Note: This page contains sample records for the topic variable rate applications from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Field Assessment of A Variable-rate Aerial Application System  

Technology Transfer Automated Retrieval System (TEKTRAN)

Several experiments were conducted to evaluate the system response of a variable-rate aerial application controller to changing flow rates. The research is collaboration between the USDA, ARS, APTRU and Houma Avionics, USA, manufacturer of a widely used flow controller designed for agricultural airc...

2

Development of variable-rate sprayer for nursery liner applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

3

Variable Rate Lime Application in Louisiana Sugarcane Production Systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

Precision agriculture may offer sugarcane growers a management system that decreases costs and maximizes profits, while minimizing any potential negative environmental impact. The utility of variable-rate (VR) lime application in the initial production year (plant cane) of a 3-yr sugarcane crop cyc...

4

Improving flow response of a variable-rate aerial application system by interactive refinement  

Microsoft Academic Search

Experiments were conducted to evaluate response of a variable-rate aerial application controller to changing flow rates and to improve its response at correspondingly varying system pressures. System improvements have been made by refinement of the control algorithms over time in collaboration with the system manufacturer, Houma Avionics, Houma, LA, USA. The variable-rate application system consists of Differential Global Positioning System

Steven J. Thomson; Yanbo Huang; James E. Hanks; Daniel E. Martin; Lowrey A. Smith

2010-01-01

5

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

6

Evaluating variable rate fungicide applications for control of Sclerotinia  

Technology Transfer Automated Retrieval System (TEKTRAN)

Oklahoma peanut growers continue to try to increase yields and reduce input costs. Perhaps the largest input in a peanut crop is fungicide applications. This is especially true for areas in the state that have high disease pressure from Sclerotinia. On average, a single fungicide application cost...

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 COMPARISON OF CONVENTIONAL AND VARIABLE RATE LIME APPLICATION METHODS IN SOUTH LOUISIANA SUGARCANE FIELDS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Louisiana sugarcane producers continue to face increased economic pressure. Growers must find ways to decrease costs and maximize profits, while minimizing potential negative environmental impacts. Precision agriculture, specifically, variable rate lime and fertilizer application, may offer an impor...

9

A Comparison of Conventional and Variable Rate Lime Application Methods in South Louisiana Sugarcane Fields  

Technology Transfer Automated Retrieval System (TEKTRAN)

Louisiana sugarcane producers continue to face increased economic pressure. Growers must find ways to decrease costs and maximize profits, while minimizing potential negative environmental impacts. Precision agriculture, specifically, variable rate lime and fertilizer application, may offer an imp...

10

A Ferrofluidic Magnetic Micropump for Variable-Flow-Rate Applications  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

11

An Admission Control Framework for Applications with Variable Consumption Rates in Client-Pull Architectures  

Microsoft Academic Search

Highly interactive multimedia applications require variable data rates during their presentation. Current admission control mechanisms do not address the variable data rate requirements appropriately for the following reasons: (1) classical admission control mechanisms are based on the server-push approach, where the required data rate has to be estimated in advance, and (2) worst-case resource reservation is not economic. Client-pull models

Silvia Hollfelder; Karl Aberer

1998-01-01

12

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

NASA Astrophysics Data System (ADS)

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

Al-Gaadi, Khalid Ali

1998-12-01

13

Improving Flow Response of a Variable-rate Aerial Application System by Interactive Refinement  

Technology Transfer Automated Retrieval System (TEKTRAN)

Experiments were conducted to evaluate response of a variable-rate aerial application controller to changing flow rates and to improve its response at correspondingly varying system pressures. System improvements have been made by refinement of the control algorithms over time in collaboration with ...

14

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...

15

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

16

Air velocity distributions from a variable-rate air-assisted sprayer for tree applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

A capability that implements tree structure to control liquid and air flow rates is the preferential design in the development of variable-rate orchard and nursery sprayers. Air jet velocity distributions from an air assisted, five-port sprayer which was under the development to achieve variable-rat...

17

Remote sensing and implications for variable-rate application using agricultural aircraft  

NASA Astrophysics Data System (ADS)

Aircraft routinely used for agricultural spray application are finding utility for remote sensing. Data obtained from remote sensing can be used for prescription application of pesticides, fertilizers, cotton growth regulators, and water (the latter with the assistance of hyperspectral indices and thermal imaging). Digital video was used to detect weeds in early cotton, and preliminary data were obtained to see if nitrogen status could be detected in early soybeans. Weeds were differentiable from early cotton at very low altitudes (65-m), with the aid of supervised classification algorithms in the ENVI image analysis software. The camera was flown at very low altitude for acceptable pixel resolution. Nitrogen status was not detectable by statistical analysis of digital numbers (DNs) obtained from images, but soybean cultivar differences were statistically discernable (F=26, p=0.01). Spectroradiometer data are being analyzed to identify narrow spectral bands that might aid in selecting camera filters for determination of plant nitrogen status. Multiple camera configurations are proposed to allow vegetative indices to be developed more readily. Both remotely sensed field images and ground data are to be used for decision-making in a proposed variable-rate application system for agricultural aircraft. For this system, prescriptions generated from digital imagery and data will be coupled with GPS-based swath guidance and programmable flow control.

Thomson, Steven J.; Smith, Lowrey A.; Ray, Jeffrey D.; Zimba, Paul V.

2004-01-01

18

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

19

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.

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

2012-01-01

20

Evaluation of two detrending techniques for application in Heart Rate Variability  

Microsoft Academic Search

The performance of two different algorithms of detrending the RR-interval before Heart Rate Variability (HRV) analysis has been evaluated using both, simulated signals and real RR-interval time series. The first algorithm is based on the smoothness prior approach (SPA) and the second algorithm is implemented using wavelet packet (WP) analysis. The calculated time and frequency domain parameters obtained from real

K. Shafqat; S. K. Pal; P. A. Kyriacou

2007-01-01

21

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

22

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

PubMed

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

1999-12-01

23

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...

24

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

25

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

26

Evaluation of two detrending techniques for application in Heart Rate Variability.  

PubMed

The performance of two different algorithms of detrending the RR-interval before Heart Rate Variability (HRV) analysis has been evaluated using both, simulated signals and real RR-interval time series. The first algorithm is based on the Smoothness Prior Approach (SPA) and the second algorithm is implemented using Wavelet Packet (WP) analysis. The calculated time and frequency domain parameters obtained from real signals after detrending and the results obtained from simulated signals suggest that the WP method performed better than the SPA. The WP method provided more attenuation of the slow varying trend and was able to preserve the other signal components better than the SPA method. Also the SPA method was computationally slower and it might be not appropriate with long signals. PMID:18001941

Shafqat, K; Pal, S K; Kyriacou, P A

2007-01-01

27

An application of fractional differintegration to heart rate variability time series.  

PubMed

Fractional differintegration is used as a new tool to characterize heart rate variability time series. This paper proposes and focuses in two indexes (?c and fnQ) derived from the fractional differintegration operator. Both indexes are applied to fractional Gaussian noise (fGn) and actual RR time series in order to test their behavior. In the analysis of monofractal time series, ?c is linearly related with the Hurst exponent and the estimation of the exponent by the proposed index has lower variance than by using Detrended Fluctuation Analysis (DFA) or the periodogram. The other index fnQ quantifies how the time series adjust to a monofractal time series. Age, postural changes and paced breathing cause significant changes on fnQ while ?c only shows significant changes due to posture. In the analyzed actual HRV time series, ?c shows good correlation with the short term scaling exponent obtained by DFA, LF/HF and RMSSD while no correlations have been found for fnQ. PMID:23510605

García-González, Miguel A; Fernández-Chimeno, Mireya; Capdevila, Lluis; Parrado, Eva; Ramos-Castro, Juan

2013-03-16

28

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

Microsoft Academic Search

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

Leslie E. Papke; Jeffrey M. Wooldridge

1996-01-01

29

An endemic model with variable re-infection rate and applications to influenza.  

PubMed

An epidemic model is considered, where immunity is not absolute, but individuals that have recovered from the disease can be re-infected at a rate which depends on the time that has passed since their recovery (recovery age). Such a model, e.g., can account for the genetic drift in the influenza virus. In the special case that the model has no vital dynamics, there is no obvious disease-free equilibrium and so the model lacks the usual interplay between the basic replacement ratio being >1 and the disease-free equilibrium being unstable. In fact, this relatively simple model which combines ordinary differential equations with a transport equation shares with general structured population models the feature that the appropriate state space of the solution semiflow is a space of measures, here on the compacted right real half line, with the weak* topology. The disease-free equilibrium, in terms of recovered individuals, is then represented as a Dirac measure concentrated at infinity. Still it is difficult to linearize about it. This makes the concept of persistence very important, for one can show the following: if the basic replacement ratio is >1, the disease is uniformly strongly persistent, i.e., the number of infectives is ultimately bounded away from 0 with the bound not depending on the initial data. We also derive various conditions for the local and global stability of the endemic equilibrium in terms of the re-infection rate. For instance, the endemic equilibrium is likely to be locally asymptotically stable if the re-infection rate is a highly sub-homogeneous function of recovery age. Conversely, if the re-infection rate is a step function which is zero at small recovery age, the endemic equilibrium can be unstable. PMID:12387924

Thieme, Horst R; Yang, Jinling

30

Determinants of heart rate variability during deep breathing: Basic findings and clinical applications  

Microsoft Academic Search

The measurement of heart rate variation during forced breathing (HRDB) is a well-known clinical test of parasympathetic function. It is known that normal values of HRDB are strongly dependent on age. However, little is known about other physiological factors that may lead to reduced HRDB values that may mimic parasympathetic failure. Thirty-two normal subjects (age 56.7±12.4 years) and 32 neurological

R. R. Diehl; D. Linden; P. Berlit

1997-01-01

31

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...

32

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

33

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 ...

34

Are evolutionary rates really variable?  

Microsoft Academic Search

Summary Langley and Fitch (1974, 1976) have shown that the pattern of nucleotide substitutions in proteins is inconsistent with a Poisson process with constant rate. From this they conclude that the rate is temporally heterogeneous. It is pointed out in this note that a process which is temporally homogeneous but not a Poisson process is compatible with the data if

John H. Gillespie; Charles H. Langley

1979-01-01

35

Connecting Variability in Global Transcription Rate to Mitochondrial Variability  

PubMed Central

Populations of genetically identical eukaryotic cells show significant cell-to-cell variability in gene expression. However, we lack a good understanding of the origins of this variation. We have found marked cell-to-cell variability in average cellular rates of transcription. We also found marked cell-to-cell variability in the amount of cellular mitochondrial mass. We undertook fusion studies that suggested that variability in transcription rate depends on small diffusible factors. Following this, in vitro studies showed that transcription rate has a sensitive dependence on [ATP] but not on the concentration of other nucleotide triphosphates (NTPs). Further experiments that perturbed populations by changing nutrient levels and available [ATP] suggested this connection holds in vivo. We found evidence that cells with higher mitochondrial mass, or higher total membrane potential, have a faster rate of transcription per unit volume of nuclear material. We also found evidence that transcription rate variability is substantially modulated by the presence of anti- or prooxidants. Daughter studies showed that a cause of variability in mitochondrial content is apparently stochastic segregation of mitochondria at division. We conclude by noting that daughters that stochastically inherit a lower mitochondrial mass than their sisters have relatively longer cell cycles. Our findings reveal a link between variability in energy metabolism and variability in transcription rate.

das Neves, Ricardo Pires; Jones, Nick S.; Andreu, Lorena; Gupta, Rajeev; Enver, Tariq; Iborra, Francisco J.

2010-01-01

36

Heart Rate Variability in Heart Failure  

Microsoft Academic Search

The autonomic nervous system has an important role in the development and progression of the heart failure syndrome. Increased sympathetic, reduced parasympathetic, and impaired baroreceptor activity are well-documented features of heart failure. The analysis of heart rate variability can give insight into these autonomic abnormalities. A number of techniques now exist for assessing heart rate variability, and in general they

John E. Sanderson

1998-01-01

37

Instantaneous monitoring of heart rate variability  

Microsoft Academic Search

Most of the currently accepted approaches to compute heart rate and assess heart rate variability operate on interpolated, continuous-valued heart rate signals, thereby ignoring the underlying discrete structure of human heart beats. To overcome this limitation, we model the stochastic structure of heart beat intervals as a history-dependent, inverse Gaussian process and derive from it an explicit probability density describing

R. Barbieri; E. C. Matten; E. N. Brown

2003-01-01

38

Increased heart rate variability during nondirective meditation  

Microsoft Academic Search

Purpose: Meditation practices are in use for relaxation and stress reduction. Some studies indicate beneficial cardiovascular health effects of meditation. The effects on the autonomous nervous system seem to vary among techniques. The purpose of the present study was to identify autonomic nerve activity changes during nondirective meditation.Materials and methods: Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex

Anders Nesvold; Morten W Fagerland; Svend Davanger; Øyvind Ellingsen; Erik E Solberg; Are Holen; Knut Sevre; Dan Atar

2012-01-01

39

Heart Rate Variability Biofeedback for Major Depression  

Microsoft Academic Search

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

Maria Karavidas

40

Heart rate and heart rate variability, a pharmacological target  

Microsoft Academic Search

Heart rate varies with respiration, blood pressure, emotion, etc., and heart rate variability (HRV) is presently one of the best indices to predict fatal issues in cardiac failure and after myocardial infarction. HRV depends on various reflexes. In addition, parallel studies of HRV and the myocardial adrenergic and muscarinic transduction system in experimental models of cardiac hypertrophy (CH) have suggested

Bernard Swynghedauw; Sylvain Jassonfl; Brigitte Chevalierfl; Jean Clairambault; Sandrine Hardouinfl; Christophe Heymesfl; Laurence Mangin; Pascale Manster; Claire Médigue; Jean-Marie Moalic; Nancy Thibault; François Carré

1997-01-01

41

Heart rate variability in brain death  

Microsoft Academic Search

The sensitivity and specificity of heart rate variability (HRV) in the corroboration of brain death diagnosis in patients with acute traumatic intracranial lesions was evaluated in 20 patients with clinical criteria of brain death, nine patients in deep coma (Glasgow scale

J. Freitas; J. Puig; A. P. Rocha; P. Lago; J. Teixeira; M. J. Carvalho; O. Costa; A. Falcão de Freitas

1996-01-01

42

Heart rate variability and familial amyloidosis  

Microsoft Academic Search

A 32-year-old man with family history of amyloidosis was admitted to the hospital because of orthostatic hypotension. An echocardiogram was suggestive for cardiac amyloidosis. Heart rate variability analysis, performed on 24-h Holter monitoring, showed markedly low values in both frequency and time domain, reflecting a severe autonomic nervous system dysfunction.

Sergio Morelli; Enrico Carmenini; Alessandro Sgreccia; Ada Francia

2002-01-01

43

Continuously-variable rate pulse combustion apparatus  

Microsoft Academic Search

This patent describes continuously-variable rate pulse combustion apparatus. It comprises: a main burner; a primary burner; main fuel supply means; primary fuel supply means; main air supply means; primary air supply means; combustion chamber means; exhaust means; inlet air decoupling means; main inlet air means; primary inlet air means; and main valve means.

W. H. Thrasher; G. J. Wells

1991-01-01

44

A new heart rate variability-based method for the estimation of oxygen consumption without individual laboratory calibration: Application example on postal workers  

Microsoft Academic Search

Traditionally, the estimation of oxygen consumption (VO2) at work using heart rate (HR) has required the determination of individual HR\\/VO2 calibration curves in a separate exercise test in a laboratory (VO2-TRAD). Recently, a new neural network-, and heart rate variability-based method has been developed (Firstbeat PRO heartbeat analysis software) for the estimation of VO2 without individual calibration (VO2-HRV). In the

Juhani Smolander; Tanja Juuti; Marja-Liisa Kinnunen; Kari Laine; Veikko Louhevaara; Kaisa Männikkö; Heikki Rusko

2008-01-01

45

Changes in heart rate variability during fainting.  

PubMed

Studies of heart rate variability in people who faint may yield insights into normal physiologic mechanisms which probably are dynamic. These insights might be gained because fainting appears to be due to a breakdown of these mechanisms. Tilt table testing reliably induces fainting in patients with a history of fainting and can be used to study these mechanisms. During tilt tests ending in fainting heart rate changes markedly, with a loss of high-frequency components on power spectral analysis and a progressive slowing of overall sinus node discharge. These changes appear to be due to changes in efferent vagal nerve traffic. Several possible mechanisms of these changes in heart rate variability are discussed. PMID:12779923

Sheldon, Robert; Riff, Kenneth

1991-10-01

46

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.

Costa, Tommaso; Boccignone, Giuseppe; Ferraro, Mario

2012-01-01

47

Evaluation of a Variable Rate Irrigating Hill-Seeder  

Technology Transfer Automated Retrieval System (TEKTRAN)

A variable rate irrigating hill-seeder is a drought-alleviating and water-saving agricultural machine that can adjust water application automatically according to the soil moisture content and realize the synchronization between water and seeds through photoelectric-detecting technology. The objecti...

48

Vaginal Intercourse Frequency and Heart Rate Variability  

Microsoft Academic Search

We examined the relationship between recalled and diary recorded frequency of penile-vaginal intercourse (FSI) and both resting heart rate variability (HRV; an index of cardiac autonomic control and parasympathetic tone associated with cardiovascular health outcomes) and resting diastolic blood pressure (DBP) in 120 healthy adults aged 19-38 (subjects scoring above the 87th percentile on the Lie scale of the Eysenck

STUART BRODY; RAGNAR PREUT

2003-01-01

49

Heart rate variability and intima media thickness  

Microsoft Academic Search

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

Nanna Hurwitz Eller; Birgitta Malmberg; Peter Bruhn

2006-01-01

50

H 2 Blocker modulates heart rate variability  

Microsoft Academic Search

Summary  The use of H2-blockers in the treatment of patients with peptic ulcer has become popular. However, this treatment has adverse cardiovascular\\u000a effects. The aim of this study was to investigate proarrhythmic rhythm and autonomic nervous activity by analyzing heart rate\\u000a variability in patients treated with omeprazole, ranitidine, and plaunotol. Nineteen patients (mean age 67.5 ± 2.7 years)\\u000a with active gastric

Tatsuhiko Ooie; Tetsunori Saikawa; Masahide Hara; Hidenobu Ono; Masataka Seike; Toshiie Sakata

1999-01-01

51

Variability of Recombination Rates in Higher Plants  

Microsoft Academic Search

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

Elisabeth Esch; Renate Horn

52

Air Pollution and Heart Rate Variability  

PubMed Central

Background Outdoor air pollution and lead exposure can disturb cardiac autonomic function, but the effects of both these exposures together have not been studied. Methods We examined whether higher cumulative lead exposures, as measured by bone lead, modified cross-sectional associations between air pollution and heart rate variability among 384 elderly men from the Normative Aging Study. We used linear regression, controlling for clinical, demographic, and environmental covariates. Results We found graded, significant reductions in both high-frequency and low-frequency powers of heart rate variability in relation to ozone and sulfate across the quartiles of tibia lead. Interquartile range increases in ozone and sulfate were associated respectively, with 38% decrease (95% confidence interval = -54.6% to -14.9%) and 22% decrease (-40.4% to 1.6%) in high frequency, and 38% decrease (-51.9% to -20.4%) and 12% decrease (-28.6% to 9.3%) in low frequency, in the highest quartile of tibia lead after controlling for potential confounders. We observed similar but weaker effect modification by tibia lead adjusted for education and cumulative traffic (residuals of the regression of tibia lead on education and cumulative traffic). Patella lead modified only the ozone effect on heart rate variability. Conclusions People with long-term exposure to higher levels of lead may be more sensitive to cardiac autonomic dysfunction on high air pollution days. Efforts to understand how environmental exposures affect the health of an aging population should consider both current levels of pollution and history of lead exposure as susceptibility factors.

Park, Sung Kyun; O'Neill, Marie S.; Vokonas, Pantel S.; Sparrow, David; Wright, Robert O.; Coull, Brent; Nie, Huiling; Hu, Howard; Schwartz, Joel

2009-01-01

53

Applications of Reaction Rate  

ERIC Educational Resources Information Center

|This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why…

Cunningham, Kevin

2007-01-01

54

Applications of Reaction Rate  

ERIC Educational Resources Information Center

This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

Cunningham, Kevin

2007-01-01

55

Vaginal intercourse frequency and heart rate variability.  

PubMed

We examined the relationship between recalled and diary recorded frequency of penile-vaginal intercourse (FSI) and both resting heart rate variability (HRV; an index of cardiac autonomic control and parasympathetic tone associated with cardiovascular health outcomes) and resting diastolic blood pressure (DBP) in 120 healthy adults aged 19-38 (subjects scoring above the 87th percentile on the Lie scale of the Eysenck Personality Inventory were excluded from analyses). As in a previous smaller study, greater HRV was associated with greater FSI (but not masturbation or non-coital sex with a partner) and rated importance of intercourse. There were no sex differences in the HRV-FSI relationship, and the relationship was not explained by including measures of Extraversion, Neuroticism, Depression, Trait Anxiety, or partnership satisfaction. However, the previously obtained negative association of FSI with DBP was not replicated. PMID:14504008

Brody, Stuart; Preut, Ragnar

56

A variable-rate filtering system for digital communications  

Microsoft Academic Search

We propose an efficient programmable transmit-receive digital filter structure consisting of a pulse shaping filter (PSF) and a cascaded integrator-comb (CIC) filter which is applicable to variable-rate digital communication systems. The CIC structure is a hardware-efficient means of constructing programmable interpolation and decimation filters, but it introduces a large amount of intersymbol interference (ISI). We solve this problem by proposing

L. Wasserman

1999-01-01

57

Investigation of determinism in heart rate variability.  

PubMed

The article searches for the possible presence of determinism in heart rate variability (HRV) signals by using a new approach based on NARMA (nonlinear autoregressive moving average) modeling and free-run prediction. Thirty-three 256-point HRV time series obtained from Wistar rats submitted to different autonomic blockade protocols are considered, and a collection of surrogate data sets are generated from each one of them. These surrogate sequences are assumed to be nondeterministic and therefore they may not be predictable. The original HRV time series and related surrogates are submitted to NARMA modeling and prediction. Special attention has been paid to the problem of stationarity. The results consistently show that the surrogate data sets cannot be predicted better than the trivial predictor-the mean-while most of the HRV control sequences are predictable to a certain degree. This suggests that the normal HRV signals have a deterministic signature. The HRV time series derived from the autonomic blockade segments of the experimental protocols do not show the same predictability performance, albeit the physiological interpretation is not obvious. These results have important implications to the methodology of HRV analysis, indicating that techniques from nonlinear dynamics and deterministic chaos may be applied to elicit more information about the autonomic modulation of the cardiovascular activity. (c) 2000 American Institute of Physics. PMID:12779396

Gomes, M. E. D.; Souza, A. V. P.; Guimaraes, H. N.; Aguirre, L. A.

2000-06-01

58

Heart rate variability in the individual fetus.  

PubMed

The change in fetal heart rate and its variability (HRV) during the course of gestation has been documented by numerous studies. The overall drop in heart rate and increase in fetal HRV is associated with fetal growth in general and with the increase in neural integration in particular. The increased complexity of the demands on the cardiovascular system leads to more variation in the temporal course of the heart rate. Most studies that document and interpret these changes are based on data acquired in groups of fetuses. The aim of this work was to investigate HRV within single fetuses. We acquired 213 5min fetal magnetocardiograms in 11 fetuses during the second and third trimesters (at least 10 data sets per fetus, median 17). From the magnetocardiograms we determined the fetal RR interval time series and calculated the standard deviation (SDNN), root mean square of successive differences (RMSSD), approximate entropy (ApEn) and temporal asymmetry (Irrev). For each subject and HRV measure, we performed regression analysis with respect to gestational age, alone and in combination with RR interval. The coefficient of determination R(2) was used to estimate goodness-of-fit. The coefficient of quartile dispersion (CQD) was used to compare the regression parameters for each HRV measure. Overall, the HRV measures increased with age and RR interval. The consistency of the HRV measures within the individual fetuses was greater than in the data pooled over all fetuses. The individual R(2) for the model including age and RR interval was best for ApEn (.79, .59-.94; median, 90% CI), followed by RMSSD (.71, .25-.88), SDNN (.55, .18-.90) and Irrev (.16, .01-.39). These values, except for Irrev, were higher than those calculated over all 213 data sets (R(2)=.65, .63, .35, .28, respectively). The slopes of the regressions of each individual's data were most consistent over all subjects for ApEn, followed by RMSSD and SDNN and Irrev. Interindividually, the time domain measures showed discrepancies and the within-fetus courses were more consistent than the course over all fetuses. On the other hand, the course of ApEn during gestation was not only very consistent within each fetus but also very similar between most of subjects. Complexity measures such as ApEn may thus more consistently reflect prenatal developmental factors influencing cardiovascular regulation. PMID:23369622

Van Leeuwen, Peter; Cysarz, Dirk; Edelhäuser, Friedrich; Grönemeyer, Dietrich

2013-01-29

59

Climate variables as predictors of basal metabolic rate: new equations.  

PubMed

Estimation of basal metabolic rate (BMR) and daily energy expenditure (DEE) in living humans and in fossil hominins can be used to understand the way populations adapt to different environmental and nutritional circumstances. One variable that should be considered in such estimates is climate, which may influence between-population variation in BMR. Overall, populations living in warmer climates tend to have lower BMR than those living in colder climates, even after controlling for body size and composition. Current methods of estimating BMR ignore climate, or deal with its effects in an insufficient manner. This may affect studies that use the factorial method to estimate DEE from BMR, when BMR is not measured but predicted using an equation. The present meta-analysis of published BMR uses stepwise regression to investigate whether the inclusion of climate variables can produce a generally applicable model for human BMR. Regression results show that mean annual temperature and high heat index temperature have a significant effect on BMR, along with body size, age and sex. Based on the regression analysis, equations predicting BMR from body size and climate variables were derived and compared with existing equations. The new equations are generally more accurate and more consistent across climates than the older ones. Estimates of DEE in living and fossil humans using the new equations are compared with estimates using previously published equations, illustrating the utility of including climate variables in estimates of BMR. The new equations derived here may prove useful for future studies of human energy expenditure. PMID:18461599

Froehle, Andrew W

60

Variable frequency drive applications guide  

SciTech Connect

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

Laloudakis, D.J.

1991-10-01

61

Statistics for variable bit-rate digital television sources  

Microsoft Academic Search

Several categories of networks allow the users to transmit at variable bit-rates on their channels. DQDB and ATM networks can be mentioned as such examples. This paper will be concerned with describing the digital television and the high-definition television coders as variable bit-rate sources to be transmitted on ATM networks. The variable bit-rates will be studied and modeled bottom up,

J.-P. Leduc; P. Delogne

1996-01-01

62

Video Texture and Motion Based Modeling of Rate Variability-Distortion (VD) Curves  

Microsoft Academic Search

We examine and model the bit rate variability-distortion (VD) curve of -4 part 2 variable bit rate (VBR) video encodings. The VD curve has important applications for evaluating the statistical multiplexing of streaming video. We show that the concave VD curve shape at high compression ratios, or equivalently large quantization scales, is influenced by both the texture and the motion

Geert Van der Auwera; Martin Reisslein; Lina J. Karam

2007-01-01

63

Application of uncertainty and variability in LCA  

Microsoft Academic Search

As yet, the application of an uncertainty and variability analysis is not common practice in LCAs. A proper analysis will\\u000a be facilitated when it is clear which types of uncertainties and variabilities exist in LCAs and which tools are available\\u000a to deal with them. Therefore, a framework is developed to classify types of uncertainty and variability in LCAs. Uncertainty\\u000a is

Mark A. J. Huijbregts

1998-01-01

64

Sleep problems and heart rate variability over the working day.  

PubMed

The purpose of this study was to discover whether greater sleep problems are associated with reduced heart rate variability during working hours and at night, and to determine whether this association is in part mediated by experienced affective states. This study involved 199 working women with a mean age of 33.8years. Sleep problems were assessed with the Jenkins Sleep Problems Scale, and the Day Reconstruction Method was used to measure positive affect and stress on the evening before and during the working day. Heart rate variability was indexed by the mean square root of the successive standard difference in heart period. Disturbed sleep was inversely related to heart rate variability during the working day (P=0.022), independently of demographic and behavioural confounders. Additional adjustment for positive affect and stress did not lead to further reductions in the association between sleep problems and reduced heart rate variability over the work day. Sleep problems were not predictive of reduced night-time heart rate variability. This report extends the findings from experimental studies and clinical samples, and suggests that disturbed sleep might impair heart rate variability in real life settings, in particular during working hours. Reduced heart rate variability might be a potential pathway linking sleep problems with cardiovascular disease. Based on the current data there was little evidence that the inverse associations between sleep problems and heart rate variability were mediated by experienced affective states. PMID:22309485

Jackowska, Marta; Dockray, Samantha; Endrighi, Romano; Hendrickx, Hilde; Steptoe, Andrew

2012-02-07

65

Predicting interannual variability in evapotranspiration rates  

NASA Astrophysics Data System (ADS)

The amount of evapotranspiration (ET), the sum of all the water that evaporates from the surface or is drawn up through plants and vented as vapor, is a strong controlling factor for the amount of water left over for other purposes, such as groundwater recharge or surface runoff. Understanding how ET rates vary from year to year is challenging, because the change is inherently controlled by small-scale variations in vegetation type and density, soil properties, and meteorological conditions. Yet there has been some success understanding variations in ET at the watershed scale. Analyzing daily measurements of evapotranspiration for 547 watersheds across the United States from 1983 to 2006, Cheng et al. identified a strong linear relationship between two slightly different ratios: the ratio between the watershed's potential evapotranspiration (PET) and precipitation and that between observed ET and precipitation. This is surprising because many previous studies suggested a nonlinear relationship between the two ratios by following the Budyko framework, a dominant approach in water cycle modeling that relates ET rates to the amount of energy and water in the system.

Schultz, Colin

2011-11-01

66

Average heart rate, heart rate variability and the sympathovagal balance  

Microsoft Academic Search

Investigated are the responses of the average heart rate and of the balance between the 0.07-0.14 and 0.14-0.40-Hz components of the heart power spectrum to gravitational stress. This was done by taking finger blood pressure measurements in 18 young normals during two 1-hour sessions. In each session there were two supine-standing and two standing-supine transitions. For each transition the changes

Marc J. A. Janssen; Cees A. Swenne; Johan de Bie; Volkert Manger Cats; Albert V. G. Bruschke

1990-01-01

67

Comparative analysis of variables to measure recovery rates in streams  

SciTech Connect

The authors assessed a series of chemical and biological variables for their abilities and cost effectiveness in determining recovery rates in streams. Using data gathered at the experimental streams of the Monticello Ecological Research Station, several water-quality variables (DO, pH, nutrients), macroinvertebrate densities, macrophyte biomass, and periphyton biomass, and several ecosystem-level variable (e.g., primary production) were compiled and analyzed. Water-quality variables were relatively inexpensive to measure, and many would be relatively easily collected for assessing recovery rates; however, their overall explanatory power for determining recovery of streams, especially biological phenomena, was limited. Several biological variables, including gross primary production, respiration, leaf litter decomposition rates, macroinvertebrate richness, and Collembola density, could be measured reasonably well and required relatively small sample sizes for detecting recovery rates. However, collection of most of these variables was more costly than collection of chemical water-quality variables. The ultimate determination of which variables to measure in assessing recovery in a given ecosystem will need to be based on the disturbances being examined, the importance of the variables to stream health, and the available monetary resources. Generally, comprehensive analyses of recovery rates for a variety of aquatic systems will greatly increase their ability to develop a framework for predicting recovery rates and ultimately improving the quality of the environment.

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

1993-09-01

68

Changes in Respiratory Rate, Blood Pressure and Heart Rate Variability in Rabbits during Orthostasis  

Microsoft Academic Search

Mokr? J, T. RemeÀová, K. Javorka: Changes in Respiratory Rate, Blood Pressure and Heart Rate Variability in Rabbits during Orthostasis. Acta Vet. Brno 2006, 75: 3-12. The purpose of the study was to evaluate the changes of respiratory rate, systemic blood pressure and heart rate variability parameters (HRV) during orthostasis in anaesthetized rabbits. Furthermore, these changes were influenced by affecting

J. Mokrý; T. Reme?ová; K. Javorka

2006-01-01

69

Analysis of heart rate variability using fuzzy measure entropy.  

PubMed

This paper proposed a new entropy measure, Fuzzy Measure Entropy (FuzzyMEn), for the analysis of heart rate variability (HRV) signals. FuzzyMEn was calculated based on the fuzzy set theory and improved the poor statistical stability in the approximate entropy (ApEn) and sample entropy (SampEn). The simulation results also demonstrated that the FuzzyMEn had better algorithm discrimination ability when compared with the recently published fuzzy entropy (FuzzyEn), The validity of FuzzyMEn was tested for clinical HRV analysis on 120 subjects (60 heart failure and 60 healthy control subjects). It is concluded that FuzzyMEn could be considered as a valid and reliable method for a clinical HRV application. PMID:23273774

Liu, Chengyu; Li, Ke; Zhao, Lina; Liu, Feng; Zheng, Dingchang; Liu, Changchun; Liu, Shutang

2012-12-27

70

An electronic flow control system for a variable-rate tree sprayer  

Technology Transfer Automated Retrieval System (TEKTRAN)

Precise modulation of nozzle flow rates is a critical measure to achieve variable-rate spray applications. An electronic flow rate control system accommodating with microprocessors and pulse width modulation (PWM) controlled solenoid valves was designed to manipulate the output of spray nozzles inde...

71

Impact of Exchange Rate Variability on International Trade Flows.  

National Technical Information Service (NTIS)

The paper investigates how exchange rate variability and risk has affected the price and volume of UK exports of manufactures in the floating rate period. Consideration is given to the definition of exchange rate volatility relevant to UK trade flows. (Co...

G. Justice

1983-01-01

72

Reduced heart rate variability following repair of tetralogy of Fallot  

PubMed Central

OBJECTIVE—To examine autonomic function as assessed by heart rate variability in patients 10 or more years after repair of tetralogy of Fallot, and to relate this to cardiac structure, function, and electrocardiographic indices.?METHODS—Heart rate variability was measured by standard time domain techniques on a 24 hour Holter ECG in 28 patients, aged 12 to 34 years (mean 19.5), who had undergone repair of tetralogy of Fallot at least 10 years previously. Echocardiography was performed to assess left ventricular size and function, right ventricular size and pressure, and any proximal pulmonary arterial stenosis. Right ventricular function was evaluated by radionuclide scan. QRS duration, QT interval, and QT dispersion were measured on a standard 12 lead ECG. Measurements of heart rate variability were compared with values from 28 age matched healthy controls (mean age 19.9 years). Interrelations between variables were assessed using Pearson correlation coefficients and stepwise regression analysis.?RESULTS—Heart rate variability was reduced, compared with values for age matched normal controls, in 12 of the 28 patients. Reduced heart rate variability was associated with increased age, increased right ventricular size and pressure, and widening of the QRS complex.?CONCLUSIONS—Reduced heart rate variability is a feature following repair of tetralogy of Fallot. It is associated with increasing age, impaired right ventricular haemodynamics, and widening of the QRS complex. Under these circumstances, reduced heart rate variability may be a marker for deteriorating right ventricular function. Increased QRS duration has been identified as a risk factor for sudden death following repair of tetralogy of Fallot, and impaired cardiac autonomic control may be one of the mechanisms involved.???Keywords: tetralogy of Fallot; heart rate variability; right ventricular function; congenital heart disease

McLeod, K; Hillis, W; Houston, A; Wilson, N; Trainer, A; Neilson, J; Doig, W

1999-01-01

73

Variable Rate Irrigation Management for Humid Climates Using a Conventional Center Pivot System  

Technology Transfer Automated Retrieval System (TEKTRAN)

This study investigates suitability of a standard commercial center pivot system for variable-rate water application under Mid-South conditions. The objective was to determine if field variability data can be applied to conventional moving sprinkler systems to optimize irrigation management on non-u...

74

Heart rate conditioning in newborn infants: Relationships among conditionability, heart rate variability, and sex  

Microsoft Academic Search

Evaluated trace conditioning in 20 newborn infants by examining heart rate responses to the conditioned stimulus (CS), in anticipation of the unconditioned stimulus (UCS) and in the absence of the UCS. 2 sets of analyses were performed using subgroups based on preexperimental heart rate variability and sex. Preexperimental heart rate variability was related only to the response to the CS,

Leighton E. Stamps; Stephen W. Porges

1975-01-01

75

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

76

Heart rate variability in depressive and anxiety disorders  

Microsoft Academic Search

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

Jack M. Gorman; Richard P. Sloan

2000-01-01

77

Heart Rate Variability as a Predictor of Speaking Anxiety  

Microsoft Academic Search

This study examines the relations among the perception of speaking anxiety and difficulties in emotion regulation with 2 measures of physiological activity: heart rate (HR) and heart rate variability (HRV). Results show significant changes in HR and state anxiety, but not HRV, among the 6 experimental conditions: quiet, reading in both sitting and standing positions, and speaking in both sitting

Valerie A. MacIntyre; Peter D. MacIntyre; Geoff Carre

2010-01-01

78

A monitoring device for continuous analysis of heart rate variability  

Microsoft Academic Search

A computer based system for bedside investigation of the autonomic nervous system (ANS) using spectral analysis of heart rate variability (HRV) is described. Primary information, electrocardiogram (ECG) signal, is obtained from a classical cardiotachymeter which is the interface between the patient and the device. A special software has been designed to continuously acquire the ECG samples, build the heart rate

U. Shim; A. Kumarakrishnan; S. B. Cahn; T. Sleator

1997-01-01

79

An age extended progress variable for conditioning reaction rates  

Microsoft Academic Search

An aging progress variable (APV) is proposed as a convenient tool for conditioning quantities used to calculate reaction rates in premixed turbulent combustion. The APV is defined to obey an advection-diffusion-reaction equation where the source term is linearly related to the fuel consumption rate when the APV is less than a threshold representative of the trailing edge of the fuel

R. W. Grout

2007-01-01

80

Heart rate variability related to effort at work  

Microsoft Academic Search

Changes in autonomic nervous system function have been related to work stress induced increases in cardiovascular morbidity and mortality. Our purpose was to examine whether various heart rate variability (HRV) measures and new HRV-based relaxation measures are related to self-reported chronic work stress and daily emotions. The relaxation measures are based on neural network modelling of individual baseline heart rate

Arja Uusitalo; Terhi Mets; Kaisu Martinmäki; Saija Mauno; Ulla Kinnunen; Heikki Rusko

2011-01-01

81

Effect of interscalene brachial plexus block on heart rate variability  

PubMed Central

Background Interscalene brachial plexus block (ISB) may be followed by cardiovascular instability. Until date, there is no clear picture available about the underlying mechanisms of ISB. In this study, we aimed to determine the changes in heart rate variability (HRV) parameters after ISB and the differences between right- and left-sided ISBs. Methods We prospectively studied 24 patients operated for shoulder surgery in sitting position and divided them into two respective groups: R (right-sided block = 14 pts) and L (left-sided block = 10 pts). HRV data were taken before and 30 min after the block. Ropivacaine without ephedrine was used for the ISB through an insulated block needle connected to a nerve stimulator. Statistical analysis implemented chi-square, Student's and t-paired tests. Skewed distributions were analyzed after logarithmic transformation. Results All the studied patients had successful blocks. Horner's syndrome signs were observed in 33.3% of the patients (R = 5/14, L = 3/10; [P = 0.769]). There were no significant differences in pre-block HRV between the groups. The application of ISB had differential effect on HRV variables: R-blocks increased QRS and QTc durations and InPNN50, while a statistical decrease was seen in InLF. L-blocks did not show any significant changes. These changes indicate a reduced sympathetic and an increased parasympathetic influence on the heart's autonomic flow after R-block. Conclusions Based on the obtained results we conclude that ISB, possibly through extension of block to the ipsilateral stellate ganglion, alters the autonomic outflow to the central circulatory system in a way depending on the block's side.

Simeoforidou, Marina; Chantzi, Eleni; Bareka, Metaxia; Tsiaka, Katerina; Iatrou, Christos; Karachalios, Theophilos

2013-01-01

82

Reproducibility of heart rate variability and blood pressure variability in individuals with spinal cord injury  

Microsoft Academic Search

Individuals with spinal cord injury (SCI) are prone to orthostatic intolerance and an increased risk of cardiovascular disease. The use of heart rate variability (HRV) and blood pressure variability (BPV) as indices of cardiovascular regulation would be valuable in this population; however, their reproducibility has yet to be tested in those with SCI. The purpose of this study was to

David S. Ditor; Mark V. Kamath; Maureen J. MacDonald; Joanne Bugaresti; Neil McCartney; Audrey L. Hicks

2005-01-01

83

Relationship of Heart Rate Variability to Parasympathetic Effect  

Microsoft Academic Search

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

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

2010-01-01

84

Changes in Heart Rate Variability in patients under local anesthesia.  

PubMed

Spectral analysis of Heart Rate Variability (HRV) is widely used for the assessment of cardiovascular autonomic control. Several studies have shown the effect of anesthetic agents on HRV parameters. In this study a systematic approach of HRV analysis has been employed. The effect caused by the ectopic beats on the spectral measurements has been investigated and results are presented. A detrending method using Wavelet Packets has been developed which was able to remove slow varying trend from HRV signals without causing significant changes in the low frequency (LF) and high frequency (HF) component of the HRV signal. Using this methodology electrocardiogram (ECG) signals from 14 patients undergoing local anesthesia (brachial plexus block) were analyzed with parametric Autoregressive (AR) method. The results showed that the LF/HF ratio values calculated from the HRV signal decreases within an hour of the application of the brachial plexus block compared to the values at the start of the procedure. This change was noticed in approximately 80% of the patients. PMID:18001949

Shafqat, K; Pal, S K; Kumari, S; Kyriacou, P A

2007-01-01

85

Heart rate variability exhibits complication-dependent changes postsurgery.  

PubMed

"Surgical stress response" is tissue damage postsurgery, leading to a systemic response (inflammation, sympathetic upregulation, and release of vasoactive chemicals), which is typically measured by C-reactive protein (CRP). We assessed arterial stiffness and heart rate variability (HRV)-additional parameters reflecting autonomic and vascular functions-in this response and their potential associations with postoperative complications. In 47 participants undergoing abdominal surgery, CRP, arterial stiffness, and HRV were measured pre- and postoperatively (days 1 and 2). C-reactive protein was significantly higher postoperatively in participants experiencing complications but not preoperatively. Compared to participants without complications, those with complications had increased HRV and pnn50 (time domain) and tendency toward increasing low-frequency/high-frequency ratio (frequency domain) on postoperative day 2. Therefore, time and frequency domain HRV parameters show perioperative changes in relation to complication development. These findings suggest the applicability of this noninvasive technology to a variety of abdominal operations. Larger studies need to confirm these findings. PMID:23091271

Scheffler, Patrick; Muccio, Salvatore; Egiziano, Giordano; Doonan, Robert J; Yu, Alice; Carli, Franco; Daskalopoulou, Stella S

2012-10-21

86

The relationship between advertisement variables and applicant responses to newspaper recruitment advertisements  

Microsoft Academic Search

The relationship between recruitment advertisement variables and applicant response rate was investigated. Three hundred and fifty companies were surveyed about applicant responses to their classified advertisements. One hundred and thirty-three surveys were completed and sent back for a return rate of 38%. The results of this study indicate that advertisements which include variables to enhance the physical features of the

Amy B. Kaplan; Michael G. Aamodt; Doreen Wilk

1991-01-01

87

The accuracy of soil map for variable rate phosphorus fertilisation  

NASA Astrophysics Data System (ADS)

The basic concept of precision agriculture is to match the input and field requirement. The Variable rate (VR) fertilisation technique allows the ability to vary the rate of fertiliser application based on the field information, normally using field maps. In VR phosphorus fertilisation, field map is developed using grid soil sampling and soil P analysis. The objective of this study is to investigate how many samples are basically required to develop an accurate map. Fresh samples collected from 0.1 - 0.2 m depth of arable fields and grassland from three different fields and were subject to chemical analyses for soil P using two methods, Olsen P and extractable ammonium lactate P. The coordinates of each sample was located by a DGPS (Trimble® AgDGPS 132, USA) and converted into Lambert 72 coordinates to have the distance in the metric system. The result of each P analysis was put against its coordinates. Out of all sample records in each field (100 % of the data) 75, 50, 25 and 10% of the sample records were randomly selected and was used to develop field P map. The Surfer 8.00 (Golden Software) software was used to draw the maps using the Kriging method. Comparison of soil P maps showed a considerable difference while the number of samples used for map development is decreasing. However, there is a degree of similarity between maps using more soil samples. This means for developing an accurate map for precision agriculture it is not necessary to collect a massive sample sets.

Maleki, M. R.; de Baerdemaeker, J.

2009-04-01

88

Heart Rate and Blood Pressure Variability: Implications for Psychiatric Research  

Microsoft Academic Search

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

Vikram K. Yeragani

1995-01-01

89

Age and Heart Rate Variability After Soccer Games  

Microsoft Academic Search

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

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

2010-01-01

90

Water Requirements and Application Rates for Lawns.  

National Technical Information Service (NTIS)

Lawn water application rates were measured for 55 homes in Laramie and Wheatland, Wyoming, during 1975 and 1976. In addition, evapotranspiration rates were measured at both cities during 1976. Lawn water application rates in 1976 were 122 percent of the a...

L. O. Pochop J. Borrelli J. R. Barnes P. K. O'Neill

1978-01-01

91

Changes in Heart Rate Variability in Patients under Local Anesthesia  

Microsoft Academic Search

Spectral analysis of Heart Rate Variability (HRV) is widely used for the assessment of cardiovascular autonomic control. Several studies have shown the effect of anesthetic agents on HRV parameters. In this study a systematic approach of HRV analysis has been employed. The effect caused by the ectopic beats on the spectral measurements has been investigated and results are presented. A

K. Shafqat; S. K. Pal; S. Kumari; P. A. Kyriacou

2007-01-01

92

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

93

Variability in Schools' Suspension Rates of Black Students  

ERIC Educational Resources Information Center

Black students are frequently suspended at much higher rates than students from other races or ethnicities. Analyses of suspension data over a three-year period were conducted to explain between-school variability in the percentages of Black students suspended in secondary schools at a large urban school district. Results of hierarchical backward…

Arcia, Emily

2007-01-01

94

Depression, heart rate variability, and exercise training in dialysis patients  

Microsoft Academic Search

Background Functional limitations, altered cardiac autonomic activity, and psychological distress are known disorders in chronic hemodialysis (HD) patients, relating to increased morbidity and mortality. The aim of this study was to examine the influence of an exercise training program on emotional parameters and heart rate variability (HRV) indices, as well as to determine whether emotional stress contributes to autonomic dysfunction

Evangelia Kouidi; Vassilis Karagiannis; Dimitrios Grekas; Apostolos Iakovides; George Kaprinis; Achilleas Tourkantonis; Asterios Deligiannis

2010-01-01

95

Relationship between major depression and heart rate variability  

Microsoft Academic Search

A high sympathetic and\\/or a low cardiovagal activity in patients with major depression (MD) may contribute to the higher cardiac morbidity and mortality of MD patients. Standardized tests of heart rate variability (HRV) allow a quantitative estimation of autonomic nervous system function. However, previous studies on the relationship between HRV and MD have revealed conflicting results. Our study compared time

Marcus W Agelink; Cavit Boz; Heiko Ullrich; Jürgen Andrich

2002-01-01

96

Power Spectral Analysis of Heart Rate Variability in Psychiatry  

Microsoft Academic Search

Power spectrum analysis of heart rate variability (PSA of HRV) is a promising method, which can be used as an index of cardiac autonomic balance. PSA of HRV is a noninvasive technique, based on ECG sampling of RR interval variation, thus providing a dynamic assessment of sympathetic and parasympathetic tone, reflecting the interactions between the two. It has been shown

Hagit Cohen; Michael A. Matar; Zeev Kaplan; Moshe Kotler

1999-01-01

97

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...

98

Depression, Heart Rate Variability, and Acute Myocardial Infarction  

Microsoft Academic Search

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

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

99

Heart rate variability is altered following spinal cord injury  

Microsoft Academic Search

Spinal cord injury (SCI) patients are know to suffer from autonomic failure as a result of their injury. The magnitude of the dysautonomia resulting from such an injury is difficult to predict or characterize and, in varying degree, it impedes the recovery of physiological homeostasis. This study is intended to investigate the effectiveness of heart rate variability (HRV) analysis as

David C. Bunten; Alberta L. Warner; Sherry R. Brunnemann; Jack L. Segal

1998-01-01

100

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...

101

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

102

Heart Rate Variability on Exposure to Severe Gold at Antarctica  

Microsoft Academic Search

An attempt has been made to evaluate Heart Rate Variability (HRV) as a reliable index for sympathetic and parasympathetic components of the autonomic nervous system response during the course of acclimatization to severe cold at Antarctica. Two groups (10 each) of healthy men in the age group of 2344 years participated in the study. Group A consisted of fresh inductees

K. Harinath; A. S. Malhotra; Karan Pal; R. Prasad; R. C. Sawhney

103

How to interpret psychology from heart rate variability?  

Microsoft Academic Search

In this paper, we have used the color stimuli to define the arousal level of subjects by analyzing their heart rate variability (HRV). For this analysis, we have used the novel Triangular Phase Space Mapping (TPSM) and try to distinguish two groups of emotions, calm and energetic. The results show that cold colors are associated with low arousal level and

Sadaf Moharreri; Nader Jafarnia Dabanloo; Saman Parvaneh; Ali M Nasrabadi

2011-01-01

104

Alteration of Heart Rate Variability Parameters in Nondiabetic Hemodialysis Patients  

Microsoft Academic Search

Objective: We attempt to identify heart rate variability (HRV) components and decide whether or not such components are more sensitive to the hemodialysis (HD) process by excluding the presence of comorbid conditions known to affect HRV. Methods: It was a prospective cohort study of factors associated with HRV. Thirty-five HD patients were admitted to the study. The research was divided

Yan-Qing Tong; Huo-Ming Hou

2007-01-01

105

Circadian Rhythms of Spectral Components of Heart Rate Variability  

Microsoft Academic Search

Circadian rhythms of heart rate variability have been widely studied in recent years. However, most previous reports described such rhythms in terms of normalized units of the low- and high-frequency (LF and HF) spectral components. In this study, we analyzed circadian rhythms of spectral components in absolute units and found unexpected results in normal subjects as well as coronary heart

G. Q. Wu; L. L. Shen; D. K. Tang; D. A. Zheng; C.-S. Poon

2006-01-01

106

Acupuncture and heart rate variability: A systematic review  

Microsoft Academic Search

Acupuncture has been reported to affect the autonomic system. Currently, there are no systematic reviews examining the effect of acupuncture on HRV available in the literature. Therefore, the aim of this systematic review was to summarize and critically assess the effects of acupuncture on heart rate variability. We searched the literature using 14 databases for articles published from the earliest

Sanghoon Lee; Myeong Soo Lee; Jun-Yong Choi; Seung-Won Lee; Sang-Yong Jeong; Edzard Ernst

2010-01-01

107

Acute Effect of Cigarette Smoking on Heart Rate Variability  

Microsoft Academic Search

Acute cigarette smoking enhances adrenergic activity and thus may be associated with hemodynamic changes in the cardiovascular system. In this study, the acute effect of cigarette smoking on heart rate variability (HRV) was studied. Fifteen subjects were included in the study. Time domain (the mean R-R interval, the standard deviation of R-R interval, and the root mean square of successive

Osman Karakaya; Irfan Barutcu; Dayimi Kaya; Ali Metin Esen; Mustafa Saglam; Mehmet Melek; Ersel Onrat; Muhsin Turkmen; Ozlem Batukan Esen; Cihangir Kaymaz

2007-01-01

108

The Effect of Colored Illumination on Heart Rate Variability  

Microsoft Academic Search

We investigated the effects of illumination with colored fluorescent light on heart rate variability (HRV) and autonomic regulation. Previous examinations have only focused on full-spectrum fluorescent bright light as it is used for the therapy of seasonal affective disorder and disturbances of circadian rhythms. Materials and Methods: In 3 experiments, 12 healthy volunteers were exposed for 10 min to red,

Axel Schäfer; Karl W. Kratky

2006-01-01

109

Suicide rates, handgun control laws, and sociodemographic variables.  

PubMed

The association of state handgun control laws to state suicide rates was investigated while controlling for sex, age, percent black, percent metropolitan population, population density, and rates of population change, divorce, crime, and unemployment. Gun control laws formed two statistically identifiable groups, (1) laws that place restrictions on the sellers of handguns and (2) laws that place restrictions on the buyers of handguns. A multiple regression analysis indicated that suicide rates were significantly lower in states with low divorce rates, low crime rates, and stringent firearm control laws, as those laws affect both the sellers and the buyers of handguns. The variables in this analysis accounted for 69% of the variance of suicide rates. PMID:2377713

Boor, M; Bair, J H

1990-06-01

110

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

2010-10-01

111

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

PubMed Central

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

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

2004-01-01

112

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.

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

2013-01-01

113

A rumor spreading model with variable forgetting rate  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

114

Variable-rate coding for meteor-burst communications  

NASA Astrophysics Data System (ADS)

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 resulting performance is compared to that obtained from fixed-rate coding. Of central importance is the derivation of tractable expressions for the probability of correct decoding for bounded-distance decoding on a memoryless channel with a time-varying symbol error probability. A throughout measure is developed that is based on the probability distribution of the initial signal-to-noise ratio.

Pursley, Michael B.; Sandberg, Stuart D.

1989-11-01

115

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

PubMed

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

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

2013-06-05

116

Longitudinal analysis of heart rate variability in chronic hypertensive pregnancy.  

PubMed

In the US, it is currently estimated that 3% of pregnant women have chronic hypertension, or more than 100,000 pregnant women each year. The aim of our study was to investigate the adaptation of autonomic control during pregnancy based on heart rate variability analysis and to determine whether chronic hypertension during pregnancy has an impact on this adaptation. Sixteen pregnant women with chronic hypertension (CH group; mean age, 30 years; range, 25-33 years) and 35 healthy pregnant women serving as controls (CON group; mean age, 28 years; range, 24-30 years) were recruited for this longitudinal study. Beginning at the 20th week of pregnancy, the women were monitored every 4th week until delivery. For the analysis of heart rate variability, Portapres signals (200 Hz) were recorded for 30 min under resting conditions. Women in the CH group had significantly elevated blood pressure compared to controls (CON, 111 mmHg [105-132]; CH, 140 mmHg [132-148]; p<0.001). An increased heart rate was found in both groups during the second half of pregnancy. Consequently, decreased heart rate variability was observed, but was more pronounced in the CON group. There was a shift in the frequency bands indicated by an elevation of the low-to-high frequency ratio (LF/HF) in both groups due to a decrease in HF, and thus a significant increase in LFn (LF power in normalized units). However, VLF (power of very low frequency range) increased exclusively in the CON pregnancies. Our data showed no significant difference in heart rate variability between the subjects of the CH and CON groups. Longitudinal variations were detectable in normal pregnancies and also, albeit to a lesser degree, in chronic hypertensive pregnant women. Thus, our data indicate that patients with long-term hypertension are still able to respond to the physiological changes occurring during pregnancy. PMID:16025737

Walther, Thomas; Wessel, Niels; Baumert, Mathias; Stepan, Holger; Voss, Andreas; Faber, Renaldo

2005-02-01

117

Variable Subduction Rates of North Atlantic Salinity Maximum Water  

NASA Astrophysics Data System (ADS)

Data from programs back to 1982, and most recently the 2003-04 Repeat Hydrography, Tracer, CO2 program are used to highlight the role tracer data can have in monitoring decadal variability of ocean circulation. The CFC data are used to document changes in thermocline ventilation, and specifically the affect increased thermocline salinity is having, if any, on Salinity Maximum Water (SMW) subduction rates in the North Atlantic Ocean. Hydrobase data show a long term trend of increasing salinity in the North Atlantic thermocline since the 1950s, and in particular in SMW. SMW is located in the subtropical/tropical north Atlantic under the evaporation minus precipitation maximum. Since SMW are the most saline of the thermocline waters, no source for additional salt exists within the ocean. Subduction rates have been calculated for SMW from 1982-2004 CFC data at stations where there was a subsurface salinity maximum present. The subduction rate for an isopycnal projected back to its outcrop, is calculated from the inverse tracer age gradient corrected for vortex stretching. Subduction rates vary from 10 to 40 m/year. The results show a pattern of changing subduction rates that correlate well with the NAO index. Since salinity seems to have been steadily increasing, though at different rates, it appears that local fresh water variability is not the major forcing effect on the subduction process. The 1990s rise in evaporation rate coincided with a prolonged high state of the North Atlantic Oscillation index (NAO). The associated increase in trade winds will have enhanced both evaporation and Ekman pumping of waters into the upper ventilated thermocline. Consistent with model results, the observational based calculations suggest that increased (decreased) wind stress curl accompanying an increased (decreased) NAO has the major forcing effect on SMW subduction variability.

Fine, R. A.; Willey, D. A.; Happell, J.

2004-12-01

118

Variable-rate hybrid ARQ for meteor-burst communications  

NASA Astrophysics Data System (ADS)

The authors introduce a form of automatic repeat request (ARQ), referred to as variable-rate type-I hybrid ARQ, in which the code rate varies in response to the fluctuations in the power received from a meteor trail. For one implementation, the source or the destination periodically obtains estimates of the signal power at the destination, and the source uses these estimates to select the rate of the code. For an alternative approach, the code rate is determined completely by the decoding successes and failures during previous transmissions. The performance measure is the throughput per trail, which is defined as the expected number of information bits received correctly for a given meteor trail. Numerical results for Reed-Solomon codes are included to illustrate the relative performance of the various schemes. It is shown that the throughput is larger for both implementations of variable-rate type-I hybrid ARQ than for fixed-rate type-I hybrid ARQ and ARQ without forward error correction.

Pursley, Michael B.; Sandberg, Stuart D.

1992-01-01

119

How do variable substitution rates influence Ka and Ks calculations?  

PubMed

The ratio of nonsynonymous substitution rate (Ka) to synonymous substitution rate (Ks) is widely used as an indicator of selective pressure at sequence level among different species, and diverse mutation models have been incorporated into several computing methods. We have previously developed a new gamma-MYN method by capturing a key dynamic evolution trait of DNA nucleotide sequences, in consideration of varying mutation rates across sites. We now report a further improvement of NG, LWL, MLWL, LPB, MLPB, and YN methods based on an introduction of gamma distribution to illustrate the variation of raw mutation rate over sites. The novelty comes in two ways: (1) we incorporate an optimal gamma distribution shape parameter a into gamma-NG, gamma-LWL, gamma-MLWL, gamma-LPB, gamma-MLPB, and gamma-YN methods; (2) we investigate how variable substitution rates affect the methods that adopt different models as well as the interplay among four evolutional features with respect to Ka/Ks computations. Our results suggest that variable substitution rates over sites under negative selection exhibit an opposite effect on omega estimates compared with those under positive selection. We believe that the sensitivity of our new methods has been improved than that of their original methods under diverse conditions and it is advantageous to introduce novel parameters for Ka/Ks computation. PMID:19944384

Wang, Dapeng; Zhang, Song; He, Fuhong; Zhu, Jiang; Hu, Songnian; Yu, Jun

2009-09-01

120

Variable rate irrigation management for peanut in the eastern Coastal Plain  

Technology Transfer Automated Retrieval System (TEKTRAN)

Variable rate irrigation provides farmers with a tool to spatially allocate limited water resources while potentially increasing profits. Optimal management of these variable rate irrigation systems will likely require rapid and reliable spatial data. We conducted variable rate irrigation experiment...

121

Relationship between Heart Rate Turbulence and Heart Rate Variability in Korean Adults with Structurally Normal Heart  

Microsoft Academic Search

Background and Objectives:Heart rate variability (HRV) illustrates the autonomic integration of the heart. Depressed HRV has been proven to be associated with an increased risk of cardiac death, whereas heart rate turbu- lence (HRT) is believed to reflect baroreflex sensitivity and it was recently introduced as another noninvasive tool for risk stratification. The aim of this study was to determine

Ji Ho Yoon; Jin Ho Kang; Byung Jin Kim; Bum Soo Kim

122

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

Microsoft Academic Search

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

Niranjan Bidargaddi; Antti Sarela; Ilkka Korhonen

2008-01-01

123

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

124

Heart rate variability and drawing impairment in hypoxemic COPD  

Microsoft Academic Search

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

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

2009-01-01

125

Heart Rate Variability and Sustained Attention in ADHD Children  

Microsoft Academic Search

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

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

1999-01-01

126

The effects of hypnosis on heart rate variability.  

PubMed

Uslu et al. (2012 ) suggested that hypnotic status can modulate cerebral blood flow. The authors investigated the effects of hypnosis on heart rate variability (HRV). In women, HRV decreased during hypnosis. Posthypnotic values were higher compared to prehypnotic and hypnotic values. Women had highest HRV parameters in the posthypnotic condition. It appears that hypnosis can produce cardiac and cognitive activations. Hypnotherapy may be useful in some cardiac clinical conditions characterized by an autonomic imbalance or some cardiac arrhythmias. PMID:23427840

Yüksel, Ramazan; Ozcan, Osman; Dane, Senol

2013-04-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

128

Threshold modeling of autonomic control of heart rate variability.  

PubMed

Even in the absence of external perturbation to the human cardiovascular system, measures of cardiac function, such as heart rate, vary with time in normal physiology. The primary source of the variation is constant regulation by a complex control system which modulates cardiac function through the autonomic nervous system. Here, we present methods of characterizing the statistical properties of the underlying processes that result in variations in ECG R-wave event times within the framework of an integrate-and-fire model. We first present techniques for characterizing the noise processes that result in heart rate variability even in the absence of autonomic input. A relationship is derived that relates the spectrum of R-R intervals to the spectrum of the underlying noise process. We then develop a technique for the characterization of the dynamic nature of autonomically related variability resulting from exogenous inputs, such as respiratory-related modulation. A method is presented for the estimation of the transfer function that relates the respiratory-related input to the variations in R-wave event times. The result is a very direct analysis of autonomic control of heart rate variability through noninvasive measures, which provides a method for assessing autonomic function in normal and pathological states. PMID:11008415

Stanley, G B; Poolla, K; Siegel, R A

2000-09-01

129

Heart rate and heart rate variability in patients with frequent ventricular arrhythmias  

Microsoft Academic Search

The authors studied associations between heart rate and heart rate variability in 31 patients with frequent ventricular arrhythmias. For each patient, a 24-h Holter tape was analyzed. Tapes were divided into 5-min episodes. Per episode, they computed heart rate (HR), the fraction low-frequency power (LF), and the coefficient of variance (CV). For each patient, scatterplots were made of LF=f(HR), CV=f(HR),

Cees A. Swenne; M. J. A. Janssen; V. M. Cats

1992-01-01

130

[Association between level of intelligence and heart rate variability].  

PubMed

Earlier we discovered that heart rate variability was associated with the level of intelligence. The purpose of this study is to confirm this association using more reliable method and to define more precisely the frequency band within which the amplitude of the heart rate modulations is related to intelligence. 13 males (aged 14 to 17) were the study subjects. The total score of the computer game Tetris was taken as a general measure of the intelligence level. Heart rate was recorded electrocardiographically both at rest and during playing Tetris. Frequency analysis of heart rate was carried out with digital Fourier transformation. Correlation analysis showed that there was positive association between the level of intelligence and the amplitude of heart rate modulation at the frequencies 0.30 and 0.15 modulations per RR interval. This association is closer for the heart rate at rest than for the heart rate during mental work and for the frequency 0.30 than for the 0.15 modulations per RR interval. PMID:21961308

Mukhin, V N; Iakovlev, N M

2011-08-01

131

Heart rate variability and autonomic nerve activities in ambulatory dogs.  

PubMed

Analysis of heart rate variability is a valuable method to investigate the sympathetic and parasympathetic function of the autonomic nervous system. Although such analyses can provide quantitative estimates of autonomic neural activity, simultaneous recording of neural activities and ECG will allow more direct investigation of neural modulation of heart rate. We developed a method that allows direct and long-term recording of neural activities and ECG using wireless device implanted in ambulatory dogs. The aim of this study was to investigate the relationship between autonomic neural firing and heart rate variability. In this study, HRV and neural activities were assessed for 5 continuous days. HRV was evaluated by calculating the mean and the standard deviation of inter-beat intervals in 24 hours. Neural activities were obtained by the sum of the filtered rectified neural signals after 200 Hz high-pass filtering to remove ECG interference. The plots showing HRV as a function of both the sympathetic and vagal activities will offer significant insights into neural modulation of heart rate in normal and diseased hearts. PMID:17946069

Song, Juan; Ogawa, Masahiro; Tan, Alex Y; Chen, Peng-Sheng; Lin, Shien-Fong

2006-01-01

132

Variable-bit-rate HDTV coding algorithm for ATM environments for B-ISDN  

NASA Astrophysics Data System (ADS)

A variable bit-rate HDTV coding algorithm based on motion-adaptive DCT is investigated for ATM environments in B-ISDN. Adaptive 2-layered coding, an ATM cell matrix for error correction, and a block interleave for error concealment are proposed to keep picture quality high by compensating for ATM cell loss. A new VLC and a congestion control scheme that restricts peak-rate and average-rate are also proposed for traffic control. The proposed algorithm is shown to reduce the coding bit-rate for HDTV conference applications in ATM environments to 10 - 30 Mb/s.

Kinoshita, Taizo; Nakahashi, Tomoko; Takizawa, Masaaki

1991-11-01

133

Rates of profit as correlated sums of random variables  

NASA Astrophysics Data System (ADS)

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

Greenblatt, R. E.

2013-10-01

134

Heart rate variability changes in physicians working on night call  

Microsoft Academic Search

Purpose  Adverse effects by night-call duty have become an important occupational health issue. The aim of this study was to investigate\\u000a whether the heart rate variability (HRV) differed during recovery from day work and night-call duty between distinct physician\\u000a specialities.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  We studied the impact of a 16-h night-call duty on autonomic balance, measured by HRV, among two physician groups differing\\u000a with

Birgitta Malmberg; Roger Persson; Per Flisberg; Palle Ørbaek

2011-01-01

135

Nocturnal evolution of heart rate variability indices in sleep apnea.  

PubMed

Heart rate variability (HRV) is a valuable clinical tool in diagnosing multiple diseases. This paper presents the results of a spectral HRV analysis conducted with 46 patients. HRV indices for the whole night show differences among patients with severe and mild apnea, and healthy subjects. These differences also appear when performing the analysis over 5-min intervals, regarding apneas being present or not in the intervals. Differences were also observed when analyzing the HRV nocturnal evolution. Results are consistent with the hypothesis that cardiovascular risk remains constant for OSA patients while it increases towards the end of the night for healthy subjects. PMID:23084286

Lado, María J; Méndez, Arturo J; Rodríguez-Liñares, Leandro; Otero, Abraham; Vila, Xosé A

2012-10-16

136

Decoupling of QT interval variability from heart rate variability with ageing.  

PubMed

Ageing has been associated with changes in cardiac electrophysiology that result in QT interval prolongation. The effect of age on rate-adaptation dynamics of the QT interval is less well understood. The aim of this study was to assess age-related changes in the temporal relationship between QT and RR interval variability. Resting ECG of 20 young and 20 elderly healthy subjects were analyzed. Beat-to-beat RR and QT interval time series were automatically extracted. Coupling between QT and RR was assessed by means of the QT variability index, coherence in the frequency domain, rate-corrected QT interval, cross-multiscale entropy, information based similarity index and joint symbolic dynamics. In addition to QT interval prolongation (433 ± 31 versus 405 ± 33 ms, p = 0.008), elderly subjects were characterized by a significantly increased QT variability index (-1.26 ± 0.28 versus -1.52 ± 0.22 ms, p < 0.0001), reduced coherence in high (0.11 ± 0.09 versus 0.29 ± 0.14 ms, p = 0.003), and low frequency bands (0.20 ± 0.16 versus 0.49 ± 0.15 ms, p < 0.0001), reduced information domain synchronization index (0.13 ± 0.07 versus 0.19 ± 0.05 ms, p = 0.001) as well as increased entropy and disparity in joint symbolic dynamics of QT and RR interval time series. In conclusion, ageing is associated with decoupling of QT variability from heart rate variability. Complexity analysis in addition to standard metrics may provide additional insight. PMID:24104598

Baumert, Mathias; Czippelova, Barbora; Porta, Alberto; Javorka, Michal

2013-10-08

137

Decreased heart rate variability in amyotrophic lateral sclerosis.  

PubMed

Autoregressive spectral analysis of heart rate variability (HRV) was performed in 29 patients with amyotrophic lateral sclerosis (ALS) and 33 age-matched healthy subjects to evaluate the involvement of the autonomic nervous system. HRV analysis provides a means to recognize low (LF) and high (HF) frequency components, respectively mediated by sympathetic and parasympathetic heart control. An increase in the mean heart rate at rest (P < 0.001), a decrease in standard deviation of R-R interval as well as in PNN50 (P < 0.001), and an increase in the LF/HF component ratio (P < 0.01) were found in the ALS patients, indicating a vagal-sympathetic imbalance. These alterations were not related to the clinical features and to the duration of the disease. Our results suggest a subclinical involvement of the autonomic nervous system in ALS, particularly affecting parasympathetic cardiovascular control. PMID:7565918

Pisano, F; Miscio, G; Mazzuero, G; Lanfranchi, P; Colombo, R; Pinelli, P

1995-11-01

138

Money, Interest Rate and Foreign Exchange Rate As Indicator Variables Of Monetary Policy  

Microsoft Academic Search

Since monetary policy operations affect the ultimate targets such as real income and prices with considerable time lags, this papers attempts to identify the indicator variable of monetary policy in Korea by using autoregression tests, variance docompositions of VAR forecasts and cointegration analyses. The results show that in Korea unlike the U.S., a broad concept of money, interest rate and

Lee TongHung; Hwang Hoyoung

2001-01-01

139

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

2013-02-01

140

A CHEMICAL EXPLANATION OF THE VARIABILITY OF THE GROWTH RATE  

PubMed Central

The general belief that uniform cells under uniform conditions will all multiply at the same moment implies that the smallest units of the chromosomes, i.e., either the genes or the molecules of which the genes are composed, all double at exactly the same moment in all cells. Since the doubling of chromosomes is a synthetic chemical process, it seems more probable that it would follow chemical laws. With the assumption that the corresponding molecules in a number of uniform cells obey the mass law in their process of doubling, a definite order in the multiplication of identical cells is established which can be formulated mathematically for the simplest case. This is the same assumption which the author has used to account for the differences in the order of death between bacteria and higher organisms. This theory demands a great variability of the growth rate of uniform cells, so great that it must be experimentally measurable even for cells with a million molecules to the chromosome. The theory demands further that the frequency curve of cell divisions plotted for successive time intervals, be skewed to the left, and that the relative range of variation become smaller as the number of genes or gene-type molecules increases. Experiments on the growth rate of Bacterium aerogenes and Saccharomyces ellipsoideus showed regularly a frequency curve skewed to the left. The yeast had a relatively narrower range of variability than the bacterium. Even with multicellular organisms, theoretical calculations show a range of variation of the growth rate from the egg cell which should still be measurable though it decreases relatively with the number of cells produced. An experiment on the size of bacteria colonies at different ages of development agreed with the theory.

Rahn, Otto

1932-01-01

141

Heart rate variability abnormalities in young patients with dilated cardiomyopathy.  

PubMed

Heart rate variability (HRV) has become the conventionally accepted term for describing variations in both instantaneous heart rate and R-R intervals. In the pediatric age group, HRV has been investigated in healthy children, diabetics, respiratory distress syndrome of the newborn, and sudden infant death syndrome. This study aimed to evaluate HRV in pediatric patients with dilated cardiomyopathy and to compare it with that of age-matched normal subjects. The study evaluated 21 patients with dilated cardiomyopathy: 11 females (mean age, 7 ± 4 years; range, 2-17 years) and 10 males (mean age, 10 ± 6 years; range, 2-18 years). Dilated cardiomyopathy (DCM) was diagnosed according to commonly accepted criteria after a noninvasive cardiologic examination, echocardiography, and 24-h Holter monitoring (MR45 and MR45-3 Oxford recorder). The patients were divided into six groups according to age, sex, and type of cardiomyopathy. Heart rate variability was recorded and analyzed in the time domain. The patients with DCM showed an abnormal HRV pattern. Particularly in the 5-6-year-old male patient group, the HRV values all were significantly increased (p = 0.05). In the 2-6-year-old female patient group, the mean cycle length, the standard deviation of all normal sinus R-R intervals during 24 h (SDNN), and the standard deviation of the average normal sinus R-R intervals for all 5-min segments (SDANN) were significantly increased (p = 0.05). The 13-18-year-old female patient group showed a significant reduction in SDNN and the mean of the standard deviation of all normal sinus R-R intervals for all 5-min segments (SDNNi) (p = 0.05). The modification of the HRV pattern in the time domain, partially age- and gender-dependent modification, may reflect an imbalance of the autonomic nervous system in children who show a delayed or reduced activity, such as pediatric patients with DCM. PMID:22411717

Grutter, Giorgia; Giordano, Ugo; Alfieri, Sara; Iodice, Francesca; Drago, Fabrizio; Ravà, Lucilla; Silvetti, Massimo Stefano

2012-03-13

142

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

Code of Federal Regulations, 2010 CFR

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

2010-01-01

143

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

Code of Federal Regulations, 2010 CFR

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

2009-01-01

144

Two-phase simulation of a variable rate infiltration experiment  

NASA Astrophysics Data System (ADS)

Flow and transport processes in unsaturated soils are typically modeled through Richards' equation with retention and hydraulic conductivity curves obtained under static and stationary conditions, respectively. This model is commonly applied to quantify infiltration at the hillslope scale under strongly varying rainfall intensity, which leads to varying infiltration rates. To our knowledge detailed laboratory experiments reproducing this situation in large columns of length comparable with the soil thickness in Alpine hillslopes are lacking. In the present work we analyze and model variable rate infiltration experiments performed in a sand column accurately instrumented with tensiometers and TDR probes. Previous analyses revealed that data collected during transient experiments are not falling within the main wetting and drying curves obtained with careful analysis under static conditions. On the other hand, as expected, the same retention curves were able to reproduce with high accuracy experiments conducted under quasi-static conditions. As a consequence, the Richards' model was unable to reproduce the pressure distribution along the column during transient experiments conducted with variable rainfall rates. These findings have important consequences, e.g. for the prediction of runoff production and hill-slope stability. We propose that this discrepancy may be due to the influence of air flow on water pressure which is expected to be much higher under variable rainfall conditions when rapid saturation of the top soil may limit air to escape from above. In the present work, we numerically investigated this hypothesis using a two-phase air-water flow model. The numerical solver is based on a linear FEM-based pressure-pressure formulation where accurate mass balance is preserved by careful choice of spatial and temporal discretization of the nonlinear terms. The pressure-pressure formulation is chosen to ensure proper implementation of the pressure-based boundary conditions that need to be imposed at the top of the column under condition of infiltration in unsaturated soil. Simulation results show that including air dynamic into the modeling approach provides a better match between experimental and numerical simulations.

Luvisotto, V.; Manoli, G.; Cainelli, O.; Bellin, A.; Marani, M.; Putti, M.

2012-04-01

145

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

2013-07-09

146

Heart rate variability: Response to graded head up tilt in healthy men  

Microsoft Academic Search

Background: Heart rate variability is actually a misnomer for R to R variability in cardiac cycle. Variation in successive cycle length is called the heart rate variability (HRV). Head-up tilt is a model of studying cardiovascular haemodynamics, which refl ects in heart rate variability (HRV). Objectives: To study the effect of 10° and 70° head-up tilt on HRV. Materials and

Sharma P; Paudel BH; Singh PN; Limbu P

147

Heart rate variability and disease characteristics in patients with COPD.  

PubMed

Heart rate variability (HRV) is reduced in patients with chronic obstructive pulmonary disease (COPD). However, the relationships among HRV and characteristics of COPD are unknown. The aim of this study was to characterize HRV in patients with COPD and to verify the correlation of HRV measured during rest with disease severity and pulmonary, muscular, and functional impairment. Thirty-one patients with COPD (16 male; 66 +/- 8 years; BMI = 24 +/- 6 kg/m(2); FEV(1) = 46 +/- 16% predicted) without severe cardiac dysfunction were included. HRV assessment was performed by the head-up tilt test (HUTT), and the main variables used for analysis were SDNN index, LF/HF ratio, and R-R intervals. Other tests included spirometry, bioelectrical impedance, cardiopulmonary exercise test, 6-minute walk test, respiratory and peripheral muscle force, health-related quality of life and functional status questionnaires, and objective quantification of physical activity level in daily life with the DynaPort and SenseWear armband activity monitors, besides calculation of the BODE index. There was a statistical difference in all variables of HRV between the HUTT positions (lying and standing). There was no correlation of HRV with BODE index or FEV(1). Out of the BODE index, just the BMI was correlated with SDNN and R-R intervals (r = 0.44; p < 0.05 and r = 0.37; p < 0.05, respectively). There was correlation between HRV reduction and a lower level of physical activity in daily life, besides worse health-related quality of life, functional status, and respiratory and peripheral muscle force. Cardiac autonomic function of patients with COPD is not related to disease severity but mainly to the level of physical activity in daily life. PMID:18815834

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

2008-09-25

148

Robustness and perturbation in the modeled cascade heart rate variability  

NASA Astrophysics Data System (ADS)

In this study, numerical experiments are conducted to examine the robustness of using cascade to describe the multifractal heart rate variability (HRV) by perturbing the hierarchical time scale structure and the multiplicative rule of the cascade. It is shown that a rigid structure of the multiple time scales is not essential for the multifractal scaling in healthy HRV. So long as there exists a tree structure for the multiplication to take place, a multifractal HRV and related properties can be captured by using the cascade. But the perturbation of the multiplicative rule can lead to a qualitative change. In particular, a multifractal to monofractal HRV transition can result after the product law is perturbed to an additive one at the fast time scale. We suggest that this explains the similar HRV scaling transition in the parasympathetic nervous system blockade.

Lin, D. C.

2003-03-01

149

Heart rate variability in newborns with hypoxic brain injury.  

PubMed

In neonatal intensive care units, there is a need for continuous monitoring of sick newborns with perinatal hypoxic ischemic brain injury (HIE). We assessed the utility of heart rate variability (HRV) in newborns with acute HIE undergoing simultaneous continuous EEG (cEEG) and ECG monitoring. HIE was classified using clinical criteria as well as visual grading of cEEG. Newborns were divided into two groups depending on the severity of the hypoxic injury and outcome. Various HRV parameters were compared between these groups, and significantly decreased HRV was found in neonates with severe HIE. As HRV is affected by many factors, it is difficult to attribute this difference solely to HIE. However, this study suggests that further investigation of HRV as a monitoring tool for acute neonatal hypoxic injury is warranted. PMID:23852475

Mati?, Vladimir; Cherian, Perumpillichira J; Widjaja, Devy; Jansen, Katrien; Naulaers, Gunnar; Van Huffel, Sabine; De Vos, Maarten

2013-01-01

150

Electrochemical Corrosion Rate Sensors for Waste Incineration Applications  

SciTech Connect

Electrochemical corrosion rate sensors work in high temperature waste incineration applications where ash is deposited. The ash serves as the electrolyte for electrochemical measurements, such as liner polarization resistance, electrochemical noise, and harmonic distortion analyses. Results to date have shown that these types of sensors respond qualitatively to changes in temperature, gas composition, alloy composition, and type of ash. Several years of research have shown that high temperature corrosion rate probes need to be better understood before corrosion rate can be used as a process variable by power plant operators. More recent research has shown that electrochemical corrosion probes typically measure lower corrosion rates than those measured by standard mass loss techniques. While still useful for monitoring changes in corrosion rates, absolute probe corrosion rates will need a calibration factor to be useful. Ideas for research that may help resolve these issues are presented.

Covino, B.S., Jr.; Bullard, S.J.; Matthes, S.A.; Holcomb, G.R.; Ziomek-Moroz, M.; Eden, D.A. (Honeywell Intercorr)

2007-03-01

151

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

NASA Astrophysics Data System (ADS)

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

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

1991-06-01

152

Age, gender and fractal scaling in heart rate variability.  

PubMed

1. The fractal scaling of heart rate variability, gauged by the correlation dimension (CD), is hypothesized to be characterized by a time structure (chronome), which in health shows differences as a function of gender and age. 2. From 24 h Holter records of 44 clinically healthy male subjects in four age groups (5-10, 20-25, 40-45 and 60-65 years; n = 11 in each group), 500 s sections at 4 h intervals for 24 h were analysed for smoothed R-R intervals sampled at 4 Hz. Using an algorithm modified from Grassberger and Procaccia (Physica D 1983; 9: 189-208), the correlation integral was estimated for embedding dimensions from 1 to 20 with a 1.0 s time lag for each section. Nightly (02.00 hours-06.00 hours) ECG records were similarly analysed in 72 additional clinically healthy subjects of both genders, 5-70 years of age. The single cosinor assessed the circadian characteristics; one- and two-way analyses of variance and linear regression were used to examine changes as a function of gender and age. 3. The 24 h average of CD is largest in the 20-25-year-old men and decreases with age there-after (P < 0.05). These changes apply in particular to the nightly CD values, which are higher in female than in male subjects (P < 0.001). Increasing age is associated with a decrease in the amplitude and an advance in the phase of the circadian rhythm in CD (P < 0.05). 4. A chaotic end-point from fractal scaling, yielding a non-linear index, such as the correlation integral, undergoes a circadian rhythm and changes with gender and age. This assessment in the chronome represents an added diagnostic tool in cardiology, and provides new end-points for the study of coherence among internal variables of autonomic mechanisms and of influences by external environmental variables upon them. PMID:9404221

Otsuka, K; Cornelissen, G; Halberg, F

1997-10-01

153

SEER*Stat Rate Exercise 2: Variables With Unlabeled Values  

Cancer.gov

This exercise focuses on the techniques for working with variables that have unlabeled values. Most variables in the database have labeled values (e.g., the values for race are "White", "Black", etc.), but labeled values are not practical for all variables. For example, histologic type has nearly 2,000 values represented as integers (8000-9992). While there are histologic type variables with labeled values available in the database, it is sometimes easier to use numeric ranges to group the values when creating user-defined variables.

154

Variable-rate irrigation management for peanut in the eastern Coastal Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

Variable rate irrigation systems provide farmers with a tool to spatially allocate limited water resources while potentially increasing profits. To optimally management these variable rate irrigation systems, we conducted irrigation experiments on peanuts to compare spatial irrigation management usi...

155

Heart rate variability and target organ damage in hypertensive patients  

PubMed Central

Background We evaluated the association between linear standard Heart Rate Variability (HRV) measures and vascular, renal and cardiac target organ damage (TOD). Methods A retrospective analysis was performed including 200 patients registered in the Regione Campania network (aged 62.4?±?12, male 64%). HRV analysis was performed by 24-h holter ECG. Renal damage was assessed by estimated glomerular filtration rate (eGFR), vascular damage by carotid intima-media thickness (IMT), and cardiac damage by left ventricular mass index. Results Significantly lower values of the ratio of low to high frequency power (LF/HF) were found in the patients with moderate or severe eGFR (p-value?

2012-01-01

156

[Continuous wavelet analysis of heart rate variability during general anesthesia].  

PubMed

The depth of anesthesia can be assessed by means of analyzing heart rate variability (HRV). Continuous wavelet transform (CWT) was used to obtain more accurate results on the changes of low frequency (LF) and high frequency (HF) components of HRV signals (RR interval sequences) before and after general anesthesia. With wavelet scale transformed into frequency, the obtained time-frequency energy distributions showed that the LF and HF components of HRV signals were suppressed after general anesthesia, while the LF/HF ratio reduced from 9.0219 to 3.5573. The time-frequency distribution showed that CWT can more accurately locate the abrupt changes in time-domain, giving more precise range of frequency changing, compared with traditional time-frequency analysis method. The results indicated that, as a new time-frequency analysis method of analyzing HRV during general anesthesia, CWT provides more accurate time-frequency location, and consequently, offers more accurate monitoring results of anesthesia depth. PMID:22616190

Wang, Yudong; Li, Chuanyong

2012-04-01

157

Heart rate variability as a biomarker of fibromyalgia syndrome  

PubMed Central

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

Staud, Roland

2009-01-01

158

Gender differences in personality and heart-rate variability.  

PubMed

Both personality traits and autonomic functioning show as gender differences, but their relationship is not well understood. Medically unexplained symptoms are related to personality features and can be assessed by autonomic measurement. The patterns are hypothesised to identify gender differences. We recruited 30 male and 30 female healthy volunteers. All participants completed the Tridimensional Personality Questionnaire (TPQ) and heart-rate variability (HRV) measurement. Correlation analysis was performed to identify the relationships between TPQ scores and HRV parameters. For the subjects as a whole, the subdimension harm avoidance 4 (HA4, fatigability and asthenia) was found to be negatively correlated with low-frequency (LF) power, high-frequency (HF) power and total power (TP) of HRV. Novelty seeking 1 (NS1, exploratory excitability) was found to be positively correlated with LF power and TP. Multiple linear regression analysis revealed that the interactions exploratory excitability x gender and fatigability x gender are predictors of LF and HF power, respectively. Our result supports the hypothesis that personality features such as exploratory excitability and fatigability are associated with autonomic functioning and that gender is a moderator in these relationships. PMID:23499230

Huang, Wei-Lieh; Chang, Li-Ren; Kuo, Terry B J; Lin, Yu-Hsuan; Chen, Ying-Zai; Yang, Cheryl C H

2013-03-15

159

Heart Rate Variability Analysis in Patients with Allergic Rhinitis  

PubMed Central

Background. Very few studies investigate the role of the autonomic nervous system in allergic rhinitis. In this study, we evaluated the autonomic nervous system in allergic rhinitis patients using heart rate variability (HRV) analysis. Methods. Eleven patients with allergic rhinitis and 13 healthy controls, aged between 19 and 40 years old, were enrolled in the study. Diagnosis of allergic rhinitis was based on clinical history, symptoms, and positive Phadiatop test. Electrocardiographic recordings on the sitting and supine positions were obtained for HRV analysis. Results. In the supine position, there were no significant statistical differences in very-low-frequency power (VLF, ?0.04?Hz), low-frequency power (LF, 0.04–0.15?Hz), high-frequency power (HF, 0.15–0.40?Hz), and the ratio of LF to HF (LF/HF) between the patient and control groups. The mean RR intervals significantly increased, while LF% and LF/HF significantly decreased in the patient group in the sitting position. Moreover, mean RR intervals, LF, and LF/HF, which were significantly different between the two positions in the control group, did not show a significant change with the posture change in the patient group. Conclusion. These suggest that patients with allergic rhinitis may have poor sympathetic modulation in the sitting position. Autonomic dysfunction may therefore play a role in the pathophysiology of allergic rhinitis.

Lee, Guo-She; Shiao, An-Suey; Ko, Jen-Hung; Shu, Chih-Hung

2013-01-01

160

Omega-3 Polyunsaturated Fatty Acids and Heart Rate Variability  

PubMed Central

Omega-3 polyunsaturated fatty acids (PUFA) may modulate autonomic control of the heart because omega-3 PUFA is abundant in the brain and other nervous tissue as well as in cardiac tissue. This might partly explain why omega-3 PUFA offer some protection against sudden cardiac death (SCD). The autonomic nervous system is involved in the pathogenesis of SCD. Heart rate variability (HRV) can be used as a non-invasive marker of cardiac autonomic control and a low HRV is a predictor for SCD and arrhythmic events. Studies on HRV and omega-3 PUFA have been performed in several populations such as patients with ischemic heart disease, patients with diabetes mellitus, patients with chronic renal failure, and in healthy subjects as well as in children. The studies have demonstrated a positive association between cellular content of omega-3 PUFA and HRV and supplementation with omega-3 PUFA seems to increase HRV which could be a possible explanation for decreased risk of arrhythmic events and SCD sometimes observed after omega-3 PUFA supplementation. However, the results are not consistent and further research is needed.

Christensen, Jeppe Hagstrup

2011-01-01

161

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

PubMed

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

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

2009-07-24

162

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

PubMed

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

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

2013-02-11

163

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.

Godfray, H Charles J; Rees, Mark

2002-01-01

164

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

PubMed Central

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 signal and its usefulness for assessing pulse rate variability (PRV). Methods Simulated pulse wave signals with known pulse interval functions and actual pulse wave signals obtained from 30 subjects with a trans-dermal pulse wave device were analyzed by PFDM. The results were compared with heart rate and HRV assessed from simultaneously recorded ECG. Results Analysis of simulated data revealed that the PFDM faithfully demodulates source interval function with preserving the frequency characteristics of the function, even when the intervals fluctuate rapidly over a wide range and when the signals include fluctuations in pulse height and baseline. Analysis of actual data revealed that individual means of low and high frequency components of PRV showed good agreement with those of HRV (intraclass correlation coefficient, 0.997 and 0.981, respectively). Conclusion The PFDM of pulse wave signal provides a reliable assessment of PRV. Given the popularity of pulse wave equipments, PFDM may open new ways to the studies of long-term assessment of cardiovascular variability and dynamics.

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

2005-01-01

165

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

2011-11-29

166

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.

Blair, Steven N.; Church, Timothy S.

2012-01-01

167

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

168

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2013 CFR

...instrument that provides for a rate of interest that is periodically adjusted to equal the current interest rate of Bank's commercial paper. Variations in the value of this interest rate can reasonably be expected...

2013-04-01

169

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

170

Continuously Variable Transmission: Assessment of Applicability to Advanced Electric Vehicles.  

National Technical Information Service (NTIS)

A brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. The arrangement and function...

S. H. Loewenthal R. J. Parker

1981-01-01

171

Variable Thermal Conductivity, Slab Mineralogy, and Subduction Rates  

NASA Astrophysics Data System (ADS)

Models of subducting slabs have suggested that metastable olivine (MO) in the slabs' cold interiors can act like parachutes and reduce their density (? ), lowering the slabs' velocities by up to 30% [Marton et al., 1999; Schmeling et al., 1999] These models, however, use constant values of thermal conductivity (k)to solve the heat flow equation. Models that use ks that are functions of P, T, and mineralogy have wedges of MO that are 20-30% smaller in cross-sectional area and whose maximum extents are 30-50 km shallower [Hauck et al., 1999; Marton et al., 2004]. As a result of the decreased amount of MO, the parachute effect should also be decreased. Using the same thermo-kinetic model as Marton et al. [2004] I determine the mineralogy of three sets of subducting slabs and calculate the driving forces acting on them. Terminal velocities (vt) are found via balances of the driving forces and the opposing viscous drag forces. For the same two sets of slabs examined using the previous constant k model [Marton et al., 1999] (thermal parameter ?rphi = 3500-12000 km), this model shows reductions that are approximately half those of the former, with maximum reductions of 1-1.25 cm/yr or ˜15%. A third set, with older lithosphere (100 My) and ?rphi = 5200-17000 km, show reductions of up to ˜2 cm/yr or 25%. In addition, there should be a negative feedback between the amount of MO and subduction velocity, narrowing the range of subduction rates [Marton et al., 1999; Tetzlaff and Schmeling, 1999]. This is tested by feeding vts back into the model, adjusting the durations of the iterations. The resultant vts and amounts of MO achieve a steady state within a few My after the slabs' tips exit the transition zone. In this case, the size of the parachute effect is dependent on lithospheric age. One set that has constant starting velocities and variable ages shows the same trend as without the feedback, but with vt changes ˜1% smaller. The other two sets with constant ages each have vt changes that are constant, +2.2% for 70 My old lithosphere, -1.3% for 100 My old lithosphere, that are in-line with the trends of the first group.

Marton, F. C.

2004-12-01

172

Review and classification of variability analysis techniques with clinical applications  

PubMed Central

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

2011-01-01

173

Causal coherence analysis of heart rate variability and systolic blood pressure variability under mental arithmetic task load  

Microsoft Academic Search

Causal coherence analysis based on a closed-loop bivariate autoregressive model was applied to heart rate variability and systolic blood pressure (SBP) variability during mental arithmetic tasks to clarify how mental task load affects the linear closed loop interaction between cardiac and vascular systems. Thirteen normal male subjects performed a mental arithmetic task, button press task, and rest task while measuring

Kohzoh Yoshino; Katsunori Matsuoka

2005-01-01

174

Autonomic control of heart rate during physical exercise and fractal dimension of heart rate variability.  

PubMed

The objectives of the present study were to investigate autonomic nervous system influence on heart rate during physical exercise and to examine the relationship between the fractal component in heart rate variability (HRV) and the system's response. Ten subjects performed incremental exercise on a cycle ergometer, consisting of a 5-min warm-up period followed by a ramp protocol, with work rate increasing at a rate of 2.0 W/min until exhaustion. During exercise, alveolar gas exchange, plasma norepinephrine (NE) and epinephrine (E) responses, and beat-to-beat HRV were monitored. HRV data were analyzed by "coarse-graining spectral analysis" (Y. Yamamoto and R. L. Hughson. J. Appl. Physiol. 71: 1143-1150, 1991) to break down their total power (Pt) into harmonic and nonharmonic (fractal) components. The harmonic component was further divided into low-frequency (0.0-0.15 Hz) and high-frequency (0.15-0.8 Hz) components, from which low-frequency and high-frequency power (Pl and Ph, respectively) were calculated. Parasympathetic (PNS) and sympathetic (SNS) nervous system activity indicators were evaluated by Ph/Pt and Pl/Ph, respectively. From the fractal component, the fractal dimension (DF) and the spectral exponent (beta) were calculated. The PNS indicator decreased significantly (P < 0.05) when exercise intensity exceeded 50% of peak oxygen uptake (VO2 peak). Conversely, the SNS indicator initially increased at 50-60% VO2peak (P < 0.05) and further increased significantly (P < 0.05) at > 60% VO2peak when there were also more pronounced increases in NE and E.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8458809

Nakamura, Y; Yamamoto, Y; Muraoka, I

1993-02-01

175

Transfer of Online Learning to Performance in Variable Application Environments  

ERIC Educational Resources Information Center

|The use of online learning (OL) has increased dramatically in the last decade; however, many instructional methods used in OL training design have not been appropriately applied or developed. Complicating this phenomenon, learners of different organizations often find the application of training content problematic in variable application

Merkley, Rodney J.; Nichols, Susan

2007-01-01

176

Police levels and crime rates: An instrumental variables approach  

Microsoft Academic Search

While police levels may affect crime, governments may react to crime by increasing police levels. The instrumental variables (IV) approach to this problem has proven difficult due to the problem of locating instruments for police levels. Using panel data from over 5000 cities (1990–2001), we instrumented police levels with two types of federal law enforcement grants, thus yielding over-identified models.

John L. Worrall; Tomislav V. Kovandzic

2010-01-01

177

Heart rate, heart rate variability and behaviour of horses during air transport.  

PubMed

Heart rate (HR), HR variability (HRV) and behaviour score (BS) of nine horses were evaluated during an eight-hour air transport between The Netherlands and New York. HR and HRV parameters were calculated every five minutes during the air transport. Compared with transit (40±3), mean HRs were higher during loading into the jet stall (67±21, P<0.001), loading into the aircraft (47±6, P=0.011), taxiing (50±8, P=0.001), and during periods of in-flight turbulence (46±7, P=0.017). During the flight, individual horses showed differences in mean HR (P=0.005) and peak HR (P<0.001). By contrast with HR data, HRV data did not differ between stages or horses. BS was highest during turbulence (3.2±0.4). However, behaviour did not always correspond with HR measurements: the least responsive horse had the highest HR. Loading into the jet stall caused the highest increase in HR and was considered the most stressful event. During transit, HR was generally comparable with resting rates. Previous studies have shown that loading and transporting by road caused more elevation in HR than during loading and transporting by air. HRV data were not found to be useful, and caution is needed when interpreting HRV data. Not every horse exhibited stress through visible (evasive) behaviour, and HR measurements may provide an additional tool to assess stress in horses. PMID:23143989

Munsters, C C B M; de Gooijer, J-W; van den Broek, J; van Oldruitenborgh-Oosterbaan, M M Sloet

2012-11-09

178

Autonomic control of heart rate during exercise studied by heart rate variability spectral analysis.  

PubMed

Spectral analysis of heart rate variability (HRV) might provide an index of relative sympathetic (SNS) and parasympathetic nervous system (PNS) activity during exercise. Eight subjects completed six 17-min submaximal exercise tests and one resting measurement in the upright sitting position. During submaximal tests, work rate (WR) was increased for the initial 3 min in a ramp fashion until it reached constant WRs of 20 W, or 30, 60, 90, 100, and 110% of the predetermined ventilatory threshold (Tvent). Ventilatory profile and alveolar gas exchange were monitored breath by breath, and beat-to-beat HRV was measured as R-R intervals of an electrocardiogram. Spectral analysis was applied to the HRV from 7 to 17 min. Low-frequency (0-0.15 Hz) and high-frequency (0.15-1.0 Hz) areas under power spectra (LO and HI, respectively) were calculated. The indicator of PNS activity (HI) decreased dramatically (P less than 0.05) when the subjects exercised compared with rest and continued to decrease until the intensity reached 60% Tvent. The indicator of SNS activity (LO/HI) remained unchanged up to 100% Tvent, whereas it increased abruptly (P less than 0.05) at 110% Tvent. The results suggested that (cardiac) PNS activity decreased progressively from rest to a WR equivalent to 60% Tvent, and SNS activity increased only when exercise intensity exceeded Tvent. PMID:1757310

Yamamoto, Y; Hughson, R L; Peterson, J C

1991-09-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

180

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

Code of Federal Regulations, 2013 CFR

...accordance with variable-rate regulations of other...Handbook on Adjustable Rate Mortgages published...the Federal Home Loan Bank Board, or a suitable...disclosure for each variable-rate program in which the consumer expresses an interest. The following...

2013-01-01

181

Exchange rate variability as an OCA criterion: Are the candidates ripe for the euro?  

Microsoft Academic Search

One measure of whether the candidate countries in Central Europe should join the euro is the degree of real exchange rate variability they are experiencing at present. If it is high one could argue that they 'need' still some exchange rate flexibility to absorb asymmetric shocks. Our results suggest that the still remaining variability of real exchange rates in Central

Daniel Gros; Alexandr Hobza

2003-01-01

182

Relationship of Extraneous Variables to Student Ratings of Instructors.  

ERIC Educational Resources Information Center

Student ratings on general, broad questionnaires about instructors are shown to lack validity to the extent that the ratings can be predicted from irrelevant characteristics, such as characteristics that belong to the student, the particular class, or interactions of the student and the class. (Author/JKS)

Korth, Bruce

1979-01-01

183

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2010 CFR

...related party). Example 1. Rate based on LIBOR. X issues a debt instrument that provides...1-year London Interbank Offered Rate (LIBOR) at the end of each year. Variations in the value of 1-year LIBOR over the term of the debt instrument...

2009-04-01

184

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2010 CFR

...related party). Example 1. Rate based on LIBOR. X issues a debt instrument that provides...1-year London Interbank Offered Rate (LIBOR) at the end of each year. Variations in the value of 1-year LIBOR over the term of the debt instrument...

2010-04-01

185

Playing a violent television game affects heart rate variability  

Microsoft Academic Search

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

Malena Ivarsson; Martin Anderson; Torbjörn Åkerstedt; Frank Lindblad

2009-01-01

186

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

187

Analysis of skin-temperature variability compared to variability of blood pressure and heart rate  

Microsoft Academic Search

High resolution skin-temperature measurement performed in normal human subjects and in patients with coronary artery disease revealed low-amplitude temperature oscillations (40×10-3°C) designated as `Temperature Variability' (TV). Spectral analysis of the filtered signal showed that most of the energy was in the range 0.015-0.04 Hz. Power spectra of temperature variability and pulse pressure amplitude were compared. Both of the signals exhibited

Ofer Barnea; Vladimir Shusterman

1995-01-01

188

Methods of analysis of heart rate variability in anesthetic practice  

Microsoft Academic Search

The present investigation is aimed to estimate preliminarily the efficiency of the VHR-analysis application during operation as one of the methods for determination of the adequacy of anesthetic mean. Particularly, using the procedure of the determination of VNS tension index by Baevsky. Investigations were performed at Research Institute of Oncology and at Tomsk Regional Clinical Hospital. In Figs 1 and

A. V. Maneev; A. N. Rybakov

2002-01-01

189

Regression Discontinuity Designs with Multiple Rating-Score Variables  

ERIC Educational Resources Information Center

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

Reardon, Sean F.; Robinson, Joseph P.

2012-01-01

190

Improved Variable Index constant false alarm rate radar processors  

Microsoft Academic Search

In the cases when the statistical distribution of range return samples are not known, constant false alarm rate (CFAR) processors can be used. Cell Averaging (CA) CFAR radar processors which have the best performance in Gaussian homogeneous environments, exhibits performance degradation in the presence of an interfering target or in regions of abrupt change in the backround clutter power. The

Y. C. U?n; K. M. U?ner

2010-01-01

191

Perishable inventory systems with variable input and demand rates  

Microsoft Academic Search

We consider a certain class of perishable inventory systems with items and demands arriving at random times. The shelf lifetime of every item is finite and deterministic. Every demand is for a single item and is satisfied by the oldest item on the shelf, if available. Generalizing previous work, we assume that the input and\\/or the demand rate depend on

Steven Nahmias; David Perry; Wolfgang Stadje

2004-01-01

192

Effects of Propellant Composition Variables on Acceleration-Induced Burning-Rate Augmentation of Solid Propellants.  

National Technical Information Service (NTIS)

This work was conducted to define further the effects of propellant composition variables on the acceleration-induced burning rate augmentation of solid propellants. The rate augmentation at a given acceleration was found to be a nonlinear inverse functio...

G. B. Northam

1972-01-01

193

EEM quantization revisited: asymptotic optimality for variable rate coding  

NASA Astrophysics Data System (ADS)

Equal-Expectation Magnitude Quantization (EEM) aims at minimizing the distortion of a quantizer with defined reconstruction points by shifting the deadzone parameter such that the expectation value of the signal equals the reconstructed value. While intuitively clear, this argument is not sufficient to prove rate-distortion optimality. In this work, it is show that the EEM quantizer is rate-distortion optimal up to third order in an expansion in powers of the quantization bucket size in the high-bitrate appoximation, and the approximating series for the optimal quantizer is computed. This result is compared to an even simpler quantization strategy based on the LLoyd-Max quantizer which selectively sets coefficients to zero. It is shown that both strategies lead to the same asymptotic expansion for the threshold parameter, but zeroing coefficients provides optimality in one additional order in the quantization bucket size.

Richter, Thomas

2011-09-01

194

Heart rate and ventilatory frequency as dimension-dependent variables  

Microsoft Academic Search

Summary  Heart rate (HR) and ventilatory frequency (f) were determined at rest in 79 boys and 91 girls aged 0.07–20 years and with a range in heights from 54–198 cm to establish the relationship between decrease in HR and f during early life with increase in body dimensions. From theoretical considerations it is assumed that frequencies such as HR and f

Erling Asmussen; N. H. Secher; E. A. Andersen

1981-01-01

195

Variability in Nest Survival Rates and Implications to Nesting Studies  

NSDL National Science Digital Library

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

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

1982-01-01

196

Interference well testing---variable fluid flow rate  

Microsoft Academic Search

At present when conducting an interference well test a constant flow rate (at the 'active' well) is utilized and the type-curve matching technique (where only 2-3 values of pressure drops are matched) is used to estimate the porosity-total compressibility product and formation permeability. For oil and geothermal reservoirs with low formation permeability the duration of the test may require a

I. M. Kutasov; L. V. Eppelbaum; M. Kagan

2008-01-01

197

Variable-heating-rate wire-mesh pyrolysis apparatus  

Microsoft Academic Search

An electrically heated wire-mesh apparatus for pyrolysis studies has been developed which uses computer-driven feedback control for the heating system and thus can apply virtually any time-temperature history to the sample. Internal components are water cooled to prevent heat buildup during long runs. Using this system, coal pyrolysis has been studied at heating rates from 0.1 to about 5000 K\\/s

J. R. Gibbins; R. A. V. King; R. J. Wood; R. Kandiyoti

1989-01-01

198

Industrial application of variable speed drive system for high speed in megawatt power range  

Microsoft Academic Search

An industrial application of a high speed high power variable speed drive system with a rated power of 2300 kW at 15600 RPM is presented. The drive is based upon economical and reliable components such as thyristor controlled current source inverters and the rugged and maintenance free squirrel cage induction machine. Many synergies with the standard load commutated drive technique

B. Odegard; C. A. Stulz; P. K. Steimer

1994-01-01

199

How policy variables influence the timing of applications for Social Security Disability Insurance  

Microsoft Academic Search

This article analyzes the impact of policy variables - employer accommodations, state Social Security Disability Insurance (DI) allowance rates, and DI benefits - on the timing of an application for DI benefits by workers with a work-limiting health condition starting when their health condition first begins to bother them. The analysis uses data from the Health and Retirement Study linked

Richard V. Burkhauser; J. S. Butler; Robert R Weathers II

1999-01-01

200

Multiphase Electric Machines for Variable-Speed Applications  

Microsoft Academic Search

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

Emil Levi

2008-01-01

201

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

202

Heart rate variability during sleep in detoxified alcohol-dependent males: A comparison with healthy controls  

PubMed Central

Context: Alcohol dependence can lead to autonomic neuropathy resulting in increased cardiac morbidity and mortality. This has previously been evaluated using heart-rate variability. Aims: We compared sleep heart-rate variability of alcohol-dependent patients with that of healthy controls in this study. Settings and Design: This study was conducted at NIMHANS, Bangalore. A case control study design was adopted. Materials and Methods: Sleep heart-rate variability of 20 male alcohol-dependent inpatients was recorded on the 5th day after detoxification. Sleep heart-rate variability was also recorded in 18 age- and gender-matched healthy controls. Statistical Analysis: The groups were compared using t-test for continuous variables and Chi-squared test for discrete variables. Results: Both time and frequency domain measures were significantly lower in the patients as compared to the controls, indicating decreased HRV in alcohol-dependent individuals. Conclusions: Decreased HRV in alcohol dependence indicates potential autonomic neuropathy.

Ganesha, Suhas; Thirthalli, Jagadisha; Muralidharan, Kesavan; Benegal, Vivek; Gangadhar, Bangalore N.

2013-01-01

203

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

Code of Federal Regulations, 2013 CFR

12 Banks and Banking 8 2013-01-01...mortgage and variable-rate transactions. 1026.19 Section 1026.19 Banks and Banking BUREAU...mortgage and variable-rate transactions. ...secured by a consumer's interest in a timeshare...

2013-01-01

204

Modeling autonomic regulation of cardiac function and heart rate variability in human endotoxemia  

PubMed Central

Heart rate variability (HRV), the quantification of beat-to-beat variability, has been studied as a potential prognostic marker in inflammatory diseases such as sepsis. HRV normally reflects significant levels of variability in homeostasis, which can be lost under stress. Much effort has been placed in interpreting HRV from the perspective of quantitatively understanding how stressors alter HRV dynamics, but the molecular and cellular mechanisms that give rise to both homeostatic HRV and changes in HRV have received less focus. Here, we develop a mathematical model of human endotoxemia that incorporates the oscillatory signals giving rise to HRV and their signal transduction to the heart. Connections between processes at the cellular, molecular, and neural levels are quantitatively linked to HRV. Rhythmic signals representing autonomic oscillations and circadian rhythms converge to modulate the pattern of heartbeats, and the effects of these oscillators are diminished in the acute endotoxemia response. Based on the semimechanistic model developed herein, homeostatic and acute stress responses of HRV are studied in terms of these oscillatory signals. Understanding the loss of HRV in endotoxemia serves as a step toward understanding changes in HRV observed clinically through translational applications of systems biology based on the relationship between biological processes and clinical outcomes.

Scheff, Jeremy D.; Mavroudis, Panteleimon D.; Calvano, Steven E.; Lowry, Stephen F.

2011-01-01

205

Impact of nocturnal hemodialysis on the variability of heart rate and duration of hypoxemia during sleep  

Microsoft Academic Search

Impact of nocturnal hemodialysis on the variability of heart rate and duration of hypoxemia during sleep.BackgroundNocturnal hemodialysis (NHD) alleviates uremia-related sleep apnea, a condition characterized by increased sympathetic activity and diminished heart rate (HR) variability. We tested the hypothesis that NHD reduces both hypoxemia and sympathetic neural contributions to HR variability during sleep.MethodsEpisodes of apnea and hypopnea and the duration

Christopher T. Chan; PAT HANLY; JONATHAN GABOR; PETER PICTON; ANDREAS PIERRATOS; John S. Floras

2004-01-01

206

Distributions of the ratios of independent beta variables and applications  

Microsoft Academic Search

We establish the exact expressions of X1\\/X2 and of X1\\/(X1+X2), where X1 and X2 are independent beta random variables of the first type, and provide some of their applications, in reliability and availability.

T. Pham-Gia

2000-01-01

207

Heart rate and heart rate variability in pregnant warmblood and Shetland mares as well as their fetuses  

Microsoft Academic Search

Heart rate (HR) is an important parameter of fetal well-being. In horses, HR and heart rate variability (HRV) can be determined by fetomaternal electrocardiography (ECG) from mid-pregnancy to foaling. Normal values for physiological parameters in larger breeds are often used as reference values in ponies. However, HR increases with decreasing size of the animal and in ponies is higher than

Christina Nagel; Jörg Aurich; Franziska Palm; Christine Aurich

2011-01-01

208

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.

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

209

Atrial fibrillation detection by heart rate variability in Poincare plot  

PubMed Central

Background Atrial fibrillation (AFib) is one of the prominent causes of stroke, and its risk increases with age. We need to detect AFib correctly as early as possible to avoid medical disaster because it is likely to proceed into a more serious form in short time. If we can make a portable AFib monitoring system, it will be helpful to many old people because we cannot predict when a patient will have a spasm of AFib. Methods We analyzed heart beat variability from inter-beat intervals obtained by a wavelet-based detector. We made a Poincare plot using the inter-beat intervals. By analyzing the plot, we extracted three feature measures characterizing AFib and non-AFib: the number of clusters, mean stepping increment of inter-beat intervals, and dispersion of the points around a diagonal line in the plot. We divided distribution of the number of clusters into two and calculated mean value of the lower part by k-means clustering method. We classified data whose number of clusters is more than one and less than this mean value as non-AFib data. In the other case, we tried to discriminate AFib from non-AFib using support vector machine with the other feature measures: the mean stepping increment and dispersion of the points in the Poincare plot. Results We found that Poincare plot from non-AFib data showed some pattern, while the plot from AFib data showed irregularly irregular shape. In case of non-AFib data, the definite pattern in the plot manifested itself with some limited number of clusters or closely packed one cluster. In case of AFib data, the number of clusters in the plot was one or too many. We evaluated the accuracy using leave-one-out cross-validation. Mean sensitivity and mean specificity were 91.4% and 92.9% respectively. Conclusions Because pulse beats of ventricles are less likely to be influenced by baseline wandering and noise, we used the inter-beat intervals to diagnose AFib. We visually displayed regularity of the inter-beat intervals by way of Poincare plot. We tried to design an automated algorithm which did not require any human intervention and any specific threshold, and could be installed in a portable AFib monitoring system.

2009-01-01

210

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

PubMed

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

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

2012-01-01

211

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

PubMed Central

BACKGROUND--It has been shown that heart rate variability is decreased in patients with congestive heart failure and that depressed heart rate variability is associated with a propensity to ventricular arrhythmias. Little is known, however, about heart rate variability in patients with both congestive heart failure and ventricular arrhythmias. METHODS--Spectral heart rate variability was analysed from 24 hour ambulatory electrocardiograms in 15 controls, 15 patients with non-sustained ventricular tachycardia associated with clinically normal hearts (NHVT group), and 40 patients with congestive heart failure (CHF group) secondary to either ischaemic heart disease (n = 15) or idiopathic dilated cardiomyopathy (n = 25). Of the 40 patients with congestive heart failure 15 had no appreciable ventricular arrhythmias (ventricular extrasystoles < 10 beats/h and no salvos) and formed the CHF-VA- group. Another 15 patients with congestive heart failure and non-sustained ventricular tachycardia formed the CHF-NSVT group. RESULTS--Heart rate variability was significantly lower in the CHF group than in controls (mean (SD) total frequency 23 (12) v 43 (13) ms; low frequency 12 (8) v 28 (9) ms; high frequency 8 (5) v 14 (7) ms; p < 0.001). The differences in heart rate variability between controls and the NHVT group, between ischaemic heart disease and dilated cardiomyopathy, and between the CHF-VA- and CHF-NSVT groups were not significant. In the CHF group heart rate variability was significantly related to left ventricular ejection fraction but not associated with ventricular arrhythmias. The frequency of ventricular extrasystoles was significantly related to the high frequency component of heart rate variability (r = 0.54, p < 0.05) in the NHVT group. Stepwise multiple regression analysis showed that in the CHF group, heart rate variability was predominantly related to left ventricular ejection fraction (p < 0.05). There was no significant difference in heart rate variability between survivors (n = 34) and those who died suddenly (n = 6) at one year of follow up in the CHF group. CONCLUSION--In patients with congestive heart failure, heart rate variability is significantly decreased. The depressed heart rate variability is principally related to the degree of left ventricular impairment and is independent of aetiology and the presence of ventricular arrhythmias. The data suggest that analysis of heart rate variability does not help the identification of patients with congestive heart failure at increased risk of sudden death.

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

1994-01-01

212

Heart rate variability during sympatho-excitatory challenges: Comparison between spontaneous and metronomic breathing  

Microsoft Academic Search

Respiration influences heart rate variability, leading to the suggestion that respiration should be controlled to assess autonomic\\u000a function by using heart rate variability. Clearly, control of respiration is advantageous or even essential in several experimental\\u000a circumstances. However, control of respiration, by itself, produces a small, but significant, increase in mean heart rate\\u000a and a decrease in respiratory synchronous variation in

Abhijit Patwardhan; Joyce Evans; Eugene Bruce; Charles Knapp

2001-01-01

213

Circadian rhythm changes in heart rate variability during chronic sound stress  

Microsoft Academic Search

To study the circadian rhythm changes of the heart rate variability (HRV) during chronic sound stress, Wistar rats were implanted\\u000a with telemetry transmitters and exposed to chronic ultrasound stress for 14 days. The heart rate, mean R-R intervals (mean\\u000a R-R) and body temperature were monitored hourly. The spectra of five-minute heart rate variability were plotted on a log-log\\u000a scale of

H. Takeuchi; A. Enzo; H. Minamitani

2001-01-01

214

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

Technology Transfer Automated Retrieval System (TEKTRAN)

Managing irrigation spatially can enhance water conservation and optimize water applications. Information and guidelines are needed on how to spatially precision-apply irrigation water with these systems. In this research, we investigated using soil electrical conductivity (EC) to delineate manageme...

215

Predictive power of increased heart rate versus depressed left ventricular ejection fraction and heart rate variability for risk stratification after myocardial infarction  

Microsoft Academic Search

Objectives. The aim of this study was to compare the predictive value of mean RR interval assessed from predischarge Holter recordings with that of heart rate variability and left ventricular ejection fraction for risk stratification after myocardial infarction.Background. Heart rate variability is a powerful tool for risk stratification after myocardial infarction. Although heart rate variability is related to heart rate,

Xavier Copie; Katerina Hnatkova; Anne Staunton; Lü Fei; A. John Camm; Marek Malik

1996-01-01

216

Bayesian variable selection for high dimensional generalized linear models: convergence rates of the fitted densities  

Microsoft Academic Search

Bayesian variable selection has gained much empirical success recently in a variety of applications when the number $K$ of explanatory variables $(x_1,...,x_K)$ is possibly much larger than the sample size $n$. For generalized linear models, if most of the $x_j$'s have very small effects on the response $y$, we show that it is possible to use Bayesian variable selection to

Wenxin Jiang

2007-01-01

217

Does heart rate variability change in angina pectoris patients treated with spinal cord stimulation?  

PubMed

To determine whether spinal cord stimulation has any effect on the autonomic nervous tone of the heart, heart rate variability was used as an indicator of autonomic nervous control of the heart. The components time domain and power spectral analyses of heart rate variability were measured in 21 patients with angina pectoris. Twenty-four-hour Holter recordings were obtained before and after 12 months with spinal cord stimulation. No significant attenuation of time domain or spectral components of heart rate variability analyses were found. Apparently, spinal cord stimulation does not influence the autonomic tone of the heart. PMID:9452151

Andersen, C

1998-01-01

218

78 FR 17724 - Ivy Funds Variable Insurance Portfolios, et al.; Notice of Application  

Federal Register 2010, 2011, 2012, 2013

...812-14114] Ivy Funds Variable Insurance Portfolios, et al.; Notice of Application March...Applicants: Ivy Funds Variable Insurance Portfolios (the ``Trust''), Waddell & Reed...Funds may invest. Applicants' Legal Analysis 1. Section 12(d)(1)(A) of...

2013-03-22

219

Has Non-linear Analysis of Heart Rate Variability Any Practical Value?  

Microsoft Academic Search

In this article, we focus on the recent advances in the assessment of the heart rate variability (HRV). Speci~cally, we review some of the new methods to assess heart rate dynamics based on non-linear mathematics and chaos theory. These methods do not quantify the actual magnitude of HRV but describe the complexity and dynamics of heart rate _uctuation. Although the

Antti E. Hedman; Juha E. K. Hartikainen

1999-01-01

220

The effect of artifact correction on spectral estimates of heart rate variability  

Microsoft Academic Search

Spectral analysis of fetal heart rate variability might offer additional information that can be used for assessing the fetal condition more reliably. Clinical recordings of fetal heart rate are usually contaminated by artifacts. These artifacts can be detected and corrected or removed, but this can affect the spectral estimates obtained from the heart rate data. To determine what level of

Chris Peters; Rik Vullings; Jan Bergmans; Guid Oei; Pieter Wijn

2008-01-01

221

Joint optimisation of maintenance and production policies considering random demand and variable production rate  

Microsoft Academic Search

This paper deals with a randomly failing manufacturing system M1 which has to satisfy a random demand during a finite horizon given a required service level. To help meet this demand, subcontracting is used through another production system M2. M1 operates with a variable production rate and its failure rate depends on both time and the production rate. In these

Souheil Ayed; Dellagi Sofiene; Rezg Nidhal

2011-01-01

222

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

PubMed Central

BACKGROUND--Although heart rate variability has already been studied in survivors of sudden cardiac death secondary to coronary artery disease, an assessment of heart rate variability in survivors of sudden cardiac death not associated with coronary artery disease has not been made. METHODS--10 patients with aborted sudden cardiac death not associated with coronary artery disease (seven patients with primary ventricular fibrillation and three with unclassified mild cardiomyopathy) underwent two channel 24 hour Holter monitoring in a drug free state. All subjects were in sinus rhythm and had normal atrioventricular conduction and normal cardiac function. Spectral heart rate variability was analysed on a Holter analysis system and was expressed as total (0.01-1.00 Hz), low (0.04-0.15 Hz) and high (0.15-0.40 Hz) frequency components for each hour. Heart rate variability index was calculated for the 24 hour periods. 10 age and sex matched healthy subjects were taken as a control group. RESULTS--The spectral heart rate variability over 24 hours was significantly lower in survivors of sudden cardiac death than in controls (total 38(15) v 48(14) ms; low, 25(11) v 32(13) ms; and high, 13(8) v 18(8) ms; p < 0.05 for all comparisons). The differences in the ratio of low/high (2.19(0.76) v 1.98(0.50), p = 0.132), mean heart rate (77(12) v 69(12) beats/min, p = 0.070), and heart rate variability index (38(12) v 44(16), p = 0.287) over 24 hours between survivors of sudden cardiac death and controls did not reach significance. Comparisons of the hourly heart rate variability over the 24 hour period between the two groups showed that the differences in all components of heart rate variability, low/high ratio and mean heart rate were highly significant. Furthermore, there was no significant difference in the maximum hourly heart rate variability over the 24 hour period. The minimum hourly heart rate variability was, however, significantly lower in survivors of sudden cardiac death than in controls (total, 20(8) v 28(4) ms; low, 12(6) v 17(3) ms; high, 6(2) v 8(2) ms; p < 0.05 for all comparisons). CONCLUSIONS--These findings suggest that there is abnormal autonomic influence on the heart in patients without coronary artery disease at risk of sudden cardiac death. Hourly analysis of heart rate variability throughout the 24 hour period may provide additional information important in the identification of high risk patients.

Fei, L.; Anderson, M. H.; Katritsis, D.; Sneddon, J.; Statters, D. J.; Malik, M.; Camm, A. J.

1994-01-01

223

A variable inductor for power applications using coupled circuits  

SciTech Connect

In this paper, a variable inductor suitable for power system applications is presented. The inductor variation is based on varying the number of turns in a secondary circuit using triac switches. Unlike thyristor-controlled reactors, the inductance of the proposed reactor is varied in steps but without causing distortion in the inductor current. Mathematical expression for the effective impedance of the reactor is developed. Theoretical results are compared with those obtained experimentally using a test model.

Lashine, A.E. (Dept. of Electrical Engineering, Menoufia Univ., Shebin El-Kom (Egypt))

1992-01-01

224

Use of variable frequency drives for extruder application  

Microsoft Academic Search

This paper describes a case study of replacing an eddy current clutch (ECC) with a modern medium voltage variable frequency drive (VFD) for 2250 HP extruder application. It covers key issues, justification, factory and field measurements of torque-speed profile through 0.5-60 Hz as well as power quality analysis. The paper reviews manufacturers' capability to build medium voltage VFDs that produce

Robert Hanna; Scott Randall

1999-01-01

225

Variable-rate irrigation management using an expert system in the eastern coastal plain  

Technology Transfer Automated Retrieval System (TEKTRAN)

Variable rate irrigation (VRI) systems have the potential to conserve water by spatially allocating limited water resources. These water savings become more important as urban, industrial, and environmental sectors compete with agriculture for available water. In this study, we conducted variable ra...

226

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

Microsoft Academic Search

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

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

1995-01-01

227

Geomagnetic disturbance associated with decrease in heart rate variability in a subarctic area  

Microsoft Academic Search

Background. Physical environmental variables, such as the natural variation in the geomagnetic field in and around the earth, influence biological processes and human health. The effect of geomagnetic disturbances on heart rate variability (HRV) in healthy students in a subarctic area is studied herein. Subjects and methods. Seven-day records by Holter ECG were obtained from eight clinically healthy subjects in

K. Otsuka; G. Cornélissen; A. Weydahl; B. Holmeslet; T. L. Hansen; M. Shinagawa; Y. Kubo; Y. Nishimura; K. Omori; S. Yano; F. Halberg

2000-01-01

228

Dipping and Variability of Blood Pressure and Heart Rate at Night Are Heritable Traits  

Microsoft Academic Search

Background: Blunted nocturnal blood pressure dipping (NBPD) as well as high variability in blood pressure (BPV) and low variability in heart rate (HRV), are associated with increased cardiovascular morbidity and mortality. The aim of this study was to determine whether these traits are heritable.Methods: We studied 260 healthy siblings without antihypertensive drugs from 118 Swedish families. The BPV and HRV

Cristiano Fava; Philippe Burri; Peter Almgren; Guido Arcaro; Leif Groop; U. Lennart Hulthén; Olle Melander

2005-01-01

229

Natural killer cell and proinflammatory cytokine responses to mental stress: associations with heart rate and heart rate variability  

Microsoft Academic Search

Associations between natural killer (NK) cell, proinflammatory cytokine stress responsivity, and cardiac autonomic responses (indexed by heart rate and heart rate variability) were assessed in 211 middle-aged men and women. Blood was drawn at baseline, immediately following color–word interference and mirror tracing tasks for the assessment of NK cell numbers, and 45 min post-stress for assessing plasma interleukin 6 (IL-6)

Natalie Owen; Andrew Steptoe

2003-01-01

230

[Design of hand-held heart rate variability acquisition and analysis system].  

PubMed

A design of handheld heart rate variability acquisition and analysis system is proposed. The system collects and stores the patient's ECG every five minutes through both hands touching on the electrodes, and then -uploads data to a PC through USB port. The system uses software written in LabVIEW to analyze heart rate variability parameters, The parameters calculated function is programmed and generated to components in Matlab. PMID:23189641

Li, Kaiyuan; Wang, Buqing; Wang, Weidong

2012-07-01

231

The effect of ventilation on spectral analysis of heart rate and blood pressure variability during exercise  

Microsoft Academic Search

Heart rate variability (HRV) and systolic blood pressure variability (BPV) during incremental exercise at 50, 75, and 100% of previously determined ventilatory threshold (VT) were compared to that of resting controlled breathing (CB) in 12 healthy subjects. CB was matched with exercise-associated respiratory rate, tidal volume, and end-tidal CO2 for all stages of exercise. Power in the low frequency (LF,

Matthew N. Bartels; Sanja Jelic; Pakkay Ngai; Gregory Gates; Douglas Newandee; Stanley S. Reisman; Robert C. Basner; Ronald E. De Meersman

2004-01-01

232

Studies on Heart Rate Variability in Patients with Acute Myocardial Infarction  

Microsoft Academic Search

Background:Heart rate variability(HRV represents one of the methods of examining the function of autonomic nervous system. Many patients with acute myocardial infarction show evidence of autonomic disturbance during the acute phase of the attack and reduced heart rate variability is a significant predictor of mortality in patients after acute myocardial infarction. Method:The study groups included 25 patients admitted to our

Ho Soon Lee; Yong Seok Choi; Seong Woo Han; Woo Jung Park; Young-Cheoul Doo; Dong Jin Oh; Kyu Hyung Ryu; Yung Lee

1997-01-01

233

Ieart Rate Variability of Recently Concussed Athletes at Rest and Exercise  

Microsoft Academic Search

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

BRENT GALL; WADE PARKHOUSE; DAVID GOODMAN

234

Real-time variable feed rate NURBS curve interpolator for CNC machining  

Microsoft Academic Search

This paper presents a real-time control algorithm based on Taylor’s expansion for implementing variable feed rate non-uniform rational B-spline (NURBS) curve interpolators using a digital signal processor for precision CNC machining. To efficiently compute the NURBS curve and its derivatives in real-time, an effective method is proposed. The variable feed rate NURBS curve interpolator can be used to realise the

C.-W. Cheng; M.-C. Tsai

2004-01-01

235

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

Microsoft Academic Search

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

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

2004-01-01

236

When can environmental variability benefit population growth? Counterintuitive effects of nonlinearities in vital rates.  

PubMed

Using models for unstructured populations, we investigate the effect of environmental variability on population growth when the environment affects vital rates through nonlinear functions. We focus here especially on interannual variation in food resources availability, for which sigmoid functions are relevant. Considering first unregulated populations in stochastic environments, we show that classic sigmoid annual growth rates cannot lead to positive effects of increased environmental variability on population growth. This is true even when the temporal average of food availability is low, and Jensen's inequality predicts an increased arithmetic mean of the annual growth rate. The result is due to the log-concavity of many sigmoid (and other accelerating) functions, as convexity of the logarithm of the annual growth rate is needed for positive effects of variability to appear. Then, separating the effects of a food availability variable on reproduction and survival rates, we show that populations with less sensitive survival rate to food are more likely to benefit from food variability-as opposed to populations that have survival rates accelerating with food availability, which is rather counterintuitive given Jensen's inequality. Again, this is explained by log-convexity properties of nonlinear functions. We further extend these results to regulated populations, in which similar positive effects of food variability can affect average population size. Positive variability effects seem however more likely to occur in regulated populations. Finally, we extend our results to stage-structured populations. We connect to the previous work showing positive effects of environmental variability with matrix models, and show that these effects are well captured by simpler unstructured models. PMID:23906589

Barraquand, Frédéric; Yoccoz, Nigel G

2013-07-29

237

The ultraviolet/optical variability of steep-spectrum radio quasars: the change in accretion rate?  

NASA Astrophysics Data System (ADS)

Context. The steep-spectrum radio quasars (SSRQs) are powerful radio sources, with thermal emission from accretion disk and jet nonthermal emission both likely contributing to the ultraviolet (UV)/optical luminosity; however, the former may play a dominant role. Since the UV/optical variability of SSRQs has been poorly studied, little is known about the mechanism of their variability. Aims: We investigate the mechanism of the UV/optical variability of SSRQs. Methods: A sample of eighteen SSRQs was established in SDSS Stripe 82 region in our previous works, in which the flux and spectral variability were studied. In this work, we construct the flux-flux diagram using SDSS u and i multi-epoch data for these eighteen SSRQs. The standard accretion disk model is used to fit the flux-flux variations, in order to explore the variability mechanism. Results: The model fit to flux-flux diagram are tuned with fixed black hole mass and varying accretion rate. We find that the flux-flux diagram of all our SSRQs can be qualitatively described by the standard accretion disk model with a change in the accretion rate. Although nonthermal jet power-law emission can also qualitatively reproduce the variability, the reasonable accretion rates and black hole masses required to fit the flux-flux variations suggest that a disk emission with variable accretion rate is a plausible description of the data. Full Fig. 1 is available in electronic form at http://www.aanda.org

Gu, M. F.; Li, S.-L.

2013-06-01

238

Elevated heart rate variability in physically active young and older adult women.  

PubMed

1. Low heart rate variability is associated with an increased risk of cardiac sudden death, coronary heart disease and all-cause mortality. We have previously shown that physically active postmenopausal women demonstrate higher levels of heart rate variability and cardiac baroreflex sensitivity compared to their sedentary peers. The purpose of the present prospective study was to test the hypothesis that heart rate variability and cardiac baroreflex sensitivity would be reduced with age in sedentary but not physically active women. To accomplish this, we measured heart rate variability (both time and frequency domain) and spontaneous cardiac baroreflex sensitivity (SBRS, sequence method) in the sitting posture in 23 sedentary women [11 premenopausal and 12 postmenopausal (age, 28 +/- 1 and 61 +/- 2 years; VO2max, 35.3 +/- 1.4 and 21.7 +/- 1.5 ml.min-1.kg-1 respectively] and in 22 physically active women [12 premenopausal and 10 postmenopausal (age, 31 +/- 1 and 59 +/- 2 years; VO2max, 52.5 +/- 1.4 and 39.7 +/- 1.8 ml.min-1.kg-1)]. 2. The S.D. of the R-R interval (time domain) was reduced (P < 0.05) with age in both sedentary (52 +/- 6 versus 33 +/- 4 ms) and physically active women (72 +/- 8 versus 49 +/- 9 ms). The high-frequency power (3740 +/- 1527 versus 915 +/- 188 and 9516 +/- 2849 versus 2803 +/- 1083 ms2/Hz), total power of heart rate variability and SBRS (11 +/- 2 versus 7 +/- 2 and 19 +/- 3 versus 13 +/- 2 ms/mmHg) also demonstrated similar age-related reductions in sedentary and physically active women, respectively (all P < 0.05). The S.D. of the R-R interval, high-frequency and total power of heart rate variability, and SBRS were higher (all P < 0.05) in the physically active compared with the sedentary women at any age. There was no significant influence of age or physical activity status on the low-frequency power of heart rate variability. In addition, no significant differences in any of the time or frequency domain measures of heart rate variability or SBRS were observed in users compared with non-users of hormone replacement therapy. 3. The results of the present study suggest that heart rate variability and cardiac baroreflex sensitivity decline similarly with age in healthy sedentary and physically active women. However, physically active women demonstrate higher levels of heart rate variability and cardiac baroreflex sensitivity compared with their sedentary peers, regardless of age. PMID:9854454

Davy, K P; DeSouza, C A; Jones, P P; Seals, D R

1998-06-01

239

An Integrated Account of the Effects of Acoustic Variability in First Language and Second Language: Evidence from Amplitude, Fundamental Frequency, and Speaking Rate Variability  

ERIC Educational Resources Information Center

|This study examined how three different sources of stimulus variability--overall amplitude, fundamental frequency, and speaking rate--affect second language (L2) vocabulary learning. Native English speakers learned Spanish words in presentation formats with no variability, moderate variability, and high variability. Dependent measures were…

Sommers, Mitchell S.; Barcroft, Joe

2007-01-01

240

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

241

Rating plastic piping systems for pressures application  

Microsoft Academic Search

The Plastic Pipe Institute's Hydrostatic Stress Committee is considering a refinement to ASTM Method D 2837 for obtaining hydrostatic design bases for thermoplastic pipe materials. Called the rate process method, this refinement would (1) expand D 2837 to include fittings and joints, (2) estimate service life at the intended use pressure, (3) test failure mechanisms similar to field observations, and

R. R. Geoffroy; I. K. DeBlieu

1983-01-01

242

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

Microsoft Academic Search

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

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

2005-01-01

243

Heart rate variability effect on the myocyte action potential duration restitution: Insights from switched systems theory  

Microsoft Academic Search

The physiological heart rate presents a stochastic behavior known as heart rate variability (HRV). In this framework the influence of HRV on the action potential duration (APD) of the atrial myocyte is analyzed in a computer model. We have found that introducing HRV into the myocyte action potential model decreases the APD of the extra beat S2 in an S1-S2

Hila Dvir; Sharon Zlochiver

2011-01-01

244

Maximum likelihood phylogenetic estimation from DNA sequences with variable rates over sites: Approximate methods  

Microsoft Academic Search

Two approximate methods are proposed for maximum likelihood phylogenetic estimation, which allow variable rates of substitution across nucleotide sites. Three data sets with quite different characteristics were analyzed to examine empirically the performance of these methods. The first, called the “discrete gamma model,” uses several categories of rates to approximate the gamma distribution, with equal probability for each category. The

Ziheng Yang

1994-01-01

245

Linear and nonlinear heart rate variability risk stratification in heart failure patients  

Microsoft Academic Search

Chronic heart failure (CHF) is a major and growing public health concern (~23 million people worldwide) with five-year survival rates of 25% in men and 38% in women. Objective of this study was to investigate whether linear and nonlinear heart rate variability (HRV) indices enhance risk prediction in patients with CHF. To discriminate between low risk (stable condition, N =

A. Voss; R. Schroeder; M. Vallverdu; I. Cygankiewicz; R. Vazquez; A. Bayes de Luna; P. Caminal

2008-01-01

246

A simple model for the simulation of low frequency heart rate variability waves  

Microsoft Academic Search

The purpose of this study was mathematical modeling of the low frequency heart rate variability wave (LFHR) and its response to isoproterenol (ISP) infusion. In a previous study the authors found that the steady-state HR can be described as a hyperbolic power function of the steady-state ISP flow rate. This dependency was coupled with a first order difference equation to

R. J. Leor-Librach; B. Z. Bobrovsky; S. Eliash; E. Kaplinsky

2000-01-01

247

Cardiovascular Endurance and Heart Rate Variability in Adolescents With Type 1 or Type 2 Diabetes  

Microsoft Academic Search

Background. Incidence rates of both type 1 and type 2 diabetes mellitus (DM) are increasing in youth and may eventually contribute to premature heart disease in early adulthood. This investigation explored the influence of type of diabetes, gender, body mass index (BMI), metabolic control (HbA1c), exercise beliefs and physical activity on cardiovascular endurance (CE), and heart rate variability (HRV). Differences

Melissa Spezia Faulkner; Laurie Quinn; James H. Rimmer; Barry H. Rich

2005-01-01

248

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

SciTech Connect

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

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

2011-08-15

249

Rate of Mutual Information Between Coarse-Grained Non-Markovian Variables  

NASA Astrophysics Data System (ADS)

The problem of calculating the rate of mutual information between two coarse-grained variables that together specify a continuous time Markov process is addressed. As a main obstacle, the coarse-grained variables are in general non-Markovian, therefore, an expression for their Shannon entropy rates in terms of the stationary probability distribution is not known. A numerical method to estimate the Shannon entropy rate of continuous time hidden-Markov processes from a single time series is developed. With this method the rate of mutual information can be determined numerically. Moreover, an analytical upper bound on the rate of mutual information is calculated for a class of Markov processes for which the transition rates have a bipartite character. Our general results are illustrated with explicit calculations for four-state networks.

Barato, Andre C.; Hartich, David; Seifert, Udo

2013-11-01

250

An infrared high rate video imager for various space applications  

Microsoft Academic Search

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

Hâkan Svedhem; Detlef Koschny

2010-01-01

251

Removal of Respiratory Influences From Heart Rate Variability in Stress Monitoring  

Microsoft Academic Search

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

Jongyoon Choi; Ricardo Gutierrez-Osuna

2011-01-01

252

Diurnal variability in rate of emission of nitrous oxide from soils  

Microsoft Academic Search

Diurnal variability in the rate of emission of nitrous oxide (NâO) from Iowa soils was studied by using a chamber technique to measure the NâO emission rates at sites on fertilized and unfertilized soils at 1- or 2-h intervals for periods of from 1 to 5 d. The coefficients of variation for the rates of NâO emission observed at these

A. M. Blackmer; S. G. Robbins; J. M. Bremner

1982-01-01

253

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

ERIC Educational Resources Information Center

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

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

2011-01-01

254

Cognitive Performance and Heart Rate Variability: The Influence of Fitness Level  

PubMed Central

In the present study, we investigated the relation between cognitive performance and heart rate variability as a function of fitness level. We measured the effect of three cognitive tasks (the psychomotor vigilance task, a temporal orienting task, and a duration discrimination task) on the heart rate variability of two groups of participants: a high-fit group and a low-fit group. Two major novel findings emerged from this study. First, the lowest values of heart rate variability were found during performance of the duration discrimination task, compared to the other two tasks. Second, the results showed a decrement in heart rate variability as a function of the time on task, although only in the low-fit group. Moreover, the high-fit group showed overall faster reaction times than the low-fit group in the psychomotor vigilance task, while there were not significant differences in performance between the two groups of participants in the other two cognitive tasks. In sum, our results highlighted the influence of cognitive processing on heart rate variability. Importantly, both behavioral and physiological results suggested that the main benefit obtained as a result of fitness level appeared to be associated with processes involving sustained attention.

Luque-Casado, Antonio; Zabala, Mikel; Morales, Esther; Mateo-March, Manuel; Sanabria, Daniel

2013-01-01

255

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

Microsoft Academic Search

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

Gianfranco Pergher; Rino Gubiani

1995-01-01

256

Macroeconomic Influences on Social Security Disability Insurance Application Rates  

Microsoft Academic Search

It is generally accepted that Social Security Disability Insurance (DI) Program application rates are influenced by the macro economy. DI program data and previous research indicate that a disproportionate number of beneficiaries (past applicants) are less-educated, with low-skill employment histories. These applicants, while they worked, were likely to intertemporally shift their durables consumption expenditures in response to tight budget constraints

Dana A. Kerr; Bert J. Smoluk

2011-01-01

257

Vagally mediated heart rate variability and heart rate entropy as predictors of treatment outcome in flight phobia.  

PubMed

In the present study a computer-assisted exposure-based treatment was applied to 54 flight phobics and the predictive role of vagally mediated heart rate (HR) variability (high frequency, 0.15-0.4 Hz band power) and heart rate entropy (HR time series sample entropy) on treatment outcome was investigated. Both physiological measures were taken under controlled breathing at 0.2 Hz and during exposure to a fearful sequence of audiovisual stimuli. Hierarchical regression analyses were conducted to assess the predictive power of these variables in these conditions on treatment self-report measures at the end of treatment and at 6 months follow-up, as well as on the behavioral treatment outcome (i.e. flying at the end of treatment). Regression models predicting significant amounts of outcome variance could be built only when HR entropy was added to the HR variability measure in a second step of the regression analyses. HR variability alone was not found to be a good predictor of neither self-reported nor behavioral treatment outcomes. PMID:17765387

Bornas, Xavier; Llabrés, Jordi; Tortella-Feliu, Miquel; Fullana, Miquel A; Montoya, Pedro; López, Ana; Noguera, Miquel; Gelabert, Joan M

2007-07-28

258

[The relation of heart rate variability and a dispersive electrocardiogram mapping indicators in human during fixed rate breathing test].  

PubMed

Association of heart rate variability and dispersive electrocardiogram mapping indicators in women during fixed rate breathing test by the period of 10 s are observed. Disturbance of depolarization processes in auricles that show an increase in dispersive group G1 is associated with expressed vagal reserves deficiency. Intensity of control centralization level by heart rhythm and humoral-metabolic influences both in a background and at active breathing can cause intensifying of high-speed microamplitude characteristics of initial front of ventricles depolarization that reflect an increase of dispersive group G9. PMID:23013004

Poskotnikova, L V; Zenchenko, T A; Medvedeva, A A; Ovsiankina, M A

2012-01-01

259

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

Microsoft Academic Search

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

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

2010-01-01

260

Non-baroreflex mediated heart rate variability causes overestimation of baroreflex sensitivity  

Microsoft Academic Search

Spectral assessment of baroreflex sensitivity (BRS) is hampered by non-baroreflex mediated heart rate variability (HRV), which adds to the baroreflex mediated HRV. Relating HRV (baroreflex output) to blood pressure variability (BPV, baroreflex input) may therefore yield BRS values that are too large. The authors propose to overcome this problem by computing BRS in the Mayer waves (0.05-0.15 Hz), while keeping

J. Frederiks; C. A. Swenne; B. J. TenVoorde; N. Honzikova; J. V. Levert; A. C. Maan; M. J. Schalij; A. V. G. Bruschke

1997-01-01

261

Development of multiscale complexity and multifractality of fetal heart rate variability.  

PubMed

During fetal development a complex system grows and coordination over multiple time scales is formed towards an integrated behavior of the organism. Since essential cardiovascular and associated coordination is mediated by the autonomic nervous system (ANS) and the ANS activity is reflected in recordable heart rate patterns, multiscale heart rate analysis is a tool predestinated for the diagnosis of prenatal maturation. The analyses over multiple time scales requires sufficiently long data sets while the recordings of fetal heart rate as well as the behavioral states studied are themselves short. Care must be taken that the analysis methods used are appropriate for short data lengths. We investigated multiscale entropy and multifractal scaling exponents from 30minute recordings of 27 normal fetuses, aged between 23 and 38weeks of gestational age (WGA) during the quiet state. In multiscale entropy, we found complexity lower than that of non-correlated white noise over all 20 coarse graining time scales investigated. Significant maturation age related complexity increase was strongest expressed at scale 2, both using sample entropy and generalized mutual information as complexity estimates. Multiscale multifractal analysis (MMA) in which the Hurst surface h(q,s) is calculated, where q is the multifractal parameter and s is the scale, was applied to the fetal heart rate data. MMA is a method derived from detrended fluctuation analysis (DFA). We modified the base algorithm of MMA to be applicable for short time series analysis using overlapping data windows and a reduction of the scale range. We looked for such q and s for which the Hurst exponent h(q,s) is most correlated with gestational age. We used this value of the Hurst exponent to predict the gestational age based only on fetal heart rate variability properties. Comparison with the true age of the fetus gave satisfying results (error 2.17±3.29weeks; p<0.001; R(2)=0.52). In addition, we found that the normally used DFA scale range is non-optimal for fetal age evaluation. We conclude that 30min recordings are appropriate and sufficient for assessing fetal age by multiscale entropy and multiscale multifractal analysis. The predominant prognostic role of scale 2 heart beats for MSE and scale 39 heart beats (at q=-0.7) for MMA cannot be explored neither by single scale complexity measures nor by standard detrended fluctuation analysis. PMID:23466040

Giera?towski, Jan; Hoyer, Dirk; Tetschke, Florian; Nowack, Samuel; Schneider, Uwe; Zebrowski, Jan

2013-03-07

262

Automatic detection and quantification of sleep apnea using heart rate variability.  

PubMed

Detection of sleep apnea using electrocardiographic (ECG) parameters is noninvasive and inexpensive. Our approach is based on the hypothesis that the patient's sleep-wake cycle during episodes of sleep apnea modulates heart rate (HR) oscillations. These HR oscillations appear as low-frequency fluctuations of instantaneous HR (IHR) and can be detected using HR variability analysis in the frequency domain. The purpose of this study was to evaluate the efficacy of our ECG-based algorithm for sleep apnea detection and quantification. The algorithm first detects normal QRS complexes and R-R intervals used to derive IHR and to estimate its spectral power in several frequency ranges. A quadratic classifier, trained on the learning set, uses 2 parameters to classify the 1-minute epoch in the middle of each 6-minute window as either apneic or normal. The windows are advanced by 1-minute steps, and the classification process is repeated. As a measure of quantification, the algorithm correctly classified 84.7% of all the 1-minute epochs in the evaluation database; and as a measure of the accuracy of apnea classification, the algorithm correctly classified all 30 test recordings in the evaluation database either as apneic or normal. Our sleep apnea detection algorithm based on analysis of a single-lead ECG provides accurate apnea detection and quantification. Because of its noninvasive and low-cost nature, this algorithm has the potential for numerous applications in sleep medicine. PMID:20719334

Babaeizadeh, Saeed; White, David P; Pittman, Stephen D; Zhou, Sophia H

2010-08-17

263

Effects of nitroglycerin on fractal features of short-term heart rate and blood pressure variability  

Microsoft Academic Search

Purpose. We investigated the effect of nitroglycerin(NTG) on fractal features of short-term heart rate variability (HRV) and blood\\u000a pressure variability (BPV) using coarse-graining spectral analysis (CGSA).\\u000a \\u000a \\u000a Method. Nine healthy young volunteers participated in this study. Five-minute recordings of electrocardiogram and blood pressure\\u000a estimated by photoplethysmograph were made during stepwise NTG infusions of 0.2, 0.4, 0.8, and 1.6 ?g·kg?1·min?1 under rate-controlled

Keiji Satoh; Junken Koh; Yoshihiro Kosaka

1999-01-01

264

Distribution Characteristics of Global Significant Earthquakes and Possible Connection Between Earthquakes and Earth's Variable Rotation Rate  

NASA Astrophysics Data System (ADS)

Based on global earthquake catalog released from Paula K. Dunbar et al., the authors investigate distribution characteristics of global significant earthquakes (Ms >=7.5) during 1832-1994, and discuss possible connection between global earthquakes and Earth's variable rotation rate. It is shown that spatial distribution characteristics of earthquakes in this catalog are similar to modern observations, mainly locating in circum-Pacific and Mediterranean-Himalayan seismic belt, and Earth variable rotation rate is highly related to the number of global great earthquakes.

Ma, Li-Hua; Han, Yan-Ben; Yin, Zhi-Qiang

2007-12-01

265

Comparison of heart rate variability signal features derived from electrocardiography and photoplethysmography in healthy individuals.  

PubMed

The heart rate variability (HRV) signal is indicative of autonomic regulation of the heart rate (HR). It could be used as a noninvasive marker in monitoring the physiological state of an individual. Currently, the primary method of deriving the HRV signal is to acquire the electrocardiogram (ECG) signal, apply appropriate QRS detection algorithms to locate the R wave and its peak, find the RR intervals, and perform suitable interpolation and resampling to produce a uniformly sampled tachogram. This process could sometimes result in errors in the HRV signal due to drift, electromagnetic and biologic interference, and the complex morphology of the ECG signal. The photoplethysmographic (PPG) signal has the potential to eliminate the problems with the ECG signal to derive the HRV signal. To investigate this point, a PDA-based system was developed to simultaneously record ECG and PPG signals to facilitate accurately controlled sampling and recording durations. Two healthy young volunteers participated in this pilot study to evaluate the applicability of our approach. To improve data quality, ECG and PPG recordings were acquired three times/subject. A comparison between different features of the HRV signals derived from both methods was performed to test the validity of using PPG signals in HRV analysis. We used autoregressive (AR) modeling, Poincare' plots, cross correlation, standard deviation, arithmetic mean, skewness, kurtosis, and approximate entropy (ApEn) to derive and compare different measures from both ECG and PPG signals. This study demonstrated that our PDA-based system was a convenient and reliable means for acquisition of PPG-derived and ECG-derived HRV signals. The excellent agreement between different measures of HRV signals acquired from both methods provides potential support for the idea of using PPGs instead of ECGs in HRV signal derivation and analysis in ambulatory cardiac monitoring of healthy individuals. PMID:17946618

Bolanos, M; Nazeran, H; Haltiwanger, E

2006-01-01

266

Variability in case-mix adjusted in-hospital cardiac arrest rates  

PubMed Central

Background It is unknown how in-hospital cardiac arrest (IHCA) rates vary across hospitals and predictors of variability. Objectives Measure variability in IHCA across hospitals and determine if hospital-level factors predict differences in case-mix adjusted event rates. Research design Get with the Guidelines Resuscitation (GWTG-R) (n=433 hospitals) was used to identify IHCA events between 2003-2007. The American Hospital Association survey, Medicare, and US Census were used to obtain detailed information about GWTG-R hospitals. Subjects adult patients with IHCA Measures Case-mix adjusted predicted IHCA rates were calculated for each hospital and variability across hospitals was compared. A regression model was used to predict case-mix adjusted event rates using hospital measures of volume, nurse-to-bed ratio, percent ICU beds, palliative care services, urban designation, volume of black patients, income, trauma designation, academic designation, cardiac surgery capability and a patient risk score. Results We evaluated 103,117 adult IHCAs at 433 US hospitals. The case mix adjusted IHCA event rate was highly variable across hospitals, median 1/1000 bed days (interquartile range: 0.7-1.3 events/1000 bed-days). In a multivariable regression model, case-mix adjusted IHCA event rates were highest in urban hospitals (rate ratio [RR] 1.1, 95% confidence interval [CI] 1.0-1.3, p=0.03) and hospitals with higher proportions of black patients (RR 1.2, 95% CI 1.0-1.3, p=0.01) and lower in larger hospitals (RR 0.54, 95% CI 0.45-0.66, p<.0001). Conclusion Case-mix adjusted IHCA event rates varied considerably across hospitals. Several hospital factors associated with higher IHCA event rates were consistent with factors often linked with lower hospital quality of care.

Merchant, Raina M.; Yang, Lin; Becker, Lance B.; Berg, Robert A.; Nadkarni, Vinay; Nichol, Graham; Carr, Brendan G.; Mitra, Nandita; Bradley, Steven M.; Abella, Benjamin S.; Groeneveld, Peter W.

2011-01-01

267

The predictive value of low heart rate and heart rate variability during stress for reoffending in delinquent male adolescents.  

PubMed

Low autonomic (re)activity is a consistent correlate of antisocial behavior in juveniles. However, longitudinal research relating autonomic measures to persistent antisocial behavior has remained scarce. Therefore, in the present study we examined the predictive value of heart rate (HR) and heart rate variability (HRV, often studied as respiratory sinus arrhythmia) for reoffending in delinquent male adolescents. At initial assessment, HR and HRV were measured at rest and in response to a public speaking task. Registered reoffending was assessed after 5-year follow-up. Attenuated HR response and stronger HRV response to stress predicted higher reoffending rates. Results provide evidence that HR/HRV reactivity are neurobiological markers for persistent juvenile antisocial behavior. Although effect sizes were small to moderate, our findings underscore the consistency of the relationship between autonomic markers and antisocial behavior. PMID:21824152

De Vries-Bouw, Marjan; Popma, Arne; Vermeiren, Robert; Doreleijers, Theo A H; Van De Ven, Peter M; Jansen, Lucres M C

2011-08-08

268

Heart rate variability and pain: associations of two interrelated homeostatic processes.  

PubMed

Between-person variability in pain sensitivity remains poorly understood. Given a conceptualization of pain as a homeostatic emotion, we hypothesized inverse associations between measures of resting heart rate variability (HRV), an index of autonomic regulation of heart rate that has been linked to emotionality, and sensitivity to subsequently administered thermal pain. Resting electrocardiography was collected, and frequency-domain measures of HRV were derived through spectral analysis. Fifty-nine right-handed participants provided ratings of pain intensity and unpleasantness following exposure to 4 degrees C thermal pain stimulation, and indicated their thresholds for barely noticeable and moderate pain during three exposures to decreasing temperature. Greater low-frequency HRV was associated with lower ratings of 4 degrees C pain unpleasantness and higher thresholds for barely noticeable and moderate pain. High-frequency HRV was unrelated to measures of pain sensitivity. Findings suggest pain sensitivity is influenced by characteristics of a central homeostatic system also involved in emotion. PMID:18023960

Appelhans, Bradley M; Luecken, Linda J

2007-10-12

269

Comparison of heart and respiratory rate variability measures using an intermittent incremental submaximal exercise model.  

PubMed

To better understand the alterations in cardiorespiratory variability during exercise, the present study characterized the patterns of change in heart rate variability (HRV), respiratory rate variability (RRV), and combined cardiorespiratory variability (HRV-RRV) during an intermittent incremental submaximal exercise model. Six males and six females completed a submaximal exercise protocol consisting of an initial baseline resting period followed by three 10-min bouts of exercise at 20%, 40%, and 60% of maximal aerobic capacity (V?O2max). The R-R interval and interbreath interval variability were measured at baseline rest and throughout the submaximal exercise. A group of 93 HRV, 83 RRV, and 28 HRV-RRV measures of variability were tracked over time through a windowed analysis using a 5-min window size and 30-s window step. A total of 91 HRV measures were able to detect the presence of exercise, whereas only 46 RRV and 3 HRV-RRV measures were able to detect the same stimulus. Moreover, there was a loss of overall HRV and RRV, loss of complexity of HRV and RRV, and loss of parasympathetic modulation of HRV (up to 40% V?O2max) with exercise. Conflicting changes in scale-invariant structure of HRV and RRV with increases in exercise intensity were also observed. In summary, in this simultaneous evaluation of HRV and RRV, we found more consistent changes across HRV metrics compared with RRV and HRV-RRV. PMID:24053520

Barrera-Ramirez, Juliana; Bravi, Andrea; Green, Geoffrey; Seely, Andrew J; Kenny, Glen P

2013-05-16

270

Aging reduces complexity of heart rate variability assessed by conditional entropy and symbolic analysis  

Microsoft Academic Search

Increasing age is associated with a reduction in overall heart rate variability as well as changes in complexity of physiologic\\u000a dynamics. The aim of this study was to verify if the alterations in autonomic modulation of heart rate caused by the aging\\u000a process could be detected by Shannon entropy (SE), conditional entropy (CE) and symbolic analysis (SA). Complexity analysis\\u000a was

Anielle C. M. Takahashi; Alberto Porta; Ruth C. Melo; Robison J. Quitério; Ester da Silva; Audrey Borghi-Silva; Eleonora Tobaldini; Nicola Montano; Aparecida M. Catai

271

Interannual variability in methane growth rate simulated with a coupled Ocean-Atmosphere-Chemistry model  

Microsoft Academic Search

(1) We assess the contribution made to the interannual variability of the global methane accumulation rate from its atmospheric sink using the STOCHEM tropospheric chemistry model coupled to the HadCM3 climate model. For both control and climate change scenarios, the standard deviation of the detrended accumulation rate was 1.4 ppbv\\/ yr for the period 1990-2009, compared with the measured standard

C. E. Johnson; D. S. Stevenson; W. J. Collins; R. G. Derwent

2002-01-01

272

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

Microsoft Academic Search

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

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

2004-01-01

273

Real-time monitoring of spontaneous resonance in heart rate variability  

Microsoft Academic Search

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

Emil Jovanov

2008-01-01

274

Heart Rate Variability Analysis Using Electric Fabric in Dry-Normal Condition  

Microsoft Academic Search

Significance verification of electric fabric compared with existing electrode is very useful for the wearable and ubiquitous healthcare. In this paper, we verified the significance between Ag\\/AgCl electrode and electric fabric in dry-normal condition through heart rate variability analysis. We can find 98% or more similarity about low frequency and high frequency parameter which is important for the heart rate

Hang Sik Shin; Chung Keun Lee; Sung Won Yoon; Dae Joong Yoon; Myoungho Lee

2005-01-01

275

Influence of high-frequency bandwidth on heart rate variability analysis during physical exercise  

Microsoft Academic Search

Heart rate variability (HRV) analysis of beat-to-beat RR interval data was performed in 11 asymptomatic young male subjects during a progressive bicycle exercise test. RR interval data (Polar S810) and breath-by-breath respiratory data (rate, minute ventilation and oxygen uptake) (Oxycon Pro) were simultaneously recorded throughout exercise. ‘Ventilation per second’ was defined as V?Esec, the change (from the previous epoch) in

M. J. Lewis; M. Kingsley; A. L. Short; K. Simpson

2007-01-01

276

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

NASA Astrophysics Data System (ADS)

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

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

2004-10-01

277

Heart Rate Variability Responses of a Preterm Infant to Kangaroo Care  

PubMed Central

A 35-week old preterm infant's behavior was fussy and restless in the open crib, but he calmed and fell asleep immediately on being placed skin-to-skin on his mother's chest. Heart rate variability (HRV), a noninvasive method to assess the autonomic nervous system's influence on heart rate, was increased with fussy behavior in the open crib and decreased with sleep during kangaroo care (KC). KC produced changes in behavior and HRV that are illustrative of decreasing stress.

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

2006-01-01

278

Identification of building applications for a variable-conductance insulation  

SciTech Connect

Recent experiments have confirmed the feasibility of controllable, reversible disabling of a vacuum insulation panel, which may result in the development of energy-efficient building envelope components. These components could extend the managed energy exchange through the building envelope from about 30% (typical with fenestration systems in commercial buildings), to as much as 90% of the gross wall and roof areas. Further investigation will be required to optimized the thermal response and the magnitude of the R-value swing (from a difference between insulating and conducting insulating values of 4 to as high as a factor of 100). The potential for energy reduction by using the variable-conductance insulation in the building envelope is discussed, and other potential building applications are mentioned.

Potter, T.F. [National Renewable Energy Lab., Golden, CO (United States); Tuluca, A. [Winter (Steven) Associates, Inc., New York, NY (United States)

1992-07-01

279

Heart rate variability during sleep and the early development of posttraumatic stress disorder  

Microsoft Academic Search

BackgroundNoradrenergic function has been linked to posttraumatic stress disorder (PTSD) and might have a role in mediating sleep disturbances of the disorder. Our objective was to relate a peripheral manifestation of noradrenergic function, sympathetic nervous system activity as indexed by heart rate variability during sleep, to the development of PTSD in subjects with recent traumatic injuries.

Thomas A Mellman; Bethany R Knorr; Wilfred R Pigeon; J. C Leiter; Metin Akay

2004-01-01

280

Chaos and spectral analyses of heart rate variability during head-up tilting in essential hypertension  

Microsoft Academic Search

To investigate nonlinear and linear components of heart rate variability (HRV) in essential hypertension (EHT), we analyzed HRV by chaos and spectral analyses in patients with EHT (n=18) and normotensives (n=10) during head-up tilting. We used the correlation dimension (CD) and Lyapunov exponents as the parameters of chaos. The CD, an index of complexity, was lower at rest in EHT

Shuntaro Kagiyama; Akira Tsukashima; Isao Abe; Shinichiro Fujishima; Susumu Ohmori; Uran Onaka; Yusuke Ohya; Koji Fujii; Takuya Tsuchihashi; Masatoshi Fujishima

1999-01-01

281

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

Microsoft Academic Search

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

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

2012-01-01

282

Predicting blood pressure reactivity and heart rate variability from mood state following coronary artery bypass surgery  

Microsoft Academic Search

Study objectives: Coronary Artery Bypass Graft (CABG) surgery is a common and successful procedure for revascularisation. However, the experience can induce emotional reactions prior to and following surgery. This study aimed to document changes in blood pressure (BP) reactivity and heart rate variability (HRV) following CABG surgery, and to determine the impact of mood state, particularly anxiety and depression upon

C. N Hallas; E. W Thornton; B. M Fabri; M. A Fox; M Jackson

2003-01-01

283

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...

284

Decreased long term variations of heart rate variability in subjects with higher self reporting stress scores  

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 relationships to mental stress were not studied explicitly for estimating stress levels. In this study, we investigated long term variations of HRV features to provide a reliable measure of chronic stress levels. Twenty three subjects

Desok Kim; Yunhwan Seo; Lizawati Salahuddin

2008-01-01

285

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

Microsoft Academic Search

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

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

2001-01-01

286

Spironolactone impairs endothelial function and heart rate variability in patients with Type 2 diabetes  

Microsoft Academic Search

Aims\\/hypothesis  Aldosterone blockade has followed in the footsteps of ACE inhibition in reducing mortality in patients with heart failure. This is associated with its beneficial effects on endothelial function and heart rate variability. Diabetes is another area, where angiotensin II withdrawal has proven to be of particular value. We postulated that aldosterone blockade with spironolactone might also have beneficial effects on

J. I. Davies; M. Band; A. Morris; A. D. Struthers

2004-01-01

287

Heart rate variability and saliva cortisol assessment in shelter dog: Human–animal interaction effects  

Microsoft Academic Search

The aim of this study is to investigate the effects of a human interaction program on shelter dogs and to determine the effect on canine heart rate variability, behaviour, and salivary cortisol levels. Twenty dogs were behaviourally (temperament tests) and clinically (full cardiologic examination) pre-tested and then matched in two homogenous groups. Ten dogs (group A) were submitted to a

Luciana Bergamasco; Maria Cristina Osella; Paolo Savarino; Giuseppe Larosa; Laura Ozella; Monica Manassero; Paola Badino; Rosangela Odore; Raffaella Barbero; Giovanni Re

2010-01-01

288

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

289

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

Microsoft Academic Search

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

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

1993-01-01

290

Detection of atrial fibrillation episodes using multiple heart rate variability features in different time periods  

Microsoft Academic Search

Circadian variations of cardiac diseases have been well known. For example, atrial fibrillation (AF) episodes show nocturnal predominance. In this study, we have developed multiple formulas that detect AF episodes in different times of the day. Heart rate variability features were calculated from randomly sampled three min ECG data. Logistic regression analyses were performed to generate three formulas for the

Desok Kim; Yunhwan Seo; Chan Hyun Youn

2008-01-01

291

Effects of antidepressant treatment on heart rate variability in major depression: A quantitative review  

Microsoft Academic Search

BACKGROUND: The literature measuring effects of antidepressant and electroconvulsive therapy (ECT) for major depression on heart rate variability (HRV) in medically well individuals was reviewed. METHODS: Fourteen studies evaluating HRV were included. Twenty three pre-post or within group comparisons were available. Treatment impact on measures of HRV was pooled over studies. We examined different classes of antidepressants, and for short

Louis T van Zyl; Takuya Hasegawa; Katsutaro Nagata

2008-01-01

292

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

293

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

294

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

295

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

296

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

Microsoft Academic Search

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

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

2001-01-01

297

Heart rate variability and short duration spaceflight: relationship to post-flight orthostatic intolerance  

Microsoft Academic Search

BACKGROUND: Upon return from space many astronauts experience symptoms of orthostatic intolerance. Research has implicated altered autonomic cardiovascular regulation due to spaceflight with further evidence to suggest that there might be pre-flight autonomic indicators of post-flight orthostatic intolerance. We used heart rate variability (HRV) to determine whether autonomic regulation of the heart in astronauts who did or did not experience

Andrew P Blaber; Roberta L Bondar; Mahmood S Kassam

2004-01-01

298

Power Spectral Analysis of Heart Rate Variability in Adolescent Male Athletes  

Microsoft Academic Search

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

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

2009-01-01

299

Mattis dementia rating scale: Clinical utility and relationship with demographic variables  

Microsoft Academic Search

The Mattis Dementia Rating Scale (DRS) is an instrument that is widely used to screen for dementia. The relationship of the DRS to demographic variables, however, has not been examined, and previous normative work is largely based on small or poorly described samples. In addition, there is no normative work that has been conducted with older medical patients. The present

Stephen J. Vangel Jr; Peter A. Lichtenberg

1995-01-01

300

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…

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

301

Circadian rhythm and variability of heart rate in Duchenne-type progressive muscular dystrophy  

Microsoft Academic Search

Using 24-hour Holter monitoring and time domain and power spectral measurements, we evaluated the variability or the heart rate and its circadian rhythm in 55 male patients with Duchenne-type progressive muscular dystrophy (DMD) to characterize their autonomic function versus findings in 20 normal controls. Comparisons were also made in patients with mild, moderate, and severe stages of DMD. The percent

Masayuki Yotsukura; Kazuya Sasaki; Eisei Kachi; Akira Sasaki; Tadayuki Ishihara; Kyozo Ishikawa

1995-01-01

302

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

Microsoft Academic Search

Background Cigarette smoking has been shown to adverse- ly affect heart rate variability (HRV), suggesting dysregula- tion of cardiac autonomic function. Conversely, smoking cessation is posited to improve cardiac regulation. Purpose The aim of the present study was to examine the effects of smoking cessation on HRV among a community sample of chronic smokers. Methods Sixty-two healthy male smokers enrolled

Christopher B. Harte; Cindy M. Meston

2013-01-01

303

Effect of 21 mg transdermal nicotine patches and smoking cessation on heart rate variability  

Microsoft Academic Search

The effect of smoking cessation on cardiac autonomic tone, as reflected by indexes of heart rate variability (HRV), has not been reported. Current smokers (n = 54, mean ± SD age 43 ± 12 years) who desired to quit, and were smoking ?1 pack\\/day and had made ?1 prior attempt at quitting, had 24-hour electrocardiographic recordings. They then attended smoking

Phyllis K. Stein; Jeffrey N. Rottman; Robert E. Kleiger

1996-01-01

304

Total power and high frequency components of heart rate variability and risk factors for atherosclerosis  

Microsoft Academic Search

Introduction: Low heart rate variability, HRV, is associated with diabetic neuropathy and with ischemic heart disease, IHD. The time context points to diabetes preceding changes in HRV, while changes in HRV precede the development of atherosclerosis and IHD. The purpose of the study was to analyse the association between the physiological risk factors of IHD and HRV in a prospective

Nanna Hurwitz Eller

2007-01-01

305

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...

306

Sudden unexpected death in epilepsy associated with progressive deterioration in heart rate variability  

Microsoft Academic Search

We describe a patient with severe epilepsy who underwent serial measurements of heart rate variability (HRV) prior to his death from autopsy-confirmed sudden unexpected death in epilepsy (SUDEP). The significance of low HRV is discussed in relation to SUDEP risk. Progressive deterioration in HRV may be a risk factor for SUDEP.

G. Rauscher; A. C. DeGiorgio; P. R. Miller; C. M. DeGiorgio

2011-01-01

307

Reinnervation of the transplanted human heart as evidenced from heart rate variability studies  

Microsoft Academic Search

This study evaluated heart rate variability (HRV) after cardiac transplantation in humans in an attempt to test the hypothesis that cardiac reinnervation occurs in the post-transplant period. HRV was measured using 24-hour Holter recordings performed on 37 ambulant patients 1 to 122 months after cardiac transplantation. All patients were free of histologic rejection and were taking no medication likely to

Igor Halpert; A. David Goldberg; Arlene B. Levine; T. Barry Levine; Robert Kornberg; Colleen Kelly; Michael Lesch

1996-01-01

308

Analysis of heart rate variability during exercise stress testing using respiratory information  

Microsoft Academic Search

This paper presents a novel method for the analysis of heart rate variability (HRV) during exercise stress testing enhanced with respiratory information. The instantaneous frequency and power of the low frequency (LF) and high frequency (HF) bands of the HRV are estimated by parametric decomposition of the instantaneous autocorrelation function (ACF) as a sum of damped sinusoids. The instantaneous ACF

Raquel Bailón; Luca Mainardi; Michele Orini; Leif Sörnmo; Pablo Laguna

2010-01-01

309

Smooth scheduling under variable rates or the analog-digital confinement game  

Microsoft Academic Search

This work considers non-terminating scheduling problems in which a system of multiple resources serves clients having variable needs. The system has m identical resources and n clients; in each time slot each resource may serve at most one client; in each such slot t each client ? has a rate, a real number ??(t), that specifies his needs in this

Ami Litman; Shiri Moran-schein

2006-01-01

310

Rate of Information-Processing as a Variable of Critical Reading.  

ERIC Educational Resources Information Center

|This study investigated the relationship between rate of information processing and critical reading and the anciallary effect of anxiety on the two variables. A tenth grade sample, consisting of 52 fast readers and 52 slow readers, was identified. All subjects in the sample had intelligence quotients of 120 or higher and vocabulary and…

Van Voorhees, Sylvia Nash

311

Variability of Peak Expiratory Flow Rate as a Prognostic Index in Asymptomatic Asthma  

Microsoft Academic Search

The prognostic relevance of an enhanced variability of peak expiratory flow rate (PEFR) throughout the day was evaluated in asthmatics in remission: it was expressed as the coefficient of variation (CV) of values recorded 4 times daily for weeks. Outcome at 3, 6, and 12 months was assessed in 2 groups of 16 patients each, differing because of a CV

V. Bellia; F. Cibella; P. Coppola; V. Greco; G. Insalaco; F. Milone; S. Oddo; G. Peralta

1984-01-01

312

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

ERIC Educational Resources Information Center

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

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

2012-01-01

313

Magnesium administration may improve heart rate variability in patients with heart failure  

Microsoft Academic Search

Background and aimIntracellular magnesium (icMg) depletion may coexist with normomagnesemia. Mg deficiency (serum and\\/or intracellular) and decreased heart rate variability (HRV) are common in heart failure (HF). Since both are predictors of poor prognosis, it was of interest to evaluate the effect of Mg supplementation on HRV in patients with HF.

D. Almoznino-Sarafian; G. Sarafian; S. Berman; M. Shteinshnaider; I. Tzur; N. Cohen; O. Gorelik

2009-01-01

314

Heart Rate Variability Measurements During Exercise Test May Improve the Diagnosis of Ischemic Heart Disease.  

National Technical Information Service (NTIS)

In this work we have analyzed changes in the heart rate variability (HRV) during exercise test comparing them with the ST deviation criteria to improve the diagnostic value of the exercise test. Coronary angiography was considered as gold standard to esta...

J. Mateo P. Serrano R. Bailon J. Garcia A. Ferreira

2001-01-01

315

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

316

Online traffic smoothing for delivery of variable bit rate media streams  

Microsoft Academic Search

Traffic smoothing for delivery of online variable bit rate (VBR) media streams is one of the most important problems in designingmultimedia systems. Given an available client buffer, a window size, and a window-sliding size, previous window-based online smoothing methods have tried to reduce the peak bandwidth allocated in each window. However, as bandwidths allocated in different windows are minimized independently,

Ray-I Chang; Meng-Chang Chen; Jan-Ming Ho; Ming-Tat Ko

2001-01-01

317

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

Microsoft Academic Search

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

Nicholas D. Giardino; Leighton Chan; Soo Borson

2004-01-01

318

Experience of using analysis methods of heart rate variability in anesthesiology practice  

Microsoft Academic Search

This paper aims to develop a means to estimate the practical efficiency of heart rate variability (HRV) analysis in the perioperative period to help define the adequacy of anesthesia. By monitoring the patient's status with the help of the indicated agents, the adequacy of anesthesia can be estimated and early diagnostics of complications originating during an anesthesia can be provided.

A. N. Rybakov; A. V. Maneev

2003-01-01

319

Antihypertensive treatment and heart rate variability in diabetic patients: role of cardiac autonomic neuropathy  

Microsoft Academic Search

Optimization of antihypertensive drug therapy continues to be a clinical challenge in patients with diabetes mellitus and its complications. We assessed the interference of autonomic neuropathy with drug effects on heart rate variability in 13 hypertensive diabetic subjects (mean age 48.4 years) during treatment with two blood pressure lowering drugs, metoprolol and enalapril. The baseline findings were compared with those

Tiina M. Salo; Jorma S. A. Viikari; Kari J. Antila; Liisa-Maria Voipio-Pulkki; Jarmo O. Jalonen; Ilkka A. T. Välimäki

1996-01-01

320

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

PubMed Central

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

Slatkin, M; Bertorelle, G

2001-01-01

321

Heart Rate Variability Characterization Using a Time-Frequency Based Instantaneous Frequency Estimation Technique  

Microsoft Academic Search

In this paper, a new method for characterizing the newborn heart rate variability (HRV) is proposed. The central of the method is the newly proposed technique for instantaneous frequency (IF) estimation specifically designed for nonstationary multicomponent signals such as HRV. The new method attempts to characterize the newborn HRV using features extracted from the time-frequency (TF) domain of the signal.

MB Malarvili; L. Rankine; M. Mesbah; P. B. Colditz; B. Boashash

322

Variable bit-rate coding of video signals for ATM networks  

Microsoft Academic Search

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

FUMIO KISHINO; KATSUTOSHI MANABE; YASUHITO HAYASHI; HIROSHI YASUDA

1989-01-01

323

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

PubMed Central

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

2013-01-01

324

Non-linear rate dependent deformation under compression due to state variable friction  

NASA Astrophysics Data System (ADS)

Observations of strain-rate effects in brittle failure under compression have been interpreted as suggesting that sub-critical crack growth plays an important role in the deformation process. We suggest an alternate interpretation in which strain-rate effects are attributed to rate- and state-dependent friction along parent cracks. Using independently measured friction law parameters we demonstrate that a wing crack model incorporating state variable friction replicates the observed dependence of the stress-strain curve on applied strain rate. Model results are essentially equivalent to those of an earlier model incorporating sub-critical crack growth, suggesting that despite their different conceptual foundations, the validity of either model can not be determined on the basis of the observed strain-rate effects. However, only the rate-dependent friction model reproduces the observed unsteady growth of wing cracks.

Renshaw, Carl E.; Schulson, Erland M.

325

Variability of Phyllochron, Plastochron and Rate of Increase in Height in Photoperiod-sensitive Sorghum Varieties  

PubMed Central

Background and Aims West African sorghum (Sorghum bicolor) varieties are generally highly photoperiod-sensitive, 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 m to more than 5 m. The present study aimed to better understand the complex phenology of these variables. Methods A 2-year series of monthly sowings of three West African sorghum varieties was conducted near Bamako, Mali. Drought stress was avoided by supplemental irrigation. Rate of initiation of primordia at the stem apex was recorded, together with rate of leaf emergence and increase in plant height. Key Results Leaf initiation and appearance rates (plastochron?1 and phyllochron?1) were constant for a given sowing date in cases where less than 20 leaves were produced (generally observed with late sowing dates). In contrast, rates were bilinear for early sowing dates, for which plants produced more than 20 leaves. The secondary rates, which occurred from the 20th leaf onwards, were only half of the initial rate. Plastochron and phyllochron showed large variations among sowing dates, and were correlated with the rate of plant height increase. The initial plastochron and phyllochron were positively correlated with soil temperature and negatively correlated with both day length and day-to-day change of day length prevailing at plant emergence, but these factors explained only half of the variation observed. Conclusions Although they belong to different genetic groups and have different height and photoperiod sensitivity, the three varieties studied exhibited similar response patterns of development rates among phenological phases and seasons, with the local landrace showing the greatest variation due to its longer vegetative phase and longer stem internodes. The possible adaptive advantages in African savannah environments of bilinear development rates and the associated limitation in height increase are discussed.

Clerget, B.; Dingkuhn, M.; Goze, E.; Rattunde, H. F. W.; Ney, B.

2008-01-01

326

When Applicants Rate the Examinations: Feedback from 2000 People.  

National Technical Information Service (NTIS)

Very high rates of satisfaction with their job tests are experienced by employment applicants, as evident from a series of studies conducted in the Seattle area in a seven-year program from 1980-86. Almost 2500 applicants for civil service jobs were sampl...

R. Davis

1986-01-01

327

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

328

Large strain rate-dependent response of elastomers at different strain rates: convolution integral vs. internal variable formulations  

NASA Astrophysics Data System (ADS)

Two different viscoelastic frameworks adapted to large strain rate-dependent response of elastomers are compared; for each approach, a simple model is derived. Within the Finite Linear Viscoelasticity theory, a time convolution integral model based on an extension to solid of the K-BKZ model is proposed. Considering the multiplicative split of the deformation gradient into elastic and inelastic parts, an internal variable model based on a large strain version of the Standard Linear Solid model is considered. In both cases, the strain energy functions involved are chosen neo-Hookean, and then each model possesses three material parameters: two stiffnesses and a viscosity parameter. These parameters are set to ensure the equivalence of the model responses for uniaxial large strain quasi-static and infinitely fast loading conditions, and for uniaxial rate-dependent small strain loading conditions. Considering their responses for different Eulerian strain rates, their differences are investigated with respect to the strain rate; more specifically, both stiffness and dissipative properties are studied. The comparison reveals that these two models differ significantly for intermediate strain rates, and a closing discussion highlights some issues about their foundations and numerical considerations.

Petiteau, J.-C.; Verron, E.; Othman, R.; Le Sourne, H.; Sigrist, J.-F.; Barras, G.

2013-08-01

329

Ambulatory ECG and analysis of heart rate variability in Parkinson's disease  

PubMed Central

OBJECTIVES—Cardiovascular reflex tests have shown both sympathetic and parasympathetic failure in Parkinson's disease. These tests, however, describe the autonomic responses during a restricted time period and have great individual variability, providing a limited view of the autonomic cardiac control mechanisms. Thus, they do not reflect tonic autonomic regulation. The aim was to examine tonic autonomic cardiovascular regulation in untreated patients with Parkinson's disease.?METHODS—24 Hour ambulatory ECG was recorded in 54 untreated patients with Parkinson's disease and 47 age matched healthy subjects. In addition to the traditional spectral (very low frequency, VLF; low frequency, LF; high frequency, HF) and non-spectral components of heart rate variability, instantaneous beat to beat variability (SD1) and long term continuous variability (SD2) derived from Poincaré plots, and the slope of the power law relation were analysed.?RESULTS—All spectral components (p<0.01) and the slope of the power-law relation (p<0.01) were lower in the patients with Parkinson's disease than in the control subjects. The Unified Parkinson's disease rating scale total and motor scores had a negative correlation with VLF and LF power spectrum values and the power law relation slopes. Patients with mild hypokinesia had higher HF values than patients with more severe hypokinesia. Tremor and rigidity were not associated with the HR variability parameters.?CONCLUSIONS—Parkinson's disease causes dysfunction of the diurnal autonomic cardiovascular regulation as demonstrated by the spectral measures of heart rate variability and the slope of the power law relation. This dysfunction seems to be more profound in patients with more severe Parkinson's disease.??

Haapaniemi, T; Pursiainen, V; Korpelainen, J; Huikuri, H; Sotaniemi, K; Myllyla, V

2001-01-01

330

Effect of Mild, Asymptomatic Obstructive Sleep Apnea on Daytime Heart Rate Variability and Impedance Cardiography Measurements  

PubMed Central

Dysregulation of autonomic nervous system dynamics is important in the pathophysiology of cardiovascular risk in obstructive sleep apnea (OSA). Heart rate variability (HRV) and impedance cardiography measures can estimate autonomic activity but have not gained traction clinically. We hypothesized that, even in a cohort of mild, asymptomatic OSA patients without overt cardiovascular disease, daytime HRV metrics and impedance cardiography measurements of pre-ejection period (PEP) would demonstrate increased sympathetic and decreased parasympathetic modulation compared with matched controls. Obese individuals (BMI ?30 kg/m2) without any known cardiovascular or inflammatory comorbidities were recruited from the community. Subjects underwent standard in-laboratory polysomnograms (PSG), followed by simultaneous electrocardiography (ECG) and impedance cardiography recordings while supine, supine with paced breathing, and after standing. 74 subjects were studied, and 59% had OSA (apnea-hypopnea index (AHI) ?10episodes/hr) with a median AHI of 25.8/hr. OSA subjects had significantly decreased daytime time- and frequency-domain HRV indices, but not significantly different PEP, when compared to controls. AHI was a significant independent predictor of time-domain HRV measures in all awake conditions, after controlling for age, gender, blood pressure, fasting cholesterol levels and hemoglobin A1C. In conclusion, our results demonstrate reductions in cardiac vagal modulation, as measured by multiple daytime time-domain markers of HRV, among asymptomatic OSA patients versus controls. Further prospective outcomes-based studies are needed to evaluate the applicability of these metrics for noninvasive screening of obese asymptomatic OSA patients, prior to the onset of overt cardiovascular disease.

Balachandran, Jay S.; Bakker, Jessie P.; Rahangdale, Shilpa; Yim-Yeh, Susie; Mietus, Joseph E.; Goldberger, Ary L.; Malhotra, Atul

2011-01-01

331

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.

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

2013-01-01

332

Spatial and temporal variability in rates of landsliding in seismically active mountain ranges  

NASA Astrophysics Data System (ADS)

Where earthquake and precipitation driven disasters occur in steep, mountainous regions, landslides often account for a large proportion of the associated damage and losses. This research addresses spatial and temporal variability in rates of landslide occurrence in seismically active mountain ranges as a step towards developing better regional scale prediction of losses in such events. In the first part of this paper we attempt to explain reductively the variability in spatial rates of landslide occurrence, using data from five major earthquakes. This is achieved by fitting a regression-based conditional probability model to spatial probabilities of landslide occurrence, using as predictor variables proxies for spatial patterns of seismic ground motion and modelled hillslope stability. A combined model for all earthquakes performs well in hindcasting spatial probabilities of landslide occurrence as a function of readily-attainable spatial variables. We present validation of the model and demonstrate the extent to which it may be applied globally to derive landslide probabilities for future earthquakes. In part two we examine the temporal behaviour of rates of landslide occurrence. This is achieved through numerical modelling to simulate the behaviour of a hypothetical landscape. The model landscape is composed of hillslopes that continually weaken, fail and reset in response to temporally-discrete forcing events that represent earthquakes. Hillslopes with different geometries require different amounts of weakening to fail, such that they fail and reset at different temporal rates. Our results suggest that probabilities of landslide occurrence are not temporally constant, but rather vary with time, irrespective of changes in forcing event magnitudes or environmental conditions. Various parameters influencing the magnitude and temporal patterns of this variability are identified, highlighting areas where future research is needed. This model has important implications for landslide hazard and risk analysis in mountain areas as existing techniques usually assume that susceptibility to failure does not change with time.

Parker, R.; Petley, D.; Rosser, N.; Densmore, A.; Gunasekera, R.; Brain, M.

2012-04-01

333

Can mock interviewers' personalities influence their personality ratings of applicants?  

PubMed

The authors examined individual difference and self-regulatory variables to understand how an interviewer rates a candidate's personality. Participants were undergraduate students at a large midwestern university in the United States who completed measures of individual differences, read an employment interview transcript involving a candidate applying for a customer service job, and rated the candidate's personality. Participants' agreeableness, social skills, and communion striving were positively associated with their ratings of the candidate's helpfulness and obedience. The authors provide a foundation for further research on interviewer effectiveness and the processes underlying the employment interview. PMID:19306679

Hilliard, Thomas; Macan, Therese

2009-03-01

334

An evaluation of subsidence rates and sea-level variability in the northern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

While subsidence is widely recognized as a driver of geomorphic change in the northern Gulf of Mexico (GOM), there is considerable disagreement over the rates of subsidence and the interpreted variability in these rates, which leads to controversies over the impacts of subsidence on surface land area change. Here we present a new method to calculate subsidence rates from the tide gauge record that is based on an understanding of the meteorological drivers of inter-annual sea-level change. In Grand Isle, LA and Galveston, TX, we explicitly show that temporal patterns of subsidence are closely linked to subsurface fluid withdrawal and coastal land loss, and suggest changes in withdrawal rates can both increase and decrease rates of subsidence and wetland loss. Our results also imply that the volume of sediment needed to rebuild GOM wetlands may currently fall within the low end of some restoration scenarios.

Kolker, Alexander S.; Allison, Mead A.; Hameed, Sultan

2011-11-01

335

Heat accumulation effects in femtosecond laser-written waveguides with variable repetition rate  

NASA Astrophysics Data System (ADS)

High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses. A novel femtosecond fiber laser system (IMRA America, FCPA ?Jewel) providing variable repetition rate between 0.1 and 5 MHz was used to study the relationship between heat accumulation and resulting waveguide properties in fused silica and various borosilicate glasses. Increasing repetition rate was seen to increase the waveguide diameter and decrease the waveguide loss, with waveguides written with 1-MHz repetition rate yielding ~0.2-dB/cm propagation loss in Schott AF45 glass. A finite-difference thermal diffusion model accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.

Eaton, Shane M.; Zhang, Haibin; Herman, Peter R.; Yoshino, Fumiyo; Shah, Lawrence; Bovatsek, James; Arai, Alan Y.

2005-06-01

336

Heat accumulation effects in femtosecond laser-written waveguides with variable repetition rate.  

PubMed

High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses. A novel femtosecond fiber laser system (IMRA America, FCPA muJewel) providing variable repetition rate between 0.1 and 5 MHz was used to study the relationship between heat accumulation and resulting waveguide properties in fused silica and various borosilicate glasses. Increasing repetition rate was seen to increase the waveguide diameter and decrease the waveguide loss, with waveguides written with 1-MHz repetition rate yielding ~0.2-dB/cm propagation loss in Schott AF45 glass. A finite-difference thermal diffusion model accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate. PMID:19495387

Eaton, Shane; Zhang, Haibin; Herman, Peter; Yoshino, Fumiyo; Shah, Lawrence; Bovatsek, James; Arai, Alan

2005-06-13

337

Cardio-pulmonary fitness test by ultra-short heart rate variability  

PubMed Central

Objectives: It is known that exercise induces cardio-respiratory autonomic modulation. The aim of this study was to assess the cardio-pulmonary fitness by ultra-short heart rate variability. Materials and Methods: Study population was divided into 3 groups: Group-1 (n = 40) consisted of military sports man. Group-2 (n = 40) were healthy age-matched sedentary male subjects with normal body mass index [BMI = 19 - 25 kg/m2). Group-3 (n = 40) were healthy age-matched obese male subjects [BMI > 29 kg/m2). Standard deviation of normal-to-normal QRS intervals (SDNN) was recorded over 15 minutes. Bruce protocol treadmill test was used; and, maximum oxygen consumption (VO2max) was calculated. Results: When the study population was divided into quartiles of SDNN (first quartile: < 60 msec; second quartile: > 60 and < 100 msec; third quartile: > 100 and <140 msec; and fourth quartile: >140 msec), progressive increase was found in VO2max; and, SDNN was significantly linked with estimated VO2max. Conclusion: In conclusion, the results of this study demonstrate that exercise training improves cardio-respiratory autonomic function (and increases heart rate variability). Improvement in cardio-respiratory autonomic function seems to translate into a lower rate of long term mortality. Ultra-short heart rate variability is a simple cardio-pulmonary fitness test which just requires 15 minutes, and involves no exercise such as in the treadmill or cycle test.

Aslani, Arsalan; Aslani, Amir; Kheirkhah, Jalal; Sobhani, Vahid

2011-01-01

338

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

PubMed Central

AIM—To investigate whether uncomplicated chronic coronary artery disease causes changes in heart rate variability and if so, whether the heart rate variability pattern is different from that described in patients with acute myocardial infarction.?METHODS—Heart rate variability was studied in 65 patients with angina who had no previous myocardial infarcts, no other diseases, and were on no drug that could influence the sinus node. Results were compared with 33 age matched healthy subjects. The diagnosis of coronary artery disease in angina patients was established by coronary angiography in 58, by thallium scintigraphy in six, and by exercise test only in one. Patients and controls were Holter monitored 24 hours outside hospital, and heart rate variability was calculated in the frequency domain as global power (GP: 0.01-1.00 Hz), low frequency peak (LF: 0.04-0.15 Hz), high frequency peak (HF: 0.15-0.40 Hz), LF/HF in ms2, and in the time domain as SDNN (SD of normal RR intervals), SDANN (SD of all five minute mean normal RR intervals), SD (mean of all five minute SDs of mean RR intervals), rMSSD (root mean square of differences of successive normal RR intervals) (all in ms), and pNN50 (proportion of adjacent normal RR intervals differing more than 50 ms from the preceding RR interval) as per cent.?RESULTS—The mean age in patients and controls was 60.4 (range 32-81) and 59.1 (32-77) years, respectively (NS), the male/female ratio, 57/65 and 24/33 (NS), and the mean time of Holter monitoring, 23.0 (18-24) and 22.8 (18-24) hours (NS). Mortality in angina patients was 0% (0/65) at one year, 0% (0/56) at two years, and 3% (1/33) at three years. Compared with healthy subjects angina patients showed a reduction in GP (p = 0.007), HF (p = 0.02), LF (p = 0.02), SD (p = 0.02), rMSSD (p = 0.01), and pNN50 (p = 0.01). No significant difference was found in RR, LF/HF, SDNN, or SDANN.?CONCLUSIONS—Uncomplicated coronary artery disease without previous acute myocardial infarction was associated with reduced high and low frequency heart rate variability, including vagal tone. SDANN and SDNN, expressing ultra low and very low frequencies which are known to reflect prognosis after acute myocardial infarction, were less affected. This is in agreement with the good prognosis in uncomplicated angina in this study.???Keywords: heart rate variability; angina pectoris; coronary artery disease; myocardial infarction; prognosis

Wennerblom, B; Lurje, L; Tygesen, H; Vahisalo, R; Hjalmarson, A

2000-01-01

339

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

340

Applicability and efficacy of variable light in schools.  

PubMed

There is a range of reliable, empirical data on the effects of special lighting techniques on the performance of adults in the work environment in the literature. However, these studies have not adequately addressed the effects of lighting on school children in the classroom environment. In the present study, the effect of variable lighting (VL) i.e., lighting that is variable in illuminance and color temperature, was studied in the classroom using a variety of student performance and attitude measures. Two classrooms each in two separate schools were studied over a period of nine months; one class in each school served as an intervention group, and a parallel class in each school served as a control group. The effects of the individual VL programs were assessed using standardized test modules. The overall effect was measured using standardized surveys of students and teachers given at the beginning and the end of the project. The results showed that the students made fewer errors, particularly fewer errors of omission, on a standardized test of attention under the VL "Concentrate" program. Reading speed, as measured using standardized reading tests, rose significantly. Reading comprehension also improved, but this improvement was not statistically significant. In contrast, the achievement motivation of the students and the classroom atmosphere did not change over the nine-month period. Overall, the students and teachers rated VL positively and found it useful during lessons. These results are in line with previous research findings. Thus, VL represents an environmental factor that can be useful to optimize general learning conditions in schools in the future. PMID:22001491

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

2011-10-06

341

Some variables affecting rate of key pecking during response-independent procedures (autoshaping)1  

PubMed Central

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

Perkins, Charles C.; Beavers, William O.; Hancock, Robert A.; Hemmendinger, Patricia C.; Hemmendinger, Dennis; Ricci, John A.

1975-01-01

342

Decoding Continuous Variables from Neuroimaging Data: Basic and Clinical Applications  

PubMed Central

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

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

2011-01-01

343

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

Microsoft Academic Search

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

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

2008-01-01

344

The relationship of late potentials to assessment of heart rate variability in post-infarction patients  

Microsoft Academic Search

In order to investigate the relationship of late potential (LP) to assessment of heart rate variability (HRV) after acute myocardial infarction (AMI), we studied 101 Chinese patients with AMI (10±2.4 days) in Taiwan by collecting 24-h ECG from a Holter tape recorder and signal-averaged ECG from a high-resolution ECG cart. Of the 101 patients, 36 patients had LP (LP group)

Tsair Kao; Hsiang-Chiang Hsiao; Hung-Wen Chiu; Chi-Woon Kong

2000-01-01

345

The relationships among heart rate variability, inflammatory markers and depression in coronary heart disease patients  

Microsoft Academic Search

Studies show negative correlations between heart rate variability (HRV) and inflammatory markers. In cardiac patients, depression is related to both. We investigated links between short-term HRV and inflammatory markers in relation to depression in acute coronary syndrome (ACS) patients.We measured C-reactive protein (CRP), interleukin-6 (IL-6), depression symptoms (Beck Depression Inventory, BDI-II), and SDNN, high frequency (HF) and low frequency (LF)

Nancy Frasure-Smith; François Lespérance; Michael R. Irwin; Mario Talajic; Bruce G. Pollock

2009-01-01

346

Depressed heart rate variability identifies postinfarction patients who might benefit from prophylactic treatment with amiodarone  

Microsoft Academic Search

OBJECTIVESThis substudy tested a prospective hypothesis that European Myocardial Infarct Amiodarone Trial (EMIAT) patients with depressed heart rate variability (HRV) benefit from amiodarone treatment.BACKGROUNDThe EMIAT randomized 1,486 survivors of acute myocardial infarction (MI) aged ?75 years with left ventricular ejection fraction (LVEF) ?40% to amiodarone or placebo. Despite a reduction of arrhythmic mortality on amiodarone, all-cause mortality was not changed.METHODSHeart

Marek Malik; A. John Camm; Michiel J Janse; Desmond G Julian; Gerald A Frangin; Peter J Schwartz

2000-01-01

347

Comparison of Verapamil Versus Felodipine on Heart Rate Variability After Acute Myocardial Infarction  

Microsoft Academic Search

A depressed heart rate variability (HRV) is a powerful predictor of poor outcome in myocardial infarction patients. The beneficial effect of specific interventions on its recovery has been reported, but data concerning calcium antagonists are scarce. We evaluated the effect of a phenylalkylamine derivative, verapamil, and a dihydropyridine derivative, felodipine, on time-and frequency-domain measurements of HRV by 24-hour Holter monitoring

1997-01-01

348

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

Microsoft Academic Search

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

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

2007-01-01

349

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

Microsoft Academic Search

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

Amanda L. WheatKevin; Kevin T. Larkin

2010-01-01

350

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

Microsoft Academic Search

Oetrended fluctuation analysis (DFA), a fractal analysis method which is widely used in heart rate variability (HRV) studies, is used to analyze the scaling behaviour of RR interval series of preterm neonates. The average scaling behaviour, calculated using 30000 RR intervals (3-4 hours), is characterized by a scaling exponent of 1.4 plusmn 0.1 at small scales (n<20) and a smaller

Geert Morren; Philippe Lemmerling; H. Daniels; G. Naulaers; S. Van Huffel

2005-01-01

351

Autonomic Nervous System Function in Infants and Adolescents: Impact of Autonomic Tests on Heart Rate Variability  

Microsoft Academic Search

Measurement of heart rate variability (HRV) shows information on the functional state of the autonomic nervous system (ANS).\\u000a In adults there are standardized autonomic tests and well-established ranges of normal values, which is not the case in children.\\u000a The aim of the present study was (1) to introduce an ANS test battery, especially for children and adolescents; (2) to establish

Elke Longin; Carmen Dimitriadis; Samina Shazi; Thorsten Gerstner; Tamara Lenz; Stephan König

2009-01-01

352

Loss of lag-response curvilinearity of indices of heart rate variability in congestive heart failure  

Microsoft Academic Search

BACKGROUND: Heart rate variability (HRV) is known to be impaired in patients with congestive heart failure (CHF). Time-domain analysis of ECG signals traditionally relies heavily on linear indices of an essentially non-linear phenomenon. Poincaré plots are commonly used to study non-linear behavior of physiologic signals. Lagged Poincaré plots incorporate autocovariance information and analysis of Poincaré plots for various lags can

Tushar P Thakre; Michael L Smith

2006-01-01

353

Effects of Air Pollution on Heart Rate Variability: The VA Normative Aging Study  

Microsoft Academic Search

Reduced heart rate variability (HRV), a marker of poor cardiac autonomic function, has been associated with air pollution, especially fine particulate matter (< 2.5 µm in aerodynamic diameter (PM2.5)). We examined the relationship between HRV (standard deviation of normal-to-normal intervals (SDNN), power in high frequency (HF) and low frequency (LF), and LF:HF ratio) and ambient air pollutants in 497 men

Sung Kyun Park; Marie S. O’Neill; Pantel S. Vokonas; David Sparrow; Joel Schwartz

2004-01-01

354

Cognitive reappraisal increases heart rate variability in response to an anger provocation  

Microsoft Academic Search

Adaptive self-regulatory responses to negative events are associated with good mental health, social functioning, and physical\\u000a health. Two forms of emotion regulation that have received attention within the context of anger are cognitive reappraisal\\u000a and expressive suppression. Research suggests that greater heart rate variability (HRV) is a physiological indicator of adaptive\\u000a emotion regulation and decreased mental load. In the present

Thomas F. DensonJessica; Jessica R. Grisham; Michelle L. Moulds

2011-01-01

355

Air Pollution and Heart Rate Variability: Effect Modification by Chronic Lead Exposure  

Microsoft Academic Search

Background—Outdoor air pollution and lead exposure can disturb cardiac autonomic function, but the effects of both these exposures together have not been studied. Methods—We examined whether higher cumulative lead exposures, as measured by bone lead, modified cross-sectional associations between air pollution and heart rate variability among 384 elderly men from the Normative Aging Study. We used linear regression, controlling for

Sung Kyun Park; Pantel S. Vokonas; David Sparrow; Robert O. Wright; Brent Coull; Huiling Nie; Howard Hu; Joel Schwartz

2008-01-01

356

Heart rate variability is confounded by the presence of erratic sinus rhythm  

Microsoft Academic Search

Decreased heart rate variability (HRV) predicts adverse outcomes. HRV can be elevated by episodes of significant non-respiratory sinus arrhythmia (i.e., a highly erratic sinus rhythm with normal p-waves, ESR). This elevated HRV could confound risk stratification by increasing HRV in high-risk patients. HRV was determined from tapes recorded at baseline in the Cardiovascular Health Study, a population study of older

P. K. Stein; D. Yanez; P. P. Domitrovich; J. Gottdiener; P. Chaves; R. Kronmal; P. Rautaharju

2002-01-01

357

Stochastic analysis of heart rate variability and its relation to echocardiography parameters in hypertrophic cardiomyopathy patients  

Microsoft Academic Search

The heart rate variability of 10 healthy males (age 26 - 4\\/+ 3 y) and 49 patients with hypertrophic cardiomyopathy (HCM) (25 males, 24 females, age 29.5 - 11.5\\/+ 10.5 y) was studied. We applied Kramers-Moyal expansion to extract the drift and diffusion terms of the Langevin equation for the RR interval time series. These terms may be used for

M. Petelczyc; J. J. Zebrowski; R. Baranowski; L. Chojnowska

2010-01-01

358

Seasonal variability of infiltration rates under contrasting slope conditions in southeast Spain  

Microsoft Academic Search

Infiltration is the key process in the rainfall-runoff relationship. Little is known, however, about the seasonal and spatial variability, which is important for the behaviour of the slope surface geomorphological processes.The infiltration rates for contrasting slopes in southeast Spain have been measured by means of simulated rainfall and ponding. A north- and a south-facing slope were selected to analyze effects

A. Cerdà

1996-01-01

359

Screening of heart diseases with multivariate short-term heart rate variability analysis  

Microsoft Academic Search

\\u000a Heart diseases are the leading cause of mortality in the western world. The aim of this pilot study was to examine the possibility\\u000a of screening heart diseases for the general practitioner by short-term analysis (five-minute ECG segments) of the heart rate\\u000a variability (HRV) applying linear (time domain and frequency domain) and nonlinear (detrended fluctuation analysis (DFA),\\u000a compression entropy (CE), symbolic

A. Heitmann; T. Huebner; R. Schroeder; S. Perz; A. Voss

360

Orthostatic influence on heart rate and blood pressure variability in trained persons with tetraplegia  

Microsoft Academic Search

To examine the orthostatic influence on heart rate and blood pressure variability in persons with tetraplegia playing wheelchair\\u000a basketball, ten trained persons with tetraplegia, ten untrained persons with tetraplegia, and ten able-bodied participated\\u000a in this study. Spectrum analysis of the ECG R–R interval and blood-pressure on a beat-by-beat basis during head-up tilt 60°\\u000a sitting were performed. The ratio of the

Yasuko Otsuka; Norihiro Shima; Toshio Moritani; Kuniharu Okuda; Kyonosuke Yabe

2008-01-01

361

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

Microsoft Academic Search

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

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

2009-01-01

362

Heart rate variability as a predictor of mortality in patients with AA and AL amyloidosis  

Microsoft Academic Search

Aims Patients with AA and AL amyloidosis have a limited life-expectancy. The aim of this study was to investigate whether heart rate variability can predict mortality in these patients. Methods and Results Twenty-two recently diagnosed patients with AA and 23 patients with AL amyloidosis were included. Fifteen patients (5 AA, 10 AL) died within 1 year. Twenty-four hour Holter recording

A. K. L. Reyners; B. P. C. Hazenberg; W. D. Reitsma; A. J. Smit

2002-01-01

363

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

364

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

Microsoft Academic Search

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

A Molfino; A Fiorentini; L Tubani; M Martuscelli; F Rossi Fanelli; A Laviano

2009-01-01

365

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

Microsoft Academic Search

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

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

2009-01-01

366

Increased heart rate variability and executive performance after aerobic training in the elderly  

Microsoft Academic Search

This study examined the effects of two short physical training programs on various parameters of heart rate variability (HRV)\\u000a and on executive performance in older people. Twenty-four sedentary men and women aged 65–78 years were randomly assigned\\u000a to an aerobic exercise program or a stretching program three times a week for 12 weeks. Resting HRV was measured in time and\\u000a frequency domains

Cédric T. Albinet; Geoffroy Boucard; Cédric A. Bouquet; Michel Audiffren

2010-01-01

367

EFFECT OF TWO SELECTED YOGIC BREATHING TECHNIQUES ON HEART RATE VARIABILITY  

Microsoft Academic Search

The heart rate variability (HRV) is an indicator of the cardiac autonomic control. Two spectral components are usually recorded, viz. high frequency (0.15- 0.50 Hz), which is due to vagal efferent activity and a low frequency component (0.05- 0.15 Hz), due to sympathetic activity. The present study was conducted to study the HRV in two yoga practices which have been

P. Raghuraj; A. G. Ramakrishnan; H. R. Nagendra; Shirley Telles

368

Circadian rhythm of spectral indices of heart rate variability in healthy subjects  

Microsoft Academic Search

Circadian pattern of heart rate variability spectral indices, including hourly, 24-hour, night, day, morning, and sex-adjusted measures of low frequency (LF), high frequency (HF), and LF\\/HF, was evaluated in healthy persons in 24-hour 3-lead electrocardiogram. HF showed circadian pattern with the greatest night values and LF\\/HF with the smallest night values. Peaks of hourly LF were found between 5 and

Andrzej Bilan; Agnieszka Witczak; Robert Palusi?ski; Wojciech My?li?ski; Janusz Hanzlik

2005-01-01

369

Face immersion increases vagal activity as assessed by heart rate variability  

Microsoft Academic Search

We examined whether the diving reflex without breath-holding (face immersion alone) increases vagal activity, as determined\\u000a by heart rate variability. A group of 15 men [mean age 20 (SD 3) years, height 172 (SD 5)?cm, body mass 68 (SD 9)?kg] performed\\u000a 12 trials at various breathing frequencies (5, 10, 15, 20, 30 breaths?·?min?1 and uncontrolled breath) with or without face

Naoyuki Hayashi; Mutsuhisa Ishihara; Ayumu Tanaka; Tomonori Osumi; Takayoshi Yoshida

1997-01-01

370

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

371

Smooth Scheduling under Variable Rates or the Analog-Digital Confinement Game  

Microsoft Academic Search

This work considers non-terminating scheduling problems in which a system of multiple resources serves clients having variable\\u000a needs. The system has m identical resources and n clients; in each time slot each resource may serve at most one client; in each such slot t each client ? has a rate, a real number ?\\u000a \\u000a ?\\u000a (t), that specifies his needs

Ami Litman; Shiri Moran-schein

2009-01-01

372

Analysis of rapid heart rate variability in the assessment of anticholinergic drug effects in humans  

Microsoft Academic Search

Anticholinergic agents have widespread therapeutic indications in clinical medicine. In addition, certain other drug groups–such as neuroleptics, antidepressants and antihistamines–possess distinct anticholinergic properties that reduce tolerance and compliance. Especially in patients with heart disease, attention should be paid to cardiac anticholinergic drug effects. The analysis of short-term heart rate variability (HRV) provides a noninvasive tool to estimate vagal cholinergic outflow.

Jani Penttilä; Tom Kuusela; Harry Scheinin

2005-01-01

373

Spatial variability of soil metabolic rate along a dryland elevation gradient  

Microsoft Academic Search

A general framework of ecosystem hotspots suggests variation in soil metabolic activity can be understood through the relative\\u000a distribution and intensity of patches of disproportionately high ecosystem process rates. To better understand the causes\\u000a of soil metabolic spatial variability and the variation in ecosystem hotspots we quantified soil respiration (R) spatial heterogeneity\\u000a across a network of seven sites spanning a

A. Chatterjee; G. D. Jenerette

374

Performance study of variable-rate modulation for underwater communications based on experimental data  

Microsoft Academic Search

In this paper, we present an analysis of the performance of a variable-rate adaptive modulation system based on instantaneous SNR information. The SNR traces we consider are part of the SubNet'09 experimental dataset, and have been derived by processing an hyperbolic frequency-modulated signal in the 9-14 kHz band. We start by deriving the high level behavior of the channel in

Beatrice Tomasi; Laura Toni; Paolo Casari; Lorenzo Rossi; Michele Zorzi

2010-01-01

375

Real-time detection of workload changes using heart rate variability  

Microsoft Academic Search

This work presents a novel approach to detecting real-time changes in workload using heart rate variability (HRV). We propose that for a given workload state, the values of HRV vary in a sub-range of a Gaussian distribution. We describe methods to monitor a HRV signal in real-time for change points based upon sub-Gaussian fitting. We tested our method on subjects

Adam Hoover; Anirud Singh; Stephanie Fishel-Brown; Eric Muth

376

The effect of endurance training on resting heart rate variability in sedentary adult males  

Microsoft Academic Search

.   Eleven previously sedentary adult males, serving as the experimental (EXP) group [mean (SE) age 36.6 (1.7) years, body mass\\u000a 87.2 (4.3) kg, body mass index, BMI, 28.4 (1.5) kg·m–2] participated in a 16-week supervised exercise program (3 days·week–1, 30 min·day–1, at ?80% of heart rate reserve) to determine the temporal effects of a moderate-to-vigorous-intensity exercise program on\\u000a heart rate variability (HRV). Five sedentary males

Edward L. Melanson; Patty S. Freedson

2001-01-01

377

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

NASA Astrophysics Data System (ADS)

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

Lin, D. C.; Sharif, A.

2010-06-01

378

Stress classification by separation of respiratory modulations in heart rate variability using orthogonal subspace projection.  

PubMed

The influence of respiration on the heart rate is a phenomenon known as respiratory sinus arrhythmia. However, effects of respiration are often ignored in studies of heart rate variability. In this paper, we take respiratory influences into account by separating the tachogram in two components, one related to respiration and one residual component, using orthogonal subspace projection. We demonstrate that it is important to remove respiratory influences during classification of rest and mental stress. Using merely the original tachogram, the classification accuracy is 57.13%, while the use of the residual tachogram results in an almost perfect classification (accuracy = 97.88%). PMID:24111137

Widjaja, Devy; Vlemincx, Elke; Van Huffel, Sabine

2013-07-01

379

Bridgman Solidification of Concentrated GaInSb Alloys with Variable Growth Rate  

SciTech Connect

Experimental works and numerical simulations on concentrated Ga1-xInxSb alloys directional solidification at high crucible pulling rates, show a damping solutal effect on the thermally driven convection which leads to a significant increase of the chemical heterogeneity of the sample and of the solid-liquid interface curvature. Analytical calculations which give a quantitative description of the solutal effect, show that the melt convection damping can be avoided if low pulling rates of the crucible are used for the growth process. A Bridgman growth method, which uses a variable pulling rate in order to reduce the damping solutal effect and to improve the axial chemical homogeneity of the sample, is numerically investigated. The growth process can be started at high pulling rates which are reduced progressively during the solidification. From the numerical modeling, it is found that the axial and radial variations of solute concentration as well as the interface curvature are maintained at lower values when variables pulling rates are used for Bridgman solidification of high doped alloys.

Stelian, C. [Department of Physics, West University of Timisoara, Bd.V.Parvan, No.4, 1900 Timisoara (Romania); Mitric, A.; Duffar, T. [EPM, ENSHMG, BP-95, 38402 St.Martin d'Heres (France); Corregidor, V.; Alves, L.C.; Barradas, N.P. [LFI, Nuclear and Technological Institute, E.N.10, 2686-953 Sacavem (Portugal)

2004-11-30

380

Assessment of cardiac autonomic functions by heart rate recovery, heart rate variability and QT dynamicity parameters in patients with acromegaly.  

PubMed

Cardiovascular complications are the most common causes of morbidity and mortality in acromegaly. However, there is little data regarding cardiac autonomic functions in these patients. Herein, we aimed to investigate several parameters of cardiac autonomic functions in patients with acromegaly compared to healthy subjects. We enrolled 20 newly diagnosed acromegalic patients (55 % female, age:45.7 ± 12.6 years) and 32 age- and gender-matched healthy subjects. All participants underwent 24 h Holter recording. Heart rate recovery (HRR) indices were calculated by subtracting 1st, 2nd and 3rd minute heart rates from maximal heart rate. All patients underwent heart rate variability (HRV) and QT dynamicity analysis. Baseline characteristics were similar except diabetes mellitus and hypertension among groups. Mean HRR1 (29.2 ± 12.3 vs 42.6 ± 6.5, p = 0.001), HRR2 (43.5 ± 15.6 vs 61.1 ± 10.8, p = 0.001) and HRR3 (46.4 ± 16.2 vs 65.8 ± 9.8, p = 0.001) values were significantly higher in control group. HRV parameters as, SDNN [standard deviation of all NN intervals] (p = 0.001), SDANN [SD of the 5 min mean RR intervals] (p = 0.001), RMSSD [root square of successive differences in RR interval] (p = 0.001), PNN50 [proportion of differences in successive NN intervals >50 ms] (p = 0.001) and high-frequency [HF] (p = 0.001) were significantly decreased in patients with acromegaly; but low frequency [LF] (p = 0.046) and LF/HF (p = 0.001) were significantly higher in acromegaly patients. QTec (p = 0.009), QTac/RR slope (p = 0.017) and QTec/RR slope (p = 0.01) were significantly higher in patients with acromegaly. Additionally, there were significant negative correlation of disease duration with HRR2, HRR3, SDNN, PNN50, RMSSD, variability index. Our study results suggest that cardiac autonomic functions are impaired in patients with acromegaly. Further large scale studies are needed to exhibit the prognostic significance of impaired autonomic functions in patients with acromegaly. PMID:23553172

Dural, Muhammet; Kabakc?, Giray; C?nar, Ne?e; Erba?, Tomris; Canpolat, U?ur; Gürses, Kadri Murat; Tokgözo?lu, Lale; Oto, Ali; Kaya, Ergün Bar??; Yorgun, Hikmet; Sahiner, Levent; Da?delen, Selçuk; Aytemir, Kudret

2013-04-01

381

Variables  

NSDL National Science Digital Library

This site, presented by Statistics Canada, is a section from "Statistics: Power from Data!" on variable classification. It discusses categorical and numerical variables and their types. The site discusses these variables: nominal, ordinal, numeric, continuous, and discrete. This is a good introductory site for any mathematics classroom studying statistics.

2008-12-25

382

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

383

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine  

Microsoft Academic Search

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim

Rosangela Poletto; Andrew M. Janczak; Ruth M. Marchant-Forde; Jeremy N. Marchant-Forde; Donald L. Matthews; Carol A. Dowell; Daniel F. Hogan; Lynetta J. Freeman; Donald C. Lay

2011-01-01

384

Variability of the Cosmic-Ray Ionization Rate in Diffuse Molecular Clouds  

NASA Astrophysics Data System (ADS)

The energy spectrum of cosmic-rays - a product of particle acceleration and subsequent diffusion - is generally assumed to be uniform throughout the Galaxy. As a result, the cosmic-ray ionization rate inferred in similar environments (e.g. in several diffuse clouds) should also be relatively constant. However, current estimates of the ionization rate in diffuse molecular clouds vary over the range (1-8)×10^{-16} s^{-1}. In addition, there are a few sight lines with 3? upper limits of ?_2<1×10^{-16} s^{-1}, suggesting even lower ionization rates in some clouds. This roughly order of magnitude difference in the cosmic-ray ionization rate between sight lines contradicts the concept of a spatially uniform cosmic-ray flux. We present cosmic-ray ionization rates derived from several published and unpublished spectroscopic observations of H_3^+ in diffuse cloud sight lines. These ionization rates are then compared with various other parameters (Galactic latitude, Galactic longitude, hydrogen column density) in a search for correlations. Also, sight lines in close proximity are compared to each other to determine the variability of the ionization rate on small spatial scales. Webber, W. R. 1998, ApJ, 506, 329 Indriolo, N., Geballe, T. R., Oka, T., & McCall, B. J. 2007, ApJ, 671, 1736 McCall B. J., et al. 2002, ApJ, 567, 391

Indriolo, Nick; Geballe, Thomas R.; Oka, Takeshi; McCall, Benjamin J.

2009-06-01

385

Analysis of heart rate variability in individuals subjected to different positive end expiratory pressure levels using expiratory positive airway pressure  

PubMed Central

Introduction The increase in the number of studies has led to greater security in the application of this method and the determination of its effectiveness in adults.. The purpose of the present study was to evaluate heart rate variability in healthy individuals submitted to different levels of positive expiratory pressure using an expiratory positive airway pressure (EPAP) device. Material and methods The study involved 27 healthy male individuals ranging in age from 20 to 35 years. Patient histories were taken and the subjects were submitted to a physical examination. The volunteers were monitored using the Polar 810s® and submitted to the EPAP experiment. Analyses were performed on variables of the frequency domain. Sympathetic and parasympathetic bands and their relationship with sympathovagal response were also analyzed. Results The mean value of this variable was 526.89 (55.50) ms2 in the first period, 2811.0 (721.10) ms2 in the fourth period and 726.52 (123.41) ms2 in the fifth period. Regarding the parasympathetic area, significant differences were detected when Periods 1 and 5 (no load) were compared with periods in which the individuals were subjected to the use of the therapy. Sympathetic and parasympathetic areas together, a significant difference was detected regarding the sympathetic/parasympathetic ratio in the comparison between Periods 1 and 4 (p < 0.01) as well as Periods 2 and 4 (p < 0.05). Conclusions The findings of the present study suggest that the therapeutic use of EPAP significantly alters the parameters of heart rate variability in the frequency domain, highlighting the importance of monitoring and care during the practice of EPAP.

Pinto, Thiago Lorentz; Costa, Ivan Peres; Kawaguchi, Leandro Yukio Alves; de Carvalho, Flavio Aimbire Soares; de Carvalho, Regiane Albertini

2013-01-01

386

Evaluation of the effects of duloxetine and escitalopram on 24-hour heart rate variability: a mechanistic study using heart rate variability as a pharmacodynamic measure.  

PubMed

A decrease in heart rate variability (HRV) can indicate increased sympathetic nervous system activity and possibly increased norepinephrine levels. In this randomized, placebo- and escitalopram (ESC)-controlled, subject-blind, 2-period, crossover study, 26 healthy subjects 50 to 65 years old received duloxetine (DLX) 60 mg once daily or ESC 20 mg once daily for 11 days, each in sequential study periods separated by a 10-day or more washout period. Continuous electrocardiogram recordings were obtained by Holter monitoring (baseline, day 9, and day 10 of treatment). Duloxetine and ESC did not produce any clinically significant effects on standard measures of HRV, which included SD of normal R-R intervals and the root mean square difference among successive R-R normal intervals index values, mean change in SD of normal R-R intervals, and frequency domain analysis. However, treatment with DLX was associated with significantly less change from baseline in total beats per 24 hours than ESC, which was an unexpected finding compared with previous observations in which vital signs were measured at a specific time point while awake. In conclusion, in healthy adults exposed to DLX or ESC, no clinically significant effects on HRV were observed. PMID:23422380

Chappell, Jill C; Kovacs, Richard; Haber, Harry; Wright, Ryan; Mitchell, Malcolm I; Detke, Michael; Pangallo, Beth

2013-04-01

387

Real-time Continuous Assessment Method for Mental and Physiological Condition using Heart Rate Variability  

NASA Astrophysics Data System (ADS)

It is necessary to monitor the daily health condition for preventing stress syndrome. In this study, it was proposed the method assessing the mental and physiological condition, such as the work stress or the relaxation, using heart rate variability at real time and continuously. The instantanuous heart rate (HR), and the ratio of the number of extreme points (NEP) and the number of heart beats were calculated for assessing mental and physiological condition. In this method, 20 beats heart rate were used to calculate these indexes. These were calculated in one beat interval. Three conditions, which are sitting rest, performing mental arithmetic and watching relaxation movie, were assessed using our proposed algorithm. The assessment accuracies were 71.9% and 55.8%, when performing mental arithmetic and watching relaxation movie respectively. In this method, the mental and physiological condition was assessed using only 20 regressive heart beats, so this method is considered as the real time assessment method.

Yoshida, Yutaka; Yokoyama, Kiyoko; Ishii, Naohiro

388

Dietary sodium effects on heart rate variability in salt sensitivity of blood pressure.  

PubMed

High dietary sodium intake is a risk factor for hypertension, and heart rate variability (HRV) is decreased in hypertension. Effects of dietary sodium intake on HRV of normotensive persons have not, however, been investigated to date. The present study examined effects of low and high sodium diets on blood pressure, heart rate, and HRV in 36 healthy, normotensive women, ages 40-70. Each was placed on a low sodium diet for 6 days followed by a high sodium diet for 6 days. The high salt diet increased mean systolic blood pressure, decreased heart rate, and increased high frequency HRV (HF). Cardiac vagal tone, estimated at baseline from heart period and a time domain estimate of respiratory sinus arrhythmia, was higher in salt-sensitive than salt-insensitive subjects. The finding of increased vagal tone in normotensive persons on high salt intake indicates that dietary sodium status should be considered in behavioral studies of HRV. PMID:18047481

McNeely, Jessica D; Windham, B Gwen; Anderson, David E

2007-11-28

389

The use of heart rate variability in assessing precompetitive stress in high-standard judo athletes.  

PubMed

The objective of this study is to examine the sensitivity to and changes in heart rate variability (HRV) in stressful situations before judo competitions and to observe the differences among judo athletes according to their competitive standards in both official and unofficial competitions. 24 (10 male and 14 female) national- and international-standard athletes were evaluated. Each participant answered the Revised Competitive State Anxiety Inventory (CSAI-2R) and their HRV was recorded both during an official and unofficial competition. The MANOVA showed significant main effects of the athlete's standard and the type of competition in CSAI-2R, in HRV time domain, in HRV frequency domain and in HRV nonlinear analysis (p<0.05). International-standard judo athletes have lower somatic anxiety, cognitive anxiety, heart rate and low-high frequency ratio than national-standard athletes (p<0.05). International-standard athletes have a higher confidence, mean RR interval, standard deviation of RR, square root of the mean squared difference of successive RR intervals, number of consecutive RR that differ by more than 5 ms, short-term variability, long-term variability, long-range scaling exponents and short-range scaling exponent than national-standard judo athletes. In conclusion, international-standard athletes show less pre-competitive anxiety than the national-standard athletes and HRV analysis is sensitive to changes in pre-competitive anxiety. PMID:22972248

Morales, J; Garcia, V; García-Massó, X; Salvá, P; Escobar, R; Buscà, B

2012-09-12

390

Rates of ingestion and their variability between individual calanoid copepods: Direct observations  

SciTech Connect

The goals of this study were to determine rates of ingestion and fecal pellet release, and their variability, for individual planktonic copepods over extended periods of time (>20 min). Ingestions and rejections of individual cells of the diatom Thalassiosira eccentrica by a adult females of the calanoid Paracalanus aculeatus were directly quantified by observing individual copepods continuously at cell concentrations ranging from 0.1 to 1.2 mm{sup 3} l{sup {minus}1}. Average ingestion rates increased with increasing food concentration, but were not significantly different between 0.3 and 1.0 mm{sup 3} l{sup {minus}1} (9.8 and 32.7 {mu}g Cl{sup {minus}1}) of T.eccentrica. Rates of cell rejections were low and similar at 0.1 and 0.3. but were significantly higher at 1.0 mm{sup 3} l{sup {minus}1}. The coefficients of variation for average ingestion rates of individual copepods hardly differed between food concentrations, ranging from 17 to 22%, and were close to those for average fecal pellet release intervals which ranged from 15 to 21%. A comparison between individuals at each food concentration found no significant differences at 1.0; at 0.1 and 0.3 mm{sup 3} l{sup {minus}1}, respectively, ingestion rates of four out of five females did not differ significantly from each other. Average intervals between fecal pellet releases were similar at 0.3 and 1.0 mm{sup 3} l{sup {minus}1}. Fecal pellet release intervals between individuals were significantly different at each food concentration; these significant differences were attributed to rather narrow ranges of pellet release intervals of each individual female. Potential sources/causes of variability in the sizes and rates of copepods in the ocean are evaluated.

Paffenhoefer, G.A.; Lewis, K.D. [Skidaway Inst. of Oceanography, Savannah, GA (United States); Bundy, M.H. [Skidaway Inst. of Oceanography, Savannah, GA (United States)]|[Alfred-Wegener-Institut fuer Polar- und Meeresforschung, Bremerhaven (Germany). Inst. fuer Fernerkundung (IFE); Metz, C. [Alfred-Wegener-Institut fuer Polar- und Meeresforschung, Bremerhaven (Germany). Inst. fuer Fernerkundung (IFE)

1995-12-01

391

Maximum Application Rates for Land Treatment of Septage.  

National Technical Information Service (NTIS)

Two years of data from a three year study indicates septage application rates of 1120 and 1500 kg/ha of nitrogen resulted in increased concentrations of nitrates in soil water extracts for a Hubbard loamy sand, Waukegan silt loam and Lester clay loam. Nit...

C. J. Clanton R. E. Machmeir J. L. Anderson M. J. Hansel

1983-01-01

392

A simple method of fetal and neonatal heart rate beat-to-beat variability quantitation: preliminary report.  

PubMed

Good base-line fetal and neonatal heart rate beat-to-beat variability appears to be a reassuring sign of well-being. Conversely, decreased base-line heart rate beat-to-beat variability during the latter part of the intrapartum period is often associated with neonatal acidosis and/or depression. A simple method of quantitation of the beat-to-beat neonatal heart rate is reported here. This method of variability quantitation (VQ) consists of a continuous integration and display of the baseline heart rate beat-to-beat variability on a scale of zero to four, expressed in beats per minute averaged over a one-minute period. Serial variability quantitation in 35 neonates with different clinical conditions appeared to demonstrate a good correlation between the variability quantitation and the outcome of the neonates. Further studies are planned for evaluating the method in the intrapartum period. PMID:851144

Modanlou, H D; Freeman, R K; Braly, P

1977-04-15

393

Depressed heart rate variability is associated with events in patients with stable coronary artery disease and preserved left ventricular function  

Microsoft Academic Search

Background: Little is known about the value of heart rate variability in patients with symptomatic coronary artery disease with a preserved left ventricular function. We hypothesized that in these patients heart rate variability might be a helpful adjunct to conventional parameters to predict clinical events. Methods: In a prospective 2-year follow-up study ambulatory electrocardiographic recordings were performed in 263 consecutive

Ad J. van Boven; J. Wouter Jukema; Jaap Haaksma; Aeilko H. Zwinderman; Harry J. G. M. Crijns; Kong I. Lie

1998-01-01

394

Severe depression is associated with markedly reduced heart rate variability in patients with stable coronary heart disease  

Microsoft Academic Search

Objective: The purpose of this study was to investigate the relationship between depression and heart rate variability in cardiac patients. Methods: Heart rate variability was measured during 24-hour ambulatory electrocardiographic (ECG) monitoring in 40 medically stable out-patients with documented coronary heart disease meeting current diagnostic criteria for major depression, and 32 nondepressed, but otherwise comparable, patients. Patients discontinued ?-blockers and

Phyllis K Stein; Robert M Carney; Kenneth E Freedland; Judith A Skala; Allan S Jaffe; Robert E Kleiger; Jeffrey N Rottman

2000-01-01

395

Evaluation of the Effect of Heat Exposure on the Autonomic Nervous System by Heart Rate Variability and Urinary Catecholamines  

Microsoft Academic Search

Evaluation of the Effect of Heat Exposure on the Autonomic Nervous System by Heart Rate Variability and Urinary Catecholamines: Shinji YAMAMOTO, et al. Department of Hygiene, Yamaguchi University Graduate School of Medicine—The aim of this study was to investigate the usefulness of heart rate variability (HRV) and urinary catecholamines (CA) as objective indices of heat stress effect. We examined physiological

Shinji Yamamoto; Mieko Iwamoto; Masaiwa Inoue; Noriaki Harada

2007-01-01

396

HRV: THE MANUFACTURERS AND VENDORS SPEAK The Portable StressEraser Heart Rate Variability Biofeedback Device: Background and Research  

Microsoft Academic Search

Heart rate variability biofeedback is a burgeoning clinical intervention for a variety of disorders. This paper describes a handheld heart rate variability biofeedback device called the StressEraser. The role of home training devices, the device algorithm and biofeedback method, and current research findings are highlighted. Additional attention is paid to the importance of user preferences and compliance with home practice

Frederick Muench

397

Effects of controlled breathing, mental activity and mental stress with or without verbalization on heart rate variability  

Microsoft Academic Search

OBJECTIVESTo assess whether talking or reading (silently or aloud) could affect heart rate variability (HRV) and to what extent these changes require a simultaneous recording of respiratory activity to be correctly interpreted.BACKGROUNDSympathetic predominance in the power spectrum obtained from short- and long-term HRV recordings predicts a poor prognosis in a number of cardiac diseases. Heart rate variability is often recorded

Luciano Bernardi; Joanna Wdowczyk-Szulc; Cinzia Valenti; Stefano Castoldi; Claudio Passino; Giammario Spadacini; Peter Sleight

2000-01-01

398

Computer-based analysis of heart rate variability signal for detection of sleep disordered breathing in children  

Microsoft Academic Search

A computer-based analysis system was developed to display and analyze heart rate variability (HRV). ECG, oxygen saturation and respiratory signals (airflow, abdominal and thoracic movements), were used as raw data. The heart rate variability signal was derived from ECG by applying a Hilbert transform-based algorithm for reliable QRS complex detection. Following the guidelines suggested by the Task Force of the

H NazeranlF; Y. Pamula; A. Gradziel; K. Ung; S. Vijendra; K. Behbehani

2003-01-01

399

Third component in cataclysmic variables: Additional mechanism for accretion rate changes?  

NASA Astrophysics Data System (ADS)

An additional mechanism for variability of the characteristics of cataclysmic variables owed to accretion rate changes is discussed. Small variations of the distance between the components owed to the presence of a third body -- brown dwarf or a giant planet -- may cause much larger response amplified by a strong dependence of the accretion rate on the radius excess of the Roche lobe-filling secondary as well as by the irradiation. This mechanism makes accretion rate variations more complicated as compared with the models of solar-type activity of the secondary. One of the proposed candidates is EM Cyg, where a 3000-day cyclicity was found (Chinarova & Andronov 1996). A contribution of the red dwarf third body was detected in the emission from EM Cyg by North et al. (2001), but it is not clear, whether this star is physically related to the cataclysmic binary. Variations of the outburst cycle length are also seen in X Leo, AB Dra, IR Gem, AY Lyr, LL Lyr and some other stars. Another candidate is V792 Cyg, where a switch of the seasonal mean outburst cycle from 25--29d to ?39d was detected (Chinarova & Andronov 2000).

Andronov, I. L.; Chinarova, L. L.

2002-01-01

400

a Modified Symmetry Reduction Method and its Application in Nonlinear Variable Coefficient Evolution Equation(s)  

Microsoft Academic Search

Based on the one-parameter Lie group theory, we established a modified symmetry reduction method in solving nonlinear variable coefficient equations. Our study shows that the modified method can be applied in solving or reducing various nonlinear variable coefficient equations. In our initial applications, we have successfully obtained some exact solutions to the equations of nonlinear variable coefficients KdV and KP.

Cheng-Jie Bai; Hong Zhao; Xia Zhang; Heng-Ying Xu

2009-01-01

401

Separable nonlinear least squares: the variable projection method and its applications  

Microsoft Academic Search

In this paper we review 30 years of developments and applications of the variable projection method for solving separable nonlinear least-squares problems. These are problems for which the model function is a linear combination of nonlinear functions. Taking advantage of this special structure, the method of variable projections eliminates the linear variables obtaining a somewhat more complicated function that involves

Gene Golu; Victor Pereyra

2002-01-01

402

Quantifying Soil Variability in GIS Applications: II Spatial Distribution of Soil Properties  

Microsoft Academic Search

Application of Geographical Information Systems (GIS) to environmental problems requires a spatial delineation of soil properties and some a priori knowledge of their variability. In the U.S.A. estimated soil properties are available from soil surveys published by the National Cooperative Soil Survey. However, information on the extent and nature of their variability is generally lacking. To remedy the situation, variability

A. S. Rogowski

1996-01-01

403

Spatial scaling of avian population dynamics: population abundance, growth rate, and variability.  

PubMed

Synchrony in population fluctuations has been identified as an important component of population dynamics. In a previous study, we determined that local-scale (<15-km) spatial synchrony of bird populations in New England was correlated with synchronous fluctuations in lepidopteran larvae abundance and with the North Atlantic Oscillation. Here we address five questions that extend the scope of our earlier study using North American Breeding Bird Survey data. First, do bird populations in eastern North America exhibit spatial synchrony in abundances at scales beyond those we have documented previously? Second, does spatial synchrony depend on what population metric is analyzed (e.g., abundance, growth rate, or variability)? Third, is there geographic concordance in where species exhibit synchrony? Fourth, for those species that exhibit significant geographic concordance, are there landscape and habitat variables that contribute to the observed patterns? Fifth, is spatial synchrony affected by a species' life history traits? Significant spatial synchrony was common and its magnitude was dependent on the population metric analyzed. Twenty-four of 29 species examined exhibited significant synchrony in population abundance: mean local autocorrelation (rho)= 0.15; mean spatial extent (mean distance where rho=0) = 420.7 km. Five of the 29 species exhibited significant synchrony in annual population growth rate (mean local autocorrelation = 0.06, mean distance = 457.8 km). Ten of the 29 species exhibited significant synchrony in population abundance variability (mean local autocorrelation = 0.49, mean distance = 413.8 km). Analyses of landscape structure indicated that habitat variables were infrequent contributors to spatial synchrony. Likewise, we detected no effects of life history traits on synchrony in population abundance or growth rate. However, short-distance migrants exhibited more spatially extensive synchrony in population variability than either year-round residents or long-distance migrants. The dissimilarity of the spatial extent of synchrony across species suggests that most populations are not regulated at similar spatial scales. The spatial scale of the population synchrony patterns we describe is likely larger than the actual scale of population regulation, and in turn, the scale of population regulation is undoubtedly larger than the scale of individual ecological requirements. PMID:18027754

Jones, Jason; Doran, Patrick J; Holmes, Richard T

2007-10-01

404

Effect of immersion, submersion, and scuba diving on heart rate variability  

PubMed Central

Background—Heart rate variability (HRV) describes the cyclic variations in heart rate and offers a non-invasive tool for investigating the modulatory effects of neural mechanisms elicited by the autonomic nervous system on intrinsic heart rate. Objective—To introduce the HRV concept to healthy volunteers under control conditions and during scuba diving. In contrast with more established manoeuvres, diving probably activates both the sympathetic and parasympathetic nervous system through various stimuli—for example, through cardiac stretch receptors, respiration pattern, psychological stress, and diving reflex. A further aim of the study was to introduce a measure for determining a candidate's ability to scuba dive by providing (a) standard values for HRV measures (three from the time domain and three from the frequency domain) and (b) physiological responses to a strenuous manoeuvre such as scuba diving. Methods—Twenty five trained scuba divers were investigated while diving under pool conditions (27°C) after the effects of head out immersion and submersion on HRV had been studied. Results and conclusions—(a) Immersion under pool conditions is a powerful stimulus for both the sympathetic and parasympathetic nervous system. (b) As neither the heart rate nor the HRV changed on going from immersion to submersion, the parasympathetic activation was probably due to haemodynamic alterations. (c) All HRV measures showed an increase in the parasympathetic activity. (d) If a physiological HRV is a mechanism for providing adaptability and flexibility, diving should not provoke circulatory problems in healthy subjects. (e) Either a lower than normal HRV under control conditions or a reduction in HRV induced by diving would be unphysiological, and a scuba diving candidate showing such characteristics should be further investigated. Key Words: immersion; submersion; scuba diving; autonomous nervous system; heart rate variability

Schipke, J; Pelzer, M

2001-01-01

405

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

406

A variable fork rate affects timing of origin firing and S phase dynamics in Saccharomyces cerevisiae.  

PubMed

Activation (in the following referred to as firing) of replication origins is a continuous and irreversible process regulated by availability of DNA replication molecules and cyclin-dependent kinase activities, which are often altered in human cancers. The temporal, progressive origin firing throughout S phase appears as a characteristic replication profile, and computational models have been developed to describe this process. Although evidence from yeast to human indicates that a range of replication fork rates is observed experimentally in order to complete a timely S phase, those models incorporate velocities that are uniform across the genome. Taking advantage of the availability of replication profiles, chromosomal position and replication timing, here we investigated how fork rate may affect origin firing in budding yeast. Our analysis suggested that patterns of origin firing can be observed from a modulation of the fork rate that strongly correlates with origin density. Replication profiles of chromosomes with a low origin density were fitted with a variable fork rate, whereas for the ones with a high origin density a constant fork rate was appropriate. This indeed supports the previously reported correlation between inter-origin distance and fork rate changes. Intriguingly, the calculated correlation between fork rate and timing of origin firing allowed the estimation of firing efficiencies for the replication origins. This approach correctly retrieved origin efficiencies previously determined for chromosome VI and provided testable prediction for other chromosomal origins. Our results gain deeper insights into the temporal coordination of genome duplication, indicating that control of the replication fork rate is required for the timely origin firing during S phase. PMID:23850861

Supady, Adriana; Klipp, Edda; Barberis, Matteo

2013-07-09

407

Power spectral analysis of heart rate variability during positive pressure pneumoperitoneum  

Microsoft Academic Search

Background  Positive pressure pneumoperitoneum (PPP) effects on the autonomic nervous system (ANS) might be of clinical importance, as\\u000a imbalance in the autonomic cardiac control might lead to serious consequences.\\u000a \\u000a \\u000a \\u000a Methods  Fifteen healthy patients undergoing elective laparoscopic cholecystectomy were analyzed for cardiac autonomic nervous activity\\u000a by spectral heart rate variability, during awake state, before and after intubation, during CO2 PPP (14 mmHg), and

A. Bickel; M. Yahalom; N. Roguin; R. Frankel; J. Breslava; S. Ivry; A. Eitan

2002-01-01

408

Interval training in elderly men increases both heart rate variability and baroreflex activity  

Microsoft Academic Search

\\u000a Abstract\\u000a \\u000a Aims\\u000a   Autonomic nervous system activity decreases continuously with age and appears to be a powerful predictor of disease and death. Attempts are thus made to reactivate autonomic drive with the intent of improving health.\\u000a Methods\\u000a   We assessed maximal oxygen consumption (VO2max), auto- nomic nervous system activity by heart rate variability (HRV) analysis and spontaneous cardiac baroreflex activity (SBR) in

Vincent Pichot; Frédéric Roche; Christian Denis; Martin Garet; David Duverney; Frédéric Costes; Jean-Claude Barthélémy

2005-01-01

409

Deficient orexinergic modulation in narcolepsy may influence heart rate variability in sleep  

Microsoft Academic Search

Summary\\u000a Question of the study  Because impaired orexinergic modulation may have an impact on autonomic nervous functions, a spectral analysis of heart rate\\u000a variability (HRV) was used to detect autonomic impairment in narcolepsy.\\u000a \\u000a \\u000a \\u000a Patients and methods  Ten narcoleptic patients (eight never treated and two after discontinuation of therapy) and 10 sex- and age-matched controls\\u000a underwent a spectral analysis of HRV in the

Petr Busek; Jitka Vankova; Jaroslav Opavsky; Jiri Salinger; sona Nevsimalova

2005-01-01

410

Changes in short-term measures of heart rate variability after eight weeks of cardiac rehabilitation  

Microsoft Academic Search

Background  In coronary artery disease (CAD) and following myocardial infarction (MI), activity of the autonomic nervous system is altered.\\u000a Reduced heart rate variability (HRV) is a risk factor for future cardiac event. Studies reporting changes in HRV post-cardiac\\u000a rehabilitation (CR) are heterogeneous, due possibly to varied data collection and analysis protocols.\\u000a \\u000a \\u000a \\u000a Aim  To evaluate changes in spectral measures of HRV derived from

Gavin R. H. Sandercock; Richard Grocott-Mason; David A. Brodie

2007-01-01

411

The influence of age on heart rate variability during morning wakefulness  

Microsoft Academic Search

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

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

2010-01-01

412

Autonomic dysfunction in vitamin B12 deficiency: A heart rate variability study  

Microsoft Academic Search

This study was arranged to examine whether vitamin B12 deficiency may cause autonomic dysfunction. Time-domain and long-term frequency-domain heart rate variability parameters from 12 patients with pernicious anemia were compared to 12 age and sex matched controls. In B12 deficient patient group time-domain parameters; SDNN (100.4±37.86 vs. 131.91±26.94, P=0.05), SDANN (87.00±37.77 vs. 118.83±26.22, P=0.05) SD (39.41±13.32 vs. 53.41±15.39, P=0.0221), rMSSD

Ahmet Bilge Sözen; ?eref Demirel; Vakur Akkaya; Hasan Kudat; Tufan Tükek; Mustafa Yeneral; Mustafa Özcan; Özen Güven; Ferruh Korkut

1998-01-01

413

Correlation structures in short-term variabilities of stock indices and exchange rates  

NASA Astrophysics Data System (ADS)

Financial data usually show irregular fluctuations and some trends. We investigate whether there are correlation structures in short-term variabilities (irregular fluctuations) among financial data from the viewpoint of deterministic dynamical systems. Our method is based on the small-shuffle surrogate method. The data we use are daily closing price of Standard & Poor's 500 and the volume, and daily foreign exchange rates, Euro/US Dollar (USD), British Pound/USD and Japanese Yen/USD. We found that these data are not independent.

Nakamura, Tomomichi; Small, Michael

2007-09-01

414

Fetal acid–base balance after betamethasone administration: relation to fetal heart rate variability  

Microsoft Academic Search

Objective  To explore whether the known decrease in fetal heart rate variability, which follows antenatal betamethasone administration\\u000a is related to fetal acid–base changes.\\u000a \\u000a \\u000a \\u000a Methods  A retrospective study of 42 women with premature delivery following a single course of betamethasone. The study group consisted\\u000a of 21 women who delivered within 48 h following first injection of betamethasone. The 21 women who delivered later than

Simon Shenhav; Michael Volodarsky; Eyal Y. Anteby; Ofer Gemer

2008-01-01

415

Cortisol release, heart rate and heart rate variability in the horse and its rider: Different responses to training and performance.  

PubMed

Although some information exists on the stress response of horses in equestrian sports, the horse-rider team is much less well understood. In this study, salivary cortisol concentrations, heart rate (HR) and heart rate variability (HRV), SDRR (standard deviation of beat-to-beat interval) and RMSSD (root mean square of successive beat-to-beat intervals) were analysed in horses and their riders (n=6 each) at a public performance and an identical rehearsal that was not open to the public. Cortisol concentrations increased in both horses and riders (P<0.001) but did not differ between performance and rehearsal. HR in horses and riders increased during the rehearsal and the public performance (P<0.001) but the increase in HR was more pronounced (P<0.01) in riders than in their horses during the public performance (from 91±10 to 150±15beats/min) compared to the rehearsal (from 94±10 to 118±12beats/min). The SDRR decreased significantly during the equestrian tasks in riders (P<0.001), but not in their horses. The RMSSD decreased in horses and riders (P<0.001) during rehearsal and performance, indicating a decrease in parasympathetic tone. The decrease in RMSSD in the riders was more pronounced (P<0.05) during the performance (from 32.6±6.6 to 3.8±0.3ms) than during the rehearsal (from 27.5±4.2 to 6.6±0.6ms). The study has shown that the presence of spectators caused more pronounced changes in cardiac activity in the riders than it did in their horses. PMID:23380228

von Lewinski, Mareike; Biau, Sophie; Erber, Regina; Ille, Natascha; Aurich, Jörg; Faure, Jean-Michel; Möstl, Erich; Aurich, Christine

2013-02-04

416

Dynamic Cardiovagal Response to Motion Sickness: A Point-Process Heart Rate Variability Study  

PubMed Central

A visual display of stripes was used to examine cardio-vagal response to motion sickness. Heart rate variability (HRV) was investigated using dynamic methods to discern instantaneous fluctuations in reaction to stimulus and perception-based events. A novel point process adaptive recursive algorithm was applied to the R-R series to compute instantaneous heart rate, HRV, and high frequency (HF) power as a marker of vagal activity. Results show interesting dynamic trends in each of the considered subjects. HF power averaged across ten subjects indicates a significant decrease 20s to 60s following the transition from “no nausea” to “mild.” Conversely, right before “strong” nausea, the group average shows a transient trending increase in HF power. Findings confirm gradual sympathetic activation with increasing nausea, and further evidence transitory increases in vagal tone before flushes of strong nausea.

LaCount, LT; Napadow, V; Kuo, B; Park, K; Kim, J; Brown, EN; Barbieri, R

2010-01-01

417

[Research on the relationship between sleep phases and heart rate variability].  

PubMed

The study of sleep phases is helpful to evaluate the sleep state and quality. In order to explore the relationship between heart rate variability (HRV) and sleep phases, detrended fluctuation analysis (DFA) and autoregressive (AR) model spectrum estimation were used to analyze R-R interval (RRI) sequence of 45 healthy subjects from Sleep Heart Rate and Stroke Volume Data Bank. The results show that, in different sleep phases, long-range correlation was detected in RRI sequence. From rapid eye movement to light sleep and deep sleep, scaling exponent alpha1 and alpha2 were decreasing, while spectral parameters LFn. u., HFn. u. and LF/HF showed increasing parasympathetic activity. Scaling exponents had more significant differences than spectral parameters in distinguishing different sleep phases. Thus, DFA will be a better analysis method to quantify HRV in different sleep stages. PMID:21485203

Jiang, Liyi; Wu, Xiaoming

2011-02-01

418

Time-optimal design for multidimensional and parallel transmit variable-rate selective excitation.  

PubMed

Variable-rate selective excitation (VERSE) is a radio frequency (RF) pulse reshaping technique. It is most commonly used to reduce the peak magnitude and specific absorption rate (SAR) of RF pulses by reshaping pulses and gradient waveforms to reduce RF magnitude while preserving excitation profiles. In this work, a general time-optimal VERSE algorithm for multidimensional and parallel transmit pulses is presented. Time optimality is achieved by translating peak RF limits to gradient upper bounds in excitation k-space. The limits are fed into a time-optimal gradient waveform design technique. Effective SAR reduction is achieved by reducing peak RF subject to a fixed pulse length. The presented method is different from other VERSE techniques in that it provides a noniterative time-optimal multidimensional solution, which drastically simplifies VERSE designs. Examples are given for 1D and 2D single channel and 2D parallel transmit pulses. PMID:19365849

Lee, Daeho; Lustig, Michael; Grissom, William A; Pauly, John M

2009-06-01

419

Synoptic-scale variability of satellite-derived sea-ice deformation rates in the Arctic  

NASA Astrophysics Data System (ADS)

Observational data show that deformation of the compact sea ice covering the central Arctic takes place within elongated, narrow zones separating semi-rigid floes. Localization of deformation, and a related intermittent character of internal stress in the ice, cannot be satisfactorily reproduced with present state-of-the-art numerical models, especially those based on various versions of viscous-plastic rheology. Similarly, sea-ice models do not reproduce properly the observed power-law tails of deformation-rate probability distributions (pdfs), with a slope depending on the scale of the observation. In order to be able to improve the models, one needs: (i) relevant quantitative measures of ice deformation rates that the models should aim to reproduce; (ii) a better understanding of the time variability of those measures (existing studies are usually limited to the analysis of single events) and their dependence on changes of the external forcing and of the properties of the ice itself. In this study, we use gridded sea-ice total deformation rates from the RGPS data provided by the RADARSAT-1 satellite, available for 11 winter seasons with a time resolution of 3 days and a spatial resolution of 12.55 km. The analysis is based on deformation-rate pdfs obtained by means of a rank-order analysis of the data for each snapshot in the dataset. We analyze the time variability of: (i) the slope of the power-law tails of the pdfs, estimated with a maximum-likelihood method; and (ii) the moments of the pdfs for a range of exponents q and spatial scales L from the original mesh size to approximately 1000 km. In all analyzed cases, the slope of the moments as a function of the length scale L increases (faster than linearly) with increasing power q. However, the tempo of this increase can be very different. Generally, there are two distinct, dominating patterns of variability, with the first pattern describing the overall level of deformation, and the second one being generally small, but peaking a number of times during a typical winter, during short periods of intense deformation. Further, we demonstrate that the moments of sea-ice deformation pdfs are highly correlated (with correlation coefficients in the order of 0.6-0.7) with a very simple quantity characterizing the strength of the atmospheric forcing on the ice, namely with the area-averaged 10-m wind speed over the Arctic Ocean. Finally, we sketch a theoretical explanation for the observed relationships between the sea-ice deformation rates and the wind forcing, based on simplified momentum equations and a very general rheology model of sea ice.

Herman, A.; G?owacki, O.

2012-04-01

420

Analysis of circadian rhythm changes in heart rate variability during chronic sound stress using an implantable biotelemetry system  

Microsoft Academic Search

Summary form only given. To study the circadian rhythm changes of the heart rate variability (HRV) during chronic sound stress, Wistar rats were implanted with telemetry transmitters and exposed to chronic ultrasound stress for 14 days. The heart rate, mean R-R intervals (mean R-R), and body temperature were monitored hourly. The spectra of five-minute heart rate variability were plotted on

H. Minamitani; H. Takeuchi; Y. Takiguchi

2001-01-01

421

Heart rate variability parameters correlate with functional independence measures in ischemic stroke patients.  

PubMed

This study gives quantitative information regarding the effect of brain infarction on the regulation of the cardiovascular system. Electrocardiograms of 16 patients, ranging from 54 to 85 years old, admitted for rehabilitation after an ischemic supratentorial stroke, all without a history of cardiac disease or rhythm disturbances, were recorded during physiotherapy effort. All patients were evaluated for the functional independence measure (FIM) score 48 to 72 hours following admission and repeated at one week before discharge. The heart rate variability (HRV) parameters: standard deviation (SD) of the RR series, the power spectrum of the RR intervals for the low frequency range (LF: 0.04-0.15 Hz), and the high frequency range (HF: 0.15-0.4 Hz) were calculated. The results showed that all heart rate variability parameters had statistically significant relationship with the FIM on admission and discharge scores. In conclusion, the HRV parameters correlate with the clinical measures of function: the greater the HRV parameter the higher the FIM score. The presented technique may prove useful as a prognostic tool providing a simple way for determining functional performance of stroke patients. PMID:12539134

Arad, Marina; Abboud, Shimon; Radai, Michal M; Adunsky, Abraham

2002-01-01

422

Study of Heart Rate Variability in Bipolar Disorder: Linear and Non-Linear Parameters during Sleep  

PubMed Central

The aim of the study is to define physiological parameters and vital signs that may be related to the mood and mental status in patients affected by bipolar disorder. In particular we explored the autonomic nervous system through the analysis of the heart rate variability. Many different parameters, in the time and in the frequency domain, linear and non-linear were evaluated during the sleep in a group of normal subject and in one patient in four different conditions. The recording of the signals was performed through a wearable sensorized T-shirt. Heart rate variability (HRV) signal and movement analysis allowed also obtaining sleep staging and the estimation of REM sleep percentage over the total sleep time. A group of eight normal females constituted the control group, on which normality ranges were estimated. The pathologic subject was recorded during four different nights, at time intervals of at least 1?week, and during different phases of the disturbance. Some of the examined parameters (MEANNN, SDNN, RMSSD) confirmed reduced HRV in depression and bipolar disorder. REM sleep percentage was found to be increased. Lempel–Ziv complexity and sample entropy, on the other hand, seem to correlate with the depression level. Even if the number of examined subjects is still small, and the results need further validation, the proposed methodology and the calculated parameters seem promising tools for the monitoring of mood changes in psychiatric disorders.

Migliorini, Matteo; Mendez, Martin O.; Bianchi, Anna M.

2012-01-01

423

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

PubMed Central

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.

Stephan-Blanchard, Erwan; Chardon, Karen; Leke, Andre; Delanaud, Stephane; Bach, Veronique; Telliez, Frederic

2013-01-01

424

Heart rate variability, norepinephrine and ECG changes in subarachnoid hemorrhage patients.  

PubMed

While electrocardiographic abnormalities in subarachnoid hemorrhage patients have been known since 1947, the provocative mechanism has not yet been satisfactorily explained. The purpose of this study was to evaluate with some tests, the role of autonomic nervous system in provoking the electrocardiographic abnormalities in 22 patients with subarachnoid hemorrhage. The standard electrocardiographic tracings and one-channel computer-based electrocardiographic tracings for spectral analysis of heart rate variability were made. Blood samples for plasma norepinephrine concentrations were taken. Statistically significant parasympathetic hyperactivation between Days 4 and 6 after sudden onset of the disease was found. In standard electrocardiographic tracings in almost all patients transient repolarisation changes and in one patient transient premature ventricular complexes were observed. Plasma norepinephrine concentrations did not parallel electrocardiographic abnormalities. No statistically significant correlation was found among tests of autonomic nervous system activity. Electrocardiographic abnormalities in our group of patients were transient, functional and observed only in the acute phase. They were probably not dependent on elevated plasma norepinephrine concentration. Spectral analysis of heart rate variability failed to explain the role of the autonomic nervous system in provoking the cardiac abnormalities. PMID:8891057

Svigelj, V; Grad, A; Kiauta, T

1996-08-01

425

Lisinopril indifferently improves heart rate variability during day and night periods in spontaneously hypertensive rats.  

PubMed

The aim of this work was to investigate the effect of 10 weeks of lisinopril treatment to spontaneously hypertensive rats (SHRs) on day/night variations of blood pressure, heart rate and autonomic cardio-regulation parameters. Male SHR with surgically implanted radio-telemetry implant that provided direct measurements of arterial pressure and electrocardiogram wave were used. Animals were allocated to two groups (n=5 each). The first group was treated with lisinopril (20 mg/kg by gavage) daily for 10 weeks (treated group); whereas the second was gavaged daily with tap water (untreated group). Arterial blood pressure, ECG and other telemetry parameters were recorded at the start and at the end of 10-week treatment. Collected data were analyzed using specialized software and were statistically tested. In addition to the expected lowering of blood pressure, spectral analysis of R-R intervals revealed that lisinopril treatment for 10 weeks significantly caused 2-3 fold increase in heart rate variability (HRV) during both active and inactive periods. However, R-R interval durations demonstrated variable distribution patterns during those periods. The cause of observed distribution pattern of R-R intervals during active and inactive periods may be of significance to better understand HRV changes and warrants further investigations. PMID:23489185

Albarwani, S; Al-Siyabi, S; Tanira, M O

2013-03-14

426

Performance analysis of low rate wireless technologies for medical applications  

Microsoft Academic Search

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

Nada Golmie; David Cypher; Olivier Rébala

2005-01-01

427

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

PubMed Central

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

Kuo, Chih-Horng; Ochman, Howard

2009-01-01

428

Application of polypyrrole actuators: feasibility of variable camber foils  

Microsoft Academic Search

A decade of research into electroactive polymer actuators is leading to the exploration of applications. These technologies are not ready to compete with the internal combustion engine and electric motors in high power propulsion systems but are suitable for intermittent or aperiodic applications with moderate cycle life requirements, providing an alternative to solenoids and direct drive electric motors. Polypyrrole, an

John D. W. Madden; Bryan Schmid; Martin Hechinger; Serge R. Lafontaine; Peter G. A. Madden; Franz S. Hover; Richard Kimball; Ian W. Hunter

2004-01-01

429

Effect of cold or thermoneutral water immersion on post-exercise heart rate recovery and heart rate variability indices.  

PubMed

This study aimed to investigate the effect of cold and thermoneutral water immersion on post-exercise parasympathetic reactivation, inferred from heart rate (HR) recovery (HRR) and HR variability (HRV) indices. Twelve men performed, on three separate occasions, an intermittent exercise bout (all-out 30-s Wingate test, 5 min seated recovery, followed by 5 min of submaximal running exercise), randomly followed by 5 min of passive (seated) recovery under either cold (CWI), thermoneutral water immersion (TWI) or control (CON) conditions. HRR indices (e.g., heart beats recovered in the first minute after exercise cessation, HRR(60)(s)) and vagal-related HRV indices (i.e., natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals (Ln rMSSD)) were calculated for the three recovery conditions. HRR(60)(s) was faster in water immersion compared with CON conditions [30+/-9 beats min(-)(1) for CON vs. 43+/- 10 beats min(-)(1) for TWI (P=0.003) and 40+/-13 beats min(-)(1) for CWI (P=0.017)], while no difference was found between CWI and TWI (P=0.763). Ln rMSSD was higher in CWI (2.32+/-0.67 ms) compared with CON (1.98+/-0.74 ms, P=0.05) and TWI (2.01+/-0.61 ms, P=0.08; aES=1.07) conditions, with no difference between CON and TWI (P=0.964). Water immersion is a simple and efficient means of immediately triggering post-exercise parasympathetic activity, with colder immersion temperatures likely to be more effective at increasing parasympathetic activity. PMID:20403733

Al Haddad, Hani; Laursen, Paul B; Chollet, Didier; Lemaitre, Frédéric; Ahmaidi, Saïd; Buchheit, Martin

2010-04-18

430

Heart rate variability reflects training load and psychophysiological status in young elite gymnasts.  

PubMed

Sartor, F, Vailati, E, Valsecchi, V, Vailati, F, La Torre, A. Heart rate variability reflects training load and psychophysiological status in young elite gymnasts. J Strength Cond Res 27(10): 2782-2790, 2013-In gymnastics, monitoring of the training load and assessment of the psychophysiological status of elite athletes is important for training planning and to avoid overtraining, consequently reducing the risk of injures. The aim of this study was to examine whether heart rate variability (HRV) is a valuable tool to determine training load and psychophysiological status in young elite gymnasts. Six young male elite gymnasts took part in a 10-week observational study. During this period, beat-to-beat heart rate intervals were measured every training day in weeks 1, 3, 5, 7, and 9. Balance, agility, upper limb maximal strength, lower limb explosive, and elastic power were monitored during weeks 2, 4, 6, 8, and 10. Training load of each training session of all 10 weeks was assessed by session rating of perceived exertion (RPE) and psychophysiological status by Foster's index. Morning supine HRV (HF% and LF%/HF%) correlated with the training load of the previous day (r = 0.232, r = -0.279, p < 0.05 ). Morning supine to sitting HRV difference (mean R wave to R wave interval (RR), mean heart rate, HF%, SD1) correlated with session RPE of the previous day (r = -0.320, r = 0.301, p < 0.01; r = 0.265, r = -0.270, p < 0.05) but not with Foster's index. Training day/reference day HRV difference (mean RR, SD1) showed the best correlations with session RPE of the previous day (r = -0.384, r = -0.332, p < 0.01) and Foster's index (r = -0.227, r = -0.260, p < 0.05). In conclusion, HRV, and in particular training day/reference day mean RR difference or SD1 difference, could be useful in monitoring training load and psychophysiological status in young male elite gymnasts. PMID:23364293

Sartor, Francesco; Vailati, Emanuele; Valsecchi, Viola; Vailati, Fulvio; La Torre, Antonio

2013-10-01

431

Dynamic evolution of plant mitochondrial genomes: Mobile genes and introns and highly variable mutation rates  

PubMed Central

We summarize our recent studies showing that angiosperm mitochondrial (mt) genomes have experienced remarkably high rates of gene loss and concomitant transfer to the nucleus and of intron acquisition by horizontal transfer. Moreover, we find substantial lineage-specific variation in rates of these structural mutations and also point mutations. These findings mostly arise from a Southern blot survey of gene and intron distribution in 281 diverse angiosperms. These blots reveal numerous losses of mt ribosomal protein genes but, with one exception, only rare loss of respiratory genes. Some lineages of angiosperms have kept all of their mt ribosomal protein genes whereas others have lost most of them. These many losses appear to reflect remarkably high (and variable) rates of functional transfer of mt ribosomal protein genes to the nucleus in angiosperms. The recent transfer of cox2 to the nucleus in legumes provides both an example of interorganellar gene transfer in action and a starting point for discussion of the roles of mechanistic and selective forces in determining the distribution of genetic labor between organellar and nuclear genomes. Plant mt genomes also acquire sequences by horizontal transfer. A striking example of this is a homing group I intron in the mt cox1 gene. This extraordinarily invasive mobile element has probably been acquired over 1,000 times separately during angiosperm evolution via a recent wave of cross-species horizontal transfers. Finally, whereas all previously examined angiosperm mtDNAs have low rates of synonymous substitutions, mtDNAs of two distantly related angiosperms have highly accelerated substitution rates.

Palmer, Jeffrey D.; Adams, Keith L.; Cho, Yangrae; Parkinson, Christopher L.; Qiu, Yin-Long; Song, Keming

2000-01-01

432

Single-grain cosmogenic 21Ne concentrations in fluvial sediments reveal spatially variable erosion rates  

NASA Astrophysics Data System (ADS)

We evaluated the hypothesis that the spatial variation in erosionin a catchment is reflected in the distribution of the cosmogenicnuclide concentrations in sediments leaving the catchment. Usingpublished data and four new 10Be measurements in fluvial sedimentcollected from the outlets of small river catchments, we constrainedthe spatial variability of erosion rates in the Gaub River catchmentin Namibia. We combined these catchment-averaged erosion rates,and the mean slope values with which they are associated, ina digital elevation model (DEM)-based analysis to predictdistributions of cosmogenic 21Ne concentrations in the sedimentleaving the Gaub catchment. We compared these synthetic distributionswith the distribution of concentrations of cosmogenic 21Ne (21NeC)in 32 quartz fluvial pebbles (16-21 mm) collected fromthe catchment outlet. The 21NeC concentrations span nearly twoorders of magnitude (2.6-160 x 106 atoms/g) and are highlyskewed toward low values. The DEM-based analysis confirms thisskew—the measured 21NeC distribution plots within theenvelope of distributions predicted for the catchment. Thismatch between measured and synthetic 21Ne distributions impliesthat the measured distribution is a signature of the spatialvariation in erosion rates.

Codilean, Alexandru T.; Bishop, Paul; Stuart, Finlay M.; Hoey, Trevor B.; Fabel, Derek; Freeman, Stewart P. H. T.

2008-02-01

433

Exponentially enhanced quantum communication rate by multiplexing continuous-variable teleportation  

NASA Astrophysics Data System (ADS)

A major challenge of today's quantum communication systems lies in the transmission of quantum information with high rates over long distances in the presence of unavoidable losses. Thereby the achievable quantum communication rate is fundamentally limited by the amount of energy that can be transmitted per use of the channel. It is hence vital to develop quantum communication protocols that encode quantum information as energy efficiently as possible. To this aim we investigate continuous-variable quantum teleportation as a method of distributing quantum information. We explore the possibility to encode information on multiple optical modes and derive upper and lower bounds on the achievable quantum channel capacities. This analysis enables us to benchmark single-mode versus multi-mode entanglement resources. Our research reveals that multiplexing does not only feature an enhanced energy efficiency, leading to an exponential increase in the achievable quantum communication rates in comparison to single-mode coding, but also yields an improved loss resilience. However, as reliable quantum information transfer is only achieved for entanglement values above a certain threshold a careful optimization of the number of coding modes is needed to obtain the optimal quantum channel capacity.

Christ, Andreas; Lupo, Cosmo; Silberhorn, Christine

2012-08-01

434

Nonlinear dynamics analysis of heart rate variability signals to detect sleep disordered breathing in children.  

PubMed

This paper reports a preliminary investigation to evaluate the significance of various nonlinear dynamics approaches to analyze the heart rate variability (HRV) signal in children with sleep disordered breathing (SDB). Data collected from children in the age group of 1-17 years diagnosed with sleep apnea were used in this study. Both short term (5 minutes) and long term data from a full night polysomnography (7-9 hours) were analyzed. For short term data, the presence of nonstationarity in the derived HRV signal was determined by calculating the local Hurst exponent. Poincare plots and approximate entropy (ApEn) were then used to show the presence of correlation in the data. For long term data, the derived HRV signal was first separated into corresponding sleep stages with the aid of the recorded sleep hypnogram values at 30 seconds epochs. The scaling exponents using detrended fluctuation analysis (DFA) and the ApEn were then calculated for each sleep stage. Data from two sample subjects recorded for different sleep stages and breathing patterns were considered for short term analysis. Data from 7 sample subjects (after sleep staging) were considered for long term analysis. The accuracy rate of ApEn was about 72% for both long term and short term data sets. The accuracy rate of Alpha (alpha) derived from DFA for long term correlations was 57%. Further work is necessary to improve on the accuracies of these useful nonlinear dynamic measures and determine their sensitivity and specificity to detect SDB in children. PMID:17946587

Nazeran, H; Krishnam, R; Chatlapalli, S; Pamula, Y; Haltiwanger, E; Cabrera, S

2006-01-01

435

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

PubMed

This study examined the effect of exercise mode on geometrical, and time and frequency domain measures of heart rate variability (HRV) during steady-state, moderate intensity exercise of the same HR. Seventeen healthy, active male participants volunteered for this study and completed a treadmill VO2max determination. One week later, cardiorespiratory, perceptual and HRV measures were recorded during seated rest (15 min) and consecutive bouts (15 min) of steady-state exercise at 50 and 65% of maximal HR. Exercise was performed using either upper body (arm ergometer), lower body (cycle) or whole body (treadmill) modes. Separated by 1 week and in a random order, participants undertook the same procedures with the remaining exercise modes. Cardiorespiratory, perceptual and HRV responses were determined during rest and steady-state exercise and analysed by two-way (mode vs. stage) repeated measures ANOVA and post hoc pairwise comparisons. Apart from a reduced respiratory rate during lower body exercise, whole and lower body exercise resulted in similar cardiorespiratory, perceptual and HRV responses. Compared to whole or lower body exercise, upper body exercise resulted in significantly (P < 0.05) greater measures of HRV particularly those within the very low (0-0.04 Hz) and low (0.04-0.15 Hz) frequency bands, greater rating of perceived exertion and less oxygen consumption. Upper body, moderate intensity exercise resulted in greater HRV compared to whole or lower body exercise with further studies necessary to elucidate the mechanisms and clinical implications for this greater HRV. PMID:17922138

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

2007-10-06

436

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.

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

2009-01-01

437

iHeartLift: a closed loop system with bio-feedback that uses music tempo variability to improve heart rate variability.  

PubMed

"Musica delenit bestiam feram" translates into "Music soothes the savage beast". There is a hidden truth in this ancient quip passed down from generations. Besides soothing the heart, it also incites the heart to a healthier level of heart rate variability (HRV). In this paper, an approach to use and test music and biofeedback to increase the heart rate variability for people facing daily stress is discussed. By determining the music tempo variability (MTV) of a piece of music and current heart rate variability, iHeartLift is able to compare the 2 trends and locate a musical piece that is suited to increase the user's heart rate variability to a healthier level. With biofeedback, the 2 trends are continuously compared in real-time and the musical piece is changed in accordance with the current comparisons. A study was conducted and it was generally found that HRV can be uplifted by music regardless of language and meaning of musical lyrics but with limitations to musical genre. PMID:22254526

Ho, Thomas C T; Chen, Xiang

2011-01-01

438

Heart Rate Variability Analysis of Ischemic and Heart Rate Related ST-segment Deviation Episodes Based on Time-frequency Method  

Microsoft Academic Search

ST-segment deviation is the routine method for the diagnosis of coronary heart diseases. However, other phenomena, such as heart rate changes and a posture change can cause similar manifestations in the ST segment, lowing the sensitivity and specificity of the detection. In this study, a different method, based on time-frequency analysis of heart rate variability, was proposed to evaluate the

Wang Xing; Xu Liang; Sun Zhongwei; Yang Zibin; Peng Yi

2007-01-01

439

Effects of high-latitude ionospheric electric field variability on global thermospheric Joule heating and mechanical energy transfer rate  

Microsoft Academic Search

Effects of high-latitude ionospheric electric field variability on the Joule heating and mechanical energy transfer rate are investigated by incorporating realistic spatial and temporal characteristics of electric field variability derived from observations into the forcing of a thermosphere ionosphere electrodynamic general circulation model. First, the characteristics of subgrid-scale variability are examined from a spectral analysis of Dynamic Explorer-2 (DE-2) plasma

Tomoko Matsuo

2008-01-01

440

Fruit, vegetable, and fish consumption and heart rate variability: the Veterans Administration Normative Aging Study123  

PubMed Central

Background: Higher intakes of fruit, vegetables, and dark fish may prevent sudden cardiac death and arrhythmias, but the exact mechanisms are not fully understood. Objective: We examined whether high consumption of fruit, vegetables, and dark fish would be associated with beneficial changes in heart rate variability (HRV). Design: HRV variables were measured among 586 older men with 928 total observations from November 2000 to June 2007 in the Normative Aging Study, a community-based longitudinal study of aging. Dietary intake was evaluated with a self-administered semiquantitative food-frequency questionnaire and categorized into quartiles. Results: After controlling for potential confounders, intake of green leafy vegetables was positively associated with normalized high-frequency power and inversely associated with normalized low-frequency power (P for trend < 0.05). These significant associations were retained after further adjustment for healthy lifestyle factors, such as physical activity and use of multivitamins. No significant association was seen between HRV measures and intakes of other fruit and vegetables, vitamin C, carotenoids, tuna and dark-meat fish, or n–3 (omega-3) fatty acids. An effect modification of intake of noncitrus fruit by obesity and of total vegetables and cruciferous vegetables by cigarette smoking was seen, which warrants further investigation. Conclusion: These findings suggest that higher intake of green leafy vegetables may reduce the risk of cardiovascular disease through favorable changes in cardiac autonomic function.

Tucker, Katherine L; O'Neill, Marie S; Sparrow, David; Vokonas, Pantel S; Hu, Howard; Schwartz, Joel

2009-01-01

441

Metabolic energy correlates of heart rate variability spectral power associated with a 900-calorie challenge.  

PubMed

We studied healthy males challenged with a 900 Cal test beverage and correlated EE with the raw (ms(2)) and normalized units (nu) of total power (TP), low frequency/high frequency (LF/HF) and VLF spectral power of heart rate variability (HRV). The correlations were evaluated during 20?min of normal breathing (NB, control) and 20?min of paced breathing (PB) at 12 breaths·min(-1) (0.2?Hz). EE was not significantly correlated with any of the HRV variables before the metabolic challenge. After the challenge, EE was positively correlated with LF/HF and with VLF; VLF was also positively correlated with LF/HF during both NB and PB. These findings suggest that EE may be a correlate of LF/HF and of VLF spectral power of HRV in healthy adolescent/young adult males. The association of lower resting energy expenditure with lower amounts of VLF spectral power may occur in individuals with predilections for obese phenotypes. PMID:21773025

Millis, Richard M; Austin, Rachel E; Hatcher, Mark D; Bond, Vernon; Goring, Kim L

2011-06-20

442

Variability in the GCR Count Rate as Measured by the CRaTER Instrument on LRO  

NASA Astrophysics Data System (ADS)

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) is currently orbiting the Moon onboard NASA's Lunar Reconnaissance Orbiter (LRO). CRaTER is composed of a stack of 3 pairs of axially-aligned solid-state Silicon detectors which surround 2 sections of Tissue Equivalent Plastic. Particles that have enough energy to penetrate the outer skin of the instrument (about 10 MeV for protons) are measured at each detector pair as they traverse the length of the instrument. The particle population that produces a signal in CRaTER normally consists of both solar energetic particles and Galactic Cosmic Rays (GCR). Due to the low level of solar activity during the mission thus far, CRaTER's measurements consist almost entirely of GCR. In this paper we investigate spatial variabilities in the count rate during the first few months of the mission that could be due to lunar phase, lunar latitude/longitude, eclipses and look direction. Possible sources of temporal variability will also be investigated.

Case, A. W.; Spence, H. E.; Golightly, M. J.; Kasper, J. C.; Blake, J. B.; Mazur, J. E.; Townsend, L. W.

2009-12-01

443

Intra-day and inter-day reliability of heart rate variability measurement.  

PubMed

At present, analysis of heart rate variability (HRV) is becoming widely used as a clinical or research tool. Supported reliability studies for HRV measurement are, however, still limited. The main purpose was to perform an assessment of the absolute and relative reliability of HRV parameters from short-term recordings by means of orthoclinostatic stimulation and to investigate, whether there is a difference in repeating the retest immediately or after several days. The study group consisted of 99 participants (mean age 22 ± 1.24 years). Standard HRV indexes were computed: PT (total spectral power), PHF (high frequency spectral power), PLF (low frequency spectral power) and LF/HF. Absolute reliability was assessed by the standard error of measurement and 95% limits of agreement; relative reliability was assessed by the intraclass correlation coefficient. There was also an estimate of the sample size needed to detect the mean difference ? 30% of the between-subject standard deviation. In conclusion, a large random variation (within individuals) of HRV parameters was revealed, regardless of whether the retest was repeated immediately or with an interruption. For most HRV parameters (particularly in the immediately repeated test-retest), however, random variation represents a limited portion of the between-subject variability. PMID:22963409

Cipryan, Lukas; Litschmannova, Martina

2012-09-11

444

Lactate and Heart Rate Variability Threshold during Resistance Exercise in the Young and Elderly.  

PubMed

This purpose of this study was to: 1) determine the intensity corresponding to anaerobic threshold (AT) during a discontinuous resistance exercise protocol in healthy young and elderly subjects by analyzing heart rate variability (HRV) and blood lactate (BL) and 2) investigate the effect of aging on these variables. A total of 28 individuals, 14 young and 14 elderly healthy men underwent one-repetition maximum (1RM) testing to determine maximum load on the leg press. Discontinuous resistance exercise testing was initiated at 10% of the 1RM with subsequent increases of 10%. The load corresponding to AT was approximately 30% 1RM in both groups. The determination of AT by HRV was associated with BL responses (p<0.01). While HRV indexes decreased with increasing of loads in both groups, the elderly had lower values at loads below AT (p<0.05). Additionally, BL increased sharply after the load corresponding to AT in both groups, although elderly subjects showed the lowest values (p<0.05). In conclusion, HRV is an effective tool for determining AT, which was approximately 30% 1RM under the testing procedures included in the present study. Furthermore, there was a marked change in autonomic function, with gradual vagal withdrawal followed by sympathetic activation. These responses were lower in elderly subjects. PMID:23606341

Simões, R P; Castello-Simões, V; Mendes, R G; Archiza, B; Santos, D A; Machado, H G; Bonjorno Jr, J C; Oliveira, C R; Reis, M S; Catai, A M; Arena, R; Borghi-Silva, A

2013-04-19

445

Analysis of heart rate variability signal during meditation using deterministic-chaotic quantifiers.  

PubMed

Abstract This study investigated the level of chaos and the existence of fractal patterns in the heart rate variability (HRV) signal prior to meditation and during meditation using two quantifiers adapted from non-linear dynamics and deterministic chaos theory: (1) component central tendency measures (CCTMs) and (2) Higuchi fractal dimension (HFD). CCTM quantifies degree of variability/chaos in the specified quadrant of the second-order difference plot for HRV time series, while HFD quantifies dimensional complexity of the HRV series. Both the quantifiers yielded excellent results in discriminating the different psychophysiological states. The study found (1) significantly higher first quadrant CCTM values and (2) significantly lower HFD values during meditation state compared to pre-meditation state. Both of these can be attributed to the respiratory-modulated oscillations shifting to the lower frequency region by parasympathetic tone during meditation. It is thought that these quantifiers are most promising in providing new insight into the evolution of complexity of underlying dynamics in different physiological states. PMID:24044586

Kamath, Chandrakar

2013-10-01

446

Accumulation Rate Variability along Norway-US Traverse Route, East Antarctica  

NASA Astrophysics Data System (ADS)

A ~2000 km-long transect of 400 MHz ground-penetrating radar (GPR) data was collected during the 2008-2009 Norway-US scientific traverse between South Pole and Troll Station on the Indian Ocean side of East Antarctica. The GPR profiles extend into the firn-ice transition. Density contrasts give rise to many highly reflective stratigraphic horizons in the firn, which can be traced continuously for several hundreds of kilometers, both near the surface and at depth. Here, the structure of these reflecting horizons is used to examine the depositional environment of the ice sheet. We also assign ages to the GPR horizons using intersecting ice cores, which allow us to quantify spatial and temporal variability in snow accumulation rates in a little known portion of East Antarctica.

Hall, M. L.; Hamilton, G. S.; Arcone, S. A.

2009-12-01

447

Heart Rate Variability and Respiratory Sinus Arrhythmia Assessment of Affective States by Bivariate Autoregressive Spectral Analysis  

PubMed Central

The study of emotions elicited by human-computer interactions is a promising field that could lead to the identification of specific patterns of affective states. We present a heart rate variability (HRV) assessment of the autonomic nervous system (ANS) response and respiratory sinus arrhythmia during PC-mediated stimuli by means of standard and multivariate autoregressive spectral methods. 35 healthy volunteers were exposed to computer-mediated tasks during data collection. The stimuli were designed to elicit: relaxation (R), engagement (E) and stress (S); half of the subjects were exposed to E before S (RES) while the other to S before E (RSE). HRV measures clearly separate the ANS response among R, S and E. Less significant differences are found between E and S in RSE, suggesting that S stimuli may cause a lasting response affecting the E period. Results from the bivariate analysis indicate a disruption of the cardio-respiratory coupling during non-relax conditions.

Magagnin, V; Mauri, M; Cipresso, P; Mainardi, L; Brown, EN; Cerutti, S; Villamira, M; Barbieri, R

2010-01-01

448

Cardiac Sympathetic Activity Assessed by Heart Rate Variability Indicates Myocardial Ischemia on Cold Exposure in Diabetes  

PubMed Central

Measurement of heart rate variability (HRV) is a non-invasive technique that can be used to investigate functioning of the autonomic nervous system, especially the balance between sympathetic and vagal activities. It is reported that dilatation of coronary microcirculation by augmentation of sympathetic nerve activity (SNA) caused by cold exposure was impaired in diabetes. The question of whether or not SNA in HRV could respond to coronary ischemia was evaluated by cold exposure in diabetic rats. It was found that diabetes with weight loss significantly increased SNA both in baseline and cold exposure, compared with control. A correspondence was also found with coronary ischemia. It can be concluded that measurement of HRV may provide useful information regarding the coronary risk of cold exposure in diabetes. (*English translation of J Jpn Coll Angiol 2012; 52: 295-301)

2013-01-01

449

Modified nondestructive colorimetric method to evaluate the variability of oxygen diffusion rate through wine bottle closures.  

PubMed

Some modifications to a previous nondestructive colorimetric method that permits evaluation of the oxygen diffusion rate through wine closures were proposed. The method is based on the reaction of indigo carmine solution with oxygen and the tristimulus measurement of the consequent color change. Simplified preparation and measurement procedures were set up, allowing the analysis of a large number of samples simultaneously. The method was applied to the evaluation of the variability within the lot of 20 different types of stoppers (synthetic, produced by molding, and natural cork). The closures were tested at a storage temperature of 26 degrees C. With regard to oxygen permeability, the natural cork stopper showed a low homogeneity within the lot, especially during the first month after bottling, whereas the synthetic closure showed a greater steadiness in the performance. The limits of the colorimetric method were also analyzed, and three possible causes of degradation of the indigo carmine solution were identified: oxygen, light, and heat. PMID:20187636

Brotto, Laura; Battistutta, Franco; Tat, Lara; Comuzzo, Piergiorgio; Zironi, Roberto

2010-03-24

450

Complexity of heart rate variability in type 2 diabetes - effect of hyperglycemia.  

PubMed

Heart rate variability (HRV) is reduced in diabetes mellitus (DM) patients, suggesting dysfunction of cardiac autonomic regulation which has been associated with increased risk for pathological cardiac events. In this paper, we examined changes in HRV complexity in association to blood glucose level (BGL) and duration of diabetes. Resting HRV and BGL measurements of 32 healthy controls and 54 type 2 DM (T2DM) patients were analyzed. HRV complexity was assessed using Shannon entropy, sample entropy (SampEn), multiscale entropy (MSE), and multiscale Renyi entropy. HRV complexity increased with hyperglycemia indicated by increases in Shannon entropy and MSE and decreases in Renyi entropy for negative orders. Diabetes duration was strongly associated with Renyi entropy which increased for positive orders and decreased for negative orders as a function of disease duration. Shannon entropy, SampEn and MSE did not correlate with disease duration. PMID:24110996

Tarvainen, Mika P; Cornforth, David J; Kuoppa, Pekka; Lipponen, Jukka A; Jelinek, Herbert F

2013-07-01

451

Real-time heart rate variability extraction using the Kaiser window.  

PubMed

A new method for real-time heart rate variability (HRV) detection from the R-wave signal, based on the integral pulse frequency modulation (IPFM) model and its similarity to pulse position modulation, is presented. The proposed method exerts low-pass filtering with a Kaiser window. It can also be used for off-line HRV analysis in both the time and frequency domains. Real-time bandpass filtering as a new HRV investigation method and as a by-product of the proposed algorithm is also introduced. Furthermore, the discrete time domain version of the French-Holden algorithm is developed, and it is thoroughly proved that low-pass filtering is an ideal method for detection of HRV. PMID:9311168

Seydnejad, S R; Kitney, R I

1997-10-01

452

A comparison of two Hilbert spectral analyses of heart rate variability.  

PubMed

The present paper compares the performance of two Hilbert spe