14.2±1.9, +60%) and decreased HR (?5.2±1.1 beats·min?1, ?7%), LFnu (?9.6±1.5, ?16%) and LF/HF (?0.7±0.3, ?19%). These measures did not change from baseline in the MC group. Conclusion HRV, based on several conventional indices, was diminished in recently abstinent, methamphetamine dependent individuals. Moreover, physical training yielded a marked increase of HRV representing increased vagal modulation or improved autonomic balance. PMID:24162556

  5. Population growth rates: issues and an application.

    PubMed Central

    Godfray, H Charles J; Rees, Mark

    2002-01-01

    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

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

    PubMed Central

    Weitz, Gunther; Bonnemeier, Hendrik; Süfke, Sven; Wellhöner, Peter; Lehnert, Hendrik; Dodt, Christoph

    2013-01-01

    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

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

    PubMed Central

    Bidmon, Sonja; Röttl, Johanna

    2014-01-01

    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

  8. 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 assessed via classical time and frequency domain measures. Mean systolic and dias- tolic blood pressure

  9. A comparison of subjective and mathematical estimations of fetal heart rate variability

    Microsoft Academic Search

    Adam J. Wolfberg; David J. Derosier; Trevor Roberts; Zeeshan Syed; Gari D. Clifford; David Acker; Adre Du Plessis

    2008-01-01

    Objectives. To develop a computerized algorithm to quantify fetal heart rate (FHR) variability and compare it to perinatologists' interpretation of FHR variability. Methods. FHR variability was calculated using data from 30 women who had a fetal scalp electrode placed for a clinical indication, and compared to the assessment of FHR variability from four perinatologists who interpreted paper tracings of the

  10. Estimating mental fatigue based on electroencephalogram and heart rate variability

    NASA Astrophysics Data System (ADS)

    Zhang, Chong; Yu, Xiaolin

    2010-01-01

    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.

  11. 74-2012 Measuring the impact of monetary variables on the Algerian dinar exchange rate

    E-print Network

    Paris-Sud XI, Université de

    /2014 57 74-2012 Measuring the impact of monetary variables on the Algerian dinar exchange rate on the Algérien Dinar Exchange rate against United States Dollar during the period 1970-2012. Using partial Adjustment model, Results showed that the only variable that effects the Algerian Dinar exchange rate

  12. Large Deviations Analysis of Variable-Rate Slepian-Wolf Coding

    E-print Network

    Merhav, Neri

    Large Deviations Analysis of Variable-Rate Slepian-Wolf Coding Nir Weinberger and Neri Merhav of ensembles of random binning Slepian-Wolf codes, where each type class of the source might have a different be achieved using variable-rate coding, at the price of a finite excess rate exponent. Index Terms Slepian-Wolf

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

    E-print Network

    Schroeder, Charles Grant

    1996-01-01

    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...

  14. 1996 International Conference on Parallel Processing Analysis of Heart Rate Variability on a Massively Parallel

    E-print Network

    Bhandarkar, Suchendra "Suchi" M.

    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

  15. 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

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

    E-print Network

    Boyer, Edmond

    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

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

    E-print Network

    Abry, Patrice

    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

  18. 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

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

    E-print Network

    Gonçalves, Paulo

    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

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

    E-print Network

    Teich, Malvin C.

    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

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

    E-print Network

    Schroeder, Charles Grant

    1996-01-01

    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...

  2. On the nature of heart rate variability in a breathing normal subject: A stochastic process analysis

    NASA Astrophysics Data System (ADS)

    Buchner, Teodor; Petelczyc, Monika; ?ebrowski, Jan J.; Prejbisz, Aleksander; Kabat, Marek; Januszewicz, Andrzej; Piotrowska, Anna Justyna; Szelenberger, Waldemar

    2009-06-01

    Human heart rate is moderated by the autonomous nervous system acting predominantly through the sinus node (the main cardiac physiological pacemaker). One of the dominant factors that determine the heart rate in physiological conditions is its coupling with the respiratory rhythm. Using the language of stochastic processes, we analyzed both rhythms simultaneously taking the data from polysomnographic recordings of two healthy individuals. Each rhythm was treated as a sum of a deterministic drift term and a diffusion term (Kramers-Moyal expansion). We found that normal heart rate variability may be considered as the result of a bidirectional coupling of two nonlinear oscillators: the heart itself and the respiratory system. On average, the diffusion (noise) component measured is comparable in magnitude to the oscillatory (deterministic) term for both signals investigated. The application of the Kramers-Moyal expansion may be useful for medical diagnostics providing information on the relation between respiration and heart rate variability. This interaction is mediated by the autonomous nervous system, including the baroreflex, and results in a commonly observed phenomenon—respiratory sinus arrhythmia which is typical for normal subjects and often impaired by pathology.

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

    Microsoft Academic Search

    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

    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

  4. Genus-Specific Substitution Rate Variability among Picornaviruses ?†

    PubMed Central

    Hicks, Allison L.; Duffy, Siobain

    2011-01-01

    Picornaviruses have some of the highest nucleotide substitution rates among viruses, but there have been no comparisons of evolutionary rates within this broad family. We combined our own Bayesian coalescent analyses of VP1 regions from four picornaviruses with 22 published VP1 rates to produce the first within-family meta-analysis of viral evolutionary rates. Similarly, we compared our rate estimates for the RNA polymerase 3Dpol gene from five viruses to four published 3Dpol rates. Both a structural and a nonstructural gene show that enteroviruses are evolving, on average, a half order of magnitude faster than members of other genera within the Picornaviridae family. PMID:21613392

  5. Heart rate and heart rate variability modification in chronic insomnia patients.

    PubMed

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

    2014-01-01

    Chronic insomnia is highly prevalent in the general population, provoking personal distress and increased risk for psychiatric and medical disorders. Autonomic hyper-arousal could be a pathogenic mechanism of chronic primary insomnia. The aim of this study was to investigate autonomic activity in patients with chronic primary insomnia by means of heart rate variability (HRV) analysis. Eighty-five consecutive patients affected by chronic primary insomnia were enrolled (38 men and 47 women; mean age: 53.2 ± 13.6). Patients were compared with a control group composed of 55 healthy participants matched for age and gender (23 men and 32 women; mean age: 54.2 ± 13.9). Patients underwent an insomnia study protocol that included subjective sleep evaluation, psychometric measures, and home-based polysomnography with evaluation of HRV in wake before sleep, in all sleep stages, and in wake after final awakening. Patients showed modifications of heart rate and HRV parameters, consistent with increased sympathetic activity, while awake before sleep and during Stage-2 non-REM sleep. No significant differences between insomniacs and controls could be detected during slow-wave sleep, REM sleep, and post-sleep wake. These results are consistent with the hypothesis that autonomic hyper-arousal is a major pathogenic mechanism in primary insomnia, and confirm that this condition is associated with an increased cardiovascular risk. PMID:24128278

  6. Changes in Heart Rate Variability after Coronary Artery Bypass Grafting and Clinical Importance of These Findings

    PubMed Central

    Lakusic, Nenad; Mahovic, Darija; Cerkez Habek, Jasna; Novak, Miroslav; Cerovec, Dusko

    2015-01-01

    Heart rate variability is a physiological feature indicating the influence of the autonomic nervous system on the heart rate. Association of the reduced heart rate variability due to myocardial infarction and the increased postinfarction mortality was first described more than thirty years ago. Many studies have unequivocally demonstrated that coronary artery bypass grafting surgery generally leads to significant reduction in heart rate variability, which is even more pronounced than after myocardial infarction. Pathophysiologically, however, the mechanisms of heart rate variability reduction associated with acute myocardial infarction and coronary artery bypass grafting are different. Generally, heart rate variability gradually recovers to the preoperative values within six months of the procedure. Unlike the reduced heart rate variability in patients having sustained myocardial infarction, a finding of reduced heart rate variability after coronary artery bypass surgery is not considered relevant in predicting mortality. Current knowledge about changes in heart rate variability in coronary patients and clinical relevance of such a finding in patients undergoing coronary artery bypass grafting are presented.

  7. HEART RATE VARIABILITY AS DETERMINISM WITH JUMP STOCHASTIC PARAMETERS

    E-print Network

    Bollt, Erik

    1. Introduction. Modeling the behavior of human cardiovascular system is an interest- ing problem, AND ERIK BOLLT§ Abstract. We use measured heart rate information (RR intervals) to develop a one with persistence which causes the heart rate and rhythm system to wander about a bifurcation point. We propose

  8. The influence of ventilatory control on heart rate variability in children

    Microsoft Academic Search

    Craig A. Williams; Philippe Lopes

    2002-01-01

    The aim of this study was to determine the influence of breathing frequency and tidal volume on resting heart rate variability in children aged 9 years ( n = 29) and 16 years ( n = 19). Heart rate variability was measured in four conditions: (1) without the control of ventilation followed at random by (2) a fixed breathing frequency

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

    Microsoft Academic Search

    M. H. Bonnet; D. L. Arand

    1997-01-01

    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

  10. Resting Enhanced Frequency Domain Analysis Improves Heart Rate Variability Sensitivity in Early and Late Diabetics

    Microsoft Academic Search

    A. I. Vinik; B. Aysin; J. Colombo

    Background: The addition of frequency domain (FD) analysis of respiratory activity to FD of heart rate variability (HRV) is necessary to independently and simultaneously analyze both autonomic (ANS) branches non-invasively and quantitatively. This method has been presented as the enhanced FD analysis (EFDA) approach. Our clinical results have shown that EFDA improves FD heart rate variability (fdHRV) sensitivity in early

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

    Microsoft Academic Search

    J M Serrador; H C Finlayson; R L Hughson

    1999-01-01

    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

  12. Heart rate variability characterization in daily physical activities using wavelet analysis and multilayer fuzzy activity clustering

    Microsoft Academic Search

    Hsiao-Lung Chan; Shih-Chin Fang; Yu-Lin Ko; Ming-An Lin; Hui-Hsun Huang; C.-H. Lin

    2006-01-01

    A portable data recorder was developed to parallel measure the electrocardiogram and body accelerations. A multilayer fuzzy clustering algorithm was proposed to classify the physical activity based on body accelerations. Discrete wavelet transform was incorporated to retrieve time-varying characteristics of heart rate variability under different physical activities. Nine healthy subjects were included to investigate activity-related heart rate variability during 24

  13. A variable-data-rate, multimode quadriphase modem.

    NASA Technical Reports Server (NTRS)

    Allen, R. W.; Batson, B. H.

    1973-01-01

    This paper describes the design and performance of a highly versatile modulator and demodulator recently developed to facilitate the evaluation of various digital communications links. The modem is capable of either PSK or QPSK operation and can accommodate a very wide range of continuously tunable data rates (1 kbps to 30 Mbps in each of two channels). In the QPSK mode, operation is possible using either a single serial data stream (single channel operation) or using two mutually independent, unrelated, and asynchronous data streams (dual-channel operation). Integrate and dump detectors are used at the demodulator for regeneration of the data stream(s). Measurements indicate that the performance of the overall system (including the bit detectors) is within 2 dB of the theoretically optimum performance of either PSK or QPSK at any rate within the range of rates provided by the modem, and is within 1 dB of theoretical over most of the range of rates.

  14. Variability in nest survival rates and implications to nesting studies

    USGS Publications Warehouse

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

    1982-01-01

    We used four reasonably large samples (83-213) of Mallard (Anas platyrhynchos) and Blue-winged Teal (A. discors) nests on an interstate highway right-of-way in southcentral North Dakota to evaluate potential biases in hatch-rate estimates. Twelve consecutive, weekly searches for nests were conducted with a cable-chain drag in 1976 and 1977. Nests were revisited at weekly intervals. Four methods were used to estimate hatch rates for the four data sets: the Traditional Method, the Mayfield Method, and two modifications of the Mayfield Method that are sometimes appropriate when daily mortality rates of nests are not constant. Hatch rates and the average age of nests at discovery declined as the interval between searches decreased, suggesting that mortality rates were not constant in our samples. An analysis of variance indicated that daily mortality rates varied with the age of nests in all four samples. Mortality was generally highest during the early laying period, moderately high during the late laying period, and lowest during incubation. We speculate that this relationship of mortality to nest age might be due to the presence of hens at nests or to differences in the vulnerability of nest sites to predation. A modification of the Mayfield Method that accounts for age-related variation in nest mortality was most appropriate for our samples. We suggest methods for conducting nesting studies and estimating nest success for species possessing similar nesting habits.

  15. Relative influence of age, resting heart rate and sedentary life style in short-term analysis of heart rate variability

    Microsoft Academic Search

    E. R. Migliaro; P. Contreras; S. Bech; A. Etxagibel; M. Castro; R. Ricca; K. Vicente

    2001-01-01

    In order to assess the relative influence of age, resting heart rate (HR) and sedentary life style, heart rate variability (HRV) was studied in two different groups. The young group (YG) consisted of 9 sedentary subjects aged 15 to 20 years (YG-S) and of 9 nonsedentary volunteers (YG-NS) also aged 15 to 20. The elderly sedentary group (ESG) consisted of

  16. Statistical analysis of heart rate and heart rate variability monitoring through the use of smart phone cameras.

    PubMed

    Bolkhovsky, Jeffrey B; Scully, Christopher G; Chon, Ki H

    2012-01-01

    Video recordings of finger tips made using a smartphone camera contain a pulsatile component caused by the cardiac pulse equivalent to that present in a photoplethysmographic signal. By performing peak detection on the pulsatile signal it is possible to extract a continuous heart rate signal. We performed direct comparisons between 5-lead electrocardiogram based heart rate variability measurements and those obtained from an iPhone 4s and Motorola Droid derived pulsatile signal to determine the accuracy of heart rate variability measurements obtained from the smart phones. Monitoring was performed in the supine and tilt positions for independent iPhone 4s (2 min recordings, n=9) and Droid (5 min recordings, n=13) experiments, and the following heart rate and heart rate variability parameters were estimated: heart rate, low frequency power, high frequency power, ratio of low to high frequency power, standard deviation of the RR intervals, and root mean square of successive RR-differences. Results demonstrate that accurate heart rate variability parameters can be obtained from smart phone based measurements. PMID:23366214

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

    E-print Network

    Paris-Sud XI, Université de

    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

  18. Spectral analysis of heart rate variability in premature infants

    Microsoft Academic Search

    Morarji Peeseya; Harel Rosen; Mark Hiatt; Thomas Hegyi

    We studied the effect of gestational age, birth weight, postmenstrual age and selected neonatal morbidities on the heart rate power spectra in preterm infants (birth weight 1075 (840, 1230) grams, gestational age 27 (26, 30) weeks). Age at testing was 6 (3, 11) days. Birth weight, gestational age and postmenstrual age were positively correlated with low frequency power (0.03- 0.39

  19. Chemical evolution, stellar nucleosynthesis, and a variable star formation rate

    Microsoft Academic Search

    Keith A. Olive; Friedrich-Karl Thielemann; James W. Truran

    1987-01-01

    The effects of a decreasing star formation rate (SFR) on the galactic abundances of elements produced in massive stars are considered. On the basis of a straightforward model of galactic evolution, relation between the upper mass limit of Type II supernovae (MSN) contributing to chemical evolution and the decline of the SFR (tau) is derived, when the oxygen abundance is

  20. Effect of Phototherapy on Neonatal Heart Rate Variability and Complexity

    Microsoft Academic Search

    Amir Weissman; Elad Berkowitz; Tatiana Smolkin; Shraga Blazer

    2009-01-01

    Background: Phototherapy is a common mode of treatment for neonatal hyperbilirubinemia. However, phototherapy has been reported to alter cardiovascular function by causing increased peripheral blood flow, diminished cardiac output and increased sympathetic activity that may be of concern particularly in sick or premature newborns. The effects of phototherapy on the autonomic nervous system modulation of heart rate in term neonates

  1. Review and classification of variability analysis techniques with clinical applications

    PubMed Central

    2011-01-01

    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

  2. COMPLEX VARIABLE BOUNDARY ELEMENT METHOD: APPLICATIONS.

    USGS Publications Warehouse

    Hromadka, T.V., II; Yen, C.C.; Guymon, G.L.

    1985-01-01

    The complex variable boundary element method (CVBEM) is used to approximate several potential problems where analytical solutions are known. A modeling result produced from the CVBEM is a measure of relative error in matching the known boundary condition values of the problem. A CVBEM error-reduction algorithm is used to reduce the relative error of the approximation by adding nodal points in boundary regions where error is large. From the test problems, overall error is reduced significantly by utilizing the adaptive integration algorithm.

  3. Online Smoothing of Variable-Bit-Rate Streaming Video

    Microsoft Academic Search

    Subhabrata Sen; Jennifer L. Rexford; Jayanta K. Dey; James F. Kurose; Donald F. Towsley

    2000-01-01

    Bandwidth smoothing techniques for stored video perform end to end workahead transmission of frames into the client playback buffer, in advance of their display times. Such techniques are very effective in reducing the burstiness of the bandwidth requirements for transmitting compressed, stored video. This paper addresses online bandwidth smoothing for a growing number of streaming video applications such as newscasts,

  4. Online smoothing of live, variable-bit-rate video

    Microsoft Academic Search

    J. Rexford; S. Sen; J. Dey; W. Feng; J. Kurose; J. Stankovic; D. Towsley

    1997-01-01

    Bandwidth smoothing techniques are effective at reducing the burstiness of a compressed, pre-recorded video stream by prefetching frames into the client playback buffer in advance of each burst. In contrast to stored video, live applications typically have limited knowledge of frame sizes and often require bounds on the delay between the source and the client(s). This paper addresses bandwidth smoothing

  5. Variable temperature effects on release rates of readily soluble nuclides

    SciTech Connect

    Kim, C.L.; Chambre, P.L.; Lee, W.W.L.; Pigford, T.H.

    1988-02-01

    In this paper we study the effect of temperature on the release rate of readily soluble nuclides, as affected by a time-temperature-dependent diffusion coefficient. In this analysis ground water fills the voids in the waste package at t=0 and one percent of the inventories of cesium and iodine are immediately dissolved into the void water. Mass transfer resistance of partly failed container and cladding is conservatively neglected. The nuclides move through the void space into the surrounding rock under a concentration gradient. We use an analytic solution to compute the nuclide concentration in the gap or void, and the mass flux rate into the porous rock. 8 refs., 4 figs.

  6. Variability in Nest Survival Rates and Implications to Nesting Studies

    NSDL National Science Digital Library

    Johnson, Douglas H.

    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.

  7. Impacts of Variable-Rate Phosphorus Fertilization Based on Dense Grid Soil Sampling on Soil-Test Phosphorus and Grain Yield of Corn and Soybean

    Microsoft Academic Search

    Manuel Bermudez; Antonio P. Mallarino

    2007-01-01

    Most agricultural fields have high soil-test phosphorus (STP) vari- ability. Variable-rate (VR) technology facilitates application of differ- ent P rates over a field and could improve nutrient application and crop yield. Replicated strip trials (6-12 ha) were established at six Iowa fields and were evaluated during 4 yr to compare VR and fixed- rate (FR) P fertilization for corn (Zea

  8. VARIABLE FIRING RATE OIL BURNER USING PULSE FUEL FLOW CONTROL.

    SciTech Connect

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

    2004-10-01

    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.

  9. Development of a novel EEG rating scale for head injury using dichotomous variables.

    PubMed

    Rae-Grant, A D; Barbour, P J; Reed, J

    1991-11-01

    We developed a new EEG rating scale for electrographic assessment of head injured patients. Phenomena present in posttraumatic EEG were scored as dichotomous variables (present or absent). These phenomena included background activity (alpha, beta, theta, delta), sleep spindles, focal abnormalities, reactivity and variability, epileptiform activity, and specific comatose patterns. Each variable was weighted according to its perceived prognostic value: i.e., normal alpha 10, flat EEG -10, spindles 4, etc. Combinations of possible scores ranged from +23 to -10. Fifty-seven EEGs from different head injured patients were independently and retrospectively analyzed by two investigators. There was a high correlation for intra- (r = 0.95) and inter- (r = 0.85) observer rating using the dichotomous test. When patients with scores over 15 (i.e., with reactive alpha) and patients with scores of -10 (i.e., ECI records) were excluded, the intra-rater and inter-rater correlations were still high (0.81 and 0.76, respectively). There was a high correlation between Glasgow outcome score at discharge and the dichotomous EEG score. This EEG scale scores most major categories of EEG activity, utilizes a multipoint scale for correlation purposes, and allows data to be analyzed in sub-categories (i.e., spindles in coma). The separate weighting score allows for refinement of the scale after data collection (i.e., to fit prospective outcome). We feel that this scale is reproducible and valid, and may be applicable to other patient groups with severely altered EEGs. PMID:1718707

  10. Forecasting the USD\\/COP Exchange Rate: A Random Walk a Variable Drift

    Microsoft Academic Search

    Peter Rowland

    2003-01-01

    This study develops three exchange rate models as well as a simple statistical model defined as a random walk with a variable drift. The exchange rate models all use the purchasing power parity hypothesis to account for the long-term relationships between prices and the exchange rate, together with error correction models to represent any shortterm dynamics. The models are estimated

  11. FEATHER GROWTH RATE AND MASS IN NEARCTIC PASSERINES WITH VARIABLE MIGRATORY BEHAVIOR AND MOLT PATTERN

    E-print Network

    DeSante, David F.

    FEATHER GROWTH RATE AND MASS IN NEARCTIC PASSERINES WITH VARIABLE MIGRATORY BEHAVIOR AND MOLT ptilochronology-based measurements of the growth rate of their tail feathers. We used between molt duration and feather quality, observed variation in feather growth rate was positively

  12. Sensitivity of detrended fluctuation analysis applied to heart rate variability of preterm newborns

    E-print Network

    Sensitivity of detrended fluctuation analysis applied to heart rate variability of preterm newborns.vanhuffel@esat.kuleuven.ac.be Abstract­Detrended fluctuation analysis (DFA), a fractal analysis method which is widely used in heart rate. It is shown that the scaling behaviour is not constant over such long segments and how heart rate patterns

  13. Emergence of dynamical complexity related to human heart rate variability

    NASA Astrophysics Data System (ADS)

    Chang, Mei-Chu; Peng, C.-K.; Stanley, H. Eugene

    2014-12-01

    We apply the refined composite multiscale entropy (MSE) method to a one-dimensional directed small-world network composed of nodes whose states are binary and whose dynamics obey the majority rule. We find that the resulting fluctuating signal becomes dynamically complex. This dynamical complexity is caused (i) by the presence of both short-range connections and long-range shortcuts and (ii) by how well the system can adapt to the noisy environment. By tuning the adaptability of the environment and the long-range shortcuts we can increase or decrease the dynamical complexity, thereby modeling trends found in the MSE of a healthy human heart rate in different physiological states. When the shortcut and adaptability values increase, the complexity in the system dynamics becomes uncorrelated.

  14. 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,...

  15. Variable-rate Phosphorus Fertilization: On-farm Research Methods and Evaluation for Corn and Soybean

    Microsoft Academic Search

    A. P. Mallarino; D. J. Wittry; D. Dousa; P. N. Hinz

    This study adapted precision agriculture technologies to commonly used field-scale strip trials and compared fixed and variable phosphorus (P) fertilization for corn (Zea mays L.) and soybean (Glycine max (L.) Merr.). Differential global positioning receivers, yield monitors, and grid soil sampling were used. Variable- rate fertilization reduced considerably the total amount of P fertilizer applied in two of four fields

  16. Ieart Rate Variability of Recently Concussed Athletes at Rest and Exercise

    Microsoft Academic Search

    BRENT GALL; WADE PARKHOUSE; DAVID GOODMAN

    GALL,B., W. PARKHOUSE, and D. GOODMAN. Heart Rate Variability of Recently Concussed Athletes at Rest and Exercise. Med. Sci. Sports Exerc., Vol. 36, No. 8, pp. 1269-1274, 2004. Purpose: The objective of this study was to assess the neuroautonomic cardiovascular regulation in recently concussed athletes at rest and in response to low-moderate steady-state exercise, using heart rate variability (HRV). Methods:

  17. Heart Rate Variability and Particulate Exposure in Vehicle Maintenance Workers: A Pilot Study

    Microsoft Academic Search

    Robert M. Eninger; Frank S. Rosenthal

    2004-01-01

    The association between occupational exposure to PM2.5 and heart rate variability was investigated in a repeated measures, longitudinal study of vehicle maintenance workers occupationally exposed to automobile emissions. Five subjects were monitored for occupational exposure to fine particulate matter (PM2.5) on 6 workdays using an aerosol photometer, validated with side-by-side sampling with a gravimetric method. End-of-day heart rate variability statistics

  18. Avalanche Photo-Detection for High Data Rate Applications

    E-print Network

    H. B. Coldenstrodt-Ronge; C. Silberhorn

    2007-09-19

    Avalanche photo detection is commonly used in applications which require single photon sensitivity. We examine the limits of using avalanche photo diodes (APD) for characterising photon statistics at high data rates. To identify the regime of linear APD operation we employ a ps-pulsed diode laser with variable repetition rates between 0.5MHz and 80MHz. We modify the mean optical power of the coherent pulses by applying different levels of well-calibrated attenuation. The linearity at high repetition rates is limited by the APD dead time and a non-linear response arises at higher photon-numbers due to multiphoton events. Assuming Poissonian input light statistics we ascertain the effective mean photon-number of the incident light with high accuracy. Time multiplexed detectors (TMD) allow to accomplish photon- number resolution by photon chopping. This detection setup extends the linear response function to higher photon-numbers and statistical methods may be used to compensate for non-linearity. We investigated this effect, compare it to the single APD case and show the validity of the convolution treatment in the TMD data analysis.

  19. Avalanche Photo-Detection for High Data Rate Applications

    E-print Network

    Coldenstrodt-Ronge, H B

    2007-01-01

    Avalanche photo detection is commonly used in applications which require single photon sensitivity. We examine the limits of using avalanche photo diodes (APD) for characterising photon statistics at high data rates. To identify the regime of linear APD operation we employ a ps-pulsed diode laser with variable repetition rates between 0.5MHz and 80MHz. We modify the mean optical power of the coherent pulses by applying different levels of well-calibrated attenuation. The linearity at high repetition rates is limited by the APD dead time and a non-linear response arises at higher photon-numbers due to multiphoton events. Assuming Poissonian input light statistics we ascertain the effective mean photon-number of the incident light with high accuracy. Time multiplexed detectors (TMD) allow to accomplish photon- number resolution by photon chopping. This detection setup extends the linear response function to higher photon-numbers and statistical methods may be used to compensate for non-linearity. We investigate...

  20. Second-order approximations for variable order fractional derivatives: Algorithms and applications

    NASA Astrophysics Data System (ADS)

    Zhao, Xuan; Sun, Zhi-zhong; Karniadakis, George Em

    2015-07-01

    Fractional calculus allows variable-order of fractional operators, which can be exploited in diverse physical and biological applications where rates of change of the quantity of interest may depend on space and/or time. In this paper, we derive two second-order approximation formulas for the variable-order fractional time derivatives involved in anomalous diffusion and wave propagation. We then present numerical tests that verify the theoretical estimates of convergence rate and also simulations of anomalous sub-diffusion and super-diffusion that demonstrate new localized diffusion rates that depend on the curvature of the variable-order function. Finally, we perform simulations of wave propagation in a truncated domain to demonstrate how erroneous wave reflections at the boundaries can be eliminated by super-diffusion, and also simulations of the Burgers equation that serve as a testbed for studying the loss and recovery of monotonicity using again variable rate diffusion as a function of space and/or time. Taken together, our results demonstrate that variable-order fractional derivatives can be used to model the physics of anomalous transport with spatiotemporal variability but also as new effective numerical tools that can deal with the long-standing issues of outflow boundary conditions and monotonicity of integer-order PDEs.

  1. Turfgrass species response exposed to increasing rates of glyphosate application

    Microsoft Academic Search

    Y. Senem Su; L. Ozturk; I. Cakmak; H. Budak

    2009-01-01

    To investigate the response of nine turfgrass species exposed to increasing rates of glyphosate application, the dry matter production, visual leaf injury symptoms (e.g., chlorosis and necrosis) and the concentrations of shikimate and mineral nutrients were determined in shoots. The rates of foliar glyphosate application were 0%, 5% (1.58mM), and 20% (6.32mM) of the recommended application rate for weed control.

  2. Short-term Heart Rate Turbulence Analysis Versus Variability and Baroreceptor Sensitivity in Patients With Dilated Cardiomyopathy1

    PubMed Central

    Bauernschmitt, Robert; Meyerfeldt, Udo; Schirdewan, Alexander

    2004-01-01

    New methods for the analysis of arrhythmias and their hemodynamic consequences have been applied in risk stratification, in particular to patients after myocardial infarction. This study investigates the suitability of short-term heart rate turbulence (HRT) analysis in comparison to heart rate and blood pressure variability as well as baroreceptor sensitivity analyses to characterise the regulatory differences between patients with dilated cardiomyopathy (DCM) and healthy controls. In this study, 30 minutes data of non-invasive continuous blood pressure and ECGs of 37 DCM patients and 167 controls measured under standard resting conditions were analysed. The results show highly significant differences between DCM patients and controls in heart rate and blood pressure variability as well as in baroreceptor sensitivity parameters. Applying a combined heart rate-blood pressure trigger, ventricular premature beats were detected in 24.3% (9) of the DCM patients and 11.3% (19) of the controls. This fact demonstrates the limited applicability of short-term HRT analyses. However, the HRT parameters showed significant differences in this subgroup with ventricular premature beats (turbulence onset: DCM: 1.80±2.72, controls: - 4.34±3.10, p<0.001; turbulence slope: DCM: 6.75±5.50, controls: 21.30±17.72, p=0.021). Considering all (including HRT) parameters in the subgroup with ventricular beats, a discrimination rate between DCM patients and controls of 88.0% was obtained (max. 6 parameters). The corresponding value obtained for the total group was 86.3% (without HRT parameters). Comparable classification rates and high correlations between heart rate turbulence and variability and baroreflex parameters point to a more universal applicability of the latter methods. PMID:16943930

  3. Combination of multispectral remote sensing, variable rate technology and environmental modeling for citrus pest management.

    PubMed

    Du, Qian; Chang, Ni-Bin; Yang, Chenghai; Srilakshmi, Kanth R

    2008-01-01

    The Lower Rio Grande Valley (LRGV) of south Texas is an agriculturally rich area supporting intensive production of vegetables, fruits, grain sorghum, and cotton. Modern agricultural practices involve the combined use of irrigation with the application of large amounts of agrochemicals to maximize crop yields. Intensive agricultural activities in past decades might have caused potential contamination of soil, surface water, and groundwater due to leaching of pesticides in the vadose zone. In an effort to promote precision farming in citrus production, this paper aims at developing an airborne multispectral technique for identifying tree health problems in a citrus grove that can be combined with variable rate technology (VRT) for required pesticide application and environmental modeling for assessment of pollution prevention. An unsupervised linear unmixing method was applied to classify the image for the grove and quantify the symptom severity for appropriate infection control. The PRZM-3 model was used to estimate environmental impacts that contribute to nonpoint source pollution with and without the use of multispectral remote sensing and VRT. Research findings using site-specific environmental assessment clearly indicate that combination of remote sensing and VRT may result in benefit to the environment by reducing the nonpoint source pollution by 92.15%. Overall, this study demonstrates the potential of precision farming for citrus production in the nexus of industrial ecology and agricultural sustainability. PMID:17222960

  4. Burn rate variability requirements for the Space Shuttle Advanced Solid Rocket Motor

    Microsoft Academic Search

    S. S. Schlueter; F. W. Jordan; L. W. Stockham

    1993-01-01

    The Advanced Solid Rocket Motor (ASRM) for the Space Shuttle has exceptionally stringent burn rate requirements. These requirements are indirectly expressed in specifications on thrust versus time trace shape and on thrust imbalance during flight for a pair of motors in a flight set. To translate these specifications into burn rate variability requirements, a series of studies was performed in

  5. Effects of shift work on QTc interval and blood pressure in relation to heart rate variability

    Microsoft Academic Search

    Katsuyuki Murata; Eiji Yano; Hideki Hashimoto; Kanae Karita; Miwako Dakeishi

    2005-01-01

    Objectives: There is evidence that shift work contributes to excess cardiovascular mortality. The purpose of this study was to determine the effects of shift work on heart rate-corrected QT (QTc) and blood pressure in relation to heart rate variability (CVRR). Methods: The study population consisted of 153 male shiftworkers and 87 male day workers who were employed at a copper-smelting

  6. Monitoring of the vegetative background of sleep by means of spectral analysis of heart rate variability

    Microsoft Academic Search

    Udo J. Scholz; Anna M. Bianchi; Sergio Cerutti; Stanislav Kubicki

    1993-01-01

    From the ECG trace of the sleep polygrams the heart rate variability (HRV) is derived by determining the intervals between the R peaks. During sleep, transitions of heart rate can be observed in HRV signal which are relevant to changes in the autonomic regulation. For better insight into the vegetative background of sleep, the spectrum analysis of HRV signal and

  7. Sources of variability in attack rates of Euchaeta elongata Esterly, a carnivorous marine copepod

    Microsoft Academic Search

    J. YEN

    1982-01-01

    An accurate and precise measure of ingestion is important for understanding trophic interactions in the plankton. This paper describes effects on the ingestion rate of the carnivorous marine copepod Euchaeta elongata Esterly of several biotic and abiotic factors operating in the pelagic environment. Sources of variability in the attack rate included, in order of decreasing influence: (1) light, (2) prey

  8. Detrended Fluctuation Analysis of Heart Rate Variability in Normal and Growth-Restricted Fetuses

    Microsoft Academic Search

    Akihiko Kikuchi; Nobuya Unno; Shiro Kozuma; Yuji Taketani

    2008-01-01

    Background: Detrended fluctuation analysis (DFA) has recently been validated as an excellent method by which to analyze heart rate variability and distinguish healthy subjects from patients with various types of the cardiac nervous system dysfunction. Methods: One hundred and nineteen fetal heart rate (FHR) recordings obtained from healthy normal fetuses and 68 recordings obtained from small-for-gestational-age (SGA) fetuses were analyzed

  9. Demographic Variables, Base Rates, and Personality Characteristics Associated With Recidivism in Male Delinquents

    ERIC Educational Resources Information Center

    Roberts, Alan H.; And Others

    1974-01-01

    Demographic variables, base rates, and personality characteristics of male delinquents were explored in three studies. The total population discharged from a treatment-oriented facility was followed. Significantly higher rates of recidivism were found among the younger delinquents, with prior institutional experience, and delinquents who had…

  10. A biomedical entertainment platform design based on musical rhythm characteristics and heart rate variability (HRV)

    Microsoft Academic Search

    Yu-chieh Huang; Shih-hsiang Lin; Ching-yen Chien; Yi-cheng Chen; Lei-chun Chou; Sheng-chieh Huang; Ming-yie Jan

    2008-01-01

    Heart rate variability (HRV) is a measure of variations in the heart rate. Over the last 25 years, HRV analysis has became popular as a non-invasive research and clinical tool for indirectly investigating both cardiac and autonomic nervous system (ANS) function in both health and disease area. How the musical rhythmic characteristics, tempo and complexity, affect the performance of HRV

  11. On diffusion processes with variable drift rates as models for decision making during learning

    Microsoft Academic Search

    P. Eckhoff; P. Holmes; C. Law; P. M. Connolly; J. I. Gold

    2008-01-01

    We investigate Ornstein Uhlenbeck and diffusion processes with variable drift rates as models of evidence accumulation in a visual discrimination task. We derive power-law and exponential drift-rate models and characterize how parameters of these models affect the psychometric function describing performance accuracy as a function of stimulus strength and viewing time. We fit the models to psychophysical data from monkeys

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

    Microsoft Academic Search

    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

    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

  13. Scaling-up crop models for climate variability applications

    Microsoft Academic Search

    J. W. Hansen; J. W. Jones

    2000-01-01

    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

  14. Sensor-based nitrogen applications out-performed producer-chosen rates for corn in on-farm demonstrations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimal nitrogen (N) fertilizer rate for corn can vary substantially within and among fields. Crop reflectance sensors offer the potential to diagnose crop N need and control N application rates at a fine spatial scale. Our objective was to evaluate the performance of sensor-based variable-rate N ap...

  15. 40-Gb/s FSK modulated WDM-PON with variable-rate multicast overlay.

    PubMed

    Xin, Xiangjun; Liu, Bo; Zhang, Lijia; Yu, Jianjun

    2011-06-20

    This paper proposes a novel conjugate-driven frequency shift keying (FSK) modulated wavelength division multiplexing passive network (WDM-PON) with variable-rate multicast services. Optical orthogonal frequency division multiplexing (OFDM) is adopted for multicast overlay services with different rate requirements. A differential detection is used for the demodulation of FSK signal, which can eliminate the crosstalk from the OFDM signal. A total 40-Gb/s FSK point to point (P2P) signal and 6.3-Gb/s OFDM overlay with three kinds of variable-rate multicast services are experimentally demonstrated. A physical-layer adaptive identification is proposed for the variable-rate multicast services. After 25 km single mode fiber (SMF) transmission, the power penalties of FSK P2P signal and OFDM multicast overlay are 1.3 dB and 1.7 dB respectively. PMID:21716492

  16. A comparison of subjective and mathematical estimations of fetal heart rate variability

    PubMed Central

    Wolfberg, Adam J.; Derosier, David J.; Roberts, Trevor; Syed, Zeeshan; Clifford, Gari D.; Acker, David; Plessis, Adre Du

    2014-01-01

    Objectives To develop a computerized algorithm to quantify fetal heart rate (FHR) variability and compare it to perinatologists’ interpretation of FHR variability. Methods FHR variability was calculated using data from 30 women who had a fetal scalp electrode placed for a clinical indication, and compared to the assessment of FHR variability from four perinatologists who interpreted paper tracings of the same data. Inter-rater reliability was calculated and receiver–operator curve analysis was done. Results Correlation between the computer algorithm’s assessment of variability and the perinatologists’ assessment (0.27–0.68) was similar to the inter-rater reliability between perinatologists (0.33–0.72). Conclusions A computer-based algorithm can assess FHR variability as well as expert clinicians. PMID:18240077

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

    ERIC Educational Resources Information Center

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

    2011-01-01

    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…

  18. Heart rate variability and circulating catecholamine concentrations during steady state exercise in healthy volunteers.

    PubMed Central

    Breuer, H W; Skyschally, A; Schulz, R; Martin, C; Wehr, M; Heusch, G

    1993-01-01

    OBJECTIVES--To assess whether exercise induced suppression of heart rate variability in the low frequency domain (0.06-0.15 Hz) is related to the increase in circulating catecholamine concentrations. DESIGN--Randomised crossover trial of three exercise tests characterised by different workloads. Pharmacological simulation of exercise-induced changes in vagal and sympathetic activity. PARTICIPANTS--Six healthy men with a mean age of 31.2 (SD 3.0) years. INTERVENTIONS--Three different workloads of steady state cycling ergometry: control state without cycling, cycling at a target heart rate of 100 beats/min, and cycling at a target heart rate of 150 beats/min. Intravenous infusion of atropine (target heart rate 100 beats/min) followed by the additional infusion of adrenaline and noradrenaline. MAIN OUTCOME MEASURES--Fast Fourier analysis of heart rate variability; blood pressure; and venous plasma concentrations of lactate, adrenaline, and noradrenaline. RESULTS--During the control exercise period there were no changes in the assessed variables compared with the preceding resting period. During exercise at a heart rate of 100 beats/min systolic blood pressure increased and heart rate variability decreased. During exercise at a heart rate of 150 beats/min systolic blood pressure and lactate, adrenaline, and noradrenaline concentrations increased. In addition, low frequency (LF) was lower than during exercise at 100 beats/min, high frequency (HF 0.15-0.80 Hz) resembled that during exercise at 100 beats/min, and diastolic blood pressure was reduced. Infusion of atropine caused no changes in blood pressure or plasma concentrations of lactate, adrenaline, and noradrenaline and decreased heart rate variability. The additional infusion of adrenaline and noradrenaline completely suppressed heart rate variability and increased blood pressure. CONCLUSIONS--The reduction in LF and HF during exercise at a heart rate of 100 beats/min, which is not characterised by increased plasma catecholamine concentrations, and during atropine infusion suggests that heart rate variability in the supine state is largely influenced by vagal activity. The additional reduction in LF during exercise at 150 beats/min and during catecholamine infusion may reflect a negative feedback of circulating catecholamines on the sympathetic control of heart rate. PMID:8038025

  19. The Sensitivity Of Response Rate To The Rate Of Variable-Interval Reinforcement For Pigeons And Rats: A Review

    PubMed Central

    Shull, Richard L

    2005-01-01

    The relation between the rate of a response (B) and the rate of its reinforcement (R) is well known to be approximately hyperbolic: B ?=? kR/(R + Ro), where k represents the maximum response rate, and Ro indicates the rate of reinforcers that will engender a response rate equal to half its maximum value. A review of data reported in 17 published papers revealed that, under variable-interval schedules of reinforcement, Ro was usually lower when pigeons were the subjects than when rats were the subjects. The value of k, in contrast, did not differ consistently between pigeons and rats. Some accounts interpret Ro as the rate of alternative, unscheduled reinforcers in the situation, expressed in units of the scheduled reinforcer. So interpreted, the difference in Ro implies that less alternative reinforcement (relative to the scheduled reinforcement) typically is available to pigeons in their operant conditioning chambers than it is to rats in theirs. Whether or not that interpretation of Ro is valid, the pigeon–rat difference in Ro ensures that for reinforcer rates above about 10 per hour, response rate will be noticeably less sensitive to changes in reinforcer rate (and presumably to changes in other incentive and motivational operations) with pigeons than with rats as subjects, at least with the experimental conditions typically employed. PMID:16156139

  20. Spatial Variability in Biodegradation Rates as Evidenced by Methane Production from an Aquifer

    PubMed Central

    Adrian, Neal R.; Robinson, Joseph A.; Suflita, Joseph M.

    1994-01-01

    Accurate predictions of carbon and energy cycling rates in the environment depend on sampling frequencies and on the spatial variability associated with biological activities. We examined the variability associated with anaerobic biodegradation rates at two sites in an alluvial sand aquifer polluted by municipal landfill leachate. In situ rates of methane production were measured for almost a year, using anaerobic wells installed at two sites. Methane production ranged from 0 to 560 ?mol · m-2 · day-1 at one site (A), while a range of 0 to 120,000 ?mol · m-2 · day-1 was measured at site B. The mean and standard deviations associated with methane production at site A were 17 and 57 ?mol · m-2 · day-1, respectively. The comparable summary statistics for site B were 2,000 and 9,900 ?mol · m-2 · day-1. The coefficients of variation at sites A and B were 340 and 490%, respectively. Despite these differences, the two sites had similar seasonal trends, with the maximal rate of methane production occurring in summer. However, the relative variability associated with the seasonal rates changed very little. Our results suggest that (i) two spatially distinct sites exist in the aquifer, (ii) methanogenesis is a highly variable process, (iii) the coefficient of variation varied little with the rate of methane production, and (iv) in situ anaerobic biodegradation rates are lognormally distributed. PMID:16349410

  1. Probabilistic pipe fracture evaluations for leak-rate-detection applications

    SciTech Connect

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

    1995-04-01

    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.

  2. [Afobazole effect on heart rate variability in rats with different behaviors in the "open field" test].

    PubMed

    Kaverina, N V; Popova, E P; Iarkova, M A; Seredenin, S B

    2009-01-01

    The course of cardiovascular diseases is known to depend upon vegetative nervous system condition. The heart rate variability is the quantitative indicator of vegetative nervous system activity. The emotional stress reaction in rats tested in the "open field" was assessed by measuring the heart rate variability, which allowed the chronotropic cardiac function to be studied in detail and showed which part of the vegetative system (either sympathetic or parasympathetic) prevails in animals with different phenotypes of the emotional stress reaction. In rats demonstrating different behaviors in the "open field" test, changes in the heart rate variability were examined under conditions of the emotional stress response development and the treatment with non-benzodiazepine anxiolytic afobazole. It was established that the sympathetic nervous system tone prevails in stress-resistant rats, whereas in non-resistant animals, the parasympathetic system is predominating. In non-resistant rats exposed to stress, the heart rate variability decreased due to reduced power of very low frequencies, in contrast to stress-resistant animals, which showed increased power of very low frequencies. Afobazole was found to increase the heart rate variability in both animal groups. In non-resistant rats, afobazole also raised the vagus tone. PMID:19334509

  3. The Effect of Spray Application Rate and Airflow Rate on Foliar Deposition in a Hedgerow Vineyard

    Microsoft Academic Search

    Gianfranco Pergher; Rino Gubiani

    1995-01-01

    Two experiments were performed in a hedgerow vineyard, in June (after end of blossom) and July (full vegetation development) to assess the influence of spray application rate and air output on the spray distribution from an axial-fan sprayer. Measurements were performed by fluorometry, using Brilliant Sulpha Flavine as a tracer.Increasing spray application rate and air output both led to higher

  4. An infrared high rate video imager for various space applications

    Microsoft Academic Search

    Hâkan Svedhem; Detlef Koschny

    2010-01-01

    Modern spacecraft with high data transmission capabilities have opened up the possibility to fly video rate imagers in space. Several fields concerned with observations of transient phenomena can benefit significantly from imaging at video frame rate. Some applications are observations and characterization of bolides\\/meteors, sprites, lightning, volcanic eruptions, and impacts on airless bodies. Applications can be found both on low

  5. Optimal Spray Application Rates for Ornamental Nursery Liner Production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spray deposition and coverage at different application rates for nursery liners of different sizes were investigated to determine the optimal spray application rates. Experiments were conducted on two and three-year old red maple liners. A traditional hydraulic sprayer with vertical booms was used t...

  6. Heart Rate Variability and Intensity of Habitual Physical Activity in Middle-Aged Persons

    Microsoft Academic Search

    MARTIN BUCHHEIT; CHANTAL SIMON; ANNE CHARLOUX; GABRIELLE BRANDENBERGER

    2005-01-01

    BUCHHEIT, M., C. SIMON, A. CHARLOUX, S. DOUTRELEAU, F. PIQUARD, and G. BRANDENBERGER. Heart Rate Variability and Intensity of Habitual Physical Activity in Middle-Aged Persons. Med. Sci. Sports Exerc., Vol. 37, No. 9, pp. 1530-1534, 2005. Purpose: In the middle-aged, it has been shown that moderate physical activity is associated with increased global HR variability (HRV) and vagal-related HRV indexes.

  7. Management strategy 3: fixed rate fertilizer applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous chapters outlined management strategies for pond fertilization that take into account specific individual pond nutrient needs. Those methods would most likely be more ecologically efficient than a pre-determined fixed-rate nutrient addition strategy. However, the vast majority of available ...

  8. Ablation of swallowing-induced atrial tachycardia affects heart rate variability: a case report.

    PubMed

    Hojo, Rintaro; Fukamizu, Seiji; Ishikawa, Tae; Hayashi, Takekuni; Komiyama, Kota; Tanabe, Yasuhiro; Tejima, Tamotsu; Kobayashi, Yoichi; Sakurada, Harumizu

    2014-05-01

    A 47-year-old man underwent slow pathway ablation for slow-fast atrioventricular nodal reentrant tachycardia. Following the procedure, he felt palpitations while swallowing, and swallowing-induced atrial tachycardia was diagnosed. Swallowing-induced atrial tachycardia arose from the right atrium-superior vena cava junction and was cured by catheter ablation. After the procedure, the patient's heart rate variability changed significantly, indicating suppression of parasympathetic nerve activity. In this case, swallowing-induced atrial tachycardia was related to the vagal nerve reflex. Analysis of heart rate variability may be helpful in elucidating the mechanism of swallowing-induced atrial tachycardia. PMID:23893269

  9. KS variables in rotating reference frame. Application to cometary dynamics

    NASA Astrophysics Data System (ADS)

    Langner, K.; Breiter, S.

    2015-06-01

    The problem of Keplerian motion in the uniformly rotating reference frame has been solved in terms of the Kustaanheimo-Stiefel (KS) variables using canonical formalism. No recourse to the Cartesian variables or orbital elements has been required. The form of solution is well suited for the application as a part of symplectic integrator. The results show that the motion is actually the composition of four independent harmonic oscillations and of the rotation in two specific coordinate planes and their conjugate momenta planes. As an example of application, we use the KS symplectic integrator to study the motion of comet C/1997 J2 (Meunier-Dupuoy) under the action of Galactic tides. The comet is found to follow an orbit in commensurability with the Sun motion around the Galactic centre, but the perturbations are not qualified as a resonance.

  10. Continuously variable transmission: Assessment of applicability to advance electric vehicles

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  11. Cepheid Variables and their Application to the Cosmological Distance Scale

    E-print Network

    Hoffmann, Samantha L

    2013-05-02

    of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Lucas M. Macri Committee Members, Alexey Belyanin Nicholas B. Suntze Sherry J. Yennello Department Head, George R. Welch May 2013 Major Subject: Physics Copyright 2013 Samantha Leigh Ho mann...CEPHEID VARIABLES AND THEIR APPLICATION TO THE COSMOLOGICAL DISTANCE SCALE A Dissertation by SAMANTHA LEIGH HOFFMANN Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree...

  12. Independence of response force and reinforcement rate on concurrent variable-interval schedule performance

    PubMed Central

    Hunter, Ian; Davison, Michael

    1982-01-01

    Five pigeons were trained over 43 experimental conditions on a variety of concurrent variable-interval schedules on which the forces required on the response keys were varied. The results were well described by the generalized matching law with log reinforcement ratios and log force ratios exerting independent (noninteractive) effects on preference. A further analysis using the Akaike criterion, an information-theoretic measure of the efficiency of a model, showed that overall reinforcement rate and overall force requirement did not affect preference. Unlike reinforcement rate changes, force requirement increases did not change the response rate on the alternate key, and an extension of Herrnstein's absolute response rate function for force variation on a single variable-interval schedule is suggested. PMID:16812264

  13. Silicon detector for high rate EXAFS applications

    SciTech Connect

    Kraner, H.W.; Siddons, D.P.; Furenlid, L.R. [Brookhaven National Lab., Upton, NY (United States); Bertuccio, G. [Politecnico di Milano (Italy). Dipt. di Elettronica e Informazione

    1995-08-01

    A multichannel silicon pad detector for EXAFS (Extended X-ray Absorption Fine Structure) applications has been designed and built. The X-ray spectroscopic measurements demonstrate that an adequate energy resolution of 230 eV FWHM (corresponding to 27 rms electrons in silicon) can be achieved reliably at {minus}35 C. A resolution of 190 eV FWHM (corresponding to 22 rms electrons) has been obtained from individual pads at {minus}35 C. At room temperature (25 C) an average energy resolution of 380 eV FWHM is achieved and a resolution of 350 eV FWHM (41 rms electrons) is the best performance. A simple cooling system constituted of Peltier cells is sufficient to reduce the reverse currents of the pads and their related shot noise contribution, in order to achieve resolutions better than 300 eV FWHM which is adequate for the EXAFS applications.

  14. Real-time monitoring of spontaneous resonance in heart rate variability

    Microsoft Academic Search

    Emil Jovanov

    2008-01-01

    The resonant characteristic of heart rate variability is usually generated using biofeedback and the external pacing of breathing, which is typically around 6 breaths\\/min (0.1 Hz), although the exact frequency varies between individuals. It was hypothesized that the actual resonant characteristic of heart rate actually depends on the current psychophysiological state of the subject; therefore, the real-team evaluation of this

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

    PubMed

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

    2001-01-01

    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

  16. Human drivers of variability in the atmospheric CO2 growth rate

    NASA Astrophysics Data System (ADS)

    Krol, M. C.; Randerson, J. T.; Davis, S. J.; Mu, M.; Keppel-Aleks, G.; Morton, D. C.; van der Werf, G.; DeFries, R. S.

    2014-12-01

    Humans directly or indirectly influence atmospheric carbon dioxide variability on multiple time scales. While fossil fuel combustion and land use emissions are known to be the primary agents driving the long-term secular increase in atmospheric CO2, variability on interannual time scales has been attributed primarily to canopy-scale responses of terrestrial ecosystems to temperature and drought stress. Recent work by Wang et al. (2014) identifies a 2-fold increase in the sensitivity of the CO2 growth rate to interannual variations in temperature and attributes this trend to changing interactions between temperature and soil moisture. Here we provide an independent assessment of this trend using a different filtering approach, and describe several novel mechanisms by which humans have exerted direct control on changes in the CO2 growth rate variability over the past 50 years. These mechanisms include: 1) increasing use of fire by humans in dry and wet tropical forests, where fire behavior and fire spread is sensitive to El Nino-Southern Oscillation (ENSO) and other climate modes, 2) modifications to ecosystems that increase their vulnerability to fire and drought stress, 3) land use responses to economic growth cycles, and 4) covariance between atmospheric transport variability and increasing regional (and interhemispheric) gradients of fossil fuel CO2. We conclude by reviewing how human and climate controls on CO2 growth rate variability are likely to change in future decades for different climate change scenarios.

  17. Heart Rate Variability – a Tool to Differentiate Positive and Negative Affective States in Pigs?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The causal neurophysiological processes, such as autonomic nervous system activity, that mediate behavioral and physiological reactivity to an environment have largely been ignored. Heart rate variability (HRV) analysis is a clinical diagnostic tool used to assess affective states (stressful and ple...

  18. Use of heart rate variability differentiates between physical and psychological states

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The major goal of animal welfare scientists is to determine when animals are experiencing a state of good welfare or poor welfare. The goal of this research was to determine if measures of heart rate variability can be used to differentiate whether animals are experiencing differing states of physi...

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

    E-print Network

    Pikovsky, Arkady

    In vivo cardiac phase response curve elucidates human respiratory heart rate variability Published information for successful reconstruction of the dynamics is the sensitivity of an oscillator to external-running conditions. We use this method to obtain the phase coupling functions describing cardio-respiratory

  20. Continuous positive airway pressure increases heart rate variability in heart failure patients with obstructive sleep apnoea

    Microsoft Academic Search

    Kengo Usui; Yasuyuki Kaneko

    2008-01-01

    Patients with heart failure or OSA (obstructive sleep apnoea) have reduced HF-HRV (high- frequency heart rate variability), indicating reduced cardiac vagal modulation, a marker of poor prognosis. CPAP (continuous positive airway pressure) abolishes OSA in patients with heart failure, but effects on daytime HF-HRV have not been determined. We hypothesized that, in patients with heart failure, treatment of coexisting OSA

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

    E-print Network

    O'Toole, Alice J.

    Brain Areas Controlling Heart Rate Variability in Tinnitus and Tinnitus-Related Distress Sven Vanneste1,2 *, Dirk De Ridder1 1 Brai2 n, Tinnitus Research Initiative Clinic Antwerp & Department, Faculty of Medicine, University of Antwerp, Antwerp, Belgium Abstract Background: Tinnitus is defined

  2. Evaluation of a laser scanning sensor for variable-rate tree sprayer development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate canopy measurement capabilities are prerequisites to automate variable-rate sprayers. A 270° radial range laser scanning sensor was tested for its scanning accuracy to detect tree canopy profiles. Signals from the laser sensor and a ground speed sensor were processed with an embedded comput...

  3. Nonlinear analysis of heart rate variability within independent frequency components during the sleep–wake cycle

    Microsoft Academic Search

    Daniel E. Vigo; Javier Dominguez; Salvador M. Guinjoan; Mariano Scaramal; Eduardo Ruffa; Juan Solernó; Leonardo Nicola Siri; Daniel P. Cardinali

    2010-01-01

    Heart rate variability (HRV) is a complex signal that results from the contribution of different sources of oscillation related to the autonomic nervous system activity. Although linear analysis of HRV has been applied to sleep studies, the nonlinear dynamics of HRV underlying frequency components during sleep is less known. We conducted a study to evaluate nonlinear HRV within independent frequency

  4. Variable bit-rate coding of video signals for ATM networks

    Microsoft Academic Search

    FUMIO KISHINO; KATSUTOSHI MANABE; YASUHITO HAYASHI; HIROSHI YASUDA

    1989-01-01

    Statistical characteristics of video signals for video packet coding, are clarified and a variable-bit-rate coding method for asynchronous transfer mode (ATM) networks is described that is capable of compensating for packet loss. ATM capabilities are shown to be greatly affected by delay, delay jitter, and packet loss probability. Packet loss has the greatest influence on picture quality. Packets may be

  5. A variable bit rate video codec for asynchronous transfer mode networks

    Microsoft Academic Search

    WILLEM VERBIEST; L. Pinnoo

    1989-01-01

    The bandwidth flexibility offered by the asynchronous transfer mode (ATM) technique makes it possible to select picture quality and bandwidth over a wide range in a simple and straightforward manner. A prototype model of a video codec was developed that demonstrates the feasibility of both variable bit rate (VBR) coding and user-selectable picture quality. The VBR coding algorithm is discussed

  6. Evaluation of Ultrasonic Sensors for the Variable Rate Tree Liner Sprayer Development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sensors functioning reliably under harsh field conditions are needed for the development of variable-rate sprayers to apply pest control agents for tree liners in ornamental nurseries. Two ultrasonic sensors were tested to determine how their durability and detection stability would be influenced by...

  7. Spray droplet sizes with additives discharged from an air-assisted variable-rate nozzle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding droplet size distributions is essential to achieve constant spray quality for real-time variable-rate sprayers that synchronize spray outputs with canopy structures. Droplet sizes were measured for a custom-designed, air-assisted, five-port nozzle coupled with a pulse width modulated (...

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

    ERIC Educational Resources Information Center

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

    2014-01-01

    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…

  9. Changes in the Hurst Exponent of Heart Rate Variability during Physical Activity

    Microsoft Academic Search

    Naoko Aoyagi; Ken Kiyono; Zbigniew R. Struzik; Yoshiharu Yamamoto

    2005-01-01

    We examine fractal scaling properties of heart rate variability using detrended fluctuation analysis (DFA), during physical activity in healthy subjects. We analyze 11 records of healthy subjects, which include both usual daily activity and experimental exercise. The subjects were asked to ride on a bicycle ergometer for 2.5 hours, and maintained a heartbeat interval of 500-600 ms. In order to

  10. Variable Rate Phosphorus Fertilization in Cotton on the Texas High Plains

    E-print Network

    Mukhtar, Saqib

    Variable Rate Phosphorus Fertilization in Cotton on the Texas High Plains Kevin Bronson, Wayne to phosphorus fertilizer, even with soil tests. Phosphorus is probably the third limiting factor in crop growth cotton responds to phosphorus fertilizer, using a landscape (topography) scale. Differences in nitrogen

  11. Noninvasive Assessment of Spontaneous Baroreflex Sensitivity and Heart Rate Variability in Patients with Carotid Stenosis

    Microsoft Academic Search

    A. C. Chao; C. M. Chern; T. B. Kuo; C. H. Chou; Y. M. Chuang; W. J. Wong; H. H. Hu

    2003-01-01

    Background: Previous limited observations have suggested that atherosclerosis may affect the distensibility of the carotid sinus and then impair the baroreflex sensitivity (BRS). No studies have been done to compare the BRS and heart rate variability (HRV) in patients with carotid stenosis and normal controls. Methods: A convenience-consecutive sample of 118 patients with transient ischemic attack or minor stroke 3

  12. Fetal heart rate variability and complexity in the course of pregnancy

    Microsoft Academic Search

    Peter Van Leeuwen; Silke Lange; Henrik Bettermann; Dietrich Grönemeyer; Wolfgang Hatzmann

    1999-01-01

    Aim of this study was the examination of fetal heart rate variability and complexity measures during pregnancy using fetal magnetocardiography. We registered 80 fetal magnetocardiograms in 19 healthy fetuses between the 16th and 41st week of gestation. On the basis of beat to beat intervals, mean RR interval (mRR), its standard deviation (SD), root mean square of successive differences (RMSSD),

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

    ERIC Educational Resources Information Center

    Srinivasan, Krishnamachari

    2007-01-01

    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…

  14. 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 ...

  15. Hierarchical Structure in Healthy and Diseased Heart Rate Variability in Humans

    E-print Network

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

    2003-12-12

    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.

  16. Heart Rate Variability and Sympathetic Skin Response in Male Patients Suffering From Acute Alcohol Withdrawal Syndrome

    Microsoft Academic Search

    Karl-Jurgen Bar; Michael Karl Boettger; Rene Neubauer; Marei Groteluschen; Thomas Jochum; Vico Baier; Heinrich Sauer; Andreas Voss

    2006-01-01

    Background: Many symptoms of alcohol withdrawal (AW) such as tachycardia or elevated blood pressure might be explained by increased peripheral and central adrenergic activity. In contrast to many neurochemical studies of sympathetic activation during AW, only very few studies investigated autonomic balance using neurophysiological methods. Methods: We investigated heart rate variability (HRV) and sympathetic skin response (SSR) in male patients

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

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

    ERIC Educational Resources Information Center

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

    2012-01-01

    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…

  19. Development of a Matlab Software for Analysis of Heart Rate Variability

    E-print Network

    Carvalho, João Luiz

    algorithms. Matlab is also a powerful system for plotting graphs and its open source nature allows one signal. There are software packages which implement some of the algorithms presented in ECGLabDevelopment of a Matlab Software for Analysis of Heart Rate Variability João Luiz Azevedo de

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

    ERIC Educational Resources Information Center

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

    2012-01-01

    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,…

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

    ERIC Educational Resources Information Center

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

    2007-01-01

    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…

  2. Relation between heart rate variability and training load in middle-distance runners

    Microsoft Academic Search

    Vincent PICHOT; Jean-Michel GASPOZ; Franck ENJOLRAS; Anestis ANTONIADIS; Pascal MININI; Thierry BUSSO

    2000-01-01

    V. PICHOT, F. ROCHE, J. M. GASPOZ, F. ENJOLRAS, A. ANTONIADIS, P. MININI, F. COSTES, T. BUSSO, J. R. LACOUR, and J. C. BARTHELEMY. Relation between heart rate variability and training load in middle-distance runners. Med. Sci. Sports Exerc., Vol. 32, No. 10, pp. 1729-1736, 2000. Purpose: Monitoring physical performance is of major importance in competitive sports. Indices commonly used,

  3. Variability in Observed and Sensor Based Estimated Optimum N Rates in Corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent research showed that active sensors such as Crop Circle can be used to estimate in-season N requirements for corn. The objective of this research was to identify sources of variability in the observed and Crop Circle-estimated optimum N rates. Field experiments were conducted at two locations...

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

    PubMed Central

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

    2014-01-01

    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

  5. 19 CFR 152.12 - Applicable rates of duty.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...which provides in general that the rates of duty applicable to merchandise shall be those in effect on the date of entry or withdrawal for consumption, except for certain merchandise covered by an entry for immediate transportation or...

  6. 19 CFR 152.12 - Applicable rates of duty.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...which provides in general that the rates of duty applicable to merchandise shall be those in effect on the date of entry or withdrawal for consumption, except for certain merchandise covered by an entry for immediate transportation or...

  7. 19 CFR 152.12 - Applicable rates of duty.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...which provides in general that the rates of duty applicable to merchandise shall be those in effect on the date of entry or withdrawal for consumption, except for certain merchandise covered by an entry for immediate transportation or...

  8. 19 CFR 152.12 - Applicable rates of duty.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...which provides in general that the rates of duty applicable to merchandise shall be those in effect on the date of entry or withdrawal for consumption, except for certain merchandise covered by an entry for immediate transportation or...

  9. 19 CFR 152.12 - Applicable rates of duty.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...which provides in general that the rates of duty applicable to merchandise shall be those in effect on the date of entry or withdrawal for consumption, except for certain merchandise covered by an entry for immediate transportation or...

  10. 26 CFR 26.2641-1 - Applicable rate of tax.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...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...

  11. Periodic spectral components of fetal heart rate variability reflect the changes in cord arterial base deficit values: a preliminary report

    Microsoft Academic Search

    Tiina Rantonen; Eeva Ekholm; Saila Siira; Taina Metsälä; Riitta Leino; Ulla Ekblad; Ilkka Välimäki

    2001-01-01

    Fetal distress changes the function of the autonomic nervous system. These changes are reflected in the fetal heart rate and can be quantified with power spectrum analysis of heart rate variability. The purpose of this study was to find out whether spectral components of fetal heart rate variability (FHRV) during labor are associated with fetal cord arterial base deficit values

  12. Sensor-based nitrogen applications out-performed producer-chosen rates for corn in on-farm demonstrations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimal nitrogen (N) fertilizer rate for corn (Zea mays L.) and other crops can vary substantially within and among fields. Current N management practices do not address this variability. Crop reflectance sensors offer the potential to diagnose crop N need and control N application rates at a fine s...

  13. A conceptual evaluation of sustainable variable-rate agricultural residue removal.

    PubMed

    Muth, D; Bryden, K M

    2012-01-01

    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, 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, 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. PMID:23128737

  14. A Conceptual Evaluation of Sustainable Variable-Rate Agricultural Residue Removal

    SciTech Connect

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

    2012-10-01

    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.

  15. Translational applications of evaluating physiologic variability in human endotoxemia

    PubMed Central

    Scheff, Jeremy D.; Mavroudis, Panteleimon D.; Calvano, Steve E.; Androulakis, Ioannis P.

    2012-01-01

    Dysregulation of the inflammatory response is a critical component of many clinically challenging disorders such as sepsis. Inflammation is a biological process designed to lead to healing and recovery, ultimately restoring homeostasis; however, the failure to fully achieve those beneficial results can leave a patient in a dangerous persistent inflammatory state. One of the primary challenges in developing novel therapies in this area is that inflammation is comprised of a complex network of interacting pathways. Here, we discuss our approaches towards addressing this problem through computational systems biology, with a particular focus on how the presence of biological rhythms and the disruption of these rhythms in inflammation may be applied in a translational context. By leveraging the information content embedded in physiologic variability, ranging in scale from oscillations in autonomic activity driving short-term heart rate variability (HRV) to circadian rhythms in immunomodulatory hormones, there is significant potential to gain insight into the underlying physiology. PMID:23203205

  16. A New Method for Quantifying Compaction Rates and Their Spatial Variability in the Mississippi Delta

    NASA Astrophysics Data System (ADS)

    Chamberlain, E. L.; Shen, Z.; Tornqvist, T. E.; Mauz, B.

    2014-12-01

    Understanding the rates and drivers of subsidence in deltas is essential to manage subaerial land in these naturally ephemeral settings. Subsidence in deltaic settings may be driven by deep crustal processes including isostasy and faulting, compaction of Holocene deposits, and anthropogenic activities such as groundwater management and fluid withdrawal. Here, we offer a new method to measure compaction rates and their spatial variability in the Mississippi Delta (MD) to test the null hypotheses that compaction increases seaward and is a major driver of subsidence. Late Holocene compaction rates are measured using the mouthbar-overbank stratigraphic boundary. This boundary generally corresponds to mean low tide level; therefore its present-day height relative to coeval mean low tide level is a measure of compaction since the formation of this boundary. The age of this boundary is established through quartz OSL dating, and Holocene relative sea level history in the MD has been well-established. The common occurrence of the mouthbar-overbank boundary in progradational fluviodeltaic successions in the MD makes it possible to study the spatial variability of compaction rates. We also compare displacement rates for this boundary directly north and south of two coast-parallel normal faults. Results show that late Holocene compaction rates in the Lafourche subdelta of the MD are on the order of a few mm/yr, significantly lower than historical surface subsidence rates for the region. Therefore, the elevated historical surface subsidence rates are likely the result of human alteration of the delta such as fluid withdrawal and groundwater management. Compaction rates do not increase seaward as generally assumed, and instead seem to be driven primarily by the thickness of sediments overlying the mouthbar sands. Thus, the highest rates are documented relatively inland. In addition, we do not find a significant increase in subsidence across normal faults in our study area, suggesting that the contribution of faulting to subsidence has been minimal over the past millennium.

  17. Design of rate control for wireless video telephony applications

    NASA Astrophysics Data System (ADS)

    Chen, Zhifeng; Reznik, Yuriy A.

    2012-10-01

    We propose a design of a rate control algorithm for low-delay video transmission over wireless channels. Our objective is to meet delay constraints and to make sure that the decoder buffer does not overflow or underflow. We approach this problem analytically, by studying the leaky bucket model in the variable rate transmission scenario, and deriving sufficient conditions for meeting our objective. We then employ these conditions in the design of the rate control algorithm. We report results obtained by using this algorithm with an MPEG-4 AVC/H.264 encoder and LTE channel simulator as a test platform.

  18. Estimating digestion rate and the problem of individual variability, exemplified by a scyphozoan jellyfish.

    PubMed

    Båmstedt; Martinussen

    2000-08-23

    Short-term (h) and long-term (days) individual variability and the effects of momentary change in feeding intensity on digestion time were studied in the scyphomedusa Aurelia aurita as a basis for developing a method to experimentally measure the digestion rate with a high precision. Ten individual medusae showed only small, non-significant differences in average digestion time (range, 2.1-2.5 h at 10 degrees C) over a 9-day experiment, whereas variability within and between days and between individuals at a given occasion was high. When medusae were manually kept at a constant feeding intensity, stomach fullness showed high variability both between individuals and within an individual over time. With a feeding intensity of, respectively, 1, 2, 4 and 8 prey h(-1) over a 5-h experimental period, stomach fullness of most individuals corresponded to a theoretical digestion time of 1-3 h, whereas single meals of the same size usually gave somewhat higher digestion time. Medusae subject to a switching from a low to a high feeding intensity tended to increase the variability, but most individuals showed a digestion time of 1-3 h. An opposite switching tended to increase the digestion time and its variability. It is concluded that the digestion time of A. aurita is randomly variable over time within given limits for a given food and environmental condition. This variability is non-synchronised in the population, causing high variability between individuals, and changes in the feeding intensity cause additional variability. However, the average digestion time of A. aurita in a physically and nutritionally stable environment is robust, and changes in the feeding intensity give predictable effects. The use of field collected data on stomach contents and laboratory determined digestion times is therefore an attractive method to calculate predation rate, but the inherent high variability in digestion time must be taken into consideration when designing the digestion experiments. Based on these findings a simple experimental method to determine the digestion time of aquatic animals is outlined and evaluated. The digestion time is simply given as the ratio between number of prey in stomach and total number of prey eaten, times the incubation time, assuming that the feeding intensity is constant. PMID:10958898

  19. A new approach to detect congestive heart failure using short-term heart rate variability measures.

    PubMed

    Liu, Guanzheng; Wang, Lei; Wang, Qian; Zhou, Guangmin; Wang, Ying; Jiang, Qing

    2014-01-01

    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

  20. Some variables affecting rate of key pecking during response-independent procedures (autoshaping).

    PubMed

    Perkins, C C; Beavers, W O; Hancock, R A; Hemmendinger, P C; Hemmendinger, D; Ricci, J A

    1975-07-01

    Rate of key pecking by pigeons subjected to response-independent procedures in which a stimulus on the response key preceded food presentation was investigated in eight experiments. Color and shape of the stimulus, duration of the stimulus, probability of food following the stimulus, duration of the intertrial interval, and duration of food presentation were varied separately and in combination. All variables studied, except color and shape of the stimulus, had a reliable effect on pecking rate, but some variables had stronger effects than others. Rapid key pecking may be obtained with a variety of response-independent procedures, as well as by response-dependent reinforcement. The results of experiments in which food is both dependent on key pecking and correlated with stimulus conditions are not representative of simple operant effects. Key pecking is an ideal response for studying the simultaneous operation of response-reinforcer and stimulus-reinforcer effects. PMID:16811864

  1. Common multifractality in the heart rate variability and brain activity of healthy humans

    NASA Astrophysics Data System (ADS)

    Lin, D. C.; Sharif, A.

    2010-06-01

    The influence from the central nervous system on the human multifractal heart rate variability (HRV) is examined under the autonomic nervous system perturbation induced by the head-up-tilt body maneuver. We conducted the multifractal factorization analysis to factor out the common multifractal factor in the joint fluctuation of the beat-to-beat heart rate and electroencephalography data. Evidence of a central link in the multifractal HRV was found, where the transition towards increased (decreased) HRV multifractal complexity is associated with a stronger (weaker) multifractal correlation between the central and autonomic nervous systems.

  2. Analysis of long term heart rate variability: methods, 1/f scaling and implications

    NASA Technical Reports Server (NTRS)

    Saul, J. P.; Albrecht, P.; Berger, R. D.; Cohen, R. J.

    1988-01-01

    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.

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

    Microsoft Academic Search

    Narumi Nagai; Taku Hamada; Tetsuya Kimura; Toshio Moritani

    2004-01-01

    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

  4. Heart rate variability during waking and sleep in healthy males and females

    Microsoft Academic Search

    S. Eisenbruck; Michael J. Harnish; William C. Orr; Thomas N. Lynn

    1999-01-01

    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

  5. IDENTIFYING COST-EFFECTIVE SOIL SAMPLING SCHEMES FOR VARIABLE-RATE FERTILIZATIONAND LIMING

    Microsoft Academic Search

    A. P. Mallarino; D. J. Wittry

    Within-field nutrient variability causes some areas of a field to be more or less responsive to fertilization. The best soil sampling and fertilization strategies are those that best estimate and apply economic optimum fertilizer rates across a field. Although current site-specific management practices could achieve this goal, questions remain concerning the cost-effectiveness of alternative sampling strategies. This study compared various

  6. Modeling and Simulation of Self-Similar Variable Bit Rate Compressed Video: A Unified Approach

    Microsoft Academic Search

    Changcheng Huang; Michael Devetsikiotis; Ioannis Lambadaris; A. Roger Kaye

    1995-01-01

    Variable bit rate (VBR) compressed video is expected to become one of the major loading factors in high-speed packet networks such as ATM-based B-ISDN. However, recent measurements based on long empirical traces (complete movies) revealed that VBR video traffic possesses that we had used before only for simple fractal processes. We use importance sampling techniques to efficiently estimate low probabilities

  7. The Superposition of Variable Bit Rate Sources in an ATM Multiplexer

    Microsoft Academic Search

    Ilkka Norros; James W. Roberts; Alain Simonian; Jorma T. Virtamo

    1991-01-01

    When variable-bit-rate sources are multiplexed in an asynchronous transfer mode (ATM) network, there arise queues with a particular form of correlated arrival process. Such queues are analyzed by exploiting a result expressing the distribution of work in system of the G\\/G\\/1 queue originally derived by V.E. Benes (1963). A simple alternative demonstration of this result is analyzed and extended to

  8. Long-range dependence in variable-bit-rate video traffic

    Microsoft Academic Search

    Jan Beran; Robert Sherman; Murad S. Taqqu; Walter Willinger

    1995-01-01

    We analyze 20 large sets of actual variable-bit-rate (VBR) video data, generated by a variety of different codecs and representing a wide range of different scenes. Performing extensive statistical and graphical tests, our main conclusion is that long-range dependence is an inherent feature of VBR video traffic, i.e., a feature that is independent of scene (e.g., video phone, video conference,

  9. Analysis of heart rate variability dynamics during propofol and dexmedetomidine anesthesia

    Microsoft Academic Search

    M. P. Tarvainen; S. Georgiadis; J. A. Lipponen; T. Laitio; P. A. Karjalainen; H. Scheinin; K. Kaskinoro

    2010-01-01

    It has been observed that heart rate variability (HRV) diminishes during anesthesia, but the exact mechanisms causing it are not completely understood. The aim of this paper was to study the dynamics of HRV during low dose propofol (N=9) and dexmedetomidine (N=8) anesthesia by using state-of-the-art time-varying methods, and thereby ultimately try to improve the safety of anesthesia. The time-varying

  10. Effect of different vibration frequencies on heart rate variability and driving fatigue in healthy drivers

    Microsoft Academic Search

    Kun Jiao; Zengyong Li; Ming Chen; Chengtao Wang; Shaohua Qi

    2004-01-01

    ObjectiveThis investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV) and driving fatigue in healthy subjects during simulated driving, by the use of power spectrum analysis and subjective evaluation.Materials and methodsSixty healthy subjects (29.6±3.3 years) were randomly divided into three groups, A, B and C, and the subjects of each group participated in the

  11. Short-Term Heart Rate Variability Strongly Predicts Sudden Cardiac Death in Chronic Heart Failure Patients

    Microsoft Academic Search

    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

    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

  12. Pilot study employing heart rate variability biofeedback training to decrease anxiety in patients with eating disorders

    PubMed Central

    2014-01-01

    Heart rate variability (HRV) biofeedback, a technique which encourages slow meditative breathing, was offered to 25 in-patients with various eating disorder diagnoses-anorexia nervosa, bulimia nervosa and binge eating disorder. We found that this modality had no serious side effects, and was subjectively useful to most participants. An enhanced ability to generate highly coherent HRV patterns in patients with recent onset anorexia nervosa was observed. PMID:24917934

  13. Heart rate variability is related to self-reported physical activity in a healthy adolescent population

    Microsoft Academic Search

    Eva Henje Blom; Erik M. G. Olsson; Eva Serlachius; Mats Ericson; Martin Ingvar

    2009-01-01

    This study investigated whether there is a relationship between heart rate variability (HRV) versus lifestyle and risk factors\\u000a for cardiovascular disease in a population of healthy adolescents. HRV is as an index of tonic autonomic activity and in adults\\u000a HRV is related to lifestyle and risk factors for cardiovascular disease, but it is not known if this is the case

  14. Nonlinear characteristics of heart rate variability during unsupervised and steady physical activities

    Microsoft Academic Search

    Hsiao-Lung Chan; Lian-Yu Lin; Ming-An Lin; Shih-Chin Fang; Chun-Hsien Lin

    2007-01-01

    The heart rate (HR) exhibits various behavior patterns in different postures and during physical activities, whereas a conventional long-term analysis of HR variability has the confounding effect whether the subject was physically active or immobilized. A specially designed ambulatory recorder that simultaneously measures the electrocardiogram and body accelerations was used to study the short-term (<=11 beats, alpha1) fractal correlation property

  15. Glutathione S-Transferase Polymorphisms, Passive Smoking, Obesity, and Heart Rate Variability in Nonsmokers

    Microsoft Academic Search

    Nicole M. Probst-Hensch; Medea Imboden; Denise Felber Dietrich; Jean-Claude Barthélemy; Ursula Ackermann-Liebrich; Wolfgang Berger; Jean-Michel Gaspoz; Joel Schwartz

    2008-01-01

    Abstract BACKGROUND: Disturbances,of heart,rate,variability,(HRV) may represent,one pathway,by which second-hand,smoke,(SHS) and air pollutants,affect,cardiovascular,morbidity,and mortality.,The mechanisms,are poorly,understood.,OBJECTIVES: We investigated,the hypothesis,that,oxidative,stress alters,cardiac,autonomic,control.,We studied the association,of polymorphismsin,oxidant-scavenging glutathione,S-transferase,(GST) genes,and their,interactions,with,SHS and obesity,with,HRV.

  16. Heart Rate Variability (HRV) and Posttraumatic Stress Disorder (PTSD): A Pilot Study

    Microsoft Academic Search

    Gabriel TanTam; Tam K. Dao; Lorie Farmer; Roy John Sutherland; Richard Gevirtz

    2011-01-01

    Exposure to combat experiences is associated with increased risk of developing Post Traumatic Stress Disorder. Prolonged exposure\\u000a therapy and cognitive processing therapy have garnered a significant amount of empirical support for PTSD treatment; however,\\u000a they are not universally effective with some patients continuing to struggle with residual PTSD symptoms. Heart rate variability\\u000a (HRV) is a measure of the autonomic nervous

  17. Biofeedback of Heart Rate Variability and Related Physiology: A Critical Review

    Microsoft Academic Search

    Amanda L. WheatKevin; Kevin T. Larkin

    2010-01-01

    Low heart rate variability (HRV) characterizes several medical and psychological diseases. HRV biofeedback is a newly developed\\u000a approach that may have some use for treating the array of disorders in which HRV is relatively low. This review critically\\u000a appraises evidence for the effectiveness of HRV and related biofeedback across 14 studies in improving (1) HRV and baroreflex\\u000a outcomes and (2)

  18. A Pilot Study of the Efficacy of Heart Rate Variability (HRV) Biofeedback in Patients with Fibromyalgia

    Microsoft Academic Search

    Afton L. Hassett; Diane C. Radvanski; Evgeny G. Vaschillo; Bronya Vaschillo; Leonard H. Sigal; Maria Katsamanis Karavidas; Steven Buyske; Paul M. Lehrer

    2007-01-01

    Fibromyalgia (FM) is a non-inflammatory rheumatologic disorder characterized by musculoskeletal pain, fatigue, depression,\\u000a cognitive dysfunction and sleep disturbance. Research suggests that autonomic dysfunction may account for some of the symptomatology\\u000a of FM. An open label trial of biofeedback training was conducted to manipulate suboptimal heart rate variability (HRV), a\\u000a key marker of autonomic dysfunction. Methods: Twelve women ages 18–60 with

  19. Pilot study employing heart rate variability biofeedback training to decrease anxiety in patients with eating disorders.

    PubMed

    Scolnick, Barbara; Mostofsky, David I; Keane, Robert J

    2014-01-01

    Heart rate variability (HRV) biofeedback, a technique which encourages slow meditative breathing, was offered to 25 in-patients with various eating disorder diagnoses-anorexia nervosa, bulimia nervosa and binge eating disorder. We found that this modality had no serious side effects, and was subjectively useful to most participants. An enhanced ability to generate highly coherent HRV patterns in patients with recent onset anorexia nervosa was observed. PMID:24917934

  20. Iterative Detection of Unity-Rate Precoded FFH-MFSK and Irregular Variable-Length Coding

    Microsoft Academic Search

    Sohail Ahmed; Robert G. Maunder; Lie-Liang Yang; Lajos Hanzo

    2009-01-01

    Iterative decoding of an irregular variable-length coding (IrVLC) scheme concatenated with precoded fast frequency-hopping (FFH) M-ary frequency-shift keying (MFSK) is considered. We employ extrinsic information transfer (EXIT) charts to investigate the three-stage concatenation of the FFH-MFSK demodulator, the rate-1 decoder, and the outer IrVLC decoder. The proposed joint source and channel coding scheme is capable of operating at low signal-to-noise

  1. Determinants of Short-Period Heart Rate Variability in the General Population

    Microsoft Academic Search

    B. Kuch; H. W. Hense; R. Sinnreich; J. D. Kark; A. von Eckardstein; D. Sapoznikov; H.-D. Bolte

    2001-01-01

    Decreased heart rate variability (HRV) is associated with a worse prognosis in a variety of diseases and disorders. We evaluated the determinants of short-period HRV in a random sample of 149 middle-aged men and 137 women from the general population. Spectral analysis was used to compute low-frequency (LF), high-frequency (HF) and total-frequency power. HRV showed a strong inverse association with

  2. Reducing Application Runtime Variability on Jaguar XT5

    SciTech Connect

    Oral, H Sarp [ORNL] [ORNL; Wang, Feiyi [ORNL] [ORNL; Dillow, David A [ORNL] [ORNL; Miller, Ross G [ORNL] [ORNL; Shipman, Galen M [ORNL] [ORNL; Maxwell, Don E [ORNL] [ORNL; Becklehimer, Jeffrey L [ORNL] [ORNL; Larkin, Jeffrey M [ORNL] [ORNL; Henseler, David [Cray, Inc.] [Cray, Inc.

    2010-01-01

    Operating system (OS) noise is defined as interference generated by the OS that prevents a compute core from performing ``useful'' work. Compute node kernel daemons, network interfaces, and other OS related services are major sources of such interference. This interference on individual compute cores can vary in duration and frequency, and can cause de-synchronization (jitter) in collective communication tasks and thus results in variable (degraded) overall parallel application performance. This behavior is more observable in large-scale applications using certain types of collective communication primitives, such as MPI\\_Allreduce. This paper presents our effort towards reducing the overall effect of OS noise on our large-scale parallel applications. Our tests were performed on the quad-core Jaguar, the Cray XT5 at the Oak Ridge National Laboratory Leadership Computing Facility (OLCF). At the time of these tests, Jaguar was a 1.4 PFLOPS supercomputer with 149,504 compute cores and 8 cores per node. We aggregated OS noise sources onto a single core for each node. The scientific application was then run on six of the remaining cores in each node. Our results show that we were able to improve the MPI_Allreduce performance by two orders of magnitude. We demonstrated up to a 30% boost in the performance of the Parallel Ocean Program (POP) using this technique.

  3. Timing and Variability of Galactose Metabolic Gene Activation Depend on the Rate of Environmental Change

    PubMed Central

    Ma, Bo; Ott, William; Josi?, Krešimir; Bennett, Matthew R.

    2015-01-01

    Modulation of gene network activity allows cells to respond to changes in environmental conditions. For example, the galactose utilization network in Saccharomyces cerevisiae is activated by the presence of galactose but repressed by glucose. If both sugars are present, the yeast will first metabolize glucose, depleting it from the extracellular environment. Upon depletion of glucose, the genes encoding galactose metabolic proteins will activate. Here, we show that the rate at which glucose levels are depleted determines the timing and variability of galactose gene activation. Paradoxically, we find that Gal1p, an enzyme needed for galactose metabolism, accumulates more quickly if glucose is depleted slowly rather than taken away quickly. Furthermore, the variability of induction times in individual cells depends non-monotonically on the rate of glucose depletion and exhibits a minimum at intermediate depletion rates. Our mathematical modeling suggests that the dynamics of the metabolic transition from glucose to galactose are responsible for the variability in galactose gene activation. These findings demonstrate that environmental dynamics can determine the phenotypic outcome at both the single-cell and population levels. PMID:26200924

  4. Students' Ways of Thinking about Two-Variable Functions and Rate of Change in Space

    ERIC Educational Resources Information Center

    Weber, Eric David

    2012-01-01

    This dissertation describes an investigation of four students' ways of thinking about functions of two variables and rate of change of those two-variable functions. Most secondary, introductory algebra, pre-calculus, and first and second semester calculus courses do not require students to think about functions of more than one variable. Yet…

  5. Influence of Physical Activity on 24Hour Measurements of Heart Rate Variability in Patients With Coronary Artery Disease

    Microsoft Academic Search

    Hans-H Osterhues; Stefan R Hanzel; Matthias Kochs; Vinzenz Hombach

    1997-01-01

    This study assessed the influence of physical activity on time domain variables of heart rate variability (HRV) during 24-hour electrocardiographic registrations. Changes in time domain variables of HRV (in particular SDNN) obtained from Holter recordings were proven as strong predictors of cardiac events in patients with coronary artery disease. Although 24-hour measurements of HRV recordings are a standard technique, little

  6. Effect of energy drink dose on exercise capacity, heart rate recovery and heart rate variability after high-intensity exercise

    PubMed Central

    An, Sang Min; Park, Jong Suk; Kim, Sang Ho

    2014-01-01

    [Purpose] The purpose of this research was to investigate the effects of exercise capacity, heart rate recovery and heart rate variability after high-intensity exercise on caffeine concentration of energy drink. [Methods] The volunteers for this study were 15 male university student. 15 subjects were taken basic physical examinations such as height, weight and BMI before the experiment. Primary tests were examined of VO2max per weight of each subjects by graded exercise test using Bruce protocol. Each of five subject was divided 3 groups (CON, ECG?, ECG?) by matched method based on weight and VO2max per weight what gained of primary test for minimize the differences of exercise capacity and ingestion of each groups. For the secondary tests, the groups of subjects were taken their materials before and after exercise as a blind test. After the ingestion, subjects were experimented on exercise test of VO2max 80% by treadmill until the all-out. Heart rate was measured by 1minute interval, and respiratory variables were analyzed VO2, VE, VT, RR and so on by automatic respiratory analyzer. And exercise exhaustion time was determined by stopwatch. Moreover, HRV was measured after exercise and recovery 3 min. [Results] Among the intake groups, ECG? was showed the longest of exercise exhaustion time more than CON group (p = .05). Result of heart rate during exercise according to intake groups, there was significant differences of each time (p < .001), however, not significant differences of each groups and group verse time (p > .05). Result of RPE during exercise according to intake groups, there was significant differences of each time (p < .001), however, not significant differences of each groups and group verse time (p > .05). [Conclusion] In conclusion, EDG? showed the significant increase of exercise exhaustion time more than CON group (p=.05) and not significant differences in HR, RPE, RER, HRV, HRR, blood pressure (p > .05). Therefore, 2.5 mg/kg-1 ingestion of energy drink might be positive effect to increase exercise performance capacity without side-effect in cardiovascular disease. PMID:25566437

  7. Neural dynamics, bifurcations and firing rates in a quadratic integrate-and-fire model with a recovery variable. I: deterministic

    E-print Network

    Shlizerman, Eli

    of a quadratic integrate-and-fire model of a single compartment neuron with a slow recovery variable, as inputNeural dynamics, bifurcations and firing rates in a quadratic integrate-and-fire model approximations of instantaneous firing rates for fixed values of the recovery variable, and use the averaging

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

    E-print Network

    non-REM sleep period without specific abnormal events is sufficient to define a matureHeart 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

  9. Prognostic value of reduced heart rate variability after myocardial infarction: clinical evaluation of a new analysis method

    Microsoft Academic Search

    T R Cripps; M Malik; T G Farrell; A J Camm

    1991-01-01

    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,

  10. Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France

    USGS Publications Warehouse

    Piegay, H.; Hupp, C.R.; Citterio, A.; Dufour, S.; Moulin, B.; Walling, D.E.

    2008-01-01

    Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides 137Cs and unsupported 210Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a -1 over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and 137Cs approaches are cross validated for estimating the sedimentation rate within a channel infill. Copyright 2008 by the American Geophysical Union.

  11. Evaluation of modulations in heart rate variability caused by a composition of herbal extracts.

    PubMed

    Cysarz, D; Schürholz, T; Bettermann, H; Kümmell, H C

    2000-05-01

    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

  12. Short-term heart rate variability in a population-based sample of 10-year-old children.

    PubMed

    Jarrin, Denise C; McGrath, Jennifer J; Poirier, Paul; Séguin, Louise; Tremblay, Richard E; Montplaisir, Jacques Y; Paradis, Gilles; Séguin, Jean R

    2015-01-01

    Heart rate variability (HRV) is a non-invasive quantitative marker of cardiac autonomic function derived from continuous electrocardiogram (ECG) recordings. Normative HRV values and development factors have not been established in pediatric populations. The objective was to derive referent time- and frequency-domain HRV values for a population-based sample of children. Children aged 9-11 years (N = 1,036) participated in the Québec Longitudinal Study of Child Development cohort cardiovascular health screening. Registered nurses measured anthropometrics (height, weight) and children wore an ambulatory Holter monitor to continuously record an ECG signal. HRV variables included time (SDNN, pNN50, RMSSD, SDANN) and frequency (HF, LF, LF/HF ratio) domain variables. Normative HRV values, stratified by age, sex, and heart rate, are presented. Greater heart rate (? avg  = -0.60, R avg (2)  = 0.39), pubertal maturation (? avg = -0.11, R avg (2)  = 0.01), later ECG recording times (? avg = -0.19, R avg (2)  = 0.07), and higher diastolic blood pressure (? avg = -0.11, R avg (2)  = 0.01) were significantly associated with reduced HRV in 10-year-old children. The normative HRV values permit clinicians to monitor, describe, and establish pediatric nosologies in primary care and research settings, which may improve treatment of diseases associated with HRV in children. By better understanding existing values, the practical applicability of HRV among clinicians will be enhanced. Lastly, developmental (e.g., puberty) and procedural (e.g., recording time) factors were identified that will improve recording procedures and interpretation of results. PMID:25056158

  13. Short-Term Heart Rate Variability in a Population-Based Sample of 10-Year-Old Children

    PubMed Central

    Jarrin, Denise C.; Poirier, Paul; Séguin, Louise; Tremblay, Richard E.; Montplaisir, Jacques Y.; Paradis, Gilles; Séguin, Jean R.

    2014-01-01

    Heart rate variability (HRV) is a non-invasive quantitative marker of cardiac autonomic function derived from continuous electrocardiogram (ECG) recordings. Normative HRV values and development factors have not been established in pediatric populations. The objective was to derive referent time- and frequency-domain HRV values for a population-based sample of children. Children aged 9–11 years (N = 1,036) participated in the Québec Longitudinal Study of Child Development cohort cardiovascular health screening. Registered nurses measured anthropometrics (height, weight) and children wore an ambulatory Holter monitor to continuously record an ECG signal. HRV variables included time (SDNN, pNN50, RMSSD, SDANN) and frequency (HF, LF, LF/HF ratio) domain variables. Normative HRV values, stratified by age, sex, and heart rate, are presented. Greater heart rate (?avg = ?0.60, Ravg2=0.39), pubertal maturation (?avg = ?0.11, Ravg2=0.01), later ECG recording times (?avg = ?0.19, Ravg2=0.07), and higher diastolic blood pressure (?avg = ?0.11, Ravg2=0.01) were significantly associated with reduced HRV in 10-year-old children. The normative HRV values permit clinicians to monitor, describe, and establish pediatric nosologies in primary care and research settings, which may improve treatment of diseases associated with HRV in children. By better understanding existing values, the practical applicability of HRV among clinicians will be enhanced. Lastly, developmental (e.g., puberty) and procedural (e.g., recording time) factors were identified that will improve recording procedures and interpretation of results. PMID:25056158

  14. 78 FR 70633 - Change in Rates and Classes of General Applicability for Competitive Products

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-26

    ...Change in Rates and Classes of General Applicability for Competitive Products; Notice Federal...Change in Rates and Classes of General Applicability for Competitive Products AGENCY: Postal...Notice of a change in rates of general applicability for competitive...

  15. Runoff phosphorus loss immediately after poultry manure application as influenced by the application rate and tillage.

    PubMed

    Kaiser, Daniel E; Mallarino, Antonio P; Haq, Mazhar U; Allen, Brett L

    2009-01-01

    Excessive or N-based application of poultry manure for crops may result in significant risk of P loss with surface runoff. This study assessed P loss immediately after poultry manure application to soybean [Glycine max (L.) Merr.] residue with and without tillage at eight Iowa fields. Manure from chickens (Gallus gallus domesticus) or turkeys (Melleagris gollopavo) was applied at intended rates of 0, 84, or 168 kg total N ha(-1) (total P was 0, 21-63, 50-123 kg P ha(-1), respectively) with three replications. Simulated rainfall (76 mm h(-1)) was applied to 3-m2 sections of larger field plots with 2 to 7% slope, usually within 2 d of application, to collect runoff during 30 min. Runoff was analyzed for concentrations of sediment, dissolved reactive P (DRPC), bioavailable P (BAPC), and total P (TPRC). Non-incorporated manure consistently increased (P < or = 0.10) concentrations of all runoff P fractions in five sites, but there were increasing trends at all sites, and on average manure increased DRPC, BAPC, and TPRC 32, 23, and 12 times, respectively, over the control. Tillage to incorporate manure reduced DRPC, BAPC, and TPRC by 88, 89, and 77% on average, respectively, although in non-manured plots tillage seldom affected DRPC or BAPC and often increased TPRC. Tillage increased sediment concentration in runoff but not enough to offset the benefits of manure P incorporation. Runoff P loads generally followed trends of runoff P concentrations but were more variable, and significant treatment effects were less frequent. Overall, incorporation of manure by tillage was very effective at reducing P loss during runoff events shortly after poultry manure application under the conditions of this study. PMID:19141820

  16. Variable firing rate power burner for high efficiency gas furnaces. Final report

    SciTech Connect

    Fuller, H.H.; Demler, R.L.; Poulin, E.

    1980-02-01

    One method for increasing the efficiency of residential furnaces and boilers is to retrofit a burner capable of firing rate (FR) modulation. While maximum FR is still attainable, the average FR is significantly lower, resulting in more effective heat exchanger performance. Equally important is the capability for continuous firing at a very low rate (simmering) which eliminates off-cycle loss, a heavy contributor to inefficiency. Additional performance can be gained by reducing the excess air required by a burner. Based on its previous experience, Foster-Miller Associates, Inc. has designed and tested a low excess air (about 15%) variable firing rate (VFR) burner. The theory of operation and the construction of the test burner are described. Test results are given along with a conclusion/recommendation. A Phase II plan is outlined which suggests methods and steps for fabrication and field testing of a number of prototype units.

  17. Prognostic value of ventricular arrhythmias and heart rate variability in patients with unstable angina

    PubMed Central

    Lanza, G A; Cianflone, D; Rebuzzi, A G; Angeloni, G; Sestito, A; Ciriello, G; Torre, G La; Crea, F; Maseri, A

    2006-01-01

    Objectives To assess the prognostic value of ventricular arrhythmias (VA) and heart rate variability (HRV) in patients with unstable angina. Design Multicentre prospective study. Setting 17 cardiological centres in Italy. Patients 543 consecutive patients with unstable angina and preserved left ventricular function (ejection fraction ?40%) enrolled in the SPAI (Stratificazione Prognostica dell'Angina Instabile) study. Methods Patients underwent 24?h ECG Holter monitoring within 24?h of hospital admission. Tested variables were frequent ventricular extrasystoles (?10/h), complex (that is, frequent or repetitive) VA, and bottom quartile values of time?domain and frequency?domain HRV variables. Primary end points were in?hospital and six?month total and cardiac deaths. Results Eight patients died in hospital (1.5%) and 32 (5.9%, 29 cardiac) during follow up. Both complex VA and frequent extrasystoles were strongly predictive of death in hospital and at follow up, even after adjustment for clinical (age, sex, cardiac risk factors and history of myocardial infarction) and laboratory (troponin I, C reactive protein and transient myocardial ischaemia on Holter monitoring) variables. At univariate analysis bottom quartile values of three HRV variables (standard deviation of RR intervals index, low?frequency amplitude and low to high frequency ratio) were associated with in?hospital death, and bottom quartile values of most HRV variables predicted six?month fatal events. At multivariate Cox survival analysis reduced low?frequency amplitude was consistently found to be independently associated with fatal end points. Conclusion In patients with unstable angina with preserved myocardial function, both VA and HRV are independent predictors of in?hospital and medium?term mortality, suggesting that these factors should be taken into account in the risk stratification of these patients. PMID:16387812

  18. Microgravity alters respiratory sinus arrhythmia and short-term heart rate variability in humans

    NASA Technical Reports Server (NTRS)

    Migeotte, P-F; Prisk, G. Kim; Paiva, M.; West, J. B. (Principal Investigator)

    2003-01-01

    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).

  19. Periodic spectral components of fetal heart rate variability reflect the changes in cord arterial base deficit values: a preliminary report.

    PubMed

    Rantonen, T; Ekholm, E; Siira, S; Metsälä, T; Leino, R; Ekblad, U; Välimäki, I

    2001-01-01

    Fetal distress changes the function of the autonomic nervous system. These changes are reflected in the fetal heart rate and can be quantified with power spectrum analysis of heart rate variability. The purpose of this study was to find out whether spectral components of fetal heart rate variability (FHRV) during labor are associated with fetal cord arterial base deficit values at birth. The association between FHRV and umbilical cord arterial base deficit was studied in 14 singleton fetuses with normal pregnancy at 35-40 weeks of gestation. Fetal ECG was recorded by scalp-electrode using a STAN Fetal ECG monitor (Cinventa Ab, Mölndal, Sweden). FHRV was quantified by computing Fast-Fourier-transformed heart rate (HR) spectra at three frequency bands: low-frequency (LF) 0.03-0.07 Hz, mid-frequency (MF) 0.07-0.13 Hz and high-frequency (HF) 0.13-1.0 Hz. We found that total FHRV and MF FHRV were lower in fetuses with cord arterial base deficit 8 to 12 mmol/L in comparison to the fetuses with normal cord arterial base deficit value (P=0.02 and P=0.01, respectively). A linear correlation was found between the spectral densities and the cord arterial base deficit values (r=0.4 and r=0.6, respectively). We conclude that the results suggest changes in the autonomic nervous cardiac control in fetuses with cord arterial base deficit between 8 to 12 mmol/L. The clinical applicability of our observations on FHRV in predicting fetal distress remains to be further studied. PMID:11146242

  20. Test-Retest Reliability of Heart Rate Variability and Respiration Rate at Rest and during Light Physical Activity in Normal Subjects

    Microsoft Academic Search

    Alida M. Guijt; Judith K. Sluiter; Monique H. W. Frings-Dresen

    2007-01-01

    Background. A variable that remains stable over repeated measurements (in stable con- ditions) is ideal for tracking modifications of the clinical state. The aim of the present study is to examine test-retest reliability of time-domain heart rate variability and respi- ration rate measurements using a portable device on normal subjects during rest and light physical activity. Methods. Twenty-six normal subjects

  1. Serial heart rate variability testing for the evaluation of autonomic dysfunction after stroke

    PubMed Central

    Al-Qudah, Zaid; Yacoub, Hussam A; Souayah, Nizar

    2014-01-01

    Background and purpose Autonomic dysfunction has been described as a frequent complication of stroke that could involve the cardiac, respiratory, sudomotor, and sexual systems. Cardiac autonomic dysfunction after stroke is one of the most recognized and has been described to increase the rate of mortality and morbidity. Methods We report two cases of stroke—one hemorrhagic and one ischemic—and describe heart rate variability during the patients’ hospitalizations with improvement reported for each patient several days after stroke onset. Results The first case demonstrated autonomic dysfunction with severe reduction of HRV after a right parietal hemorrhagic stroke. The second case demonstrated similar findings in a patient with acute ischemic stroke. In both cases, normalization of heart rate variability occurred several weeks after stroke symptoms onset and was paralleled by a dramatic improvement of the clinical status. Conclusion Our data established that serial HRV testing is a noninvasive tool that could be utilized as a marker to evaluate the dynamics of acute stroke. PMID:25566336

  2. Performance evaluation of low rate WPANs for medical applications

    Microsoft Academic Search

    Nada Golmie; David Cypher; Olivier Rebala

    2004-01-01

    In this article we consider the emerging low-rate wireless personal area network (WPAN) technology as specified in the IEEE 802.15.4 standard and evaluate its suitability for medical applications. The main objective for this effort is to develop a universal and interoperable interface for medical equipment . We focus on scalability issues and the need to support several communicating devices near

  3. UTHSC College of Pharmacy Application for Regional Tuition Rate

    E-print Network

    Cui, Yan

    UTHSC College of Pharmacy Application for Regional Tuition Rate Tuition discount applies) miles radius of Memphis, TN. Eligible students will receive a discount on NonResident tuition #: ________________________________________________ I hereby apply for tuition reduction and certify that I am eligible for this discount as set forth

  4. High-Frequency Heart Rate Variability Linked to Affiliation with a New Group

    PubMed Central

    Sahdra, Baljinder K.; Ciarrochi, Joseph; Parker, Philip D.

    2015-01-01

    This study tests the hypothesis that high levels of high-frequency heart rate variability (HF-HRV) predisposes individuals to affiliate with new groups. Resting cardiac physiological recordings were taken before and after experimental sessions to measure trait high-frequency heart rate variability as an index of dispositional autonomic influence on heart rate. Following an experimental manipulation of priming of caring-related words, participants engaged in a minimal group paradigm, in which they imagined being a member of one of two arbitrary groups, allocated money to members of the two groups, and rated their affiliation with the groups. High levels of HF-HRV were associated with ingroup favouritism while allocating money, an effect largely attributable to a positive relationship between HF-HRV and allocation of money to the ingroup, and less due to a negative relationship between HF-HRV and money allocation to the outgroup. HF-HRV was also associated with increased self-reported affiliation feelings for the ingroup but was unrelated to feelings towards the outgroup. These effects remained substantial even after controlling for age, gender, BMI, mood, caffeine consumption, time of day of data collection, smoking and alcohol behaviour, and respiration rate. Further, the effects were observed regardless of whether participants were primed with caring-related words or not. This study is the first to bridge a long history of research on ingroup favouritism to the relatively recent body of research on cardiac vagal tone by uncovering a positive association between HF-HRV and affiliation with a novel group. PMID:26106891

  5. High-Frequency Heart Rate Variability Linked to Affiliation with a New Group.

    PubMed

    Sahdra, Baljinder K; Ciarrochi, Joseph; Parker, Philip D

    2015-01-01

    This study tests the hypothesis that high levels of high-frequency heart rate variability (HF-HRV) predisposes individuals to affiliate with new groups. Resting cardiac physiological recordings were taken before and after experimental sessions to measure trait high-frequency heart rate variability as an index of dispositional autonomic influence on heart rate. Following an experimental manipulation of priming of caring-related words, participants engaged in a minimal group paradigm, in which they imagined being a member of one of two arbitrary groups, allocated money to members of the two groups, and rated their affiliation with the groups. High levels of HF-HRV were associated with ingroup favouritism while allocating money, an effect largely attributable to a positive relationship between HF-HRV and allocation of money to the ingroup, and less due to a negative relationship between HF-HRV and money allocation to the outgroup. HF-HRV was also associated with increased self-reported affiliation feelings for the ingroup but was unrelated to feelings towards the outgroup. These effects remained substantial even after controlling for age, gender, BMI, mood, caffeine consumption, time of day of data collection, smoking and alcohol behaviour, and respiration rate. Further, the effects were observed regardless of whether participants were primed with caring-related words or not. This study is the first to bridge a long history of research on ingroup favouritism to the relatively recent body of research on cardiac vagal tone by uncovering a positive association between HF-HRV and affiliation with a novel group. PMID:26106891

  6. Ocean variability contributing to basal melt rate near the ice front of Ross Ice Shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    Arzeno, Isabella B.; Beardsley, Robert C.; Limeburner, Richard; Owens, Breck; Padman, Laurie; Springer, Scott R.; Stewart, Craig L.; Williams, Michael J. M.

    2014-07-01

    Basal melting of ice shelves is an important, but poorly understood, cause of Antarctic ice sheet mass loss and freshwater production. We use data from two moorings deployed through Ross Ice Shelf, ˜6 and ˜16 km south of the ice front east of Ross Island, and numerical models to show how the basal melting rate near the ice front depends on sub-ice-shelf ocean variability. The moorings measured water velocity, conductivity, and temperature for ˜2 months starting in late November 2010. About half of the current velocity variance was due to tides, predominantly diurnal components, with the remainder due to subtidal oscillations with periods of a few days. Subtidal variability was dominated by barotropic currents that were large until mid-December and significantly reduced afterward. Subtidal currents were correlated between moorings but uncorrelated with local winds, suggesting the presence of waves or eddies that may be associated with the abrupt change in water column thickness and strong hydrographic gradients at the ice front. Estimated melt rate was ˜1.2 ± 0.5 m a-1 at each site during the deployment period, consistent with measured trends in ice surface elevation from GPS time series. The models predicted similar annual-averaged melt rates with a strong annual cycle related to seasonal provision of warm water to the ice base. These results show that accurately modeling the high spatial and temporal ocean variability close to the ice-shelf front is critical to predicting time-dependent and mean values of meltwater production and ice-shelf thinning.

  7. Autonomic modulations in patients with bronchial asthma based on short-term heart rate variability

    PubMed Central

    Lutfi, Mohamed F.

    2012-01-01

    Background: Although enhanced cholinergic activity of asthmatics has been established early on, little heart rate variability (HRV) studies were done on asthma patients. Previous HRV studies were based on 24-hour recordings and therefore have not considered the extremely labile activity of bronchial asthma. Objective: To evaluate the pattern of autonomic modulations in asthmatic patients based on short-term HRV studies. Materials and Methods: The study involved 100 asthmatic patients with an age range of 20-40 years. Asthma activity was evaluated over the last month prior to patients’ assessment using asthma control test (ACT). Allflow Spirometer was used for assessing pulmonary function, while Biocom 3000 electrocardiography recorder was used for studying 5-minute HRV. Data was analyzed using the Statistical Package for the Social Sciences Software. Heart rate and asthma medications were introduced as a covariate when studied variables were screened for significant correlation between measurements of asthma severity and heart rate variability indices using partial correlations. Results: The level of asthma control correlate positively with both normalized low frequency (LF Norm) and the ratio of low frequency/high frequency (LF/HF) (CC = 0.302, 0.212 and P = 0.002, 0.036, respectively) and negatively with HF Norm (CC = -0.317, P = 0.001). Duration of asthma correlates positively with normalized high frequency (HF Norm) (CC = 0.235, P = 0.020) and negatively with LF Norm (CC = -0.250, P = 0.013). Conclusion: Poor asthma control is associated with lower HRV, depressed sympathetic and enhanced parasympathetic modulations especially in those with longer asthma duration. PMID:22919165

  8. The effect of heart rate variability biofeedback on performance psychology of basketball players.

    PubMed

    Paul, Maman; Garg, Kanupriya

    2012-06-01

    Coping with pressure and anxiety is an ineluctable demand of sports performance. Heart rate variability (HRV) Biofeedback (BFB) shall be used as a tool for self regulating physiological responses resulting in improved psycho physiological interactions. For further analysis, the present study has been designed to examine the relationship between anxiety and performance and also effectiveness of biofeedback protocol to create stress-eliciting situation in basketball players. Thirty basketball players of university level and above (both male and female) aged 18-28 years, who scored a minimum of 20 in state trait anxiety inventory, were randomly divided into three equal groups- Experimental (Biofeedback) group, Placebo group and Control (No Treatment) group. The BFB group received HRV BFB training for 10 consecutive days for 20 min that included breathing at individual's resonant frequency through a pacing stimulus; Placebo group was shown motivational video clips for 10 consecutive days for 10 min, whereas No Treatment Control group was not given any intervention. Two way repeated measure ANOVA was applied to analyze the differences within and between the groups. Anxiety, coping self-efficacy, heart rate variability, respiration rate, and performance (dribbling, passing and shooting) at session 1, 10 and 1 month follow up were statistically significant in each group along with interaction of group and time (p < 0.001). Also, all the measures showed statistically significant inter group difference (p < 0.05). The findings are harmonious with existing data on HRV BFB as a strategy for dealing with anxiety. The Placebo group showed improvement in self efficacy and performance post training. The Control group showed no change in any variable except performance. The results of the study support the idea that HRV BFB lowers the anxiety and thus there seems to be a potential association between HRV BFB and performance optimization. PMID:22402913

  9. Intelligent real-time CCD data processing system based on variable frame rate

    NASA Astrophysics Data System (ADS)

    Chen, Su-ting

    2009-07-01

    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.

  10. Controlling Variable Emittance (MEMS) Coatings for Space Applications

    NASA Technical Reports Server (NTRS)

    Farrar, D.; Schneider, W.; Osiander, R.; Champion, J. L.; Darrin, A. G.; Douglas, Donya; Swanson, Ted D.

    2003-01-01

    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.

  11. Impact of physical activity on heart rate variability in children with type 1 diabetes

    Microsoft Academic Search

    Su-Ru Chen; Yann-Jinn Lee; Hung-Wen Chiu; Chii Jeng

    2008-01-01

    Objective  Children with type 1 diabetes are usually associated with cardiovascular autonomic neuropathy. The present study explored\\u000a the influence of physical activity on their autonomic nervous function by measuring the heart rate variability (HRV).\\u000a \\u000a \\u000a \\u000a Materials and methods  A total of 93 type 1 diabetic children and 107 healthy control subjects were enrolled. The Physical Activity Questionnaire\\u000a for Children (PAQ-C) was adopted to

  12. The effect of tolterodine 4 and 8 mg on the heart rate variability in healthy subjects

    Microsoft Academic Search

    Maya SchiffersPeter Sauermann; Peter Sauermann; Brigitte Schurch; Ulrich Mehnert

    2010-01-01

    Purpose  To investigate the potential effect of tolterodine on the human heart rate variability (HRV). Oral antimuscarinic treatment\\u000a for overactive bladder might significantly alter HRV, which is an important predictor for cardiac and all-cause mortality.\\u000a Yet, little information exists regarding the influence of oral antimuscarinics on the HRV.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Healthy female volunteers were randomly assigned to either placebo, tolterodine extended release (ER)

  13. The influence of age on heart rate variability during morning wakefulness

    Microsoft Academic Search

    Elizabeth Anne Goff; Christian L. Nicholas; Anura S. Malaweera; Anita K. Simonds; John Trinder; Mary J. Morrell

    2010-01-01

    Objective  Early morning wakefulness is associated with a peak in cardiac events. The influence of ageing on cardiac regulation during\\u000a this time is unknown. This cross-sectional study of healthy men and women (n = 40, 20–30 and >60 years) investigated the effect of age on heart rate variability (HRV) during morning versus evening wakefulness\\u000a and sleep.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Stable electrocardiogram data during each wake period and

  14. Highly variable recessive lethal or nearly lethal mutation rates during germ-line development of male Drosophila melanogaster

    PubMed Central

    Gao, Jian-Jun; Pan, Xue-Rong; Hu, Jing; Ma, Li; Wu, Jian-Min; Shao, Ye-Lin; Barton, Sara A.; Woodruff, Ronny C.; Zhang, Ya-Ping; Fu, Yun-Xin

    2011-01-01

    Each cell of higher organism adults is derived from a fertilized egg through a series of divisions, during which mutations can occur. Both the rate and timing of mutations can have profound impacts on both the individual and the population, because mutations that occur at early cell divisions will affect more tissues and are more likely to be transferred to the next generation. Using large-scale multigeneration screening experiments for recessive lethal or nearly lethal mutations of Drosophila melanogaster and recently developed statistical analysis, we show for male D. melanogaster that (i) mutation rates (for recessive lethal or nearly lethal) are highly variable during germ cell development; (ii) first cell cleavage has the highest mutation rate, which drops substantially in the second cleavage or the next few cleavages; (iii) the intermediate stages, after a few cleavages to right before spermatogenesis, have at least an order of magnitude smaller mutation rate; and (iv) spermatogenesis also harbors a fairly high mutation rate. Because germ-line lineage shares some (early) cell divisions with somatic cell lineage, the first conclusion is readily extended to a somatic cell lineage. It is conceivable that the first conclusion is true for most (if not all) higher organisms, whereas the other three conclusions are widely applicable, although the extent may differ from species to species. Therefore, conclusions or analyses that are based on equal mutation rates during development should be taken with caution. Furthermore, the statistical approach developed can be adopted for studying other organisms, including the human germ-line or somatic mutational patterns. PMID:21890796

  15. A variable reaction rate model for chlorine decay in drinking water due to the reaction with dissolved organic matter.

    PubMed

    Hua, Pei; Vasyukova, Ekaterina; Uhl, Wolfgang

    2015-05-15

    A second order kinetic model for simulating chlorine decay in bulk water due to the reaction with dissolved organic matter (DOM) was developed. It takes into account the decreasing reactivity of dissolved organic matter using a variable reaction rate coefficient (VRRC) which decreases with an increasing conversion. The concentration of reducing species is surrogated by the maximum chlorine demand. Temperature dependency, respectively, is described by the Arrhenius-relationship. The accuracy and adequacy of the proposed model to describe chlorine decay in bulk water were evaluated and shown for very different waters and different conditions such as water mixing or rechlorination by applying statistical tests. It is thus very well suited for application in water quality modeling for distribution systems. PMID:25765169

  16. Docosahexaenoic acid-rich fish oil improves heart rate variability and heart rate responses to exercise in overweight adults.

    PubMed

    Ninio, Daniel M; Hill, Alison M; Howe, Peter R; Buckley, Jonathan D; Saint, David A

    2008-11-01

    Dietary fish oil supplementation and regular physical activity can improve outcomes in patients with established CVD. Exercise has been shown to improve heart rate variability (HRV), a predictor of cardiac death, but whether fish oil benefits HRV is controversial. Obese adults at risk of future coronary disease have impaired HRV and may benefit from these interventions. We evaluated the effect of DHA-rich tuna fish oil supplementation with and without regular exercise on HRV in sedentary, overweight adults with risk factors for coronary disease. In a randomised, double-blind, parallel comparison, sixty-five volunteers consumed 6 g fish oil/d (DHA 1.56 g/d, EPA 0.36 g/d) or sunflower-seed oil (placebo) for 12 weeks. Half of each oil group also undertook regular moderate physical activity (3 d/week for 45 min, at 75 % of age-predicted maximal heart rate (HR)). Resting HR and the HR response to submaximal exercise were measured at weeks 0, 6 and 12. In forty-six subjects, HRV was also assessed by power spectrum analysis of 20 min electrocardiogram recordings taken supine at baseline and 12 weeks. Fish oil supplementation improved HRV by increasing high-frequency power, representing parasympathetic activity, compared with placebo (P = 0.01; oil x time interaction). It also reduced HR at rest and during submaximal exercise (P = 0.008; oil x time interaction). There were no significant fish oil x exercise interactions. Dietary supplementation with DHA-rich fish oil reduced HR and modulated HRV in keeping with an improved parasympathetic-sympathetic balance in overweight adults with risk factors for future coronary disease. PMID:18339222

  17. A novel model for antipersistent variable bit rate (VBR) video traffic is proposed. Antipersistent VBR video bit

    E-print Network

    Gabbouj, Moncef

    ABSTRACT A novel model for antipersistent variable bit rate (VBR) video traffic is proposed. Antipersistent VBR video bit streams are a subset of VBR video bit streams in which the bit rate is controlled by a rate controller when the video is encoded. Statistical properties of antipersistent VBR video bit

  18. Heart Rate Variability Biofeedback as a Method for Assessing Baroreflex Function: A Preliminary Study of Resonance in the Cardiovascular System

    Microsoft Academic Search

    Evgeny Vaschillo; Paul Lehrer; Naphtali Rishe; Mikhail Konstantinov

    2002-01-01

    This study describes the use of a biofeedback method for the noninvasive study of baroreflex mechanisms. Five previously untrained healthy male participants learned to control oscillations in heart rate using biofeedback training to modify their heart rate variability at specific frequencies. They were instructed to match computer-generated sinusoidal oscillations with oscillations in heart rate at seven frequencies within the range

  19. Atypical pupillary light reflex and heart rate variability in children with autism spectrum disorder

    PubMed Central

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

    2012-01-01

    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

  20. Considerations in the assessment of heart rate variability in biobehavioral research

    PubMed Central

    Quintana, Daniel S.; Heathers, James A. J.

    2014-01-01

    Heart rate variability (HRV) refers to various methods of assessing the beat-to-beat variation in the heart over time, in order to draw inference on the outflow of the autonomic nervous system. Easy access to measuring HRV has led to a plethora of studies within emotion science and psychology assessing autonomic regulation, but significant caveats exist due to the complicated nature of HRV. Firstly, both breathing and blood pressure regulation have their own relationship to social, emotional, and cognitive experiments – if this is the case are we observing heart rate (HR) changes as a consequence of breathing changes? Secondly, experiments often have poor internal and external controls. In this review we highlight the interrelationships between HR and respiration, as well as presenting recommendations for researchers to use when collecting data for HRV assessment. Namely, we highlight the superior utility of within-subjects designs along with the importance of establishing an appropriate baseline and monitoring respiration. PMID:25101047

  1. A new algorithm for wavelet-based heart rate variability analysis

    E-print Network

    García, Constantino A; Vila, Xosé; Márquez, David G

    2014-01-01

    One of the most promising non-invasive markers of the activity of the autonomic nervous system is Heart Rate Variability (HRV). HRV analysis toolkits often provide spectral analysis techniques using the Fourier transform, which assumes that the heart rate series is stationary. To overcome this issue, the Short Time Fourier Transform is often used (STFT). However, the wavelet transform is thought to be a more suitable tool for analyzing non-stationary signals than the STFT. Given the lack of support for wavelet-based analysis in HRV toolkits, such analysis must be implemented by the researcher. This has made this technique underutilized. This paper presents a new algorithm to perform HRV power spectrum analysis based on the Maximal Overlap Discrete Wavelet Packet Transform (MODWPT). The algorithm calculates the power in any spectral band with a given tolerance for the band's boundaries. The MODWPT decomposition tree is pruned to avoid calculating unnecessary wavelet coefficients, thereby optimizing execution t...

  2. Continuously Variable Rating: a new, simple and logical procedure to evaluate original scientific publications

    PubMed Central

    Silva, Mauricio Rocha e

    2011-01-01

    OBJECTIVE: Impact Factors (IF) are widely used surrogates to evaluate single articles, in spite of known shortcomings imposed by cite distribution skewness. We quantify this asymmetry and propose a simple computer-based procedure for evaluating individual articles. METHOD: (a) Analysis of symmetry. Journals clustered around nine Impact Factor points were selected from the medical “Subject Categories” in Journal Citation Reports 2010. Citable items published in 2008 were retrieved and ranked by granted citations over the Jan/2008 - Jun/2011 period. Frequency distribution of cites, normalized cumulative cites and absolute cites/decile were determined for each journal cluster. (b) Positive Predictive Value. Three arbitrarily established evaluation classes were generated: LOW (1.3?IF<2.6); MID: (2.6?IF<3.9); HIGH: (IF?3.9). Positive Predictive Value for journal clusters within each class range was estimated. (c) Continuously Variable Rating. An alternative evaluation procedure is proposed to allow the rating of individually published articles in comparison to all articles published in the same journal within the same year of publication. The general guiding lines for the construction of a totally dedicated software program are delineated. RESULTS AND CONCLUSIONS: Skewness followed the Pareto Distribution for (1Variable Rating is shown to be a simple computer based procedure capable of accurately providing a valid rating for each article within the journal and time frame in which it was published. PMID:22189736

  3. Applicability and efficacy of variable light in schools.

    PubMed

    Barkmann, Claus; Wessolowski, Nino; Schulte-Markwort, Michael

    2012-02-01

    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

  4. Respiratory and heart rate patterns in infants destined to be victims of sudden infant death syndrome: average rates and their variability measured over 24 hours

    Microsoft Academic Search

    A J Wilson; V Stevens; C I Franks; J Alexander; D P Southall

    1985-01-01

    From a prospective study in which 24 hour recordings of the electrocardiogram and respiratory activity (abdominal wall movement) were made on a population of full term infants, 22 recordings were obtained from 16 infants who later were victims of the sudden infant death syndrome. The average heart rate, average heart rate variability, average breath to breath interval, and average breath

  5. Analysis of heart rate variability and skin blood flow oscillations under deep controlled breathing.

    PubMed

    Krasnikov, Gennady V; Tyurina, Miglena Y; Tankanag, Arina V; Piskunova, Galina M; Chemeris, Nikolai K

    2013-02-01

    The effect of deep breathing controlled in both rate (0.25, 0.16, 0.1, 0.07, 0.05 and 0.03 Hz) and amplitude on the heart rate variability (HRV) and respiration-dependent oscillations of forearm/finger skin blood flow (SBF) has been studied in 29 young healthy volunteers. The influence of sympathovagal balance on the respiratory sinus arrhythmia (RSA) amplitude and respiratory SBF oscillations has been studied. The subjects with predominant parasympathetic tonus had statistically significant higher RSA amplitudes in the breathing rate region of 0.03-0.07 Hz than the subjects with predominant sympathetic tonus. In the finger-cushion zone, having a well-developed sympathetic vascular innervations, the amplitudes of respiratory SBF oscillations at breathing rates 0.05 and 0.07 Hz were higher in the group of subjects with predominant parasympathetic tonus. In the forearm skin, where the density of sympathetic innervations is low comparatively to that in the finger skin, no statistically significant differences in the amplitude of respiratory SBF oscillations were found concerning the two groups of subjects. PMID:23174619

  6. Second ventilatory threshold from heart-rate variability: valid when the upper body is involved?

    PubMed

    Mourot, Laurent; Fabre, Nicolas; Savoldelli, Aldo; Schena, Federico

    2014-07-01

    To determine the most accurate method based on spectral analysis of heart-rate variability (SA-HRV) during an incremental and continuous maximal test involving the upper body, the authors tested 4 different methods to obtain the heart rate (HR) at the second ventilatory threshold (VT(2)). Sixteen ski mountaineers (mean ± SD; age 25 ± 3 y, height 177 ± 8 cm, mass 69 ± 10 kg) performed a roller-ski test on a treadmill. Respiratory variables and HR were continuously recorded, and the 4 SA-HRV methods were compared with the gas-exchange method through Bland and Altman analyses. The best method was the one based on a time-varying spectral analysis with high frequency ranging from 0.15 Hz to a cutoff point relative to the individual's respiratory sinus arrhythmia. The HR values were significantly correlated (r(2) = .903), with a mean HR difference with the respiratory method of 0.1 ± 3.0 beats/min and low limits of agreements (around -6 /+6 beats/min). The 3 other methods led to larger errors and lower agreements (up to 5 beats/min and around -23/+20 beats/min). It is possible to accurately determine VT(2) with an HR monitor during an incremental test involving the upper body if the appropriate HRV method is used. PMID:24231307

  7. Analysis of heart rate variability signal in meditation using second-order difference plot

    NASA Astrophysics Data System (ADS)

    Goswami, Damodar Prasad; Tibarewala, Dewaki Nandan; Bhattacharya, Dilip Kumar

    2011-06-01

    In this article, the heart rate variability signal taken from subjects practising different types of meditations have been investigated to find the underlying similarity among them and how they differ from the non-meditative condition. Four different groups of subjects having different meditation techniques are involved. The data have been obtained from the Physionet and also collected with our own ECG machine. For data analysis, the second order difference plot is applied. Each of the plots obtained from the second order differences form a single cluster which is nearly elliptical in shape except for some outliers. In meditation, the axis of the elliptical cluster rotates anticlockwise from the cluster formed from the premeditation data, although the amount of rotation is not of the same extent in every case. This form study reveals definite and specific changes in the heart rate variability of the subjects during meditation. All the four groups of subjects followed different procedures but surprisingly the resulting physiological effect is the same to some extent. It indicates that there is some commonness among all the meditative techniques in spite of their apparent dissimilarity and it may be hoped that each of them leads to the same result as preached by the masters of meditation. The study shows that meditative state has a completely different physiology and that it can be achieved by any meditation technique we have observed. Possible use of this tool in clinical setting such as in stress management and in the treatment of hypertension is also mentioned.

  8. Heart Rate Variability in Sleeping Preterm Neonates Exposed to Cool and Warm Thermal Conditions

    PubMed Central

    Stéphan-Blanchard, Erwan; Chardon, Karen; Léké, André; Delanaud, Stéphane; Bach, Véronique; Telliez, Frédéric

    2013-01-01

    Sudden infant death syndrome (SIDS) remains the main cause of postneonatal infant death. Thermal stress is a major risk factor and makes infants more vulnerable to SIDS. Although it has been suggested that thermal stress could lead to SIDS by disrupting autonomic functions, clinical and physiopathological data on this hypothesis are scarce. We evaluated the influence of ambient temperature on autonomic nervous activity during sleep in thirty-four preterm neonates (mean ± SD gestational age: 31.4±1.5 weeks, postmenstrual age: 36.2±0.9 weeks). Heart rate variability was assessed as a function of the sleep stage at three different ambient temperatures (thermoneutrality and warm and cool thermal conditions). An elevated ambient temperature was associated with a higher basal heart rate and lower short- and long-term variability in all sleep stages, together with higher sympathetic activity and lower parasympathetic activity. Our study results showed that modification of the ambient temperature led to significant changes in autonomic nervous system control in sleeping preterm neonates. The latter changes are very similar to those observed in infants at risk of SIDS. Our findings may provide greater insight into the thermally-induced disease mechanisms related to SIDS and may help improve prevention strategies. PMID:23840888

  9. The forgotten role of central volume in low frequency oscillations of heart rate variability.

    PubMed

    Ferrario, Manuela; Moissl, Ulrich; Garzotto, Francesco; Cruz, Dinna N; Tetta, Ciro; Signorini, Maria G; Ronco, Claudio; Grassmann, Aileen; Cerutti, Sergio; Guzzetti, Stefano

    2015-01-01

    The hypothesis that central volume plays a key role in the source of low frequency (LF) oscillations of heart rate variability (HRV) was tested in a population of end stage renal disease patients undergoing conventional hemodialysis (HD) treatment, and thus subject to large fluid shifts and sympathetic activation. Fluid overload (FO) in 58 chronic HD patients was assessed by whole body bioimpedance measurements before the midweek HD session. Heart Rate Variability (HRV) was measured using 24-hour Holter electrocardiogram recordings starting before the same HD treatment. Time domain and frequency domain analyses were performed on HRV signals. Patients were retrospectively classified in three groups according to tertiles of FO normalized to the extracellular water (FO/ECW%). These groups were also compared after stratification by diabetes mellitus. Patients with the low to medium hydration status before the treatment (i.e. 1st and 2nd FO/ECW% tertiles) showed a significant increase in LF power during last 30 min of HD compared to dialysis begin, while no significant change in LF power was seen in the third group (i.e. those with high pre-treatment hydration values). In conclusion, several mechanisms can generate LF oscillations in the cardiovascular system, including baroreflex feedback loops and central oscillators. However, the current results emphasize the role played by the central volume in determining the power of LF oscillations. PMID:25793464

  10. Heart rate variability in idiopathic dilated cardiomyopathy: relation to disease severity and prognosis.

    PubMed Central

    Yi, G.; Goldman, J. H.; Keeling, P. J.; Reardon, M.; McKenna, W. J.; Malik, M.

    1997-01-01

    OBJECTIVE: To assess the clinical importance of heart rate variability (HRV) in patients with idiopathic dilated cardiomyopathy (DCM). PATIENTS AND METHODS: Time domain analysis of 24 hour HRV was performed in 64 patients with DCM, 19 of their relatives with left ventricular enlargement (possible early DCM), and 33 healthy control subjects. RESULTS: Measures of HRV were reduced in patients with DCM compared with controls (P < 0.05). HRV parameters were similar in relatives and controls. Measures of HRV were lower in DCM patients in whom progressive heart failure developed (n = 28) than in those who remained clinically stable (n = 36) during a follow up of 24 (20) months (P = 0.0001). Reduced HRV was associated with NYHA functional class, left ventricular end diastolic dimension, reduced left ventricular ejection fraction, and peak exercise oxygen consumption (P < 0.05) in all patients. DCM patients with standard deviation of normal to normal RR intervals calculated over the 24 hour period (SDNN) < 50 ms had a significantly lower survival rate free of progressive heart failure than those with SDNN > 50 ms (P = 0.0002, at 12 months; P = 0.0001, during overall follow up). Stepwise multiple regression analysis showed that SDNN < 50 ms identified, independently of other clinical variables, patients who were at increased risk of developing progressive heart failure (P = 0.0004). CONCLUSIONS: HRV is reduced in patients with DCM and related to disease severity. HRV is clinically useful as an early non-invasive marker of DCM deterioration. PMID:9068391

  11. Spatiotemporal variability of the organic matter and the rates of its transformation in the Ob Inlet

    NASA Astrophysics Data System (ADS)

    Agatova, A. I.; Lapina, N. M.; Torgunova, N. I.

    2013-03-01

    The data on the qualitative and quantitative variability of the organic matter (OM) and its transformation rates in the waters of the Ob Inlet during different seasons are considered. The OM distribution was quite nonuniform over the entire Ob Inlet aquatic area: the concentrations of Corg varied from 2.8 to 14.1 mg/L and from 0.32 to 4.59 mg/L for the dissolved and particulate forms, respectively. The maximum concentrations of dissolved OM were registered in the main flow of the Ob River water supplied to the bay, whereas the minimum concentrations were characteristic for the near-bottom layers formed by the Kara Sea waters of high salinity in the northern part of the bay. Both in the summer and in the autumn, the fraction of particulate matter within the total OM reached its maximum values in the mixing zone of the Taz and Ob riverine waters, as well as in the mixing zone of the Ob River and Kara Sea waters. These boundary zones were characterized by the widest variability of the elemental (C: N: P) and biochemical (proteins and carbohydrates) composition of the OM, as well as of its transformation rates measured by the activities of the enzymes (alkaline phosphatase and the electron transport system).

  12. Short-term heart rate variability in older patients with newly diagnosed depression.

    PubMed

    Ha, Jee Hyun; Park, Soyeon; Yoon, Daehyun; Kim, Byungsu

    2015-04-30

    Dysfunction of the autonomic nervous system has been considered to be a risk factor for major depressive disorder (MDD) and cardiovascular disease (CVD). The aim of this study was to evaluate short-term heart rate variability (HRV) in elderly patients with newly diagnosed MDD. Thirty MDD patients over 60 years old newly diagnosed by a structured interview were enrolled, free from antidepressants. Socio-demographic data, blood tests, and heart rate variability (HRV) obtained from 5-min ECG were gathered. The MDD group showed significantly lower very low frequency power, low frequency power, high frequency power, and total power in frequency domain. In time domain analysis, the MDD group showed a significantly smaller standard deviation of the NN, root mean square of the differences of the successive NN, and NN50/total number of all NNs. These findings demonstrated a lower HRV in older patients who were newly diagnosed with depression without a history of CVD and antidepressants effect, compared with the control subjects. Low HRV may be an important predictor of both MDD and CVD in elderly. The use of HRV in elderly depressive patients could be a meaningful screening method for risk of CVD. PMID:25747680

  13. Variability in venom volume, flow rate and duration in defensive stings of five scorpion species.

    PubMed

    van der Meijden, Arie; Coelho, Pedro; Rasko, Mykola

    2015-06-15

    Scorpions have been shown to control their venom usage in defensive encounters, depending on the perceived threat. Potentially, the venom amount that is injected could be controlled by reducing the flow speed, the flow duration, or both. We here investigated these variables by allowing scorpions to sting into an oil-filled chamber, and recording the accreting venom droplets with high-speed video. The size of the spherical droplets on the video can then be used to calculate their volume. We recorded defensive stings of 20 specimens representing 5 species. Significant differences in the flow rate and total expelled volume were found between species. These differences are likely due to differences in overall size between the species. Large variation in both venom flow speed and duration are described between stinging events of single individuals. Both venom flow rate and flow duration correlate highly with the total expelled volume, indicating that scorpions may control both variables in order to achieve a desired end volume of venom during a sting. PMID:25911958

  14. Statistical variability and confidence intervals for planar dose QA pass rates

    SciTech Connect

    Bailey, Daniel W.; Nelms, Benjamin E.; Attwood, Kristopher; Kumaraswamy, Lalith; Podgorsak, Matthew B. [Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260 (United States) and Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States); Department of Biostatistics, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Molecular and Cellular Biophysics and Biochemistry, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States) and Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214 (United States)

    2011-11-15

    Purpose: The most common metric for comparing measured to calculated dose, such as for pretreatment quality assurance of intensity-modulated photon fields, is a pass rate (%) generated using percent difference (%Diff), distance-to-agreement (DTA), or some combination of the two (e.g., gamma evaluation). For many dosimeters, the grid of analyzed points corresponds to an array with a low areal density of point detectors. In these cases, the pass rates for any given comparison criteria are not absolute but exhibit statistical variability that is a function, in part, on the detector sampling geometry. In this work, the authors analyze the statistics of various methods commonly used to calculate pass rates and propose methods for establishing confidence intervals for pass rates obtained with low-density arrays. Methods: Dose planes were acquired for 25 prostate and 79 head and neck intensity-modulated fields via diode array and electronic portal imaging device (EPID), and matching calculated dose planes were created via a commercial treatment planning system. Pass rates for each dose plane pair (both centered to the beam central axis) were calculated with several common comparison methods: %Diff/DTA composite analysis and gamma evaluation, using absolute dose comparison with both local and global normalization. Specialized software was designed to selectively sample the measured EPID response (very high data density) down to discrete points to simulate low-density measurements. The software was used to realign the simulated detector grid at many simulated positions with respect to the beam central axis, thereby altering the low-density sampled grid. Simulations were repeated with 100 positional iterations using a 1 detector/cm{sup 2} uniform grid, a 2 detector/cm{sup 2} uniform grid, and similar random detector grids. For each simulation, %/DTA composite pass rates were calculated with various %Diff/DTA criteria and for both local and global %Diff normalization techniques. Results: For the prostate and head/neck cases studied, the pass rates obtained with gamma analysis of high density dose planes were 2%-5% higher than respective %/DTA composite analysis on average (ranging as high as 11%), depending on tolerances and normalization. Meanwhile, the pass rates obtained via local normalization were 2%-12% lower than with global maximum normalization on average (ranging as high as 27%), depending on tolerances and calculation method. Repositioning of simulated low-density sampled grids leads to a distribution of possible pass rates for each measured/calculated dose plane pair. These distributions can be predicted using a binomial distribution in order to establish confidence intervals that depend largely on the sampling density and the observed pass rate (i.e., the degree of difference between measured and calculated dose). These results can be extended to apply to 3D arrays of detectors, as well. Conclusions: Dose plane QA analysis can be greatly affected by choice of calculation metric and user-defined parameters, and so all pass rates should be reported with a complete description of calculation method. Pass rates for low-density arrays are subject to statistical uncertainty (vs. the high-density pass rate), but these sampling errors can be modeled using statistical confidence intervals derived from the sampled pass rate and detector density. Thus, pass rates for low-density array measurements should be accompanied by a confidence interval indicating the uncertainty of each pass rate.

  15. Variability in root production, phenology, and turnover rate among 12 temperate tree species.

    PubMed

    McCormack, M Luke; Adams, Thomas S; Smithwick, Erica A H; Eissenstat, David M

    2014-08-01

    The timing of fine root production and turnover strongly influences both the seasonal potential for soil resource acquisition among competing root systems and the plant fluxes of root carbon into soil pools. However, basic patterns and variability in the rates and timing or fine root production and turnover are generally unknown among perennial plants species. We address this shortfall using a heuristic model relating root phenology to turnover together with three years of minirhizotron observations of root dynamics in 12 temperate tree species grown in a common garden. We specifically investigated how the amount and the timing of root production differ among species and how they impact estimates of fine root turnover. Across the 12 species, there was wide variation in the timing of root production with some species producing a single root flush in early summer and others producing roots either more uniformly over the growing season or in multiple pulses. Additionally, the pattern and timing of root production appeared to be consistent across years for some species but varied in others. Root turnover rate was related to total root production (P < 0.001) as species with greater root production typically had faster root turnover rates. We also found that, within species, annual root production varied up to a threefold increase between years, which led to large interannual differences in turnover rate. Results from the heuristic model indicated that shifting the pattern or timing of root production can impact estimates of root turnover rates for root populations with life spans less than one year while estimates of root turnover rate for longer lived roots were unaffected by changes in root phenology. Overall, we suggest that more detailed observations of root phenology and production will improve fidelity of root turnover estimates. Future efforts should link patterns of root phenology and production with whole-plant life history traits and variation in annual and seasonal climate. PMID:25230473

  16. Inferring clocks when lacking rocks: the variable rates of molecular evolution in bacteria

    PubMed Central

    Kuo, Chih-Horng; Ochman, Howard

    2009-01-01

    Background Because bacteria do not have a robust fossil record, attempts to infer the timing of events in their evolutionary history requires comparisons of molecular sequences. This use of molecular clocks is based on the assumptions that substitution rates for homologous genes or sites are fairly constant through time and across taxa. Violation of these conditions can lead to erroneous inferences and result in estimates that are off by orders of magnitude. In this study, we examine the consistency of substitution rates among a set of conserved genes in diverse bacterial lineages, and address the questions regarding the validity of molecular dating. Results By examining the evolution of 16S rRNA gene in obligate endosymbionts, which can be calibrated by the fossil record of their hosts, we found that the rates are consistent within a clade but varied widely across different bacterial lineages. Genome-wide estimates of nonsynonymous and synonymous substitutions suggest that these two measures are highly variable in their rates across bacterial taxa. Genetic drift plays a fundamental role in determining the accumulation of substitutions in 16S rRNA genes and at nonsynonymous sites. Moreover, divergence estimates based on a set of universally conserved protein-coding genes also exhibit low correspondence to those based on 16S rRNA genes. Conclusion Our results document a wide range of substitution rates across genes and bacterial taxa. This high level of variation cautions against the assumption of a universal molecular clock for inferring divergence times in bacteria. However, by applying relative-rate tests to homologous genes, it is possible to derive reliable local clocks that can be used to calibrate bacterial evolution. Reviewers This article was reviewed by Adam Eyre-Walker, Simonetta Gribaldo and Tal Pupko (nominated by Dan Graur). PMID:19788732

  17. Effect of urea application rate and water content on nitrous oxide emission from a sandy loam soil - a laboratory study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agriculture is a major contributor to global anthropogenic nitrous oxide (N2O, a potent greenhouse gas) emission. Data from a pomegranate orchard indicate that N2O emission is highly variable with nitrogen application rates and irrigation methods. The aim of this study was to investigate the effect ...

  18. Slection de variables pour la classification multiclasses : Comparaisons et application la

    E-print Network

    Paris-Sud XI, Université de

    vingt huit facteurs de risque appartenant au rating CAMELS. Ces facteurs sont ordonnés selon leur and ordered variables belonging to rating CAMELS using feature selection algorithm. The comparison between

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

    PubMed

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

    2010-07-01

    Measurements of exercise heart rate (HR(ex)), HR recovery (HRR) and HR variability (HRV) are used as indices of training status. However, the day-to-day variability of these indices throughout a competitive soccer period is unknown. On 14 occasions during a 3-week competition camp, 18 under 15 (U15) and 15 under 17 (U17) years soccer players performed a 5-min submaximal run, followed by a seated 5-min recovery period. HR(ex) was determined during the last 30 s of exercise, while HRR and HRV were measured during the first and last 3 min of the post-exercise recovery period, respectively. U15 players displayed greater HR(ex) (P = 0.02) and HRR (P = 0.004) compared with the U17 players, but there was no difference in HRV (P = 0.74). The mean coefficient of variation (CV) for HR(ex) was lower than that for HRV [3.4 (90% CL, 3.1, 3.7) vs. 10.7 (9.6, 11.9)%, P < 0.001]; both were lower than that for HRR [13.3 (12.2, 14.3)%, P < 0.01]. In contrast to HR(ex) and HRR, the CV for HRV was correlated to maximal aerobic speed (r = -0.52, P = 0.002). There was no correlation between total activity time (training sessions + matches) and CV of any of the quantified variables. The variability of each of these measures and player fitness levels should be considered when interpreting changes in training status. PMID:20229253

  20. Assessment of variable camber for application to transport aircraft

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The potential benefits were determined for the variable camber of commercial transport airplanes designed for intercontinental and domestic missions. A variable camber concept was developed and incorporated into airplanes designed for the two missions. Benefits were evaluated by comparing the mission performance and direct operating costs for the variable camber airplanes with those for reference airplanes designed for the same missions but having fixed geometry high speed wings. Several technical uncertainties associated with implementing variable camber were also examined.

  1. SVM Variable selection with application to pedestrian detection

    Microsoft Academic Search

    Alain Rakotomamonjy; Frédéric Suard

    Nowadays, to solve a learning from examples problem, a large amount of data can be available due to the prolife- ration of acquisition systems. Besides, more and more fea- tures characterize each example. Variable selection algo- rithms adress the problem of selecting the input variables that are most predictive for a given task. In this paper, we present a variable

  2. Restlessness behaviour, heart rate and heart-rate variability of dairy cows milked in two types of automatic milking systems and auto-tandem milking parlours

    Microsoft Academic Search

    Lorenz Gygax; Isabelle Neuffer; Christine Kaufmann; Rudolf Hauser; Beat Wechsler

    2008-01-01

    In order to assess the welfare of cows milked in automatic milking systems (AMS), restlessness behaviour during milking (stepping, foot-lifting), heart rate (HR) and heart-rate variability (HRV) were investigated in cows milked in two different AMS models (AMS-1, AMS-2) and in auto-tandem milking parlours (ATM) on four commercial farms in each case.Stepping rates and proportions of milkings with foot-lifting were

  3. A study of heart rate and heart rate variability in human subjects exposed to occupational levels of 50 Hz circularly polarised magnetic fields

    Microsoft Academic Search

    Mardi L. Sait; Andrew W. Wood; Hassan A. Sadafi

    1999-01-01

    The effects of power-frequency magnetic fields on heart rate and heart rate variability (HRV) were studied in groups of adult volunteers. Exposure consisted of 28 ?T (280 mG) at 50 Hz (circularly polarized) for 100 or 150 seconds either following or prior to a similar period of sham-exposure. A small but significant slowing of heart rate of the order of

  4. Heart Rate Variability and its Correlation with Pulmonary Function Test of Smokers

    PubMed Central

    Behera, Joshil Kumar; Sood, Sushma; Kumar, Naresh; Sharma, Kirti; Mishra, Reshmi; Roy, Prasanta Saha

    2013-01-01

    Context: Though many studies have been conducted on the effect of chronic smoking on pulmonary function test (PFT) and heart rate variability (HRV), no study has found a correlation between the pulmonary function test and heart rate variability parameters so far. Aim: The aim was to study if there was a correlation, if any, between PFT and HRV. Settings and Design: Thirty male subjects who were chronic smokers of at least 10 pack years and another 30 nonsmoking healthy males were included in the study and were matched for age, height, weight, and body surface area. Materials and Methods: PFT and HRV were performed on these subjects and a correlation was statistically derived. Statistical Analysis Used: Spearman?s correlation coefficient was used for the analysis of HRV and PFT. Multiple stepwise regression analysis was used subsequently. Results: HF and LF showed correlation coefficients of 0.378 and-0.383 with forced expiratory volume in the first second (FEV 1) and peak expiratory flow rate (PEFR), respectively. It was found that only FEV 1/FVC was having a statistically significant regression coefficient with HF the R-value was found to be 0.425 while with other parameters, it was not significant. Conclusion: We conclude that smoking affects all the parameters of PFT and HRV. Since there is a correlation between PFT parameters (PEFR and FEV1) and HRV parameter (LF and HF), this can help us in predicting cardiac morbidity in chronic smokers. So HRV should be included as a routine test along with PFT in chronic smokers for early diagnosis of cardiac involvement. PMID:23580921

  5. Assessment of electrocardiography, echocardiography, and heart rate variability in dynamic and static type athletes

    PubMed Central

    Toufan, Mehrnoush; Kazemi, Babak; Akbarzadeh, Fariborz; Ataei, Amin; Khalili, Majid

    2012-01-01

    Background: Over the last two decades, morphological cardiac changes induced by athletic conditioning have been of great interest. Therefore, several studies have been orchestrated to delineate electrocardiography (ECG), echocardiography, and heart rate variability (HRV) findings in athletes. Purpose: To assess the ECG, echocardiography, and HRV in a group of dynamic and static type athletes. Methods: Fifty professional athletes (20 static and 30 dynamic exercise athletes) and 50 healthy nonathletes (control group) were recruited. Standard 12-lead ECG and transthoracic echocardiography was performed on all athletes and the control group. Through echocardiography, variables including left ventricular (LV) end-diastolic/systolic diameter, LV mass, and left atrial volume index were measured. In addition, both the athletes and the control group underwent ECG Holter monitoring for 15 minutes and several parameters related to HRV (time and frequency domain) were recorded. Results: The most common ECG abnormalities among the athletes were sinus bradycardia and incomplete right bundle branch block. LV end-diastolic diameter and left atrial volume index were significantly greater in the dynamic athletes (P < 0.001). LV end-systolic diameter was significantly lower in the static group (P < 0.001). LV mass of the dynamic and static athletes was significantly greater than that of the controls (P < 0.001). Among the ECG Holter monitoring findings, the dynamic athletes had lower systolic blood pressure than the controls (P = 0.01). Heart rate was lowest in the control group (P < 0.001). Conclusion: The most common ECG abnormalities among adolescent Iranian athletes were sinus bradycardia and incomplete right bundle branch block. Static exercise seemed to reduce LV end-systolic diameter, while dynamic exercise resulted in increased LV end-diastolic diameter and left atrial volume index. Additionally, Iranian athletes showed no differences in HRV parameters, excluding heart rate and systolic blood pressure, compared with the nonathletes. PMID:22924010

  6. Do lambs perceive regular human stroking as pleasant? Behavior and heart rate variability analyses.

    PubMed

    Coulon, Marjorie; Nowak, Raymond; Peyrat, Julie; Chandèze, Hervé; Boissy, Alain; Boivin, Xavier

    2015-01-01

    Stroking by humans is beneficial to the human-animal relationship and improves welfare in many species that express intraspecific allogrooming, but very few studies have looked at species like sheep that do not express such contact except around parturition. This study investigated the way lambs perceive regular human tactile contact using behavioral and physiological responses. Twenty-four lambs were reared and bucket-fed in groups of four. All were stroked daily by their familiar caregiver. At 8 weeks of age, the lambs were individually tested in their home pen but in a 1×1m open-barred pen after a 15 h period of habituation to physical separation from peers while remaining in visual and auditory contact. Half of the lambs received stroking by their caregiver for 8 min and half were exposed to their caregiver's immobile presence. Heart rate and heart rate variability were recorded and analyzed by 2-min slots over the same interval based on three measures: mean heart rate value (HR), root mean square of successive differences (RMSSD) and standard deviation of all intervals measured between consecutive sinus beats (SDNN). Behavioral responses (ear postures of the lamb and time spent in contact with the familiar caregiver, on the knees of the familiar caregiver, and moving) were recorded throughout the test. Lamb HR decreased continuously while in the presence of their caregiver. Lambs being stroked showed slower HR and higher RMSSD which reflected positive emotional states compared to lambs left unstroked. All behavioral variables were highly correlated with the main component axis of the PCA analyses: the more the animals stayed in contact with their caregiver, the less they moved and the more their ears were hanging. This first component clearly differentiates lambs being stroked or not. Behavioral and physiological observations support the hypothesis that gentle physical contact with the caregiver is perceived positively by lambs. PMID:25714604

  7. Do Lambs Perceive Regular Human Stroking as Pleasant? Behavior and Heart Rate Variability Analyses

    PubMed Central

    Coulon, Marjorie; Nowak, Raymond; Peyrat, Julie; Chandèze, Hervé; Boissy, Alain; Boivin, Xavier

    2015-01-01

    Stroking by humans is beneficial to the human-animal relationship and improves welfare in many species that express intraspecific allogrooming, but very few studies have looked at species like sheep that do not express such contact except around parturition. This study investigated the way lambs perceive regular human tactile contact using behavioral and physiological responses. Twenty-four lambs were reared and bucket-fed in groups of four. All were stroked daily by their familiar caregiver. At 8 weeks of age, the lambs were individually tested in their home pen but in a 1×1m open-barred pen after a 15h period of habituation to physical separation from peers while remaining in visual and auditory contact. Half of the lambs received stroking by their caregiver for 8min and half were exposed to their caregiver’s immobile presence. Heart rate and heart rate variability were recorded and analyzed by 2-min slots over the same interval based on three measures: mean heart rate value (HR), root mean square of successive differences (RMSSD) and standard deviation of all intervals measured between consecutive sinus beats (SDNN). Behavioral responses (ear postures of the lamb and time spent in contact with the familiar caregiver, on the knees of the familiar caregiver, and moving) were recorded throughout the test. Lamb HR decreased continuously while in the presence of their caregiver. Lambs being stroked showed slower HR and higher RMSSD which reflected positive emotional states compared to lambs left unstroked. All behavioral variables were highly correlated with the main component axis of the PCA analyses: the more the animals stayed in contact with their caregiver, the less they moved and the more their ears were hanging. This first component clearly differentiates lambs being stroked or not. Behavioral and physiological observations support the hypothesis that gentle physical contact with the caregiver is perceived positively by lambs. PMID:25714604

  8. Decoding Continuous Variables from Neuroimaging Data: Basic and Clinical Applications

    PubMed Central

    Cohen, Jessica R.; Asarnow, Robert F.; Sabb, Fred W.; Bilder, Robert M.; Bookheimer, Susan Y.; Knowlton, Barbara J.; Poldrack, Russell A.

    2011-01-01

    The application of statistical machine learning techniques to neuroimaging data has allowed researchers to decode the cognitive and disease states of participants. The majority of studies using these techniques have focused on pattern classification to decode the type of object a participant is viewing, the type of cognitive task a participant is completing, or the disease state of a participant's brain. However, an emerging body of literature is extending these classification studies to the decoding of values of continuous variables (such as age, cognitive characteristics, or neuropsychological state) using high-dimensional regression methods. This review details the methods used in such analyses and describes recent results. We provide specific examples of studies which have used this approach to answer novel questions about age and cognitive and disease states. We conclude that while there is still much to learn about these methods, they provide useful information about the relationship between neural activity and age, cognitive state, and disease state, which could not have been obtained using traditional univariate analytical methods. PMID:21720520

  9. Performance analysis of low rate wireless technologies for medical applications

    Microsoft Academic Search

    Nada Golmie; David Cypher; Olivier Rébala

    2005-01-01

    In this article we discuss what wireless technologies can be used for medical applications and how well they perform in a healthcare\\/hospital environment. We consider the emerging low-rate Wireless Personal Area Network (WPAN) technology as specified in the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard and evaluate its suitability to the medical environment. We focus on scalability issues

  10. Functional, fractal nonlinear response with application to rate processes with memory, allometry, and population genetics

    PubMed Central

    Vlad, Marcel O.; Morán, Federico; Popa, Vlad T.; Szedlacsek, Stefan E.; Ross, John

    2007-01-01

    We give a functional generalization of fractal scaling laws applied to response problems as well as to probability distributions. We consider excitations and responses, which are functions of a given state vector. Based on scaling arguments, we derive a general nonlinear response functional scaling law, which expresses the logarithm of a response at a given state as a superposition of the values of the logarithms of the excitations at different states. Such a functional response law may result from the balance of different growth processes, characterized by variable growth rates, and it is the first order approximation of a perturbation expansion similar to the phase expansion. Our response law is a generalization of the static fractal scaling law and can be applied to the study of various problems from physics, chemistry, and biology. We consider some applications to heterogeneous and disordered kinetics, organ growth (allometry), and population genetics. Kinetics on inhomogeneous reconstructing surfaces leads to rate equations described by our nonlinear scaling law. For systems with dynamic disorder with random energy barriers, the probability density functional of the rate coefficient is also given by our scaling law. The relative growth rates of different biological organs (allometry) can be described by a similar approach. Our scaling law also emerges by studying the variation of macroscopic phenotypic variables in terms of genotypic growth rates. We study the implications of the causality principle for our theory and derive a set of generalized Kramers–Kronig relationships for the fractal scaling exponents. PMID:17360340

  11. Power-Law Behavior of Beat-Rate Variability in Monolayer Cultures of Neonatal Rat Ventricular Myocytes

    Microsoft Academic Search

    Jan P. Kucera; Marc O. Heuschkel; Philippe Renaud; Stephan Rohr

    2010-01-01

    It is known that extracardiac factors (nervous, humoral, and hemodynamic) participate in the power-law behavior of heart-rate variability. To assess whether intrinsic properties of cardiac tissue might also be involved, beat-rate variability was studied in spontaneously beating cell cultures devoid of extracardiac influences. Extracellular electrograms were recorded from monolayer cultures of neonatal rat ventricular myocytes under stable incubating conditions for

  12. Method of variable bias and its application to estimating subsurface temperature

    SciTech Connect

    Deming, D.; Hanor, J.S.; Nunn, J.A. (Louisiana State Univ., Baton Rouge (USA))

    1990-10-01

    A method of obtaining variable-bias estimates of physical quantities from noisy and incomplete data is introduced, and its application to estimating subsurface temperature is illustrated by application to temperature data from the Iberia salt dome in south Louisiana.

  13. Transverse spatiotemporal variability of lowland river properties and effects on metabolic rate estimates

    NASA Astrophysics Data System (ADS)

    Villamizar, Sandra R.; Pai, Henry; Butler, Christopher A.; Harmon, Thomas C.

    2014-01-01

    Variability of river properties such as temperature, velocity, dissolved oxygen (DO), and light at small scales (centimeters to meters) can play an important role in the local exchanges of energy and mass. We hypothesize that significant transverse cross-sectional DO variation is observable within a river. Such variation may influence conventional single-station metabolic rate (primary production and respiration) estimates with respect to DO probe location, and reveal important connections between physical and biogeochemical processes and their drivers in rivers. Using a mobile sensor system, we measured river properties across a bend in the lower Merced River in Central California under stationary flow conditions in April and September. Cross-sectional temperature, DO, and chlorophyll-a concentrations exhibited modest but significant gradients, which varied in magnitude and direction on a diel basis. The spatiotemporal variation was consistent with reach geomorphology and incident light patterns. Gross primary production (GPP), community respiration (CR24), and net ecosystem production (NEP) rates estimates derived from local DO and temperature time series varied by 3-10% over the river cross section, with greater variation in late summer. The presence of transverse metabolic rate gradients in this relatively simple reach implies the existence of substantial gradients in more complex river regimes, such as those spanning distinctively different microhabitats, transient storage zones, and related distributed biogeochemical zones.

  14. Changes in heart-rate variability of survivors of nasopharyngeal cancer during Tai Chi Qigong practice

    PubMed Central

    Fong, Shirley S.M.; Wong, Janet Y.H.; Chung, Louisa M.Y.; Yam, Timothy T.T.; Chung, Joanne W.Y.; Lee, Y.M.; Chow, Lina P.Y.; Luk, W.S.; Ng, Shamay S.M.

    2015-01-01

    [Purpose] To explore the changes in heart-rate variability (HRV) of survivors of nasopharyngeal cancer (NPC) before, during, and after a Tai Chi (TC) Qigong exercise. [Subjects and Methods] Eleven survivors of NPC participated voluntarily in the study. The heart rate of each participant was measured continuously for 1 minute before the TC Qigong intervention, during the 5-minute TC Qigong intervention, and for 1 minute after the intervention, using a Polar heart-rate monitor. Spectral HRV was expressed in terms of normalised low frequency (LF) power, normalised high frequency (HF) power, and the low frequency/high frequency (LF/HF) power ratio. [Results] Both the LF-power and the HF-power components had significant time effects. However, the time effect of the LF/HF power ratio was not significant. Post hoc contrast analysis revealed a significant decrease in LF power and a concomitant increase in HF power during the 4th minute and 5th minute of the TC Qigong exercise. [Conclusion] Five minutes of TC Qigong exercise was found to improve HRV by increasing HF power and decreasing LF power, but these effects were transient. TC Qigong might be an appropriate exercise for improving the ANS function and psychological and cardiac health of survivors of NPC.

  15. Inward-attention meditation increases parasympathetic activity: a study based on heart rate variability.

    PubMed

    Wu, Shr-Da; Lo, Pei-Chen

    2008-10-01

    Phenomenon of the heart rate variability (HRV) during various meditation techniques has been reported. However, most of these techniques emphasized the skill of slow breathing (<0.15 Hz). This paper reports our study on HRV during meditation which emphasizes inward attention. Inward attention has been an important approach for the Zen-meditation practitioners to enter into transcendental consciousness. Two groups of subjects were investigated, 10 experimental subjects with Zen-meditation experience and 10 control subjects without any meditation experience. We analyzed HRV both in time and frequency domains. The results revealed both common and different effects on HRV between inward-attention meditation and normal rest. The major difference of effects between two groups were the decrease of LF/HF ratio and LF norm as well as the increase of HF norm, which suggested the benefit of a sympathovagal balance toward parasympathetic activity. Moreover, we observed regular oscillating rhythms of the heart rate when the LF/HF ratio was small under meditation. According to previous studies, regular oscillations of heart rate signal usually appeared in the low-frequency band of HRV under slow breathing. Our findings showed that such regular oscillations could also appear in the high-frequency band of HRV but with smaller amplitude. PMID:18997439

  16. Changes in heart-rate variability of survivors of nasopharyngeal cancer during Tai Chi Qigong practice.

    PubMed

    Fong, Shirley S M; Wong, Janet Y H; Chung, Louisa M Y; Yam, Timothy T T; Chung, Joanne W Y; Lee, Y M; Chow, Lina P Y; Luk, W S; Ng, Shamay S M

    2015-05-01

    [Purpose] To explore the changes in heart-rate variability (HRV) of survivors of nasopharyngeal cancer (NPC) before, during, and after a Tai Chi (TC) Qigong exercise. [Subjects and Methods] Eleven survivors of NPC participated voluntarily in the study. The heart rate of each participant was measured continuously for 1 minute before the TC Qigong intervention, during the 5-minute TC Qigong intervention, and for 1 minute after the intervention, using a Polar heart-rate monitor. Spectral HRV was expressed in terms of normalised low frequency (LF) power, normalised high frequency (HF) power, and the low frequency/high frequency (LF/HF) power ratio. [Results] Both the LF-power and the HF-power components had significant time effects. However, the time effect of the LF/HF power ratio was not significant. Post hoc contrast analysis revealed a significant decrease in LF power and a concomitant increase in HF power during the 4th minute and 5th minute of the TC Qigong exercise. [Conclusion] Five minutes of TC Qigong exercise was found to improve HRV by increasing HF power and decreasing LF power, but these effects were transient. TC Qigong might be an appropriate exercise for improving the ANS function and psychological and cardiac health of survivors of NPC. PMID:26157266

  17. The Sensitivity of Response Rate to the Rate of Variable-Interval Reinforcement for Pigeons and Rats: A Review

    ERIC Educational Resources Information Center

    Shull, Richard L.

    2005-01-01

    The relation between the rate of a response ("B") and the rate of its reinforcement ("R") is well known to be approximately hyperbolic: B = kR/(R + R[subscript o]), where k represents the maximum response rate, and R[subscript o] indicates the rate of reinforcers that will engender a response rate equal to half its maximum value. A review of data…

  18. Slip rate variability along the Kunlun Fault using PS-InSAR

    NASA Astrophysics Data System (ADS)

    Nockles, V.; Parsons, B.; Wright, T. J.; Holley, R.; Shan, X.

    2013-12-01

    Variability in slip rate along the left-lateral Kunlun Fault in Tibet has been investigated spatially, using geological observations, by a number of previous authors notably Van der Woerd et al, 2002 and Kirby et al, 2007 and the results interpreted as a systematic decrease eastwards towards the fault tip. To investigate further whether systematic trends can be observed we use satellite radar interferometry (InSAR) to estimate apparent slip rates along the Eastern Kunlun fault. We processed a total of 108 passes, each 400km in length, on 5 tracks along a 900km section of the eastern part of the Kunlun Fault running from the end of the Kokoxili rupture, at the intersection with the Kunlun Pass, to the tip of the fault at Maqu, on the eastern margin of Tibet. We compare the results for PS-InSAR and standard InSAR on two of the tracks and find them to be both consistent and complementary. Standard InSAR effectively delineates long wavelength features, whilst PS-InSAR provides valuable data in regions that are incoherent using standard techniques. Using PS-InSAR enables us to reduce decorrelation effects and extend our data set by including larger perpendicular baselines. For example, the response to a magnitude 6.1 earthquake on the right lateral Elashan Fault, just north of the Kunlun fault, is incoherent close to the fault in standard InSAR creating unwrapping problems. PS-InSAR, however, is coherent and shows a clear signal related to this event. In general, in a non-urban setting, where data is coherent using standard InSAR the noise levels are lower than for PS-InSAR due to the spatial averaging of the data and the inclusion of only small baseline interferograms, whereas PS-InSAR performs better in less coherent areas. We construct profiles of the mean line-of-sight velocity for 5 sections of the fault, then invert to solve for the best fitting model parameters using an elastic dislocation model of a strike slip fault. We obtain slip rates along the Kunlun Fault, for a locking depth of 10km, of 12-15mm/yr at Burdan Budai Shan (95.5°E), reducing to 7mm/yr where the fault is offset by a pull apart basin (98.8°E), increasing back to 9mm/yr (100.16°E), and then reducing to less than 6mm/yr at the fault tip (102.1°E). Our results match the overall trends seen with geological data but are seen to be a few mm lower along the middle section of the fault. These differences can possibly be attributed to variations through the earthquake cycle as geological slip rates average over the earthquake cycle, whilst geodetic slip rates represent a snap shot at a given time within it. For example, near the end of the Kokoxili rupture, where a post seismic signal might be expected, the apparent slip rates are seen to be higher than for geological slip rates. In addition, we consider the interaction of the main fault with off-shoots to the south of the Kunlun fault, and the effect of thrust faulting to the north, by looking for spatial variability in the shape of the profiles. References: Kirby et al (2007), Slip rate gradients along the Eastern Kunlun fault, Tectonics, 26, doi:10.1029/2006TC002033 Van der Woer ,J., et al. (2002), The 14 November 2001, Mw = 7.8 Kokxili earthquake in northern Tibet (Qinghai Province, China), Seismol. Res. Lett., 73, 125-135

  19. Acute effects of caffeine on heart rate variability in habitual caffeine consumers.

    PubMed

    Rauh, Robert; Burkert, Michaela; Siepmann, Martin; Mueck-Weymann, Michael

    2006-05-01

    During the last years, heart rate variability (HRV) has become a promising risk factor for cardiovascular events. However, the effect of caffeine on HRV in habitual caffeine consumers has barely been investigated. Therefore, we treated 30 male habitual caffeine users in a randomized double-blinded crossover study design with either placebo, 100 or 200 mg caffeine orally and determined parameters of HRV under resting conditions and metronomic breathing. As result, we could not detect significant differences in HRV parameters up to 90 min after drug ingestion. We conclude that modest amounts of caffeine do not reveal negative nor positive effects on HRV within the first 90 min after drug ingestion in young and healthy habitual caffeine consumers. However, further research is necessary to determine the effects of caffeine on HRV in habitual caffeine users, healthy as well as suffering from diabetes, hypertension and postmyocardial infarction. PMID:16640511

  20. Discrimination between Healthy and Sick Cardiac Autonomic Nervous System by Detrended Heart Rate Variability Analysis

    E-print Network

    Y. Ashkenazy; M. Lewkowicz; J. Levitan; S. Havlin; K. Saermark; H. Moelgaard; P. E. Bloch Thomsen

    1998-10-13

    Multiresolution Wavelet Transform and Detrended Fluctuation Analysis have been recently proven as excellent methods in the analysis of Heart Rate Variability, and in distinguishing between healthy subjects and patients with various dysfunctions of the cardiac nervous system. We argue that it is possible to obtain a distinction between healthy subjects/patients of at least similar quality by, first, detrending the time-series of RR-intervals by subtracting a running average based on a local window with a length of around 32 data points, and then, calculating the standard deviation of the detrended time-series. The results presented here indicate that the analysis can be based on very short time-series of RR-data (7-8 minutes), which is a considerable improvement relative to 24-hours Holter recordings.

  1. Heart rate variability differs between right- and left-handed individuals.

    PubMed

    Yüksel, Ramazan; Arslan, Muzeyyen; Dane, Senol

    2014-06-01

    Previous studies reported reduced longevity in left-handers with the suggestion that it may be associated with different heart diseases. Therefore, differences in heart rate variability (HRV), an index of autonomic cardiac activity, were examined for right- and left-handed individuals. 120 healthy young university students (75 women, 45 men; M age = 20.4 yr., SD = 1.5) volunteered. Handedness was assessed with the Edinburgh Handedness Inventory and HRV was measured via electrocardiography. The results suggest that the left-handers' HRV was significantly different from that of right-handers on several parameters. The atypical cerebral organization of left-handers may be related to an imbalanced autonomic system that results in higher frequencies of heart irregularities. PMID:25068752

  2. A high performance, continuously variable data rate, digitally implemented BPSK modem for deep space network

    NASA Technical Reports Server (NTRS)

    Paik, W. H.

    1981-01-01

    This paper describes a high performance, digital, BPSK modem designed to improve the telemetry data handling capability of NASA's Deep Space Network. The data rate is continuously variable from 0.5 Mbps to 30 Mbps. It uses newly designed, high speed digital alogrithms for receive filtering, carrier tracking, bit timing and AGC. The carrier and bit time tracking loops have been designed to provide fast acquisition and low tracking phase jitter at E sub b/N sub 0 as low as -4 dB and bit transition density as low as 10%. The performance of the modem is within 0.65 dB below 10 Mbps, 1.0 dB from 10 Mbps to 20 Mbps, and 1.5 dB above 20 Mbps of theoretical coherent BPSK at a BER of 0.0004.

  3. Change in heart rate variability after the adult attachment interview in dissociative patients.

    PubMed

    Farina, Benedetto; Speranza, Anna Maria; Imperatori, Claudio; Quintiliani, Maria Isabella; Della Marca, Giacomo

    2015-01-01

    The aim of this study was to assess heart rate variability (HRV) in individuals with dissociative disorders (DD) before and after the Adult Attachment Interview (AAI). Electrocardiograms were recorded before, during, and after the AAI in 13 individuals with DD and 13 healthy participants matched for age and gender. Significant change in HRV was observed only in the DD group. After the AAI, those with DD showed significant increases in the low frequency/high frequency ratio (pre-AAI = 1.91 ± 1.19; post-AAI = 4.03 ± 2.40; Wilcoxon test = -2.76, p = .005). Our results suggest that the retrieval of childhood attachment experiences in individuals with DD is associated with a change in HRV patterns that could reflect the emotion dysregulation of dissociative psychopathological processes. PMID:25492425

  4. Wavelet-based correlations of impedance cardiography signals and heart rate variability

    NASA Astrophysics Data System (ADS)

    Podtaev, Sergey; Dumler, Andrew; Stepanov, Rodion; Frick, Peter; Tziberkin, Kirill

    2010-04-01

    The wavelet-based correlation analysis is employed to study impedance cardiography signals (variation in the impedance of the thorax z(t) and time derivative of the thoracic impedance (- dz/dt)) and heart rate variability (HRV). A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. The modulus of wavelet-correlation function shows the level of correlation, and the phase indicates the mean phase shift of oscillations at the given scale (frequency). Significant correlations essentially exceeding the values obtained for noise signals are defined within two spectral ranges, which correspond to respiratory activity (0.14-0.5 Hz), endothelial related metabolic activity and neuroendocrine rhythms (0.0095-0.02 Hz). Probably, the phase shift of oscillations in all frequency ranges is related to the peculiarities of parasympathetic and neuro-humoral regulation of a cardiovascular system.

  5. Automatic stress-relieving music recommendation system based on photoplethysmography-derived heart rate variability analysis.

    PubMed

    Shin, Il-Hyung; Cha, Jaepyeong; Cheon, Gyeong Woo; Lee, Choonghee; Lee, Seung Yup; Yoon, Hyung-Jin; Kim, Hee Chan

    2014-01-01

    This paper presents an automatic stress-relieving music recommendation system (ASMRS) for individual music listeners. The ASMRS uses a portable, wireless photoplethysmography module with a finger-type sensor, and a program that translates heartbeat signals from the sensor to the stress index. The sympathovagal balance index (SVI) was calculated from heart rate variability to assess the user's stress levels while listening to music. Twenty-two healthy volunteers participated in the experiment. The results have shown that the participants' SVI values are highly correlated with their prespecified music preferences. The sensitivity and specificity of the favorable music classification also improved as the number of music repetitions increased to 20 times. Based on the SVI values, the system automatically recommends favorable music lists to relieve stress for individuals. PMID:25571461

  6. The Influence of Neuromuscular Electrical Stimulation on the Heart Rate Variability in Healthy Subjects

    PubMed Central

    Kang, Jong Ho; Hyong, In Hyouk

    2014-01-01

    [Purpose] The purpose of this study was to examine the effect of neuromuscular electrical stimulation (NMES) on heart rate variability (HRV). [Subjects and Methods] Ten healthy subjects participated in the study. All subjects received NMES with a pulse duration of 300 us and frequency of 30?Hz at the vastus lateralis and vastus medialis for 15 minutes. The stimulation intensity was adjusted in the range of 20 to 30 mA. HRV using a pulse oximeter was measured in the sitting position before and after NMES. [Results] After the NMES, all HRV data slightly increased, but there was no significance between before and after data. [Conclusion] We suggest that strengthening exercises using NMES may be undertaken safely. PMID:24926120

  7. From Prediction to Prescription: Intelligent Decision Support for Variable Rate Fertilization

    SciTech Connect

    Fink, Raymond Keith; Hoskinson, Reed Louis; Hess, John Richard

    2001-07-01

    We describe the use of machine learning methods in the analysis of spatial soil fertility, soil physical characteristics, and yield data, with a particular objective of determining local (field- to farm-scale) crop response patterns. For effective prescriptive use, the output of these tools is augmented with economic data and operational constraints, and recast as a rulebased decision support tool to maximize economic return in variable rate fertilization systems. We describe some of the practical issues addressed in development of one such system, including data preparation, adaptation of regression tree output for use in a rule-based expert system, and incorporation of real-world limits on system recommendations. Results from various field trials of this system are summarized.

  8. The Effect of Chicken Extract on Mood, Cognition and Heart Rate Variability

    PubMed Central

    Young, Hayley; Benton, David; Carter, Neil

    2015-01-01

    Chicken extract, which is rich in anserine and carnosine, has been widely taken in Asian countries as a traditional remedy with various aims, including attenuation of psychological fatigue. The effects of consuming BRAND’S Essence of Chicken (EOC) or a placebo on 46 young adults’ responses to a standard psychological “stressor” were considered. Heart rate variability (HRV), cortisol responses, mood and cognition were measured at baseline and after ten days supplementation. EOC resulted in feeling less anxious, depressed and confused and more agreeable and clearheaded. A decrease in HRV was observed after EOC but only in females. Cognition and cortisol levels were not influenced by EOC. Findings suggest that EOC may be a promising supplement to improve mood in a healthy population. PMID:25642970

  9. Comparison of finger plethysmograph to ECG in the measurement of heart rate variability.

    PubMed

    Giardino, Nicholas D; Lehrer, Paul M; Edelberg, Robert

    2002-03-01

    Two experiments compared finger plethysmograph (FP) to electrocardiogram (ECG) in providing accurate heart periods for use in heart rate variability (HRV) calculations. In Experiment 1, simultaneous ECG and FP recordings were taken from 16 healthy subjects at rest. In Experiment 2, 10 additional healthy subjects were recorded at rest and during the Stroop Color-Word Test. In both studies, high correlations were found between FP-derived and ECG-derived band variance for high and low frequency HRV at rest. But, during the Stroop task, correlations were strongly diminished. In addition, under both conditions, HRV measures were significantly higher using the FP signal. Thus, FP may be adequate for determining HRV at rest, but, for experimental use, ECG may still be recommended. Nonetheless, further studies that include test-retest reliability assessment of both data collection techniques are warranted before a more certain determination can be made. PMID:12212675

  10. Spectral analysis of short-term blood pressure and heart rate variability in uremic patients.

    PubMed

    Cloarec-Blanchard, L; Girard, A; Houhou, S; Grünfeld, J P; Elghozi, J L

    1992-06-01

    Short-term fluctuations in blood pressure (BP) and heart rate (HR) were quantified to assess autonomic nervous system (ANS) dysfunction in six dialysis patients, compared to six control subjects of similar age. Indirect finger BP was measured by a Finapres device. Analog-to-digital conversion of the BP was used to determine systolic BP (SBP), diastolic BP (DBP) and HR every second. The equidistant sampling allowed a direct spectral analysis using a fast Fourier transform algorithm. Uremic patients exhibited reduced BP and HR short-term variabilities, with a dramatic reduction in the amplitude of the 0.1 Hz component (Mayer waves) of SBP and DBP spectra. Dialysis did not produce any consistent immediate improvement in the amplitude of the Mayer waves. Our study thus indicates impaired cardiovascular ANS function in uremic patients. PMID:1630069

  11. Scale Specific and Scale Independent Measures of Heart Rate Variability as Risk Indicators

    E-print Network

    Y. Ashkenazy; M. Lewkowicz; J. Levitan; S. Havlin; K. Saermark; H. Moelgaard; P. E. Bloch Thomsen; M. Moller; U. Hintze; H. V. Huikuri

    2000-11-22

    We study the Heart Rate Variability (HRV) using scale specific variance and scaling exponents as measures of healthy and cardiac impaired individuals. Our results show that the variance and the scaling exponent are uncorrelated. We find that the variance measure at certain scales is well suited to separate healthy subjects from heart patients. However, for cumulative survival probability the scaling exponents outperform the variance measure. Our risk study is based on a database containing recordings from 428 individuals after myocardial infarct (MI) and on database containing 105 healthy subjects and 11 heart patients. The results have been obtained by applying three recently developed methods (DFA - Detrended Fluctuation Analysis, WAV - Multiresolution Wavelet Analysis, and DTS - Detrended Time Series analysis) which are shown to be highly correlated.

  12. Sediment yield variability in Spain: a quantitative and semiqualitative analysis using reservoir sedimentation rates

    NASA Astrophysics Data System (ADS)

    Verstraeten, Gert; Poesen, Jean; de Vente, Joris; Koninckx, Xenia

    2003-03-01

    An existing dataset of area-specific sediment yield (SSY) for 60 catchments in Spain that was retrieved from sediment deposition rates in reservoirs [Avendaño Salas, C., Sanz Montero, E., Rayán, C., Gómez Montaña, 1997. Sediment yield at Spanish reservoirs and its relationship with the drainage basin area. In: Proceedings of the 19th Symposium of Large Dams, Florence, 1997. ICOLD (International Committee on Large Dams), pp. 863-874] reveals that catchment area alone explains only 17% of the variability in SSY. In this study, an attempt to explain the remaining variability in SSY was made using a quantitative and a semiqualitative approach for 22 catchments. During a field survey, the 22 selected catchments were characterised by topography, vegetation cover, lithology, shape and the presence of gullies in the broad vicinity of the reservoir. This information was used to develop a factorial scoring index model that provides a fairly accurate and reliable prediction of SSY. A classical multiple regression model using climatic, topographic and land use properties derived from regional datasets could not explain as much variance as the qualitative index model, nor did it appear to be as reliable. The same conclusion could be drawn when using the CORINE soil erosion risk map of southern Europe. The low prediction capability of the multiple regression models and the CORINE soil erosion risk map could be attributed mainly to the fact that these methods do not incorporate gully erosion and that the land cover data are not a good representation of soil cover. Both variables have been shown to be of great importance during the field surveys. Future assessments of SSY could be quickly and efficiently made using the proposed factorial scoring index model. In comparison with other models, which demand more data, the index model offers an alternative prediction tool.

  13. Integrated Central-Autonomic Multifractal Complexity in the Heart Rate Variability of Healthy Humans

    PubMed Central

    Lin, D. C.; Sharif, A.

    2012-01-01

    Purpose of Study: The aim of this study was to characterize the central-autonomic interaction underlying the multifractality in heart rate variability (HRV) of healthy humans. Materials and Methods: Eleven young healthy subjects participated in two separate ~40?min experimental sessions, one in supine (SUP) and one in, head-up-tilt (HUT), upright (UPR) body positions. Surface scalp electroencephalography (EEG) and electrocardiogram (ECG) were collected and fractal correlation of brain and heart rate data was analyzed based on the idea of relative multifractality. The fractal correlation was further examined with the EEG, HRV spectral measures using linear regression of two variables and principal component analysis (PCA) to find clues for the physiological processing underlying the central influence in fractal HRV. Results: We report evidence of a central-autonomic fractal correlation (CAFC) where the HRV multifractal complexity varies significantly with the fractal correlation between the heart rate and brain data (P?=?0.003). The linear regression shows significant correlation between CAFC measure and EEG Beta band spectral component (P?=?0.01 for SUP and P?=?0.002 for UPR positions). There is significant correlation between CAFC measure and HRV LF component in the SUP position (P?=?0.04), whereas the correlation with the HRV HF component approaches significance (P?=?0.07). The correlation between CAFC measure and HRV spectral measures in the UPR position is weak. The PCA results confirm these findings and further imply multiple physiological processes underlying CAFC, highlighting the importance of the EEG Alpha, Beta band, and the HRV LF, HF spectral measures in the supine position. Discussion and Conclusion: The findings of this work can be summarized into three points: (i) Similar fractal characteristics exist in the brain and heart rate fluctuation and the change toward stronger fractal correlation implies the change toward more complex HRV multifractality. (ii) CAFC is likely contributed by multiple physiological mechanisms, with its central elements mainly derived from the EEG Alpha, Beta band dynamics. (iii) The CAFC in SUP and UPR positions is qualitatively different, with a more predominant central influence in the fractal HRV of the UPR position. PMID:22403548

  14. Emotionally excited eyeblink-rate variability predicts an experience of transportation into the narrative world.

    PubMed

    Nomura, Ryota; Hino, Kojun; Shimazu, Makoto; Liang, Yingzong; Okada, Takeshi

    2015-01-01

    Collective spectator communications such as oral presentations, movies, and storytelling performances are ubiquitous in human culture. This study investigated the effects of past viewing experiences and differences in expressive performance on an audience's transportive experience into a created world of a storytelling performance. In the experiment, 60 participants (mean age = 34.12 years, SD = 13.18 years, range 18-63 years) were assigned to watch one of two videotaped performances that were played (1) in an orthodox way for frequent viewers and (2) in a modified way aimed at easier comprehension for first-time viewers. Eyeblink synchronization among participants was quantified by employing distance-based measurements of spike trains, D (spike) and D (interval) (Victor and Purpura, 1997). The results indicated that even non-familiar participants' eyeblinks were synchronized as the story progressed and that the effect of the viewing experience on transportation was weak. Rather, the results of a multiple regression analysis demonstrated that the degrees of transportation could be predicted by a retrospectively reported humor experience and higher real-time variability (i.e., logarithmic transformed SD) of inter blink intervals during a performance viewing. The results are discussed from the viewpoint in which the extent of eyeblink synchronization and eyeblink-rate variability acts as an index of the inner experience of audience members. PMID:26029123

  15. Emotionally excited eyeblink-rate variability predicts an experience of transportation into the narrative world

    PubMed Central

    Nomura, Ryota; Hino, Kojun; Shimazu, Makoto; Liang, Yingzong; Okada, Takeshi

    2015-01-01

    Collective spectator communications such as oral presentations, movies, and storytelling performances are ubiquitous in human culture. This study investigated the effects of past viewing experiences and differences in expressive performance on an audience’s transportive experience into a created world of a storytelling performance. In the experiment, 60 participants (mean age = 34.12 years, SD = 13.18 years, range 18–63 years) were assigned to watch one of two videotaped performances that were played (1) in an orthodox way for frequent viewers and (2) in a modified way aimed at easier comprehension for first-time viewers. Eyeblink synchronization among participants was quantified by employing distance-based measurements of spike trains, Dspike and Dinterval (Victor and Purpura, 1997). The results indicated that even non-familiar participants’ eyeblinks were synchronized as the story progressed and that the effect of the viewing experience on transportation was weak. Rather, the results of a multiple regression analysis demonstrated that the degrees of transportation could be predicted by a retrospectively reported humor experience and higher real-time variability (i.e., logarithmic transformed SD) of inter blink intervals during a performance viewing. The results are discussed from the viewpoint in which the extent of eyeblink synchronization and eyeblink-rate variability acts as an index of the inner experience of audience members.

  16. Entropy information of heart rate variability and its power spectrum during day and night

    NASA Astrophysics Data System (ADS)

    Jin, Li; Jun, Wang

    2013-07-01

    Physiologic systems generate complex fluctuations in their output signals that reflect the underlying dynamics. We employed the base-scale entropy method and the power spectral analysis to study the 24 hours heart rate variability (HRV) signals. The results show that such profound circadian-, age- and pathologic-dependent changes are accompanied by changes in base-scale entropy and power spectral distribution. Moreover, the base-scale entropy changes reflect the corresponding changes in the autonomic nerve outflow. With the suppression of the vagal tone and dominance of the sympathetic tone in congestive heart failure (CHF) subjects, there is more variability in the date fluctuation mode. So the higher base-scale entropy belongs to CHF subjects. With the decrease of the sympathetic tone and the respiratory frequency (RSA) becoming more pronounced with slower breathing during sleeping, the base-scale entropy drops in CHF subjects. The HRV series of the two healthy groups have the same diurnal/nocturnal trend as the CHF series. The fluctuation dynamics trend of data in the three groups can be described as “HF effect”.

  17. Depression as an independent determinant of decreased heart rate variability in patients post myocardial infarction

    PubMed Central

    van den Berg, M.P.; Spijkerman, T.A.; van Melle, J.P.; van den Brink, R.H.S.; Winter, J.B.; Veeger, N.J.; Ormel, J.

    2005-01-01

    Objective Depression is associated with an increased risk of cardiac morbidity and mortality in patients following myocardial infarction (MI). Our objective was to investigate the potential role of the autonomic nervous system in mediating this detrimental effect. Methods The study group consisted of 95 consecutive post-MI patients without depression and 53 post-MI patients with depression. Depressive symptoms were assessed by the Beck Depression Inventory (BDI). Activity of the autonomic nervous system was assessed by analysing heart rate variability (HRV) using 24-hour ambulatory electrocardiographic recordings as obtained three months post MI. Results Higher age, female gender and left ventricular ejection fraction <0.40 were associated with lower HRV (SDANN, and very-low-frequency and low-frequency power, but not RMSSD and high-frequency power), as was depression. In the multivariate analysis, age and left ventricular ejection fraction but not gender emerged to be independently associated with HRV. After adjustment for these two covariates, depression remained significantly associated with low HRV. Conclusions Patients with depression in the present post-MI study are characterised by decreased longer-range HRV compared with the patients without depression, independent of other clinical variables. This observation supports the concept that one of the mechanisms underlying the detrimental effect of depression on post-MI prognosis may be that depression adds to the autonomic derangement post MI. PMID:25696482

  18. Lagged Poincar\\'{e} and auto-correlation analysis of Heart rate variability in diabetes

    E-print Network

    Ghatak, S K

    2010-01-01

    The heart rate variability (HRV) in diabetic human subjects, has been analyzed using lagged Poincar\\'{e} plot, auto-correlation and the detrended fluctuation analysis methods. The parameters $SD1$, and $SD12 (= SD1/SD2)$ for Poincar\\'{e} plot for diabetic are lower than that for non-diabetic subjects and reverse is case for $SD2$ for all lagged number (m). The slope and the curvature of the plot SD12 vs m is much reduced for diabetic subject. The scatter plot of two successive interbeat intervals points out smaller variability in diabetic heart. The detrended fluctuation exponent has a higher value for diabetic group. The auto-correlation function of the deviation of interbeat interval in diabetic group shows highly correlated pattern when compared to that of normal one. The study suggests that the curvature of $SD12$ and auto-correlation method appear to be better way to assess the alteration of regulatory system on heart dynamics in diabetic condition.

  19. Associations between heart rate variability, metabolic syndrome risk factors, and insulin resistance.

    PubMed

    Stuckey, Melanie I; Kiviniemi, Antti; Gill, Dawn P; Shoemaker, J Kevin; Petrella, Robert J

    2015-07-01

    The purpose of this study was to examine differences in heart rate variability (HRV) in metabolic syndrome (MetS) and to determine associations between HRV parameters, MetS risk factors, and insulin resistance (homeostasis model assessment for insulin resistance (HOMA-IR)). Participants (n = 220; aged 23-70 years) were assessed for MetS risk factors (waist circumference, blood pressure, fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol) and 5-min supine HRV (time and frequency domain and nonlinear). HRV was compared between those with 3 or more (MetS+) and those with 2 or fewer MetS risk factors (MetS-). Multiple linear regression models were built for each HRV parameter to investigate associations with MetS risk factors and HOMA-IR. Data with normal distribution are presented as means ± SD and those without as median [interquartile range]. In women, standard deviation of R-R intervals 38.0 [27.0] ms, 44.5 [29.3] ms; p = 0.020), low-frequency power (5.73 ± 1.06 ln ms(2), 6.13 ± 1.05 ln ms(2); p = 0.022), and the standard deviation of the length of the Poincaré plot (46.8 [31.6] ms, 58.4 [29.9] ms; p = 0.014) were lower and heart rate was higher (68 [13] beats/min, 64 [12] beats/min; p = 0. 018) in MetS+ compared with MetS-, with no differences in men. Waist circumference was most commonly associated with HRV, especially frequency domain parameters. HOMA-IR was associated with heart rate. In conclusion, MetS+ women had a less favourable HRV profile than MetS- women, but there were no differences in men. HOMA-IR was associated with heart rate, not HRV. PMID:26140416

  20. Hypersonic Boundary Layer Measurements with Variable Blowing Rates Using Molecular Tagging Velocimetry

    NASA Technical Reports Server (NTRS)

    Bathel, Brett F.; Danehy, Paul M.; Johansen, Craig T.; Jones, Stephen B.; Goyne, Christopher P.

    2012-01-01

    Measurements of mean and instantaneous streamwise velocity profiles in a hypersonic boundary layer with variable rates of mass injection (blowing) of nitrogen dioxide (NO2) were obtained over a 10-degree half-angle wedge model. The NO2 was seeded into the flow from a slot located 29.4 mm downstream of the sharp leading edge. The top surface of the wedge was oriented at a 20 degree angle in the Mach 10 flow, yielding an edge Mach number of approximately 4.2. The streamwise velocity profiles and streamwise fluctuating velocity component profiles were obtained using a three-laser NO2->NO photolysis molecular tagging velocimetry method. Observed trends in the mean streamwise velocity profiles and profiles of the fluctuating component of streamwise velocity as functions of the blowing rate are described. An effort is made to distinguish between the effect of blowing rate and wall temperature on the measured profiles. An analysis of the mean velocity profiles for a constant blowing rate is presented to determine the uncertainty in the measurement for different probe laser delay settings. Measurements of streamwise velocity were made to within approximately 120 gm of the model surface. The streamwise spatial resolution in this experiment ranged from 0.6 mm to 2.6 mm. An improvement in the spatial precision of the measurement technique has been made, with spatial uncertainties reduced by about a factor of 2 compared to previous measurements. For the quiescent flow calibration measurements presented, uncertainties as low as 2 m/s are obtained at 95% confidence for long delay times (25 gs). For the velocity measurements obtained with the wind tunnel operating, average single-shot uncertainties of less than 44 m/s are obtained at 95% confidence with a probe laser delay setting of 1 gs. The measurements were performed in the 31-inch Mach 10 Air Tunnel at the NASA Langley Research Center.

  1. A Variable Turbulent Schmidt Number Formulation for Scramjet Application

    NASA Technical Reports Server (NTRS)

    Xiao, X.; Edwards, J. R.; Hassan, H. A.; Cutler, A. D.

    2004-01-01

    In high speed engines, thorough turbulent mixing of fuel and air is required to obtain high performance and high efficiency. Thus, the ability to predict turbulent mixing is crucial in obtaining accurate numerical simulation of an engine and its performance. Current state of the art in CFD simulation is to assume both turbulent Prandtl number and Schmidt numbers to be constants. However, since the mixing of fuel and air is inversely proportional to the Schmidt number, a value of 0.45 for the Schmidt number will produce twice as much diffusion as that with a value of 0.9. Because of this, current CFD tools and models have not been able to provide the needed guidance required for the efficient design of a scramjet engine. The goal of this investigation is to develop the framework needed to calculate turbulent Prandtl and Schmidt numbers as part of the solution. This requires four additional equations: two for the temperature variance and its dissipation rate and two for the concentration variance and its dissipation rate. In the current investigation emphasis will be placed on studying mixing without reactions. For such flows, variable Prandtl number does not play a major role in determining the flow. This, however, will have to be addressed when combustion is present. The approach to be used is similar to that used to develop the k-zeta model. In this approach, relevant equations are derived from the exact Navier-Stokes equations and each individual correlation is modeled. This ensures that relevant physics is incorporated into the model equations. This task has been accomplished. The final set of equations have no wall or damping functions. Moreover, they are tensorially consistent and Galilean invariant. The derivation of the model equations is rather lengthy and thus will not be incorporated into this abstract, but will be included in the final paper. As a preliminary to formulating the proposed model, the original k-zeta model with constant turbulent Prandtl and Schmidt numbers is used to model the supersonic coaxial jet mixing experiments involving He, O2 and air.

  2. Heart rate variability in the early hours of an acute myocardial infarction.

    PubMed

    Lombardi, F; Sandrone, G; Spinnler, M T; Torzillo, D; Lavezzaro, G C; Brusca, A; Malliani, A

    1996-05-15

    The occurrence of an autonomic disturbance early in acute myocardial infarction (AMI) has been reported: signs of sympathetic activation were mainly observed in relation to an anterior localization, whereas signs of vagal overactivity were more frequent in inferior wall AMI. Information is limited in relation to the persistence of these alterations during the early hours of AMI. We studied 33 patients with an AMI within 188 +/- 16 minutes from the onset of symptoms and 1 week after hospital admission. From a 20-minute Holter recording, we computed with autoregressive methodology, time and frequency domain indexes of heart rate variability. At admission, patients with an anterior wall AMI exhibited a smaller RR variance (593 +/- 121 ms2) than did those with an inferior wall AMI (1,122 +/- 191 ms2). In both groups the spectral profile was characterized by a predominant (73 +/- 4 and 61 +/- 4 normalized units) low frequency and by a small (13 +/- 2 and 22 +/- 3 normalized units) high-frequency component, indicating the presence of a sympathetic excitation and of a diminished vagal modulation. Although signs of sympathetic activation were more evident in patients with anterior wall AMI, no evidence of a vagal hyperactivity was observed in patients with inferior wall AMI. In the latter group, we noticed 1 week after the acute event an increase in the low-frequency component, which reached the values observed in patients with anterior wall AMI. Thrombolysis did not affect heart rate variability parameters. Thus, this study suggests the presence of an autonomic disturbance characterized by signs of sympathetic excitation and of a reduced vagal modulation, which was more evident in patients with an anterior localization early after AMI. PMID:8644654

  3. Changes in Heart Rate Variability Parameters after Elective Percutaneous Coronary Intervention

    PubMed Central

    Abrootan, Saeed; Yazdankhah, Saeed; Payami, Babak; Alasti, Mohammad

    2015-01-01

    Background: Patients with chronic stable angina often have a state of sympathetic hyperactivity. It is considered associated with myocardial ischemia and disappears after ischemia elimination. The aim of this study was to investigate the changes in heart rate variability parameters, a noninvasive technique for the evaluation of the autonomic nervous system activity, after successful revascularization in these patients to evaluate this theory. Methods: The patients were enrolled among those who underwent successful percutaneous coronary intervention. Short-term heart rate variability analyses of all the patients were obtained, and time-domain indices (standard deviation of normal-to-normal intervals [SDNN], standard deviation of differences of successive R-R intervals [SDSD], root-mean square differences of successive R-R intervals [rMSSD], percentage of R-R intervals differing > 10 ms from the preceding one [PNN10], percentage of R-R intervals differing > 20 ms from the preceding one [PNN20], percentage of R-R intervals differing > 30 ms from the preceding one [PNN30], percentage of R-R intervals differing > 40 ms from the preceding one [PNN40], percentage of R-R intervals differing > 50 ms from the preceding one [PNN50], percentage of R-R intervals differing > 60 ms from the preceding one [PNN60], and percentage of R-R intervals differing > 70 ms from the preceding one [PNN70]) were analyzed. All the measurements were made before and after percutaneous coronary intervention. Results: This study included 64 patients, comprising 27 men and 37 women at a mean age of 56.8 ± 9.1 years. There was a significant difference only between pre- and post-revascularization SDNN (27.5 ± 19.72 vs. 41 ± 41.4; p value = 0.013). The other parameters showed no significant differences after successful coronary intervention. Conclusion : Our data indicate that the increase in SDNN in patients with stable angina pectoris undergoing percutaneous coronary intervention seems to be prominent.

  4. Spectral analyses of systolic blood pressure and heart rate variability and their association with cognitive performance in elderly hypertensive subjects.

    PubMed

    Santos, W B; Matoso, J M D; Maltez, M; Gonçalves, T; Casanova, M; Moreira, I F H; Lourenço, R A; Monteiro, W D; Farinatti, P T V; Soares, P P; Oigman, W; Neves, M F T; Correia, M L G

    2015-08-01

    Systolic hypertension is associated with cognitive decline in the elderly. Altered blood pressure (BP) variability is a possible mechanism of reduced cognitive performance in elderly hypertensives. We hypothesized that altered beat-to-beat systolic BP variability is associated with reduced global cognitive performance in elderly hypertensive subjects. In exploratory analyses, we also studied the correlation between diverse discrete cognitive domains and indices of systolic BP and heart rate variability. Disproving our initial hypothesis, we have shown that hypertension and low education, but not indices of systolic BP and heart rate variability, were independent predictors of lower global cognitive performance. However, exploratory analyses showed that the systolic BP variability in semi-upright position was an independent predictor of matrix reasoning (B=0.08±.03, P-value=0.005), whereas heart rate variability in semi-upright position was an independent predictor of the executive function score (B=-6.36±2.55, P-value=0.02). We conclude that myogenic vascular and sympathetic modulation of systolic BP do not contribute to reduced global cognitive performance in treated hypertensive subjects. Nevertheless, our results suggest that both systolic BP and heart rate variability might be associated with modulation of frontal lobe cognitive domains, such as executive function and matrix reasoning. PMID:25518896

  5. Effects of Moderate and Vigorous Physical Activity on Heart Rate Variability in a British Study of Civil Servants

    Microsoft Academic Search

    Kirsten L. Rennie; Harry Hemingway; Meena Kumari; Eric Brunner; Marek Malik; Michael Marmot

    2003-01-01

    Physical inactivity and low resting heart rate variability (HRV) are associated with increased coronary heart disease incidence. In the Whitehall II study of civil servants aged 45-68 years (London, United Kingdom, 1997- 1999), the strength of the association of moderate and vigorous activity with higher HRV was examined. Five- minute recordings of heart rate and HRV measures were obtained from

  6. JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 32, NO. 2, JANUARY 15, 2014 257 Optical Networking With Variable-Code-Rate

    E-print Network

    Kahn, Joseph M.

    , IEEE Abstract--We evaluate the impact of variable-code-rate transceivers on cost, capacity by means of an existing analytical method which assumes the AWGN hypothesis for the nonlinear noise occupation, when compared to current fixed-rate transceivers op- erating at 100, 200 or 400 Gb/s. Finally

  7. The influence of erosion thresholds and runoff variability on the relationships among topography, climate, and erosion rate

    E-print Network

    DiBiase, Roman A.

    The influence of erosion thresholds and runoff variability on the relationships among topography, climate, and erosion rate Roman A. DiBiase1 and Kelin X. Whipple1 Received 18 May 2011; revised 20 October relating channel steepness and erosion rate provide the opportunity to evaluate the role of thresholds

  8. Comparison of detrended fluctuation analysis and spectral analysis for heart rate variability in sleep and sleep apnea

    Microsoft Academic Search

    Thomas Penzel; Jan W. Kantelhardt; Ludger Grote; Jörg-Hermann Peter; Armin Bunde

    2003-01-01

    Sleep has been regarded as a testing situation for the autonomic nervous system, because its activity is modulated by sleep stages. Sleep-related breathing disorders also influence the autonomic nervous system and can cause heart rate changes known as cyclical variation. We investigated the effect of sleep stages and sleep apnea on autonomic activity by analyzing heart rate variability (HRV). Since

  9. Comparison of Detrended Fluctuation Analysis and Spectral Analysis for Heart Rate Variability in Sleep and Sleep Apnea

    Microsoft Academic Search

    Thomas Penzel; Jan W. Kantelhardt; Ludger Grote; Jörg-Hermann Peter; Armin Bunde

    2003-01-01

    Sleep has been regarded as a testing situation for the autonomic nervous system, because its activity is modulated by sleep stages. Sleep-related breathing disorders also influence the autonomic nervous system and can cause heart rate changes known as cyclical variation. We investigated the effect of sleep stages and sleep apnea on autonomic activity by analyzing heart rate variability (HRV). Since

  10. Parent-Youth Rating Concordance for Hair Pulling Variables, Functional Impairment, and Anxiety Scale Scores in Trichotillomania

    ERIC Educational Resources Information Center

    Keuthen, Nancy J.; Flessner, Christopher A.; Woods, Douglas W.; Franklin, Martin E.; Piacentini, John A.; Khanna, Muniya; Moore, Phoebe; Cashin, Susan

    2008-01-01

    Knowledge of cross-informant rating concordance is critical for the assessment of child and adolescent problems in clinical and research settings. We explored parent-youth rating concordance for hair pulling variables, functional impairment, and anxiety symptoms in a sample of child and adolescent hair pullers (n = 133) satisfying conservative…

  11. An Integrated Optimization Of Large-Scale Wind With Variable Rating Coupled To Compressed Air Energy Storage

    Microsoft Academic Search

    Samir Succar; Jeffery B. Greenblatt; David Denkenberger; Robert H. Williams

    2006-01-01

    Abstract A methodology is presented for jointly optimizing the wind turbine specific rating and the storage configuration for a large-scale wind farm coupled to compressed air energy storage (CAES). By allowing the wind-storage system to be optimized in an integrated, variable rating framework the overall cost of energy (COE) can be reduced substantially. These changes also enhance the capacity factor

  12. An Area-Efficient Variable Length Decoder IP Core Design for MPEG1\\/2\\/4 Video Coding Applications

    Microsoft Academic Search

    Chih-Da Chien; Keng-Po Lu; Yu-Min Chen; Jiun-In Guo; Yuan-Sun Chu; Ching-Lung Su

    2006-01-01

    This paper proposes an area-efficient variable length decoder (VLD) IP core design for MPEG-1\\/2\\/4 video coding applications. The proposed IP core exploits the parallel numerical matching in the MPEG-1\\/2\\/4 entropy decoding to achieve high data throughput rate in terms of limited hardware cost. This feature not only improves the performance of VLD, but also facilitates reducing the power consumption through

  13. A Variable Stability Test Vehicle for ITS Applications

    NASA Technical Reports Server (NTRS)

    Griffin, Daniel C.; Lee, Allan Y.

    1996-01-01

    A variable stability test bed is under development for the National Highway Traffic Safety Administration (NHTSA). The Variable Dynamic Testbed Vehicle (VDTV) is being designed for research and testing of advanced collision warning and avoidance technologies being developed by industry and most likely being made available to consumers in the near future.

  14. Variable Focusing Microlens Chip for Potential Sensing Applications

    Microsoft Academic Search

    Weisong Wang; Ji Fang

    2007-01-01

    A variable focusing microlens chip, which has the capability of adjusting its focal length over a wide range without any mechanical driving parts, is reported in this paper. The packaged microlens chip consists of a flexible polymer lens, a fluidic chamber, an integrated sensor, and an actuator. A thermal actuator is introduced into this variable focusing microlens to obtain relatively

  15. Effects of Posteroanterior Thoracic Mobilization on Heart Rate Variability and Pain in Women with Fibromyalgia

    PubMed Central

    Reis, Michel Silva; Durigan, João Luiz Quagliotti; Arena, Ross; Rossi, Bruno Rafael Orsini; Mendes, Renata Gonçalves; Borghi-Silva, Audrey

    2014-01-01

    Fibromyalgia (FM) has been associated with cardiac autonomic abnormalities and pain. Heart rate variability (HRV) is reduced in FM with autonomic tone dominated by sympathetic activity. The purpose of this study was to evaluate the effects of one session of a posteroanterior glide technique on both autonomic modulation and pain in woman with FM. This was a controlled trial with immediate followup; twenty premenopausal women were allocated into 2 groups: (i) women diagnosed with FM (n = 10) and (ii) healthy women (n = 10). Both groups received one session of Maitland mobilization grade III posteroanterior central pressure glide, at 2?Hz for 60?s at each vertebral segment. Autonomic modulation was assessed by HRV and pain by a numeric pain scale before and after the intervention. For HRV analyses, heart rate and RR intervals were recorded for 10 minutes. FM subjects demonstrated reduced HRV compared to controls. Although the mobilization technique did not significantly reduce pain, it was able to improve HRV quantified by an increase in rMSSD and SD1 indices, reflecting an improved autonomic profile through increased vagal activity. In conclusion, women with FM presented with impaired cardiac autonomic modulation. One session of Maitland spine mobilization was able to acutely improve HRV. PMID:24991436

  16. Analysis of heart rate variability during auditory stimulation periods in patients with schizophrenia.

    PubMed

    Akar, Saime Akdemir; Kara, Sad?k; Latifo?lu, Fatma; Bilgiç, Vedat

    2015-02-01

    The vulnerability-stress model is a hypothesis for symptom development in schizophrenia patients who are generally characterized by cardiac autonomic dysfunction. Therefore, measures of heart rate variability (HRV) have been widely used in schizophrenics for assessing altered cardiac autonomic regulations. The goal of this study was to analyze HRV of schizophrenia patients and healthy control subjects with exposure to auditory stimuli. More specifically, this study examines whether schizophrenia patients may exhibit distinctive time and frequency domain parameters of HRV from control subjects during at rest and auditory stimulation periods. Photoplethysmographic signals were used in the analysis of HRV. Nineteen schizophrenic patients and twenty healthy control subjects were examined during rest periods, while exposed to periods of white noise (WN) and relaxing music. Results indicate that HRV in patients was lower than that of control subjects indicating autonomic dysfunction throughout the entire experiment. In comparison with control subjects, patients with schizophrenia exhibited lower high-frequency power and a higher low-frequency to high-frequency ratio. Moreover, while WN stimulus decreased parasympathetic activity in healthy subjects, no significant changes in heart rate and frequency-domain HRV parameters were observed between the auditory stimulation and rest periods in schizophrenia patients. We can conclude that HRV can be used as a sensitive index of emotion-related sympathetic activity in schizophrenia patients. PMID:24831932

  17. Heart Rate Variability Monitoring during Sleep Based on Capacitively Coupled Textile Electrodes on a Bed

    PubMed Central

    Lee, Hong Ji; Hwang, Su Hwan; Yoon, Hee Nam; Lee, Won Kyu; Park, Kwang Suk

    2015-01-01

    In this study, we developed and tested a capacitively coupled electrocardiogram (ECG) measurement system using conductive textiles on a bed, for long-term healthcare monitoring. The system, which was designed to measure ECG in a bed with no constraints of sleep position and posture, included a foam layer to increase the contact region with the curvature of the body and a cover to ensure durability and easy installation. Nine healthy subjects participated in the experiment during polysomnography (PSG), and the heart rate (HR) coverage and heart rate variability (HRV) parameters were analyzed to evaluate the system. The experimental results showed that the mean of R-peak coverage was 98.0% (95.5%–99.7%), and the normalized errors of HRV time and spectral measures between the Ag/AgCl system and our system ranged from 0.15% to 4.20%. The root mean square errors for inter-beat (RR) intervals and HR were 1.36 ms and 0.09 bpm, respectively. We also showed the potential of our developed system for rapid eye movement (REM) sleep and wake detection as well as for recording of abnormal states. PMID:26007716

  18. The effect of hypoxia and exercise on heart rate variability, immune response, and orthostatic stress.

    PubMed

    Koelwyn, G J; Wong, L E; Kennedy, M D; Eves, N D

    2013-02-01

    Hypoxia with exercise is commonly used to enhance physiological adaptation in athletes, but may prolong recovery between training bouts. To investigate this, heart rate variability (HRV), systemic immune response, and response to an orthostatic challenge were measured following exercise in hypoxia and air. Eleven trained men performed a 10-km cycling time trial breathing hypoxia (16.5 ± 0.5% O(2)) or air. HRV and the heart rate response to an orthostatic challenge were measured for 3 days before and after each trial, while venous blood samples were collected pre-, 0, 2, and 24 h post-exercise. Hypoxia had no significant effect compared with air. Subgroup analysis of those who had a drop in oxyhemoglobin saturation (SpO(2)) > 10% between hypoxia and air compared with those who did not, demonstrated a significantly altered HRV response (?HFnu: -2.1 ± 0.9 vs 8.6 ± 9.3, ?LFnu: 2.1 ± 1.0 vs -8.6 ± 9.4) at 24 h post-exercise and increased circulating monocytes (1.3 ± 0.2 vs 0.8 ± 0.2 × 10(9) /L) immediately post-hypoxic exercise. Exercise and hypoxia did not change HRV or the systemic immune response to exercise. However, those who had a greater desaturation during hypoxic exercise had an attenuate recovery 24 h post-exercise and may be more susceptible to accumulating fatigue with subsequent training bouts. PMID:23013143

  19. Poincare plot of heart rate variability: an approach towards explaining the cardiovascular autonomic function in obesity.

    PubMed

    Muralikrishnan, Krishnan; Balasubramanian, Kabali; Ali, Sajjadh M Jawahar; Rao, Badanidiyur Vishwanatha

    2013-01-01

    Obesity has been shown to affect cardiovascular function. Heart rate variability (HRV) has been an accepted method of measuring cardiovascular autonomic function. The aim of the study is to evaluate the impact of obesity on HRV using Poincaré plot (POP) analysis. A finding of sympathovagal imbalance in pre-obese adults in respiratory sinus arrhythmia (RSA) could provide important diagnostic information about early subclinical autonomic dysfunction in obesity. Thirty one obese (BMI 26.84 +/- 2.47) adult males (25.42 +/- 7.86 years) were compared with 31 normal subjects (25.38 +/- 4.61 years). In all participants, anthropometric and blood pressure (BP) measurements were performed. After rest at supine position for 5 minutes, they were asked to do control deep breathing for 1 minute. HRV was measured in terms of POP analysis. Differences in Resting heart rate (RHR) (P < or = 0.025), Pulse pressure (PP) (P < or = 0.048), SD1 (P < or = 0.042) and SD2 (P < or = 0.039) of the POP between the two groups were significant. Correlation between Body mass index (BMI) and (PP) (p = 0.19); SD1 (p = 0.47) and SD2 (p = 0.39) of the POP were significant in obese groups. Obesity is related to sympathovagal imbalance characterized by depressed parasympathetic tone and increased sympathetic activity. Nonlinear methods like POP permit simple assessment of autonomic function, despite measuring different aspects of HRV. PMID:24020096

  20. Reduced heart rate variability during sleep in long-duration spaceflight.

    PubMed

    Xu, D; Shoemaker, J K; Blaber, A P; Arbeille, P; Fraser, K; Hughson, R L

    2013-07-15

    Limited data are available to describe the regulation of heart rate (HR) during sleep in spaceflight. Sleep provides a stable supine baseline during preflight Earth recordings for comparison of heart rate variability (HRV) over a wide range of frequencies using both linear, complexity, and fractal indicators. The current study investigated the effect of long-duration spaceflight on HR and HRV during sleep in seven astronauts aboard the International Space Station up to 6 mo. Measurements included electrocardiographic waveforms from Holter monitors and simultaneous movement records from accelerometers before, during, and after the flights. HR was unchanged inflight and elevated postflight [59.6 ± 8.9 beats per minute (bpm) compared with preflight 53.3 ± 7.3 bpm; P < 0.01]. Compared with preflight data, HRV indicators from both time domain and power spectral analysis methods were diminished inflight from ultralow to high frequencies and partially recovered to preflight levels after landing. During inflight and at postflight, complexity and fractal properties of HR were not different from preflight properties. Slow fluctuations (<0.04 Hz) in HR presented moderate correlations with movements during sleep, partially accounting for the reduction in HRV. In summary, substantial reduction in HRV was observed with linear, but not with complexity and fractal, methods of analysis. These results suggest that periodic elements that influence regulation of HR through reflex mechanisms are altered during sleep in spaceflight but that underlying system complexity and fractal dynamics were not altered. PMID:23637139

  1. Heart rate variability during carbachol-induced REM sleep and cataplexy.

    PubMed

    Torterolo, Pablo; Castro-Zaballa, Santiago; Cavelli, Matías; Velasquez, Noelia; Brando, Victoria; Falconi, Atilio; Chase, Michael H; Migliaro, Eduardo R

    2015-09-15

    The nucleus pontis oralis (NPO) exerts an executive control over REM sleep. Cholinergic input to the NPO is critical for REM sleep generation. In the cat, a single microinjection of carbachol (a cholinergic agonist) into the NPO produces either REM sleep (REMc) or wakefulness with muscle atonia (cataplexy, CA). In order to study the central control of the heart rate variability (HRV) during sleep, we conducted polysomnographic and electrocardiogram recordings from chronically prepared cats during REMc, CA as well as during sleep and wakefulness. Subsequently, we performed statistical and spectral analyses of the HRV. The heart rate was greater during CA compared to REMc, NREM or REM sleep. Spectral analysis revealed that the low frequency band (LF) power was significantly higher during REM sleep in comparison to REMc and CA. Furthermore, we found that during CA there was a decrease in coupling between the RR intervals plot (tachogram) and respiratory activity. In contrast, compared to natural behavioral states, during REMc and CA there were no significant differences in the HRV based upon the standard deviation of normal RR intervals (SDNN) and the mean squared difference of successive intervals (rMSSD). In conclusion, there were differences in the HRV during naturally-occurring REM sleep compared to REMc. In addition, in spite of the same muscle atonia, the HRV was different during REMc and CA. Therefore, the neuronal network that controls the HRV during REM sleep can be dissociated from the one that generates the muscle atonia during this state. PMID:25997581

  2. Synchronization analysis between heart rate variability and EEG activity before, during, and after epileptic seizure.

    PubMed

    Piper, Diana; Schiecke, Karin; Leistritz, Lutz; Pester, Britta; Benninger, Franz; Feucht, Martha; Ungureanu, Mihaela; Strungaru, Rodica; Witte, Herbert

    2014-08-01

    Abstract An innovative concept for synchronization analysis between heart rate (HR) components and rhythms in EEG envelopes is represented; it applies time-variant analyses to heart rate variability (HRV) and EEG, and it was tested in children with temporal lobe epilepsy (TLE). After a removal of ocular and movement-related artifacts, EEG band activity was computed by means of the frequency-selective Hilbert transform providing envelopes of frequency bands. Synchronization between HRV and EEG envelopes was quantified by Morlet wavelet coherence. A surrogate data approach was adapted to test for statistical significance of time-variant coherences. Using this processing scheme, significant coherence values between a HRV low-frequency sub-band (0.08-0.12 Hz) and the EEG ? envelope (1.5-4 Hz) occurring both in the preictal and early postictal periods of a seizure can be shown. Investigations were performed for all electrodes at 20-s intervals and for selected electrode pairs (T3÷C3, T4÷C4) in a time-variant mode. Synchronization was more pronounced in the group of right hemispheric TLE patients than in the left hemispheric group. Such a group-specific augmentation of synchronization confirms the hypothesis of a right hemispheric lateralization of sympathetic cardiac control of the low-frequency HRV components. PMID:24695024

  3. Heart Rate Variability in Overweight Health Care Students: Correlation with Visceral Fat

    PubMed Central

    Krishna, Bandi Hari; N, Mallikarjuna Reddy

    2015-01-01

    Background and Objectives: Increased sympathetic activity, decreased parasympathetic activity and sympathovagal imbalance (SVI) has been reported in obese individuals. However, the SVI and its association with visceral fat in overweight health care students have not been explored. Therefore, in the present study, we have assessed heart rate variability (HRV) and its association with visceral fat in overweight health care students. Materials and Methods: Frequency domain parameters of HRV, body fat distribution and baseline anthropometric parameters were recorded in the control (n=40) and overweight (n=40) individuals. Further, the association of visceral fat with HRV was analysed. Results: There was no significant difference in age and height of overweight group and control group (p = 0.732). The baseline heart rate and blood pressure (p<0.001) were higher in the overweight group. Total body fat, subcutaneous fat and visceral fat were higher in the overweight group (p<0.001). Among frequency domain parameter of HRV, LFnu and LF: HF were more in the overweight group (p<0.001). Further, HFnu was less in the overweight group (p<0.001). Conclusion: Sympathovagal imbalance due to increased sympathetic activity and its association with visceral fat was observed in overweight individuals. PMID:25737980

  4. Effect of Rotating Acoustic Stimulus on Heart Rate Variability in Healthy Adults

    PubMed Central

    Roy, Bhaskar; Choudhuri, Raghabendra; Pandey, Ambarish; Bandopadhyay, Sajal; Sarangi, Sasmit; Kumar Ghatak, Sobhendu

    2012-01-01

    Acoustic stimulus can modulate the Autonomic Nervous System. However, previous reports on this topic are conflicting and inconclusive. In this study we have shown, how rotating acoustic stimulus, a novel auditory binaural stimulus, can change the autonomic balance of the cardiac system. We have used Heart rate Variability (HRV), an indicator of autonomic modulation of heart, both in time and frequency domain to analyze the effect of stimulus on 31 healthy adults. A decrease in the heart rate accompanied with an increase in SD and RMSSD indices on linear analysis was observed post-stimulation. In the Poincaré Plot, Minor Axis (SD1), Major Axis (SD2) and the ratio SD12 (SD1/SD2) increased after the stimulation. Post stimulus greater increment of SD12 with higher lag numbers of (M) beat to beat intervals, when compared to pre stimulus values, resulted in increased curvilinearity in the SD12 vs. Lag number plot. After stimulation,value of exponent alpha of Dretended Flactuation Analysis of HRV was found to be decreased. From these characteristic responses of the heart after the stimulus, it appears that rotating acoustic stimulus may be beneficial for the sympathovagal balance of the heart. PMID:23091566

  5. Heart Rate Variability Monitoring during Sleep Based on Capacitively Coupled Textile Electrodes on a Bed.

    PubMed

    Lee, Hong Ji; Hwang, Su Hwan; Yoon, Hee Nam; Lee, Won Kyu; Park, Kwang Suk

    2015-01-01

    In this study, we developed and tested a capacitively coupled electrocardiogram (ECG) measurement system using conductive textiles on a bed, for long-term healthcare monitoring. The system, which was designed to measure ECG in a bed with no constraints of sleep position and posture, included a foam layer to increase the contact region with the curvature of the body and a cover to ensure durability and easy installation. Nine healthy subjects participated in the experiment during polysomnography (PSG), and the heart rate (HR) coverage and heart rate variability (HRV) parameters were analyzed to evaluate the system. The experimental results showed that the mean of R-peak coverage was 98.0% (95.5%-99.7%), and the normalized errors of HRV time and spectral measures between the Ag/AgCl system and our system ranged from 0.15% to 4.20%. The root mean square errors for inter-beat (RR) intervals and HR were 1.36 ms and 0.09 bpm, respectively. We also showed the potential of our developed system for rapid eye movement (REM) sleep and wake detection as well as for recording of abnormal states. PMID:26007716

  6. Intracardiac Origin of Heart Rate Variability, Pacemaker Funny Current and their Possible Association with Critical Illness

    PubMed Central

    Papaioannou, Vasilios E; Verkerk, Arie O; Amin, Ahmed S; de Bakker, Jaques MT

    2013-01-01

    Heart rate variability (HRV) is an indirect estimator of autonomic modulation of heart rate and is considered a risk marker in critical illness, particularly in heart failure and severe sepsis. A reduced HRV has been found in critically ill patients and has been associated with neuro-autonomic uncoupling or decreased baroreflex sensitivity. However, results from human and animal experimental studies indicate that intracardiac mechanisms might also be responsible for interbeat fluctuations. These studies have demonstrated that different membrane channel proteins and especially the so-called ‘funny’ current (If), an hyperpolarization-activated, inward current that drives diastolic depolarization resulting in spontaneous activity in cardiac pacemaker cells, are altered during critical illness. Furthermore, membrane channels kinetics seem to have significant impact upon HRV, whose early decrease might reflect a cellular metabolic stress. In this review article we present research findings regarding intracardiac origin of HRV, at the cellular level and in both isolated sinoatrial node and whole ex vivo heart preparations. In addition, we will review results from various experimental studies that support the interrelation between If and HRV during endotoxemia. We suggest that reduced HRV during sepsis could also be associated with altered pacemaker cell membrane properties, due to ionic current remodeling. PMID:22920474

  7. Effect of two selected yogic breathing techniques of heart rate variability.

    PubMed

    Raghuraj, P; Ramakrishnan, A G; Nagendra, H R; Telles, S

    1998-10-01

    The heart rate variability (HRV) is an indicator of the cardiac autonomic control. Two spectral components are usually recorded, viz. high frequency (0.15-0.50 Hz), which is due to vagal efferent activity and a low frequency component (0.05-0.15 Hz), due to sympathetic activity. The present study was conducted to study the HRV in two yoga practices which have been previously reported to have opposite effects, viz, sympathetic stimulation (kapalabhati, breathing at high frequency, i.e., 2.0 Hz) and reduced sympathetic activity (nadisuddhi, alternate nostril breathing). Twelve male volunteers (age range, 21 to 33 years) were assessed before and after each practice on separate days. The electrocardiogram (lead I) was digitized on-line and off-line analysis was done. The results showed a significant increase in low frequency (LF) power and LF/HF ratio while high frequency (HF) power was significantly lower following kapalabhati. There were no significant changes following nadisuddhi. The results suggest that kapalabhati modifies the autonomic status by increasing sympathetic activity with reduced vagal activity. The study also suggests that HRV is a more useful psychophysiological measure than heart rate alone. PMID:10874345

  8. Heart rate variability during sleep following the practice of cyclic meditation and supine rest.

    PubMed

    Patra, Sanjib; Telles, Shirley

    2010-06-01

    Day time activities are known to influence the sleep on the following night. Cyclic meditation (CM) has recurring cycles. Previously, the low frequency (LF) power and the ratio between low frequency and high frequency (LF/HF ratio) of the heart rate variability (HRV) decreased during and after CM but not after a comparable period of supine rest (SR). In the present study, on thirty male volunteers, CM was practiced twice in the day and after this the HRV was recorded (1) while awake and (2) during 6 h of sleep (based on EEG, EMG and EGG recordings). This was similarly recorded for the night's sleep following the day time practice of SR. Participants were randomly assigned to the two sessions and all of them practiced both CM and SR on different days. During the night following day time CM practice there were the following changes; a decrease in heart rate, LF power (n.u.), LF/HF ratio, and an increase in the number of pairs of Normal to Normal RR intervals differing by more than 50 ms divided by total number of all NN intervals (pNN50) (P < 0.05, in all cases, comparing sleep following CM compared with sleep following SR). No change was seen on the night following SR. Hence yoga practice during the day appears to shift sympatho-vagal balance in favor of parasympathetic dominance during sleep on the following night. PMID:19838801

  9. Mass loss rates of a sample of irregular and semiregular M-type AGB-variables

    NASA Astrophysics Data System (ADS)

    Olofsson, H.; González Delgado, D.; Kerschbaum, F.; Schöier, F. L.

    2002-09-01

    We have determined mass loss rates and gas expansion velocities for a sample of 69 M-type irregular (IRV 22 objects) and semiregular (SRV; 47 objects) AGB-variables using a radiative transfer code to model their circumstellar CO radio line emission. We believe that this sample is representative for the mass losing stars of this type. The (molecular hydrogen) mass loss rate distribution has a median value of 2.0 x 10-7 Msun yr-1, and a minimum of 2.0 x 10-8 Msun yr-1 and a maximum of 8 x 10-7 Msun yr-1. M-type IRVs and SRVs with a mass loss rate in excess of 5 x 10-7 Msun yr-1 must be very rare, and among these mass losing stars the number of sources with mass loss rates below a few 10-8 Msun yr-1 must be small. We find no significant difference between the IRVs and the SRVs in terms of their mass loss characteristics. Among the SRVs the mass loss rate shows no dependence on the period. Likewise the mass loss rate shows no correlation with the stellar temperature. The gas expansion velocity distribution has a median of 7.0 km s-1, and a minimum of 2.2 km s-1 and a maximum of 14.4 km s-1. No doubt, these objects sample the low gas expansion velocity end of AGB winds. The fraction of objects with low gas expansion velocities is very high, about 30% have velocities lower than 5 km s-1, and there are objects with velocities lower than 3 km s-1: V584 Aql, T Ari, BI Car, RX Lac, and L2 Pup. The mass loss rate and the gas expansion velocity correlate well, a result in line with theoretical predictions for an optically thin, dust-driven wind. In general, the model produces line profiles which acceptably fit the observed ones. An exceptional case is R Dor, where the high-quality, observed line profiles are essentially flat-topped, while the model ones are sharply double-peaked. The sample contains four sources with distinctly double-component CO line profiles, i.e., a narrow feature centered on a broader feature: EP Aqr, RV Boo, X Her, and SV Psc. We have modelled the two components separately for each star and derive mass loss rates and gas expansion velocities. We have compared the results of this M-star sample with a similar C-star sample analysed in the same way. The mass loss rate characteristics are very similar for the two samples. On the contrary, the gas expansion velocity distributions are clearly different. In particular, the number of low-velocity sources is much higher in the M-star sample. We found no example of the sharply double-peaked CO line profile, which is evidence of a large, detached CO-shell, among the M-stars. About 10% of the C-stars show this phenomenon.

  10. Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

    PubMed Central

    Cunha, F.A.; Montenegro, R.A.; Midgley, A.W.; Vasconcellos, F.; Soares, P.P.; Farinatti, P.

    2014-01-01

    The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve (%V?O2?R) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and V?O2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg-1·min-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and %V?O2?R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and %V?O2?R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise. PMID:25003546

  11. Spectral analysis of heart rate variability during asleep-awake craniotomy for tumor resection.

    PubMed

    Conte, Valeria; Guzzetti, Stefano; Porta, Alberto; Tobaldini, Eleonora; Baratta, Pietro; Bello, Lorenzo; Stocchetti, Nino

    2009-07-01

    Anesthesia during asleep-awake craniotomy should provide adequate analgesia and sedation whereas permitting language testing. In this work, we used the analysis of heart rate variability (HRV) to quantify the sympatho-vagal balance and better evaluate patient's stress response during asleep-awake craniotomy. Patients admitted to our hospital for tumor resection with language testing were studied (n=21, age range: 22 to 53 y ). Heart rate and systolic arterial blood pressure were collected at 5 time points: T1: preanesthesia; T2: dura mater opening; T3: cortical mapping; T4: subcortical mapping; T5: dura mater suturing. Patients were anesthetized with propofol/remifentanil infusion and ventilated via laryngeal mask during T2, but were awakened for language testing at T3 and T4, and resedated with remifentanil during T5. At each time point, HRV was analyzed by power spectrum analysis: overall variance, very low frequency (VLF), low frequency (LF) and high frequency (HF) powers, and LF/HF ratio (an index of prevalence of sympathetic over parasympathetic tone) were derived. A significant increase in both heart rate and systolic arterial blood pressure was observed from time point T3 through T5 (P<0.05, compared with T1). HRV analysis revealed that the LF/HF ratio progressively increased to reach values during T4 that were significantly higher than preanesthesia values (P<0.05). During T5, LF/HF ratio returned to preanesthesia level. HRV analysis confirmed the presence of moderate intraoperative stress response, indicating a significant increase in the LF/HF ratio during the awake phases. This information might help in tailoring the protocol and the duration of awake phase according to the individual autonomic response. PMID:19543003

  12. AKAP10 (I646V) functional polymorphism predicts heart rate and heart rate variability in apparently healthy, middle-aged European-Americans

    Microsoft Academic Search

    Serina A. Neumann; Whittemore G. Tingley; Bruce R. Conklin; Catherine J. Shrader; Eloise Peet; Matthew F. Muldoon; J. Richard Jennings; Robert E. Ferrell; STEPHEN B. MANUCKc

    2009-01-01

    Previous evidence suggests that the dual-specific A kinase-anchoring protein 2 functional polymorphism (AKAP10 (A\\/G) I646V) influences heart rate (HR) and heart rate variability (HRV) in mice and humans (N 5 122) with cardiovascular disease. Here, we asked whether this AKAP10 variant predicts HR and HRV in a large sample of healthy humans. Resting HR and short-term time and frequency domain

  13. Association of heart rate variability and inflammatory response in patients with cardiovascular diseases: current strengths and limitations

    PubMed Central

    Papaioannou, Vasilios; Pneumatikos, Ioannis; Maglaveras, Nikos

    2013-01-01

    Many experimental and clinical studies have confirmed a continuous cross-talk between both sympathetic and parasympathetic branches of autonomic nervous system and inflammatory response, in different clinical scenarios. In cardiovascular diseases, inflammation has been proven to play a pivotal role in disease progression, pathogenesis and resolution. A few clinical studies have assessed the possible inter-relation between neuro-autonomic output, estimated with heart rate variability analysis, which is the variability of R-R in the electrocardiogram, and different inflammatory biomarkers, in patients suffering from stable or unstable coronary artery disease (CAD) and heart failure. Moreover, different indices derived from heart rate signals' processing, have been proven to correlate strongly with severity of heart disease and predict final outcome. In this review article we will summarize major findings from different investigators, evaluating neuro-immunological interactions through heart rate variability analysis, in different groups of cardiovascular patients. We suggest that markers originating from variability analysis of heart rate signals seem to be related to inflammatory biomarkers. However, a lot of open questions remain to be addressed, regarding the existence of a true association between heart rate variability and autonomic nervous system output or its adoption for risk stratification and therapeutic monitoring at the bedside. Finally, potential therapeutic implications will be discussed, leading to autonomic balance restoration in relation with inflammatory control. PMID:23847549

  14. The Effects of Thoracic Sympathotomy on Heart Rate Variability in Patients with Palmar Hyperhidrosis

    PubMed Central

    Zhang, Tong-yuan; Xu, Jin-jin

    2012-01-01

    Purpose To observe the evolution of heart rate variability (HRV) in patients with palmar hyperhidrosis before and after endoscopic thoracic sympathotomy and to evaluate the effects of the surgery on the autonomic nervous system. Materials and Methods Endoscopic thoracic sympathotomy was performed on 20 patients with palmar hyperhidrosis. The thoracic sympathetic chain at the level of the third to fourth rib (R3-R4) was transected, but the ganglia were left in position without removal. A slightly larger ramus, in comparison to the other rami, that arose laterally from the sympathetic chain was interrupted to achieve adequate sympathetic denervation of the upper extremity. Before and on the day after the surgery, 24-hour Holter Electrocardiograph was performed, obtaining time domain and frequency domain parameters. Results Compared with preoperative variables, there was a significant increase in the number of adjacent normal R wave to R wave (R-R) intervals that differed by more than 50 ms, as percent of the total number of normal RR intervals (pNN50); root mean square difference, the square root of the mean of the sum of squared differences between adjacent normal RR intervals over the entire 24-hour recording; standard deviation of the average normal RR interval for all 5-minute segments of a 24-hour recording (SDANN) after thoracic sympathotomy. Low frequencies (LF, 0.04 to 0.15 Hz) decreased significantly. There was no statistical difference in high frequencies (HF, 0.15 to 0.40 Hz), LF/HF ratio (LF/HF), or standard deviation for all normal RR intervals for the entire 24-h recording (SDNN) before and after thoracic sympathotomy. Conclusion There was a significant improvement in HRV in patients with palmar hyperhidrosis after thoracic sympathotomy. This may be attributable to an improvement autonomic nervous system balance and parasympathetic predominance in the early postoperative stage. PMID:23074105

  15. Heart rate variability and cardio-respiratory coupling during sleep in patients prior to bariatric surgery.

    PubMed

    Trimer, R; Cabiddu, R; Mendes, R G; Costa, F S M; Oliveira, A D; Borghi-Silva, A; Bianchi, A M

    2014-03-01

    Obesity is associated with increased cardiac risk of morbidly and mortality and for the development and progression of obstructive sleep apnea (OSA). Severity of obesity negatively affects the heart rate variability (HRV) in patients with indication for bariatric surgery (BS). The purpose of this study is to determine if the severity of obesity alters the autonomic cardiac regulation and the cardio-respiratory coupling during sleep using spectral analysis of HRV and respiration variability signals (RS) in patients prior to BS. Twenty-nine consecutive preoperative BS and ten subjects (controls) underwent polysomnography. The spectral and cross-spectral parameters of the HRV and RS were computed during different sleep stages (SS). Spectral analysis of the HRV and RV indicated lower respiration regularity during sleep and a lower HRV in obese patients (OP) during all SS when compared with controls (p < 0.05). Severely (SO) and super-obese patients (SOP) presented lower values of low frequency/high frequency (LF/HF) ratio and LF power during REM sleep and higher HF power (p < 0.05), while morbidly obese (MO) patients presented lower LF/HF ratio and LF power in SS-S2 and higher HF power when compared to controls (p < 0.05). The cross-spectral parameters showed that SOP presented lower percentage of tachogram power coherent with respiration in SS-S3 when compared to controls (p < 0.05). Patients prior to BS presented altered HRV and RV in all SS. SO, MO, and SOP presented altered cardio-respiratory coupling during sleep, and these alterations are related with severity of obesity and OSA parameters. PMID:24395186

  16. Effects of aerobic training intensity on resting, exercise and post-exercise blood pressure, heart rate and heart-rate variability

    Microsoft Academic Search

    V A Cornelissen; B Verheyden; A E Aubert; R H Fagard

    2010-01-01

    We aimed to investigate the effects of endurance training intensity (1) on systolic blood pressure (SBP) and heart rate (HR) at rest before exercise, and during and after a maximal exercise test; and (2) on measures of HR variability at rest before exercise and during recovery from the exercise test, in at least 55-year-old healthy sedentary men and women. A

  17. ACTIVE LEARNING TO OVERCOME SAMPLE SELECTION BIAS: APPLICATION TO PHOTOMETRIC VARIABLE STAR CLASSIFICATION

    SciTech Connect

    Richards, Joseph W.; Starr, Dan L.; Miller, Adam A.; Bloom, Joshua S.; Butler, Nathaniel R.; Berian James, J. [Astronomy Department, University of California, Berkeley, CA 94720-7450 (United States); Brink, Henrik [Dark Cosmology Centre, Juliane Maries Vej 30, 2100 Copenhagen O (Denmark); Long, James P.; Rice, John, E-mail: jwrichar@stat.berkeley.edu [Statistics Department, University of California, Berkeley, CA 94720-7450 (United States)

    2012-01-10

    Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest as strongly biased predictions on the data of interest. Typically, training sets are derived from historical surveys of brighter, more nearby objects than those from more extensive, deeper surveys (testing data). This sample selection bias can cause catastrophic errors in predictions on the testing data because (1) standard assumptions for machine-learned model selection procedures break down and (2) dense regions of testing space might be completely devoid of training data. We explore possible remedies to sample selection bias, including importance weighting, co-training, and active learning (AL). We argue that AL-where the data whose inclusion in the training set would most improve predictions on the testing set are queried for manual follow-up-is an effective approach and is appropriate for many astronomical applications. For a variable star classification problem on a well-studied set of stars from Hipparcos and Optical Gravitational Lensing Experiment, AL is the optimal method in terms of error rate on the testing data, beating the off-the-shelf classifier by 3.4% and the other proposed methods by at least 3.0%. To aid with manual labeling of variable stars, we developed a Web interface which allows for easy light curve visualization and querying of external databases. Finally, we apply AL to classify variable stars in the All Sky Automated Survey, finding dramatic improvement in our agreement with the ASAS Catalog of Variable Stars, from 65.5% to 79.5%, and a significant increase in the classifier's average confidence for the testing set, from 14.6% to 42.9%, after a few AL iterations.

  18. Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star Classification

    NASA Astrophysics Data System (ADS)

    Richards, Joseph W.; Starr, Dan L.; Brink, Henrik; Miller, Adam A.; Bloom, Joshua S.; Butler, Nathaniel R.; James, J. Berian; Long, James P.; Rice, John

    2012-01-01

    Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest as strongly biased predictions on the data of interest. Typically, training sets are derived from historical surveys of brighter, more nearby objects than those from more extensive, deeper surveys (testing data). This sample selection bias can cause catastrophic errors in predictions on the testing data because (1) standard assumptions for machine-learned model selection procedures break down and (2) dense regions of testing space might be completely devoid of training data. We explore possible remedies to sample selection bias, including importance weighting, co-training, and active learning (AL). We argue that AL—where the data whose inclusion in the training set would most improve predictions on the testing set are queried for manual follow-up—is an effective approach and is appropriate for many astronomical applications. For a variable star classification problem on a well-studied set of stars from Hipparcos and Optical Gravitational Lensing Experiment, AL is the optimal method in terms of error rate on the testing data, beating the off-the-shelf classifier by 3.4% and the other proposed methods by at least 3.0%. To aid with manual labeling of variable stars, we developed a Web interface which allows for easy light curve visualization and querying of external databases. Finally, we apply AL to classify variable stars in the All Sky Automated Survey, finding dramatic improvement in our agreement with the ASAS Catalog of Variable Stars, from 65.5% to 79.5%, and a significant increase in the classifier's average confidence for the testing set, from 14.6% to 42.9%, after a few AL iterations.

  19. Selection of entropy-measure parameters for knowledge discovery in heart rate variability data

    PubMed Central

    2014-01-01

    Background Heart rate variability is the variation of the time interval between consecutive heartbeats. Entropy is a commonly used tool to describe the regularity of data sets. Entropy functions are defined using multiple parameters, the selection of which is controversial and depends on the intended purpose. This study describes the results of tests conducted to support parameter selection, towards the goal of enabling further biomarker discovery. Methods This study deals with approximate, sample, fuzzy, and fuzzy measure entropies. All data were obtained from PhysioNet, a free-access, on-line archive of physiological signals, and represent various medical conditions. Five tests were defined and conducted to examine the influence of: varying the threshold value r (as multiples of the sample standard deviation ?, or the entropy-maximizing rChon), the data length N, the weighting factors n for fuzzy and fuzzy measure entropies, and the thresholds rF and rL for fuzzy measure entropy. The results were tested for normality using Lilliefors' composite goodness-of-fit test. Consequently, the p-value was calculated with either a two sample t-test or a Wilcoxon rank sum test. Results The first test shows a cross-over of entropy values with regard to a change of r. Thus, a clear statement that a higher entropy corresponds to a high irregularity is not possible, but is rather an indicator of differences in regularity. N should be at least 200 data points for r = 0.2 ? and should even exceed a length of 1000 for r = rChon. The results for the weighting parameters n for the fuzzy membership function show different behavior when coupled with different r values, therefore the weighting parameters have been chosen independently for the different threshold values. The tests concerning rF and rL showed that there is no optimal choice, but r = rF = rL is reasonable with r = rChon or r = 0.2?. Conclusions Some of the tests showed a dependency of the test significance on the data at hand. Nevertheless, as the medical conditions are unknown beforehand, compromises had to be made. Optimal parameter combinations are suggested for the methods considered. Yet, due to the high number of potential parameter combinations, further investigations of entropy for heart rate variability data will be necessary. PMID:25078574

  20. Do Bells Affect Behaviour and Heart Rate Variability in Grazing Dairy Cows?

    PubMed Central

    Johns, Julia; Patt, Antonia; Hillmann, Edna

    2015-01-01

    In alpine regions cows are often equipped with bells. The present study investigated the impact of wearing a bell on behaviour and heart rate variability in dairy cows. Nineteen non-lactating Brown-Swiss cows with bell experience were assigned to three different treatments. For 3 days each, cows were equipped with no bell (control), with a bell with inactivated clapper (silent bell) or with a functional bell (functional bell). The bells weighed 5.5 kg and had frequencies between 532 Hz and 2.8 kHz and amplitudes between 90 and 113 dB at a distance of 20 cm. Data were collected on either the first and third or on all 3 days of each treatment. Whereas duration of rumination was reduced with a functional bell and a silent bell compared with no bell, feeding duration was reduced with a silent bell and was intermediate with a functional bell. Head movements were reduced when wearing a silent bell compared with no bell and tended to be reduced when wearing a functional compared to no bell. With a functional bell, lying duration was reduced by almost 4 hours on the third day of treatment compared with the first day with a functional bell and compared with no bell or a silent bell. All additional behavioural measures are consistent with the hypothesis of a restriction in the behaviour of the cows wearing bells, although this pattern did not reach significance. There was no treatment effect on heart rate variability, suggesting that the bells did not affect vago-sympathetic balance. An effect of experimental day was found for only 1 out of 10 behavioural parameters, as shown by a decrease in lying with a functional bell on day 3. The results indicate behavioural changes in the cows wearing a bell over 3 days, without indication of habituation to the bell. Altogether, the behavioural changes suggest that the behaviour of the cows was disturbed by wearing a bell. If long-lasting, these effects may have implications for animal welfare. PMID:26110277

  1. Attentional Focus and Performance Anxiety: Effects on Simulated Race-Driving Performance and Heart Rate Variability

    PubMed Central

    Mullen, Richard; Faull, Andrea; Jones, Eleri S.; Kingston, Kieran

    2012-01-01

    Previous studies have demonstrated that an external focus can enhance motor learning compared to an internal focus. The benefits of adopting an external focus are attributed to the use of less effortful automatic control processes, while an internal focus relies upon more effort-intensive consciously controlled processes. The aim of this study was to compare the effectiveness of a distal external focus with an internal focus in the acquisition of a simulated driving task and subsequent performance in a competitive condition designed to increase state anxiety. To provide further evidence for the automatic nature of externally controlled movements, the study included heart rate variability (HRV) as an index of mental effort. Sixteen participants completed eight blocks of four laps in either a distal external or internal focus condition, followed by two blocks of four laps in the competitive condition. During acquisition, the performance of both groups improved; however, the distal external focus group outperformed the internal focus group. The poorer performance of the internal focus group was accompanied by a larger reduction in HRV, indicating a greater investment of mental effort. In the competition condition, state anxiety increased, and for both groups, performance improved as a function of the increased anxiety. Increased heart rate and self-reported mental effort accompanied the performance improvement. The distal external focus group also outperformed the internal focus group across both neutral and competitive conditions and this more effective performance was again associated with lower levels of HRV. Overall, the results offer support for the suggestion that an external focus promotes a more automatic mode of functioning. In the competitive condition, both foci enhanced performance and while the improved performance may have been achieved at the expense of greater compensatory mental effort, this was not reflected in HRV scores. PMID:23133431

  2. Supine Low Frequency Power of Heart Rate Variability Reflects Baroreflex Function, Not Cardiac Sympathetic Innervation

    PubMed Central

    Moak, Jeffrey P.; Goldstein, David S.; Eldadah, Basil A.; Saleem, Ahmed; Holmes, Courtney; Pechnik, Sandra; Sharabi, Yehonatan

    2008-01-01

    Background Power spectral analysis of heart rate variability (HRV) has been used to indicate cardiac autonomic function. High-frequency power relates to respiratory sinus arrhythmia and therefore to parasympathetic cardiovagal tone; however, the relationship of low-frequency (LF) power to cardiac sympathetic innervation and function has been controversial. Alternatively, LF power might reflect baroreflexive modulation of autonomic outflows. Objective We studied normal volunteers and chronic autonomic failure syndrome patients with and without loss of cardiac noradrenergic nerves in order to examine the relationships of LF power with cardiac sympathetic innervation and baroreflex function. Methods We compared LF power of HRV in patients with cardiac sympathetic denervation, as indicated by low myocardial concentrations of 6-[18F] fluorodopamine-derived radioactivity or low rates of norepinephrine entry into coronary sinus plasma (cardiac norepinephrine spillover) to values in patients with intact innervation, at baseline, during infusion of yohimbine, which increases exocytotic norepinephrine release from sympathetic nerves, or during infusion of tyramine, which increases non-exocytotic release. Baroreflex-cardiovagal slope (BRS) was calculated from the cardiac interbeat interval and systolic pressure during the Valsalva maneuver. Results LF power was unrelated to myocardial 6-[18F] fluorodopamine-derived radioactivity or cardiac norepinephrine spillover. In contrast, the log of LF power correlated positively with the log of BRS (r=0.72, p<0.0001). Patients with low BRS (? 3 msec/mm Hg) had low LF power, regardless of cardiac innervation. Tyramine and yohimbine increased LF power in subjects with normal BRS but not in those with low BRS. BRS at baseline predicted LF responses to tyramine and yohimbine. Conclusions LF power reflects baroreflex function, not cardiac sympathetic innervation. PMID:17997358

  3. Fetal electrocardiographic measurements in the assessment of fetal heart rate variability in the antepartum period.

    PubMed

    Van Leeuwen, Peter; Werner, Lisa; Hilal, Ziad; Schiermeier, Sven; Hatzmann, Wolfgang; Grönemeyer, Dietrich

    2014-03-01

    This study examines signal availability in fetal electrocardiogram (FECG) beat-to-beat acquisition and the accuracy of fetal heart rate variability (HRV) analysis in the clinical setting using a commercially available FECG monitor. Signal availability was examined in 130 FECG recordings of 0.3-17.5 h duration collected in 63 fetuses (25th-42nd week of gestation) under uncontrolled conditions. Identification of R-peaks demonstrated a signal loss of 30% ± 24% with 3.6 ± 1.7 signal gaps per minute. Median duration of the gaps within a recording was 1.8 ± 0.2 s. Per hour of recording, 1.8 ± 2.1 episodes of 5 min of uninterrupted data were found. Signal availability improved with gestational age and was poorer in women with high body-mass index. Fetal HRV between weeks 36-42 was examined on the basis of 5 min RR-interval episodes obtained under controlled quiet conditions in 55 FECG compared to 46 high quality fetal magnetocardiograms. There were no differences in RR-interval duration, its standard deviation and low frequency power. However, various measures of short-term HRV were significantly higher in the FECG data: root mean square of successive differences (10.0 ± 1.8 versus 6.6 ± 3.0 ms, p < 0.001, high frequency spectral power (24 ± 12 versus 13 ± 13 ms(2), p < 0.001) and approximate entropy (0.86 ± 0.16 versus 0.73 ± 0.24, p = 0.007). We conclude that, in spite of considerable signal loss, FECG recordings can accurately estimate heart rate and its overall variance. However, measures that quantify short-term beat-to-beat HRV will be compromised due to possible recurring inappropriate detection of single R-peaks. PMID:24556971

  4. Compression of SAR raw data through range focusing and variable-rate trellis-coded quantization.

    PubMed

    D'Elia, C; Poggi, G; Verdoliva, L

    2001-01-01

    There is an ever-growing interest in the compression of SAR data because of the huge resources required for storage and transmission. This is especially true for spaceborne sensors, given the limited capacity of the downlink channel. Unfortunately, SAR data lack the useful properties on which compression algorithms rely; indeed, these are present in the focused images, but focusing is too complex for on-board implementation at this time. Poggi et al. (2000) proposed to perform on the satellite only the low-complexity range focusing, which increases the data correlation and better concentrates their energy. These properties were then exploited by adopting a variable-rate vector quantizer, with a clear performance improvement with respect to reference techniques. However, vector quantization (VQ) is too complex for actual on-board implementation, and therefore, here we replace VQ with trellis-coded VQ. To limit complexity, only small vectors are used, which reduces VQ's ability to exploit data dependencies; on the other hand, trellis coding allows one to encode large blocks of data at once, and to obtain a better partition of the input space. Experiments on real SAR data show that the overall performance is comparable to that of Poggi et al., but the complexity is much lower, making on-board implementation possible. PMID:18255543

  5. Hemodynamic performance of the biventricular bypass system operated in an independent variable rate mode.

    PubMed

    Ishino, K; Murakami, T; Irie, H; Nakayama, H; Izumoto, H; Yamada, M; Teraoka, H; Senoo, Y; Teramoto, S

    1992-10-01

    The present study was undertaken to determine whether a biventricular bypass system operated in an independent variable rate (VR) mode can maintain the entire circulation. Two pusher-plate pumps which incorporated the Hall effect position sensors were used to bypass the right and left ventricles in 10 sheep under fibrillation. The flow distributions of the pump output to the carotid and renal arteries were investigated every 6 h using ultrasonic blood flow meters for 24 h in 5 animals, and the controllability of the VR mode was evaluated in 5 long-term experiments. The carotid artery flow ratio to the pump output decreased significantly from 4.7 +/- 0.8% before the bypass to 2.7 +/- 0.9% after 24 h. However, the renal artery flow ratio did not change throughout the experiments. In the long-term experiments, the animals were kept alive from 3 to 48 days (mean 15.6 days). The mean pump output had been maintained at more than 90 ml/min/kg for the first 7 days. After the surgery, the pump driving conditions were not readjusted in any experiment. The results indicate that the biventricular bypass system operated in the independent VR mode automatically maintains the entire circulation at a satisfactory level. PMID:1442154

  6. An Efficient Biometric-Based Algorithm Using Heart Rate Variability for Securing Body Sensor Networks.

    PubMed

    Pirbhulal, Sandeep; Zhang, Heye; Mukhopadhyay, Subhas Chandra; Li, Chunyue; Wang, Yumei; Li, Guanglin; Wu, Wanqing; Zhang, Yuan-Ting

    2015-01-01

    Body Sensor Network (BSN) is a network of several associated sensor nodes on, inside or around the human body to monitor vital signals, such as, Electroencephalogram (EEG), Photoplethysmography (PPG), Electrocardiogram (ECG), etc. Each sensor node in BSN delivers major information; therefore, it is very significant to provide data confidentiality and security. All existing approaches to secure BSN are based on complex cryptographic key generation procedures, which not only demands high resource utilization and computation time, but also consumes large amount of energy, power and memory during data transmission. However, it is indispensable to put forward energy efficient and computationally less complex authentication technique for BSN. In this paper, a novel biometric-based algorithm is proposed, which utilizes Heart Rate Variability (HRV) for simple key generation process to secure BSN. Our proposed algorithm is compared with three data authentication techniques, namely Physiological Signal based Key Agreement (PSKA), Data Encryption Standard (DES) and Rivest Shamir Adleman (RSA). Simulation is performed in Matlab and results suggest that proposed algorithm is quite efficient in terms of transmission time utilization, average remaining energy and total power consumption. PMID:26131666

  7. Heart rate variability and mortality in patients with end stage renal disease.

    PubMed

    Cashion, Ann K; Holmes, Sandra L; Arheart, Kristopher L; Acchiardo, Sergio R; Hathaway, Donna K

    2005-01-01

    Heart rate variability (HRV), a measure of autonomic function, is associated with mortality in non-end stage renal disease (ESRD). The purpose of this pilot study was to determine if HRV was predictive of mortality in patients on dialysis and to identify at-risk factors. Patients on chronic hemodialysis (n = 53) were assessed at baseline and again 24 months later. Baseline measures quantified 24-hour HRV, health, depression, and quality of life (QoL). Twenty-four-month data determined mortality. Participants were African American, 49% male, aged 47.8+/-13.3 years, with 62.4+/-60 months of dialysis. Outcomes of 24-hour HRV measures were impaired for all groups. Factors including exercise and smoking were associated with diminished HRV. The low frequency-high frequency ratio was found to be the most influential HRV determinant of death. The ability to identify patients at-risk for death and to prescribe therapy to reduce risk could have significance for the care of patients with ESRD. PMID:15889802

  8. [Heart rate variability in the prognosis of tilt-testing results].

    PubMed

    Dupliakov, D V; Golovina, G A; Sysuenkova, E V; Glukhova, V L; Gar'kina, S V

    2012-01-01

    Study aim was assessment of dynamics of spectral parameters of heart rate variability (HRV) during the Westminster and Italian protocols of tilt-test (TT). We included in this study 114 patients with recurrent vasovagal syncope (VVS). Basing on TT results we distinguished 4 groups of patients: with positive result of the Westminster protocol (WPTT) (group 1, n=30); with negative result of WPTT (group 2, n=23); with positive result of the Italian protocol (IPTT) (group 3, n=44); with negative result of IPTT (group 4, n=11). Control group comprised 14 healthy persons without history of syncope. Spectral parameters of HRV were analyzed in 3 five minutes intervals (before TT in horizontal position, during first and last 5 minutes of orthostasis). Structure of vasovagal responses was similar for all TT protocols used. In lying position in patients of groups 1-3 lower values of LF1 and LF1/HF1 were registered, as well as high values of HF1 compared with the control group and patients with negative results of IPTT. Initial stage of TT in patients with positive result of WPTT (group 1) was characterized by almost twofold increase of LF values (n.u.) and decrease of HF parameters (n.u.) compared with other patients. In the group 1 during the second period. PMID:22839716

  9. Robust efficiency and actuator saturation explain healthy heart rate control and variability

    PubMed Central

    Li, Na; Cruz, Jerry; Chien, Chenghao Simon; Sojoudi, Somayeh; Recht, Benjamin; Stone, David; Csete, Marie; Bahmiller, Daniel; Doyle, John C.

    2014-01-01

    The correlation of healthy states with heart rate variability (HRV) using time series analyses is well documented. Whereas these studies note the accepted proximal role of autonomic nervous system balance in HRV patterns, the responsible deeper physiological, clinically relevant mechanisms have not been fully explained. Using mathematical tools from control theory, we combine mechanistic models of basic physiology with experimental exercise data from healthy human subjects to explain causal relationships among states of stress vs. health, HR control, and HRV, and more importantly, the physiologic requirements and constraints underlying these relationships. Nonlinear dynamics play an important explanatory role––most fundamentally in the actuator saturations arising from unavoidable tradeoffs in robust homeostasis and metabolic efficiency. These results are grounded in domain-specific mechanisms, tradeoffs, and constraints, but they also illustrate important, universal properties of complex systems. We show that the study of complex biological phenomena like HRV requires a framework which facilitates inclusion of diverse domain specifics (e.g., due to physiology, evolution, and measurement technology) in addition to general theories of efficiency, robustness, feedback, dynamics, and supporting mathematical tools. PMID:25092335

  10. Robust efficiency and actuator saturation explain healthy heart rate control and variability.

    PubMed

    Li, Na; Cruz, Jerry; Chien, Chenghao Simon; Sojoudi, Somayeh; Recht, Benjamin; Stone, David; Csete, Marie; Bahmiller, Daniel; Doyle, John C

    2014-08-19

    The correlation of healthy states with heart rate variability (HRV) using time series analyses is well documented. Whereas these studies note the accepted proximal role of autonomic nervous system balance in HRV patterns, the responsible deeper physiological, clinically relevant mechanisms have not been fully explained. Using mathematical tools from control theory, we combine mechanistic models of basic physiology with experimental exercise data from healthy human subjects to explain causal relationships among states of stress vs. health, HR control, and HRV, and more importantly, the physiologic requirements and constraints underlying these relationships. Nonlinear dynamics play an important explanatory role--most fundamentally in the actuator saturations arising from unavoidable tradeoffs in robust homeostasis and metabolic efficiency. These results are grounded in domain-specific mechanisms, tradeoffs, and constraints, but they also illustrate important, universal properties of complex systems. We show that the study of complex biological phenomena like HRV requires a framework which facilitates inclusion of diverse domain specifics (e.g., due to physiology, evolution, and measurement technology) in addition to general theories of efficiency, robustness, feedback, dynamics, and supporting mathematical tools. PMID:25092335

  11. Heart rate variability and arterial oxygen saturation response during extreme normobaric hypoxia.

    PubMed

    Botek, Michal; Krej?í, Jakub; De Smet, Stefan; Gába, Aleš; McKune, Andrew J

    2015-07-01

    The primary purpose of this study was to assess the response of autonomic cardiac activity and changes in the arterial oxygen saturation (SpO2) during normobaric hypoxia and subsequent recovery. Heart rate variability (HRV) and SpO2 were monitored in a supine position during hypoxia (FiO2=9.6%) for 10min, and normoxic recovery in 29 subjects. Spectral analysis of HRV quantified the autonomic cardiac activity by means of low frequency (LF) (0.05-0.15Hz) and high frequency (HF) (0.15-0.50Hz) power transformed by natural logarithm (Ln). Based on the SpO2 response to hypoxia, the subjects were divided into Resistant (RG, SpO2=80.8±7.0%) or Sensitive (SG, SpO2=67.2±2.9%) group. The SpO2 and vagal activity (LnHF) significantly decreased during hypoxia in both groups. A withdrawal in vagal activity was significantly greater in SG compared to RG. Moreover, only in SG, a relative increase in sympathetic modulation (Ln LF/HF) during hypoxia occurred. Correlations (r=-0.461, and r=0.595, both P<0.05) between ?SpO2 (delta) and ?Ln LF/HF, and ?LnHF were found. Based on results, it seems that SpO2 level could be an important factor that influences the autonomic cardiac response in hypoxia. PMID:25907329

  12. The changes of heart rate variability after unilateral stellate ganglion block

    PubMed Central

    Kim, Jang Jae; Lee, Hee Seung; Han, Jong In

    2010-01-01

    Background The effect of the unilateral stellate ganglion block (SGB) on cardiovascular regulation remains controversial. We wished to evaluate the changes in heart rate variability (HRV) after a unilateral stellate ganglion block in patients with head and neck pain in the present study. Methods Patients with head and neck pain (n = 89) were studied. HRV was determined before and after a C6 unilateral stellate ganglion block (right-sided SGB, 40; left-sided SGB, 49) using a paratracheal technique with 1% mepivacaine (6 ml). Results There were no significant differences in HRV indices before and after right-sided SGB. The log scale of power in the high frequency range (lnHF) was increased and ratio of power in the low frequency range (LF) to power in the high frequency range (HF) ratio was decreased after left-sided SGB. Conclusions These results demonstrated that left-sided SGB increased parasympathetic activities in patients with head and neck pain. PMID:20498813

  13. Exposure to Discrimination and Heart Rate Variability Reactivity to Acute Stress among Women with Diabetes.

    PubMed

    Wagner, Julie; Lampert, Rachel; Tennen, Howard; Feinn, Richard

    2013-11-01

    Exposure to racial discrimination has been linked to physiological reactivity. This study investigated self-reported exposure to racial discrimination and parasympathetic [high-frequency heart rate variability (HF-HRV)] and sympathetic (norepinephrine and cortisol) activity at baseline and then again after acute laboratory stress. Lifetime exposure to racial discrimination was measured with the Schedule of Racist Events scale. Thirty-two women (16 Black and 16 White) with type 2 diabetes performed a public speaking stressor. Beat-to-beat intervals were recorded on electrocardiograph recorders, and HF-HRV was calculated using spectral analysis and natural log transformed. Norepinephrine and cortisol were measured in blood. Higher discrimination predicted lower stressor HF-HRV, even after controlling for baseline HF-HRV. When race, age, A1c and baseline systolic blood pressure were also controlled, racial discrimination remained a significant independent predictor of stressor HF-HRV. There was no association between lifetime discrimination and sympathetic markers. In conclusion, preliminary data suggest that among women with type 2 diabetes mellitus (T2DM), exposure to racial discrimination is adversely associated with parasympathetic, but not sympathetic, reactivity. Copyright © 2013 John Wiley & Sons, Ltd. PMID:24194397

  14. Measurement of heart rate variability and stress evaluation by using microwave reflectometric vital signal sensing

    NASA Astrophysics Data System (ADS)

    Nagae, Daisuke; Mase, Atsushi

    2010-09-01

    In this paper, we present two robust signal processing techniques for stress evaluation using a microwave reflectometric cardiopulmonary sensing instrument. These techniques enable the heart rate variability (HRV) to be recovered from measurements of body-surface dynamic motion, which is subsequently used for the stress evaluation. Specifically, two novel elements are introduced: one is a reconfiguration of the HRV from the cross-correlation function between a measurement signal and a template signal which is constructed by averaging periodic component over a measurement time. The other is a reconstruction of the HRV from the time variation of the heartbeat frequency; this is evaluated by a repetition of the maximum entropy method. These two signal processing techniques accomplish the reconstruction of the HRV, though they are completely different algorithms. For validations of our model, an experimental setup is presented and several sets of experimental data are analyzed using the two proposed signal processing techniques, which are subsequently used for the stress evaluation. The results presented herein are consistent with electrocardiogram data.

  15. Meditation-induced changes in high-frequency heart rate variability predict smoking outcomes

    PubMed Central

    Libby, Daniel J.; Worhunsky, Patrick D.; Pilver, Corey E.; Brewer, Judson A.

    2012-01-01

    Background: High-frequency heart rate variability (HF-HRV) is a measure of parasympathetic nervous system (PNS) output that has been associated with enhanced self-regulation. Low resting levels of HF-HRV are associated with nicotine dependence and blunted stress-related changes in HF-HRV are associated with decreased ability to resist smoking. Meditation has been shown to increase HF-HRV. However, it is unknown whether tonic levels of HF-HRV or acute changes in HF-HRV during meditation predict treatment responses in addictive behaviors such as smoking cessation. Purpose: To investigate the relationship between HF-HRV and subsequent smoking outcomes. Methods: HF-HRV during resting baseline and during mindfulness meditation was measured within two weeks of completing a 4-week smoking cessation intervention in a sample of 31 community participants. Self-report measures of smoking were obtained at a follow up 17-weeks after the initiation of treatment. Results: Regression analyses indicated that individuals exhibiting acute increases in HF-HRV from resting baseline to meditation smoked fewer cigarettes at follow-up than those who exhibited acute decreases in HF-HRV (b = ?4.89, p = 0.008). Conclusion: Acute changes in HF-HRV in response to meditation may be a useful tool to predict smoking cessation treatment response. PMID:22457646

  16. Using near infrared spectroscopy and heart rate variability to detect mental overload.

    PubMed

    Durantin, G; Gagnon, J-F; Tremblay, S; Dehais, F

    2014-02-01

    Mental workload is a key factor influencing the occurrence of human error, especially during piloting and remotely operated vehicle (ROV) operations, where safety depends on the ability of pilots to act appropriately. In particular, excessively high or low mental workload can lead operators to neglect critical information. The objective of the present study is to investigate the potential of functional near infrared spectroscopy (fNIRS) - a non-invasive method of measuring prefrontal cortex activity - in combination with measurements of heart rate variability (HRV), to predict mental workload during a simulated piloting task, with particular regard to task engagement and disengagement. Twelve volunteers performed a computer-based piloting task in which they were asked to follow a dynamic target with their aircraft, a task designed to replicate key cognitive demands associated with real life ROV operating tasks. In order to cover a wide range of mental workload levels, task difficulty was manipulated in terms of processing load and difficulty of control - two critical sources of workload associated with piloting and remotely operating a vehicle. Results show that both fNIRS and HRV are sensitive to different levels of mental workload; notably, lower prefrontal activation as well as a lower LF/HF ratio at the highest level of difficulty, suggest that these measures are suitable for mental overload detection. Moreover, these latter measurements point toward the existence of a quadratic model of mental workload. PMID:24184083

  17. Effects of acute hypoxia on heart rate variability, sample entropy and cardiorespiratory phase synchronization

    PubMed Central

    2014-01-01

    Background Investigating the responses of autonomic nervous system (ANS) in hypoxia may provide some knowledge about the mechanism of neural control and rhythmic adjustment. The integrated cardiac and respiratory system display complicated dynamics that are affected by intrinsic feedback mechanisms controlling their interaction. To probe how the cardiac and respiratory system adjust their rhythms in different simulated altitudes, we studied heart rate variability (HRV) in frequency domain, the complexity of heartbeat series and cardiorespiratory phase synchronization (CRPS) between heartbeat intervals and respiratory cycles. Methods In this study, twelve male subjects were exposed to simulated altitude of sea level, 3000 m and 4000 m in a hypobaric chamber. HRV was assessed by power spectral analysis. The complexity of heartbeat series was quantified by sample entropy (SampEn). CRPS was determined by cardiorespiratory synchrogram. Results The power spectral HRV indices at all frequency bands depressed according to the increase of altitude. The SampEn of heartbeat series increased significantly with the altitude (P?

  18. Toward Capturing Momentary Changes of Heart Rate Variability by a Dynamic Analysis Method

    PubMed Central

    Zhang, Haoshi; Zhu, Mingxing; Zheng, Yue; Li, Guanglin

    2015-01-01

    The analysis of heart rate variability (HRV) has been performed on long-term electrocardiography (ECG) recordings (12~24 hours) and short-term recordings (2~5 minutes), which may not capture momentary change of HRV. In this study, we present a new method to analyze the momentary HRV (mHRV). The ECG recordings were segmented into a series of overlapped HRV analysis windows with a window length of 5 minutes and different time increments. The performance of the proposed method in delineating the dynamics of momentary HRV measurement was evaluated with four commonly used time courses of HRV measures on both synthetic time series and real ECG recordings from human subjects and dogs. Our results showed that a smaller time increment could capture more dynamical information on transient changes. Considering a too short increment such as 10 s would cause the indented time courses of the four measures, a 1-min time increment (4-min overlapping) was suggested in the analysis of mHRV in the study. ECG recordings from human subjects and dogs were used to further assess the effectiveness of the proposed method. The pilot study demonstrated that the proposed analysis of mHRV could provide more accurate assessment of the dynamical changes in cardiac activity than the conventional measures of HRV (without time overlapping). The proposed method may provide an efficient means in delineating the dynamics of momentary HRV and it would be worthy performing more investigations. PMID:26172953

  19. The Effects of Guided Imagery on Heart Rate Variability in Simulated Spaceflight Emergency Tasks Performers

    PubMed Central

    Yijing, Zhang; Xiaoping, Du; Fang, Liu; Xiaolu, Jing; Bin, Wu

    2015-01-01

    Objectives. The present study aimed to investigate the effects of guided imagery training on heart rate variability in individuals while performing spaceflight emergency tasks. Materials and Methods. Twenty-one student subjects were recruited for the experiment and randomly divided into two groups: imagery group (n = 11) and control group (n = 10). The imagery group received instructor-guided imagery (session 1) and self-guided imagery training (session 2) consecutively, while the control group only received conventional training. Electrocardiograms of the subjects were recorded during their performance of nine spaceflight emergency tasks after imagery training. Results. In both of the sessions, the root mean square of successive differences (RMSSD), the standard deviation of all normal NN (SDNN), the proportion of NN50 divided by the total number of NNs (PNN50), the very low frequency (VLF), the low frequency (LF), the high frequency (HF), and the total power (TP) in the imagery group were significantly higher than those in the control group. Moreover, LF/HF of the subjects after instructor-guided imagery training was lower than that after self-guided imagery training. Conclusions. Guided imagery was an effective regulator for HRV indices and could be a potential stress countermeasure in performing spaceflight tasks. PMID:26137491

  20. Heart rate variability and treatment outcome in major depression: a pilot study.

    PubMed

    Jain, Felipe A; Cook, Ian A; Leuchter, Andrew F; Hunter, Aimee M; Davydov, Dmitry M; Ottaviani, Cristina; Tartter, Molly; Crump, Caroline; Shapiro, David

    2014-08-01

    Variations in heart rate variability (HRV) have been associated with major depressive disorder (MDD), but the relationship of baseline HRV to treatment outcome in MDD is unclear. We conducted a pilot study to examine associations between resting baseline HRV and MDD treatment outcome. We retrospectively tested several parameters of HRV in an MDD treatment study with escitalopram (ESC, N=26) to generate a model of how baseline HRV related to treatment outcome, and cross-validated the model in a separate trial of MDD treatment with Iyengar yoga (IY, N=16). Lower relative power of very low frequency (rVLF) HRV at baseline predicted improvement in depressive symptoms when adjusted for age and gender (R2>.43 and p<0.05 for both trials). Although vagal parasympathetic measures were correlated with antidepressant treatment outcome, their predictive power was not significant after adjusting for age and gender. In conclusion, baseline resting rVLF was associated with depression treatment outcome in two independent MDD treatment studies. These results should be interpreted with caution due to limited sample size, but a strength of this study is its validation of the rVLF predictor in an independent sample. rVLF merits prospective confirmation as a candidate biomarker. PMID:24769434

  1. Orthostatic influence on heart rate and blood pressure variability in trained persons with tetraplegia.

    PubMed

    Otsuka, Yasuko; Shima, Norihiro; Moritani, Toshio; Okuda, Kuniharu; Yabe, Kyonosuke

    2008-09-01

    To examine the orthostatic influence on heart rate and blood pressure variability in persons with tetraplegia playing wheelchair basketball, ten trained persons with tetraplegia, ten untrained persons with tetraplegia, and ten able-bodied participated 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 degrees sitting were performed. The ratio of the high frequency to total frequency (HF/TF) in the R-R interval decreased from supine (0.5 +/- 0.2) to sitting (0.3 +/- 0.2), and the low frequency (LF) power in systolic blood pressure increased from 4.7 +/- 9.1 to 15.0 +/- 13.1 mmHg(2) only in the untrained persons with tetraplegia (P < 0.01). The decrease in the HF/TF ratio in the untrained persons with tetraplegia indicates attenuated parasympathetic activity to the orthostatic challenge and the similar increase in LF power indicate that parasympathetic activity was reduced and sympathetic activity increased only in these persons. These results suggest that training enhances cardiovascular stability in tetraplegic subjects. PMID:18542988

  2. The relationship between air pollutants and heart-rate variability among community residents in Korea.

    PubMed

    Min, Kyoung-Bok; Min, Jin-Young; Cho, Sung-Il; Paek, Domyung

    2008-02-01

    Air pollution, both particulate and gaseous, is known to cause adverse health effects and is associated with increased cardiovascular mortality and morbidity. With a growing recognition in the importance of the autonomic nervous system in air pollution, we examined the effects of air pollutants, namely, particulate matter (PM10), sulfur dioxide (SO2), and nitric dioxide (NO2), on cardiac autonomic function by measuring heart-rate variability (HRV) among community residents. This study was conducted at Taein Island, located off the southern coast of South Korea; 1349 subjects (596 males and 753 females) were included in this analysis. Subjects responded to the interview about general characteristics and an HRV examination was conducted. Exposure data were collected from the Environmental Management Corporation during the same period of HRV measurement. Linear regression analyses were carried out to evaluate the association over 72 h, and the parameters of HRV indices were presented as the percentage change. The exposures to PM(10), SO(2), and NO2 were associated with reduced HRV indices, and significant decreases in the standard deviation of the normal to normal interval (SDNN) and low frequency (LF) domain effect, and the effect was largely continued until 12 h. Our results suggest that air pollutants stimulate the autonomic nervous system and provoke an imbalance in cardiac autonomic control. Thus, these subclinical effects may lead to pathological consequences, particularly in high-risk patients and susceptible subjects. PMID:18302051

  3. A Body Shape Index and Heart Rate Variability in Healthy Indians with Low Body Mass Index

    PubMed Central

    Thomas, Tinku; Bharathi, Ankalmadagu Venkatsubbareddy; Sucharita, Sambashivaiah

    2014-01-01

    Background. One third of Indian population is said to be suffering from chronic energy deficiency (CED), with increased risk of developing chronic diseases. A new anthropometric measure called A Body Shape Index (ABSI) is said to be a better index in predicting risks for premature mortality. ABSI is also in part said to be a surrogate of visceral fat. Objective. The present study aimed to explore the association between indices of HRV (heart rate variability), BMI, WC, and ABSI in healthy Indian males with low BMI (BMI < 18.5?kg/m2) and to compare with normal BMI group (BMI 18.5 to 24.9?kg/m2). Methodology. ABSI and BMI were derived from anthropometric parameters, namely, height, weight, and waist circumference in 178 males aged 18 to 78 years. Subjects were categorized into two groups based on their BMI. Results and Conclusions. Power spectral analysis of HRV demonstrated a significant negative correlation between Log HF (high frequency) and ABSI in both low BMI [?24.2 (9.4), P < 0.05] and normal BMI group [?23.41 (10.1), P < 0.05] even after controlling for age. Thus even with slight increase in BMI among low BMI individuals, there could be a greater risk of cardiovascular morbidity and mortality. PMID:25371818

  4. Preference and resistance to change with constant- and variable-duration terminal links: independence of reinforcement rate and magnitude.

    PubMed

    Grace, Randolph C; Bedell, Melissa A; Nevin, John A

    2002-05-01

    Pigeons responded in a three-component multiple concurrent-chains procedure in which the variable-interval reinforcement schedules were the same across components but magnitudes differed across components. The terminal links were arranged either as a variable delay followed by presentation of a reinforcer ("variable duration") or as a fixed period of access to the schedule during which a variable number of reinforcers could be earned ("constant duration"). Relative reinforcement rate was varied parametrically across both types of conditions. After baseline training in each condition, resistance to change of terminal-link responding was assessed by delivering food during the initial links according to a variable-time schedule. Both preference and resistance to change were more sensitive to reinforcement-rate differences in the constant-duration conditions. Sensitivities of preference and resistance to change to relative reinforcement rate did not change depending on relative reinforcement magnitude. Taken together, these results confirm and extend those of prior studies, and suggest that reinforcement rate and magnitude combine additively to determine preference and resistance to change. A single structural relation linking preference and resistance to change describes all the data from this and several related studies. PMID:12083678

  5. Multifractal analysis of heart rate variability and laser Doppler flowmetry fluctuations:comparison of results from different numerical methods

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology.

  6. Analytical Treatment of the Metabolic Effects of Isocaloric Stimulant on Heart Rate Variability as Measured by Electrocardiograph

    NASA Astrophysics Data System (ADS)

    Taffe, Lauren Rachelle

    Heart Rate variability (HRV) is measured during a period that includes ingestion and digestion of 900 kilogram calories of carbohydrate and fat beverages on two separate occasions. Autoregressive (AR) analysis, Poincare Plot Analysis (PPA), Detrended Fluctuation Analysis (DFA), and the Largest Lyapunov Exponent (LLE) highlights variations in the linear and non-linear indices with respect to time. DFA indices indicated that all individuals were healthy (??1). In addition, an overall increase of ? over the 3-hour observation time shows increased sympathetic intonation. Body Mass Index (BMI) influences on HRV were found. Over short time scales, DFA's ? 1 index suggests the potentiality for future patho-physiological risk in those with high BMI>25. Over longer time scales, ?2 has no significant differentiation among different BMI groups. The application of k-means cluster analysis revealed a connection to BMI when ? and ? 1 /?2 parameters were used. We believe that the LLE indicates an increased stability during digestion of the hypercaloric beverages. Groups with BMI>25 have smaller LLE, on average, than BMI? 25. This does substantiate the AR, Poincare, and DFA analyses of groups with higher BMI having less sympathetic increase when compared to lower BMI groups due to caloric metabolism.

  7. Variable stiffness material and structural concepts for morphing applications

    NASA Astrophysics Data System (ADS)

    Kuder, Izabela K.; Arrieta, Andres F.; Raither, Wolfram E.; Ermanni, Paolo

    2013-11-01

    Morphing, understood as the ability to undergo pronounced shape adaptations to optimally respond to a diversity of operational conditions, has been singled out as a future direction in the pursuit of maximised efficiency of lightweight structures. Whereas a certain degree of adaptivity can be accomplished conventionally by means of mechanical systems, compliance allowing for substantial reversible deformability exhibits far more potential as a morphing strategy. A promising solution to the inherent contradiction between high stiffness and reversible deformation capacity posed by morphing is offered by introducing variable stiffness components. This notion indicates the provision of a controllable range of deformation resistance levels in place of fixed properties, as required by real-time shape adaptation dictated by maximum efficiency under changing external conditions. With special emphasis on the morphing context, the current review aims to identify the main tendencies, undertaking a systematic classification of existing approaches involving stiffness variability. Four broad categories in which variable stiffness has been applied to morphing are therefore distinguished and detailed: material engineering, active mechanical design, semi-active techniques and elastic structural behaviour. Adopting a wide perspective, the study highlights key capabilities, limitations and challenges. The need for attention directed to the variable stiffness strategy is recognised and the significance of intensive research activities in a highly integrated and multidisciplinary environment emphasised if higher maturity stages of the concepts are to be reached. Finally, the potential of emerging directions of semi-active design involving electro-bonded laminates and multi-stable structures is brought into focus.

  8. Application of Variable Structure Control in Missile Electromechanical Actuator System

    Microsoft Academic Search

    Yuan Gao; Liang-xian Gu; Lei Pan

    2008-01-01

    Parameter variation and load disturbance will have great influence on the performance of missile electromechanical actuator system and further on the performance of the entire missile system during the missile flight process. To solve this problem, a variable structure control system for missile electromechanical actuator system was proposed in this paper. To verify the proposed control scheme, simulation has been

  9. An Application of Durkheim's Theory of Suicide to Prison Suicide Rates in the United States

    ERIC Educational Resources Information Center

    Tartaro, Christine; Lester, David

    2005-01-01

    E. Durkheim (1897) suggested that the societal rate of suicide might be explained by societal factors, such as marriage, divorce, and birth rates. The current study examined male prison suicide rates and suicide rates for men in the total population in the United States and found that variables based on Durkheim's theory of suicide explained…

  10. Preliminary Results of an Open Label Study of Heart Rate Variability Biofeedback for the Treatment of Major Depression

    Microsoft Academic Search

    Maria Katsamanis Karavidas; Paul M. Lehrer; Evgeny Vaschillo; Bronya Vaschillo; Humberto Marin; Steven Buyske; Igor Malinovsky; Diane Radvanski; Afton Hassett

    2007-01-01

    Major depressive disorder (MDD) is a common mood disorder that can result in significant discomfort as well as interpersonal\\u000a and functional disability. A growing body of research indicates that autonomic function is altered in depression, as evidenced\\u000a by impaired baroreflex sensitivity, changes in heart rate, and reduced heart rate variability (HRV). Decreased vagal activity\\u000a and increased sympathetic arousal have been

  11. Buffering of Life Histories against Environmental Stochasticity: Accounting for a Spurious Correlation between the Variabilities of Vital Rates and Their

    Microsoft Academic Search

    William F. Morris; Daniel F. Doak

    abstract:,Life-history theory predicts vital rates that on average make,large contributions,to the annual multiplication rate of a line- age should be highly buffered against environmental,variability. This prediction has been tested by looking for a negative correlation be- tween the sensitivities (or elasticities) of the elements in a projection matrix and their variances (or coefficients of variation). Here, we show,by constructing random,matrices

  12. Domain Adaptation Under Data Misalignment: An Application to Cepheid Variable Star Classification

    E-print Network

    Vilalta, Ricardo

    Domain Adaptation Under Data Misalignment: An Application to Cepheid Variable Star Classification methodology on the classification of Cepheid variable stars according to their pulsation mode: fundamental analysis, as for example when the training and testing samples correspond to stars (i.e., to light curves

  13. SPATIAL VARIABILITY IN PHOSPHORUS BEFORE AND AFTER POULTRY MANURE APPLICATION IN SMALL PLOTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate assessment of environmental research on small plots requires knowledge of the spatial variability in soil properties at small spatial scales. The effect of management practices, such as manure application, can affect this variability and should be accounted for in small plot studies. The ...

  14. 18.01 Single Variable Calculus, Fall 2003

    E-print Network

    Starr, Jason M.

    DIFFERENTIATION AND INTEGRATION OF FUNCTIONS OF ONE VARIABLE, WITH APPLICATIONS. CONCEPTS OF FUNCTION, LIMITS, AND CONTINUITY. DIFFERENTIATION RULES, APPLICATION TO GRAPHING, RATES, APPROXIMATIONS, AND EXTREMUM PROBLEMS. ...

  15. Cepheid Variables and their Application to the Cosmological Distance Scale 

    E-print Network

    Hoffmann, Samantha L

    2013-05-02

    In the current era of “precision cosmology”, measuring the expansion rate of the Universe (Hubble constant, or H0) more accurately and precisely helps to better constrain the properties of dark energy. Cepheid-based ...

  16. Ivabradine Improves Heart Rate Variability in Patients with Nonischemic Dilated Cardiomyopathy

    PubMed Central

    Kurtoglu, Ertugrul; Balta, Sevket; Karakus, Yasin; Yasar, Erdogan; Cuglan, Bilal; Kaplan, Ozgur; Gozubuyuk, Gokhan

    2014-01-01

    Background Ivabradine is a novel specific heart rate (HR)-lowering agent that improves event-free survival in patients with heart failure (HF). Objectives We aimed to evaluate the effect of ivabradine on time domain indices of heart rate variability (HRV) in patients with HF. Methods Forty-eight patients with compensated HF of nonischemic origin were included. Ivabradine treatment was initiated according to the latest HF guidelines. For HRV analysis, 24-h Holter recording was obtained from each patient before and after 8 weeks of treatment with ivabradine. Results The mean RR interval, standard deviation of all normal to normal RR intervals (SDNN), the standard deviation of 5-min mean RR intervals (SDANN), the mean of the standard deviation of all normal-to-normal RR intervals for all 5-min segments (SDNN index), the percentage of successive normal RR intervals exceeding 50 ms (pNN50), and the square root of the mean of the squares of the differences between successive normal to normal RR intervals (RMSSD) were low at baseline before treatment with ivabradine. After 8 weeks of treatment with ivabradine, the mean HR (83.6 ± 8.0 and 64.6 ± 5.8, p < 0.0001), mean RR interval (713 ± 74 and 943 ± 101 ms, p < 0.0001), SDNN (56.2 ± 15.7 and 87.9 ± 19.4 ms, p < 0.0001), SDANN (49.5 ± 14.7 and 76.4 ± 19.5 ms, p < 0.0001), SDNN index (24.7 ± 8.8 and 38.3 ± 13.1 ms, p < 0.0001), pNN50 (2.4 ± 1.6 and 3.2 ± 2.2 %, p < 0.0001), and RMSSD (13.5 ± 4.6 and 17.8 ± 5.4 ms, p < 0.0001) substantially improved, which sustained during both when awake and while asleep. Conclusion Our findings suggest that treatment with ivabradine improves HRV in nonischemic patients with HF. PMID:25119894

  17. Autonomic nervous system activity assessment by heart rate variability in experimental bladder outlet obstruction.

    PubMed

    Dobrek, ?ukasz; Baranowska, Agnieszka; Skowron, Beata; Thor, Piotr J

    2013-01-01

    A syndrome with urgency, with or without associated urine incontinence and usually accompanied by higher urinary frequency and nocturia has been named "overactive bladder; OAB". OAB is an entity with complex pathophysiology, involving both myogenic and neurogenic (afferent / efferent bladder innervation) disturbances. OAB symptoms accompany benign prostatic hypertrophy--BPH ("obstructive OAB"). The aim of the study was to estimate the autonomic nervous system activity (ANS) in the experimental bladder outlet obstruction (BOO) which was an animal model of the human BPH. The study was conducted using 30 female rats, divided into two groups: BOO animals (n=15), with surgically induced BOO (by partial ligation of the proximal urethra) and control ones (n=15), which underwent sham procedure (without urethral ligation). Two weeks after the surgery, in both groups, ANS activity was estimated using time- and spectral analysis of the heart rate variability recordings. The bladder overactivity in BOO animals was confirmed using urodynamic recordings and bladder histological assessment, juxtaposed against the results of the control group. The key finding of our study was the development of autonomic disturbances in bladder outlet obstruction (BOO) rats. Our study revealed that BOO animals were characterised by diminished rMSSD and spectral HRV parameters: TP, LF and HF, in comparison with the control group. The normalised nLF and nHF parameters did not differ significantly in both groups, although slight changes in the nLF (increased) and nHF (decreased) were noted in BOO group. The absolute VLF value was almost the same in both studied populations, however, the percentage part of this component in the appropriate HRV spectrum differed considerably in both studied groups. In BOO animals, VLF percentage amounted to about 90%, whereas in control animals this parameter reached only about 53% of the total power spectrum. Thus, to sum up, our findings suggest autonomic imbalance with decreased global autonomic tension and diminished parasympathetic activity with relatively sympathetic overactivity. PMID:23619221

  18. Physical Activity and Heart Rate Variability in Older Adults: The Cardiovascular Health Study

    PubMed Central

    Soares-Miranda, Luisa; Sattelmair, Jacob; Chaves, Paulo; Duncan, Glen; Siscovick, David S; Stein, Phyllis K; Mozaffarian, Dariush

    2014-01-01

    Background Cardiac mortality and electrophysiologic dysfunction both increase with age. Heart rate variability (HRV) provides indices of autonomic function and electrophysiology that are associated with cardiac risk. How habitual physical activity (PA) among older adults prospectively relates to HRV, including nonlinear indices of erratic sinus patterns, is not established. We hypothesized that increasing levels of both total leisure-time activity and walking would be prospectively associated with more favorable time-domain, frequency-domain, and nonlinear HRV measures in older adults. Methods and Results We evaluated serial longitudinal measures of both PA and 24-hour Holter HRV over 5 years among 985 older US adults in the community-based Cardiovascular Health Study. After multivariable adjustment, greater total leisure-time activity, walking distance, and walking pace were each prospectively associated with specific, more favorable HRV indices, including higher 24-hour standard-deviation-of-all-normal-to-normal-intervals (SDNN, p-trend=0.009, 0.02, 0.06, respectively) and ultra-low-frequency-power (p-trend=0.02, 0.008, 0.16, respectively). Greater walking pace was also associated with higher short-term-fractal-scaling-exponent (p-trend=0.003) and lower Poincare ratio (p-trend=0.02), markers of less erratic sinus patterns. Conclusions Greater total leisure-time activity, as well as walking alone, were prospectively associated with more favorable and specific indices of autonomic function in older adults, including several suggestive of more normal circadian fluctuations and less erratic sinoatrial firing. Our results suggest potential mechanisms that might contribute to lower cardiovascular mortality with habitual PA later in life. PMID:24799513

  19. Effects of exercise intensity and duration on nocturnal heart rate variability and sleep quality.

    PubMed

    Myllymäki, Tero; Rusko, Heikki; Syväoja, Heidi; Juuti, Tanja; Kinnunen, Marja-Liisa; Kyröläinen, Heikki

    2012-03-01

    Acute physical exercise may affect cardiac autonomic modulation hours or even days during the recovery phase. Although sleep is an essential recovery period, the information on nocturnal autonomic modulation indicated by heart rate variability (HRV) after different exercises is mostly lacking. Therefore, this study investigated the effects of exercise intensity and duration on nocturnal HR, HRV, HR, and HRV-based relaxation, as well as on actigraphic and subjective sleep quality. Fourteen healthy male subjects (age 36 ± 4 years, maximal oxygen uptake 49 ± 4 ml/kg/min) performed five different running exercises on separate occasions starting at 6 p.m. with HR guidance at home. The effect of intensity was studied with 30 min of exercises at intensities corresponding to HR level at 45% (easy), 60% (moderate) and 75% (vigorous) of their maximal oxygen uptake. The effect of duration was studied with 30, 60, and 90 min of moderate exercises. Increased exercise intensity elevated nocturnal HR compared to control day (p < 0.001), but it did not affect nocturnal HRV. Nocturnal HR was greater after the day with 90- than 30- or 60-min exercises (p < 0.01) or control day (p < 0.001). Nocturnal HRV was lower after the 90-min exercise day compared to control day (p < 0.01). Neither exercise intensity nor duration had any impact on actigraphic or subjective sleep quality. The results suggest that increased exercise intensity and/or duration cause delayed recovery of nocturnal cardiac autonomic modulation, although long exercise duration was needed to induce changes in nocturnal HRV. Increased exercise intensity or duration does not seem to disrupt sleep quality. PMID:21667290

  20. Chaotic Signatures of Heart Rate Variability and Its Power Spectrum in Health, Aging and Heart Failure

    PubMed Central

    Wu, Guo-Qiang; Arzeno, Natalia M.; Shen, Lin-Lin; Tang, Da-Kan; Zheng, Da-An; Zhao, Nai-Qing; Eckberg, Dwain L.; Poon, Chi-Sang

    2009-01-01

    A paradox regarding the classic power spectral analysis of heart rate variability (HRV) is whether the characteristic high- (HF) and low-frequency (LF) spectral peaks represent stochastic or chaotic phenomena. Resolution of this fundamental issue is key to unraveling the mechanisms of HRV, which is critical to its proper use as a noninvasive marker for cardiac mortality risk assessment and stratification in congestive heart failure (CHF) and other cardiac dysfunctions. However, conventional techniques of nonlinear time series analysis generally lack sufficient sensitivity, specificity and robustness to discriminate chaos from random noise, much less quantify the chaos level. Here, we apply a ‘litmus test’ for heartbeat chaos based on a novel noise titration assay which affords a robust, specific, time-resolved and quantitative measure of the relative chaos level. Noise titration of running short-segment Holter tachograms from healthy subjects revealed circadian-dependent (or sleep/wake-dependent) heartbeat chaos that was linked to the HF component (respiratory sinus arrhythmia). The relative ‘HF chaos’ levels were similar in young and elderly subjects despite proportional age-related decreases in HF and LF power. In contrast, the near-regular heartbeat in CHF patients was primarily nonchaotic except punctuated by undetected ectopic beats and other abnormal beats, causing transient chaos. Such profound circadian-, age- and CHF-dependent changes in the chaotic and spectral characteristics of HRV were accompanied by little changes in approximate entropy, a measure of signal irregularity. The salient chaotic signatures of HRV in these subject groups reveal distinct autonomic, cardiac, respiratory and circadian/sleep-wake mechanisms that distinguish health and aging from CHF. PMID:19183809

  1. Lower heart rate variability associated with military sexual trauma rape and posttraumatic stress disorder.

    PubMed

    Lee, Elizabeth Ann Davis; Theus, Sue A

    2012-10-01

    Low heart rate variability (HRV) can occur with psychological disorders such as posttraumatic stress disorder (PTSD). The purpose of this study was to examine the association between PTSD by trauma type and decreased HRV measures in female veterans with cardiac symptoms. This secondary analysis utilized data from a previous study of female veterans (n = 125) examined for cardiac symptoms by Holter and electrocardiogram recordings at a Veterans Affairs medical center. The mean HRV measure from three 10-s data segments with spontaneous respirations was obtained for each subject. PTSD diagnosis and type of trauma exposure were collected from mental health consult notes. Chi-square was used for frequency of subject characteristics; independent t tests and one-way analysis of variance (ANOVA) compared means of HRV measures between trauma types. Statistical significance was set at p < .05 a priori. By ANOVA, significantly lower log-transformed standard deviation of all normal sinus rhythm R-R intervals (SDNN) and log-transformed square root of the mean of the sum of the squares of differences between adjacent normal sinus rhythm R-R intervals (RMSSD) were found in the PTSD group with documented rape military sexual trauma (MST) compared to other groups including no PTSD, PTSD following MST with rape not specified, combat exposure, and nonmilitary-related trauma; lower HRV measures were not found with other PTSD types of trauma. This study suggests rape MST with concomitant PTSD may be a risk factor for decreased HRV in female veterans examined for cardiac symptoms. PMID:22899708

  2. Vagal nerve activity and the high frequency peak of the heart rate variability.

    PubMed

    Yambe, T; Nanka, S; Kobayashi, S; Tanaka, A; Yoshizawa, M; Abe, K; Tabayashi, K; Takeda, H; Nitta, S

    1999-05-01

    For the Quality of life (QOL) of patients with an artificial heart system, monitoring an information of the cardiovascular control system may be important. We have been evaluating the autonomic nervous system for that purpose. Recently, fluctuations in hemodynamic parameters including heart rate variability (HRV) were evaluated by means of spectral analysis and nonlinear mathematical analysis. Respiratory wavers in HRV were thought to reflect ongoing information of the parasympathetic nerve activity. Is it true? In order to confirm this hypothesis, we recorded vagal nerve activity directly in the chronic animal experiments. Six healthy adult goats were anesthetized with Halothene inhalation and thoracotomy were performed by the fourth lib resection during mechanical ventilation. Arterial blood pressure, right and left atrial pressures were continuously monitored with the catheter insertion. Cardiac output was measured by the electromagnetic flowmeter attached to the ascending aorta. After the chest was closed, incision was made to the left neck and left vagal nerve was separated. Stainless steel electrodes were inserted into the vagal nerve and fixed by the plasticizer. After the incision was closed, the goats were transferred to the cage and extubated after waking. Hemodynamic parameters and vagal nerve activity were measured in the awake condition. The results showed that clear observation of the autonomic nerve discharges were embodied by this experimental system. The vagal nerve discharges were synchronized with heart beat and respiration. The vagal nerve tonus was significantly influenced by the hemodynamic alteration. However in some condition, the respiratory wave was not always consistent with tonus of the vagal nerve activity, thus suggesting that we should check another information to evaluate the parasympathetic tone. We must continue this study to evaluate an autonomic nerve during artificial heart circulation. PMID:10467931

  3. Heart Rate Variability in Association with Frequent Use of Household Sprays and Scented Products in SAPALDIA

    PubMed Central

    Adam, Martin; Schaffner, Emmanuel; Barthélémy, Jean-Claude; Carballo, David; Gaspoz, Jean-Michel; Rochat, Thierry; Schindler, Christian; Schwartz, Joel; Zock, Jan-Paul; Künzli, Nino; Probst-Hensch, Nicole; Team, SAPALDIA

    2012-01-01

    Background: Household cleaning products are associated with adverse respiratory health outcomes, but the cardiovascular health effects are largely unknown. Objective: We determined if long-term use of household sprays and scented products at home was associated with reduced heart rate variability (HRV), a marker of autonomic cardiac dysfunction. Methods: We recorded 24-hr electrocardiograms in a cross-sectional survey of 581 Swiss adults, ? 50 years of age, who answered a detailed questionnaire regarding their use of household cleaning products in their homes. The adjusted average percent changes in standard deviation of all normal-to-normal intervals in 24 hr (24-hr SDNN) and total power (TP) were estimated in multiple linear regression in association with frequency [< 1, 1–3, or 4–7 days/week, unexposed (reference)] of using cleaning sprays, air freshening sprays, and scented products. Results: Decreases in 24-hr SDNN and TP were observed with frequent use of all product types, but the strongest reductions were associated with air freshening sprays. Compared with unexposed participants, we found that using air freshening sprays 4–7 days/week was associated with 11% [95% confidence interval (CI): –20%, –2%] and 29% (95% CI: –46%, –8%) decreases in 24-hr SDNN and TP, respectively. Inverse associations of 24-SDNN and TP with increased use of cleaning sprays, air freshening sprays, and scented products were observed mainly in participants with obstructive lung disease (p < 0.05 for interactions). Conclusions: In predominantly older adult women, long-term frequent use of household spray and scented products was associated with reduced HRV, which suggests an increased risk of cardiovascular health hazards. People with preexisting pulmonary conditions may be more susceptible. PMID:22538298

  4. Short-term secondhand smoke exposure decreases heart rate variability and increases arrhythmia susceptibility in mice

    PubMed Central

    Chen, Chao-Yin; Chow, Drin; Chiamvimonvat, Nipavan; Glatter, Kathryn A.; Li, Ning; He, Yuxia; Pinkerton, Kent E.; Bonham, Ann C.

    2008-01-01

    Exposure to secondhand smoke (SHS), a major indoor air pollutant, is linked to increased cardiovascular morbidity and mortality, including cardiac arrhythmias. However, the mechanisms underlying the epidemiological findings are not well understood. Impaired cardiac autonomic function, indexed by reduced heart rate variability (HRV), may represent an underlying cause. The present study takes advantage of well-defined short-term SHS exposure (3 days, 6 h/day) on HRV and the susceptibility to arrhythmia in mice. With the use of electrocardiograph telemetry recordings in conscious mice, HRV parameters in the time domain were measured during the night after each day of exposure and 24 h after 3 days of exposure to either SHS or filtered air. The susceptibility to arrhythmia was determined after 3 days of exposure. Exposure to a low concentration of SHS [total suspended particle (TSP), 2.4 ± 3.2; and nicotine, 0.3 ± 0.1 mg/m3] had no significant effect on HRV parameters. In contrast, the exposure to a higher but still environmentally relevant concentration of SHS (TSP, 30 ± 1; and nicotine, 5 ± 1 mg/m3) significantly reduced HRV starting after the first day of exposure and continuing 24 h after the last day of exposure. Moreover, the exposed mice showed a significant increase in ventricular arrhythmia susceptibility and atrioventricular block. The data suggest that SHS exposure decreased HRV beyond the exposure period and was associated with an increase in arrhythmia susceptibility. The data provide insights into possible mechanisms underlying documented increases in cardiovascular morbidity and mortality in humans exposed to SHS. PMID:18552155

  5. Glutathione S-Transferase Polymorphisms, Passive Smoking, Obesity, and Heart Rate Variability in Nonsmokers

    PubMed Central

    Probst-Hensch, Nicole M.; Imboden, Medea; Dietrich, Denise Felber; Barthélemy, Jean-Claude; Ackermann-Liebrich, Ursula; Berger, Wolfgang; Gaspoz, Jean-Michel; Schwartz, Joel

    2008-01-01

    Background Disturbances of heart rate variability (HRV) may represent one pathway by which second-hand smoke (SHS) and air pollutants affect cardiovascular morbidity and mortality. The mechanisms are poorly understood. Objectives We investigated the hypothesis that oxidative stress alters cardiac autonomic control. We studied the association of polymorphisms in oxidant-scavenging glutathione S-transferase (GST) genes and their interactions with SHS and obesity with HRV. Methods A total of 1,133 nonsmokers > 50 years of age from a population-based Swiss cohort underwent ambulatory 24-hr electrocardiogram monitoring and reported on lifestyle and medical history. We genotyped GSTM1 and GSTT1 gene deletions and a GSTP1 (Ile105Val) single nucleotide polymorphism and analyzed genotype–HRV associations by multiple linear regressions. Results Homozygous GSTT1 null genotypes exhibited an average 10% decrease in total power (TP) and low-frequency-domain HRV parameters. All three polymorphisms modified the cross-sectional associations of HRV with SHS and obesity. Homozygous GSTM1 null genotypes with > 2 hr/day of SHS exposure exhibited a 26% lower TP [95% confidence interval (CI), 11 to 39%], versus a reduction of ?5% (95% CI, ?22 to 17%) in subjects with the gene and the same SHS exposure compared with GSTM1 carriers without SHS exposure. Similarly, obese GSTM1 null genotypes had, on average, a 22% (95% CI, 12 to 31%) lower TP, whereas with the gene present obesity was associated with only a 3% decline (95% CI, ?15% to 10%) compared with nonobese GSTM1 carriers. Conclusions GST deficiency is associated with significant HRV alterations in the general population. Its interaction with SHS and obesity in reducing HRV is consistent with an impact of oxidative stress on the autonomous nervous system. PMID:19057702

  6. Heart rate variability and arrhythmic patterns of 24-hour Holter electrocardiography among Nigerians with cardiovascular diseases

    PubMed Central

    Adebayo, Rasaaq Ayodele; Ikwu, Amanze Nkemjika; Balogun, Michael Olabode; Akintomide, Anthony Olubunmi; Ajayi, Olufemi Eyitayo; Adeyeye, Victor Oladeji; Mene-Afejuku, Tuoyo Omasan; Bamikole, Olaniyi James; Ogunyemi, Suraj Adefabi; Ajibare, Adeola Olubunmi; Oketona, Omolola Abiodun

    2015-01-01

    Background Facilities for Holter electrocardiography (ECG) monitoring in many Nigerian hospitals are limited. There are few published works in Nigeria on the use of 24-hour Holter ECG in cardiac arrhythmic evaluation of patients with cardiovascular diseases. Objective To study the clinical indications, arrhythmic pattern, and heart rate variability (HRV) among subjects referred for 24-hour Holter ECG at our Cardiac Care Unit. Methods Three-hundred and ten patients (134 males and 176 females) were studied consecutively over a 48-month period using Schiller type (MT-101) Holter ECG machine. Results Out of the 310 patients reviewed, 134 were males (43.2%) and 176 were females (56.8%). The commonest indication for Holter ECG was palpitation followed by syncope in 71 (23%) and 49 (15.8%) of subjects, respectively. Premature ventricular complex and premature atrial complex were the commonest types of arrhythmia in 51.5% and 15% subjects, respectively. Ventricular arrhythmia was more prevalent in dilated cardiomyopathy patients (85.7%). The HRV of subjects with palpitation, stroke, and diabetes mellitus with autonomic neuropathy, using standard deviation of normal to normal intervals average (milliseconds), were 107.32±49.61, 79.15±49.15, and 66.50±15.54, respectively. The HRV, using standard deviation of averages of normal to normal intervals average (milliseconds), of patients with palpitation, stroke, and diabetes mellitus with autonomic neuropathy were 77.39±62.34, 57.82±37.05, and 55.50±12.71, respectively. Conclusion Palpitation and syncope were the commonest indications for Holter ECG among our subjects. The commonest arrhythmic patterns were premature ventricular complex and premature atrial complex, with ventricular arrhythmia being more prevalent in dilated cardiomyopathy. There was a reduction in HRV in patients with stroke and diabetic autonomic neuropathy. PMID:26170685

  7. The Effects of Different Noise Types on Heart Rate Variability in Men

    PubMed Central

    Sim, Chang Sun; Sung, Joo Hyun; Cheon, Sang Hyeon; Lee, Jang Myung; Lee, Jae Won

    2015-01-01

    Purpose To determine the impact of noise on heart rate variability (HRV) in men, with a focus on the noise type rather than on noise intensity. Materials and Methods Forty college-going male volunteers were enrolled in this study and were randomly divided into four groups according to the type of noise they were exposed to: background, traffic, speech, or mixed (traffic and speech) noise. All groups except the background group (35 dB) were exposed to 45 dB sound pressure levels. We collected data on age, smoking status, alcohol consumption, and disease status from responses to self-reported questionnaires and medical examinations. We also measured HRV parameters and blood pressure levels before and after exposure to noise. The HRV parameters were evaluated while patients remained seated for 5 minutes, and frequency and time domain analyses were then performed. Results After noise exposure, only the speech noise group showed a reduced low frequency (LF) value, reflecting the activity of both the sympathetic and parasympathetic nervous systems. The low-to-high frequency (LF/HF) ratio, which reflected the activity of the autonomic nervous system (ANS), became more stable, decreasing from 5.21 to 1.37; however, this change was not statistically significant. Conclusion These results indicate that 45 dB(A) of noise, 10 dB(A) higher than background noise, affects the ANS. Additionally, the impact on HRV activity might differ according to the noise quality. Further studies will be required to ascertain the role of noise type. PMID:25510770

  8. Long-range correlations in heart rate variability during computer-mouse work under time pressure

    NASA Astrophysics Data System (ADS)

    Jiang, Dineng; He, Mulu; Qiu, Yihong; Zhu, Yisheng; Tong, Shanbao

    2009-04-01

    The aim of this study was to investigate the influences of time pressure on long-range correlations in heart rate variability (HRV), the effects of relaxation on the cardiovascular regulation system and the advantages of detrended fluctuation analysis (DFA) over the conventional power spectral analysis in discriminating states of the cardiovascular systems under different levels of time pressure. Volunteer subjects ( n=10, male/female=5/5) participated in a computer-mouse task consisting of five sessions, i.e. baseline session (BSS) which was free of time pressure, followed by sessions with 80% (SS80), 100% (SS100), 90% (SS90) and 150% (SS150) of the baseline time. Electrocardiogram (ECG) and task performance were recorded throughout the experiments. Two rest sessions before and after the computer-mouse work, i.e. RS1 and RS2, were also recorded as comparison. HRV series were subsequently analyzed by both conventional power spectral analysis and detrended fluctuation analysis (DFA). The long-term scaling exponent ?2 by DFA was significantly lower in SS80 than that in other sessions. It was also found that short-term release of time pressure had positive influences on the cardiovascular system, i.e. the ?2 in RS2 was significantly higher than that in SS80, SS100 and SS90. No significant differences were found between any two sessions by conventional power spectral analysis. Our results showed that DFA performed better in discriminating the states of cardiovascular autonomic modulation under time pressure than the conventional power spectral analysis.

  9. Analysis and application of variable conductance heat pipe air preheater

    Microsoft Academic Search

    Chengming Shi; Yang Wang; Quan Liao; Ying Yang

    2011-01-01

    The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature transfer matrix\\u000a was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer\\u000a surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could\\u000a be easily calculated

  10. The influence of mean heart rate on measures of heart rate variability as markers of autonomic function: a model study

    Microsoft Academic Search

    Hung-Wen Chiu; Ti-Ho Wang; Lu-Chou Huang; Han-Wen Tso; Tsair Kao

    2003-01-01

    Some studies have demonstrated that the assessments of autonomic activities from the alterations of heart rate variations (HRVs) after autonomic blockade and during exercise of high intensity by the spectral analysis of HRV seemed inconsistent with actual situation. The inconsistency is probably caused by the contributions of fluctuating magnitudes and mean levels of autonomic activities on HRV having not been

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

    E-print Network

    modulates the autonomic nervous system (ANS) by activating and desensitizing peripheral nicotinic1 of 4 Abstract--Heart rate variability (HRV) is frequently used to measure autonomic nervous system (ANS) activity. However, little is known about the mechanism underlying pharmacologically induced

  12. Development of variable-rate sprayer with laser scanning sensor to synchronize spray outputs to tree structures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Efficient and effective precision spray equipment and strategies have been constantly demanded to reduce pesticide use in tree crop productions. An experimental variable-rate air-assisted sprayer implemented with a high-speed laser scanning sensor was developed to control the spray output of individ...

  13. Van Driesche et al.: Efficacy of Variable and Fixed Parasitoid Rates 63 EFFECT OF PARASITOID RELEASE PATTERN ON WHITEFLY

    E-print Network

    Hoddle, Mark S.

    Van Driesche et al.: Efficacy of Variable and Fixed Parasitoid Rates 63 EFFECT OF PARASITOID commercial poinsettia production conditions we compared two patterns of parasitoid release for the aphelinid whitefly parasitoid Eretmocerus eremicus Rose and Zolnerowich. We compared the currently used pattern

  14. EFFECTS OF INSTILLED EMISSION PARTICULATE MATTER ON ELECTROCARDIOGRAPHIC INDICES AND HEART RATE VARIABILITY (HRV) IN SPONTANEOUSLY HYPERTENSIVE RATS

    EPA Science Inventory

    EFFECTS OF INSTILLED EMISSION PARTICULATE MATTER (EPM) ON ELECTROCARDIOGRAPHIC INDICES AND HEART RATE VARIABILITY (HRV) IN SPONTANEOUSLY HYPERTENSIVE (SH) RATS. L.B. Wichers1, J.P. Nolan2, W.H. Rowan2, M.J. Campen3, T.P. Jenkins4, D.L. Costa2, and W.P. Watkinson2. 1UNC SPH, Chap...

  15. Linear and nonlinear dynamics of heart rate variability after acute myocardial infarction with normal and reduced left ventricular ejection fraction

    Microsoft Academic Search

    Federico Lombardi; Giulia Sandrone; Andrea Mortara; Daniela Torzillo; Maria Teresa La Rovere; Maria Gabriella Signorini; Sergio Cerutti; Alberto Malliani

    1996-01-01

    We analyzed heart rate variability (HRV) in 2 groups of patients after acute myocardial infarction with normal and reduced ejection fraction (EF) by considering both the power of the 2 major harmonic components at low and high frequency and 2 indexes of nonlinear dynamics, namely the 1f slope and the correlation dimension D2. HRV of patients with a reduced EF

  16. Relationship between electrolytes and heart rate variability parameters in end-stage renal failure patients before and after hemodialysis

    Microsoft Academic Search

    Tsai Lung Wen; Wang Chung-Kwe; Ing Fang Yang; Ten Fang Yang

    O Obbjjeeccttiivvee:: One of the major causes of death in end-stage renal disease (ESRD) patients under maintenance hemodialysis (HD) is ventricular arrhythmias (VA). Heart rate variability (HRV) has been claimed to be related to disturbance of autonomic nervous system and therefore a predictor for VA occurrence. The purpose of this study is to evaluate the relationship between the HRV parameters

  17. Coronary Artery Bypass Grafting Is Associated with a Significant Worsening of QT Dynamicity and Heart Rate Variability

    Microsoft Academic Search

    Bunyamin Yavuz; Umit Duman; Gulcan Abali; Omer Faruk Dogan; Alkin Yazicioglu; Levent Sahiner; Kudret Aytemir; Lale Tokgozoglu; Metin Demircin; Nasih Nazli; Giray Kabakci; Ali Oto

    2006-01-01

    Background: Imbalance in autonomic nervous system and impaired myocardial repolarization has been shown to increase the risk for arrhythmias in patients with coronary artery disease. This study evaluated the effects of coronary artery bypass grafting (CABG) on heart rate variability and QT interval dynamicity in subjects with coronary artery disease undergoing elective CABG surgery. Methods: The study group consisted of

  18. Variable rate, multi-format receiver design for 10 to 40 Gb/s DPSK and OOK formats.

    PubMed

    Christen, L; Lizé, Y; Nuccio, S; Willner, A E; Paraschis, L

    2008-03-17

    We demonstrate a continuously-variable bit-rate receiver from 10 to 40 Gbit/s for DPSK demodulation. Unlike previous DPSK demodulators, this receiver is also capable of passing intensity modulated waveforms without distortion. Degradations imposed by receiver imperfections are presented and compared with a traditional DPSK delay-line interferometer. PMID:18542478

  19. HEART RATE VARIABILITY SIGNAL PARAMETERS QUANTIFY SKIN COOLING EFFECT OF ENERGY PATCHES DURING REST AND EXERCISE IN YOUNG HEALTHY INDIVIDUALS

    Microsoft Academic Search

    Homer Nazeran

    Heart rate variability (HRV) signal analysis provid es a non-invasive and sensitive marker of autonomic nervous system (ANS) activity. Spectral parameters of HRV signal are used to quantify the balance between sym pathetic and parasympathetic (sympathovagal) influences under various physiologic conditions. ECG signals were acquired, filtered and further processed to derive the HRV signal. The low frequency (LF), high frequ

  20. Depression, Comorbid Anxiety Disorders, and Heart Rate Variability in Physically Healthy, Unmedicated Patients: Implications for Cardiovascular Risk

    Microsoft Academic Search

    Andrew H. Kemp; Daniel S. Quintana; Kim L. Felmingham; Slade Matthews; Herbert F. Jelinek

    2012-01-01

    ContextThere is evidence that heart rate variability (HRV) is reduced in major depressive disorder (MDD), although there is debate about whether this effect is caused by medication or the disorder per se. MDD is associated with a two to fourfold increase in the risk of cardiac mortality, and HRV is a robust predictor of cardiac mortality; determining a direct link