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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

A NEW VARIABLE FLOW RATE NOZZLE FOR AERIAL APPLICATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new variable flow rate nozzle for aerial application, VeriRate Nozzle, has been developed and marketed. The unique design of the nozzle provides for a wide range of flow rates with changes in spray pressure while maintaining droplet size and spray angle. The design is a combination of a flexible...

3

Assessment of the varitarget nozzle for variable rate application of liquid crop protection products.  

E-print Network

??Traditionally, growers spray uniform application of pesticides over the target area regardless of variations in pest infestations. In recent years, variable rate application (VRA) technologies… (more)

Daggupati, Naga Prasad

2007-01-01

4

Basic notions of heart rate variability and its clinical applicability  

Microsoft Academic Search

Autonomic nervous system (ANS) plays an important role in the regulation of the physiological processes of the human organism during normal and pathological conditions. Among the techniques used in its evaluation, the heart rate variability (HRV) has arising as a simple and non-invasive measure of the autonomic impulses, representing one of the most promising quantitative markers of the autonomic balance.

Luiz Carlos; Marques VANDERLEI; Carlos Marcelo PASTRE; Rosângela Akemi HOSHI; Moacir Fernandes de GODOY

2009-01-01

5

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 ...

6

Mathematical 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 ...

7

Crop Sensors for Variable-Rate Nitrogen Application to Cotton  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cotton yield can be very responsive to nitrogen fertilizer. However, over-application of N can result in excess vegetative growth, which can delay maturity and increase the need for growth regulator, defoliant, and insecticide, in addition to wasting money on fertilizer that does not produce a retu...

8

A variable rate speech compressor for mobile applications  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

9

Application uniformity of a commercial center pivot variable rate irrigation system  

Technology Transfer Automated Retrieval System (TEKTRAN)

With the advent of commercial variable rate irrigation (VRI) systems, there is a great interest in using them to improve water use efficiency, implement deficit irrigation strategies in water limited regions and manage water applications for many other important objectives. Multiple catch can trials...

10

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

Microsoft Academic Search

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

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

11

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

E-print Network

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

Arzeno, Natalia M. (Natalia María Arzeno Soltero)

2007-01-01

12

Variable Rate Application of Nematicides on Cotton Fields: A Promising Site-Specific Management Strategy  

PubMed Central

Field tests were conducted to determine if differences in response to nematicide application (i.e., root-knot nematode (RKN) populations, cotton yield, and profitability) occurred among RKN management zones (MZ). The MZ were delineated using fuzzy clustering of five terrain (TR) and edaphic (ED) field features related to soil texture: apparent soil electrical conductivity shallow (ECa-shallow) and deep (ECa-deep), elevation (EL), slope (SL), and changes in bare soil reflectance. Zones with lowest mean values of ECa- shallow, ECa- deep, NDVI, and SL were designated as at greater risk for high RKN levels. Nematicide-treated plots (4 rows wide and 30 m long) were established in a randomized complete block design within each zone, but the number of replications in each zone varied from four to six depending on the size of the zone.The nematicides aldicarb (Temik 15 G) and 1,3-dichloropropene (1,3-D,Telone II) were applied at two rates (0.51 and 1.0 kg a.i./ha for aldicarb, and 33.1 and 66.2 kg a.i./ha for 1,3-D) to RKN MZ in commercial fields between 2007 and 2009. A consolidated analysis over the entire season showed that regardless of the zone, there were not differences between aldicarb rates and 1,3-D rates. The result across zones showed that 1,3-D provided better RKN control than did aldicarb in zones with low ECa values (high RKN risk zones exhibiting more coarse-textured sandy soils). In contrast, in low risk zones with relatively higher ECa values (heavier textured soil), the effects of 1,3-D and aldicarb were equal and application of any of the treatments provided sufficient control. In low RKN risk zones, a farmer would often have lost money if a high rate of 1,3-D was applied. This study showed that the effect of nematicide type and rate on RKN control and cotton yield varied across management zones (MZ) with the most expensive treatment likely to provide economic benefit only in zones with coarser soil texture. This study demonstrates the value of site specific application of nematicides based on management zones, although this approach might not be economically beneficial in fields with little variability in soil texture. PMID:23482903

Ortiz, Brenda V.; Perry, Calvin; Sullivan, Dana; Lu, Ping; Kemerait, Robert; Davis, Richard F.; Smith, Amanda; Vellidis, George; Nichols, Robert

2012-01-01

13

Variable rate application of nematicides on cotton fields: a promising site-specific management strategy.  

PubMed

Field tests were conducted to determine if differences in response to nematicide application (i.e., root-knot nematode (RKN) populations, cotton yield, and profitability) occurred among RKN management zones (MZ). The MZ were delineated using fuzzy clustering of five terrain (TR) and edaphic (ED) field features related to soil texture: apparent soil electrical conductivity shallow (ECa-shallow) and deep (ECa-deep), elevation (EL), slope (SL), and changes in bare soil reflectance. Zones with lowest mean values of ECa- shallow, ECa- deep, NDVI, and SL were designated as at greater risk for high RKN levels. Nematicide-treated plots (4 rows wide and 30 m long) were established in a randomized complete block design within each zone, but the number of replications in each zone varied from four to six depending on the size of the zone.The nematicides aldicarb (Temik 15 G) and 1,3-dichloropropene (1,3-D,Telone II) were applied at two rates (0.51 and 1.0 kg a.i./ha for aldicarb, and 33.1 and 66.2 kg a.i./ha for 1,3-D) to RKN MZ in commercial fields between 2007 and 2009. A consolidated analysis over the entire season showed that regardless of the zone, there were not differences between aldicarb rates and 1,3-D rates. The result across zones showed that 1,3-D provided better RKN control than did aldicarb in zones with low ECa values (high RKN risk zones exhibiting more coarse-textured sandy soils). In contrast, in low risk zones with relatively higher ECa values (heavier textured soil), the effects of 1,3-D and aldicarb were equal and application of any of the treatments provided sufficient control. In low RKN risk zones, a farmer would often have lost money if a high rate of 1,3-D was applied. This study showed that the effect of nematicide type and rate on RKN control and cotton yield varied across management zones (MZ) with the most expensive treatment likely to provide economic benefit only in zones with coarser soil texture. This study demonstrates the value of site specific application of nematicides based on management zones, although this approach might not be economically beneficial in fields with little variability in soil texture. PMID:23482903

Ortiz, Brenda V; Perry, Calvin; Sullivan, Dana; Lu, Ping; Kemerait, Robert; Davis, Richard F; Smith, Amanda; Vellidis, George; Nichols, Robert

2012-03-01

14

Comparison of Variable and Single-Rate Applications of Aldicarb on Cotton Yield in Fields Infested with Meloidogyne incognita  

PubMed Central

Variable-rate applications of the nematicide aldicarb were compared to producer standard rates in eight field tests over 3 years. Test areas (308 to 1,015 m long) were divided into eight or five blocks. Each block contained two plots with a variable-rate treatment (VRT) of aldicarb and a producer standard treatment (PST) of aldicarb. Each VRT plot was divided into three subunits and intensively sampled for Meloidogyne incognita in either the fall or spring before planting. Rates of aldicarb were assigned to each subunit for VRT based on M. incognita population density. In three of the eight tests, VRT resulted in either higher yield or similar yields, but less nematicide applied. In two tests there were no differences between PST and VRT in yields or average rates of aldicarb applied. In three tests, VRT used more aldicarb (>0.17 kg a.i./ha difference) than PST and yields were not significantly different between treatments. In two of the cases where VRT was superior to PST, the producer's rate of aldicarb was judged to be either too low or too high for the average M. incognita density present in the field. In all three cases where PST was superior to VRT, perennial weeds were an important factor also limiting yield. Variable-rate application of aldicarb did not consistently provide for higher yields or lower nematicide usage than standard application rates. PMID:19270939

Wheeler, T. A.; Kaufman, H. W.; Baugh, B.; Kidd, P.; Schuster, G.; Siders, K.

1999-01-01

15

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

Microsoft Academic Search

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.

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

2000-01-01

16

Variable rate application of nematicides on cotton fields: A promising site-specific management strategy.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Field tests were conducted to determine if differences in response to nematicide application (i.e., root-knot nematode (RKN) population levels, cotton yield, and profitability) occurred among RKN management zones (MZ). The MZ were delineated using variables related to soil texture, including appare...

17

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...

18

DESCRIPTION OF A HIGH-CLEARANCE APPLICATOR FOR MAKING VARIABLE RATE N APPLICATIONS TO CORN USING ACTIVE SENSOR READINGS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A major factor contributing to low nitrogen (N) use efficiency and environmental contamination for traditional corn N management schemes is routine application of large and uniform doses of N to spatially variable landscapes, before when the crop can effectively utilize N. Our long-term research goa...

19

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

20

[Application of power spectral analysis of heart rate variability to women with climacteric symptoms].  

PubMed

Climacteric symptoms are multiple syndromes in menopausal women. It is known that autonomic nervous activity disorder plays an important role in these symptoms. In the present brief review, we report our recent studies of the relation between climacteric symptoms and autonomic nervous system balance measured by power spectral analysis of heart rate variability (HRV) using a standard hexagon radar chart. The sympathetic excitability and irritability, and the standard deviation of mean R-R intervals in the supine position were significantly decreased in women with climacteric symptoms compared to control women without climacteric symptoms. There was a negative correlation (r = -0.363, P = 0.0167) between the standard deviation of mean R-R intervals in the supine position and the simplified menopausal index score. These results show suggest a close relation between climacteric symptoms and autonomic nervous activities, and our power spectral analysis of HRV, which provides a standard hexagonal radar chart composed of three sympathetic and three parasympathetic parameters, may be helpful in the diagnosis and treatment of climacteric symptoms in menopausal women. PMID:25224709

Yanagihara, Nobuyuki; Seki, Meikan; Goto, Yukio; Hachisuga, Toru; Nakano, Masahiro

2014-09-01

21

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...

22

The sensitivity of the epidemic growth rate to weather variables, with an application to yellow rust on wheat.  

PubMed

ABSTRACT We first show how to estimate the exponential epidemic growth rate, r, for different combinations of three weather variables. Then we derive a method to quantify the sensitivity of r to a weather variable as a function of the pathogen life cycle variables of latent period, basic reproductive number, and the mean and standard deviation of the sporulation curve. The method can be used to identify the most important weather variable and pathogen life cycle component in terms of epidemic progress. The method is applied to yellow rust, caused by Puccinia striiformis, on winter wheat. We conclude that the most important weather variable for the progress of yellow rust is temperature, followed by dew period and light quantity. By far, the most important pathogen life cycle component is the basic reproductive number, especially at low and high temperatures. This disagrees with the general view that latent period is the most important variable at low temperatures. We discuss explanations of this. PMID:18944376

Papastamati, Konstantina; van den Bosch, Frank

2007-02-01

23

Heart rate variability: a review  

Microsoft Academic Search

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

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

2006-01-01

24

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 ...

25

Variability of Plasmaspheric Rotation Rate  

NASA Astrophysics Data System (ADS)

The plasmasphere has been observed to rotate at a rate different than that of the Earth itself. Previous studies such as Burch et al. [2003] have linked plasmaspheric sub-corotation to joule heating of the polar ionosphere during periods of high geomagnetic activity, and have supported it with an individual case study observation. We carry out a statistical survey of plasmaspheric rotation rates over several months of IMAGE EUV data in 2001, correlating the results with geomagnetic indices. An automated cross-correlation routine is used to track azimuthal features such as "notches" over a single pass of the IMAGE satellite, providing an estimate of the plasmasphere's rotation rate. Observed trends and possible causes of the variability of rotation rate are discussed.

Galvan, D. A.; Moldwin, M. B.; Sandel, B. R.

2008-05-01

26

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...

27

PERFORMANCE OF A VARIABLE RATE CENTER PIVOT SYSTEM  

Technology Transfer Automated Retrieval System (TEKTRAN)

US farmers have access to equipment for variable-rate application of most inputs, but some potential benefits of precision agriculture may be masked by uniform application of irrigation water. A system developed at the University of Georgia for variable-rate (VR) water application was installed on a...

28

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

29

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

PubMed

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

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

2014-07-01

30

CANONICAL CORRELATION ANALYSIS BETWEEN TIME SERIES AND STATIC OUTCOMES, WITH APPLICATION TO THE SPECTRAL ANALYSIS OF HEART RATE VARIABILITY  

PubMed Central

Although many studies collect biomedical time series signals from multiple subjects, there is a dearth of models and methods for assessing the association between frequency domain properties of time series and other study outcomes. This article introduces the random Cramér representation as a joint model for collections of time series and static outcomes where power spectra are random functions that are correlated with the outcomes. A canonical correlation analysis between cepstral coefficients and static outcomes is developed to provide a flexible yet interpretable measure of association. Estimates of the canonical correlations and weight functions are obtained from a canonical correlation analysis between the static outcomes and maximum Whittle likelihood estimates of truncated cepstral coefficients. The proposed methodology is used to analyze the association between the spectrum of heart rate variability and measures of sleep duration and fragmentation in a study of older adults who serve as the primary caregiver for their ill spouse. PMID:24851143

Krafty, Robert T.; Hall, Martica

2014-01-01

31

Rater variables associated with ITER ratings.  

PubMed

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

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

2013-10-01

32

Deconvolution of variable rate reservoir performance data using B-splines  

E-print Network

This work presents the development, validation and application of a novel deconvolution method based on B-splines for analyzing variable-rate reservoir performance data. Variable-rate deconvolution is a mathematically unstable problem which has been...

Ilk, Dilhan

2007-04-25

33

Rater Variables Associated with ITER Ratings  

ERIC Educational Resources Information Center

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

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

2013-01-01

34

HEART RATE VARIABILITY AND 24-HOUR MINIMUM HEART RATE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Heart rate variability (HRV) indices based on 24-hour electrocardiograph recordings have been used in clinical research studies to assess the aggregate activity of the autonomic nervous system. While 24-hour HRV is generally considered non-invasive, use in research protocols typically involves cons...

35

Gaussian Mixture Model of Heart Rate Variability  

PubMed Central

Heart rate variability (HRV) is an important measure of sympathetic and parasympathetic functions of the autonomic nervous system and a key indicator of cardiovascular condition. This paper proposes a novel method to investigate HRV, namely by modelling it as a linear combination of Gaussians. Results show that three Gaussians are enough to describe the stationary statistics of heart variability and to provide a straightforward interpretation of the HRV power spectrum. Comparisons have been made also with synthetic data generated from different physiologically based models showing the plausibility of the Gaussian mixture parameters. PMID:22666386

Costa, Tommaso; Boccignone, Giuseppe; Ferraro, Mario

2012-01-01

36

Fluid/Vapor Separator for Variable Flow Rates  

NASA Technical Reports Server (NTRS)

Shutter varies gas throughput of porous plug. Variable area exposed on porous plug allows to pass varying rates of vapor flow while blocking flow of liquid helium II from cryogenic bath. Applications in refining operations, industrial chemistry, and steam-powered equipment.

Lee, J. M.; Chuang, C.; Frederking, T. H.; Brown, G. S.; Kamioka, Y.; Vorreiter, J.

1984-01-01

37

Sigh rate and respiratory variability during mental load Journal: Psychophysiology  

E-print Network

Sigh rate and respiratory variability during mental load Journal: Psychophysiology Manuscript ID;Sigh rate and respiratory variability during mental arithmetic - 1 - RUNNING HEAD: SIGH RATE AND RESPIRATORY VARIABILITY Sigh rate and respiratory variability during mental load Elke Vlemincx Research Group

38

Within-field variability in optimum nitrogen rate for corn linked to soil moisture variability  

Technology Transfer Automated Retrieval System (TEKTRAN)

Understanding the interaction between yield response to N and other growth-limiting factors is essential to improving spatially dependent N fertilizer applications. Our objective was to evaluate the impact of soil water content variability on the economic optimum N rate (EONR) for corn (Zea mays L.)...

39

Heart Rate Variability – A Historical Perspective  

PubMed Central

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

Billman, George E.

2011-01-01

40

A numerical model prediction for boiling multi channel flow rate distribution and application in 600MW supercritical variable-pressure once-through boiler with vertical tube coils  

NASA Astrophysics Data System (ADS)

Flow rate distribution is important in a multi channel system when the flow is heated non-uniformly. This paper describes a steady state approach for obtaining the flow distribution among various tubes of complex multi channel system. Based on the present approach, a program has been developed, which is directly applied in thermal hydraulic design and investigation of 600MW supercritical variable-pressure once through boiler.

Chen, Tingkuan; Xu, Jinliang; Wu, Lucheng

1996-04-01

41

Heart rate variability to assess combat readiness.  

PubMed

Chronic fatigue/physical exhaustion (FPE) impacts combat readiness but is difficult to identify. We tested the hypothesis that resting heart rate variability (HRV), including both time- and frequency-domain assessments, would correlate with hydration status and aerobic capacity in military recruit-age men and women with varying fitness levels. Cardiac interbeat intervals were recorded using a heart R-R monitor during 20 minutes of quiet, supine rest with paced breathing (0.25 Hz). HRV metrics included average R-R interval (RRIavg), R-R interval standard deviation (RRISD), the percentage of adjacent R-R intervals varying by > or = 50 ms (pNN50), and integrated areas of R-R interval spectral power at the high (0.15-0.4 Hz) (RRIHF) and low (0.04-0.15 Hz) (RRILF) frequencies. Treadmill maximal oxygen uptake (VO2 max), segmental bioimpedance estimates of total body water (TBW), and urine specific gravity (USG) were also assessed. All dependent variables of interest were within expected ranges, although absolute ranges of individual values were considerable. RRI correlated with VO2 max (r = 0.49; p < 0.001), with TBW (r = 0.38; p < 0.001), and inversely with USG (r = -0.23; p = 0.02). RRISD correlated with VO2 max (r = 0.21; p = 0.03), but not with TBW or USG. pNN50 correlated inversely with USG (r = -0.21; p = 0.03) but not with VO2 max or TBW. R-R interval spectral power at the high and low frequencies did not correlate with VO2 max, TBW, or USG. We have demonstrated that fitness level and hydration status may affect cardiac function via changes in autonomic tone, highlighting the potential of field-based assessment of heart rate variability metrics to identify FPE and other aspects of combat readiness. PMID:20731279

Fogt, Donovan L; Cooper, Paige J; Freeman, Christine N; Kalns, John E; Cooke, William H

2009-05-01

42

Soil variability in engineering applications  

NASA Astrophysics Data System (ADS)

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

Vessia, Giovanna

2014-05-01

43

The Impact of Soil Sampling Errors on Variable Rate Fertilization  

SciTech Connect

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

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

2004-07-01

44

gHRV: Heart rate variability analysis made easy.  

PubMed

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

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

2014-08-01

45

Erosion rate variability in steady state landscapes: sources  

E-print Network

Erosion rate variability in steady state landscapes: sources and implications Les Hasbargen Chris Erosion rate variability is: · Strong (order 1 variability) · Autogenic at steady forcing · Spatially organized · Topographically recognizable in the landscape #12;Erosion facility to water supply rainfall (r

Paola, Chris

46

An efficient software implementation of a variable rate modem  

NASA Technical Reports Server (NTRS)

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.

Mantha, Ramesh; Hunt, Andrew; Crozier, Stewart

1995-01-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

48

VARIABILITY IN MEASURED BEDLOAD-TRANSPORT RATES.  

USGS Publications Warehouse

During a four-day period of nearly constant water discharge, four sets of consecutively collected bedload samples, ranging from 43 to 120 samples, were obtained at the same cross channel location using a standard 65-pound Helley-Smith bedload sampler. When the measured transport rates are converted to dimensionless rates and plotted as cumulative frequency distributions, they show good agreement with a theoretical probability distribution function of rates derived for the case of ripples on dunes. The distributions show that during constant water discharge individual measured rates at a fixed point vary from near zero to four times the mean rate, and 60 percent of the sampled rates will be less than the mean.

Carey, William P.

1985-01-01

49

Wearable depression monitoring system with heart-rate variability.  

PubMed

A wearable depression monitoring system is proposed with an application-specific system-on-chip (SoC) solution. The SoC is designed to accelerate the filtering and feature extraction of heart-rate variability (HRV) from the electrocardiogram (ECG). Thanks to the SoC solution and planar-fashionable circuit board (P-FCB), the monitoring system becomes a low-power wearable system. Its dimension is 14cm × 7cm with 5mm thickness covering the chest band for convenient usage. In addition, with 3.7V 500mAh battery, its lifetime is at least 10 hours. For user's convenience, the system is interfacing to smart phones through Bluetooth communication. With the features of the HRV and Beck depression inventory (BDI), the smart phone application trains and classifies the user's depression scale with 71% of accuracy. PMID:25570021

Roh, Taehwan; Sunjoo Hong; Hoi-Jun Yoo

2014-08-01

50

Heart rate variability in mice with coronary heart disease  

E-print Network

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

Zapanta, Laurence (Laurence F.)

2005-01-01

51

[Some regularities of the pulse rate variability].  

PubMed

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

Dudin, S A; Zandanova, G I

2011-01-01

52

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

PubMed

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

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

2014-07-01

53

Hybrid Companding Delta Modulation with Variable-Rate Sampling  

Microsoft Academic Search

Hybrid companding delta modulation (HCDM) is known to be superior in performance to other instantaneous or syllabic companding delta modulation systems [1]. To improve its performance or to reduce the bit rate further in coding speech, we propose to use a variable-rate sampling scheme in the HCDM system. The proposed system employs several different sampling rates but transmits the output

Chong Un; Dong Cho

1982-01-01

54

Noncontact imaging photoplethysmography to effectively access pulse rate variability  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

55

Method of Discriminant Gravity Tolerance using Heart Rate Variability  

NASA Astrophysics Data System (ADS)

When returning on the earth by the space flight, the space deconditioning may be developed. As this countermeasure, the artificial gravity load device using the centrifuge is proposed in the space station. But the gravity load might cause the faint, and safe gravity load is uncertainty. We proposed that discriminate strength of gravity tolerance using heart rate variability time series. Step function was inputted to AR model estimated from heart rate variability time series during rest or under light gravity load, and strength of the gravity tolerance was discriminated by the step response function. On the result, discriminant accuracy was 87.5% by using heart rate variability time series when gravity load of 1.0 G was added to the human lying on the supine. Therefore, possibility of discriminant of gravity tolerance was obtained by using heart rate variability time series when sympathetic hyperactivity. Discriminant of the gravity tolerance is expected before countermeasure of space deconditioning is executed.

Yoshida, Yutaka; Yokoyama, Kiyoko; Takada, Hiroki; Iwase, Satoshi

56

High-bit-rate continuous-variable quantum key distribution  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

57

Variable-rate coding for meteor-burst communications  

Microsoft Academic Search

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

M. B. Pursley; S. D. Sandberg

1989-01-01

58

Heart rate variability associated with particulate air pollution  

Microsoft Academic Search

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

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

1999-01-01

59

Some theoretical results in variable-rate optical communications.  

NASA Technical Reports Server (NTRS)

Review of several variable-rate optical transmission schemes over an earth-to-space link which neutralize the effects of atmospheric turbulence. These adaptive laser communication systems exploit atmospheric reciprocity and the relatively long coherence time of the turbulence to monitor the time-varying state of the earth-to-space channel by using a satellite beacon and making appropriate measurements at the ground terminal. Optimal variable-rate strategy based on this channel-state information results is considerably improved performance in comparison with nonadaptive optical communication systems.

Levitt, B. K.

1972-01-01

60

Heart rate variability interventions for concussion and rehabilitation  

PubMed Central

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

Conder, Robert L.; Conder, Alanna A.

2014-01-01

61

Two-Stage Variable Sample-Rate Conversion System  

NASA Technical Reports Server (NTRS)

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

Tkacenko, Andre

2009-01-01

62

Variability of Lekanesphaera monodi metabolic rates with habitat trophic status  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

63

Heart Rate Variability and Drawing Impairment in Hypoxemic COPD  

ERIC Educational Resources Information Center

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

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

2009-01-01

64

Heart Rate Variability: Effect of Exercise Intensity on Postexercise Response  

ERIC Educational Resources Information Center

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

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

2012-01-01

65

Adoption of site-specific variable rate sprinkler irrigation systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

More than twenty years of private and public research on site-specific variable-rate sprinkler irrigation (SS-VRI) technology has resulted in limited commercial adoption of the technology. Competing patents, liability and proprietary software have affected industry’s willingness to move into a new t...

66

Extracting heart rate variability from a wearable reflectance pulse oximeter  

Microsoft Academic Search

The effectiveness and efficiency of combat medics can be greatly improved by increasing the speed and precision with which physiological information is gathered from wounded soldiers. In this paper we demonstrate the feasibility of extracting accurate heart rate variability (HRV) measurements from photoplethysmographic (PPG) signals recorded by a reflectance-mode pulse oximeter sensor attached to the forehead.

W. Johnston; Y. Mendelson

2005-01-01

67

Assessing variability by joint sampling of alignments and mutation rates  

E-print Network

Assessing variability by joint sampling of alignments and mutation rates Dirk Metzler Roland with a single set of alignment para- meters, or when mutation parameters are estimated on the basis of a single sampling sequence alignments and mutation parameters simultaneously from their joint poste- rior

Wakolbinger, Anton

68

Enhancing adoption of site-specific variable rate sprinkler systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

More than twenty years of private and public research on site-specific variable-rate sprinkler irrigation (SS-VRI) has resulted in very limited commercial adoption of the technology. Documented and proven water conservation strategies using site-specific irrigation are quite limited, and its cost-ef...

69

Aggregation of Variables and System Decomposition: Applications  

E-print Network

that the aggregate variable descriptions of mutation-selection systems offer a potential formal definition of units decomposi- tion operators. It is also shown that equitable partitions have a natural application to the description of mutation-selection matrices (fitness landscapes) when their fitness functions have certain

Stadler, Peter F.

70

Efficient delivery techniques for variable-bit-rate multimedia  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

71

Variable rate fertilization based on spectral index and remote sensing  

NASA Astrophysics Data System (ADS)

Variable rate fertilization can meet the needs of crop growth with low pollution of the environment resulted in by excess fertilization, and has therefore become an important part of precision agriculture. Variable rate fertilization requires a precise access to growing crops and spatial distribution. It is the key to precision agriculture technology in accessing the crop information based on spectroscopy and remote sensing technologies. This paper outlines our efforts to find a way to combine the information of growth with the spatial location information in a common way. Ground-based Remote Sensing Instrument GreenSeeker is used to analyze the biological characteristics of winter wheat in the spatial variability. The experiments are conducted during the period of rviving, early jointing, and late jointing. The measurement result is calculated according to GreenSeeker canopy NDVI data and the canopy chlorophyll content is obtained by using laboratory analysis. The analysis of NDVI data of canopy leaves and chlorophyll content and spatial distribution trends shows that the NDVI data of canopy are influenced by environmental factors such as the surface coverage during the period of reviving. The data of chlorophyll are at a low level and quite different at region distribution. As the wheat growth stage changes, the spatial variability and the chlorophyll content are going to decrease, and in more evenly distributed. It is proved that the analysis of spatial distribution can accurately grasp the biological characteristics and distribution information of the winter wheat in experimental area, and provide the basis for variable management.

Li, Shuqiang; Li, Minzan; Ding, Yongjun; Zhao, Ruijiao

2010-11-01

72

Heart rate variability in normal and pathological sleep  

PubMed Central

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

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

2013-01-01

73

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

Microsoft Academic Search

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

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

2000-01-01

74

Assessment of pulse rate variability by the method of pulse frequency demodulation  

Microsoft Academic Search

BACKGROUND: Due to its easy applicability, pulse wave has been proposed as a surrogate of electrocardiogram (ECG) for the analysis of heart rate variability (HRV). However, its smoother waveform precludes accurate measurement of pulse-to-pulse interval by fiducial-point algorithms. Here we report a pulse frequency demodulation (PFDM) technique as a method for extracting instantaneous pulse rate function directly from pulse wave

Junichiro Hayano; Allan Kardec Barros; Atsunori Kamiya; Nobuyuki Ohte; Fumihiko Yasuma

2005-01-01

75

Direct observation of homoclinic orbits in human heart rate variability  

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

76

Qigong Effects on Heart Rate Variability and Peripheral Vasomotor Responses.  

PubMed

Population aging is occurring worldwide, and preventing cardiovascular event in older people is a unique challenge. The aim of this study was to examine the effects of a 12-week qigong (eight-form moving meditation) training program on the heart rate variability and peripheral vasomotor response of middle-aged and elderly people in the community. This was a quasi-experimental study that included the pre-test, post-test, and nonequivalent control group designs. Seventy-seven participants (experimental group = 47; control group = 30) were recruited. The experimental group performed 30 min of eight-form moving meditation 3 times per week for 12 weeks, and the control group continued their normal daily activities. After 12 weeks, the interaction effects indicated that compared with the control group, the experimental group exhibited significantly improved heart rate variability and peripheral vasomotor responses. PMID:24869492

Chang, Mei-Ying

2014-05-27

77

Solutions of two-factor models with variable interest rates  

NASA Astrophysics Data System (ADS)

The focus of this work is on numerical solutions to two-factor option pricing partial differential equations with variable interest rates. Two interest rate models, the Vasicek model and the Cox-Ingersoll-Ross model (CIR), are considered. Emphasis is placed on the definition and implementation of boundary conditions for different portfolio models, and on appropriate truncation of the computational domain. An exact solution to the Vasicek model and an exact solution for the price of bonds convertible to stock at expiration under a stochastic interest rate are derived. The exact solutions are used to evaluate the accuracy of the numerical simulation schemes. For the numerical simulations the pricing solution is analyzed as the market completeness decreases from the ideal complete level to one with higher volatility of the interest rate and a slower mean-reverting environment. Simulations indicate that the CIR model yields more reasonable results than the Vasicek model in a less complete market.

Li, Jinglu; Clemons, C. B.; Young, G. W.; Zhu, J.

2008-12-01

78

Efficient delivery techniques for variable-bit-rate multimedia  

Microsoft Academic Search

Two key technologies enabling scalable on-demand delivery of stored multimedia content are work-ahead smoothing and multicast delivery. Work-ahead smoothing reduces the burstiness of variable bit rate streams, simplifying server and network resource allocation. Recent multicast delivery techniques such as patching or bandwidth skimming serve clients that request the same content close together in time with (partially) shared multicasts, greatly reducing

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

2001-01-01

79

Efficient Delivery Techniques for Variable Bit Rate Multimedia  

Microsoft Academic Search

Two key technologies enabling scalable on-demand delivery of stored multimedia content are work-ahead smoothing and multicast delivery. Work-ahead smoothing reduces the burstiness of variable bit rate streams, simplifying server and network resource allocation. Recent multicast delivery techniques such as patching or bandwidth skimming serve clients that request the same content close together in time with (partially) shared multicasts, greatly reducing

Yanping Zhao; Derek Eager; Mary Vernon

2002-01-01

80

Heart Rate Variability and Disease Characteristics in Patients with COPD  

Microsoft Academic Search

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

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

2008-01-01

81

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)...

82

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

Microsoft Academic Search

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

François Cottin; François Durbin; Yves Papelier

2004-01-01

83

Heart Rate Variability in Sleep-Related Migraine without Aura  

PubMed Central

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

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

2013-01-01

84

Heart rate variability analysis during central hypovolemia using wavelet transformation.  

PubMed

Detection of hypovolemia prior to overt hemodynamic decompensation remains an elusive goal in the treatment of critically injured patients in both civilian and combat settings. Monitoring of heart rate variability has been advocated as a potential means to monitor the rapid changes in the physiological state of hemorrhaging patients, with the most popular methods involving calculation of the R-R interval signal's power spectral density (PSD) or use of fractal dimensions (FD). However, the latter method poses technical challenges, while the former is best suited to stationary signals rather than the non-stationary R-R interval. Both approaches are also limited by high inter- and intra-individual variability, a serious issue when applying these indices to the clinical setting. We propose an approach which applies the discrete wavelet transform (DWT) to the R-R interval signal to extract information at both 500 and 125 Hz sampling rates. The utility of machine learning models based on these features were tested in assessing electrocardiogram signals from volunteers subjected to lower body negative pressure induced central hypovolemia as a surrogate of hemorrhage. These machine learning models based on DWT features were compared against those based on the traditional PSD and FD, at both sampling rates and their performance was evaluated based on leave-one-subject-out fold cross-validation. Results demonstrate that the proposed DWT-based model outperforms individual PSD and FD methods as well as the combination of these two traditional methods at both sample rates of 500 Hz (p value <0.0001) and 125 Hz (p value <0.0001) in detecting the degree of hypovolemia. These findings indicate the potential of the proposed DWT approach in monitoring the physiological changes caused by hemorrhage. The speed and relatively low computational costs in deriving these features may make it particularly suited for implementation in portable devices for remote monitoring. PMID:23371800

Ji, Soo-Yeon; Belle, Ashwin; Ward, Kevin R; Ryan, Kathy L; Rickards, Caroline A; Convertino, Victor A; Najarian, Kayvan

2013-06-01

85

Heart rate variability in children with type 1 diabetes mellitus  

PubMed Central

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

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

2014-01-01

86

Kramers-Moyal Expansion of Heart Rate Variability  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

87

Variable beam dose rate and DMLC IMRT to moving body anatomy  

SciTech Connect

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

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

2008-11-15

88

Music structure determines heart rate variability of singers.  

PubMed

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

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

2013-01-01

89

Music structure determines heart rate variability of singers  

PubMed Central

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

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

2013-01-01

90

Complex character analysis of heart rate variability following brain asphyxia.  

PubMed

In the present study Renyi entropy and L-Z complexity were used to characterize heart rate variability (HRV) of rats that were suffered from brain asphyxia and ischemia. Two groups of rats were studied: (a) rats (n=5) injected with NAALADase inhibitor, 2-PMPA, which has been proven neuroprotective in asphyxia injury and (b) control subjects (n=5) without medication. Renyi entropy and L-Z complexity of the R-R intervals (RRI) at different experiment stages were investigated in the two groups. The results show that both measures indicate less injury and better recovery in the drug injection group. The dynamic change of 90 min RRI signal after the asphyxia was investigated. The sudden reduction of the two parameters shows their sensitivity to the asphyxia insult. PMID:16129646

Cai, Yuanyuan; Qiu, Yihong; Wei, Lan; Zhang, Wei; Hu, Sijun; Smith, Peter R; Crabtree, Vincent P; Tong, Shanbao; Thakor, Nitish V; Zhu, Yisheng

2006-05-01

91

12 CFR 1026.19 - Certain mortgage and variable-rate transactions.  

Code of Federal Regulations, 2013 CFR

...variable-rate transactions. 1026.19 Section 1026.19 Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION TRUTH IN LENDING (REGULATION Z) Closed-End Credit § 1026.19 Certain mortgage and variable-rate transactions....

2013-01-01

92

Repolarisation descriptors and heart rate variability in hemodialyzed patients.  

PubMed

T wave morphology (TWM) descriptors derived from Holter electrocardiograms during hemodialysis (HD) are of potential value for cardiac risk assessment in HD patients. Our knowledge on autonomic regulation of TWM descriptors is limited. The purpose of this study was to investigate the association between TWM parameters and heart rate variability (HRV) during intradialytic monitoring. In each of 81 patients on maintenance HD, continuous electrocardiograms were recorded 5 times during HD on alternate weeks. TWM descriptors were calculated every 5 seconds in overlapping 10-second ECG segments and Low Frequency (LF) (0.04 Hz to 0.15 Hz), High Frequency (HF) (0.15 Hz to 0.40 Hz) powers of the spectrum of HRV were calculated every five minutes. The calculated values of TWM and HRV were averaged during the first hour of the recordings and subsequently over all recordings in each subject. Analyzable data for HRV and TWM were available in 71 HD patients (aged 61+/-15, 36 % diabetics, 32 % females). LF in normalized units correlated positively with Total Cosine R to T (r=0.374, p=0.001) and negatively with T wave morphology dispersion (r= -0.253, p=0.033) after adjusting for HR. In conclusion, a heart rate independent association between repolarization descriptors and HRV exists in HD patients. Autonomic modulation needs to be considered when using TWM characteristics for risk profiling of HD patients. PMID:25470516

Poulikakos, D; Banerjee, D; Malik, M

2014-12-01

93

High frequency chest compression effects heart rate variability.  

PubMed

High frequency chest compression (HFCC) supplies a sequence of air pulses through a jacket worn by a patient to remove excessive mucus for the treatment or prevention of lung disease patients. The air pulses produced from the pulse generator propagates over the thorax delivering the vibration and compression energy. A number of studies have demonstrated that the HFCC system increases the ability to clear mucus and improves lung function. Few studies have examined the change in instantaneous heart rate (iHR) and heart rate variability (HRV) during the HFCC therapy. The purpose of this study is to measure the change of HRV with four experimental protocols: (a) without HFCC, (b) during Inflated, (c)HFCC at 6Hz, and (d) HFCC at 21Hz. The nonlinearity and regularity of HRV was assessed by approximate entropy (ApEn), a method used to quantify the complexities and randomness. To compute the ApEn, we sectioned with a total of eight epochs and displayed the ApEn over the each epoch. Our results show significant differences in the both the iHR and HRV between the experimental protocols. The iHR was elevated at both the (c) 6Hz and (d) 21Hz condition from without HFCC (10%, 16%, respectively). We also found that the HFCC system tends to increase the HRV. Our study suggests that monitoring iHR and HRV are very important physiological indexes during HFCC therapy. PMID:18002145

Lee, Jongwon; Lee, Yong W; Warwick, Warren J

2007-01-01

94

From beat rate variability in induced pluripotent stem cell-derived pacemaker cells to heart rate variability in human subjects  

PubMed Central

Background We previously reported that induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CM) manifest beat rate variability (BRV) resembling heart rate variability (HRV) in human sinoatrial node (SAN). We now hypothesized the BRV-HRV continuum originates in pacemaker cells. Objective To investigate whether cellular BRV is a source of HRV dynamics, we hypothesized three-levels of interaction among different cardiomyocyte entities: (1) single pacemaker cells, (2) networks of electrically coupled pacemaker cells and (3) in situ SAN. Methods We measured BRV/HRV properties in single pacemaker cells, iPSC-derived contracting embryoid bodies (EBs) and electrocardiograms from the same individual. Results Pronounced BRV/HRV were present at all three levels. Coefficient of variance (COV) of inter-beat intervals (IBI) and Poincaré plot SD1 and SD2 in single cells were 20x > EBs (P<0.05) and in situ heart (the latter two were similar, P>0.05). We also compared BRV magnitude among single cells, small (~5-10 cells) and larger EBs (>10 cells): BRV indices progressively increased (P<0.05) as cell number decreased. Disrupting intracellular Ca2+ handling markedly augmented BRV magnitude, revealing a unique bi-modal firing pattern, suggesting intracellular mechanisms contribute to BRV/HRV and the fractal behavior of heart rhythm. Conclusions The decreased BRV magnitude in transitioning from single cell to EB suggests HRV of hearts in situ originates from summation and integration of multiple cell-based oscillators. Hence, complex interactions among multiple pacemaker cells and intracellular Ca2+ handling determine HRV in humans and isolated cardiomyocyte networks. PMID:25052725

Barad, Lili; Novak, Atara; Ben-Ari, Erez; Lorber, Avraham; Itskovitz-Eldor, Joseph; Rosen, Michael R; Weissman, Amir; Binah, Ofer

2014-01-01

95

Testing the effect of metabolic rate on DNA variability at the intra-specific level.  

PubMed

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

McGaughran, Angela; Holland, Barbara R

2010-01-01

96

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

PubMed Central

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

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

2013-01-01

97

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

PubMed Central

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

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

2014-01-01

98

Heart rate variability in type 2 diabetes mellitus.  

PubMed

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

Stuckey, Melanie I; Petrella, Robert J

2013-01-01

99

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

PubMed Central

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

Chouchou, Florian; Desseilles, Martin

2014-01-01

100

The relationship between working memory, reinvestment, and heart rate variability.  

PubMed

There is growing evidence illustrating the negative aspects of reinvestment on everyday life, however its underlying mechanisms remain unclear. The main aim of this study was to empirically clarify the relationship between reinvestment and working memory (WM). A secondary aim was to investigate the contribution of high-frequency heart rate variability (HF-HRV) to WM. Sixty-two participants took part in a within-subject design in which we measured their WM capacity in a low-pressure and a high-pressure condition while their HF-HRV was measured. In addition, they had to fill out scales assessing their dispositional reinvestment. Results showed that the correlation between reinvestment and WM is negative, exists only in the high-pressure condition, and is specific to the decision component of reinvestment and not the movement component. Moreover, a hierarchical regression analysis revealed that under high pressure resting HF-HRV predicted WM performance above DSRS, whereas DSRS did not predict WM performance above resting HF-HRV. PMID:25449388

Laborde, Sylvain; Furley, Philip; Schempp, Caroline

2015-02-01

101

Heart rate variability and drawing impairment in hypoxemic COPD.  

PubMed

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

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

2009-06-01

102

Variable-rate selective excitation for rapid MRI sequences.  

PubMed

Balanced steady-state free precession (SSFP) imaging sequences require short repetition times (TRs) to avoid off-resonance artifacts. The use of slab-selective excitations is common, as this can improve imaging speed by limiting the field of view (FOV). However, the necessarily short-duration excitations have poor slab profiles. This results in unusable slices at the slab edge due to significant flip-angle variations or aliasing in the slab direction. Variable-rate selective excitation (VERSE) is a technique by which a time-varying gradient waveform is combined with a modified RF waveform to provide the same excitation profile with different RF power and duration characteristics. With the use of VERSE, it is possible to design short-duration pulses with dramatically improved slab profiles. These pulses achieve high flip angles with only minor off-resonance sensitivity, while meeting SAR limits at 1.5 T. The improved slab profiles will enable more rapid 3D imaging of limited volumes, with more consistent image contrast across the excited slab. PMID:15334579

Hargreaves, Brian A; Cunningham, Charles H; Nishimura, Dwight G; Conolly, Steven M

2004-09-01

103

Extraction of Heart Rate Variability from Smartphone Photoplethysmograms  

PubMed Central

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.

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

2015-01-01

104

Newborn seizure detection based on heart rate variability.  

PubMed

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

Malarvili, M B; Mesbah, Mostefa

2009-11-01

105

Nonlinear control of heart rate variability in human infants.  

PubMed Central

Nonlinear analyses of infant heart rhythms reveal a marked rise in the complexity of the electrocardiogram with maturation. We find that normal mature infants (gestation greater than or equal to 35 weeks) have complex and distinctly nonlinear heart rhythms (consistent with recent reports for healthy adults) but that such nonlinearity is lacking in preterm infants (gestation > or = to 27 weeks) where parasympathetic-sympathetic interaction and function are presumed to be less well developed. Our study further shows that infants with clinical brain death and those treated with atropine exhibit a similar lack of nonlinear feedback control. These three lines of evidence support the hypothesis championed by Goldberger et al. [Goldberger, A.L., Rigney, D.R. & West, B.J. (1990) Sci. Am. 262, 43-49] that autonomic nervous system control underlies the nonlinearity and possible chaos of normal heart rhythms. This report demonstrates the acquisition of nonlinear heart rate dynamics and possible chaos in developing human infants and its loss in brain death and with the administration of atropine. It parallels earlier work documenting changes in the variability of heart rhythms in each of these cases and suggests that nonlinearity may provide additional power in characterizing physiological states. PMID:8637921

Sugihara, G; Allan, W; Sobel, D; Allan, K D

1996-01-01

106

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

PubMed Central

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

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

2013-01-01

107

Sternal pulse rate variability compared with heart rate variabilit on healthy subjects.  

PubMed

The heart rate variability (HRV) is a commonly used method to quantify the sympathetic and the parasympa-thetic modulation of the heart rate. HRV is mainly conducted on electrocardiograms (ECG). However, the use of photo-plethysmography (PPG) as a marker of the autonomic tone is emerging. In this study we investigated the feasibility of deriving pulse rate variability (PRV) using PPG signals recorded by a reflectance PPG sensor attached to the chest bone (sternum) and comparing it to HRV. The recordings were conducted on 9 healthy subjects being in a relaxed supine position and under forced respiration, where the subjects were asked to breathe following a visual scale with a rate of 27 breaths/min. HRV parameters such as the mean intervals (meanNN), the standard deviation of intervals (SDNN), the root mean square of difference of successive intervals (RMSSD), and the proportion of intervals differing more than 50 ms (pNN50) were calculated from the R peak-to-R peak (R-R) and pulse-to-pulse (P-P) intervals. In the frequency domain the low and high frequency ratio of the power spectral density (LF/HF) was also computed. The Pearson correlation coefficient showed significant correlation for all the parameters (r > 0.95 with p <; 0.001) and the Bland-Altmann analysis showed close agreement between the two methods for all the parameters during resting and forced respiration condition. Thus, PRV analysis using sternal PPG can be an alternative to HRV analysis on healthy subjects at. PMID:25570719

Chreiteh, Shadi S; Belhage, Bo; Hoppe, Karsten; Branebjerg, Jens; Thomsen, Erik V

2014-08-01

108

Dissociation of heart rate variability and heart rate recovery in well-trained athletes.  

PubMed

The purpose of this investigation was to examine the relationships between aerobic fitness, volume of physical activity (PA), heart rate variability (HRV), and heart rate recovery (HRR) in a group of well-trained endurance athletes. Nineteen endurance athletes participated in this study and had aerobic capacities that placed them above the 99th percentile based on normative values (VO(2max): 67.1 ± 2 ml kg(-1) min(-1)). HRV was obtained via an EKG collected during supine rest and reported as high-frequency (HF), low-frequency (LF), and total power (TP). Natural log (ln) transformation was applied when variables violated assumptions of normality. HRR recovery was reported as the reduction in heart rate from peak exercise to the heart rate 1 min after cessation of exercise and PA was estimated from a questionnaire. HRR was significantly correlated with PA and VO(2max) (r = 0.67, P = 0.003 and 0.51, P = 0.039, respectively), but not with any index of HRV. Age was significantly correlated with lnHF (r = -0.49, P = 0.033), lnLF/lnHF (r = 0.48, P = 0.037), and normalized units (NU) of LF (r = 0.47, P = 0.042) and HF (r = -0.47, P = 0.042). Stepwise regression revealed that the strongest predictor of HRR was PA (R (2) = 0.45) and that VO(2max) did not add significant predictive value to the model. The relationship between HRV and age is evident in well-trained endurance athletes, whereas the relationship between HRV and PA/aerobic fitness is not. The maintained relationship between HRR and PA/aerobic fitness suggests that HRR may be a better marker of fitness-related differences in autonomic control in this population. PMID:22124525

Lee, C Matthew; Mendoza, Albert

2012-07-01

109

Population growth rates: issues and an application.  

PubMed Central

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

Godfray, H Charles J; Rees, Mark

2002-01-01

110

Estimating hydraulic properties of volcanic aquifers using constant-rate and variable-rate aquifer tests  

USGS Publications Warehouse

In recent years the ground-water demand of the population of the island of Maui, Hawaii, has significantly increased. To ensure prudent management of the ground-water resources, an improved understanding of ground-water flow systems is needed. At present, large-scale estimations of aquifer properties are lacking for Maui. Seven analytical methods using constant-rate and variable-rate withdrawals for single wells provide an estimate of hydraulic conductivity and transmissivity for 103 wells in central Maui. Methods based on constant-rate tests, although not widely used on Maui, offer reasonable estimates. Step-drawdown tests, which are more abundantly used than other tests, provide similar estimates as constant-rate tests. A numerical model validates the suitability of analytical solutions for step-drawdown tests and additionally provides an estimate of storage parameters. The results show that hydraulic conductivity is log-normally distributed and that for dike-free volcanic rocks it ranges over several orders of magnitude from 1 to 2,500 m/d. The arithmetic mean, geometric mean, and median values of hydraulic conductivity are respectively 520, 280, and 370 m/d for basalt and 80, 50, and 30 m/d for sediment. A geostatistical approach using ordinary kriging yields a prediction of hydraulic conductivity on a larger scale. Overall, the results are in agreement with values published for other Hawaiian islands. ?? 2007 American Water Resources Association.

Rotzoll, K.; El-Kadi, A. I.; Gingerich, S.B.

2007-01-01

111

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

PubMed Central

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

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

2013-01-01

112

Fetal autonomic brain age scores, segmented heart rate variability analysis, and traditional short term variability.  

PubMed

Disturbances of fetal autonomic brain development can be evaluated from fetal heart rate patterns (HRP) reflecting the activity of the autonomic nervous system. Although HRP analysis from cardiotocographic (CTG) recordings is established for fetal surveillance, temporal resolution is low. Fetal magnetocardiography (MCG), however, provides stable continuous recordings at a higher temporal resolution combined with a more precise heart rate variability (HRV) analysis. A direct comparison of CTG and MCG based HRV analysis is pending. The aims of the present study are: (i) to compare the fetal maturation age predicting value of the MCG based fetal Autonomic Brain Age Score (fABAS) approach with that of CTG based Dawes-Redman methodology; and (ii) to elaborate fABAS methodology by segmentation according to fetal behavioral states and HRP. We investigated MCG recordings from 418 normal fetuses, aged between 21 and 40 weeks of gestation. In linear regression models we obtained an age predicting value of CTG compatible short term variability (STV) of R (2) = 0.200 (coefficient of determination) in contrast to MCG/fABAS related multivariate models with R (2) = 0.648 in 30 min recordings, R (2) = 0.610 in active sleep segments of 10 min, and R (2) = 0.626 in quiet sleep segments of 10 min. Additionally segmented analysis under particular exclusion of accelerations (AC) and decelerations (DC) in quiet sleep resulted in a novel multivariate model with R (2) = 0.706. According to our results, fMCG based fABAS may provide a promising tool for the estimation of fetal autonomic brain age. Beside other traditional and novel HRV indices as possible indicators of developmental disturbances, the establishment of a fABAS score normogram may represent a specific reference. The present results are intended to contribute to further exploration and validation using independent data sets and multicenter research structures. PMID:25505399

Hoyer, Dirk; Kowalski, Eva-Maria; Schmidt, Alexander; Tetschke, Florian; Nowack, Samuel; Rudolph, Anja; Wallwitz, Ulrike; Kynass, Isabelle; Bode, Franziska; Tegtmeyer, Janine; Kumm, Kathrin; Moraru, Liviu; Götz, Theresa; Haueisen, Jens; Witte, Otto W; Schleußner, Ekkehard; Schneider, Uwe

2014-01-01

113

Development and preliminary evaluation of an Android based heart rate variability biofeedback system.  

PubMed

The reduced Heart Rate Variability (HRV) is believed to be associated with several diseases such as congestive heart failure, diabetes and chronic kidney diseases (CKD). In these cases, HRV biofeedback may be a potential intervention method to increase HRV which in turn is beneficial to these patients. In this work, a real-time Android biofeedback application based on a Bluetooth enabled ECG and thoracic electrical bioimpedance (respiration) measurement device has been developed. The system performance and usability have been evaluated in a brief study with eight healthy volunteers. The result demonstrates real-time performance of system and positive effects of biofeedback training session by increased HRV and reduced heart rate. Further development of the application and training protocol is ongoing to investigate duration of training session to find an optimum length and interval of biofeedback sessions to use in potential interventions. PMID:25570716

Abtahi, F; Berndtsson, A; Abtahi, S; Seoane, F; Lindecrantz, K

2014-08-01

114

Estimating mental fatigue based on electroencephalogram and heart rate variability  

NASA Astrophysics Data System (ADS)

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

Zhang, Chong; Yu, Xiaolin

2010-01-01

115

Hierarchical Structure of Heart Rate Variability in Humans  

NASA Astrophysics Data System (ADS)

We show a hierarchical structure (HS) of the She-Leveque form in the beat-to-beat RR intervals of heart rate variability (HRV) in humans. This structure, first found as an empirical law in turbulent fluid flows, implies further details in the HRV multifractal scaling. We tested HS using daytime RRi data from healthy subjects and heart diseased patients with congestive heart failure and found a universal law C(b) where b characterizes the multifractality of HRV and C is related to a co-dimension parameter of the most violent events in the fluctuation. The potential of diagnosis is discussed based on the characteristics of this finding. To model the HRV phenomenology, we propose a local-feedback-global-cascade (LFGC) model based on the She-Waymire (SW) cascade solution to the HS in fluid turbulence. This model extends from the previous work in that it integrates additive law multiplicatively into the cascade structure. It is an attempt to relate to the cardiovascular physiology which consists of numerous feedback controls that function primarily on the principle of additive law. In particular, the model is based on the same philosophy as the SW cascade that its multifractal dynamics consists of a singular and a modulating component. In the LFGC model, we introduce local feedback to model the dynamics of the modulating effect. The novelty of our model is to incorporate the cascade structure in the scheduling for the feedback control. This model also represents an alternative solution to the HS. We will present the simulation results by the LFGC model and discuss its implication in physiology terms.

Gao, X. Z.; Ching, E. S. C.; Lin, D. C.

2004-03-01

116

Heart Rate Variability and Exercise in Aging Women  

PubMed Central

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

Blair, Steven N.; Church, Timothy S.

2012-01-01

117

Wave reflections, arterial stiffness, heart rate variability and orthostatic hypotension.  

PubMed

Increased arterial stiffness and wave reflections are independently associated with orthostatic hypotension (OH). This study investigated whether heart rate variability (HRV) is also involved in the modulation of orthostatic blood pressure (BP) change. A total of 429 subjects (65.1±16.4 years, 77.4% men) were enrolled in this study. OH was defined as a ?20?mm?Hg decrease in brachial systolic blood pressure (SBP) or a ?10?mm?Hg diastolic blood pressure (DBP) decrease upon standing. Measurements of carotid-femoral pulse wave velocity (cf-PWV) and the amplitude of the reflected pressure wave from a decomposed carotid pressure wave (Pb) were obtained by carotid tonometry in the supine position. The power spectrum from a 5-min recording of an electrocardiogram at rest was analyzed to provide components in the high frequency (HF) and low frequency (LF) ranges. Subjects with OH (n=59, 13.8%) had significantly higher cf-PWV and Pb and significantly lower LogHF and LogLF than those without OH (n=370). The cf-PWV, Pb, LogHF and LogLF were significantly associated with postural SBP and DBP changes. Furthermore, cf-PWV but not Pb was significantly associated with LogHF and LogLF. Multivariate analysis showed that Pb (odds ratio (OR) per 1 s.d. 1.65, 95% confidence interval (CI) 1.282-2.137; P=0.003) and LogHF (OR 0.628, 95% CI 0.459-0.860, P=0.004), but not cf-PWV (OR 1.279, 95% CI 0.932-1.755, P=0.128), were significant independent determinants of OH. Increased wave reflections may predispose OH independently of arterial stiffness and HRV. In contrast, increased arterial stiffness may cause OH through the modulation of HRV. PMID:25142223

Lu, Dai-Yin; Sung, Shih-Hsien; Yu, Wen-Chung; Cheng, Hao-Min; Chuang, Shao-Yuan; Chen, Chen-Huan

2014-12-01

118

VARIABLE BIT RATE ENCODING USING JPEG2000 M. W. Marcellin and A. Bilgin  

E-print Network

VARIABLE BIT RATE ENCODING USING JPEG2000 M. W. Marcellin and A. Bilgin DTS, USA ABSTRACT A variable bit rate encoding method for JPEG2000 is presented. The method is suitable for encoding digital are subsequently analyzed and parsed to create final JPEG2000 codestreams at any desired average bit rate

Bilgin, Ali

119

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

E-print Network

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

120

Application of high-rate cutting tools  

NASA Astrophysics Data System (ADS)

Widespread application of the newest high-rate cutting tools to the most appropriate jobs is slowed by the sheer magnitude of developments in tool types, materials, workpiece applications, and by the rapid pace of change. Therefore, a study of finishing and roughing sizes of coated carbide inserts having a variety of geometries for single point turning was completed. The cutting tools were tested for tool life, chip quality, and workpiece surface finish at various cutting conditions with medium alloy steel. An empirical wear-life data base was established, and a computer program was developed to facilitate technology transfer, assist selection of carbide insert grades, and provide machine operating parameters. A follow-on test program was implemented suitable for next generation coated carbides, rotary cutting tools, cutting fluids, and ceramic tool materials.

Moriarty, John L., Jr.

1989-03-01

121

Adaptive Observer Design under Low Data Rate Transmission with Applications to Oil Well Drill-string  

E-print Network

-on-the-bit force as a control variable to extinguish limit cycles. It uses the value of the bit angular velocity, to estimate the friction coefficient. In this case, the measured variable is the rotary angular speed. SinceAdaptive Observer Design under Low Data Rate Transmission with Applications to Oil Well Drill

Paris-Sud XI, Université de

122

The application of variable frequency drives to mine fans  

SciTech Connect

During the past several years variable speed drives have become much less expensive for higher horsepower applications. This has created an opportunity to utilize this type of system in variable load mine ventilation applications where the traditional solutions were to use in-flight controllable pitch fans, variable inlet waves or constant load systems and ignore the opportunity for power savings. This paper explores the basic characteristics of each type system and some of the advantages that each system offers for specific mine ventilation applications. The relative capital cost and operating cost of each type systems are also presented.

Smith, R.Z.

1999-07-01

123

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

PubMed

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

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

2014-12-01

124

A variable-data-rate, multimode quadriphase modem.  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

125

Dimensional analysis of heart rate variability in heart transplant recipients  

SciTech Connect

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

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

1987-01-01

126

Temporal relationship between dynamic heart rate variability and electroencephalographic activity during sleep in man  

Microsoft Academic Search

In previous sleep studies, it has been demonstrated that Poincaré plots of RR intervals, which provide a beat to beat dynamic measure of heart rate variability, have distinctive and characteristic patterns according to sleep stages. This study was designed to evaluate the temporal relationship between heart rate variability and sleep electroencephalographic activity (EEG) by using the Pearson's interbeat autocorrelation coefficients

H. Otzenberger; C. Simon; C. Gronfier; G. Brandenberger

1997-01-01

127

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

Microsoft Academic Search

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

M. H. Bonnet; D. L. Arand

1997-01-01

128

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

E-print Network

Analysis of Heart Rate Variability Using Time-Varying Filtering of Heart Transplanted Patients the heart rate variability (HRV), obtained by using the time-varying integral pulse frequency modulation (TVIPFM) which is well adapted to the exercise stress testing. We consider that the mean heart period

Paris-Sud XI, Université de

129

Supporting stored video: reducing rate variability and end-to-end resource requirements through optimal smoothing  

Microsoft Academic Search

VBR compressed video is known to exhibit significant, multiple- time-scale bit rate variability. In this paper, we consider the trans- mission of stored video from a server to a client across a high speed network, and explore how the client buffer space can be used most effectively toward reducing the variability of the transmi tted bit rate. We present two

James D. Salehi; Shi-Li Zhang; James F. Kurose; Donald F. Towsley

1998-01-01

130

ORTHOSTATIC HYPOTENSION AND HEART RATE VARIABILITY AS INDICATORS OF CARDIAC AUTONOMIC NEUROPATHY IN DIABETES MELLITUS  

Microsoft Academic Search

Aim: The aim of this study was to emphasize two different points in our work: 1) The well known importance of (subclinical) postural hypotension and reduced heart rate variability as (early) markers of autonomic neuropathy; 2) and the more controversial influence of diabetic control in their worsening. Methods: Two standard cardiovascular response tests (heart rate variability by respiration and orthostatic

Abdülkadir Koçer; Zekeriya Aktürk; Emin Maden

131

Understanding garnet variability: Application of geometallurgy to diamonds and exploration  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

132

26 CFR 1.1275-5 - Variable rate debt instruments.  

...payments and the number of complete years to maturity from the issue date...rate for an initial period of 1 year or less followed by a...on intervals that are equal in length. For example, if a 4-year debt instrument provides...

2014-04-01

133

Heart rate variability in left ventricular dysfunction and heart failure: effects and implications of drug treatment.  

PubMed Central

OBJECTIVE--To review the importance of heart rate variability analysis in left ventricular dysfunction and heart failure and to assess the effects of drug treatment. In patients with left ventricular dysfunction or heart failure, a low heart rate variability is a strong predictor of a low probability of survival. Because drug treatment in these patients has rapidly changed over the past two decades, the effect of these drugs on heart rate variability needs special attention. DESIGN--A study of published reports to give an overview of heart rate variability in patients with left ventricular dysfunction or heart failure and how it is affected by drug treatment. RESULTS--Analysis of heart rate variability provides an easily obtained early marker for progression of disease. It seems to be more closely related to the degree of neurohumoral activation than to haemodynamic variables. Cardiovascular drugs may either stimulate or inhibit the degree of neurohumoral activation, and the effects of pharmacological intervention can be closely monitored with this method. CONCLUSIONS--The analysis of heart rate variability, including spectral analysis, is a novel non-invasive way to obtain potentially useful clinical information in patients with reduced left ventricular function. The effects of drug treatment on heart rate variability are in general consistent with their long-term effects in left ventricular dysfunction and heart failure. PMID:7857731

Tuininga, Y S; van Veldhuisen, D J; Brouwer, J; Haaksma, J; Crijns, H J; Man in't Veld, A J; Lie, K I

1994-01-01

134

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

PubMed Central

OBJECTIVE—To examine the correlation between heart rate variability and left ventricular mass in cyclists with an athlete's heart.?METHODS—Left 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 time and frequency domain heart rate variability indices were computed.?RESULTS—In the cyclists, the mean of all RR intervals between normal beats (meanNN), the SD of the RR intervals, and their coefficient of variation were significantly greater than in control subjects (p < 0.01, p < 0.01, and p < 0.05, respectively). For cyclists and control subjects, only meanNN correlated with left ventricular mass (r = 0.48, p = 0.038). The heart rate variability indices that correlated with functional or metabolic variables were: meanNN v E/A peak (the ratio of peak early and peak atrial filling rate) (r = 0.48, p = 0.039); the root mean square of successive differences in RR intervals among successive normal beats v E/A area (ratio of peak early and peak atrial filling volume) (r = 0.48, p = 0.040); percentage of successive RR intervals differing by more than 50 ms v the phosphocreatine to ATP ratio at rest (r = 0.54, p = 0.017); and the SD of the average RR intervals during all five minute periods v the phosphocreatine to ATP ratio during stress (r = 0.60, p = 0.007).?CONCLUSIONS—Highly trained cyclists have increased heart rate variability indices, reflecting increased cardiac vagal control compared with control subjects. Left ventricular mass has no major influence on heart rate variability, but heart rate variability is significantly correlated with high energy phosphate metabolism and diastolic function.???Keywords: heart rate variability; left ventricular mass; hypertrophy; athlete's heart PMID:10336920

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

1999-01-01

135

Variable temperature effects on release rates of readily soluble nuclides  

SciTech Connect

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.

Kim, C.-L.; Light, W.B.; Lee, W.W.-L.; Chambre, P.L.; Pigford, T.H. (Korea Advanced Energy Research Inst., Daeduk (Republic of Korea); Lawrence Berkeley Lab., CA (USA))

1988-09-01

136

Variability in Nest Survival Rates and Implications to Nesting Studies  

NSDL National Science Digital Library

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

Johnson, Douglas H.

137

Multiport solid-state imager characterization at variable pixel rates  

SciTech Connect

The imaging performance of an 8-port Full Frame Transfer Charge Coupled Device (FFT CCD) as a function of several parameters including pixel clock rate is presented. The device, model CCD- 13, manufactured by English Electric Valve (EEV) is a 512 {times} 512 pixel array designed with four individual programmable bidirectional serial registers and eight output amplifiers permitting simultaneous readout of eight segments (128 horizontal {times} 256 vertical pixels) of the array. The imager was evaluated in Los Alamos National Laboratory`s High-Speed Solid-State Imager Test Station at true pixel rates as high as 50 MHz for effective imager pixel rates approaching 400 MHz from multiporting. Key response characteristics measured include absolute responsivity, Charge-Transfer-Efficiency (CTE), dynamic range, resolution, signal-to-noise ratio, and electronic and optical crosstalk among the eight video channels. Preliminary test results and data obtained from the CCD-13 will be presented and the versatility/capabilities of the test station will be reviewed.

Yates, G.J.; Albright, K.A. [Los Alamos National Lab., NM (United States); Turko, B.T. [Lawrence Berkeley Lab., CA (United States)

1993-08-01

138

VARIABLE FIRING RATE OIL BURNER USING PULSE FUEL FLOW CONTROL.  

SciTech Connect

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

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

2004-10-01

139

The contribution of coping-related variables and heart rate variability to visual search performance under pressure.  

PubMed

Visual search performance under pressure is explored within the predictions of the neurovisceral integration model. The experimental aims of this study were: 1) to investigate the contribution of coping-related variables to baseline, task, and reactivity (task-baseline) high-frequency heart rate variability (HF-HRV), and 2) to investigate the contribution of coping-related variables and HF-HRV to visual search performance under pressure. Participants (n=96) completed self-report measures of coping-related variables (emotional intelligence, coping style, perceived stress intensity, perceived control of stress, coping effectiveness, challenge and threat, and attention strategy) and HF-HRV was measured during a visual search task under pressure. The data show that baseline HF-HRV was predicted by a trait coping-related variable, task HF-HRV was predicted by a combination of trait and state coping-related variables, and reactivity HF-HRV was predicted by a state coping-related variable. Visual search performance was predicted by coping-related variables but not by HF-HRV. PMID:25481358

Laborde, Sylvain; Lautenbach, Franziska; Allen, Mark S

2015-02-01

140

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

141

Emergence of dynamical complexity related to human heart rate variability  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

142

Identifying Effective Counselors Through Client-Supervisor Ratings and Personality-Environmental Variables.  

ERIC Educational Resources Information Center

Compared client ratings of counselor effectiveness with tested personality characteristics, personal-professional demographic variables, and supervisor ratings. Findings included a high correlation between supervisor and client ratings of counselor effectiveness and a significant difference between high- and low-effective counselors for job…

Wiggins, James D.; Moody, Anne

1983-01-01

143

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,...

144

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

E-print Network

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

Brown, Emery N.

145

12 CFR 226.19 - Certain mortgage and variable-rate transactions.  

Code of Federal Regulations, 2012 CFR

...Section 226.19 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Closed-End Credit § 226.19 Certain mortgage and variable-rate transactions....

2012-01-01

146

12 CFR 226.19 - Certain mortgage and variable-rate transactions.  

Code of Federal Regulations, 2010 CFR

...Section 226.19 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Closed-End Credit § 226.19 Certain mortgage and variable-rate transactions....

2010-01-01

147

12 CFR 226.19 - Certain mortgage and variable-rate transactions.  

Code of Federal Regulations, 2013 CFR

... Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM (CONTINUED) TRUTH IN LENDING (REGULATION Z) Closed-End Credit § 226.19 Certain mortgage and variable-rate transactions....

2013-01-01

148

12 CFR 226.19 - Certain mortgage and variable-rate transactions.  

Code of Federal Regulations, 2011 CFR

...Section 226.19 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Closed-End Credit § 226.19 Certain mortgage and variable-rate transactions....

2011-01-01

149

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

150

Heart Rate Variability during Exercise Performed below and above Ventilatory Threshold  

Microsoft Academic Search

COTTIN, F., C. MEDIGUE, P.-M. LEPRETRE, Y. PAPELIER, J.-P. KORALSZTEIN, and V. BILLAT. Heart Rate Variability during Exercise Performed below and above Ventilatory Threshold. Med. Sci. Sports Exerc., Vol. 36, No. 4, pp. 594 - 600, 2004. Purpose: To examine whether differences in heart rate variability (HRV) can distinguish sub- from supra-ventilatory-threshold exercise and whether the exercise duration at supra-threshold

FRANCOIS COTTIN; CLAIRE MEDIGUE; PIERRE-MARIE LEPRETRE; YVES PAPELIER; JEAN-PIERRE KORALSZTEIN; VERONIQUE BILLAT

2004-01-01

151

Inverse coupling between ultradian oscillations in delta wave activity and heart rate variability during sleep  

Microsoft Academic Search

Objective: We investigate the relationship between changes in heart rate variability and electroencephalographic (EEG) activity during sleep.Method: Nine male subjects with regular non-rapid-eye movement-rapid-eye movement (NREM-REM) sleep cycles were included in the study. They underwent EEG and cardiac recordings during one experimental night. Heart rate variability was determined over 5-min periods by the ratio of low frequency to low frequency

Gabrielle Brandenberger; Jean Ehrhart; François Piquard; Chantal Simon

2001-01-01

152

Heart Rate Variability Predicts Cognitive Reactivity to a Sad Mood Provocation  

Microsoft Academic Search

Cognitive reactivity—the tendency to think negatively in response to a sad mood—is an important predictor of depression vulnerability.\\u000a The current study examined whether heart rate variability, a physiological index of emotion regulation capacity, predicts\\u000a individual differences in cognitive reactivity. Heart rate variability in the high frequency spectrum was assessed during\\u000a a 5-min rest period among a sample of healthy, female

Christopher G. BeeversAlissa; Alissa J. Ellis; Ryan M. Reid

153

On the management of variable bit-rate traffic streams in packet-switched networks  

E-print Network

ON THE MANAGEMENT OF VARIABLE BIT-RATE TRAFFIC STREAMS IN PACKET-SWITCHED NETWORKS A Thesis by BYEONGKI YOO Submitted to the Office of Graduate Studies of Texas ASM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1998 Major Subject: Computer Science ON THE MANAGEMENT OF VARIABLE BIT-RATE TRAFFIC STREAMS IN PACKET-SWITCHED NETWORKS A Thesis by BYEONGKI YOO Submitted to Texas A&M University in partial fulfillment...

Yoo, Byeongki

2012-06-07

154

February 2005 Determining Optimum Nitrogen Application Rates for Corn  

E-print Network

1 February 2005 Determining Optimum Nitrogen Application Rates for Corn Larry Bundy, Todd Andraski factor affecting the efficiency of N use by corn. It is impera- tive that N application rate recommendations accu- rately predict the amount of N needed to obtain profitable corn yields and minimize N losses

Balser, Teri C.

155

Avalanche Photo-Detection for High Data Rate Applications  

E-print Network

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.

H. B. Coldenstrodt-Ronge; C. Silberhorn

2007-09-19

156

Holocene activity of an alpine debris-flow catchment: does climate control erosion rate variability?  

NASA Astrophysics Data System (ADS)

The Zielbach catchment is located in the central-eastern Italian Alps. It covers an area of ca. 40 km2 and is characterized by fluvial sediment transport along the main drainage basin, and by the supply of sediment through debris flows, derived from a ca. 10 km2 tributary catchment. A debris-flow database demonstrates that nowadays this latter tributary dominates the sediment budget of the entire Zielbach. In this study, we analyze modern and paleo-erosion rates of the catchment through the application of the cosmogenic nuclides technique. For modern erosion rate, samples of river-born sand were taken from the main river and tributaries along the entire drainage system, while paleo-erosion rates are calculated thanks to cores' samples, which were collected on the alluvial fan and which were likewise dated based on 14C measurements of organic matter. Results obtained from the modern drainage system reveal the spatial erosion rate variability that characterizes the catchment nowadays (values ranging from 2.6 to 0.15 mm/yr). This spatial pattern is characterized by a generally increasing trend of 10Be values where hillslope contributions predominate and by a decreasing concentration trend where sediment has been supplied by debris flows. Results obtained from the cores allow the reconstruction of the Zielbach Holocene evolution and the assignment of the climate role on the temporal erosion rate variability (values ranging between 21 and 0.43 mm/yr). 14C concentrations of organic material collected from the core material indicate a lowermost age of 10'000 yr at ca. 35 m depth. The sedimentary fabric of the deposits indicates that the fan is built up by alternation of alluvial and debris-flow deposits, where the latter ones dominate in volumes. The stratigraphic architecture also infers that alluvial deposits correspond to periods of low activity of the debris-flow catchment. Most important, however, paleo-erosion rates indicate a decreasing trend for the debris-flow activity from ca. 10'000 yr to the present, with values decreasing from ca. 21 to 0.8 mm/yr. During the same time span, the alluvial sediment supplied by the main catchment appears to have been steady, as indicated by a constant basin-averaged denudation rate of 0.45 mm/yr. The comparison of these results with the climatic history of the valley reveals that periods of high activity of the debris flow catchment (associated with higher 10Be-based erosion rates) correspond to periods of a wetter and cooler climate. In particular, the highest value (21 mm/yr) seems to be related to the late glacial phase, which presumably started after the LGM and terminated around 10'000 yr, while a reactivation of the debris-flow activity, with erosion rates around 1.0 mm/yr, corresponds to the Holocene climatic deterioration at ca. 3'500 yr B.P. The alluvial phase of the Zielbach catchment (erosion rate of ca. 0.43 mm/yr), marked by absent or lower debris-flow activity, seems to be related to the Holocene climatic optimum between 8'000 and 4'000 years ago.

Savi, S.; Norton, K. P.; Brardinoni, F.; Akçar, N.; Kubik, P.; Picotti, V.; Schlunegger, F.

2012-12-01

157

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

PubMed Central

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

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

2012-01-01

158

Cooled variable nozzle radial turbine for rotor craft applications  

NASA Technical Reports Server (NTRS)

An advanced, small 2.27 kb/sec (5 lbs/sec), high temperature, variable area radial turbine was studied for a rotor craft application. Variable capacity cycles including single-shaft and free-turbine engine configurations were analyzed to define an optimum engine design configuration. Parametric optimizations were made on cooled and uncooled rotor configurations. A detailed structural and heat transfer analysis was conducted to provide a 4000-hour life HP turbine with material properties of the 1988 time frame. A pivoted vane and a moveable sidewall geometry were analyzed. Cooling and variable geometry penalties were included in the cycle analysis. A variable geometry free-turbine engine configuration with a design 1477K (2200 F) inlet temperature and a compressor pressure ratio of 16:1 was selected. An uncooled HP radial turbine rotor with a moveable sidewall nozzle showed the highest performance potential for a time weighted duty cycle.

Rogo, C.

1981-01-01

159

Heart rate variability to assess ventilatory threshold in ski-mountaineering.  

PubMed

Abstract The capacity to predict the heart rate (HR) and speed at the first (VT1) and second (VT2) ventilatory thresholds was evaluated during an incremental ski-mountaineering test using heart rate variability (HRV). Nine skiers performed a field test to exhaustion on an alpine skiing track. VT1 and VT2 were individually determined by visual analysis from gas exchanges (VT1V and VT2V) and time-varying spectral HRV analysis (VT1fH, VT2fH and VT2H). VT1 could not be determined with the HRV methods used. On the contrary, the VT2 was determined in all skiers. No significant difference between HR and speed at VT2H and VT2V was observed (174.3 ± 5.6 vs. 174.3 ± 5.3 bpm, and 6.3 ± 0.9 and 6.3 ± 0.9 km h(-1), respectively). Strong correlations were obtained for HR (r = 0.91) and speed (r = 0.92) at VT2H and VT2V with small limits of agreement (±3.6 bpm for HR). Our results indicated that HRV enables determination of HR and speed at VT2 during a specific ski-mountaineering incremental test. These findings provide practical applications for skiers in order to evaluate and control specific training loads, at least when referring to VT2. PMID:25228474

Cassirame, Johan; Tordi, Nicolas; Fabre, Nicolas; Duc, Sébastien; Durand, Fabienne; Mourot, Laurent

2014-09-17

160

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

PubMed

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

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

2008-01-01

161

Final Study for Bonneville Power Administration's 1986 Variable Industrial Power Rate Proposal.  

SciTech Connect

In this study, BPA is proposing a Variable Industrial Power (VI-86) rate option for its aluminum smelter loads. This rate would provide a predetermined contractual tie between the price of BPA's power and the US market price of aluminum. Establishing such a tie between input price (electricity) and output price (aluminum) will enhance the ability of aluminum producers to operate over the entire business cycle. This should reduce the cyclicality of smelter operations. Increasing the price of power when aluminum prices are high is intended to compensate BPA for any decrease in BPA's revenues when the lower rates occur. Various proposals for and discussions of a variable rate for BPA's direct service industrial (DSI) customers have occurred throughout the region over the past year. This study is the result of analyses conducted and evidence received from the rate hearings conducted on the Variable Rate (VI-86). This study describes the Variable rate proposed by BPA and the analyses conducted in support of the rate.

United States. Bonneville Power Administration.

1986-06-01

162

Spatial variability of erosion rates inferred from the frequency distribution of cosmogenic 3  

E-print Network

Spatial variability of erosion rates inferred from the frequency distribution of cosmogenic 3 He.W. Carlson Available online 22 November 2007 Abstract To constrain the spatial distribution of erosion rates grains each. The average [3 He]c from the 26 aliquots was used to estimate a basin-wide average erosion

Mukhopadhyay, Sujoy

163

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

E-print Network

Wrapper subset evaluation facilitates the automated detection of diabetes from heart rate, and is associated with many other conditions such as vision loss, heart failure and stroke. Any improvement in early that the detection of diabetes is feasible from heart rate variability measures. D. J. Cornforth, H. F. Jelinek, M. C

Teich, Malvin C.

164

[Changes in heart rate variability after myocardial infarction. Value of Poincareé's diagram].  

PubMed

The variability of the heart rate is reduced after myocardial infarction. It then progressively increases, to return to near normal values after several months. However, these changes in heart rate variability occur at the same time as slowing of the heart rate which makes interpretation difficult. Poincaré's diagram is constructed from a Holter recording plotting each RR interval against the preceding RR interval. The authors have developed a geometric approach to this diagram to evaluate parasympathetic tone for a given heart rate. By measuring the dispersion in height of the Poincaré's diagram, the authors evaluate the shor-term variability for a given RR interval. Two 24 hr Holter recordings were performed in 52 patients at one and two weeks after a myocardial infarction. The dispersion in the height of the Poincaré's diagrams was measured at the 10th, 25th, 50th, 75th and 90th percentiles of the total dispersion. The authors have shown an increase in the short-term variability of the shortest RR intervals (1th, 25th and 50th percentiles) which is not observed in the longer RR intervals (75th and 90th percentiles). In conclusion, theres is an increase in the heart rate variability at the shortest RR intervals. This suggests that the recovery of parasympathic tone after myocardial infarction occurs mainly at the fastest heart rates. PMID:8745997

Copie, X; Le Heuzey, J Y; Iliou, M C; Pousset, F; Lavergne, T; Guize, L

1995-11-01

165

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

PubMed

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

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

2011-06-20

166

Probabilistic pipe fracture evaluations for leak-rate-detection applications  

SciTech Connect

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

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

1995-04-01

167

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

PubMed Central

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

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

1994-01-01

168

Effect of flow rate on environmental variables and phytoplankton dynamics: results from field enclosures  

NASA Astrophysics Data System (ADS)

To investigate the effects of flow rate on phytoplankton dynamics and related environment variables, a set of enclosure experiments with different flow rates were conducted in an artificial lake. We monitored nutrients, temperature, dissolved oxygen, pH, conductivity, turbidity, chlorophyll-a and phytoplankton levels. The lower biomass in all flowing enclosures showed that flow rate significantly inhibited the growth of phytoplankton. A critical flow rate occurred near 0.06 m/s, which was the lowest relative inhibitory rate. Changes in flow conditions affected algal competition for light, resulting in a dramatic shift in phytoplankton composition, from blue-green algae in still waters to green algae in flowing conditions. These findings indicate that critical flow rate can be useful in developing methods to reduce algal bloom occurrence. However, flow rate significantly enhanced the inter-relationships among environmental variables, in particular by inducing higher water turbidity and vegetative reproduction of periphyton (Spirogyra). These changes were accompanied by a decrease in underwater light intensity, which consequently inhibited the photosynthetic intensity of phytoplankton. These results warn that a universal critical flow rate might not exist, because the effect of flow rate on phytoplankton is interlinked with many other environmental variables.

Zhang, Haiping; Chen, Ruihong; Li, Feipeng; Chen, Ling

2014-12-01

169

Diurnal variation in heart rate variability before and after maximal exercise testing.  

PubMed

As heart-rate variability (HRV) is under evaluation in clinical applications, the authors sought to better define the interdependent impact of age, maximal exercise, and diurnal variation under physiologic conditions. The authors evaluated the diurnal changes in HRV 24-h pre- and post-maximal aerobic exercise testing to exhaustion in young (19-25 yrs, n?=?12) and middle-aged (40-55 yrs, n?=?12) adults. Subjects wore a portable 5-lead electrocardiogram holter for 48?h (24?h prior to and following a maximal aerobic capacity test). Time-, frequency-, time-frequency-, and scale-invariant-domain measures of HRV were computed from RR-interval data analyzed using a 5-min window size and a 2.5-min step size, resulting in a different set of outputs every 2.5?min. Results were averaged (mean?±?SE) over four prespecified time periods during the morning, afternoon, evening, and night on Day 1 and Day 2. Diurnal changes in HRV in young and middle-aged adults were compared using a two-way, repeated-measures analysis of variance (ANOVA). Young adults demonstrated higher HRV compared to middle-aged adults during periods of wakefulness and sleep prior to maximal exercise stress testing (i.e., high-frequency power during Day 1: young adults: morning 1862?±?496?ms(2), afternoon 1797?±?384?ms(2), evening 1908?±?431?ms(2), and night 3202?±?728?ms(2); middle-aged adults: morning 341?±?53?ms(2), afternoon 405?±?68?ms(2), evening 469?±?80?ms(2), and night 836?±?136?ms(2)) (p < .05). Exercise resulted in reductions in HRV such that multiple measures of HRV were not significantly different between age groups during the afternoon and evening periods. All measures of HRV demonstrated between-group differences overnight on Day 2 (p < .05). Young adults are associated with higher baseline HRV during the daytime. Sleep increases variability equally and proportionally to daytime variability. Given the higher baseline awake HRV and equal rise in HRV during sleep, the change in HRV from sleep to morning with exercise is greater in younger subjects. These physiologic results have clinical significance in understanding the pathophysiology of altered variability in ill patients. PMID:21539426

Armstrong, Rachel G; Kenny, Glen P; Green, Geoffrey; Seely, Andrew J E

2011-05-01

170

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

PubMed Central

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

2014-01-01

171

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...

172

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

Microsoft Academic Search

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.

MARTIN BUCHHEIT; CHANTAL SIMON; ANNE CHARLOUX; GABRIELLE BRANDENBERGER

2005-01-01

173

Variable rate phosphorus fertilization experiment based on on-line visible and near infrared soil sensing  

NASA Astrophysics Data System (ADS)

Soil phosphorus is an important nutrient particularly for root and seed development, and deficiency of soil P could result in poor crop yield. However, over-application of Phosphorous causes waste of fertilizer and contamination to the environment. Variable rate (VR) fertilization may allow for a better phosphorous management in the soil, if within field variability in soil available P (P_av) can be characterized at a desirable fine scale. Visible and near infrared (vis-NIR) spectroscopy has been proven to be fast, cheap and non-destructive tool for the measurement of P_av. On-line vis-NIR sensors enable the collection of high resolution data on P_av with acceptable accuracy. The aim of this paper was to compare the economic and environmental benefits of VR phosphorous fertilization based on on-line vis-NIR soil sensing (OVR) against uniform rate (UR) and traditional precision farming variable rate (TVR). A trial plot experiment consisting of 9 plots was designed and implemented in a field with spring barely in 2013. Triplication plots (24 m width) for each of the three fertilization methods (OVR, UR and TVR) were randomly laid out in the field. Prior to the fertilization experiment, an on-line vis-NIR measurement was carried out to measure within field variation in P_av. Fertilizer input (P2O5 in kg ha-1) and yield output of each plot was measured to run a basic cost-benefit analysis. The validation of the on-line measurement with an independent validation set showed moderate measurement accuracy of P_av (R2= 0.72, RMSEP = 0.55 mg/100g and RPD = 1.99). The lowest amount of P2O5 was recommended and applied in OVR plots, which indicated a reduction of fertilizer use by 40 and 54 kg ha-1, as compared to UR and TPF method, respectively. Small yield difference was observed between the three treatments, although UR plots showed a slightly higher yield (6.990 kg ha-1). However, ANOVA analysis resulted in a smaller F value of 0.22 than F critical (3.22), which allows the conclusion that the differences of yield between the three treatments are insignificant at 5% confidence (p < 0.05) level. The cost-benefit analysis showed the OVR method to provide comparable margin to TVR method, as only extra £2 per ha was calculated with OVR. A much larger margin of about £31 per ha was obtained with the innovative the OVR method, as compared to the TVR. A longer term experiment is still underway in the same to understand and confirm the mechanism and agronomic link if any between fertilizer input and crop growth and yield, as practical experience indicated that more than one cropping season is needed to record actual crop response to phosphorous application. It can be concluded that a clear environmental benefit can be achieved by using the innovative OVR concept. However, a longer term study is needed to prove the economic benefit, as compared particularly to TVR. .

Kuang, Boyan; Mouazen, Abdul

2014-05-01

174

Continuously variable transmission: Assessment of applicability to advance electric vehicles  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

175

Influence of transrectal and transabdominal ultrasound examination on salivary cortisol, heart rate, and heart rate variability in mares.  

PubMed

Pregnancy diagnostics in equine reproduction are routinely performed using transrectal ultrasonography, although it is also possible to visualize the fetus by transabdominal ultrasound examinations from the 90th day of gestation onward. We hypothesized that ultrasound examinations may stress the mare and that the gestational stage status and lactation may influence the mare's stress reaction. To investigate the stress reaction, 25 thoroughbred mares of different age, pregnancy and lactational status underwent a transrectal examination. In pregnant mares, an additional transabdominal examination was performed. Salivary cortisol concentration, mean heart rate, and heart rate variability of mares were assessed to evaluate the reactions of hypothalamic-pituitary-adrenal (HPA) axis and of the autonomic nervous system. Significant differences were observed between lactating and nonlactating mares; with a lower responsiveness to stress in lactating mares. The transrectal ultrasound examination in nonlactating mares induced a significant increase in salivary cortisol (P < 0.05), and in the heart rate variability parameter, ratio of low to high frequencies (P < 0.05). This reflects an activation of the HPA axis and a shift to more sympathetic dominance. In contrast, a transabdominally performed pregnancy check did not induce an activation of the HPA axis over basal level but increased the mean heart rate and low to high frequency ratio. The results of this study indicate that checks of advanced pregnancies can be easily performed by transabdominal ultrasonography. With regard to animal welfare, this technique should be preferred during midgestation in nonlactating mares. PMID:25529317

Schönbom, Hanno; Kassens, Ana; Hopster-Iversen, Charlotte; Klewitz, Jutta; Piechotta, Marion; Martinsson, Gunilla; Kißler, Andreas; Burger, Dominik; Sieme, Harald

2015-03-01

176

Quantifying variable erosion rates to understand the coupling of surface processes in the Teton Range, Wyoming  

NASA Astrophysics Data System (ADS)

Short-term geomorphic processes (fluvial, glacial, and hillslope erosion) and long-term exhumation control transient alpine landscapes. Long-term measurements of exhumation are not sufficient to capture the processes driving transient responses associated with short-term climatic oscillations, because of high variability of individual processes across space and time. This study compares the efficacy of different erosional agents to assess the importance of variability in tectonically active landscapes responding to fluctuations in Quaternary climate. We focus on the Teton Range, where erosional mechanisms include hillslope, glacial, and fluvial processes. Erosion rates were quantified using sediment accumulation and cosmogenic dating (bedrock and stream sediments). Results show that rates of erosion are highly variable, with average short-term rockfall rates (0.8 mm/y) occurring faster than either apparent basin-averaged (0.2 mm/y) and long-term ridge erosion rates (0.02 mm/y). Examining erosion rates separately also demonstrates the coupling between glacial, fluvial, and hillslope processes. Apparent basin-averaged erosion rates amalgamate valley wall and ridge erosion with stream and glacial rates. Climate oscillations drive the short-term response of a single erosional process (e.g., rockfalls or other mass wasting) that may enhance or limit the erosional efficiency of other processes (glacial or fluvial). While the Teton landscape may approach long-term equilibrium, stochastic processes and rapid response to short-term climate change actively perpetuate the transient ruggedness of the topography.

Tranel, Lisa M.; Spotila, James A.; Binnie, Steven A.; Freeman, Stewart P. H. T.

2015-01-01

177

A wavelet-based heart rate variability analysis for the study of nonsustained ventricular tachycardia  

Microsoft Academic Search

It has been reported that the sympathovagal balance (SB) can be quantified by heart rate (HR) via the low-frequency (LF) to high-frequency (HF) spectral power ratio LF\\/HF. In this paper, an investigation of the relationship between the autonomic nervous system (ANS) and nonsustained ventricular tachycardia (NSVT) is presented. A wavelet transform (WT)-based approach for short-time heart rate variability (HRV) assessments

Szi-Wen Chen

2002-01-01

178

Bit-Rate-Variable DPSK Demodulation Using Silicon Microring Resonators With Electro-Optic Wavelength Tuning  

Microsoft Academic Search

We demonstrate a bit-rate-variable differential phase-shift keying (DPSK) demodulator based on silicon microring resonators (MRRs) with an integrated diode for wavelength tuning. The resonance wavelength of the MRR may be tuned by carrier injection and depletion. Error-free operations (bit error rate ${<}10^{-9}$ ) have been achieved for all tuning wavelengths. In addition, the proposed scheme can demodulate DPSK signals over

Ke Xu; Gordon K. P. Lei; Stanley M. G. Lo; Zhenzhou Cheng; Chester Shu; Hon Ki Tsang

2012-01-01

179

Respiratory influences on non-linear dynamics of heart rate variability in humans  

Microsoft Academic Search

.  ?The goal of our study was to determine whether evidence for chaos in heart rate variability (HRV) can be observed when the\\u000a respiratory input to the autonomic controller of heart rate is forced by the deterministic pattern associated with periodic\\u000a breathing. We simultaneously recorded, in supine healthy volunteers, RR intervals and breathing volumes for 20 to 30?min (1024\\u000a data point

J.-O. Fortrat; Yoshiharu Yamamoto; Richard L. Hughson

1997-01-01

180

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

PubMed

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

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

2014-02-01

181

A Within-Subject Normal-Mixture Model with Mixed-Effects for Analyzing Heart Rate Variability  

PubMed Central

Data on heart rate variability (HRV) have been used extensively to indirectly assess the autonomic control of the heart. The distributions of HRV measures, such as the RR-interval, are not necessarily normally distributed and current methodology does not typically incorporate this characteristic. In this article, a mixed-effects modeling approach under the assumption of a two-component normal-mixture distribution for the within-subject observations has been proposed. Estimation of the parameters of the model was performed through an application of the EM algorithm, which is different from the traditional EM application for the normal-mixture methods. An application of this method was illustrated and the results from a simulation study were discussed. Differences among other methods were also reviewed. PMID:25506510

Ketchum, Jessica M.; Best, Al M.; Ramakrishnan, Viswanathan

2014-01-01

182

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

ERIC Educational Resources Information Center

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

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

2012-01-01

183

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 in corn. The objective of this research was to identify the sources of variability in the observed and estimated economic optimum N rates (EONR) using Crop Circle. Field experiments were c...

184

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...

185

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

ERIC Educational Resources Information Center

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

Srinivasan, Krishnamachari

2007-01-01

186

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

ERIC Educational Resources Information Center

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

Orman, Evelyn K.

2011-01-01

187

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

ERIC Educational Resources Information Center

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

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

2014-01-01

188

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 (...

189

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

E-print Network

Cigarette smoking has been shown to adverse- ly affect heart rate variability (HRV), suggesting dysregula] and introduces a variety of adverse health consequences such as cardiovas- cular diseases (CVD) [2], respiratory diseases [3], and can- cer [4]. Smoking also increases the risk of ischemic heart disease and sudden

Meston, Cindy

190

Polarization-insensitive delay-asymmetric nonlinear loop mirror for variable bit-rate DPSK demodulation  

Microsoft Academic Search

We demonstrate a polarization-insensitive delay-asymmetric nonlinear loop mirror for DPSK demodulation at variable bit-rates. The output power variation has been suppressed to below 0.35 dB for arbitrary input signal polarization states.

Y. H. Dai; Mable P. Fok; Chester Shu

2009-01-01

191

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...

192

The Use of Heart Rate Variability as a Novel Method to Differentiate between Affective 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 ‘unpleasant’ versus ‘pleas...

193

Methodology for multifractal analysis of heart rate variability: From LF\\/HF ratio to wavelet leaders  

Microsoft Academic Search

The present contribution aims at proposing a comprehensive and tutorial introduction to the practical use of wavelet Leader based multifractal analysis to study heart rate variability. First, the theoretical background is recalled. Second, practical issues and pitfalls related to the selection of the scaling range or statistical orders, minimal regularity, parabolic approximation of spectrum and parameter estimation, are discussed. Third,

P. Abry; H. Wendt; S. Jaffard; H. Helgason; P. Goncalve?s; E. Pereira; C. Gharib; P. Gaucherand; M. Doret

2010-01-01

194

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

EPA Science Inventory

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

195

Response-Time Variability Is Related to Parent Ratings of Inattention, Hyperactivity, and Executive Function  

ERIC Educational Resources Information Center

Objective: Individuals with ADHD are often characterized as inconsistent across many contexts. ADHD is also associated with deficits in executive function. We examined the relationships between response time (RT) variability on five brief computer tasks to parents' ratings of ADHD-related features and executive function in a group of children with…

Gomez-Guerrero, Lorena; Martin, Cristina Dominguez; Mairena, Maria Angeles; Di Martino, Adriana; Wang, Jing; Mendelsohn, Alan L.; Dreyer, Benard P.; Isquith, Peter K.; Gioia, Gerard; Petkova, Eva; Castellanos, F. Xavier

2011-01-01

196

Modulated Lattice Vector Quantization: How to Make Quantization Index Modulation an Efficient Variable Rate Source Coder  

Microsoft Academic Search

The design of a variable rate joint watermarking and compression (JWC) scheme is examined in this paper. The proposed approach, called modulated lattice vector quantization (MLVQ), is based on dither modulation quantization index modulation (DM-QIM) which allows for embedding information while maintaining good coding performance. In the first part, we propose a specific indexing method to make MLVQ with a

Ludovic Guillemot; Jean-Marie Moureaux

2010-01-01

197

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

ERIC Educational Resources Information Center

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

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

2007-01-01

198

Prognostic 2.0: software tool for heart rate variability analysis and QT interval dispersion  

Microsoft Academic Search

Cardiovascular diseases, in particular Acute Myocardial Infarction (AMI) are the first cause of death in industrialized countries. Measurements of indicators of the behavior of the autonomic nervous system, such as the Heart Rate Variability (HRV) and the QT Interval Dispersion (QTD) in the acute phase of the AMI (first 48 hours after the event) give a good estimation of the

Alfonso Mendoza; Oscar L. Rueda; Lola X. Bautista; Víctor E. Martinez; Eddie R. Lopez; Mario F. Gomez; Alexander Alvarez

2007-01-01

199

Effects of Two Yoga Based Relaxation Techniques on Heart Rate Variability (HRV)  

Microsoft Academic Search

Heart rate variability (HRV) was studied in cyclic meditation (CM) and supine rest (SR). CM included yoga postures followed by guided relaxation. Forty-two male volunteers were assessed in CM and SR sessions of 35 minutes, where CM or SR practice was preceded and followed by 5 minutes of SR. During the yoga postures of CM and after CM, low frequency

Patil Sarang; Shirley Telles

2006-01-01

200

Detection of Acute Stress by Heart Rate Variability Using a Prototype Mobile ECG Sensor  

Microsoft Academic Search

Mental stress affects our body often detrimentally. Heart rate variability (HRV) analysis is commonly used as a quantitative marker depicting the activit y of autonomic nervous system that may be related to mental stress. HRV features can be extracted by detecting QRS complexes from electrocardiogram (ECG) signals. A miniature ECG device can enable HRV features to be measured anytime and

Lizawati Salahuddin; Desok Kim

2006-01-01

201

Variable Rate Phosphorus Fertilization in Cotton on the Texas High Plains  

E-print Network

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

Mukhtar, Saqib

202

Journal of Environmental Management 86 (2008) 1426 Combination of multispectral remote sensing, variable rate technology  

E-print Network

, variable rate technology and environmental modeling for citrus pest management Qian Dua , Ni-Bin Changb of agrochemicals to maximize crop yields. Intensive agricultural activities in past decades might have caused that drink it, a number of government programs have been introduced to directly limit its environmental

Du, Jenny (Qian)

203

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

E-print Network

during Labor Muriel Doret, M.D., Ph.D.,1,2 Hannes Helgason, Ph.D.,3 Patrice Abry, Ph.D.,3 Paulo Goncalves multifractal analysis of fetal heart rate (FHR) variability in fetuses with and without acidosis during labor minutes before birth (p

Abry, Patrice

204

Identifying genetic variants for heart rate variability in the acetylcholine pathway.  

PubMed

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

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

2014-01-01

205

Regional variability in the rates of total hip replacement in Spain.  

PubMed

The role of economic resources, distribution of providers, and demography may explain part of the variability found in hip arthroplasty in international surveys. We aimed to investigate the influence of ageing index, health budget, and density of orthopaedic surgeons in the regional variability of the primary and revision THR rate in Spain, where regions decide on the allocation of their health budget.Inpatient database of hip procedures for years 1997 to 2011 was obtained from the Spanish Ministry of Health, segregated for each of the 17 regional health services in Spain. Crude and adjusted rates (direct method with total Spanish population per year) were calculated and used as dependent variables. Ageing index, Health Expenditure of Gross Domestic Product (GDP), and number of orthopaedic surgeons per region were used as independent variables. Negative binomial regression analysis model and Poisson regression were calculated to estimate the risk contribution of the ecological variables.A total of 425,914 hip procedures, with 367,489 primary (mean crude rate = 124 × 105 inhabitants/year) and 58,425 revision hips (21 × 105 inhabitants/year) were included in the analysis. Regional variability was higher than expected in THR in Spain, despite a universal coverage health system in which equity may be challenged in the administration of hip arthroplasty. This was found particularly for primary THR. When hip replacement rates were adjusted for sex and age, the regional ageing index, the density of orthopaedic surgeons and the regional health budget could only partially explain risk ratio changes. PMID:24474410

Padilla-Eguiluz, Norma G; García-Rey, Eduardo; Cordero-Ampuero, Jose; Gómez-Barrena, Enrique

2014-01-01

206

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

Microsoft Academic Search

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

Angela McGaughran; Barbara R. Holland

2010-01-01

207

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

E-print Network

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

208

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

E-print Network

pathological states such as ischemia and myocardial infarction, heart failure, hyperten- sion, diabetes in Heart Rate Variability Signal Processing and Interpretation OVER the past 30 years, heart rate which issued a seminal paper: "Heart rate variability: standards of measure- ment, physiological

209

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

PubMed Central

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

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

2013-01-01

210

Effects of variability and rate on battery charge storage and lifespan  

NASA Astrophysics Data System (ADS)

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

Krieger, Elena Marie

211

The effects of auditory stimulation with music on heart rate variability in healthy women  

PubMed Central

OBJECTIVES: There are no data in the literature with regard to the acute effects of different styles of music on the geometric indices of heart rate variability. In this study, we evaluated the acute effects of relaxant baroque and excitatory heavy metal music on the geometric indices of heart rate variability in women. METHODS: We conducted this study in 21 healthy women ranging in age from 18 to 35 years. We excluded persons with previous experience with musical instruments and persons who had an affinity for the song styles. We evaluated two groups: Group 1 (n?=?21), who were exposed to relaxant classical baroque musical and excitatory heavy metal auditory stimulation; and Group 2 (n?=?19), who were exposed to both styles of music and white noise auditory stimulation. Using earphones, the volunteers were exposed to baroque or heavy metal music for five minutes. After the first music exposure to baroque or heavy metal music, they remained at rest for five minutes; subsequently, they were re-exposed to the opposite music (70-80 dB). A different group of women were exposed to the same music styles plus white noise auditory stimulation (90 dB). The sequence of the songs was randomized for each individual. We analyzed the following indices: triangular index, triangular interpolation of RR intervals and Poincaré plot (standard deviation of instantaneous beat-by-beat variability, standard deviation of the long-term RR interval, standard deviation of instantaneous beat-by-beat variability and standard deviation of the long-term RR interval ratio), low frequency, high frequency, low frequency/high frequency ratio, standard deviation of all the normal RR intervals, root-mean square of differences between the adjacent normal RR intervals and the percentage of adjacent RR intervals with a difference of duration greater than 50 ms. Heart rate variability was recorded at rest for 10 minutes. RESULTS: The triangular index and the standard deviation of the long-term RR interval indices were reduced during exposure to both music styles in the first group and tended to decrease in the second group whereas the white noise exposure decreased the high frequency index. We observed no changes regarding the triangular interpolation of RR intervals, standard deviation of instantaneous beat-by-beat variability and standard deviation of instantaneous beat-by-beat variability/standard deviation in the long-term RR interval ratio. CONCLUSION: We suggest that relaxant baroque and excitatory heavy metal music slightly decrease global heart rate variability because of the equivalent sound level. PMID:23917660

Roque, Adriano L.; Valenti, Vitor E.; Guida, Heraldo L.; Campos, Mônica F.; Knap, André; Vanderlei, Luiz Carlos M.; Ferreira, Lucas L.; Ferreira, Celso; de Abreu, Luiz Carlos

2013-01-01

212

Design of rate control for wireless video telephony applications  

NASA Astrophysics Data System (ADS)

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.

Chen, Zhifeng; Reznik, Yuriy A.

2012-10-01

213

Experiences with leak rate calculations methods for LBB application  

SciTech Connect

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

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

1997-04-01

214

On the Accretion Rates of SW Sextantis Nova-like Variables  

NASA Astrophysics Data System (ADS)

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

Ballouz, Ronald-Louis; Sion, Edward M.

2009-06-01

215

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

PubMed Central

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

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

2014-01-01

216

Necessary conditions for the optimality of variable rate residual vector quantizers  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

217

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

Microsoft Academic Search

Study Objectives: The study goal was to investigate autonomic activity with heart rate variability analysis during different sleep stages in males and females. Design: The study utilized a 2 Groups (males, females) X 4 States (waking, stage 2 sleep, stage 4 sleep, rapid-eye movement sleep) mixed design with one repeated, within-subjects factor (i.e., state). Setting: The study was carried out

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

1999-01-01

218

Heart rate variability patterns before ventricular tachycardia onset in patients with an implantable cardioverter defibrillator  

Microsoft Academic Search

Time- and frequency-domain analysis of heart rate variability (HRV) has been proven effective in describing alteration of autonomic control mechanisms and in identifying patients with increased cardiac and arrhythmic mortality. Patients with implantable cardioverter defibrillators offer the opportunity to evaluate HRV patterns before ventricular tachycardia (VT) and under control conditions. We therefore analyzed time- and frequency-domain parameters of short-term HRV

Federico Lombardi; Alberto Porta; Maurizio Marzegalli; Stefano Favale; Massimo Santini; Antonello Vincenti; Angelo De Rosa

2000-01-01

219

Reliability of heart rate variability measures at rest and during light exercise in children  

Microsoft Academic Search

Objectives: To investigate the reliability of heart rate variability (HRV) measures at rest and during light exercise in children.Methods: Short term (five minute) HRV was assessed in 12 children (11–12 years of age). HRV measures were collected at rest with the children supine, breathing at 12 breaths\\/min, and during exercise on a cycle ergometer while exercising at 25% of peak

R J Winsley; N Armstrong; K Bywater; S G Fawkner

2003-01-01

220

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

PubMed Central

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

2014-01-01

221

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

Microsoft Academic Search

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

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

2011-01-01

222

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

Microsoft Academic Search

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,

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

1995-01-01

223

Effect of exercise mode on heart rate variability during steady state exercise  

Microsoft Academic Search

This study examined the effect of exercise mode on geometrical, and time and frequency domain measures of heart rate variability\\u000a (HRV) during steady-state, moderate intensity exercise of the same HR. Seventeen healthy, active male participants volunteered\\u000a for this study and completed a treadmill \\u000a $$ \\\\dot V{\\\\text{O}}_{{\\\\text{2max}}} $$ determination. One week later, cardiorespiratory, perceptual and HRV measures were recorded during seated

Anthony S. Leicht; Wade H. Sinclair; Warwick L. Spinks

2008-01-01

224

Effect of meditation on scaling behavior and complexity of human heart rate variability  

E-print Network

The heart beat data recorded from samples before and during meditation are analyzed using two different scaling analysis methods. These analyses revealed that mediation severely affects the long range correlation of heart beat of a normal heart. Moreover, it is found that meditation induces periodic behavior in the heart beat. The complexity of the heart rate variability is quantified using multiscale entropy analysis and recurrence analysis. The complexity of the heart beat during mediation is found to be more.

Sarkar, A

2006-01-01

225

Discrimination power of long-term heart rate variability measures for chronic heart failure detection  

Microsoft Academic Search

The aim of this study was to investigate the discrimination power of standard long-term heart rate variability (HRV) measures\\u000a for the diagnosis of chronic heart failure (CHF). The authors performed a retrospective analysis on four public Holter databases,\\u000a analyzing the data of 72 normal subjects and 44 patients suffering from CHF. To assess the discrimination power of HRV measures,\\u000a an

Paolo Melillo; Roberta Fusco; Mario Sansone; Marcello Bracale; Leandro Pecchia

2011-01-01

226

An analytical and computational study of a stochastic adsorption model with variable attachment and detachment rates  

NASA Astrophysics Data System (ADS)

We present a stochastic model for adsorption and evaporation of monomers with applications to optical coatings. We consider a general case of attachment and detachment rates dependent on the overall number of particles in the system. The model is applicable to all dimensions and topologies, and can describe a variety of two-state physical systems. We report analytical results for the time-dependent particle density. We compare our analytical results with experimental data and Monte Carlo simulations.

Mazilu, D. A.; Schwen, E. M.; Mazilu, I.

2015-01-01

227

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

PubMed Central

[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.

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

2014-01-01

228

Twenty-four hour variation in heart rate variability indices derived from fractional differintegration.  

PubMed

Assuming that RR time-series behave as a fractionally differintegrated Gaussian process, García-González et al. (2003) recently proposed new indices for quantifying variability and structure in RR data. One of these was the 'fractional noise quantifier' (fnQ), measuring the departure of an RR time-series from a monofractal structure (i.e. a measure of its multifractality). Sixty-nine participants (aged = 34·5 ± 12·4 years, body mass index (BMI) = 23·9 ± 2·9 kg m(-2) , maximal oxygen uptake rate (V?O2peak ) = 42·4 ± 10·9 ml min(-1)  kg(-1) , 39 males) provided continuous beat-to-beat ECG recordings for a 24-h period. Fractional differintegration was used to quantify fnQ, and heart rate variability was calculated in the time domain. All variables were evaluated during consecutive 1-h periods and also during four 6-h blocks corresponding to morning, afternoon, evening and night periods. Apart from RR, circadian trends in all variables were independent of gender (P = 0·11-0·59). Apart from fnQ, all variables exhibited circadian variation (0·0005

Lewis, Michael J; McNarry, Melitta A

2015-01-01

229

Heart rate variability and baroreflex sensitivity are reduced in chronically undernourished, but otherwise healthy, human subjects.  

PubMed

Alterations in autonomic nerve activity in subjects in a chronically undernourished state have been proposed, but have been inadequately documented. The present study evaluated heart rate and systolic blood pressure variability in the frequency domain in two underweight groups, one of which was undernourished and recruited from the lower socio-economic strata [underweight, undernourished (UW/UN); n =15], while the other was from a high class of socio-economic background [underweight, well nourished (UW/WN); n =17], as well as in normal-weight controls [normal weight, well nourished (NW/WN); n =27]. Baroreflex sensitivity, which is a determinant of heart rate variability, was also assessed. The data indicate that total power (0-0.4 Hz), low-frequency power (0.04-0.15 Hz) and high-frequency power (0.15-0.4 Hz) of RR interval variability were significantly lower in the UW/UN subjects ( P <0.05) than in the NW/WN controls when expressed in absolute units, but not when the low- and high-frequency components were normalized for total power. Baroreflex sensitivity was similarly lower in the UW/UN group ( P <0.05). Heart rate variability parameters in the UW/WN group were generally between those of the UW/UN and NW/WN groups, but were not statistically different from either. The mechanisms that contribute to the observed differences between undernourished and normal-weight groups, and the implications of these differences, remain to be elucidated. PMID:12605590

Vaz, Mario; Bharathi, A V; Sucharita, S; Nazareth, D

2003-03-01

230

Usefulness of the heart-rate variability complex for predicting cardiac mortality after acute myocardial infarction  

PubMed Central

Background Previous studies indicate that decreased heart-rate variability (HRV) is related to the risk of death in patients after acute myocardial infarction (AMI). However, the conventional indices of HRV have poor predictive value for mortality. Our aim was to develop novel predictive models based on support vector machine (SVM) to study the integrated features of HRV for improving risk stratification after AMI. Methods A series of heart-rate dynamic parameters from 208 patients were analyzed after a mean follow-up time of 28 months. Patient electrocardiographic data were classified as either survivals or cardiac deaths. SVM models were established based on different combinations of heart-rate dynamic variables and compared to left ventricular ejection fraction (LVEF), standard deviation of normal-to-normal intervals (SDNN) and deceleration capacity (DC) of heart rate. We tested the accuracy of predictors by assessing the area under the receiver-operator characteristics curve (AUC). Results We evaluated a SVM algorithm that integrated various electrocardiographic features based on three models: (A) HRV complex; (B) 6 dimension vector; and (C) 8 dimension vector. Mean AUC of HRV complex was 0.8902, 0.8880 for 6 dimension vector and 0.8579 for 8 dimension vector, compared with 0.7424 for LVEF, 0.7932 for SDNN and 0.7399 for DC. Conclusions HRV complex yielded the largest AUC and is the best classifier for predicting cardiac death after AMI. PMID:24886422

2014-01-01

231

The interpretation of very high frequency band of instantaneous pulse rate variability during paced respiration  

PubMed Central

Background Pulse rate (PR) indicates heart beat rhythm and contains various intrinsic characteristics of peripheral regulation. Pulse rate variability (PRV) is a reliable method to assess autonomic nervous system function quantitatively as an effective alternative to heart rate variability. However, the frequency range of PRV is limited by the temporal resolution of PR based on heart rate and it is further restricted the exploration of optimal autoregulation frequency based on spectral analysis. Methods Recently, a new novel method, called instantaneous PRV (iPRV), was proposed. iPRV breaks the limitation of temporal resolution and extends the frequency band. Moreover, iPRV provides a new frequency band, called very high frequency band (VHF; 0.4-0.9 Hz). Results The results showed that the VHF indicated the influences of respiratory maneuvers (paced respiration at 6-cycle and 30-cycle) and the nonstationary condition (head-up tilt; HUT). Conclusions VHF is as a potential indication of autoregulation in higher frequency range and with peripheral regulation. It helps for the frequency exploration of cardiovascular autoregulation. PMID:24750578

2014-01-01

232

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

PubMed

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

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

2014-12-01

233

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

PubMed

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

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

2015-01-01

234

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

NASA Technical Reports Server (NTRS)

We studied heart rate (HR), heart rate variability (HRV), and respiratory sinus arrhythmia (RSA) in four male subjects before, during, and after 16 days of spaceflight. The electrocardiogram and respiration were recorded during two periods of 4 min controlled breathing at 7.5 and 15 breaths/min in standing and supine postures on the ground and in microgravity. Low (LF)- and high (HF)-frequency components of the short-term HRV (< or =3 min) were computed through Fourier spectral analysis of the R-R intervals. Early in microgravity, HR was decreased compared with both standing and supine positions and had returned to the supine value by the end of the flight. In microgravity, overall variability, the LF-to-HF ratio, and RSA amplitude and phase were similar to preflight supine values. Immediately postflight, HR increased by approximately 15% and remained elevated 15 days after landing. LF/HF was increased, suggesting an increased sympathetic control of HR standing. The overall variability and RSA amplitude in supine decreased postflight, suggesting that vagal tone decreased, which coupled with the decrease in RSA phase shift suggests that this was the result of an adaptation of autonomic control of HR to microgravity. In addition, these alterations persisted for at least 15 days after return to normal gravity (1G).

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

2003-01-01

235

Calculation of vaporization rates assuming various rate determining steps: Application to the resistojet  

NASA Technical Reports Server (NTRS)

The various steps that could control the vaporization rate of a material are discussed. These steps include the actual vaporization, flow rate of matrix gas, chemical reaction, gas diffusion, and solid state diffusion. The applicable equations have been collected from diverse appropriate sources, and their use is explained. Rate equations are derived for conditions where more than one step is rate controlling. Calculations are made for two model materials: rhenium which vaporizes congruently, and tantalum carbide which vaporizes incongruently. The case of vaporization under thermal gradient conditions is also treated. The existence of a thermal gradient in the resistojet means that the vaporization rate of a material may be only one thousandth of that predicted under isothermal conditions. Calculations show that rhenium might have a 100,000 hr lifetime at temperature in a 2500 C resistojet. Tantalum carbide would have a life of only 660 sec under similar conditions.

May, C. E.

1984-01-01

236

Causes of variability in plasmasphere rotation rate: IMAGE EUV observations (Invited)  

NASA Astrophysics Data System (ADS)

IMAGE EUV observations demonstrate that the plasmasphere usually does not corotate as assumed in simple convection models, even at low L shells. The prevailing hypothesis states that plasmaspheric subcorotation is due to enhanced auroral zone Joule heating which drives equatorward thermospheric winds. As the neutral thermospheric material moves to lower latitudes, it grows farther from the Earth’s spin axis and turns westward to conserve angular momentum. This induces a westward motion in the ionosphere (a subcorotation), which produces a change in the corotation electric field that maps out to the plasmasphere, causing a subcorotation there as well. We test this hypothesis by searching for a correlation between plasmaspheric rotation rates and several geomagnetic indices (used as proxies for enhanced Joule heating in the auroral zone). We carry out a statistical survey of plasmaspheric rotation rates over several months of IMAGE EUV data in 2001, using two different measurement techniques. Azimuthal features such as “notches” are tracked in local time over a single pass of the IMAGE satellite, both visually and using an automated cross-correlation routine. Each technique provides an estimate of the plasmasphere’s rotation rate. We find a weak correlation between rotation rate and Dst, Kp, AE, the midnight boundary index (MBI), and Joule heating estimates from assimilative mapping of ionospheric electrodynamics (AMIE) at L = 2.5, but not at L = 3.5. In general, lower rotation rates correspond to higher auroral and geomagnetic activity. We also make the first direct observation of plasmaspheric superrotation. The rotation rate is found to be highly variable on multi-day timescales, but the typical state of the plasmasphere is subcorotation, with inferred mean values ranging from 88% to 95% of corotation, depending on L shell. In addition, a statistical analysis shows that rotation rates near dusk are generally lower than those at dawn, suggesting that local time and magnetospheric convection contribute to the variation in rotation rate as well. We conclude that the cause of variability in plasmaspheric rotation rate is a combination of storm phase, local-time-dependent convection, and westward ionospheric drift.

Galvan, D. A.; Moldwin, M.; Sandel, B. R.; Crowley, G.

2010-12-01

237

Heart rate variability and biological age: implications for health and gaming.  

PubMed

Accurate and inexpensive psychophysiological equipment and software are needed to measure and monitor the autonomic nervous system for gaming and therapeutic purposes. The purpose of this study was to determine whether heart rate variability (HRV) derived from photoplethesmography (PPG) technology was predictive of autonomic nervous system (ANS) aging or biological age. Second, we sought to determine which HRV variable was most predictive of ANS change and aging. To test our hypotheses, we first conducted a criterion related validity study by comparing parameters of a 5 minute resting HRV test obtained from electrocardiography (ECG), the current "gold standard," with PPG technologies, and found them to be significantly correlated (r?0.92) on all parameters during a resting state. PPG was strongly correlated to ECG on all HRV parameters during a paced six breaths per minute deep breathing test (r?0.98). Further analysis revealed that maximum variation of heart rate had the highest negative correlation (r=-0.67) with age. We conclude that PPG is comparable to ECG in accuracy, and maximum variation of heart rate derived from a paced breathing test can be considered a marker of biological aging. Therapeutic interventions and games designed to reduce dysfunction in the ANS can now be developed using accurate physiological data. PMID:23574369

Russoniello, Carmen V; Zhirnov, Yevgeniy N; Pougatchev, Vadim I; Gribkov, Evgueni N

2013-04-01

238

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

PubMed Central

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.

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

2014-01-01

239

Controlling Variable Emittance (MEMS) Coatings for Space Applications  

NASA Technical Reports Server (NTRS)

Small spacecraft, including micro and nanosats, as they are envisioned for future missions, will require an alternative means to achieve thermal control due to their small power and mass budgets. One of the proposed alternatives is Variable Emittance (Vari-E) Coatings for spacecraft radiators. Space Technology-5 (ST-5) is a technology demonstration mission through NASA Goddard Space Flight Center (GSFC) that will utilize Vari-E Coatings. This mission involves a constellation of three (3) satellites in a highly elliptical orbit with a perigee altitude of approximately 200 kilometers and an apogee of approximately 38,000 kilometers. Such an environment will expose the spacecraft to a wide swing in the thermal and radiation environment of the earth's atmosphere. There are three (3) different technologies associated with this mission. The three technologies are electrophoretic, electrochromic, and Micro ElectroMechanical Systems (MEMS). The ultimate goal is to make use of Van-E coatings, in order to achieve various levels of thermal control. The focus of this paper is to highlight the Vari-E Coating MEMS instrument, with an emphasis on the Electronic Control Unit responsible for operating the MEMS device. The Test & Evaluation approach, along with the results, is specific for application on ST-5, yet the information provides a guideline for future experiments and/or thermal applications on the exterior structure of a spacecraft.

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

2003-01-01

240

PERFORMANCE ANALYSIS OF LOW RATE WIRELESS TECHNOLOGIES FOR MEDICAL APPLICATIONS  

E-print Network

medical devices, connections are mainly based on the RS-232 port interfaces that are made permanently working group is currently developing standard specifications for medical device communication focusingPERFORMANCE ANALYSIS OF LOW RATE WIRELESS TECHNOLOGIES FOR MEDICAL APPLICATIONS N. Golmie, D

241

Workshop on Thermonuclear Reaction Rates for Astrophysics Applications  

E-print Network

rates key reactions: experiment and theory s-, r- and p-process nucleosynthesis nuclear experiments. Research activities carried out at INP include nuclear structure, nuclear reactions and astrophysics of Excellence in Low-energy Ion-Beam Research and Applications (LIBRA). Location NCSR "Demokritos" is located

242

High dose rate endobronchial brachytherapy using a new applicator  

Microsoft Academic Search

Background and purpose: To obtain adequate spatial dose distribution for endobronchial brachytherapy, we applied reference dose points according to the bronchial diameter. For this purpose, we devised a new applicator of which the source transfer tube is contained in the center of the lumen for high dose rate (HDR) brachytherapy.Materials and methods: Thirty-nine patients with endobronchial cancer underwent endobronchial brachytherapy

Yoshihito Nomoto; Kazufusa Shouji; Shun Toyota; Masahiro Sasaoka; Shuuichi Murashima; Maki Ooi; Kan Takeda; Tsuyoshi Nakagawa

1997-01-01

243

Why Do State Disability Application Rates Vary Over Time?  

Microsoft Academic Search

Social Security Disability Insurance (SSDI) applicatons and benefit receipts vary greatly by state, which has led to concerns about potential inconsistencies in the way that states apply disability standards. An earlier brief concluded that more than 70 percent of the variation across states in SSDI application rates is explained by state health, demographic, and employment characteristics; state policies and politics

Norma B. Coe; Kelly Haverstick; Alicia H. Munnell; Anthony Webb

2012-01-01

244

Heart rate variability on antihypertensive drugs in black patients living in sub-Saharan Africa  

PubMed Central

Background Compared with Caucasians, African Americans have lower heart rate variability (HRV) in the high-frequency domain, but there are no studies in blacks born and living in Africa. Methods In the Newer versus Older Antihypertensive agents in African Hypertensive patients trial (NCT01030458), patients (30–69 years) with uncomplicated hypertension (140–179/90–109 mmHg) were randomized to single-pill combinations of bisoprolol/hydrochlorothiazide (R) or amlodipine/valsartan (E). 72 R and 84 E patients underwent 5-min ECG recordings at randomization and 8, 16 and 24 weeks. HRV was determined by fast Fourier transform and autoregressive modelling. Results Heart rate decreased by 9.5 beats/min in R patients with no change in E patients (? 2.2 beats/min). R patients had reduced total (? 0.13 ms²; p = 0.0038) and low-frequency power (? 3.6 nu; p = 0.057), higher high-frequency (+ 3.3 nu; p = 0.050) and a reduced low- to high-frequency ratio (? 0.08; p = 0.040). With adjustment for heart rate, these differences disappeared, except for the reduced low-frequency power in the R group (? 4.67 nu; p = 0.02). Analyses confined to 39 R and 47 E patients with HRV measurements at all visits or based on autoregressive modelling were confirmatory. Conclusion In native black African patients, antihypertensive drugs modulate HRV, an index of autonomous nervous tone. However, these effects were mediated by changes in heart rate except for low-frequency variability, which was reduced on beta blockade independent of heart rate. PMID:24066715

Osakwe, Chukwunomso E.; Jacobs, Lotte; Anisiuba, Benedict C.; Ndiaye, Mouhamado B.; Lemogoum, Daniel; Ijoma, Chinwuba K.; Kamdem, Marius M.; Thijs, Lutgarde; Boombhi, Hilaire J.; Kaptue, Joseph; Kolo, Philip M.; Mipinda, Jean B.; Odili, Augustine N.; Ezeala-Adikaibe, Birinus; Kingue, Samuel; Omotoso, Babatunde A.; Ba, Serigne A.; Ulasi, Ifeoma I.; M’buyamba-Kabangu, Jean-Rene

2014-01-01

245

76 FR 72731 - John Hancock Variable Insurance Trust, et al.; Notice of Application  

Federal Register 2010, 2011, 2012, 2013

...Act Release No. 29865; File No. 812-13621] John Hancock Variable Insurance Trust, et al.; Notice...lending and borrowing facility. Applicants: John Hancock Variable Insurance Trust, John Hancock Funds II, John Hancock Funds III,...

2011-11-25

246

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

PubMed

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

Paul, Maman; Garg, Kanupriya

2012-06-01

247

Children's Sleep and Autonomic Function: Low Sleep Quality Has an Impact on Heart Rate Variability  

PubMed Central

Objectives: Short sleep duration and poor sleep quality in children have been associated with concentration, problem behavior, and emotional instability, but recently also with disrupted autonomic nervous function, which predicts cardiovascular health. Heart rate variability (HRV) was used as noninvasive indicator of autonomic function to examine the influence of sleep. Design: Cross-sectional and longitudinal observational study on the effect of sleep on HRV Participants: Belgian children (5-11 years) of the ChiBS study in 2010 (N = 334) and 2011 (N = 293). Interventions: N/A. Methods: Sleep duration was reported and in a subgroup sleep quality (efficiency, latency, awakenings) was measured with accelerometry. High-frequency (HF) power and autonomic balance (LF/HF) were calculated on supine 5-minute HRV measurements. Stress was measured by emotion and problem behavior questionnaires. Sleep duration and quality were used as HRV predictors in corrected cross-sectional and longitudinal regressions. Stress was tested as mediator (intermediate pathway) or moderator (interaction) in sleep-HRV associations. Results: In both cross-sectional and longitudinal analyses, long sleep latency could predict lower HF (parasympathetic activity), while nocturnal awakenings, sleep latency, low sleep efficiency, and low corrected sleep duration were related to higher LF/HF (sympathetic/parasympathetic balance). Parental reported sleep duration was not associated with HRV. The significances remained after correction for stress. Stress was not a mediator, but a moderator (enhancer) in the relationship between sleep quality and HRV. Conclusions: Low sleep quality but not parent-reported low sleep duration leads to an unhealthier heart rate variability pattern (sympathetic over parasympathetic dominance). This stresses the importance of good sleep quality for cardiovascular health in children. Citation: Michels N; Clays E; De Buyzere M; Vanaelst B; De Henauw S; Sioen I. Children's sleep and autonomic function: low sleep quality has an impact on heart rate variability. SLEEP 2013;36(12):1939-1946. PMID:24293769

Michels, Nathalie; Clays, Els; De Buyzere, Marc; Vanaelst, Barbara; De Henauw, Stefaan; Sioen, Isabelle

2013-01-01

248

Bivalve growth rate and isotopic variability across the Barents Sea Polar Front  

NASA Astrophysics Data System (ADS)

Analysis of bivalve shell increments provides a means to reconstruct long-term patterns in growth histories and assess factors that regulate marine ecosystems, while tissue stable isotopes are indicators of food sources and trophic dynamics. We examined shell growth patterns and tissue stable isotopic composition (?13C and ?15N) of the hairy cockle (Ciliatocardium ciliatum) in the northwest Barents Sea to evaluate the influence of different water masses and the Polar Front on growth rates and food sources and to assess the influence of climatic variability on ecological processes over seasonal to decadal scales. Shell growth rates were highest in Atlantic water, intermediate in Arctic water, and lowest at the Polar Front. Temporal patterns of ontogenetically-adjusted growth (SGI) were negatively correlated with the Atlantic Multidecadal Oscillation (AMO), local precipitation and ice-free days. The highest growth occurred during colder periods with more sea ice, while lower growth was associated with warmer periods and less sea ice. Stable isotope values of lipid-extracted tissues from Atlantic water cockles were enriched in ?13C by up to 2.1‰ and ?15N by 1.5‰ compared to animals from Arctic waters. Distinct seasonal and water mass variations in stable isotopic values reflect spatial and temporal variability in food supplies to the bivalves in this region on small spatial scales. Overall, Atlantic waters supported the highest growth rates, the most complex trophic webs, and the greatest sensitivity to interannual variability in environmental conditions. Bivalves from Arctic waters were the most distinct of the three groups in their response to regional climate forcing and local environmental manifestations of those conditions. The Polar Front exhibits growth and isotopic characteristics predominantly of the Atlantic domain. These results demonstrate that integrating results of sclerochronological and stable isotopic analyses of benthic bivalves provide independent, corroborative lines of evidence and added insight into the ecological function of these systems when assessing potential effects of changes in water mass distributions in the Barents Sea.

Carroll, Michael L.; Ambrose, William G.; Locke V, William L.; Ryan, Stuart K.; Johnson, Beverly J.

2014-02-01

249

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

NASA Astrophysics Data System (ADS)

In order to meet the need of image shooting with CCD in unmanned aerial vehicles, a real-time high resolution CCD data processing system based on variable frame rate is designed. The system is consisted of three modules: CCD control module, data processing module and data display module. In the CCD control module, real-time flight parameters (e.g. flight height, velocity and longitude) should be received from GPS through UART (Universal Asynchronous Receiver Transmitter) and according to the corresponding flight parameters, the variable frame rate is calculated. Based on the calculated variable frame rate, CCD external synchronization control impulse signal is generated in the control of FPGA and then CCD data is read out. In the data processing module, data segmentation is designed to extract ROI (region of interest), whose resolution is equal to valid data resolution of HDTV standard conforming to SMPTE (1080i). On one hand, Ping-pong SRAM storage controller is designed in FPGA to real-time store ROI data. On the other hand, according to the need of intelligent observing, changeable window position is designed, and a flexible area of interest is obtained. In the real-time display module, a special video encoder is used to accomplish data format conversion. Data after storage is packeted to HDTV format by creating corresponding format information in FPGA. Through inner register configuration, high definition video analog signal is implemented. The entire system has been implemented in FPGA and validated. It has been used in various real-time CCD data processing situations.

Chen, Su-ting

2009-07-01

250

Fixed-quality/variable bit-rate on-board image compression for future CNES missions  

NASA Astrophysics Data System (ADS)

The huge improvements in resolution and dynamic range of current [1][2] and future CNES remote sensing missions (from 5m/2.5m in Spot5 to 70cm in Pleiades) illustrate the increasing need of efficient on-board image compressors. Many techniques have been considered by CNES during the last years in order to go beyond usual compression ratios: new image transforms or post-transforms [3][4], exceptional processing [5], selective compression [6]. However, even if significant improvements have been obtained, none of those techniques has ever contested an essential drawback in current on-board compression schemes: fixed-rate (or compression ratio). This classical assumption provides highly-predictable data volumes that simplify storage and transmission. But on the other hand, it demands to compress every image-segment (strip) of the scene within the same amount of data. Therefore, this fixed bit-rate is dimensioned on the worst case assessments to guarantee the quality requirements in all areas of the image. This is obviously not the most economical way of achieving the required image quality for every single segment. Thus, CNES has started a study to re-use existing compressors [7] in a Fixed-Quality/Variable bit-rate mode. The main idea is to compute a local complexity metric in order to assign the optimum bit-rate to comply with quality requirements. Consequently, complex areas are less compressed than simple ones, offering a better image quality for an equivalent global bit-rate. "Near-lossless bit-rate" of image segments has revealed as an efficient image complexity estimator. It links quality criteria and bit-rates through a single theoretical relationship. Compression parameters are thus automatically computed in accordance with the quality requirements. In addition, this complexity estimator could be implemented in a one-pass compression and truncation scheme.

Camarero, Roberto; Delaunay, Xavier; Thiebaut, Carole

2012-10-01

251

Biomedical Teleacupuncture between China and Austria Using Heart Rate Variability—Part 2: Patients with Depression  

PubMed Central

It has been shown in previous studies that the autonomic nervous system can be affected by acupuncture. Within this study, teleacupuncture between China and Austria is used for quantifying the effects of heart rate (HR) and heart rate variability (HRV) in 33 Chinese patients (27 females, 6 males; mean age ± SD 49.5 ± 13.1 years; range 22–72 years) suffering from depression. Electrocardiographic signals before, during, and after acupuncture at the acupoint Baihui (GV20) were recorded in Harbin and analyzed in Graz using teleacupuncture. HRV data were analyzed in the time and frequency domain. Mean HR decreased significantly (P < 0.05) during and after acupuncture, whereas total HRV increased significantly after the third acupuncture stimulation period (P < 0.05) and also 5–10 minutes after (P < 0.05) acupuncture. The study shows that HRV could be a useful parameter for quantifying clinical effects of acupuncture on the autonomic nervous system. PMID:22570670

Litscher, Gerhard; Cheng, Guangyu; Wang, Lu; Cheng, Weiping; Su, Hang; Niu, Qianqian; Zou, Tianyu; Wang, Yongyue; Feng, Xiao; Gaischek, Ingrid; Sheng, Zemin; Kuang, Haixue

2012-01-01

252

A new algorithm for wavelet-based heart rate variability analysis  

E-print Network

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...

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

2014-01-01

253

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

PubMed Central

We investigated pupillary light reflex (PLR) in 152 children with ASD, 116 typically developing (TD) children, and 36 children with non-ASD neurodevelopmental disorders (NDDs). Heart rate variability (HRV) was measured simultaneously to study potential impairments in the autonomic nervous system (ANS) associated with ASD. The results showed that the ASD group had significantly longer PLR latency, reduced relative constriction amplitude, and shorter constriction/redilation time than those of the TD group. Similar atypical PLR parameters were observed in the NDD group. A significant age effect on PLR latency was observed in children younger than 9 years in the TD group, but not in the ASD and NDD groups. Atypical HRV parameters were observed in the ASD and NDD groups. A significant negative correlation existed between the PLR constriction amplitude and average heart rate in children with an ASD, but not in children with typical development. PMID:23248075

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

2012-01-01

254

Individual differences in heart rate variability are associated with the avoidance of negative emotional events.  

PubMed

Although the emotional outcome of a choice generally affects subsequent decisions, humans can inhibit the influence of emotion. Heart rate variability (HRV) has emerged as an objective measure of individual differences in the capacity for inhibitory control. In the present study, we investigated how individual differences in HRV at rest are associated with the emotional effects of the outcome of a choice on subsequent decision making using a decision-making task in which emotional pictures appeared as decision outcomes. We used a reinforcement learning model to characterize the observed behaviors according to several parameters, namely, the learning rate and the motivational value of positive and negative pictures. Consequently, we found that individuals with a lower resting HRV exhibited a greater negative motivational value in response to negative pictures, suggesting that these individuals tend to avoid negative pictures compared with individuals with a higher resting HRV. PMID:25457639

Katahira, Kentaro; Fujimura, Tomomi; Matsuda, Yoshi-Taka; Okanoya, Kazuo; Okada, Masato

2014-12-01

255

Method for controlling a rate of changing an RPM ratio in a continuously variable transmission  

SciTech Connect

A method is described for controlling a rate of changing an RPM ratio in a continuously variable transmission connected to an engine in a vehicle, the transmission having a driving pulley mounted on an input shaft, the driving pulley comprising a fixed member and a movable member, the movable member being actuated by an hydraulic cylinder to form a V-shaped opening between the movable member and the fixed member, a driven pulley mounted on an output shaft, the driven pulley comprising another fixed member and another movable member. The another movable member is similarly actuated by another hydraulic cylinder supplied with a line pressure to form another V-shaped opening between the another movable member and the another fixed member and an endless belt member spanning the pulleys so that an effective diameter of the pulleys can be varied at different rates with regard to each other so that different speed ratios can be obtained.

Niwa, T.; Gono, T.; Osanai, A.

1986-04-29

256

Changing Geomagnetic Field and Heart Rates Variability in Healthy Volunteers: A Pilot Study  

NASA Astrophysics Data System (ADS)

Space Climate is an interdisciplinary science that deals with the long-term change in the Sun, and its effects in the near-Earth environment, including possible effects on human health. This paper will present the first results from simultaneous experiments performed at 3 different locations - Sofia, Bulgaria 42° 40' N 23° 20' E; Moscow, Russia 55° 45' N 37° 36‘ E and Arkhangelsk, Russia 64° 34' N / 40° 32' E. Subjects are 5 healthy volunteers, women, mean age 39,4 years. The experiments are part of the project “Heliobiology” (2011 - 2015) that reflects the intense interest towards the influence of solar activity and meteorology on the human health. The aim of the experiments is to study the degree of conjugation of the heart rate variability and the variations of the geomagnetic field. To minimize the experimental bias one and the same hard- and software were applied during the testing. ECG signals were recorder via "KARDI-2", the software package is "Ecosan-2007", both developed by "Medical Computer Systems", Zelenograd, Russia. The duration of the observations ranged from 60 to 120 minutes. A comparison of the dynamics of the minute variations of the heart rate with the horizontal components of the geomagnetic field vector revealed a synchronization of some of the research parameters as well as specific individual differences. Despite of the small sample size (5 subjects per 8 measures), in over 70% of the experimental data a similar patterns of variation of geophysical and heart rate variability were recorded. The experiments discussed involved healthy volunteers, i.e. people that have good adaptation reserves, and the response to variation of geomagnetic field will not push them beyond the physiological norms. The observed effect of synchronization of heart rate fluctuations of healthy subjects with fluctuations of geomagnetic field may give an effective tool to address further one especially interesting problems - the mechanism of geomagnetic sensitivity.

Jordanova, Malina; Zenchenko, Tatiana; Poskotinova, Lilia; Medvedeva, Anna; Uzunov, Todor; Alenikova, Alexandra

257

Application of semiclassical methods to reaction rate theory  

SciTech Connect

This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e. most reactions. Second, we have developed a method to describe the fluctuations of decay rates of individual energy states from the average RRKM rate in systems where the direct calculation of individual rates would be impossible. Combined with the semiclassical theory this latter effort has provided a direct comparison to the experimental results of Moore and coworkers. In SCTST, the Hamiltonian is expanded about the barrier and the ``good`` action-angle variables are obtained perturbatively; a WKB analysis of the effectively one-dimensional reactive direction then provides the transmission probabilities. The advantages of this local approximate treatment are that it includes tunneling effects and anharmonicity, and it systematically provides a multi-dimensional dividing surface in phase space. The SCTST thermal rate expression has been reformulated providing increased numerical efficiency (as compared to a naive Boltzmann average), an appealing link to conventional transition state theory (involving a ``prereactive`` partition function depending on the action of the reactive mode), and the ability to go beyond the perturbative approximation.

Hernandez, R.

1993-11-01

258

Influence of type 2 diabetes on symbolic analysis and complexity of heart rate variability in men  

PubMed Central

Background Individuals with diabetes may develop cardiac autonomic dysfunction that may be evaluated by heart rate variability (HRV). The aim was evaluated heart rate variability (HRV) of individuals with type 2 diabetes, without cardiovascular autonomic neuropathy (CAN), in response to active postural maneuver by means of nonlinear analysis (symbolic analysis, Shannon and conditional entropy) and correlate HRV parameters between them, glycated hemoglobin and diabetes duration. Methods Nineteen men with type 2 diabetes without CAN (T2D) and nineteen healthy men (CG), age-range from 40 to 60 years were studied. We assessed HRV in supine and orthostatic position using symbolic analysis (0V%, 1V%, 2LV% and 2UV%), Shannon and conditional entropy (SE and NCI). Results In supine position T2D presented higher sympathetic modulation (0V%) than CG. However, there was not any difference between groups for indexes of complexity (SE and NCI). Furthermore, T2D presented a preserved response of cardiac autonomic modulation after active postural maneuver. Conclusions The present study showed that individuals with type 2 diabetes without CAN presented higher cardiac sympathetic modulation. However, the complexity of HRV was not influenced by imbalance of the autonomic modulation in individuals with type 2 diabetes. In addition, the response of autonomic nervous system in the heart remains preserved after active postural maneuver in individuals with type 2 diabetes, possibly due to the lack of CAN in this group. PMID:24485048

2014-01-01

259

Interpretation of Normalized Spectral Heart Rate Variability Indices In Sleep Research: A Critical Review  

PubMed Central

The normalized spectral heart rate variability (HRV) measures low-frequency (LF)nu and high-frequency (HF)nu are frequently used in contemporary sleep research studies to quantify modulation of the sympathetic and parasympathetic branches of the autonomic nervous system. The purpose of this tutorial and methodologic critique is to concisely demonstrate the structural algebraic redundancy inherent in the normalized spectral HRV measures with respect to each other, and also with respect to the well-known HRV index of sympathovagal balance, LF:HF ratio. The statistical problems and interpretational paradoxes related to the mathematical definitions of LFnu and HFnu are briefly outlined. Examples of use of normalized spectral HRV measures in recent articles from the sleep-relevant research literature are critically reviewed. LFnu, HFnu, and LF:HF ratio should be considered equivalent carriers of information about sympathovagal balance. Citation: Burr RL. Interpretation of normalized spectral heart rate variability indices in sleep research: a critical review. SLEEP 2007;30(7):913-919. PMID:17682663

Burr, Robert L.

2007-01-01

260

Sleep Quality Estimation based on Chaos Analysis for Heart Rate Variability  

NASA Astrophysics Data System (ADS)

In this paper, we propose an algorithm to estimate sleep quality based on a heart rate variability using chaos analysis. Polysomnography(PSG) is a conventional and reliable system to diagnose sleep disorder and to evaluate its severity and therapeatic effect, by estimating sleep quality based on multiple channels. However, a recording process requires a lot of time and a controlled environment for measurement and then an analyzing process of PSG data is hard work because the huge sensed data should be manually evaluated. On the other hand, it is focused that some people make a mistake or cause an accident due to lost of regular sleep and of homeostasis these days. Therefore a simple home system for checking own sleep is required and then the estimation algorithm for the system should be developed. Therefore we propose an algorithm to estimate sleep quality based only on a heart rate variability which can be measured by a simple sensor such as a pressure sensor and an infrared sensor in an uncontrolled environment, by experimentally finding the relationship between chaos indices and sleep quality. The system including the estimation algorithm can inform patterns and quality of own daily sleep to a user, and then the user can previously arranges his life schedule, pays more attention based on sleep results and consult with a doctor.

Fukuda, Toshio; Wakuda, Yuki; Hasegawa, Yasuhisa; Arai, Fumihito; Kawaguchi, Mitsuo; Noda, Akiko

261

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

PubMed

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

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

2014-07-01

262

Frequency range extension of spectral analysis of pulse rate variability based on Hilbert-Huang transform.  

PubMed

Heart rate variability (HRV) is a well-accepted indicator for neural regulatory mechanisms in cardiovascular circulation. Its spectrum analysis provides the powerful means of observing the modulation between sympathetic and parasympathetic nervous system. The timescale of HRV is limited by discrete beat-to-beat time intervals; therefore, the exploration region of frequency band of HRV spectrum is relatively narrow. It had been proved that pulse rate variability (PRV) is a surrogate measurement of HRV in most of the circumstances. Moreover, arterial pulse wave contains small oscillations resulting from complex regulation of cardiac pumping function and vascular tone at higher frequency range. This study proposed a novel instantaneous PRV (iPRV) measurement based on Hilbert-Huang transform. Fifteen healthy subjects participated in this study and received continuous blood pressure wave recording in supine and passive head-up tilt. The result showed that the very-high-frequency band (0.4-0.9 Hz) varied during head-up tilt and had strong correlation (r = 0.77) with high-frequency band and medium correlation (r = 0.643) with baroreflex sensitivity. The very-high-frequency band of iPRV helps for the exploration of non-stationary autoregulation and provides the non-stationary spectral evaluation of HRV without distortion or information loss. PMID:24435320

Chang, Chia-Chi; Hsiao, Tzu-Chien; Hsu, Hung-Yi

2014-04-01

263

Heart rate variability in sleeping preterm neonates exposed to cool and warm thermal conditions.  

PubMed

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

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

2013-01-01

264

Automated detection of perinatal hypoxia using time-frequency-based heart rate variability features.  

PubMed

Perinatal hypoxia is a cause of cerebral injury in foetuses and neonates. Detection of foetal hypoxia during labour based on the pattern recognition of heart rate signals suffers from high observer variability and low specificity. We describe a new automated hypoxia detection method using time-frequency analysis of heart rate variability (HRV) signals. This approach uses features extracted from the instantaneous frequency and instantaneous amplitude of HRV signal components as well as features based on matrix decomposition of the signals' time-frequency distributions using singular value decomposition and non-negative matrix factorization. The classification between hypoxia and non-hypoxia data is performed using a support vector machine classifier. The proposed method is tested on a dataset obtained from a newborn piglet model with a controlled hypoxic insult. The chosen HRV features show strong performance compared to conventional spectral features and other existing methods of hypoxia detection with a sensitivity 93.3 %, specificity 98.3 % and accuracy 95.8 %. The high predictive value of this approach to detecting hypoxia is a substantial step towards developing a more accurate and reliable hypoxia detection method for use in human foetal monitoring. PMID:24272142

Dong, Shiying; Boashash, Boualem; Azemi, Ghasem; Lingwood, Barbara E; Colditz, Paul B

2014-02-01

265

Rate of Decrease of Genetic Variability in a Two-Dimensional Continuous Population of Finite Size  

PubMed Central

The rate of decay of genetic variability was investigated for two-dimensional continuous populations of finite size. The exact value of the rate involves a rather complicated expression (formula (4-1)). However, numerical examples indicate that in a population habitat size L x L and density D, the rate is approximately equal to (see PDF) where ?2 is the variance of dispersion distance assuming isotropical migration. The value given in (2) is equal to that of a panmictic population of size DL2. It is remarkable that whether the rate assumes the value given by (1) or by (2) depends only on D?2 (a local property), which is independent of the habitat size. Since, in a one-dimensional population, this depends on both D?2 and the habitat size, there is an essential difference between the two types of population structure.—The function giving the probability of two homologous genes separated by a given distance being different alleles was also obtained, (formula (5-1)). PMID:5034774

Maruyama, Takeo

1972-01-01

266

Climate trends and variability of rain rate derived from long-term measurements in Norway  

NASA Astrophysics Data System (ADS)

systems are affected by rainfall, and the attenuation increases significantly with rain rate and frequency. Above about 10 GHz rainfall must generally be considered for estimating expected link availability with sufficient attenuation margin included. Rain rate is a key factor, and depending on climate, it will dictate the possible path length and other factors such as antenna size, for the planned performance of a system that operates at higher frequencies than about 10 GHz. This paper presents results from an analysis of Norwegian tipping bucket rain gauge data from 1967 to 2013. It is found that the rain rate currently used by the Radiocommunication Sector of the International Telecommunication Union recommendation for attenuation prediction, R0.01—the rate exceeded for 0.01% of an average year—has actually increased in all parts of the country from where long-term data exist. Moreover, the year to year variability is significant. The increase may well be seen as a consequence of climate change. Such a change may cause higher attenuation effects than expected when radio links are designed following "normal" dimensioning procedures.

Tjelta, Terje; Mamen, Jostein

2014-09-01

267

Effect of Icodextrin on Heart Rate Variability in Diabetic Patients on Peritoneal Dialysis  

PubMed Central

? Introduction: Spectral analysis of heart rate variability is a noninvasive method for evaluating autonomic cardiovascular dysfunction under various clinical conditions, such as in dialysis patients, in whom an imbalance between the sympathetic and parasympathetic nervous system appears to be an important risk factor for sudden cardiovascular death and arrhythmia. ? Objective: We compared the effect of icodextrin-based dialysis solution, an option that allows for better metabolic and fluid overload control, with that of glucose-based dialysis fluid on sympathetic and parasympathetic activity in the heart, as assessed by heart rate variability, in diabetic patients on peritoneal dialysis (PD). ? Methods: This secondary analysis uses data from a randomized controlled trial in diabetic PD patients with high or high-average peritoneal transport using icodextrin-based (ICO group, n = 30) or glucose-based (GLU group, n = 29) solutions for the long dwell. All patients underwent 24-hour electrocardiographic Holter monitoring at baseline, and at 6 and 12 months of follow-up. ? Results: We observed no significant differences between the groups in most of the variables analyzed, although values were, in general, below reference values. In the ICO group, total power and both low- and high-frequency power in normalized units increased, but the percentage of RR intervals with variation of more than 50 ms declined over time; in the GLU group, all those values declined. Plasma catecholamine levels were higher at baseline and declined over time. ? Conclusions: These results indicate a partial recovery of sympathetic activity in the ICO group, probably because of better extracellular fluid control and lower exposure to glucose with the use of icodextrin-based dialysis solutions. PMID:24525598

Orihuela, Oscar; de Jesús Ventura, María; Ávila-Díaz, Marcela; Cisneros, Alejandra; Vicenté-Martínez, Marlén; Furlong, María-del-Carmen; García-González, Zuzel; Villanueva, Diana; Alcántara, Guadalupe; Lindholm, Bengt; García-López, Elvia; Villanueva, Cleva; Paniagua, Ramón

2014-01-01

268

Statistical variability and confidence intervals for planar dose QA pass rates  

SciTech Connect

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.

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

269

Heart Rate Variability for Evaluating Vigilant Attention in Partial Chronic Sleep Restriction  

PubMed Central

Study Objectives: Examine the use of spectral heart rate variability (HRV) metrics in measuring sleepiness under chronic partial sleep restriction, and identify underlying relationships between HRV, Karolinska Sleepiness Scale ratings (KSS), and performance on the Psychomotor Vigilance Task (PVT). Design: Controlled laboratory study. Setting: Experimental laboratory of the Brain Work Research Centre of the Finnish Institute of Occupational Health, Helsinki, Finland. Participants: Twenty-three healthy young males (mean age ± SD = 23.77 ± 2.29). Interventions: A sleep restriction group (N = 15) was subjected to chronic partial sleep restriction with 4 h sleep for 5 nights. A control group (N = 8) had 8 h sleep on all nights. Measurements and Results: Based on a search over all HRV frequency bands in the range [0.00, 0.40] Hz, the band [0.01, 0.08] Hz showed the highest correlation for HRV–PVT (0.60, 95% confidence interval [0.49, 0.69]) and HRV–KSS (0.33, 95% confidence interval [0.16, 0.46]) for the sleep restriction group; no correlation was found for the control group. We studied the fraction of variance in PVT explained by HRV and a 3-component alertness model, containing circadian and homeostatic processes coupled with sleep inertia, respectively. HRV alone explained 33% of PVT variance. Conclusions: The findings suggest that HRV spectral power reflects vigilant attention in subjects exposed to partial chronic sleep restriction. Citation: Henelius A, Sallinen M, Huotilainen M, Müller K, Virkkala J, Puolamäki K. Heart rate variability for evaluating vigilant attention in partial chronic sleep restriction. SLEEP 2014;37(7):1257-1267. PMID:24987165

Henelius, Andreas; Sallinen, Mikael; Huotilainen, Minna; Müller, Kiti; Virkkala, Jussi; Puolamäki, Kai

2014-01-01

270

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

PubMed Central

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

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

2012-01-01

271

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

PubMed Central

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

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

2013-01-01

272

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

E-print Network

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

Paris-Sud XI, Université de

273

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 ...

274

Modeling Passing Rates on a Computer-Based Medical Licensing Examination: An Application of Survival Data Analysis  

ERIC Educational Resources Information Center

The purpose of this article was to model United States Medical Licensing Examination (USMLE) Step 2 passing rates using the Cox Proportional Hazards Model, best known for its application in analyzing clinical trial data. The number of months it took to pass the computer-based Step 2 examination was treated as the dependent variable in the model.…

de Champlain, Andre F.; Winward, Marcia L.; Dillon, Gerard F.; de Champlain, Judy E.

2004-01-01

275

Impacts of obesity and stress on neuromuscular fatigue development and associated heart rate variability.  

PubMed

Objectives:Obesity and stress are independently associated with decrements in neuromuscular functions. The present study examined the interplay of obesity and stress on neuromuscular fatigue and associated heart rate variability (HRV).Methods:Forty-eight non-obese (18.5rate of strength loss), perceived effort and mental demand, heart rate and temporal (RMSSD: root mean square of successive differences between N-N intervals) and spectral (LF/HF: ratio of low to high frequency) indices of HRV.Results:Stress negatively affected endurance time (P<0.0001) and rate of strength loss (P=0.029). In addition, significant obesity × stress interactions were found on endurance time (P=0.0073), rate of strength loss (P=0.027) and perceived effort (P=0.026), indicating that stress increased fatigability, particularly in the obese group. Both obesity (P=0.001) and stress (P=0.033) independently lowered RMSSD. Finally, stress increased LF/HF ratio (P=0.028) and the interaction of stress and obesity (P=0.008) indicated that this was augmented in the obese group.Discussion:The present study provides the first evidence that stress-related neuromuscular fatigue development is accelerated in obese individuals. In addition, the stress condition resulted in poorer HRV indices, which is indicative of autonomic dysfunction, particularly in the obese group. These findings indicate that workers are more susceptible to fatigue in high-stress work environments, particularly those with higher BMI, which can increase the risk of musculoskeletal injuries as well as cardiovascular diseases in this population.International Journal of Obesity advance online publication, 2 September 2014; doi:10.1038/ijo.2014.127. PMID:25042859

Mehta, R K

2014-07-21

276

Heart rate variability explored in the frequency domain: A tool to investigate the link between heart and behavior  

Microsoft Academic Search

The neural regulation of circulatory function is mainly effected through the interplay of the sympathetic and vagal outflows. This interaction can be explored by assessing cardiovascular rhythmicity with appropriate spectral methodologies. Spectral analysis of cardiovascular signal variability, and in particular of RR period (heart rate variability, HRV), is a widely used procedure to investigate autonomic cardiovascular control and\\/or target function

Nicola Montano; Alberto Porta; Chiara Cogliati; Giorgio Costantino; Eleonora Tobaldini; Karina Rabello Casali; Ferdinando Iellamo

2009-01-01

277

The influence of sediment cover variability on longterm river incision rates: An example from the Peikang River,  

E-print Network

The influence of sediment cover variability on longterm river incision rates: An example from reach of the Peikang River. Sediment from these landslides produced widespread aggradation the spatial and temporal variability of sediment cover for the Peikang River. Because the river is undergoing

Mueller, Karl

278

Intra-canopy variability of fruit growth rate in peach trees grafted on rootstocks with different vigour-control capacity  

E-print Network

season and at harvest.At harvest, the fresh weight of each selected fruit was also determined. AfterIntra-canopy variability of fruit growth rate in peach trees grafted on rootstocks with different research was to study intra-canopy variability in fruit growth under conditions of low fruit-to- fruit

DeJong, Theodore

279

The relationships of resting baroreflex sensitivity, heart rate variability and measures of impulse control in children and adolescents  

Microsoft Academic Search

The objectives of the present study were to assess: (1) the feasibility of using a non-invasive method to measure baroreflex sensitivity in children and adolescents; (2) the relationships of resting baroreflex sensitivity with resting levels of other cardiovascular variables; and (3) whether baroreflex sensitivity and heart rate variability, two indices of cardiac vagal control at rest, were related to measures

Michael T. Allen; Karen A. Matthews; Karen L. Kenyon

2000-01-01

280

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

PubMed

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

Wu, Shr-Da; Lo, Pei-Chen

2008-10-01

281

Heart rate variability and its changes over 5 years in older adults  

PubMed Central

Purpose: to characterise the association between age, ageing and heart rate variability (HRV) in older individuals, 585 adults age >65 years with two 24-h Holter recordings in the Cardiovascular Health Study were studied. Methods: heart rate (HR), ventricular premature contractions (VPCs), atrial premature contractions (APCs), frequency-domain, ratio-based and non-linear HRV and heart rate turbulence (HRT) were examined cross-sectionally by 5-year age groups and prospectively over 5 years. Analyses adjusted for gender, lower versus elevated cardiovascular (CV) risk and for the change in CV risk. Results: HR declined, and VPCs and APCs increased per 5-year increase in age. Frequency-domain HRV decreased more at 65–69, less at 70–74 and minimally at ?75 years, independent of CVD risk or change in CVD risk. Ratio and non-linear HRV continued to decline to ?75 years old. Ratio HRV and HRT slope were more strongly related to CVD risk than frequency-domain HRV. Conclusions: cardiac autonomic function, assessed by frequency-domain HRV, declines most at 65–70 and levels off at age >75. The decline is independent of CVD risk or change in CVD risk. Ratio-based and non-linear HRV and HRT slope continued to change with increasing age and were more closely related to CVD risk than frequency-domain HRV. PMID:19147739

Stein, Phyllis K.; Barzilay, Joshua I.; Chaves, Paulo H. M.; Domitrovich, Peter P.; Gottdiener, John S.

2009-01-01

282

Heart rate and heart rate variability in multiparous dairy cows with unassisted calvings in the periparturient period.  

PubMed

Behavioural changes before calving can be monitored on farms; however, predicting the onset of calving is sometimes difficult based only on clinical signs. Heart rate (HR) and heart rate variability (HRV) as non-invasive measures of autonomic nervous system (ANS) activity were investigated in Holstein-Friesian cows (N=20) with unassisted calvings in the periparturient period to predict the onset of calving and assess the stress associated with calving. R-R-intervals were analysed in 5-min time windows during the following three main periods of measurement: 1) between 0 and 96h before the onset of calving restlessness (prepartum period); 2) during four stages of calving: (I) early first stage; between the onset of calving restlessness and the first abdominal contractions; (II) late first stage (between the first abdominal contractions and the appearance of the amniotic sac); (III) early second stage (between the appearance of the amniotic sac and the appearance of the foetal hooves); (IV) late second stage (between the appearance of the foetal hooves and delivery of the calf), and 3) over 48h following calving (postpartum period). Data collected between 72 and 96h before calving restlessness was used as baseline. Besides HR, Poincaré measures [standard deviation 1 (SD1) and 2 (SD2) and SD2/SD1 ratio], the root mean square of successive differences (RMSSD) in R-R intervals, the high-frequency (HF) component of HRV and the ratio between the low-frequency (LF) and the HF components (LF/HF ratio) were calculated. Heart rate increased only following the onset of the behavioural signs, peaked before delivery of the calf, then decreased immediately after calving. Parasympathetic indices of HRV (RMSSD, HFnorm and SD1) decreased, whereas sympathovagal indices (LF/HF ratio and SD2/SD1 ratio) increased significantly from baseline between 12 and 24 before the onset of calving restlessness. The same pattern was observed between 0 and 1h before calving restlessness. Following the onset of behavioural signs, parasympathetic activity increased gradually with a parallel shift in sympathovagal balance towards parasympathetic tone, which was possibly a consequence of oxytocin release, which induces an increase in vagus nerve activity. Parasympathetic activity decreased rapidly between 0 and 0.5h following calving and was lower than measured during all other stages of the study, while sympathetic activity peaked during this stage and was higher than measured during any other stages. Between 0 and 4h after calving vagal tone was lower than baseline, whereas sympathovagal balance was higher, reflecting a prolonged physiological challenge caused by calving. Vagal activity decreased, whereas sympathovagal balance shifted towards sympathetic tone with increased live body weight of the calf during the late second stage of calving, suggesting higher levels of stress associated with the higher body weight of calves. All HRV indices, measured either at the late second stage of calving and between 12 and 24h after calving, were affected by the duration of calving. Our results indicate that ANS activity measured by HRV indices is a more immediate indicator of the onset of calving than behaviour or HR, as it changed earlier than when restlessness or elevation in HR could be observed. However, because of the possible effects of other physiological mechanisms (e.g. oxytocin release) on ANS activity it seems to be difficult to measure stress associated with calving by means of HRV between the onset of calving restlessness and delivery. Further research is needed to enable more precise interpretation of the prepartum changes in HR and HRV in dairy cattle. PMID:25449409

Kovács, L; T?zsér, J; Kézér, F L; Ruff, F; Aubin-Wodala, M; Albert, E; Choukeir, A; Szelényi, Z; Szenci, O

2015-02-01

283

Thermographically determined specific absorption rate patterns of 434-MHz applicators.  

PubMed

The specific absorption rate (SAR) patterns of two 434-MHz hyperthermia applicators, models TCA 434-1 (9 X 20 cm) and TCA 434-2 (13 X 25 cm), were evaluated thermographically using a phantom model. The phantom model consisted of a 2-cm-thick layer of fat and a 10-cm depth of muscle contained in a 30 X 30 cm base Plexiglas box. The model was bisected in the middle. Polyester screens at the interface allowed the synthetic gel to make electrical contact between the two halves of the muscle tissue. Octyl alcohol was applied to the fat interface to ensure continuity of dielectric properties. Thermograms were taken for both applicators over the following areas of the exposed model: (1) fat surface, (2) internal surface with E-field parallel to interface, and (3) internal surface with E-field perpendicular to interface. SAR's were calculated from the temperature rise (8 degrees C maximum), net input power (550-650 W), exposure time (15-60 s), and specific heat of the muscle (0.86 kcal/kg degrees C). A factor of 0.42 needs to be multiplied to correct for the specific heat of fat. High localized SAR's along the broad sides of the applicators were seen when the applicators were in direct contact with the phantom. With the use of a 0.8-cm polystyrene foam spacing, the SAR's within the aperture of the applicators were relatively uniform. The patterns of the two applicators were quite similar. However, the TCA 434-1 applicator is smaller and more applicable for clinical conditions. PMID:3724699

Chou, C K; Guy, A W; McDougall, J A; Dong, A; Luk, K H

1986-01-01

284

A Variable Turbulent Schmidt Number Formulation for Scramjet Application  

NASA Technical Reports Server (NTRS)

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.

Xiao, X.; Edwards, J. R.; Hassan, H. A.; Cutler, A. D.

2004-01-01

285

Pan-Svalbard growth rate variability and environmental regulation in the Arctic bivalve Serripes groenlandicus  

NASA Astrophysics Data System (ADS)

Growth histories contained in the shells of bivalves provide continuous records of environmental and biological information over lifetimes spanning decades to centuries, thereby linking ecosystem responses to both natural and anthropogenic climatic variations over a range of scales. We examined growth rates and temporal growth patterns of 260 individuals of the circumpolar Greenland Smooth Cockle ( Serripes groenlandicus) collected between 1997 and 2009 from 11 sites around the Svalbard Archipelago. These sites encompass a range of oceanographic and environmental conditions, from strongly Atlantic-influenced conditions on the west coast to high-Arctic conditions in northeast Svalbard. Absolute growth was up to three times greater at the most strongly Atlantic-influenced locations compared to the most Arctic-influenced areas, and growth performance was highest at sites closest to the West Spitsbergen Current. We also developed growth chronologies up to 34 years in length extending back to 1974. Standardized growth indices (SGI) exhibited substantial inter-site variability, but there were also common temporal features including steadily increasing growth from the late 1980's to the mid-1990's followed by a marked shift from relatively greater to poorer growth in the mid-1990's and from 2004 to 2008. This pattern was consistent with phase-shifts in large-scale climatic drivers. Interannual variability in SGI was also related to local manifestations of the large-scale drivers, including sea temperature and sea ice extent. The temporal growth pattern at Rijpfjorden, on northeast Svalbard, was broadly representative (R = 0.81) of the entire dataset. While there were site-related differences in the specific relationships between growth and environmental parameters, the aggregated dataset indicated an overriding regional driver of bivalve growth: the Arctic Climate Regime Index (ACRI). These results demonstrate that sclerochronological proxies can be useful retrospective analytical tools for establishing baselines of ecosystem variability and for identifying key ecosystem drivers across spatial and temporal scales.

Carroll, Michael L.; Ambrose, William G.; Levin, Benjamin S.; Locke V, William L.; Henkes, Gregory A.; Hop, Haakon; Renaud, Paul E.

2011-11-01

286

Heart rate variability of human in hypoxic oxygen-argon environment  

NASA Astrophysics Data System (ADS)

Human adaptive capacity, reliability and stability in extreme environments depend primarily on the individual resistance to stresses, includes both innate and acquired components. We have conducted studies in six healthy subjects - men aged between 24 to 42 years who psychophysiological indicators acterizing the severity of stress reactions studied directly during an emergency situation, before and after it. The subjects were in a hypoxic oxygen-argon atmosphere 10 days. Cardiovascular system is one of the first to respond to stressful reaction. The method of heart rate variability (HRV) allows us to estimate balance of sympathetic and parasympathetic parts of vegetative nervous system. In the course of the baseline study it was found that resting heart rate (HR) in the examined individuals is within normal limits. During the experiment in all subjects there was a trend towards more frequent heartbeat. Each subject at one stage or another stay in a hypoxic oxygen-argon environment heart rate go beyond the group norm, but the extent and duration of these abnormalities were significantly different. Marked increase in middle heart rate during of subjects experiment, fluctuating within a wide range (from 2.3% to 29.1%). Marked increase in middle heart rate during of subjects experiment, fluctuating within a wide range (from 2.3% to 29.1%). This suggests that the ability to adapt to living in the investigated gas environment have marked individual differences. SDNN (mean square deviation of all R-R intervals) is the integral indicator of the total effect of the sinus node to the sympathetic and parasympathetic parts of vegetative nervous system, as well as indicating the higher functional reserves of the cardiovascular systems. Increase in heart rate in the majority of subject was accompanied by an increase in individual SDNN. This suggests that the parasympathetic system is able to balance the increase in activity of the sympathetic system, and functional reserves are sufficient. However, the opposite dynamic test 02 - accompanied by a decrease heart rate increase SDNN. The survey detected that all subjects marked signs of increased activity of the sympathetic nervous system. Besides when short-term exposure (up to 10 days) in most researched factor in the majority of patients was enough functional reserves to adapt to the conditions of a changed atmosphere. However, the adaptation process was accompanied by severe stress and compensatory mechanisms for longer stay in hypoxic conditions, oxygen-argon environment may develop adverse effects associated with sympathicotony.

Khayrullina, Rezeda; Smoleevskiy, Alexandr; Bubeev, Yuri

287

Heart Rate Variability Modification after Adult Attachment Interview in Dissociative Patients.  

PubMed

Abstract 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). The Electrocardiogram (EKG) was recorded before, during and after the AAI in thirteen individuals with DD and thirteen healthy participants matched for age and gender. Significant modification of HRV was observed only in the DD group. After the AAI, those with DD showed significant increases of the LF/HF ratio (Pre-AAI: 1.91±1.19; Post-AAI: 4.03±2.40; Wilcoxon-Test = -2.76, p= 0.006). Our results suggest that the retrieval of childhood attachment experiences in individuals with DD is associated with a modification of HRV patterns that could reflect the emotional dysregulation of dissociative psychopathological processes. PMID:25492425

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

2014-12-01

288

Bit-rate variable DPSK demodulation based on cascaded four-wave mixing.  

PubMed

We report a demodulator for DPSK signals at variable bit rates based on cascaded four-wave mixing (FWM). The demodulation utilizes two FWM processes in a photonic crystal fiber (PCF) with in-between dispersion in a chirped fiber Bragg grating (CFBG). The first FWM generates a wavelength-tunable idler carrying phase information of the signal. A tunable optical delay between the signal and the idler is then introduced by dispersion. The signal, the idler, and the pump are reflected by the CFBG with a reflectance of 99% back to the PCF to initiate the second FWM process. In the second FWM, the phase relationship between the signal and the one-bit-delayed idler determines an amplification or attenuation of the idler, converting phase modulation to intensity modulation. Error-free demodulations have been successfully demonstrated for both NRZ and RZ-DPSK signals at 5 and 10 Gb/s. PMID:21369118

Dai, Yongheng; Shu, Chester

2011-02-14

289

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

NASA Technical Reports Server (NTRS)

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.

Paik, W. H.

1981-01-01

290

Heart rate variability in adolescents with functional hypothalamic amenorrhea and anorexia nervosa.  

PubMed

Aim of this study consisted in assessing the 24-h heart rate variability (HRV), a measure of autonomic nervous system (ANS) imbalance, in 21 adolescents with functional hypothalamic amenorrhea (FHA, 11 normogonadotropic, N-FHA, and 10 hypogonadotropic, Hy-FHA) compared to 21 patients with anorexia nervosa (AN) and 21 controls. As expected, subjects with AN showed a significant dysregulation in multiple HRV parameters, while Hy-FHA patients presented with a dysregulation in a few domains (SDNN, HFr), which was not present in girls with N-FHA, who showed values largely similar to controls. FHA might represent part of the AN biological spectrum, and a link between these two conditions might exist, possibly related to the degree of psychological and/or hormonal dysfunction. PMID:24359810

Bomba, Monica; Corbetta, Fabiola; Gambera, Alessandro; Nicosia, Franco; Bonini, Luisa; Neri, Francesca; Tremolizzo, Lucio; Nacinovich, Renata

2014-02-28

291

The effects of exposure to environmental factors on Heart Rate Variability: an ecological perspective.  

PubMed

The impact of human exposure to environmental factors on Heart Rate Variability (HRV) was examined in the urban space of Tel-Aviv-Jaffa. Four environmental factors were investigated: thermal and social loads; CO concentrations and noise. Levels of HRV are explained mainly by subjective social stresses, noise and CO. The most interesting result is the fact that while subjective social stress and noise increase HRV, low levels of CO are reducing HRV to some extent moderating the impact of subjective social stress and noise. Beyond the poisoning effect of CO and the fact that extremely low levels of HRV associated with high dozes of CO increase risk for life, low levels of CO may have a narcotic effect, as it is measured by HRV. The effects of thermal loads on HRV are negligible probably due to the use of behavioral means in order to neutralize heat and cold effects. PMID:23477780

Schnell, Izhak; Potchter, Oded; Epstein, Yoram; Yaakov, Yaron; Hermesh, Hagai; Brenner, Shmuel; Tirosh, Emanuel

2013-12-01

292

[Heart rate variability study based on a novel RdR RR Intervals Scatter Plot].  

PubMed

On the basis of Poincare scatter plot and first order difference scatter plot, a novel heart rate variability (HRV) analysis method based on scatter plots of RR intervals and first order difference of RR intervals (namely, RdR) was proposed. The abscissa of the RdR scatter plot, the x-axis, is RR intervals and the ordinate, y-axis, is the difference between successive RR intervals. The RdR scatter plot includes the information of RR intervals and the difference between successive RR intervals, which captures more HRV information. By RdR scatter plot analysis of some records of MIT-BIH arrhythmias database, we found that the scatter plot of uncoupled premature ventricular contraction (PVC), coupled ventricular bigeminy and ventricular trigeminy PVC had specific graphic characteristics. The RdR scatter plot method has higher detecting performance than the Poincare scatter plot method, and simpler and more intuitive than the first order difference method. PMID:25508411

Lu, Hongwei; Lu, Xiuyun; Wang, Chunfang; Hua, Youyuan; Tian, Jiajia; Liu, Shihai

2014-08-01

293

[Heart rate variability study based on a novel RdR RR Intervals Scatter Plot].  

PubMed

On the basis of Poincare scatter plot and first order difference scatter plot, a novel heart rate variability (HRV) analysis method based on scatter plots of RR intervals and first order difference of RR intervals (namely, RdR) was proposed. The abscissa of the RdR scatter plot, the x-axis, is RR intervals and the ordinate, y-axis, is the difference between successive RR intervals. The RdR scatter plot includes the information of RR intervals and the difference between successive RR intervals, which captures more HRV information. By RdR scatter plot analysis of some records of MIT-BIH arrhythmias database, we found that the scatter plot of uncoupled premature ventricular contraction (PVC), coupled ventricular bigeminy and ventricular trigeminy PVC had specific graphic characteristics. The RdR scatter plot method has higher detecting performance than the Poincare scatter plot method, and simpler and more intuitive than the first order difference method. PMID:25464780

Lu, Hongwei; Lu, Xiuyun; Wang, Chunfang; Hua, Youyuan; Tian, Jiajia; Liu, Shihai

2014-08-01

294

Assessing Complexity of Heart Rate Variability in People with Spinal Cord Injury using Local Scale Exponents  

PubMed Central

Detrended fluctuation analysis (DFA) has been widely used to study dynamics of heart rate variability (HRV), which provides a quantitative parameter, the scaling exponent ?, to represent the correlation properties of RR interval series. However, it has been demonstrated that HRV exhibits complex behavior that cannot be fully described by a single exponent. This study aimed to investigate whether local scale exponent ?(t) with t being the time scale can reveal new features of HRV that cannot be reflected by DFA coefficients. To accurately estimate ?(t), we developed an approach for correcting ?(t) at small scales and verified the approach using simulated signals. We studied HRV in 12 subjects with spinal cord injury and 14 able-bodied controls during sitting and prone postures. The results showed that ?(t) provides complementary views of HRV, suggesting that it may be used to evaluate the effects of SCI-induced autonomic damage on HRV. PMID:25571456

Liao, Fuyuan; Brooks, Ian; Hsieh, Chang-Wei; Rice, Ian M.; Jankowska, Maria M.; Jan, Yih-Kuen

2015-01-01

295

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

E-print Network

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.

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

1998-10-13

296

Resting high-frequency heart rate variability is related to resting brain perfusion.  

PubMed

We examined the neural correlates of resting cardiac vagal activity in a sample of 432 participants (206 male; 61 African American; mean age 42 years). Pulsed arterial spin labeling was used to quantify whole brain and regional cerebral blood flow at rest. High-frequency heart rate variability (HF-HRV) was used to measure cardiac vagal activity at rest. The primary aim was to determine whether brain regions implicated in regulating cardiac vagal reactions were also related to cardiac vagal activity at rest, and whether these associations varied by sex or race. Brain areas previously related to vagal reactivity were related to resting HF-HRV. Directionality of relationships differed between overall and regional flows. Some relationships were only observed in women and African Americans. There appears to be communality between brain regions associated with task-induced vagal reactivity and those associated with resting cardiac vagal activity. PMID:25174686

Allen, Ben; Jennings, J Richard; Gianaros, Peter J; Thayer, Julian F; Manuck, Stephen B

2015-02-01

297

Focusing neurovisceral integration: Cognition, heart rate variability, and cerebral blood flow.  

PubMed

The neurovisceral integration hypothesis suggests in part that cerebral control of autonomic function conveys comparable control of executive function and, hence, correlation among vagally determined high frequency heart rate variability (HF-HRV), executive function, and regional cerebral blood flow (CBF). In 440 middle-aged men and women, resting HF-HRV was related to regional CBF derived from a resting arterial spin-labeled MRI scan and to seven neuropsychological tests of executive function. Despite some intercorrelations, regression modeling failed to support integrated central control of HF-HRV and executive function. Integration between autonomic and cognitive control appears more circumscribed than the general integration suggested by the neurovisceral integration hypothesis. PMID:25160649

Richard Jennings, J; Allen, Ben; Gianaros, Peter J; Thayer, Julian F; Manuck, Stephen B

2015-02-01

298

Use of heart rate variability in monitoring stress and recovery in judo athletes.  

PubMed

The main objective of this study was to examine the effect of different judo training loads on heart rate variability (HRV) measurements, to determine if they can be used as valid indicators in monitoring stress and recovery in judo athletes. Fourteen male national-standard judo athletes were randomly divided into 2 groups, and each group followed a different type of training, namely, a high training load (HTL) and a moderate training load program (MTL). Data collection included HRV measurements, a Recovery Stress Questionnaire for athletes (RESTQ-SPORT), and strength measurements, 4 weeks before and after the training program. The HTL group had lower square root of the mean squared difference of successive RR intervals, very low frequency, high frequency, short-term variability, short-range scaling exponents, general recovery, sport-specific recovery, general stress, maximum strength, maximum power, and higher low/high frequency ratio at posttest compared with pretest (p ? 0.05). The HTL group showed lower short-range and long-range scaling exponents, general recovery, sport-specific recovery, and higher general stress than the MTL group in posttest measurements (p ? 0.05). In conclusion, judo athletes enrolled in an HTL program showed an imbalance of the autonomic nervous system with decreased vagal modulation, together with a decrease in strength parameters, higher markers for stress, and a lower perception of recovery. PMID:24276307

Morales, José; Alamo, Juan M; García-Massó, Xavier; Buscà, Bernat; López, Jose L; Serra-Añó, Pilar; González, Luís-Millán

2014-07-01

299

Lagged Poincar\\'{e} and auto-correlation analysis of Heart rate variability in diabetes  

E-print Network

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.

Ghatak, S K

2010-01-01

300

Scalar dissipation rate modelling in variable density turbulent axisymmetric jets and diffusion flames  

NASA Astrophysics Data System (ADS)

In recent years several transport equation models for the scalar dissipation rate have been proposed to replace the well known algebraic expression based on equality of mechanical and scalar turbulent time scales. In this study various transport equation models are compared with each other and the model equation of Yoshizawa [J. Fluid Mech. 195, 541 (1988)] is given special attention. The latter is shown to allow an algebraic solution that is different from the classical "equal-scales" algebraic model. The constants that appear in this equation are assigned values based on similarity behavior in turbulent jets and based on studies of homogeneous isotropic turbulence. Both algebraic models and the transport equation models are compared and applied to isothermal variable density jets and jet diffusion flames. It is found that general features, such as the behavior of scalar fluctuation intensities of variable density turbulent jets are relatively well predicted by all the models. Differences between the models exist regarding the predicted time scale ratios.

Sanders, J. P. H.; Gökalp, I.

1998-04-01

301

Study of formulation variables influencing the drug release rate from matrix tablets by experimental design.  

PubMed

Experimental design was utilized to simultaneously investigate the effect of varying the type of diluent (insoluble Calcium phosphate or water-soluble arabic gum) and the diluent/matrix ratio on the drug release behaviour from both lipophilic (glyceryl behenate, Compritol) or hydrophilic (hydroxypropylmethylcellulose) matrix tablets. Ketoprofen, theophylline and sodium sulphadiazine were selected as model drugs on the basis of their respectively very low, medium and high water-solubility, in order to evaluate the influence of this parameter as well. The selected response variables were the dissolution efficiency (i.e. the area under the dissolution curve) after one and six hours and the time necessary to dissolve 10% drug. Tablets obtained by direct compression of drug-diluent-matrix ternary mixtures prepared according to the experimental plan provided for by an asymmetric screening matrix, were tested for drug release properties using a USP paddle apparatus. Graphic analysis of the effects allowed identification, for each examined drug, of the formulation factors active on the selected responses and determination of the proper level of the variables to be selected for the response improvement. The different results obtained with the three examined drugs pointed out the role of the drug solubility in determining the influence of formulation parameters on drug release rate from matrix tablets. PMID:16154333

Furlanetto, Sandra; Cirri, Marzia; Maestrelli, Francesca; Corti, Giovanna; Mura, Paola

2006-01-01

302

Haptic feedback enhances rhythmic motor control by reducing variability, not improving convergence rate.  

PubMed

Stability and performance during rhythmic motor behaviors such as locomotion are critical for survival across taxa: falling down would bode well for neither cheetah nor gazelle. Little is known about how haptic feedback, particularly during discrete events such as the heel-strike event during walking, enhances rhythmic behavior. To determine the effect of haptic cues on rhythmic motor performance, we investigated a virtual paddle juggling behavior, analogous to bouncing a table tennis ball on a paddle. Here, we show that a force impulse to the hand at the moment of ball-paddle collision categorically improves performance over visual feedback alone, not by regulating the rate of convergence to steady state (e.g., via higher gain feedback or modifying the steady-state hand motion), but rather by reducing cycle-to-cycle variability. This suggests that the timing and state cues afforded by haptic feedback decrease the nervous system's uncertainty of the state of the ball to enable more accurate control but that the feedback gain itself is unaltered. This decrease in variability leads to a substantial increase in the mean first passage time, a measure of the long-term metastability of a stochastic dynamical system. Rhythmic tasks such as locomotion and juggling involve intermittent contact with the environment (i.e., hybrid transitions), and the timing of such transitions is generally easy to sense via haptic feedback. This timing information may improve metastability, equating to less frequent falls or other failures depending on the task. PMID:24371296

Ankarali, M Mert; Tutkun Sen, H; De, Avik; Okamura, Allison M; Cowan, Noah J

2014-03-01

303

On heart rate variability and autonomic activity in homeostasis and in systemic inflammation.  

PubMed

Analysis of heart rate variability (HRV) is a promising diagnostic technique due to the noninvasive nature of the measurements involved and established correlations with disease severity, particularly in inflammation-linked disorders. However, the complexities underlying the interpretation of HRV complicate understanding the mechanisms that cause variability. Despite this, such interpretations are often found in literature. In this paper we explored mathematical modeling of the relationship between the autonomic nervous system and the heart, incorporating basic mechanisms such as perturbing mean values of oscillating autonomic activities and saturating signal transduction pathways to explore their impacts on HRV. We focused our analysis on human endotoxemia, a well-established, controlled experimental model of systemic inflammation that provokes changes in HRV representative of acute stress. By contrasting modeling results with published experimental data and analyses, we found that even a simple model linking the autonomic nervous system and the heart confound the interpretation of HRV changes in human endotoxemia. Multiple plausible alternative hypotheses, encoded in a model-based framework, equally reconciled experimental results. In total, our work illustrates how conventional assumptions about the relationships between autonomic activity and frequency-domain HRV metrics break down, even in a simple model. This underscores the need for further experimental work towards unraveling the underlying mechanisms of autonomic dysfunction and HRV changes in systemic inflammation. Understanding the extent of information encoded in HRV signals is critical in appropriately analyzing prior and future studies. PMID:24680646

Scheff, Jeremy D; Griffel, Benjamin; Corbett, Siobhan A; Calvano, Steve E; Androulakis, Ioannis P

2014-06-01

304

Slip rate variability along the Kunlun Fault using PS-InSAR  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

305

Integrated Central-Autonomic Multifractal Complexity in the Heart Rate Variability of Healthy Humans  

PubMed Central

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

Lin, D. C.; Sharif, A.

2012-01-01

306

Is slow wave sleep an appropriate recording condition for heart rate variability analysis?  

PubMed

Heart rate variability (HRV) analysis holds increasing interest but electrocardiographic (ECG) recordings are strongly disturbed by body movements, changes in environment and respiration. Here we give arguments for the use of slow wave sleep (SWS) as an appropriate recording condition. Sixteen healthy subjects aged 21-31 years (10 males, 6 females) underwent polygraphic sleep, ECG, and respiratory recordings during one experimental night. HRV was analyzed in 5-min SWS segments and compared to data collected during quiet wake in the morning with controlled breathing, using for each individual the same respiratory frequency as that recorded during SWS. SWS has two major advantages. First, it is a quiet sleep period, free of any external confounding events and is characterized by fewer body movements or arousals that cause abrupt heart rate (HR) increases which disrupt the ECG signal. Second, SWS avoids the deleterious effect of controlled breathing on HRV. Respiratory cycles were spontaneously more regular during SWS than during generally used wake (Standard deviation (SD) of the respiratory cycles was 0.27+/-0.02 s during SWS vs 0.42+/-0.07 s during wake under controlled breathing; p<0.01). Compared to quiet wake, the SD of normal R-R intervals reflecting global variability was significantly lower during SWS (54.3+/-4.7 vs 78.8+/-6.1 ms; p<0.001) and the normalized high frequency power was increased (0.57+/-0.04 vs 0.51+/-0.03; p<0.05), suggesting a higher parasympathetic control of the heart. Thus, SWS offers a "self-controlled" and undisturbed moment of observation for assessing time and frequency domain HRV indexes. Its relevance as an optimal ECG recording condition has to be confirmed in various experimental conditions. PMID:16005265

Brandenberger, Gabrielle; Buchheit, Martin; Ehrhart, Jean; Simon, Chantal; Piquard, François

2005-08-31

307

Hypersonic Boundary Layer Measurements with Variable Blowing Rates Using Molecular Tagging Velocimetry  

NASA Technical Reports Server (NTRS)

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.

Bathel, Brett F.; Danehy, Paul M.; Johansen, Craig T.; Jones, Stephen B.; Goyne, Christopher P.

2012-01-01

308

The association of particulate air metal concentrations with heart rate variability.  

PubMed

Numerous studies show an association between particulate air pollution and adverse health effects. Particulate matter is a complex mixture of elemental carbon, ammonium, sulfates, nitrates, organic components, and metals. The mechanisms of action of particulate matter less than or equal to 2.5 micro m in mean aerodynamic diameter (PM(2.5)), as well as the constituents responsible for the observed cardiopulmonary health effects, have not been identified. In this study we focused on the association between the metallic component of PM(2.5) and cardiac autonomic function based on standard heart rate variability (HRV) measures in an epidemiologic study of boilermakers. Thirty-nine male boilermakers were monitored throughout a work shift. Each subject wore an ambulatory electrocardiogram (Holter) monitor and a personal monitor to measure PM(2.5). We used mixed-effects models to regress heart rate and SDNN index (standard deviation of the normal-to-normal) on PM(2.5) and six metals (vanadium, nickel, chromium, lead, copper, and manganese). There were statistically significant mean increases in the SDNN index of 11.30 msec and 3.98 msec for every 1 micro g/m(3) increase in the lead and vanadium concentrations, respectively, after adjusting for mean heart rate, age, and smoking status. Small changes in mean heart rate were seen with all exposure metrics. The results of this study suggest an association between exposure to airborne metals and significant alterations in cardiac autonomic function. These results extend our understanding of the adverse health effects of the metals component of ambient PM(2.5). PMID:12204821

Magari, Shannon R; Schwartz, Joel; Williams, Paige L; Hauser, Russ; Smith, Thomas J; Christiani, David C

2002-09-01

309

Application of variable-sweep wings to commuter aircraft  

NASA Technical Reports Server (NTRS)

The effects of using variable-sweep wings on the riding quality and mission-performance characteristics of commuter-type aircraft were studied. A fixed-wing baseline vehicle and a variable-sweep version of the baseline were designed and evaluated. Both vehicles were twin-turboprop, pressurized-cabin, 30-passenger commuter aircraft with identical mission requirements. Mission performance was calculated with and without various ride-quality constraints for several combinations of cruise altitude and stage lengths. The variable-sweep aircraft had a gross weight of almost four percent greater than the fixed-wing baseline in order to meet the design-mission requirements. In smooth air, the variable sweep configuration flying with low sweep had a two to three percent fuel-use penalty. However, the imposition of quality constraints in rough air can result in advantages in both fuel economy and flight time for the variable-sweep vehicle flying with high sweep.

Robins, A. W.; Beissner, F. L., Jr.; Lovell, W. A.; Price, J. E.; Turriiziani, R. V.; Washburn, F. F.

1983-01-01

310

Effects of Posteroanterior Thoracic Mobilization on Heart Rate Variability and Pain in Women with Fibromyalgia  

PubMed Central

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

Reis, Michel Silva; Durigan, João Luiz Quagliotti; Arena, Ross; Rossi, Bruno Rafael Orsini; Mendes, Renata Gonçalves; Borghi-Silva, Audrey

2014-01-01

311

Large deviations estimates for the multiscale analysis of heart rate variability  

NASA Astrophysics Data System (ADS)

In the realm of multiscale signal analysis, multifractal analysis provides a natural and rich framework to measure the roughness of a time series. As such, it has drawn special attention of both mathematicians and practitioners, and led them to characterize relevant physiological factors impacting the heart rate variability. Notwithstanding these considerable progresses, multifractal analysis almost exclusively developed around the concept of Legendre singularity spectrum, for which efficient and elaborate estimators exist, but which are structurally blind to subtle features like non-concavity or, to a certain extent, non scaling of the distributions. Large deviations theory allows bypassing these limitations but it is only very recently that performing estimators were proposed to reliably compute the corresponding large deviations singularity spectrum. In this article, we illustrate the relevance of this approach, on both theoretical objects and on human heart rate signals from the Physionet public database. As conjectured, we verify that large deviations principles reveal significant information that otherwise remains hidden with classical approaches, and which can be reminiscent of some physiological characteristics. In particular we quantify the presence/absence of scale invariance of RR signals.

Loiseau, Patrick; Médigue, Claire; Gonçalves, Paulo; Attia, Najmeddine; Seuret, Stéphane; Cottin, François; Chemla, Denis; Sorine, Michel; Barral, Julien

2012-11-01

312

Nonequilibrium quantum criticality in open systems: The dissipation rate as an additional indispensable scaling variable  

NASA Astrophysics Data System (ADS)

We propose that nonequilibrium quantum criticality in open systems under the Born-Markov approximation can be described by a master equation of the Lindblad form. This master equation is derived from a system coupling weakly to a heat bath microscopically and is suggested to provide an approach to study dynamic quantum critical behavior of the system at finite temperatures. We find that the dissipation rate in the equation representing the coupling must be included in the scaling forms as an indispensable additional scaling variable in order to correctly describe the nonequilibrium quantum critical behavior, yet the equilibrium fixed point determines the nonequilibrium critical behavior in the weak coupling limit. Through numerically solving the Lindblad equation for the quantum Ising chain, we affirm these propositions by finite-time scaling forms with the dissipation rate. Nonequilibrium dynamic critical behavior of spontaneous emissions in dissipative open systems at zero temperature near their quantum critical points is discovered and is also described well by the scaling forms.

Yin, Shuai; Mai, Peizhi; Zhong, Fan

2014-03-01

313

Continuously-tunable, bit-rate variable OTDM using broadband SBS slow-light delay line.  

PubMed

We conceptually compare the advantages of the proposed slow-light-based tunable OTDM to conventional fiber-based fixed OTDM multiplexer. We experimentally demonstrate continuously-controllable OTDM of two 2.5-Gb/s return-to-zero (RZ) signals using broadband SBS-based slow-light as the tunable optical delay line. We show that the time slot of one signal path can be manipulated relative to the other by as much as 75-ps. This continuous slow light tunability dramatically enhances the OTDM system performance which results in a power penalty reduction of 9-dB for the multiplexed data stream. We also demonstrate variable-bit-rate OTDM by dynamically adjusting the tunable slow-light delay according to the input bit-rates. We show efficient two-by-one optical time multiplexing of three different input data streams at 2.5-Gb/s, 2.67-Gb/s and 5-Gb/s. PMID:19547161

Zhang, B; Zhang, L; Yan, L-S; Fazal, I; Yang, J-Y; Willner, A E

2007-06-25

314

Seasonal variability in the fertilization rate of women undergoing assisted reproduction treatments.  

PubMed

The objective of this study was to evaluate whether seasonality affects human-assisted reproduction treatment outcomes. For this, 1932 patients undergoing intracytoplasmic sperm injection (ICSI) were assigned to a season group according to the day of oocyte retrieval: winter (n = 435), spring (n = 444), summer (n = 469) or autumn (n = 584). Analysis of variance was used to compare the ICSI outcomes. The fertilization rate was increased during the spring (winter: 67.9%, spring: 73.5%, summer: 68.7% and autumn: 69.0%; p < 0.01). In fact, a nearly 50% increase in the fertilization rate during the spring was observed (odds ratio 1.45, confidence interval 1.20-1.75; p < 0.01). The oestradiol concentration per number of oocytes was significantly higher during the spring (winter: 235.8 pg/mL, spring: 282.1 pg/mL, summer: 226.1 pg/mL and autumn: 228.7 pg/mL; p = 0.030). This study demonstrates a seasonal variability in fertilization after ICSI, where fertilization is higher during the spring than at any other time. PMID:22296507

Braga, Daniela Paes De Almeida Ferreira; Setti, Amanda; Figueira, Rita de Cássia Sávio; Iaconelli, Assumpto; Borges, Edson

2012-07-01

315

Resting Heart Rate Variability Predicts Safety Learning and Fear Extinction in an Interoceptive Fear Conditioning Paradigm  

PubMed Central

This study aimed to investigate whether interindividual differences in autonomic inhibitory control predict safety learning and fear extinction in an interoceptive fear conditioning paradigm. Data from a previously reported study (N?=?40) were extended (N?=?17) and re-analyzed to test whether healthy participants' resting heart rate variability (HRV) - a proxy of cardiac vagal tone - predicts learning performance. The conditioned stimulus (CS) was a slight sensation of breathlessness induced by a flow resistor, the unconditioned stimulus (US) was an aversive short-lasting suffocation experience induced by a complete occlusion of the breathing circuitry. During acquisition, the paired group received 6 paired CS-US presentations; the control group received 6 explicitly unpaired CS-US presentations. In the extinction phase, both groups were exposed to 6 CS-only presentations. Measures included startle blink EMG, skin conductance responses (SCR) and US-expectancy ratings. Resting HRV significantly predicted the startle blink EMG learning curves both during acquisition and extinction. In the unpaired group, higher levels of HRV at rest predicted safety learning to the CS during acquisition. In the paired group, higher levels of HRV were associated with better extinction. Our findings suggest that the strength or integrity of prefrontal inhibitory mechanisms involved in safety- and extinction learning can be indexed by HRV at rest. PMID:25181542

Pappens, Meike; Schroijen, Mathias; Sütterlin, Stefan; Smets, Elyn; Van den Bergh, Omer; Thayer, Julian F.; Van Diest, Ilse

2014-01-01

316

Effects of posteroanterior thoracic mobilization on heart rate variability and pain in women with fibromyalgia.  

PubMed

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

Reis, Michel Silva; Durigan, João Luiz Quagliotti; Arena, Ross; Rossi, Bruno Rafael Orsini; Mendes, Renata Gonçalves; Borghi-Silva, Audrey

2014-01-01

317

Effects of 50 Hz magnetic field exposure on human heart rate variability with passive tilting.  

PubMed

The question of whether power-frequency magnetic fields of strengths relevant to industrial exposure can affect heart rhythm remains controversial. Because the reported effects on heart rate (HR) are so small, procedures which can provoke changes in the sympathovagal balance in a controlled manner may have a greater capacity for identifying subtle field-related changes, if they do exist. We have investigated HR and heart rate variability (HRV) spectral indices in 20 volunteers subjected to a tilt from the supine position to 60 degrees , head up. The tilting procedure was carried out under two conditions, field (28 microT resultant, circularly polarized) and sham, in a balanced double-blind design. Subjects were instructed to breathe in time with an audible cue at 2.5 s intervals. Although the anticipated significant changes in HR and the high frequency (HF), low frequency (LF) and LF/HF ratio (log transformed) occur with tilting, there were no significant differences between corresponding measures with and without exposure to magnetic fields (tilt ln LF/HF ratio 0.94 +/- 0.19 and 0.95 +/- 0.20 for sham and field, respectively). There was also no evidence of a field-related trend in spectral alterations when the time following tilting was divided into three 256 s epochs. PMID:16365512

Sait, Mardi L; Wood, Andrew W; Kirsner, Richard L G

2006-01-01

318

Analysis of heart rate variability during auditory stimulation periods in patients with schizophrenia.  

PubMed

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

Akar, Saime Akdemir; Kara, Sad?k; Latifo?lu, Fatma; Bilgiç, Vedat

2015-02-01

319

Changes in frequency of premature complexes and heart rate variability related to shift work  

PubMed Central

OBJECTIVES—To investigate whether an increased risk of cardiovascular disease might be caused by increased arrhythmogeneity and by unfavourable changes in autonomic cardiac control the changes in the occurrence of premature complexes (PVCs) and in heart rate variability (HRV) were studied in subjects who started to work in shifts.?METHODS—1 Year changes in frequency of PVCs and HRV were measured in 49 shift workers and 22 control subjects working in daytime. All respondents were starting in a new job in integrated circuit or waste incinerator plants.?RESULTS—The incidence of PVC increased significantly in shift workers over the 1 year follow up, compared with daytime workers. The frequency of ventricular extrasystoles increased in 48.9% of the shift workers, and in 27.3% of the daytime workers. The Spearman correlation coefficient between the number of nights worked and the change in PVCs was 0.33 (p=0.004). A small non-significant unfavourable change in HRV was found in both the shift and daytime workers.?CONCLUSIONS—A change in arrhythmogeneity, but not in cardiac autonomic control, might explain the increased risk of cardiovascular disease in shift workers.???Keywords: arrhythmia; heart rate; shift work PMID:11555690

van Amelsvoort, L G P M; Schouten, E; Maan, A; Swenne, C; Kok, F

2001-01-01

320

Heart rate variability and alternans formation in the heart: The role of feedback in cardiac dynamics.  

PubMed

A beat-to-beat alternation in the action potential duration (APD) of myocytes, i.e. alternans, is believed to be a direct precursor of ventricular fibrillation in the whole heart. A common approach for the prediction of alternans is to construct the restitution curve, which is the nonlinear functional relationship between the APD and the preceding diastolic interval (DI). It was proposed that alternans appears when the magnitude of the slope of the restitution curve exceeds one, known as the restitution hypothesis. However, this restitution hypothesis was derived under the assumption of periodic stimulation, when there is a dependence of the DI on the immediate preceding APD (i.e. feedback). However, under physiological conditions, the heart rate exhibits substantial variations in time, known as heart rate variability (HRV), which introduces deviations from periodic stimulation in the system. In this manuscript, we investigated the role of HRV on alternans formation in isolated cardiac myocytes using numerical simulations of an ionic model of the cardiac action potential. We used this model with two different pacing protocols: a periodic pacing protocol with feedback and a protocol without feedback. We show that when HRV is incorporated in the periodic pacing protocol, it facilitated alternans formation in the isolated cell, but did not significantly change the magnitude of alternans. On the other hand, in the case of the pacing protocol without feedback, alternans formation was prevented, even in the presence of HRV. PMID:24576615

McIntyre, Stephen D; Kakade, Virendra; Mori, Yoichiro; Tolkacheva, Elena G

2014-06-01

321

Heart Rate Variability in Response to Pain Stimulus in VLBW Infants Followed Longitudinally During NICU Stay  

PubMed Central

The objective of this longitudinal study, conducted in a neonatal intensive care unit, was to characterize the response to pain of high-risk very low birth weight infants (< 1500 g) from 23 through 38 weeks post-menstrual age (PMA) by measuring heart rate variability (HRV). Heart period data were recorded before, during, and after a heel lanced or wrist venipunctured blood draw for routine clinical evaluation. Pain response to the blood draw procedure and age-related changes of HRV in low-frequency and high-frequency bands were modeled with linear mixed-effects models. HRV in both bands decreased during pain, followed by a recovery to near-baseline levels. Venipuncture and mechanical ventilation were factors that attenuated the HRV response to pain. HRV at the baseline increased with post-menstrual age but the growth rate of high-frequency power was reduced in mechanically ventilated infants. There was some evidence that low-frequency HRV response to pain improved with advancing PMA. PMID:19739134

Padhye, Nikhil S; Williams, Amber L; Khattak, Asif Z; Lasky, Robert E

2009-01-01

322

Aerobic exercise affects T-wave alternans and heart rate variability in postmenopausal women.  

PubMed

The purpose of this study was to investigate the effects of a 10-week high-intermediate exercise intervention on heart rate variability/microscopic T-wave alternans (HRV/MTWA) in healthy postmenopausal women (PMW). 62 healthy PMW were recruited and randomly divided into an exercise group (EG, n=32) or a control group (CG, n=30). The EG attended a progressively high-intermediate intensity (75-85% heart rate reserve, HRR) group-based step aerobic exercise program for 10 weeks, whereas the CG did not receive any intervention. HRV/MTWA, blood chemistry and physical function-related indices were measured before and within 24?h following the 10-week exercise program. Following a 10-week exercise intervention, the EG had significant mean decreases in SDNN (22.4%), CV (21.4%), NN50 (72.6%), LF (ms2; 55.8%), HF (ms2; 39.9%), LF (n.u.; 11.2%), and LF/HF (34.5%). The EG showed a significant increase in HF (n.u.; 40.0%) and CAV (44.4%), whereas there was no significant finding in the CG. The coupling effect of MTWA and HRV after intervention suggests that exercise intervention potentially affects regulation changes of the autonomic nervous system and cardiovascular condition synchronically in PMW. The rebound effect of biomarkers has proven to be a considerable factor on HRV/MTWA measurements. PMID:23757126

Shen, T-W; Wen, H-J

2013-12-01

323

Acute Changes in Heart Rate Variability in Subjects With Diabetes Following a Highway Traffic Exposure  

PubMed Central

Objective To pilot a protocol to evaluate acute cardiovascular effects in in-vehicle exposure to traffic air pollutants in people with diabetes. Methods Twenty-one volunteers with type 2 diabetes were passengers on 90- to 110-minute car rides on a busy highway. We measured in-vehicle particle number and mass (PM2.5) nitrogen dioxide, and carbon monoxide and heart rate, heart rate variability (HRV), and blood pressure. Results Compared with pre-ride measurements, we found a decrease in high frequency (HF) HRV from pre-ride to next day (ratio 0.66, 95% CI = 0.47 to 0.93) and an increase in low frequency to HF ratio at post-ride (ratio 1.92, 95% CI = 1.21 to 3.05) at post-ride. Interquartile range increases in measured pollutants were associated with next-day decreases in HR HRV. Conclusions This protocol appears useful for assessing acute adverse cardiovascular effects of in-vehicle exposures among people who have diabetes. PMID:20190650

Laumbach, Robert J.; Rich, David Q.; Gandhi, Sampada; Amorosa, Louis; Schneider, Stephen; Zhang, Junfeng; Ohman-Strickland, Pamela; Gong, Jicheng; Lelyanov, Oleksiy; Kipen, Howard M.

2014-01-01

324

Reduced heart rate variability during sleep in long-duration spaceflight.  

PubMed

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

Xu, D; Shoemaker, J K; Blaber, A P; Arbeille, P; Fraser, K; Hughson, R L

2013-07-15

325

Analysis of heart rate variability in posttraumatic stress disorder patients in response to a trauma-related reminder  

Microsoft Academic Search

Background: Spectral analysis of heart rate variability has recently been shown to be a reliable noninvasive test for quantitative assessment of cardiovascular autonomic regulatory responses, providing a dynamic map of sympathetic and parasympathetic interaction. In a prior study exploring the state of hyperarousal characterizing the posttraumatic stress disorder (PTSD) syndrome, the authors described standardized heart rate analysis carried out in

Hagit Cohen; Moshe Kotler; Mike A. Matar; Zeev Kaplan; Uri Loewenthal; Hanoch Miodownik; Yair Cassuto

1998-01-01

326

INFLUENCE OF DEMOGRAPHIC, SURGICAL AND IMPLANT VARIABLES ON WEAR RATE AND OSTEOLYSIS IN ABG I HIP ARTHROPLASTY  

Microsoft Academic Search

Periprosthetic osteolysis is associated with accelerated wear rates. The goal of this study was to investigate the influence of demographic and technical variables on wear rates and size of osteolytic lesions. Eighty retrieved ABG I prostheses were analyzed according to prospectively established criteria. There were 22 men and 58 women with an average age of 52 years (34-65) at the

J. Gallo; V. Havranek; I. Cechova; J. Zapletalova

2006-01-01

327

The influence of erosion thresholds and runoff variability on the relationships among topography, climate, and erosion rate  

E-print Network

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

DiBiase, Roman A.

328

Modular high frame rate detector for synchrotron applications  

SciTech Connect

The development of detectors often lags the development in X-ray sources. However, advanced detectors are critical for fully utilizing and exploiting the capabilities of the new bright sources. We report on the development of a modular high frame rate detector for synchrotron applications such as small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). The detector consists of four modules, each providing an imaging area of 5 x 5 cm{sup 2} and capable of frame rates of 200 frames per second (fps) with full resolution, and 650 fps with smaller region of interest (ROI). Details of the detector design and experiments at synchrotron beamlines are discussed in the paper.

Singh, B.; Yang, L.; Thacker, S.; Gaysinskly, V.; Guo, L.; et. al.

2011-01-27

329

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds.  

PubMed

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 (%VO2 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 VO2 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 % VO2 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 % VO2 R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise. PMID:25003546

Cunha, F A; Montenegro, R A; Midgley, A W; Vasconcellos, F; Soares, P P; Farinatti, P

2014-08-01

330

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds  

PubMed Central

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

Cunha, F.A.; Montenegro, R.A.; Midgley, A.W.; Vasconcellos, F.; Soares, P.P.; Farinatti, P.

2014-01-01

331

Variability of stream flow discharge in response to self-similar random fields of temporal fluctuations in lateral inflow rate  

NASA Astrophysics Data System (ADS)

This article presents the use of stochastic methodology for quantitative analysis of variability in stream flow discharge in response to fluctuations in lateral inflow rate, where the lateral inflow rate is considered to be the difference between rainfall and infiltration rates. In this work, we focus on the case where the temporal correlation structure of the fluctuations in the lateral inflow rate can be characterized by the statistics of random fractals. A closed-form expression quantifying the stream flow variability is therefore developed to investigate the influence of the fractal dimension of lateral inflow process and the size of time domain. It is found that the stream flow discharge variability increases with the time domain size, while the fractal dimension of lateral inflow process plays a role in the smoothness of fluctuations in stream flow discharge around the mean.

Chang, Ching-Min; Yeh, Hund-Der

2014-09-01

332

Two Algorithms for Variable Power Control of Heat-Balance Sap Flow Gauges under High Flow Rates  

Microsoft Academic Search

The advantages of variable power control for heat-balance sap flow gauges are evident under high flow rates (e.g., .600 g h21) where high rates of power must be applied. Under the very high flow rates (e.g., 1500-4000 g h21) of mature grapevines (Vitis spp.), we evaluated two algorithms to control the power applied to heat-balance sap flow gauges, and thus

Julie M. Tarara; John C. Ferguson

2006-01-01

333

Personal Exposure to Household Particulate Matter, Household Activities and Heart Rate Variability among Housewives  

PubMed Central

Background The association between indoor air pollution and heart rate variability (HRV) has been well-documented. Little is known about effects of household activities on indoor air quality and HRV alteration. To investigate changes in HRV associated with changes in personal exposure to household particulate matter (PM) and household activities. Methods We performed 24-h continuous monitoring of electrocardiography and measured household PM exposure among 50 housewives. The outcome variables were log10-transformed standard deviation of normal-to-normal (NN) intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent NN intervals (r-MSSD). Household PM was measured as the mass concentration of PM with an aerodynamic diameter <2.5 µm (PM2.5). We used mixed-effects models to examine the association between household PM2.5 exposure and log10-transformed HRV indices. Results After controlling for potential confounders, an interquartile range change in household PM2.5 with 1- to 4-h mean was associated with 1.25–4.31% decreases in SDNN and 0.12–3.71% decreases in r-MSSD. Stir-frying, cleaning with detergent and burning incense may increase household PM2.5 concentrations and modify the effects of household PM2.5 on HRV indices among housewives. Conclusions Indoor PM2.5 exposures were associated with decreased SDNN and r-MSSD among housewives, especially during stir-frying, cleaning with detergent and burning incense. PMID:24594880

Huang, Ya-Li; Chen, Hua-Wei; Han, Bor-Cheng; Liu, Chien-Wei; Chuang, Hsiao-Chi; Lin, Lian-Yu; Chuang, Kai-Jen

2014-01-01

334

Heart rate variability and cardio-respiratory coupling during sleep in patients prior to bariatric surgery.  

PubMed

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

Trimer, R; Cabiddu, R; Mendes, R G; Costa, F S M; Oliveira, A D; Borghi-Silva, A; Bianchi, A M

2014-03-01

335

The Effects of Thoracic Sympathotomy on Heart Rate Variability in Patients with Palmar Hyperhidrosis  

PubMed Central

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

Zhang, Tong-yuan; Xu, Jin-jin

2012-01-01

336

Correlating multidimensional fetal heart rate variability analysis with acid-base balance at birth.  

PubMed

Fetal monitoring during labour currently fails to accurately detect acidemia. We developed a method to assess the multidimensional properties of fetal heart rate variability (fHRV) from trans-abdominal fetal electrocardiogram (fECG) during labour. We aimed to assess this novel bioinformatics approach for correlation between fHRV and neonatal pH or base excess (BE) at birth.We enrolled a prospective pilot cohort of uncomplicated singleton pregnancies at 38-42?weeks' gestation in Milan, Italy, and Liverpool, UK. Fetal monitoring was performed by standard cardiotocography. Simultaneously, with fECG (high sampling frequency) was recorded. To ensure clinician blinding, fECG information was not displayed. Data from the last 60?min preceding onset of second-stage labour were analyzed using clinically validated continuous individualized multiorgan variability analysis (CIMVA) software in 5?min overlapping windows. CIMVA allows simultaneous calculation of 101 fHRV measures across five fHRV signal analysis domains. We validated our mathematical prediction model internally with 80:20 cross-validation split, comparing results to cord pH and BE at birth.The cohort consisted of 60 women with neonatal pH values at birth ranging from 7.44 to 6.99 and BE from -0.3 to -18.7?mmol?L(-1). Our model predicted pH from 30 fHRV measures (R(2) = 0.90, P < 0.001) and BE from 21 fHRV measures (R(2) = 0.77, P < 0.001).Novel bioinformatics approach (CIMVA) applied to fHRV derived from trans-abdominal fECG during labor correlated well with acid-base balance at birth. Further refinement and validation in larger cohorts are needed. These new measurements of fHRV might offer a new opportunity to predict fetal acid-base balance at birth. PMID:25407948

Frasch, Martin G; Xu, Yawen; Stampalija, Tamara; Durosier, Lucien D; Herry, Christophe; Wang, Xiaogang; Casati, Daniela; Seely, Andrew Je; Alfirevic, Zarko; Gao, Xin; Ferrazzi, Enrico

2014-12-01

337

Selection of entropy-measure parameters for knowledge discovery in heart rate variability data  

PubMed Central

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

2014-01-01

338

Racial differences in heart rate variability during sleep in women: The SWAN Sleep Study  

PubMed Central

Background Heart rate variability (HRV) differs markedly by race, yet few studies have evaluated these relationships in women. Moreover, none have evaluated HRV during sleep, despite sleep's importance to cardiovascular health. Methods We addressed these gaps by examining HRV during sleep in African American, Chinese and white women (mean age 51.2 ± 2.2). Sleep and HRV during sleep (sHRV) were measured concurrently. Results Heart rate variability during stage 2 non-rapid eye movement (NREM) and rapid eye movement (REM) sleep differed significantly by race after adjusting for possible confounders. Normalized high frequency HRV was significantly lower in white compared to African American and Chinese participants (white NREM=0.35 ±.01, REM=0.23 ± .01; African American NREM=0.43 ± 0.02, REM=0.29 ± 0.02; Chinese NREM=0.47 ± 0.03, REM=0.33 ± 0.02; p’s<.001). The inverse was seen for low frequency power, with higher values in white compared to African American and Chinese participants (white NREM=0.66 ± .01, REM=0.77 ± .01; African American=NREM 0.58 ± 0.02, REM=0.71 ± 0.02; Chinese=0.53 ± 0.03, REM=0.68 ± 0.02; p’s<.010). Whites also exhibited higher low-to-high frequency HRV ratios during sleep compared to African American and Chinese women (white NREM=2.42 ± 1.07, REM=5.05 ± 1.07; African American NREM=1.69 ± 1.09, REM=3.51 ± 1.09; Chinese NREM=.35 ± 1.07, REM=2.88 ± 1.13; p’s<.001). Conclusions Race was robustly related to HRV during sleep. Compared to African American and Chinese women, whites exhibited decreased vagally-mediated control of the heart during sleep. Rresearch is needed to evaluate whether sHRV, including race differences, is prospectively associated with cardiovascular disease. PMID:24077772

Hall, Martica; Middleton, Kellie; Thayer, Julian F; Lewis, Tené T.; Kline, Christopher E.; Matthews, Karen A.; Kravitz, Howard M.; Krafty, Robert T.; Buysse, Daniel J.

2013-01-01

339

The 5-HTTLPR genotype modulates heart rate variability and its adjustment by pharmacological panic challenge in healthy men.  

PubMed

Abnormal serotonin transporter (5-HTT) function and autonomic nervous system (ANS) dysregulation has been proposed in panic disorder. However, in contrast to hypothalamo-pituitary-adrenocortical (HPA) functioning, ANS reactivity during panic response has yet not been investigated in humans with respect to the 5-HTT genotype. The present study assessed the influence of challenging by cholecystokinin tetrapeptide (CCK-4) on heart rate variability (HRV) measures, to monitor autonomic reactivity and its relationship to 5-HTT-linked polymorphic region (5-HTTLPR) genotypes. We hypothesized substantial effects of the 5-HTTLPR genotype on autonomic reactivity. We studied 30 healthy young men, 15 of each with the long/long (l/l) or short/short (s/s) genotype for the 5-HTTLPR. All participants received an intravenous application of 50 ?g CCK-4. HRV measures were assessed in both groups at baseline and immediately after CCK-4 application. Our results indicated lower parasympathetic activity in s/s carriers during baseline, time and frequency domain measures. CCK-4 application significantly enhanced the sympathetic tone in both groups, leading to diminished group differences. A significant treatment by genotype effect indicated reduced autonomic reactivity to CCK-4 challenge in the s/s compared to l/l carriers. Our findings show enhanced sympathetic and/or diminished cardiac vagal activity under basal conditions and blunted autonomic reactivity in s/s vs. l/l carriers. Our study provides novel data supporting claims that the s/s genotype represents a genetic vulnerability factor associated with inadequate hyporeactivity to stress and extends current knowledge on the impact of the central serotonergic activity on the sympathoadrenal pathway. PMID:24342768

Agorastos, Agorastos; Kellner, Michael; Stiedl, Oliver; Muhtz, Christoph; Becktepe, Jos S; Wiedemann, Klaus; Demiralay, Cüneyt

2014-03-01

340

Changes in deceleration capacity of heart rate and heart rate variability induced by ambient air pollution in individuals with coronary artery disease  

Microsoft Academic Search

BACKGROUND AND OBJECTIVE: Exposure to ambient particles has been shown to be responsible for cardiovascular effects, especially in elderly with cardiovascular disease. The study assessed the association between deceleration capacity (DC) as well as heart rate variability (HRV) and ambient particulate matter (PM) in patients with coronary artery disease (CAD). METHODS: A prospective study with up to 12 repeated measurements

Alexandra Schneider; Regina Hampel; Angela Ibald-Mulli; Wojciech Zareba; Georg Schmidt; Raphael Schneider; Regina Rückerl; Jean Philippe Couderc; Betty Mykins; Günter Oberdörster; Gabriele Wölke; Mike Pitz; H-Erich Wichmann; Annette Peters

2010-01-01

341

ACTIVE LEARNING TO OVERCOME SAMPLE SELECTION BIAS: APPLICATION TO PHOTOMETRIC VARIABLE STAR CLASSIFICATION  

SciTech Connect

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.

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

342

Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star Classification  

NASA Astrophysics Data System (ADS)

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.

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

343

Kangaroo Care Modifies Preterm Infant Heart Rate Variability in Response to Heel Stick Pain: Pilot Study  

PubMed Central

Background Heel stick is the most common painful procedure for preterm infants in neonatal intensive care units. Resultant pain causes adverse physiological effects in major organ systems. Kangaroo Care (KC), involving mother-infant skin-to-skin contact is a promising analgesic for infant pain; however, the effect of KC on the autonomic nervous system's response to pain is unknown. Aim To determine if KC results in improved balance in autonomic responses to heel stick pain than the standard method where infants remain in an incubator care (IC) for the heel stick. Study Design A randomized cross-over trial. Subjects Fourteen preterm infants, 30-32 weeks gestational age and less than 9 days postnatal age. Outcome Measures Infant behavioral state, heart rate, heart rate variability (HRV) indices including low frequency (LF) and high frequency (HF) power, and the LF/HF ratio measured over Baseline, Heel Warming, Heel Stick, and Recovery periods in KC and IC conditions. Results HRV differences between KC and IC were that LF was higher in KC at Baseline (p<.01) and at Heel Stick (p< .001), and HF was higher in KC at Baseline than in the IC condition (p< .05). The LF/HF ratio had less fluctuation across the periods in KC than in IC condition and was significantly lower during Recovery in KC than in IC (p< .001). Conclusions Infants experienced better balance in response in KC than IC condition as shown by more autonomic stability during heel stick. KC may be helpful in mediating physiologic response to painful procedures in preterm infants. PMID:19505775

Cong, Xiaomei; Ludington-Hoe, Susan M.; McCain, Gail; Fu, Pingfu

2009-01-01

344

Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring.  

PubMed

The measurement of heart rate variability (HRV) is often considered a convenient non-invasive assessment tool for monitoring individual adaptation to training. Decreases and increases in vagal-derived indices of HRV have been suggested to indicate negative and positive adaptations, respectively, to endurance training regimens. However, much of the research in this area has involved recreational and well-trained athletes, with the small number of studies conducted in elite athletes revealing equivocal outcomes. For example, in elite athletes, studies have revealed both increases and decreases in HRV to be associated with negative adaptation. Additionally, signs of positive adaptation, such as increases in cardiorespiratory fitness, have been observed with atypical concomitant decreases in HRV. As such, practical ways by which HRV can be used to monitor training status in elites are yet to be established. This article addresses the current literature that has assessed changes in HRV in response to training loads and the likely positive and negative adaptations shown. We reveal limitations with respect to how the measurement of HRV has been interpreted to assess positive and negative adaptation to endurance training regimens and subsequent physical performance. We offer solutions to some of the methodological issues associated with using HRV as a day-to-day monitoring tool. These include the use of appropriate averaging techniques, and the use of specific HRV indices to overcome the issue of HRV saturation in elite athletes (i.e., reductions in HRV despite decreases in resting heart rate). Finally, we provide examples in Olympic and World Champion athletes showing how these indices can be practically applied to assess training status and readiness to perform in the period leading up to a pinnacle event. The paper reveals how longitudinal HRV monitoring in elites is required to understand their unique individual HRV fingerprint. For the first time, we demonstrate how increases and decreases in HRV relate to changes in fitness and freshness, respectively, in elite athletes. PMID:23852425

Plews, Daniel J; Laursen, Paul B; Stanley, Jamie; Kilding, Andrew E; Buchheit, Martin

2013-09-01

345

Influence of postexercise cooling techniques on heart rate variability in men.  

PubMed

The reduction of core body temperature (T(C)) is vitally important in the treatment of hyperthermia; however, little is known regarding the impact of cooling treatments on the autonomic control of heart rate (HR). The aim of the present study was to examine the influence of three field-based hyperthermia treatments on the neural control of HR via heart rate variability (HRV). Following exercise-induced hyperthermia (T(C) approximately 40.0 degrees C) in a warm environment (34.2 +/- 0.5 degrees C), nine healthy, active men were treated during recovery, in a randomized order, with intravenous cold saline infusion (IV) or ice packs (ICE) or fan cooling with intermittent water spray (FAN) for 40 min. During each treatment, HR dynamics via power spectral (VLF, LF, HF), Poincare plot (SD1, SD2), approximate entropy (ApEn) and short- (alpha(1)) and long-term (alpha(2)) fractal scaling analyses were determined every 10 min. At recovery onset, HR and T(C) were similar between treatments and were significantly reduced over the 40 min recovery period. During recovery, HR and alpha(2) were significantly reduced from initial levels but were significantly greater for IV compared with ICE and FAN. In contrast, VLF, LF, HF, SD1, SD2 and ApEn increased during recovery, with all being significantly lower for IV compared with ICE and/or FAN. The present results demonstrated that IV, compared with ICE and FAN, resulted in significantly greater HR, reduced spectral and geometrical HRV, lower HR complexity and reduced long-term HR control, indicative of reduced vagal and/or increased sympathetic modulation. Specific treatments for exercise-induced hyperthermia may result in an altered sympathovagal balance that requires further examination. PMID:19270035

Leicht, Anthony S; Sinclair, Wade H; Patterson, Mark J; Rudzki, Stephan; Tulppo, Mikko P; Fogarty, Alison L; Winter, Sue

2009-06-01

346

Respiratory safety pharmacology: Concurrent validation of volume, rate, time, flow and ratio variables in conscious male Sprague–Dawley rats  

Microsoft Academic Search

This study compares basic respiratory variables (rate, tidal and minute volumes) with time-, flow- and ratio-derived parameters obtained using head-out plethysmography in rats following administration of reference drugs (isotonic saline, 2.0mL\\/kg, IV; albuterol, 400?g\\/kg, inhalation; methacholine, 136?g\\/kg, IV; and remifentanil, 14?g\\/kg, IV) to identify respiratory variables with superior sensitivity. Paired t-tests by block-period, and analysis of covariance (ANCOVA) with baseline

Margarita Legaspi; Simon Authier; Dominique Gauvin; Maxim Moreau; Guy Beauchamp; Fernando Chaurand; Eric Troncy

2010-01-01

347

Dynamic Modeling of the SSDI Application Timing Decision: The Importance of Policy Variables  

Microsoft Academic Search

This paper analyzes the importance of policy variables in the context of Social Security Disability Insurance (SSDI) application timing decision. Previously, we explicitly modeled the optimal timing of SSDI application using dynamic structural models. We estimated these models using data from the Health and Retirement Study (HRS). This paper uses option value model estimates to simulate application timing under alternative

Richard V. Burkhauser; J. S. Butler; Gulcin Gumus

2003-01-01

348

Field validity of heart rate variability metrics produced by QRSTool and CMetX.  

PubMed

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, user-friendly tools that can be used to compute metrics of HRV. In the present study, the authors examined the field validity of these software tools--that is, their validity when used by nonexperts. In a lab with extensive expertise in psychopathology but not psychophysiology, ECG data were obtained from 63 undergraduates at baseline and during a stressor and then processed using QRSTool and CMetX to produce the 10 HRV indices described in Allen et al. (2007). The indices displayed factor structures and patterns of changes from baseline to stressor that were similar to findings from Allen et al. and consistent with how indices of parasympathetic and sympathetic activity should behave. Results support the field validity of QRSTool and CMetX, suggesting that they are useful for nonexperts in psychophysiology interested in measuring HRV. PMID:22329530

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

2012-09-01

349

On the risk of aortic valve replacement surgery assessed by heart rate variability parameters.  

PubMed

In recent years the number of arterial stenosis (AS) patients has grown rapidly and valvular disease is expected to be the next great epidemic. We studied a group of 385 arterial valve replacement (AVR) surgery patients, of whom 16 had died in the postoperational period (up to 30?d after the operation). Each patient had a heart rate variability (HRV) recording made prior to the operation in addition to a full set of medical diagnostics including echocardiography. We formed 16 age, sex, New York Heart Association (NYHA) class, and BMI adjusted control pairs for each person who died in the perioperative period. Our aim was to find indications of the risk from AVR surgery based on the medical data and HRV properties. Besides standard, linear HRV methods, we used indexes of time irreversibility introduced by Guzik (G%), Porta (P%), Ehlers (index E) and Hou (index D). In addition, we analyzed the multiscale multifractal properties of HRV calculating the Hurst surface. The nonlinear analysis methods show statistically significant indications of the risk of AVR surgery in an increase of multifractality and an increase of time irreversibility of the HRV measured prior to the operation. PMID:25514504

Zebrowski, J J; Kowalik, I; Or?owska-Baranowska, E; Andrzejewska, M; Baranowski, R; Giera?towski, J

2015-01-01

350

Effect of acute hypoxia on heart rate variability at rest and during exercise.  

PubMed

The purpose of this study was to investigate sympathovagal balance as inferred from heart rate variability (HRV) responses to acute hypoxia at rest and during exercise. HRV was evaluated in 12 healthy subjects during a standardized hypoxic tolerance test which consists of four periods alternating rest and moderate exercise (50 % V.O (2)max) in normoxic and hypoxic conditions. Ventilatory responses were determined and HRV indexes were calculated for the last 5 min of each period. In well-tolerant subjects, hypoxia at rest induced a decrease of root-mean-square of successive normal R-R interval differences (RMSSD) (p < 0.05) and of absolute high frequency (HF) power (p < 0.001). All absolute HRV indexes were strongly reduced during exercise (p < 0.001) with no further changes under the additional stimulus of hypoxia. A significant increase (p < 0.05) in the HF/(LF+HF) ratio (where LF is low frequency power) was found during exercise in hypoxia compared to exercise in normoxia, associated with similar mean changes in ventilation and tidal volume. These results indicate a vagal control withdrawal under hypoxia at rest. During exercise at 50 % V.O (2)max, HRV indexes cannot adequately represent cardiac autonomic adaptation to acute hypoxia, or possibly to other additional stimuli, due to the dominant effect of exercise and the eventual influence of confounding factors. PMID:15162245

Buchheit, M; Richard, R; Doutreleau, S; Lonsdorfer-Wolf, E; Brandenberger, G; Simon, C

2004-05-01

351

Cardiac Uncoupling and Heart Rate Variability Stratify ICU Patients by Mortality  

PubMed Central

Objective: We have previously shown that cardiac uncoupling (reduced heart rate variability) in the first 24 hours of trauma ICU stay is a robust predictor of mortality. We hypothesize that cardiac uncoupling over the entire ICU stay independently predicts mortality, reveals patterns of injury, and heralds complications. Methods: A total of 2088 trauma ICU patients satisfied the inclusion criteria for this study. Cardiac uncoupling by outcome was compared using the Wilcoxon rank sum test. Risk of death from cardiac uncoupling and covariates (age, ISS, AIS Head Score, total transfusion requirements) was assessed using multivariate logistic regression models at each ICU day. Univariate logistic regression was used to assess risk of death from uncoupling irrespective of covariates at each ICU day. Results: A total of 1325 (63.5%) patients displayed some degree of uncoupling over their ICU stay. The difference in uncoupling between survivors and nonsurvivors is both dramatic and consistent across the entire ICU stay, indicating that the presence of uncoupling is unrelated to the cause of death. However, the magnitude of uncoupling varies by day when data is stratified by cause of death. Conclusions: Cardiac uncoupling: 1) is an independent predictor of death throughout the ICU stay, 2) has a predictive window of 2 to 4 days, and 3) appears to increase in response to inflammation, infection, and multiple organ failure. PMID:16772784

Norris, Patrick R.; Ozdas, Asli; Cao, Hanqing; Williams, Anna E.; Harrell, Frank E.; Jenkins, Judith M.; Morris, John A.

2006-01-01

352

Using near infrared spectroscopy and heart rate variability to detect mental overload.  

PubMed

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

Durantin, G; Gagnon, J-F; Tremblay, S; Dehais, F

2014-02-01

353

A Body Shape Index and Heart Rate Variability in Healthy Indians with Low Body Mass Index  

PubMed Central

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

Thomas, Tinku; Bharathi, Ankalmadagu Venkatsubbareddy; Sucharita, Sambashivaiah

2014-01-01

354

Heart rate variability and treatment outcome in major depression: a pilot study.  

PubMed

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

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

355

A body shape index and heart rate variability in healthy indians with low body mass index.  

PubMed

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/m(2)) and to compare with normal BMI group (BMI 18.5 to 24.9?kg/m(2)). 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

Sowmya, Sharma; Thomas, Tinku; Bharathi, Ankalmadagu Venkatsubbareddy; Sucharita, Sambashivaiah

2014-01-01

356

Cardiac arrhythmia detection using combination of heart rate variability analyses and PUCK analysis.  

PubMed

This paper presents cardiac arrhythmia detection using the combination of a heart rate variability (HRV) analysis and a "potential of unbalanced complex kinetics" (PUCK) analysis. Detection performance was improved by adding features extracted from the PUCK analysis. Initially, R-R interval data were extracted from the original electrocardiogram (ECG) recordings and were cut into small segments and marked as either normal or arrhythmia. HRV analyses then were conducted using the segmented R-R interval data, including a time-domain analysis, frequency-domain analysis, and nonlinear analysis. In addition to the HRV analysis, PUCK analysis, which has been implemented successfully in a foreign exchange market series to characterize change, was employed. A decision-tree algorithm was applied to all of the obtained features for classification. The proposed method was tested using the MIT-BIH arrhythmia database and had an overall classification accuracy of 91.73%. After combining features obtained from the PUCK analysis, the overall accuracy increased to 92.91%. Therefore, we suggest that the use of a PUCK analysis in conjunction with HRV analysis might improve performance accuracy for the detection of cardiac arrhythmia. PMID:24110032

Mahananto, Faizal; Igasaki, Tomohiko; Murayama, Nobuki

2013-01-01

357

Effects of acute hypoxia on heart rate variability, sample entropy and cardiorespiratory phase synchronization  

PubMed Central

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?

2014-01-01

358

Robust efficiency and actuator saturation explain healthy heart rate control and variability  

PubMed Central

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

Li, Na; Cruz, Jerry; Chien, Chenghao Simon; Sojoudi, Somayeh; Recht, Benjamin; Stone, David; Csete, Marie; Bahmiller, Daniel; Doyle, John C.

2014-01-01

359

Multiscale analysis of heart rate variability in non-stationary environments  

PubMed Central

Heart rate variability (HRV) is highly non-stationary, even if no perturbing influences can be identified during the recording of the data. The non-stationarity becomes more profound when HRV data are measured in intrinsically non-stationary environments, such as social stress. In general, HRV data measured in such situations are more difficult to analyze than those measured in constant environments. In this paper, we analyze HRV data measured during a social stress test using two multiscale approaches, the adaptive fractal analysis (AFA) and scale-dependent Lyapunov exponent (SDLE), for the purpose of uncovering differences in HRV between chronic fatigue syndrome (CFS) patients and their matched-controls. CFS is a debilitating, heterogeneous illness with no known biomarker. HRV has shown some promise recently as a non-invasive measure of subtle physiological disturbances and trauma that are otherwise difficult to assess. If the HRV in persons with CFS are significantly different from their healthy controls, then certain cardiac irregularities may constitute good candidate biomarkers for CFS. Our multiscale analyses show that there are notable differences in HRV between CFS and their matched controls before a social stress test, but these differences seem to diminish during the test. These analyses illustrate that the two employed multiscale approaches could be useful for the analysis of HRV measured in various environments, both stationary and non-stationary. PMID:23755016

Gao, Jianbo; Gurbaxani, Brian M.; Hu, Jing; Heilman, Keri J.; Emanuele II, Vincent A.; Lewis, Greg F.; Davila, Maria; Unger, Elizabeth R.; Lin, Jin-Mann S.

2013-01-01

360

Noninvasive method for electrocardiogram recording in conscious rats: feasibility for heart rate variability analysis.  

PubMed

Heart rate variability (HRV) analysis consists in a well-established tool for the assessment of cardiac autonomic control, both in humans and in animal models. Conventional methods for HRV analysis in rats rely on conscious state electrocardiogram (ECG) recording based on prior invasive surgical procedures for electrodes/transmitters implants. The aim of the present study was to test a noninvasive and inexpensive method for ECG recording in conscious rats, assessing its feasibility for HRV analysis. A custom-made elastic cotton jacket was developed to fit the rat's mean thoracic circumference, with two pieces of platinum electrodes attached on its inner surface, allowing ECG to be recorded noninvasively in conscious, restrained rats (n=6). Time- and frequency-domain HRV analyses were conducted, under basal and autonomic blockade conditions. High-quality ECG signals were obtained, being feasible for HRV analysis. As expected, mean RR interval was significantly decreased in the presence of atropine (p <0.05) and increased in the presence of propranolol (p<0.001). Also, reinforcing the reliability of the method, low- and high-frequency HRV spectral powers were significantly decreased in the presence of propranolol (p <0.05) and atropine (p< 0.001), respectively. In summary, the present work describes a novel, inexpensive and noninvasive method for surface ECG recording in conscious rats. PMID:20563424

Pereira-Junior, Pedro P; Marocolo, Moacir; Rodrigues, Fabricio P; Medei, Emiliano; Nascimento, José H M

2010-06-01

361

Anxiety Disorders are Associated with Reduced Heart Rate Variability: A Meta-Analysis  

PubMed Central

Background: Anxiety disorders increase risk of future cardiovascular disease (CVD) and mortality, even after controlling for confounds including smoking, lifestyle, and socioeconomic status, and irrespective of a history of medical disorders. While impaired vagal function, indicated by reductions in heart rate variability (HRV), may be one mechanism linking anxiety disorders to CVD, prior studies have reported inconsistent findings highlighting the need for meta-analysis. Method: Studies comparing resting-state HRV recordings in patients with an anxiety disorder as a primary diagnosis and healthy controls were considered for meta-analysis. Results: Meta-analyses were based on 36 articles, including 2086 patients with an anxiety disorder and 2294 controls. Overall, anxiety disorders were characterized by lower HRV [high frequency (HF): Hedges’ g?=??0.29. 95% CI: ?0.41 to ?0.17, p?

Chalmers, John A.; Quintana, Daniel S.; Abbott, Maree J.-Anne; Kemp, Andrew H.

2014-01-01

362

Association between heart rate variability and fluctuations in resting-state functional connectivity  

PubMed Central

Functional connectivity has been observed to fluctuate across the course of a resting state scan, though the origins and functional relevance of this phenomenon remain to be shown. The present study explores the link between endogenous dynamics of functional connectivity and autonomic state in an eyes-closed resting condition. Using a sliding window analysis on resting state fMRI data from 35 young, healthy male subjects, we examined how heart rate variability (HRV) covaries with temporal changes in whole-brain functional connectivity with seed regions previously described to mediate effects of vigilance and arousal (amygdala and dorsal anterior cingulate cortex; dACC). We identified a set of regions, including brainstem, thalamus, putamen, and dorsolateral prefrontal cortex, that became more strongly coupled with the dACC and amygdala seeds during states of elevated HRV. Effects differed between high and low frequency components of HRV, suggesting specific contributions of parasympathetic and sympathetic tone on individual connections. Furthermore, dynamics of functional connectivity could be separated from those primarily related to BOLD signal fluctuations. The present results contribute novel information about the neural basis of transient changes of autonomic nervous system states, and suggest physiological and psychological components of the recently observed non-stationarity in resting state functional connectivity. PMID:23246859

Chang, Catie; Metzger, Coraline D.; Glover, Gary H.; Duyn, Jeff H.; Heinze, Hans-Jochen; Walter, Martin

2012-01-01

363

Association between Cigarette Smoking and Erectile Tumescence: The Mediating Role of Heart Rate Variability  

PubMed Central

Cigarette smoking deleteriously affects erectile function, and conversely, quitting smoking improves erectile hemodynamics. Underlying mechanisms by which smoking (or reduction of smoking frequency) may affect erectile physiology are not well understood. This study examined the mediating role of heart rate variability (HRV; a marker of sympathovagal balance) among a sample of male chronic smokers from the United States. Sixty-two healthy men (Mage = 38.27 years; SD = 10.62) were assessed at baseline (while smoking regularly), at mid-treatment (while using a nicotine patch), and at follow-up, four weeks after patch discontinuation. Cigarette use, frequency-domain parameters of HRV (low frequency [LF], high frequency [HF], LF/HF ratio), and physiological sexual arousal responses (via penile plethysmography) were assessed at each visit. Results were consistent with mediation, in that greater reductions in cigarette use from baseline to follow-up were associated with longitudinal increases in LF, which in turn showed positive relations with across-time changes in erectile tumescence. Neither HF or LF/HF ratio mediated the relationship between smoking and erection. In conclusion, HRV mediated the inverse relationship between reductions in smoking and enhancements in erectile tumescence. Results underscore the possibility that cigarette use may deleteriously affect erectile function peripherally, in part, by disrupting cardiac autonomic function. PMID:23303335

Harte, Christopher B.; Meston, Cindy M.

2012-01-01

364

Comparison of quantitative sensory testing and heart rate variability in Swedish Val30Met ATTR.  

PubMed

Patients with transthyretin amyloidosis (ATTR) polyneuropathy, a hereditary fatal disease, often report defects in both thermal perception and autonomic nervous system function as their first clinical symptoms. While elevated thermal perception thresholds (TPT) for cold and warmth only recently have been shown as an early marker of small nerve fiber dysfunction in these patients, heart rate variability (HRV) has frequently been used to quantify autonomic neuropathy. The main purpose with this report was to elucidate a possible relationship between estimates of HRV and TPT in a selected group of early and late-onset Swedish Val30Met ATTR patients. The results show significantly more pronounced elevation of TPT in early compared to late-onset patients. Significant correlations between HRV and TPT were found among late-onset cases, indicating a possible relationship between loss of thin nerve fibers in somatic and autonomic nerves, while generally no such relationships were found among early-onset cases. This observation emphasizes the importance of testing both HRV and TPT to ensure optimal early detection of neuropathic changes in an as wide as possible range of small nerve fibers in suspected ATTR patients. This is of particular importance as the phenotype of the ATTR disease varies between groups with different age of onset. PMID:22035563

Heldestad, Victoria; Wiklund, Urban; Hörnsten, Rolf; Obayashi, Konen; Suhr, Ole B; Nordh, Erik

2011-12-01

365

Low heart rate variability in unemployed men: The possible mediating effects of life satisfaction.  

PubMed

Unemployment has consistently been associated with increased risk of cardiovascular disease and premature mortality, and impaired autonomic modulation of the heart might be one mechanism partly explaining this. This study examined whether the possible effect of unemployment on cardiac autonomic modulation is in part mediated by lower psychological well-being. The sample comprised of 15 job-seeking men aged 30-49 years matched with 15 employed men on age, type of job, smoking habits, alcohol intake, frequency of physical activity, and body mass index. Heart rate variability (HRV) during a modified orthostatic test was the measure of cardiac autonomic modulation, and life satisfaction was the measure of psychological well-being. Unemployed men had significantly lower overall HRV (p = .040) than controls. This association was partially mediated through lower general life satisfaction, and in particular, by low financial satisfaction, independently of demographic and/or behavioral factors that influence HRV. These findings suggest that seeking a job is a potential stressor that may reduce overall HRV and contribute towards disturbance of cardiac autonomic modulation in men. Financial difficulties could be one mechanism through which the effects of unemployment are translated into impaired autonomic modulation. PMID:25482493

Jandackova, V K; Jackowska, M

2014-12-01

366

Individual differences in resting heart rate variability and cognitive control in posttraumatic stress disorder  

PubMed Central

Post-traumatic stress disorder (PTSD) is characterized by deficits in cognitive functioning, particularly cognitive control. Moreover, these deficits are thought to play a critical role in the etiology and maintenance of core PTSD symptoms such as intrusive thoughts and memories. However, the psychophysiological concomitants of cognitive control remain largely unexamined. In this article, we suggest that individual differences in heart rate variability (HRV), a physiological index of self-regulatory capacity, may underlie the association between cognitive control ability and intrusive cognitions in PTSD. We review evidence showing that individual differences in HRV at rest are related to prefrontal cortical activity and performance on a broad range of cognitive control tasks. We highlight the importance of inhibition as a mechanism by which HRV promotes successful cognitive control. In addition, we summarize recent research linking individual differences in HRV to performance on laboratory tasks that assess the ability to control unwanted memories and intrusive thoughts. We conclude by suggesting that future studies should examine the role of low HRV as a risk factor for developing PTSD. PMID:25076929

Gillie, Brandon L.; Thayer, Julian F.

2014-01-01

367

Efficacy of a Low Dose of Estrogen on Antioxidant Defenses and Heart Rate Variability  

PubMed Central

This study tested whether a low dose (40% less than the pharmacological dose of 17-? estradiol) would be as effective as the pharmacological dose to improve cardiovascular parameters and decrease cardiac oxidative stress. Female Wistar rats (n = 9/group) were divided in three groups: (1) ovariectomized (Ovx), (2) ovariectomized animals treated for 21 days with low dose (LE; 0.2?mg), and (3) high dose (HE; 0.5?mg) 17-? estradiol subcutaneously. Hemodynamic assessment and spectral analysis for evaluation of autonomic nervous system regulation were performed. Myocardial superoxide dismutase (SOD) and catalase (CAT) activities, redox ratio (GSH/GSSG), total radical-trapping antioxidant potential (TRAP), hydrogen peroxide, and superoxide anion concentrations were measured. HE and LE groups exhibited an improvement in hemodynamic function and heart rate variability. These changes were associated with an increase in the TRAP, GSH/GSSG, SOD, and CAT. A decrease in hydrogen peroxide and superoxide anion was also observed in the treated estrogen groups as compared to the Ovx group. Our results indicate that a low dose of estrogen is just as effective as a high dose into promoting cardiovascular function and reducing oxidative stress, thereby supporting the approach of using low dose of estrogen in clinical settings to minimize the risks associated with estrogen therapy. PMID:24738017

Casali, Karina Rabello; Baraldi, Dhãniel; Conzatti, Adriana; Araújo, Alex Sander da Rosa; Khaper, Neelam; Llesuy, Susana; Rigatto, Katya; Belló-Klein, Adriane

2014-01-01

368

Time- and state-dependent analysis of autonomic control in narcolepsy: higher heart rate with normal heart rate variability independent of sleep fragmentation.  

PubMed

Narcolepsy with hypocretin deficiency is known to alter cardiovascular control during sleep, but its aetiology is disputed. As cardiovascular control differs between sleep states, and narcolepsy affects sleep architecture, controlling for both duration and transitions of sleep states is necessary. This study therefore aimed to assess heart rate and its variability in narcolepsy during sleep taking these factors into account. The study included 12 medication-naïve patients with narcolepsy with cataplexy and hypocretin deficiency (11 male, 16-53 years old), and 12 sex- and age-matched healthy controls (11 male, 19-55 years). All subjects underwent 1-night ambulatory polysomnography recording. Cardiovascular parameters were calculated for each 30-s epoch. Heart rate was significantly higher in patients with narcolepsy than in controls in all sleep states and during wakefulness prior to sleep. Groups did not differ in heart rate variability measures. The effects of sleep state duration on heart rate and its variability were similar between patients and controls. In conclusion, heart rate was consistently higher in patients with narcolepsy than controls, independent of sleep stage and sleep fragmentation. A direct effect of hypocretin deficiency therefore seems probable. PMID:25382307

van der Meijden, Wisse P; Fronczek, Rolf; Reijntjes, Robert H A M; Corssmit, Eleonora P M; Biermasz, Nienke R; Lammers, Gert Jan; van Dijk, J Gert; Thijs, Roland D

2014-11-01

369

Short-term Parameters of Heart Rate Variability During Balanced Anaesthesia with Administration of Two Different Inhalation Anaesthetics  

PubMed Central

Introduction: Heart rate variability which denotes variations of the length of consecutive heart cycles has been suggested to reflect the modulation of heart rate by autonomic nervous system. Methods: Sixty four patients of ASA I and ASA II status scheduled for elective abdominal surgical procedures were randomly allocated to group 1 and group 2. Premedication and induction of anaesthesia were performed with same agents. After orotracheal intubation maintenance of balanced anaesthesia was based on administration of same induction agents,opioids and muscle relaxant while delivery of gaseous mixture with sevoflurane in the group 1 (n=32) and isoflurane in the group 2(n=32). Haemodynamic parameters were monitored in perioperative and electrocardiogram was recorded by holter ECG recorder, while the analysis of the parameters were performed by corresponding softwares . Data were presented as mean values of logarithmic (natural logarithm) values of the power of the total spectrum of heart rate variability(TP), mean values of the logarithmic values of low frequency band (LF), mean values of the logarithmic values of high frequency range(HF), and mean values of SD1 and SD2 parameters. Results: Analysis of the values of hemodynamic parameters has shown changes of haemodynamic parameters during perioperative period without significant statistical differences between the groups. Analysis of the logarhitmic values of parameters of heart rate variability of frequency domain has shown changes of the total spectrum power and LF and HF spestra with variations of the values of total power spectrum and individual components of the spectrum of heart rate variability during the balanced anaesthesia with administration of two different inhalation anaesthetics, without statistically significant differences between the groups. Conclusion: The results have shown that during balanced anaesthesia with two different inhalation anaesthetics there are variations of haemodynamic variables and parameters of heart rate variability without statistically significance that could show the difference between the groups and different agents administered. PMID:25568550

Omerbegovi?, Meldijana

2014-01-01

370

An infrared high rate video imager for various space applications  

NASA Astrophysics Data System (ADS)

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 and high Earth orbiting spacecraft as well as on planetary and lunar orbiters. The optimum wavelength range varies depending on the application but we will focus here on the near infrared, partly since it allows exploration of a new field and partly because it, in many cases, allows operation both during day and night. Such an instrument has to our knowledge never flown in space so far. The only sensors of a similar kind fly on US defense satellites for monitoring launches of ballistic missiles. The data from these sensors, however, is largely inaccessible to scientists. We have developed a bread-board version of such an instrument, the SPOSH-IR. The instrument is based on an earlier technology development - SPOSH - a Smart Panoramic Optical Sensor Head, for operation in the visible range, but with the sensor replace by a cooled IR detector and new optics. The instrument is using a Sofradir 320x256 pixel HgCdTe detector array with 30µm pixel size, mounted directly on top of a four stage thermoelectric Peltier cooler. The detector-cooler combination is integrated into an evacuated closed package with a glass window on its front side. The detector has a sensitive range between 0.8 and 2.5 µm. The optical part is a seven lens design with a focal length of 6 mm and a FOV 90deg by 72 deg optimized for use at SWIR. The detector operates at 200K while the optics operates at ambient temperature. The optics and electronics for the bread-board has been designed and built by Jena-Optronik, Jena, Germany. This talk will present the design and the strong and the weak points as found through testing will be identified. Possible alternatives for improvements will be discussed and two flight applications will be outlined.

Svedhem, Hâkan; Koschny, Detlef

2010-05-01

371

Quantification of Bone Growth Rate Variability in Rats Exposed to Micro- (near zero G) and Macrogravity (2G)  

NASA Technical Reports Server (NTRS)

Our stated primary objective is to quantify the growth rate variability of rat lamellar bone exposed to micro and macrogravity (2G). The primary significance of the proposed work is that an elegant method will be established that unequivocally characterizes the morphological consequences of gravitational factors on developing bone. The integrity of this objective depends upon our successful preparation of thin sections suitable for imaging individual bone lamellae, and our imaging and quantitation of growth rate variability in populations of lamellae from individual bone samples.

Bromage, Timothy G.; Doty, Stephen B.; Smolyar, Igor; Holton, Emily

1996-01-01

372

Quantitation of Bone Growth Rate Variability in Rats Exposed to Micro-(near zero G) and Macrogravity (2G)  

NASA Technical Reports Server (NTRS)

Our stated primary objective is to quantify the growth rate variability of rat lamellar bone exposed to micro- (near zero G: e.g., Cosmos 1887 & 2044; SLS-1 & SLS-2) and macrogravity (2G). The primary significance of the proposed work is that an elegant method will be established that unequivocally characterizes the morphological consequences of gravitational factors on developing bone. The integrity of this objective depends upon our successful preparation of thin sections suitable for imaging individual bone lamellae, and our imaging and quantitation of growth rate variability in populations of lamellae from individual bone samples.

Bromage, Timothy G.; Doty, Stephen B.; Smolyar, Igor; Holton, Emily

1997-01-01

373

Analytical Treatment of the Metabolic Effects of Isocaloric Stimulant on Heart Rate Variability as Measured by Electrocardiograph  

NASA Astrophysics Data System (ADS)

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.

Taffe, Lauren Rachelle

374

Variability in solar radiation and temperature explains observed patterns and trends in tree growth rates across four tropical forests  

PubMed Central

The response of tropical forests to global climate variability and change remains poorly understood. Results from long-term studies of permanent forest plots have reported different, and in some cases opposing trends in tropical forest dynamics. In this study, we examined changes in tree growth rates at four long-term permanent tropical forest research plots in relation to variation in solar radiation, temperature and precipitation. Temporal variation in the stand-level growth rates measured at five-year intervals was found to be positively correlated with variation in incoming solar radiation and negatively related to temporal variation in night-time temperatures. Taken alone, neither solar radiation variability nor the effects of night-time temperatures can account for the observed temporal variation in tree growth rates across sites, but when considered together, these two climate variables account for most of the observed temporal variability in tree growth rates. Further analysis indicates that the stand-level response is primarily driven by the responses of smaller-sized trees (less than 20 cm in diameter). The combined temperature and radiation responses identified in this study provide a potential explanation for the conflicting patterns in tree growth rates found in previous studies. PMID:22833269

Dong, Shirley Xiaobi; Davies, Stuart J.; Ashton, Peter S.; Bunyavejchewin, Sarayudh; Supardi, M. N. Nur; Kassim, Abd Rahman; Tan, Sylvester; Moorcroft, Paul R.

2012-01-01

375

18 CFR 35.1 - Application; obligation to file rate schedules, tariffs and certain service agreements.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Application; obligation to file rate schedules, tariffs and certain service... § 35.1 Application; obligation to file rate schedules, tariffs and certain service... (a) Every public utility shall file with the Commission and...

2010-04-01

376

SPATIALLY VARIABLE INSECTICIDE APPLICATIONS FOR EARLY SEASON CONTROL OF COTTON INSECT PESTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Our research has shown that cotton insect pests, specifically tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae), can be controlled early season in commercial cotton fields in Mississippi, USA, using spatially variable insecticide applications. Technology was develo...

377

Analysis of the electrical characteristics of a Westinghouse variable speed generating system for wind turbine applications  

Microsoft Academic Search

Variable speed electric generating technology can enhance the general use of wind energy in electric utility applications. This enhancement results from two characteristic properties of variable speed wind turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire wind turbine system, and an improvement in the overall efficiency by using a more

J. I. Herrera; T. W. Reddoch

1988-01-01

378

The factors to be considered in the correct cable for variable frequency drive applications on cranes  

Microsoft Academic Search

On a more frequent basis, variable frequency drives are being installed in crane applications where the power, controls and instrumentation cables must be free flexing or routed through a mechanical cable handling system. The electromagnetic interference caused by the use of variable frequency drives must be considered in the planning stage of any new or retrofit crane project

S. G. LaPidus

1998-01-01

379

The application of variable fuzzy sets theory in coastal waterway selection  

Microsoft Academic Search

Variable fuzzy set theory (VFS) has evolved into a valuable method to solve multi-criteria decision making problems under fuzzy environments. This paper is concerned with the exposition of VFS theory and its application on coastal waterway selection. First, basic conceptions of VFS theory are described including relative difference function and relative membership function with interval values. Then a variable fuzzy

Guolei Tang; Xiangqun Song; Zijian Guo; Wenyuan Wang; Ningning Li

2010-01-01

380

Communications technology satellite - A variable conductance heat pipe application  

NASA Technical Reports Server (NTRS)

A variable-conductance heat pipe system (VCHPS) has been designed to provide thermal control for a transmitter experiment package (TEP) to be flown on the Communications Technology Satellite. The VCHPS provides for heat rejection during TEP operation and minimizes the heat leak during power down operations. The VCHPS described features a unique method of aiding priming of arterial heat pipes and a novel approach to balancing heat pipe loads by staggering their control ranges.

Mock, P. R.; Marcus, B. D.; Edelman, E. A.

1974-01-01

381

Multi-finger RF MEMS variable capacitors for RF applications  

Microsoft Academic Search

This paper presents a digital type RF MEMS variable capacitor with a tuning range on the order of 10:l. The digital tuning is obtained by having multiple beams suspended on a single pedestal. The typical actuation voltage is approximately 3MOV but can be reduced to the 10-35V range with certain design modifications. The unloaded Q of the capacitor at 1

Hariharasudhan Kannan; Balaji Lakshminarayanan; Thomas Weller

2004-01-01

382

256-Slice CT Angiographic Evaluation of Coronary Artery Bypass Grafts: Effect of Heart Rate, Heart Rate Variability and Z-Axis Location on Image Quality  

PubMed Central

Purpose The objective of this study is to assess the effect of heart rate, heart rate variability and z-axis location on coronary artery bypass graft (CABG) image quality using a 256-slice computed tomography (CT) scanner. Methods A total of 78 patients with 254 CABG (762 graft segments) were recruited to undergo CABG assessment with 256-slice CT and prospective ECG-gating. Two observers rated graft segments for image quality on a 5-point scale. Quantitative measurements were also made. Logistic and cumulative link mixed models were used to assess the predictors of graft image quality. Results Graft image quality was judged as diagnostic (scores 5 (excellent), 4 (good) and 3 (moderate)) in 96.6% of the 762 segments. Interobserver agreement was excellent (kappa ?0.90). Graft image quality was not affected by heart rate level. However, high heart rate variability was associated with an important and significant image quality deterioration (odds ratio 4.31; p ?=? 0.036). Distal graft segments had significantly lower image quality scores than proximal segments (p ? 0.02). Significantly higher noise was noted at the origin of the mammary grafts (p ?=? 0.001), owing to streak artifacts from the shoulders. Conclusion CABG imaging with 270-msec rotation 256-slice CT and prospective ECG-gating showed an adequate image quality in 96.6% of graft segments, and an excellent interobserver agreement. Graft image quality was not influenced by heart rate level. Image quality scores were however significantly decreased in patients with high heart rate variability, as well as in distal graft segments, which are closer to the heart. PMID:24637891

Gramer, Bettina M.; Diez Martinez, Patricia; Chin, Anne S.; Sylvestre, Marie-Pierre; Larrivée, Sandra; Stevens, Louis-Mathieu; Noiseux, Nicolas; Soulez, Gilles; Rummeny, Ernst J.; Chartrand-Lefebvre, Carl

2014-01-01

383

The effects of body posture and temperament on heart rate variability in dairy cows.  

PubMed

Reactivity of cattle affects many aspects of animal production (e.g. reduced milk and meat production). Animals have individual differences in temperament and emotional reactivity, and these differences can affect how animals react to stressful and fear-eliciting events. Heart rate variability (HRV) is a good indicator of stress and balance of the autonomous nervous system, and low parasympathetic activity is connected with higher emotional reactivity. The study had two specific aims: (1) to compare HRV in dairy cows for standing and lying postures (no earlier results available), and (2) to assess whether dairy cows' emotional reactivity is connected to their HRV values. Eighteen dairy cows were subjected twice to a handling test (HT): morning (HT1) and afternoon (HT2), to evaluate emotional reactivity (avoidance score, AS). HRV was measured during HT (standing). HRV baseline values, both standing and lying down, were measured one week before HTs. HRV was analyzed with time and frequency domain analyses and with the Recurrence Quantification Analysis (RQA). Heart rate (HR), low-frequency/high-frequency band ratio (LH/HF), % determinism (%DET) and longest diagonal line segment in the recurrence plot (Lmax) were higher (p<0.05) while the cows were standing than when lying down, whereas the root mean square of successive R-R intervals (RMSSD) (p<0.05) and power of the high-frequency band (HF) (p<0.1) were higher while the animals were lying down. HR, the standard deviation of all interbeat intervals (SDNN), RMSSD, HF, power of the low-frequency band (LF), % recurrence (%REC), %DET, Shannon entropy (p<0.05), and HF (p<0.1) were higher during the handling test compared to standing baseline values. AS (i.e. tendency to avoid handling) correlated positively with SDNN (r=0.48, p<0.05), RMSSD (r=0.54, p<0.05), HF, RMSSD (r=0.46, p<0.1) and LF (r=0.57, p<0.05), and negatively with %DET (r=-0.53, p<0.05), entropy (r=-0.60, p<0.05) and Lmax (r=-0.55, p<0.05) in the baseline HRV measurements. AS correlated positively with SDNN (r=0.43, p<0.1) and HF (r=0.53, p<0.05) during HT. Some HRV parameters (HR, LF, %REC, %DET) indicated that the handling test may have caused stress to the experimental cows, although some HRV results (SDNN, RMSSD, HF, entropy) were controversial. The correlations between HRV variables and AS suggest that the emotional reactivity of the cow can be assessed from the baseline values of the HRV. It is debatable, however, whether the handling test used in the present study was a good method of causing mild stress in dairy cattle, since it may have even induced a positive emotional state. The posture of the cow affected HRV values as expected (based on results from other species), so that while standing a shift towards more sympathetic dominance was evident. Our results support the idea that linear (time and frequency domain) and non-linear (RQA) methods measuring HRV complement each other, but further research is needed for better understanding of the connection between temperament and HRV. PMID:25481355

Frondelius, Lilli; Järvenranta, Kirsi; Koponen, Taija; Mononen, Jaakko

2015-02-01

384

Ivabradine Improves Heart Rate Variability in Patients with Nonischemic Dilated Cardiomyopathy  

PubMed Central

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

Kurtoglu, Ertugrul; Balta, Sevket; Karakus, Yasin; Yasar, Erdogan; Cuglan, Bilal; Kaplan, Ozgur; Gozubuyuk, Gokhan

2014-01-01

385

Sleep processes exert a predominant influence on the 24-h profile of heart rate variability.  

PubMed

Adverse cardiovascular events are known to exhibit 24-h variations with a peak incidence in the morning hours and a nonuniform distribution during the night. The authors examined whether these 24-h variations could be related to circadian or sleep-related changes in heart rate (HR) and in HR variability (HRV). To differentiate the effect of circadian and sleep-related influences, independent of posture and of meal ingestion, seven normal subjects were studied over 24 h, once with nocturnal sleep from 2300 to 0700 h and once after a night of sleep deprivation followed by 8 h of daytime sleep from 0700 to 1500 h. The subjects were submitted to constant conditions (continuous enteral nutrition and bed rest). HRV was calculated every 5 min using two indexes: the standard deviation of normal R-R intervals (SDNN) and the ratio of low-frequency to low-frequency plus high-frequency power. Sleep processes exerted a predominant influence on the 24-h profiles of HR and HRV, with lowest HRV levels during slow wave sleep, high levels during REM sleep and intrasleep awakenings, and abrupt increases in HR at each transition from deeper sleep to lighter sleep or awakenings. The circadian influence was smaller, except for SDNN, which displayed a nocturnal increase of 140% whether the subjects slept or not. This study demonstrates that 24-h variations in HR and HRV are little influenced by the circadian clock andare mainly sleep-stage dependent. The results suggest an important role for exogenous factors in the morning increase in cardiovascular events. During sleep, the sudden rises in HR at each transition from deeper sleep to lighter sleep or awakenings might precipitate the adverse cardiac events. PMID:12465887

Viola, Antoine U; Simon, Chantal; Ehrhart, Jean; Geny, Bernard; Piquard, François; Muzet, Alain; Brandenberger, Gabrielle

2002-12-01

386

Sympathetic control of short-term heart rate variability and its pharmacological modulation.  

PubMed

The static relationship between heart rate (HR) and the activity of either vagal or sympathetic nerves is roughly linear within the physiological range of HR variations. The dynamic control of HR by autonomic nerves is characterized by a fixed time delay between the onset of changes in nerve activity and the onset of changes in HR. This delay is much longer for sympathetically than for vagally mediated changes in HR. In addition, the kinetics of the HR responses shows the properties of a low-pass filter with short (vagal) and long (sympathetic) time constants. These differences might be secondary to differences in nervous conduction times, width of synaptic cleft, kinetics of receptor activation and post-receptor events. Because of the accentuated low-pass filter characteristics of the HR response to sympathetic modulation, sympathetic influences are almost restricted to the very-low-frequency component of HR variability, but the chronotropic effects of vagal stimulation usually predominate over those of sympathetic stimulation in this frequency band. Oscillations in cardiac sympathetic nerve activity are not involved in respiratory sinus arrhythmia (high-frequency component) and make a minor contribution to HR oscillations of approximately 10-s period (low-frequency component of approximately 0.1 Hz), at least in the supine position. In the latter case, HR oscillations are derived mainly from a baroreflex, vagally mediated response to blood pressure Mayer waves. Beta-blockers and centrally acting sympathoinhibitory drugs share the ability to improve the baroreflex control of HR, possibly through vagal facilitation, which might be beneficial in several cardiovascular diseases. PMID:17635171

Elghozi, Jean-Luc; Julien, Claude

2007-08-01

387

Auditory stimulation with music influences the geometric indices of heart rate variability in men  

PubMed Central

Background Chronic classical music was reported to increase parasympathetic activitywhen evaluating heart rate variability (HRV). It is poor in the literature investigation of the acute effects of baroque and heavy metal styles of musical auditory stimulation on HRV. In this study we evaluated the acute effects of relaxant baroque and excitatory heavy metal music on the geometric indices of HRV in healthy men. Method The study was performed in 12 healthy men between 18 and 30 years old. We excluded persons with previous experience with music instrument and those who had affinity with the song styles. We analyzed the following indices: RRtri, TINN and Poincaré plot (SD1, SD2 and SD1/SD2 ratio). HRV was recorded at rest for ten minutes. Subsequently they were exposed to relaxant baroque or excitatory heavy metal music for five minutes through an earphone. After the first music exposure they remained at rest for more five minutes and them they were exposed again to Baroque or Heavy Metal music (65–80 dB). The sequence of songs was randomized for each individual. Results The RRTri and SD2 indices were reduced during the heavy metal musical auditory stimulation (p??0.05).The qualitative Poincaré plot analysis indicated that during relaxant classical baroque music there was observed a higher beat-to-beat dispersion of RR intervals compared with no music exposure and during excitatory heavy metal musical auditory stimulation, showing higher HRV. Conclusion We suggest that excitatory heavy metal music acutely decreases global HRV. PMID:24883104

2014-01-01

388

Indoor Air Pollution, Nighttime Heart Rate Variability and Coffee Consumption among Convenient Store Workers  

PubMed Central

Background The association between ambient air pollution and heart rate variability (HRV) has been well-documented. Little is known about the association of HRV at night with indoor air pollution and coffee consumption. The aim of this study was to investigate the association of HRV indices with indoor air pollution, working time and coffee consumption. Methods We recruited 60 young healthy convenient store workers to monitor indoor PM2.5 (particulate matter with an aerodynamic diameter ? 2.5 µm) exposures, coffee consumption (yes vs. no) and HRV indices during daytime (0700–1500 hours) and nighttime (2300-0700 hours). We used linear mixed effects models to assess the associations of HRV indices with indoor PM2.5 exposures and coffee consumption. Results We observed the inverse association between indoor PM2.5 exposures and HRV indices, with a decrease in all HRV indices with increased indoor PM2.5 exposures. However, the decrease was most pronounced during nighttime, where a 1 interquartile range (IQR) increase in indoor PM2.5 at 4-hr time-weighted moving average was associated with a change of ?4.78% 5-min standard deviation (SD) of normal-to-normal intervals for 5-min segment (SDNN) and ?3.23% 5-min square root of the mean squared differences of successive intervals for 5-min segment (r-MSSD). Effects of indoor PM2.5 were lowest for participants with coffee consumption during daytime. Conclusions Indoor PM2.5 exposures were associated with decreased 5-min SDNN and 5-min r-MSSD, especially during nighttime. The effect of indoor PM2.5 on HRV indices may be modified by coffee consumption in young healthy convenient store workers. PMID:24312680

Chuang, Kai-Jen; Chuang, Hsiao-Chi; Lin, Lian-Yu

2013-01-01

389

The relationship between resting heart rate variability and erectile tumescence among men with normal erectile function  

PubMed Central

Introduction Individuals with erectile dysfunction have been shown to display lower heart rate variability (HRV), suggesting dysregulation of cardiac autonomic function. No studies have explored whether HRV is predictive of erectile response among men with clinically normal erectile function. Aim To examine associations between resting HRV and objective measures of genital response (i.e., resting penile circumference; erectile tumescence) and self-reported sexual function. Methods The sample comprised 59 male community volunteers (mean age = 20.15 years; SD = 2.52) selected from the control conditions of two previously published studies. Participants reported erectile function in the normal range (scoring ? 26 on the International Index of Erectile Function [IIEF]) and had no history of cardiovascular disease or myocardial infarct. During a laboratory visit, self-report, anthropometric, cardiovascular, and electrocardiographic data were assessed, as well as resting penile circumference and erectile tumescence in response to viewing an erotic film. Main Outcome Measures Resting penile responses, erectile tumescence (circumferential change via penile plethysmography), self-reported sexual function per the IIEF, and both time-domain (standard deviation of beat-to-beat [NN] intervals [SDNN], square root of the mean squared difference of successive NN intervals [RMSSD], and percent of NN intervals for which successive heartbeat intervals differed by at least 50 msec [pNN50]) and frequency-domain (low frequency [LF], high frequency [HF], LF/HF ratio) parameters of HRV were assessed. Results Higher resting HF power and lower resting LF/HF ratio were associated with greater erectile tumescence. There were marginally significant positive associations between mean NN interval and pNN50 and penile tumescence. HRV was not associated with self-reported sexual function or with resting penile circumference. Conclusions Results suggested that, among men without erectile dysfunction, relatively elevated parasympathetic tone was predictive of larger erectile tumescence. Limited variance in sexual function scores may have accounted for the lack of association between HRV and IIEF scores. PMID:23802770

Harte, Christopher B.

2013-01-01

390

Effects of Exercise Training on Heart Rate Variability in Chagas Heart Disease  

PubMed Central

Background: Heart rate variability (HRV) is a marker of autonomic dysfunction severity. The effects of physical training on HRV indexes in Chagas heart disease (CHD) are not well established. Objective: To evaluate the changes in HRV indexes in response to physical training in CHD. Methods: Patients with CHD and left ventricular (LV) dysfunction, physically inactive, were randomized either to the intervention (IG, N = 18) or control group (CG, N = 19). The IG participated in a 12-week exercise program consisting of 3 sessions/week. Results: Mean age was 49.5 ± 8 years, 59% males, mean LVEF was 36.3 ± 7.8%. Baseline HRV indexes were similar between groups. From baseline to follow-up, total power (TP): 1653 (IQ 625 - 3418) to 2794 (1617 - 4452) ms, p = 0.02) and very low frequency power: 586 (290 - 1565) to 815 (610 - 1425) ms, p = 0.047) increased in the IG, but not in the CG. The delta (post - pre) HRV indexes were similar: SDNN 11.5 ± 30.0 vs. 3.7 ± 25.1 ms. p = 0.10; rMSSD 2 (6 - 17) vs. 1 (21 - 9) ms. p = 0.43; TP 943 (731 - 3130) vs. 1780 (921 - 2743) Hz. p = 0.46; low frequency power (LFP) 1.0 (150 - 197) vs. 60 (111 - 146) Hz. p = 0.85; except for high frequency power, which tended to increase in the IG: 42 (133 - 92) vs. 79 (61 - 328) Hz. p = 0.08). Conclusion: In the studied population, the variation of HRV indexes was similar between the active and inactive groups. Clinical improvement with physical activity seems to be independent from autonomic dysfunction markers in CHD. PMID:25098373

Nascimento, Bruno Ramos; Lima, Márcia Maria Oliveira; Nunes, Maria do Carmo Pereira; de Alencar, Maria Clara Noman; Costa, Henrique Silveira; Pinto Filho, Marcelo Martins; Cota, Vitor Emanuel Serafim; Rocha, Manoel Otávio da Costa; Ribeiro, Antonio Luiz Pinho

2014-01-01

391

Is volcanic air pollution associated with decreased heart-rate variability?  

PubMed Central

Objectives To determine the autonomic cardiovascular control among residents of Hawaii who are exposed to varying levels of volcanic air pollution (vog), which consists largely of sulfur dioxide (SO2) and acid aerosols. Methods In a cross-sectional study between April 2006 and June 2008, the authors measured cardiovagal autonomic function by heart-rate variability (HRV) in 72 healthy individuals who lived in four exposure zones on Hawaii Island: vog-free (n=18); episodic exposure to SO2 >200 ppb and acid aerosol (n=19); chronic exposure to SO2 ?30 ppb and acid aerosol (n=15); and chronic exposure to acid aerosols (n=20). Individuals with diabetes or heart disease, or who had smoked in the preceding month were excluded. HRV was measured in all subjects during rest, paced breathing and active standing (Ewing manoeuvre). HRV was analysed in time and frequency domains and compared between the four exposure zones. Results There were no significant differences between exposure zones in HRV, in either time or frequency domains, even after adjustment for age, gender, ethnicity and body mass index. There was no significant HRV change in three individuals in whom HRV was measured before and during an exposure to combined SO2 100–250 ppb and concentration of respirable particles of diameter ?2.5 ? (PM2.5) >500 ?g/m3. Age was significantly correlated with time-domain parameters during paced breathing and the Ewing manoeuvre. Conclusions This study of healthy individuals found no appreciable effects of vog on the autonomic nervous system. PMID:21546995

Chow, Dominic C; Grandinetti, Andrew; Fernandez, Ed; Sutton, A J; Elias, Tamar; Brooks, Barbara; Tam, Elizabeth K

2011-01-01

392

Heart rate variability analysis during head-up tilt test predicts nitroglycerine-induced syncope  

PubMed Central

Objective The aim of this study was to determine whether or not heart rate variability (HRV) analysis during the first 20?min of head-up tilt testing could predict whether patients will develop syncope after nitroglycerine administration. Design 64 patients with previous loss of consciousness underwent head-up tilt testing with the Italian protocol, which involves the administration of nitroglycerine after 20?min of tilt. HRV parameters were analysed from 5?min intervals selected during pretest supine rest (phase 1), the first 5?min (phase 2) and the last 5?min (phase 3) of passive 20?min of tilting, prior to the administration of nitroglycerine. Differences in power (ms2) of the spectral components between the various phases of tilting were calculated for each patient and expressed as ?. Results 20 patients (group 1, 9 women, mean age 43.2±24.5?years) had a syncope during tilt testing after nitroglycerine, while the other 44 (group 2, 24 women, mean age 41±20.5?years) did not. In group 1, the HRV spectral parameters high frequency (HF) and total power (TP) had a significant decrement from phases 2 to 3 (p=0.012 and 0.027, respectively), while in group 2 the average HF and TP values did not change. The ? of spectral parameters between phases 2 and 3 were able to differentiate between the two groups and to predict syncope after nitroglycerine administration (p<0.05). Conclusions HRV analysis within the first 20?min of passive tilting demonstrated that patients with nitroglycerine-induced syncope are characterised by a progressive decrement of parasympathetic activity, which does not occur in patients with a negative response to nitroglycerine. If confirmed on a wider population, HRV analysis could replace nitroglycerine administration and shorten the duration of the tilt test. PMID:25332802

Efremov, Kristian; Brisinda, Donatella; Venuti, Angela; Iantorno, Emilia; Cataldi, Claudia; Fioravanti, Francesco; Fenici, Riccardo

2014-01-01

393

Effects of exercise and hypoxia on heart rate variability and acute mountain sickness.  

PubMed

Acute mountain sickness (AMS) is a common condition among non-acclimatized individuals ascending to high altitude. Exercise, a characteristic feature of hiking and mountaineering, has been suggested to exacerbate AMS prevalence and to cause modifications of the autonomic nervous system. A reduction of the heart rate variability (HRV) is a common finding during acute hypoxia, however characteristics of HRV during exercise in subjects suffering from AMS are unknown. Therefore, the aim of the present study was to investigate the effects of acute normobaric hypoxia (FiO2=11.0% ? 5 500 m) at rest (PHE) and during exercise (AHE) on the cardiac autonomic function and the development of AMS in 20 healthy, male individuals. HRV recordings were performed during normoxia and after 2, 4, 6 and 8 h in hypoxia during PHE and AHE, respectively. AMS was assessed using the Lake Louise Score. During PHE 50% of participants developed AMS and 70% during AHE (p=0.22). The analysis of HRV data showed a significant reduction of total power (TP), high frequency (HF) and low frequency (LF) components and an increase of the LF:HF ratio during PHE, however without further modification during AHE. Exercise did not increase AMS prevalence or severity, but increased "non-gastrointestinal" symptoms including headache, fatigue and dizziness. HRV indices were not related to the overall incidence of AMS or the development of "non-gastrointestinal" symptoms but we detected significant correlations between gastrointestinal complaints and HRV components. Thus, we suggest that the cardiac autonomic modulation during acute normobaric hypoxia does not play an important role in the development of AMS, but seems to be related to gastrointestinal complaints at high altitude. However, the influence of moderate exercise on HRV and AMS is minor, only "non-GI" symptoms seem to be exacerbated when exercise is applied. PMID:23386424

Mairer, K; Wille, M; Grander, W; Burtscher, M

2013-08-01

394

Short-term secondhand smoke exposure decreases heart rate variability and increases arrhythmia susceptibility in mice  

PubMed Central

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

Chen, Chao-Yin; Chow, Drin; Chiamvimonvat, Nipavan; Glatter, Kathryn A.; Li, Ning; He, Yuxia; Pinkerton, Kent E.; Bonham, Ann C.

2008-01-01

395

The Effects of Different Noise Types on Heart Rate Variability in Men  

PubMed Central

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

Sim, Chang Sun; Sung, Joo Hyun; Cheon, Sang Hyeon; Lee, Jang Myung; Lee, Jae Won

2015-01-01

396

Use of the harmonic mean: On averaging count-rate data for variable-time, fixed-count intervals  

SciTech Connect

The average of count rates from measurements performed by accumulating a fixed total number of counts over a variable time interval should be obtained with harmonic mean. Use of an arithmetic mean in these cases will give intuitively incorrect results. Uncertainty estimators for this harmonically averaged counting rate, such as the standard deviation, must also be suitably transformed to correspond to that for the harmonic mean.

Colle, R.

1996-09-01

397

Variable-Temperature Rate Coefficients of Proton-Transfer Equilibrium Reaction C2H4 + H3O+  

E-print Network

Variable-Temperature Rate Coefficients of Proton-Transfer Equilibrium Reaction C2H4 + H3O+ C2H5: The rate coefficients for the forward and reverse proton-transfer reactions C2H4 + H3O+ C2H5 + + H2O and S = (-15.0 ± 0.9) J·mol-1 ·K-1 , respectively. INTRODUCTION Proton-transfer reactions of simple molecules

Sanov, Andrei

398

Double blind placebo controlled trial of short term transdermal scopolamine on heart rate variability in patients with chronic heart failure.  

PubMed Central

OBJECTIVE: To test the hypothesis that short term application of transdermal scopolamine increases heart rate variability (HRV) and restores sympathovagal balance in patients with stable congestive heart failure (CHF). DESIGN: A double blind placebo controlled crossover study. SETTING: Tertiary referral centre. PATIENTS: Twelve patients (mean age 66 (10)) with New York Heart Association class II-IV CHF. All patients had coronary artery disease (mean left ventricular ejection fraction 26.7 (8.9) %). INTERVENTION: Patients were randomly assigned to receive either a placebo skin patch or a transdermal scopolamine patch (Transderm, 0.05 mg/h). Patches remained in place for 48 hours with a 24 hour washout period before crossover. OUTCOME MEASURES: HRV was derived from (a) 24 hour time domain indices (mean RR interval, standard deviation of interbeat interval, and the baseline width of the frequency distribution of RR intervals) and (b) short data set (2.2 mm) power spectral measurements using autoregressive modelling. Autospectral measures were performed in both resting supine and standing (orthostatic) states. The 24 hour Holter record was obtained during the second day of patch application. RESULTS: There was a small but significant (P < 0.05) increase in all time domain HRV variables with scopolamine. There was a paradoxical fall in low frequency (LF) spectral power induced by orthostasis during baseline (-30%) and placebo (-34%) states. Conversely, scopolamine was associated with a 14% increase in LF power during orthostatic stress. Scopolamine thus significantly reduced the orthostatic fall in LF (P < 0.01) compared with either baseline or placebo values. No difference in circadian rhythm was seen between the scopolamine and placebo treatment periods. However, the abrupt fall in the high frequency (vagal) power during the early morning sleep-wake hours was reduced by scopolamine. Scopolamine was also associated with a significant rightward shift in the resting LF central frequency consistent with a vagomimetic effect. CONCLUSION: Patients with chronic stable CHF showed a paradoxical fall in the low frequency (sympathetic) power during orthostatic stress. Transdermal scopolamine applied over a 48 hour period partially restored the balance between sympathetic tone and vagal activity in CHF patients and maintained this balance during orthostatic stress. Images PMID:8795476

Venkatesh, G.; Fallen, E. L.; Kamath, M. V.; Connolly, S.; Yusuf, S.

1996-01-01

399

41 CFR 301-11.102 - What is the applicable M&IE rate?  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false What is the applicable M&IE rate? 301-11.102 Section 301-11... § 301-11.102 What is the applicable M&IE rate? For days of travel which Your applicable M&IE rate is Require lodging The...

2010-07-01

400

Variability of Phyllochron, Plastochron and Rate of Increase in Height in Photoperiod-sensitive Sorghum Varieties  

Microsoft Academic Search

† Background and Aims West African sorghum (Sorghum bicolor) varieties are generally highly photoperiod-sensi- tive, which is a necessary adaptation to the variable onset date of the rainy season and the variable dates of sowing in the savannah zone. Depending on sowing date, plants can produce from 12 to .40 leaves on the main culm, with height varying from 1

B. Clerget; M. Dingkuhn; E. Goze; H. F. W. Rattunde; B. Ney

2008-01-01

401

AN ENVIRONMENTAL ASSESSMENT OF SENSOR-BASED VARIABLE-RATE NITROGEN MANAGEMENT IN CORN  

Technology Transfer Automated Retrieval System (TEKTRAN)

In order to address the problem of nitrate contamination of surface and ground waters, various methods have been used to try to account for spatial variability of N within agricultural fields. One approach to account for this variability and thereby reduce nitrate pollution is in-season site-specif...

402

Detection of subjects with higher self-reporting stress scores using heart rate variability patterns during the day  

Microsoft Academic Search

Heart rate variability (HRV) has been well established to measure instantaneous levels of mental stress. Circadian patterns of HRV features have been reported but their use to estimate levels of mental stress were not studied thoroughly. In this study, we investigated time dependent variations of HRV features to detect subjects under chronic mental stress. Sixty eight subjects were divided into

Desok Kim; Yunhwan Seo; Jaegeol Cho; Chul-Ho Cho

2008-01-01

403

Using heart rate variability analysis to assess the effect of music therapy on anxiety reduction of patients  

Microsoft Academic Search

Music therapy has been considered to reduce the anxiety of patients, but the mechanism of music therapy remains to be investigated. Psychophysiological researchers have revealed that the autonomic activities relate to the anxiety. Heart rate variability (HRV) analysis has been used to assess the autonomic activities hence it may be a useful tool for evaluate the effects of music therapy

H. W. Chiu; L. S. Lin; M. C. Kuo; H. S. Chiang; C. Y. Hsu

2003-01-01

404

Impact of Pubertal Development and Physical Activity on Heart Rate Variability in Overweight and Obese Children in Taiwan  

ERIC Educational Resources Information Center

Child obesity is frequently associated with dysfunction of autonomic nervous system. Children in pubertal development were suggested to be vulnerable to autonomic nervous system problems such as decrease of heart rate variability from dysregulation of metabolic control. This study explored the influence of pubertal development on autonomic nervous…

Chen, Su-Ru; Chiu, Hung-Wen; Lee, Yann-Jinn; Sheen, Tzong-Chi; Jeng, Chii

2012-01-01

405

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

E-print Network

Heart rate variability during REM and non-REM sleep in preterm neonates with and without abnormal and the eventual home monitoring. Results: Periods of non-REM sleep have lower noise limit values and can be distinguished significantly from periods of REM sleep and from the total recording period. The presence

406

An in situ study of respiratory variables in three British sublittoral crabs with different routine rates of activity  

Microsoft Academic Search

To assess the respiratory physiology of marine crabs in situ, velvet swimming crabs, Necora puber, edible crabs, Cancer pagarus, and spider crabs, Maja squinado were sampled in the sublittoral zone by subaqua divers. Measurements included routine rates of oxygen uptake (?O2) and analysis of oxygen levels and acid–base variables of haemolymph samples withdrawn from crabs immediately after capture and analysed

A. J. S Watt; N. M Whiteley; E. W Taylor

1999-01-01

407

Variable rate fertilization for maize and its effects based on the site-specific soil fertility and yield  

Technology Transfer Automated Retrieval System (TEKTRAN)

The experiments of variable rate fertilization (VRF) for maize were carried out using a self-developed VRF system. In the studies, prescriptions of VRF were made for maize according to the nutrient levels in soil and the theory of yield goal. The results of this study have shown that VRF increased...

408

Power spectral analysis of heart-rate variability reflects the level of cardiac autonomic activity in rabbits  

Microsoft Academic Search

Power spectral analysis of heart rate (HR[ variability was tested in conscious rabbits to assess the reliability of this method for assessing cardiac autonomic function in normal rabbits under resting conditions. Evaluation of power spectrum was performed in 5 rabbits under normal resting conditions and after sympathetic, parasympathetic and combined sympathetic plus parasympathetic blockade. Rabbits were randomly assigned to undergo

Viatcheslav A. Moguilevski; Louise Shiel; Judith Oliver; Barry P. McGrath

1996-01-01

409

Five-minute recordings of heart rate variability in obsessive–compulsive disorder, panic disorder and healthy volunteers  

Microsoft Academic Search

Background: Recent studies have used spectral analysis of heart rate variability (HRV) to study autonomous nervous system (ANS) function in panic disorder (PD). Most studies reported a reduced HRV in resting PD patients, suggesting increased sympathetic and decreased parasympathetic tone. In obsessive–compulsive disorder (OCD) inconsistent findings have been reported on ANS function and to date no studies have been carried

B. R. Slaap; M. M. A. Nielen; M. L. Boshuisen; A. M. van Roon; J. A. den Boer

2004-01-01

410

CHANGES IN HEART RATE VARIABILITY AND LUNG FUNCTION OBSERVED IN NC PATROL TROOPERS EXPOSED TO PM AND AIR TOXICS  

EPA Science Inventory

Changes in Heart Rate Variability and Lung Function in NC Patrol Troopers exposed to PM and Air Toxics Michael Riediker1, Wayne E Cascio1, Robert B Devlin2, Thomas Griggs1&4, Margaret Herbst1, Ronald W Williams3, Steve P McCorquodale4, Philip A Bromberg1 1) University o...

411

Ascertainment bias in rate ratio estimation from case-sibling control studies of variable age-at-onset  

E-print Network

Ascertainment bias in rate ratio estimation from case-sibling control studies of variable age-mail: langholz@hsc.usc.edu #12;Abstract Motivated by a Finnish case-control study of early onset diabetes period of the study or including all cases but eliminating the proband as a control for non

Goldstein, Larry

412

Abstract--Cardiovascular variables such as heart rate (HR) and blood pressure (BP) are robustly regulated by an  

E-print Network

Abstract--Cardiovascular variables such as heart rate (HR) and blood pressure (BP) are robustly. We present exploratory results based on a simulation study of the cardiovascular system, and real-- Cardiovascular control, switching linear dynamical systems, baroreflex I. INTRODUCTION HYSIOLOGICAL systems often

Chen, Yiling

413

Evaluation of the Stormwater Capture Potential of New York City Soils: Implications of Infiltration Rate Variability on Urban Runoff Predictions  

Microsoft Academic Search

The properties used to characterize soils and, more specifically, those that are used to describe the rate at which water infiltrates into them, are key parameters in most rainfall-runoff models. Because these parameters are known to be highly variable, they are a known source of uncertainty in our ability to predict runoff from pervious surfaces. The goals of this study

Kimberly A DiGiovanni; Franco Montalto; Alisha Goldstein

2010-01-01

414

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...

415

Analysis of the mobile phone effect on the heart rate variability by the calculation of correlation dimension  

Microsoft Academic Search

In this work, the effect of the electromagnetic radiation generated by mobile phone, on the heart rate variability (HRV) has been investigated using correlation dimension calculation which is a nonlinear analysis method. The 17 volunteer subjects participated to our work and the experiment is designed as three periods and each period have 7 minutes. The electrocardiogram (ECG) signals were recorded

Derya Yilmaz; Metin Yildiz

2009-01-01

416

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...

417

Differences in mean and variability of heart rate and ambulatory rate-pressure product when valsartan or carvedilol is added to lisinopril.  

PubMed

Guidelines recommend combining ?-blockers and angiotensin-converting enzyme (ACE) inhibitors in high-risk heart disease but not in the initial treatment of hypertension. The mechanism of this benefit has not been determined. After 3 weeks of lisinopril (L, 40 mg/day) run-in, 30 subjects entered a single-blinded, forced-titration, crossover study in which carvedilol (C, 20 then 40 mg/day) or a control renin-angiotensin blocker, valsartan (V, 160 then 320 mg/day) were added to L. Ambulatory blood pressure (ABP) and heart rate monitoring was performed at the end of each period. Rate-pressure product (RPP, systolic BP × heart rate, an indicator of cardiac oxygen consumption) was measured over 24 hours, daytime (6 am to midnight), and nighttime (midnight to 6 am) periods. Variability (standard deviation and range) of RPP, BP, and heart rate was also investigated. After 4 weeks, mean 24-hour systolic BP was about 8 mm Hg lower when either V or C was added to L (P < .01 each). Heart rate was consistently lower with C (8 beats/min over 24 hours, P < .000) but was slightly increased with V (about 2 beats/min, P = NS). Consequently, C lowered RPP to a greater degree than V over 24 hours (about 8% vs. 2%, P < .000) and during daytime and nighttime periods (P < .000 each). In addition, RPP variability (SD but not range) was consistently lower on C than V. When added to L, C reduces the mean and variability (SD) of 24-hour heart rate and cardiac workload to a greater degree than valsartan. These effects may contribute to the outcome benefits observed with ?-blocker-ACE inhibitor combinations. PMID:23107894

Izzo, Joseph L; Yedlapati, Siva H; Faheem, Sheikh M; Younus, Usman; Osmond, Peter J

2012-01-01

418

Variable-configuration UUVs for marine science applications  

Microsoft Academic Search

In this article, after a brief overview of trends in underwater unmanned vehicle (UUV) design and applications, results in developing an automatic guidance and control system for Romeo are presented. Attention is focused on the design, development, and testing in the operating conditions of a bottom and ice-canopy following system and on the development of methodologies for the at-field identification

M. Caccia; R. Bono; G. Bruzzone; G. Veruggio

1999-01-01

419

Seasonal changes in physical performance and heart rate variability in high level futsal players.  

PubMed

The aim of this study was to determine the changes in physical performance and resting heart rate variability (HRV) in professional futsal players during the pre-season and in-season training periods. 11 athletes took part in the study (age=24.3±2.9 years; height=176.3±5.2 cm; weight=76.1±6.3 kg), and performed a repeated-sprint ability (RSA) test [6×40 m (20+20 m with a 180° change of direction) sprints separated by 20 s of passive recovery] and Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) at 3 different moments (M1=beginning of pre-season; M2=end of pre-season; M3=mid in-season). The HRV indices were assessed at the same moments. After the short pre-season (3-week), mean RSA time (RSAmean) (M1=7.43±0.2 s; M2=7.24±0.2 s; P=0.003), decrement in RSA performance (RSAdecrement) (M1=6.7±0.3%; M2=5.0±0.9%; P=0.001), and Yo-Yo IR1 distance (M1=1.244±298 m; M2=1.491±396 m; P=0.002) were significantly improved (P<0.05). During the in-season (i. e., M3), performance in Yo-Yo IR1 and RSAmean were maintained. In contrast, RSAbest (M2=6.89±0.2 to M3=6.69±0.3; P=0.001) was improved and RSAdecrement (M2=5.0±0.9% to M3=6.6±0.9%; P=0.001) was impaired. At M2, there was an increase in HRV vagal-related indices compared with M1 that was maintained at M3. In conclusion, after a short pre-season, futsal players improved their RSA and Yo-Yo IR1 performance with concomitant improvements in HRV. These indices were maintained during the in-season period while RSAbest was improved and RSAdecrement impaired. Frequent monitoring of these performances and HRV indices may assist with identification of individual training adaptations and/or early signs of maladaption. PMID:23143705

Oliveira, R S; Leicht, A S; Bishop, D; Barbero-Álvarez, J C; Nakamura, F Y

2013-05-01

420

Short-term vs. long-term heart rate variability in ischemic cardiomyopathy risk stratification  

PubMed Central

In industrialized countries with aging populations, heart failure affects 0.3–2% of the general population. The investigation of 24 h-ECG recordings revealed the potential of nonlinear indices of heart rate variability (HRV) for enhanced risk stratification in patients with ischemic heart failure (IHF). However, long-term analyses are time-consuming, expensive, and delay the initial diagnosis. The objective of this study was to investigate whether 30 min short-term HRV analysis is sufficient for comparable risk stratification in IHF in comparison to 24 h-HRV analysis. From 256 IHF patients [221 at low risk (IHFLR) and 35 at high risk (IHFHR)] (a) 24 h beat-to-beat time series (b) the first 30 min segment (c) the 30 min most stationary day segment and (d) the 30 min most stationary night segment were investigated. We calculated linear (time and frequency domain) and nonlinear HRV analysis indices. Optimal parameter sets for risk stratification in IHF were determined for 24 h and for each 30 min segment by applying discriminant analysis on significant clinical and non-clinical indices. Long- and short-term HRV indices from frequency domain and particularly from nonlinear dynamics revealed high univariate significances (p < 0.01) discriminating between IHFLR and IHFHR. For multivariate risk stratification, optimal mixed parameter sets consisting of 5 indices (clinical and nonlinear) achieved 80.4% AUC (area under the curve of receiver operating characteristics) from 24 h HRV analysis, 84.3% AUC from first 30 min, 82.2 % AUC from daytime 30 min and 81.7% AUC from nighttime 30 min. The optimal parameter set obtained from the first 30 min showed nearly the same classification power when compared to the optimal 24 h-parameter set. As results from stationary daytime and nighttime, 30 min segments indicate that short-term analyses of 30 min may provide at least a comparable risk stratification power in IHF in comparison to a 24 h analysis period. PMID:24379785

Voss, Andreas; Schroeder, Rico; Vallverdú, Montserrat; Schulz, Steffen; Cygankiewicz, Iwona; Vázquez, Rafael; Bayés de Luna, Antoni; Caminal, Pere

2013-01-01