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1

Verification of a variable rate sprayer for nursery liner applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

2

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...

3

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...

4

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

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

PubMed

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

Sammito, S; Böckelmann, I

2015-03-01

7

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

E-print Network

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

Jones, Carol

8

Performance evaluation of a newly developed variable rate sprayer for nursery liner applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

9

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...

10

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...

11

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 µl/min is obtained given a channel width of 1000 µm and a rotational velocity of 8 rpm. In addition, it is shown that the pump is capable of developing a maximum pressure head of 75 mm water (0.66 kPa) with channel width of 500 µm.

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

2012-04-01

12

A variable rate speech compressor for mobile applications  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

13

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

14

Long-Term Variable Rate Lime and Phosphorus Application for Piedmont No-Till Field Crops  

Microsoft Academic Search

Variable rate (VR) fertilizer application is a paradigm with potential to improve input efficiency and farm profitability. It is widely marketed by commercial applicators in the southeastern US. However, field studies comparing VR with traditional management have not demonstrated consistent, positive results. The objectives of this study were: (1) to determine the soil impact, crop response and economic potential of

Randy Weisz; Ron Heiniger; Jeffrey G. White; Ben Knox; Lonnie Reed

2003-01-01

15

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

NASA Astrophysics Data System (ADS)

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

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

2005-01-01

16

Development of a Semi-controller for a Variable Rate Fertilizer Applicator  

NASA Astrophysics Data System (ADS)

In this paper, aiming at the current development of domestic agricultural production, introduced a variable fertilizer controller which suits for a domestic food-producing areas to promote output. The variable rate fertilization controller combined with the current Chinese made fertilizer equipment; mechanism of metering system for the applicator uses a flute wheel. The amount of fertilizer is determined by the rotation speed of flute wheel. The use of the control system can be inconsistent in soil fertility, pre-division of plots with different fertilizer way through the process of moving the driver automatically adjusts the amount of fertilizer direction buttons to precision variable fertilization. Papers on the electronic structure of the controller and software design in detail. In addition, we have examined the performance of this new product in the field by using different fertilizer and requirement. The results reveal that semi-automatic controller work well by controlling the quantity of fertilizer precisely. Specifically, coefficient of variation of fertilizing is controlled to be less than 5%. That means this new type semi-automatic controller worth developing in further.

Ji, Jianbin; Wang, Xiu; Mao, Yijin; Chen, Liping; Hu, Lingyan

17

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

E-print Network

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

Arzeno, Natalia M. (Natalia María Arzeno Soltero)

2007-01-01

18

Admission Interview Ratings: Relationship to Applicant Academic and Demographic Variables and Interviewer Characteristics.  

ERIC Educational Resources Information Center

Medical school admission interview ratings for four entering classes (n=356 students) were compared with preadmission academic variables (admission test scores, undergraduate grades), student characteristics (age, gender, residence), and interviewer characteristics (gender, professional background, admission committee membership). Recommendations…

Elam, Carol L.; Andrykowski, Michael A.

1991-01-01

19

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

E-print Network

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

Beck, Andy Dwayne

2001-01-01

20

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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 georegistratio...

21

Change rates and prevalence of a dichotomous variable: simulations and applications.  

PubMed

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

Brinks, Ralph; Landwehr, Sandra

2015-01-01

22

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

PubMed Central

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

Brinks, Ralph; Landwehr, Sandra

2015-01-01

23

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

24

ADOPTION OF SPATIAL INFORMATION GATHERING TECHNOLOGIES AND VARIABLE RATE INPUT APPLICATION TECHNOLOGIES BY COTTON FARMERS IN THE SOUTHEAST  

Microsoft Academic Search

Probit analysis identified factors influencing adoption of precision farming technologies by Southeastern cotton farmers. Younger, more educated farmers who operated larger farms and were optimistic about the future of precision farming were most likely to adopt site-specific information technology. The probability of adopting variable rate input application technology was higher for younger farmers who operated larger farms, owned more of

Steven W. Martin; Roland K. Roberts; Burton C. English; James A. Larson; Rebecca L. Cochran; W. Robert Goodman; Sherry L. Larkin; Michele C. Marra; W. Donald Shurley; Jeanne M. Reeves

2004-01-01

25

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...

26

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...

27

Determinants of heart rate variability  

Microsoft Academic Search

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

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

1996-01-01

28

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

E-print Network

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

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

2002-05-21

29

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

PubMed

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

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

2013-04-01

30

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

31

[Effects of nitrogen application rate on spatiotemporal variability of biomass accumulation of cotton's fruiting branch at flower and boll stage].  

PubMed

Field experiments were conducted in Anyang and Nanjing, the typical representatives of ecological regions in the Yellow River Valley and the lower reaches of Yangtze River Valley in China, to quantitatively analyze the spatiotemporal variability of biomass accumulation of the fruiting branch of cotton variety Nucotn 33B at its flower and boll stage under effects of 0, 120, 240, 360, and 480 kg N x hm(-2) (marked as N0, N1, N2, N3, and N4, respectively). The results indicated that both in Nanjing and in Anyang, the temporal variability of biomass accumulation of vegetative and reproductive organs at different positions of fruiting branch could be described by Logistic equation, but the spatial variability was obviously different. Under the nitrogen application rate of 360 kg x hm(-2) in Anyang and of 240 kg x hm(-2) in Nanjing, the biomass accumulation had the characteristics of earlier starting date, shorter duration, and maximal speed of rapid increase. These nitrogen application rates could accelerate the biomass accumulation to benefit the high lint yield and fiber quality, while excess or deficient nitrogen supply was disadvantageous to the biomass accumulation of fruiting branch. Therefore, it could be possible to apply appropriate amount of nitrogen to regulate the growth eigenvalues of different positions fruiting branch at its speed growth stage to obtain high lint yield and fiber quality. PMID:19123358

Yang, Zhi-Bin; Chen, Bing-Lin; Zhou, Zhi-Guo

2008-10-01

32

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

33

An experimental variable-rate sprayer for nursery and orchard applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

Most chemical applications in orchards and ornamental nurseries are not target-oriented, resulting in significant loss of pesticides and contamination of the environment. To avoid over- and under-application of chemicals, sprayers must be designed to apply the appropriate amount of pesticide based o...

34

Effect of variable rates of gypsum application on wheat yield under rice-wheat system.  

PubMed

A field experiment was initiated during 2005-2006 to study the effect of gypsum application on rice and subsequent wheat crop. The direct, residual and cumulative effects of gypsum were also noticed under rice-wheat system. The gypsum was applied as 0, 1 and 2 t ha(-1) with the basal dose of N, P2O5, K2O as 120, 90 and 60 kg ha(-1) to both crops. Rice variety IRRI6 and wheat variety Naseer 2000 were planted in Randomized Complete Block Design with three replications in a permanent layout. The soil samples were collected from both crops before earing to study P and K concentrations. The rice yield was significantly affected by gypsum application that ranged from 4807-5472 kg ha(-1). The highest rice yield was recorded by the application of 2.0 t gypsum ha(-1) with an increase of 13.8% over control. Similarly all the yield components like number of panicles m(-2), panicle length, plant height and 1000 grain weight were also significantly affected by gypsum application. The wheat grain yield ranged from 2598 to 4304 kg ha(-1). The cumulative application of 1 and 2 t gypsum ha(-1) increased the wheat yield by 25.25 and 65.66% over check, respectively. The direct and residual application of 2 t gypsum ha(-1) gave an increase of 46.80 and 15.05% over the check, respectively. The application of gypsum significantly affected the P and K that ranged from 4.50-7.50 and 4.70-9.32 mg kg(-1) P while 70-110 and 78-112 mg kg(-1) K in rice and wheat, respectively. PMID:19090243

Khan, Rahmat Ullah; Gurmani, Ali Raza; Khan, Muhammad Sohail; Gurmani, Akber Hussain

2007-11-01

35

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

36

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

E-print Network

. -!!. !)[-E. (? 9!!! !(! ~ ))! (40) For tD 100, Eq. 40 can he expressed in terms of the 1ogarithnd. c approximation. This result is given ss Ap 162. 6 E (q. -q . )(log(t-t ) + log kh j j j ? 1 j-1 ~ 2 t w ? 5. 228 + 0. 8686s) (41) For application to field...100, Eq. 14 reduces to (15) where 7 is Euler's constant aud has a value of 0. 577216. Ex]nessing Eq. 15 in field units gives np - pi ? pwf 162. 6 ~[log t + 1~ 2 ? 3. 228 t w + 0. 8686s] (16) Expressing Fq. 16 iu terms of the flowing hottomhole...

Blasingame, Thomas Alwin

1986-01-01

37

Flow variability of an aerial variable-rate nozzle at constant pressures  

Technology Transfer Automated Retrieval System (TEKTRAN)

Variable-rate ground application systems have been in use for the past 15 years, but due to high application speeds, flow requirements, and aerodynamic considerations, variable-rate aerial nozzles have not been available until now. In 2006, Spray Target, Inc. released the VeriRatevariable-rate aer...

38

Analysis of Heart Rate Variability  

Microsoft Academic Search

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

B. Mc A. SAYKRS

1973-01-01

39

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

40

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 ...

41

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

42

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

PubMed

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

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

2014-11-01

43

Multifractality and heart rate variability  

NASA Astrophysics Data System (ADS)

In this paper, we participate to the discussion set forth by the editor of Chaos for the controversy, "Is the normal heart rate chaotic?" Our objective was to debate the question, "Is there some more appropriate term to characterize the heart rate variability (HRV) fluctuations?" We focused on the ?24 h RR series prepared for this topic and tried to verify with two different techniques, generalized structure functions and wavelet transform modulus maxima, if they might be described as being multifractal. For normal and congestive heart failure subjects, the hq exponents showed to be decreasing for increasing q with both methods, as it should be for multifractal signals. We then built 40 surrogate series to further verify such hypothesis. For most of the series (?75%-80% of cases) multifractality stood the test of the surrogate data employed. On the other hand, series coming from patients in atrial fibrillation showed a small, if any, degree of multifractality. The population analyzed is too small for definite conclusions, but the study supports the use of multifractal series to model HRV. Also it suggests that the regulatory action of autonomous nervous system might play a role in the observed multifractality.

Sassi, Roberto; Signorini, Maria Gabriella; Cerutti, Sergio

2009-06-01

44

An Analysis of Heart Rate Variability  

Microsoft Academic Search

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

H. LUCZAK; W. LAURIG

1973-01-01

45

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

46

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

47

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

PubMed

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

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

2014-07-01

48

Performance evaluation of a center pivot variable rate irrigation system  

Technology Transfer Automated Retrieval System (TEKTRAN)

Variable Rate Irrigation (VRI) for center pivots offers potential to match specific application rates to non-uniform soil conditions along the length of the lateral. The benefit of such systems is influenced by the areal extent of these variations and the smallest scale to which the irrigation syste...

49

Association between oral variables and heart rate variability  

PubMed Central

The heart rate variability is a useful method to assess cardiac autonomic modulation in patients undergoing dental procedures, because knowledge of physiological conditions provides greater security to the professional as well as the possibility of a better plan treatment to patient benefit. The aim of our study was to describe the association between cardiac autonomic control and dental variables. We consulted the databases Medline, SciELO, Lilacs and Cochrane, using the terms “autonomic”, “dentistry”, “heart rate variability”, “cardiovascular physiology.” The selected studies indicated a strong relationship between dental variables and HRV. There was an association between malocclusion, TMD, dental procedures cirugia and low HRV. Thus, they become more studies that relate to HRV in dental science, especially in clinical practice. PMID:24373329

2013-01-01

50

Variable-rate variable-power MQAM for fading channels  

Microsoft Academic Search

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

Andrea J. Goldsmith; Soon-Ghee Chua

1997-01-01

51

Heart rate variability characterization using correlation dimension  

Microsoft Academic Search

Heart rate variability (HRV) has become a useful tool for analyzing cardiovascular autonomic control from the electrocardiogram (ECG). Detection and analysis of HRV allows a quantitative and noninvasive method to obtain reliable and reproducible information on autonomic modulation of heart rate. Nonlinear methods (e.g., correlation dimension) are promising tools for HRV assessment. This paper presents a reliable estimation of correlation

Xiaobo Miao; Wei He; Hao Yang; Heng-Ming Tail

2002-01-01

52

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

E-print Network

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

Haykin, Simon

53

Heart rate variability in ischemic heart disease  

Microsoft Academic Search

Major untoward events, such as life-threatening arrhythmias and acute coronary events, have been suggested to be triggered by the activation of the autonomic nervous system in patients with coronary artery disease. Analysis of heart rate variability by conventional time and frequency domain methods, as well as by newer methods derived from nonlinear system theory, has offered a novel approach for

Heikki V. Huikuri; Timo H. Mäkikallio

2001-01-01

54

Heart rate variability in isolated rabbit hearts  

Microsoft Academic Search

Clinical evidence for the presence of heart rate variability (HRV) in patients with cardiac denervation after heart transplantation raised our interest in HRV in an isolated heart preparation. Therefore hearts of seven adult white ELCO rabbits were transferred to a perfusion apparatus. After a stabilization of 30 min in the Langendorff mode, the hearts were perfused in the working heart

G. Heger; B. Frey; B. Kiegler; T. Kos; G. Steurer

1995-01-01

55

Heart Rate Variability Malvin Carl Teich  

E-print Network

, Grasmere, UK, 2005 #12;CONGESTIVE HEART FAILURE INABILITY OF HEART TO INCREASE CARDIAC OUTPUT IN PROPORTION #12;wav SMALLER VALUES OF wav THAN FOR NORMAL SUBJECTS HEART-FAILURE M. C. Teich, Workshop on NewHeart Rate Variability Malvin Carl Teich Boston University and Columbia University http

Teich, Malvin C.

56

Heart Rate Variability in Chinchilla Rabbits  

Microsoft Academic Search

Temporal and spectral parameters of heart rate variability were studied as criteria for classification of mature Chinchilla rabbit population according to their basal neurovegetative status. The absolute values of total spectral power density and individual frequency bands differed significantly in vagotonics and sympathotonics. However, standardized spectral power distributions in high-, low- and very low-frequency ranges were similar in both groups.

K. Sh. Nadareishvili; I. I. Meskhishvili; D. D. Kakhiani; G. L. Ormotsadze; G. T. Nazarishvili; M. G. Gvasalia; M. T. Khvedelidze; V. Ya. Sandodze

2002-01-01

57

HEART RATE VARIABILITY AND 24-HOUR MINIMUM HEART RATE  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

58

Variable Rate Phosphorus Fertilization in Cotton on the Texas High Plains  

E-print Network

with the ground rig used for blanket-rate applications, after it was fitted with an Agchem/Soil Tec., Inc-distance method of interpolation to calculate and generate its variable-rate application maps (Figure 1, Lamesa

Mukhtar, Saqib

59

Gaussian Mixture Model of Heart Rate Variability  

PubMed Central

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

Costa, Tommaso; Boccignone, Giuseppe; Ferraro, Mario

2012-01-01

60

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

61

Heart rate variability in hypertensive subjects  

Microsoft Academic Search

Hypertension is often associated with findings of sympathetic hyperactivity. Evidence shows that adrenergic receptor stimulation can induce left ventricular hypertrophy. Using an autoregressive algorithm in a power spectrum analysis of heart-rate variability in 14 subjects with mild hypertension (mean age 41 ± 9.0 years) and 9 age-matched normotensives we compared autonomic nervous system function at baseline (rest) and during sympathetic

Gianfranco Piccirillo; Maria Rita Munizzi; Filippo L. Fimognari; Vincenzo Marigliano

1996-01-01

62

Quantitative analysis of heart rate variability  

Microsoft Academic Search

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

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

1995-01-01

63

Modeling heart rate variability by stochastic feedback  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

64

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

65

Heart Rate Variability – A Historical Perspective  

PubMed Central

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

Billman, George E.

2011-01-01

66

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

2003-01-01

67

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

68

DEVELOPMENT OF A SEMI-CONTROLLER FOR A VARIABLE RATE FERTILIZER  

E-print Network

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

69

Soil variability in engineering applications  

NASA Astrophysics Data System (ADS)

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

Vessia, Giovanna

2014-05-01

70

A variable rate coefficient chlorine decay model.  

PubMed

Chlorine is the most widely used water disinfectant in the world. As a result, optimal chlorine usage is essential for both human and environmental health. Chlorine decay models can be used to predict residual concentrations in water distribution networks and optimize chlorine dosing. However, the coefficients of current chlorine decay models are often dependent on the loading conditions and are therefore impractical for day-to-day water distribution network modeling purposes and chlorine dosing optimization studies. This study proposes and assesses a novel numerical chlorine decay model with four parameters that are independent of the loading conditions for a given water sample. The model is based on kinetic equations derived from the rate law for concurrent bimolecular second order reactions with chlorine and will be referred to as the variable rate coefficient (VRC) chlorine decay model. The performance of the proposed model is compared with another model reported in the literature, and the VRC model is also assessed for reliability with data sets that are omitted during model calibration. The VRC model is consistently found to be in agreement with the experimental data. PMID:19238972

Jonkergouw, Philip M R; Khu, Soon-Thiam; Savic, Dragan A; Zhong, Dan; Hou, Xiu Q; Zhao, Hong-Bin

2009-01-15

71

Altitude, heart rate variability and aerobic capacities.  

PubMed

We analyzed the relationship between aerobic capacities and changes in heart rate variability (HRV) in Nordic-skiers during living high-training low (Hi-Lo). Eleven skiers trained for 18 days at 1200 m, sleeping at 1200 m (LL, n = 5) or in hypoxic rooms (HL, n = 6, 3 x 6 days at altitudes of 2500 - 3000 - 3500 m, 11 h . day (-1)). Measurements were performed before, during and two weeks after Hi-Lo. VO(2max), peak power output were not improved in HL nor in LL, whereas VO(2) and power at the respiratory compensation point (VO(2RCP) and PRCP) increased by 7.5 % and 5.0 % only in HL. Significant changes in HRV occurred only in LL, in the standing position, including a 30 % (p < 0.05) increase in resting heart rate (HR), a 50 % (p < 0.05) decrease in total spectral power (TP) and a 77 % (p < 0.05) decrease in high frequency activity (HF). When all the subjects were pooled, the changes in HRV in the supine position were correlated to the changes in aerobic capacities, i.e., HF, LF and TP were correlated to VO(2RCP) and HR, HF and TP were correlated to PRCP. This study confirms the relationship between HRV and changes in aerobic capacity, therefore highlighting the potential value of HRV for monitoring altitude training adaptations. PMID:17687758

Schmitt, L; Fouillot, J-P; Millet, G P; Robach, P; Nicolet, G; Brugniaux, J; Richalet, J-P

2008-04-01

72

MATLAB SOFTWARE FOR DETRENDED FLUCTUATION ANALYSIS OF HEART RATE VARIABILITY  

E-print Network

- dividuals with congestive heart failure. The HRV computational tools mentioned above do not imple- mentMATLAB SOFTWARE FOR DETRENDED FLUCTUATION ANALYSIS OF HEART RATE VARIABILITY Fernanda S. Leite1, Heart rate variability, HRV. Abstract: The analysis of heart rate variability (HRV) is an important tool

Carvalho, João Luiz

73

The Impact of Soil Sampling Errors on Variable Rate Fertilization  

SciTech Connect

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

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

2004-07-01

74

gHRV: Heart rate variability analysis made easy.  

PubMed

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

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

2014-08-01

75

Relationship of QT interval variability to heart rate and RR interval variability.  

PubMed

The study investigated whether the beat-to-beat QT interval variability relationship to the mean heart rate and the RR interval variability depended on the cardiovascular autonomic status changed by postural positioning. Repeated long-term 12-lead Holter recordings were obtained from 352 healthy subjects (mean age 32.7 ± 9.1 years, 176 females) while they underwent postural provocative tests involving supine, unsupported sitting and unsupported standing positions. Each recording was processed as a sequence of overlapping 10-second segments. In each segment, the mean RR interval, the coefficients of variance of the RR intervals (RRCV) and the QT intervals (QTCV) were obtained. In each subject, these characteristics, corresponding to different postural positions, were firstly averaged and secondly used to obtain within-subject correlation coefficients between the different characteristics at different postural positions. While the within-subject means of RRCV generally decreased when changing the position from supine to sitting and to standing (4.53 ± 1.95%, 4.12 ± 1.51% and 3.26 ± 1.56% in females and 3.99 ± 1.44%, 4.00 ± 1.24% and 3.53 ± 1.32% in males respectively), the means of QTCV systematically increased during these position changes (0.96 ± 0.40%, 1.30 ± 0.56% and 1.88 ± 1.46% in females and 0.85 ± 0.30%, 1.13 ± 0.41% and 1.41 ± 0.59% in males, respectively). The intra-subject relationship between QTCV, RRCV and mean RR intervals was highly dependent on postural positions. The study concludes that no universally applicable normalization of the QT interval variability for the heart rate and/or the RR interval variability should be assumed. In future studies of the QT variability, it seems preferable to report on the absolute values of QT variability, RR variability and mean heart rate separately. PMID:23938108

Hnatkova, Katerina; Kowalski, Donna; Keirns, James J; van Gelderen, E Marcel; Malik, Marek

2013-01-01

76

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

77

Development of digital flow control system for multi-channel variable-rate sprayers  

Technology Transfer Automated Retrieval System (TEKTRAN)

Precision modulation of nozzle flow rates is a critical step for variable-rate spray applications in orchards and ornamental nurseries. An automatic flow rate control system activated with microprocessors and pulse width modulation (PWM) controlled solenoid valves was developed to control flow rates...

78

Pulse rate variability compared with Heart Rate Variability in children with and without sleep disordered breathing.  

PubMed

Heart Rate Variability (HRV), the variation of time intervals between heartbeats, is one of the most promising and widely used quantitative markers of autonomic activity. Traditionally, HRV is measured as the series of instantaneous cycle intervals obtained from the electrocardiogram (ECG). In this study, we investigated the estimation of variation in heart rate from a photoplethysmography (PPG) signal, called pulse rate variability (PRV), and assessed its accuracy as an estimate of HRV in children with and without sleep disordered breathing (SDB). We recorded raw PPGs from 72 children using the Phone Oximeter, an oximeter connected to a mobile phone. Full polysomnography including ECG was simultaneously recorded for each subject. We used correlation and Bland-Altman analysis for comparing the parameters of HRV and PRV between two groups of children. Significant correlation (r > 0.90, p < 0.05) and close agreement were found between HRV and PRV for mean intervals, standard deviation of intervals (SDNN) and the root-mean square of the difference of successive intervals (RMSSD). However Bland-Altman analysis showed a large divergence for LF/HF ratio parameter. In addition, children with SDB had depressed SDNN and RMSSD and elevated LF/HF in comparison to children without SDB. In conclusion, PRV provides the accurate estimate of HRV in time domain analysis but does not reflect precise estimation for parameters in frequency domain. PMID:24111246

Dehkordi, Parastoo; Garde, Ainara; Karlen, Walter; Wensley, David; Ansermino, J Mark; Dumont, Guy A

2013-01-01

79

Comparison of heart rate variability and pulse rate variability detected with photoplethysmography  

NASA Astrophysics Data System (ADS)

This study compares ear photoplethysmography (PPG) and electrocardiogram (ECG) in providing accurate heart beat intervals for use in calculations of heart rate variability (HRV, from ECG) or of pulse rate variability (PRV, from PPG) respectively. Simultaneous measurements were taken from 44 healthy subjects at rest during spontaneous breathing and during forced metronomic breathing (6/min). Under both conditions, highly significant (p > 0.001) correlations (1.0 > r > 0.97) were found between all evaluated common HRV and PRV parameters. However, under both conditions the PRV parameters were higher than HRV. In addition, we calculated the limits of agreement according to Bland and Altman between both techniques and found good agreement (< 10% difference) for heart rate and standard deviation of normal-to-normal intervals (SDNN), but only moderate (10-20%) or even insufficient (> 20%) agreement for other standard HRV and PRV parameters. Thus, PRV data seem to be acceptable for screening purposes but, at least at this state of knowledge, not for medical decision making. However, further studies are needed before more certain determination can be made.

Rauh, Robert; Limley, Robert; Bauer, Rainer-Dieter; Radespiel-Troger, Martin; Mueck-Weymann, Michael

2004-08-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

81

Classification and regression tree (CART) for analysis of soybean yield variability among fields in Northeast China: The importance of phosphorus application rates under drought conditions  

Microsoft Academic Search

Drought is the most critical environmental factor limiting the productivity of agricultural crops worldwide. Increased frequency and severity of drought are expected to accompany climate change and will negatively impact global food security. Wide yield variability from field to field, and consequently reduced average yield on a regional scale often occur under drought conditions. The reasons for the yield variability

Haifeng Zheng; Liding Chen; Xiaozeng Han; Xinfeng Zhao; Yan Ma

2009-01-01

82

Wearable depression monitoring system with heart-rate variability.  

PubMed

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

Roh, Taehwan; Sunjoo Hong; Hoi-Jun Yoo

2014-08-01

83

12 CFR 619.9340 - Variable interest rate.  

Code of Federal Regulations, 2013 CFR

...DEFINITIONS § 619.9340 Variable interest rate. An interest rate on the outstanding loan balances, which may be changed from time to time during the period of the loan, if provision is made in the note or loan...

2013-01-01

84

Heart rate variability in mice with coronary heart disease  

E-print Network

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

Zapanta, Laurence (Laurence F.)

2005-01-01

85

Sociocultural Variability in Infant Temperament Ratings.  

ERIC Educational Resources Information Center

Examines mother characteristics, child behavior, and mother's temperament ratings when their babies were 4 months old. The social status, anxiety level, and mental health status of the mother were all related to temperament ratings on the Carey Infant Temperament Questionnaire. Results suggest that individual differences in mothers may be the…

Sameroff, Arnold J.; And Others

1982-01-01

86

Estimating the Variability of Substitution Rates  

Microsoft Academic Search

Suppose that amino acid or nucleotide data are available for a homologous gene in several species which diverged from a common ancestor at about the same time and that substitution rates between all pairs of species are calculated, correcting as necessary for multiple substitutions and for back and parallel substitutions. The variances and covariances of these corrected substitution rates are

Michael Bulmer

1989-01-01

87

MULTIRESOLUTION WAVELET ANALYSIS OF HEART RATE VARIABILITY FOR  

E-print Network

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

Teich, Malvin C.

88

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

89

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...

90

[Music and heart rate variability. Study of the effect of music on heart rate variability in healthy adolescents].  

PubMed

The effect of trophotropic (relaxing) music on heart rate and heart rate variability has been investigated in 23 healthy young individuals by means of 24-hour Holter-ECG. Relaxing music (Bach, Vivaldi, Mozart) resulted in significant reduction of heart rate and also significant reduction of heart rate variability. The significance of these results for the use of music in coronary heart disease is discussed. PMID:10412282

Escher, J; Evéquoz, D

1999-05-20

91

Variable rate QAM for mobile radio  

Microsoft Academic Search

Quadrature amplitude modulation (QAM) schemes which vary the number of modulation levels in accordance with the mobile radio fading channel variations are investigated. Important parameters considered are the fading rate and the block size used. We describe how the adaptive QAM modems can be employed and consider their use in a DECT-like TDD packet structure. System performance in the presence

W. T. Webb; R. Steele

1995-01-01

92

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

ERIC Educational Resources Information Center

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

Barkaoui, Khaled

2010-01-01

93

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

2013-02-01

94

Heart Rate Variability Analysis Using Threshold of Wavelet Package Coefficients  

E-print Network

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

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

2009-01-01

95

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

96

Ground-Based Canopy Reflectance Sensing for Variable-Rate Nitrogen Corn Fertilization  

Technology Transfer Automated Retrieval System (TEKTRAN)

Nitrogen (N) available to support corn (Zea mays L.) production can be highly variable within fields. Canopy reflectance sensing for assessing crop N health has been proposed as a technology to base top-dress variable-rate N application. Objectives of this research were to evaluate the use of active...

97

Noncontact imaging photoplethysmography to effectively access pulse rate variability  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

98

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 PMID:10336928

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

1999-01-01

99

High-bit-rate continuous-variable quantum key distribution  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

100

Variable-rate coding for meteor-burst communications  

Microsoft Academic Search

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

M. B. Pursley; S. D. Sandberg

1989-01-01

101

Heart rate variability associated with particulate air pollution  

Microsoft Academic Search

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

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

1999-01-01

102

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

103

Artificial intelligent strategy to control heart rate variability  

Microsoft Academic Search

This research proposes a new artificial intelligence strategy to enhance software games based on heart rate variability. The model consists of two modules (visual learning and IQ test) that will conjoined with a biofeedback device connected to a computer to monitor student heart rate and record its changes in a stressful situation and generate appropriate reports. By playing these two

A. H. Beg; Noraziah Ahmad; Nawsher Khan; Ahmed N Abd Alla; Muhammad Nubli; A. K. Lovely

2010-01-01

104

Changes in resting heart rate variability across the menstrual cycle.  

PubMed

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

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

2014-10-01

105

Heart rate variability (HRV): an indicator of stress  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

106

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

PubMed

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

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

2015-03-01

107

Concentration dependence of variability in growth rates of microtubules.  

PubMed Central

Growth and shortening of microtubules in the course of their polymerization and depolymerization have previously been observed to occur at variable rates. To gain insight into the meaning of this prominent variability, we studied the way in which its magnitude depends on the growth rate of experimentally observed and computer-simulated microtubules. The dynamic properties of plus-ended microtubules nucleated by pieces of Chlamydomonas flagellar axonemes were observed in real time by video-enhanced differential interference contrast light microscopy at differing tubulin concentrations. By means of a Monte Carlo algorithm, populations of microtubules were simulated that had similar growth and dynamic properties to the experimentally observed microtubules. By comparison of the experimentally observed and computer-simulated populations of microtubules, we found that 1) individual microtubules displayed an intrinsic variability that did not change as the rate of growth for a population increased, and 2) the variability was approximately fivefold greater than predicted by a simple model of subunit addition and loss. The model used to simulate microtubule growth has no provision for incorporation of lattice defects of any type, nor sophisticated geometry of the growing end. Thus, these as well as uncontrolled experimental variables were eliminated as causes for the prominent variability. PMID:12324403

Pedigo, Susan; Williams, Robley C

2002-01-01

108

Heart rate variability interventions for concussion and rehabilitation  

PubMed Central

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

Conder, Robert L.; Conder, Alanna A.

2014-01-01

109

Heart rate variability interventions for concussion and rehabilitation.  

PubMed

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

Conder, Robert L; Conder, Alanna A

2014-01-01

110

Two-Stage Variable Sample-Rate Conversion System  

NASA Technical Reports Server (NTRS)

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

Tkacenko, Andre

2009-01-01

111

Do Financial Market Variables Predict Unemployment Rate Fluctuations?  

Microsoft Academic Search

This paper examines empirically the Granger-causal relationship between financial market variables and real economic activity as measured by the unemployment rate. We find in our paper that the in-sample measures of fit are largely affected by one particular influential observation: 1974:12. This observation accounts for superior performance of the paper-bill spread in explaining the unemployment rate. We then show that

Jingyi Chen

2002-01-01

112

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

113

Assessing variability by joint sampling of alignments and mutation rates  

E-print Network

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

Wakolbinger, Anton

114

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...

115

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...

116

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

E-print Network

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

Adams, Robert P.

117

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

118

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

119

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

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

Ordinal pattern statistics for the assessment of heart rate variability  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

122

Ultraviolet variability of quasars: dependence on the accretion rate  

NASA Astrophysics Data System (ADS)

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

Meusinger, H.; Weiss, V.

2013-12-01

123

Changes in heart rate variability and QT variability during the first trimester of pregnancy.  

PubMed

The risk of new-onset arrhythmia during pregnancy is high, presumably relating to changes in both haemodynamic and cardiac autonomic function. The ability to non-invasively assess an individual's risk of developing arrhythmia during pregnancy would therefore be clinically significant. We aimed to quantify electrocardiographic temporal characteristics during the first trimester of pregnancy and to compare these with non-pregnant controls.Ninety-nine pregnant women and sixty-three non-pregnant women underwent non-invasive cardiovascular and haemodynamic assessment during a protocol consisting of various physiological states (postural manoeurvres, light exercise and metronomic breathing). Variables measured included stroke volume, cardiac output, heart rate, heart rate variability, QT and QT variability and QTVI (a measure of the variability of QT relative to that of RR).Heart rate (p < 0.0005, p < 0.0005, p < 0.0005) and cardiac output (p = 0.043, p < 0.0005, p < 0.0005) were greater in pregnant women in all physiological states (respectively for the supine position, light exercise and metronomic breathing state), whilst stroke volume was lower in pregnancy only during the supine position (p < 0.0005). QTe (Q wave onset to T wave end) and QTa (T wave apex) were significantly shortened (p < 0.05) and QTeVI and QTaVI were increased in pregnancy in all physiological states (p < 0.0005). QT variability (p < 0.002) was greater in pregnant women during the supine position, whilst heart rate variability was reduced in pregnancy in all states (p < 0.0005).Early pregnancy is associated with substantial changes in heart rate variability, reflecting a reduction in parasympathetic tone and an increase in sympathetic activity. QTVI shifted to a less favourable value, reflecting a greater than normal amount of QT variability. QTVI appears to be a useful method for quantifying changes in QT variability relative to RR (or heart rate) variability, being sensitive not only to physiological state but also to gestational age. We support the use of non-invasive markers of cardiac electrical variability to evaluate the risk of arrhythmic events in pregnancy, and we recommend the use of multiple physiological states during the assessment protocol. PMID:25690105

Carpenter, R E; D'Silva, L A; Emery, S J; Uzun, O; Rassi, D; Lewis, M J

2015-03-01

124

Adoption of Site-Specific Information and Variable-Rate Technologies in Cotton Precision Farming  

Microsoft Academic Search

Probit analysis identified factors that influence the adoption of precision farming technologies by Southeastern cotton farmers. Younger, more educated farmer who operated larger farms and were optimistic about the future of precision farming were most likely to adopt site-specific information technology. The probability of adopting variable-rate input application technology was higher for younger farmers who operated larger farms, owned more

Roland K. Roberts; Burton C. English; James A. Larson; Rebecca L. Cochran; W. Robert Goodman; Sherry L. Larkin; Michele C. Marra; Steven W. Martin; W. Donald Shurley; Jeanne M. Reeves

2004-01-01

125

Spray deposition inside tree canopies from a newly developed variable-rate air assisted sprayer  

Technology Transfer Automated Retrieval System (TEKTRAN)

Conventional spray applications in orchards and ornamental nurseries are not target-oriented, resulting in significant waste of pesticides and contamination of the environment. To address this problem, a variable-rate air-assisted sprayer implementing laser scanning technology was developed to apply...

126

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

127

Variable Rate Fertilizer Distributor in Precision Farming Based on PLC Technology  

Microsoft Academic Search

In order to improve the fertilization rationality of crop and decrease pollution and waste, the variable rate fertilizer applicator integrated optical sensors was designed based on PLC technology. NDVI (Normalized Difference Vegetative Index) value was a scale to measure the status health and the stand or fall of the crop. According to the real-time data from the NDVI equipment, combined

Limin Shao; Xiu Wang

2007-01-01

128

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

129

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

ERIC Educational Resources Information Center

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

Stamps, Leighton E.; Porges, Stephen W.

1975-01-01

130

Large-scale dimension densities for heart rate variability analysis  

NASA Astrophysics Data System (ADS)

In this work, we reanalyze the heart rate variability (HRV) data from the 2002 Computers in Cardiology (CiC) Challenge using the concept of large-scale dimension densities and additionally apply this technique to data of healthy persons and of patients with cardiac diseases. The large-scale dimension density (LASDID) is estimated from the time series using a normalized Grassberger-Procaccia algorithm, which leads to a suitable correction of systematic errors produced by boundary effects in the rather large scales of a system. This way, it is possible to analyze rather short, nonstationary, and unfiltered data, such as HRV. Moreover, this method allows us to analyze short parts of the data and to look for differences between day and night. The circadian changes in the dimension density enable us to distinguish almost completely between real data and computer-generated data from the CiC 2002 challenge using only one parameter. In the second part we analyzed the data of 15 patients with atrial fibrillation (AF), 15 patients with congestive heart failure (CHF), 15 elderly healthy subjects (EH), as well as 18 young and healthy persons (YH). With our method we are able to separate completely the AF (?ls?=0.97±0.02) group from the others and, especially during daytime, the CHF patients show significant differences from the young and elderly healthy volunteers (CHF, 0.65±0.13 ; EH, 0.54±0.05 ; YH, 0.57±0.05 ; p<0.05 for both comparisons). Moreover, for the CHF patients we find no circadian changes in ?ls? (day, 0.65±0.13 ; night, 0.66±0.12 ; n.s.) in contrast to healthy controls (day, 0.54±0.05 ; night, 0.61±0.05 ; p=0.002 ). Correlation analysis showed no statistical significant relation between standard HRV and circadian LASDID, demonstrating a possibly independent application of our method for clinical risk stratification.

Raab, Corinna; Wessel, Niels; Schirdewan, Alexander; Kurths, Jürgen

2006-04-01

131

Heart rate variability in normal and pathological sleep  

PubMed Central

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

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

2013-01-01

132

Influence of sickness condition on diurnal rhythms of heart rate and heart rate variability in cows  

PubMed Central

Parameters of heart rate variability would explain changes in heart rate during the disease status in cows and to evaluate whether such changes might provide a more sensitive and quantitative indicator of these conditions than crude indices. For this purpose, we recorded electrocardiograms for 24 hr using a Holter-type electrocardiograph and applied power spectral analysis of heart rate variability in both five clinically healthy and four hospitalized cows. The significant findings of the current investigation were that the diurnal variations of autonomic nervous function are abolished in cows that are sick. This abnormal rhythm was induced by predominant parasympathetic inhibition in these cows. Therefore, the heart rate variability may be a useful indicator of sickness condition in cows. PMID:25648088

YOSHIDA, Masumi; ONDA, Ken; WADA, Yasunori; KUWAHARA, Masayoshi

2014-01-01

133

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

134

Heart Rate Variability Dynamics for the Prognosis of Cardiovascular Risk  

Microsoft Academic Search

Statistical, spectral, multi-resolution and non-linear methods were applied to heart rate variability (HRV) series linked with classification schemes for the prognosis of cardiovascular risk. A total of 90 HRV records were analyzed: 45 from healthy subjects and 45 from cardiovascular risk patients. A total of 52 features from all the analysis methods were evaluated using standard two-sample Kolmogorov-Smirnov test (KS-test).

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

2011-01-01

135

Urinary albumin excretion and heart rate variability in obese women  

Microsoft Academic Search

OBJECTIVE: The aim of this work was to examine the relationship between cardiac autonomic function and urinary albumin excretion in obesity.SUBJECTS: These were 27 obese non-diabetic postmenopausal women and 18 non-obese healthy postmenopausal women.MEASUREMENTS: Urinary albumin excretion as well as plasma nitrate, both indices of capillary function, were measured. Power spectral analysis of heart rate variability was performed, as a

B Andersson; J Wikstrand; T Ljung; S Björk; Å Wennmalm; P Björntorp; Björn Andersson

1998-01-01

136

Heart rate variability in exercising humans: effect of water immersion  

Microsoft Academic Search

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

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

1998-01-01

137

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

138

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

E-print Network

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

139

Heart Rate Variability During Early Adaptation to Space  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

140

Compact solid state high repetition rate variable amplitude pulse generator  

Microsoft Academic Search

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

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

2009-01-01

141

Circadian Variation of Heart Rate Variability Across Sleep Stages  

PubMed Central

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

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

2013-01-01

142

General anesthesia suppresses normal heart rate variability in humans  

NASA Astrophysics Data System (ADS)

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

Matchett, Gerald; Wood, Philip

2014-06-01

143

Variable Sample Rate Conversion Techniques for the Advanced Receiver  

NASA Astrophysics Data System (ADS)

One of the primary challenges in the development of the Advanced Receiver is the ability to accommodate a wide variety of possible data rates, motivated by the desire to support different missions for the Deep Space Network (DSN) under different adverse conditions. To conform to fixed architectures such as the analog-to-digital converter (ADC) used at the front end and tracking loops used subsequently, this requires that the sampling rate be varied entirely digitally after the ADC to accommodate the fixed parameters of the tracking loops. In this article, we present a series of methods to achieve variable sample rate conversion (SRC). Specifically, we focus on two sets of schemes to alter the sampling rate: coarse techniques to lower the bulk of the sampling rate near the desired amount while removing out-of-band artifacts due to noise and interference, and fine techniques used to accurately tailor the sampling rate to the exact desired value. Advantages and disadvantages of both sets of methods are investigated in terms of implementation complexities and performance metrics.

Tkacenko, A.

2007-02-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

145

Effects of passive smoking on heart rate variability, heart rate and blood pressure: an observational studyx  

Microsoft Academic Search

Background Exposure to environmental tobacco smoke (ETS) has been shown to increase the risk for cardiovascular diseases and death, and autonomic dysfunction (specifically, reduced heart rate variability (HRV)) is a predictor of increased cardiac risk. This study tests the hypothesis that ETS exposure reduces HRV in the general population and discusses possible pathways. Methods This cross-sectional study was conducted between

Denise Felber Dietrich; Joel Schwartz; Christian Schindler; Jean-Michel Gaspoz; Jean-Claude Barthelemy; Jean-Marie Tschopp; Frederic Roche; Arnold von Eckardstein; Otto Brandli; Philippe Leuenberger; Diane R Gold; Ursula Ackermann-Liebrich

146

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

PubMed Central

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

Lehrer, Paul M.; Gevirtz, Richard

2014-01-01

147

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

ERIC Educational Resources Information Center

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

Tanno, Takayuki; Sakagami, Takayuki

2008-01-01

148

How to avoid misinterpretation of heart rate variability power spectra?  

PubMed

Spectral analysis of R-R Interval time series is increasingly used to determine periodic components of heart rate variability (HRV). Particular diagnostic relevance is assigned to a low-frequency (LF) component, associated with blood pressure regulation, and a high-frequency (HF) component, also referred to as respiratory sinus arrhythmia (RSA) in the HRV power spectra. Frequency ranges for parametrisation of power spectra have been defined for either component in numerous publications.Results obtained from examinations with standardised psychic load in which ECG and respiratory signal are continuously recorded and adequately processed have shown that the true individual frequency range of the HF component can be reliably determined only by means of characteristics of respiration (respiratory rate (RR), range and median value of RR, tidal depth). Respiratory rhythms are interindividually extremely differentiated and of individual-specific nature. In many cases LF and HF components may be totally superimposed on each other and, consequently, cannot be diagnostically evaluated. PMID:11886699

Cammann, Henning; Michel, Josef

2002-04-01

149

An age extended progress variable for conditioning reaction rates  

NASA Astrophysics Data System (ADS)

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 consumption layer. Above this threshold, the APV has a constant source term. To test the proposal, three-dimensional fully compressible direct numerical simulation (DNS) is performed in an inflow-outflow configuration with inlet turbulence forcing using a modified version of the DNS code SENGA. A model chemical mechanism involving two steps and four species is used which has an order of magnitude difference between the time scales associated with the two steps. The inlet Taylor scale Reynolds number is 51 and the Damköhler numbers are 2.0 and 0.29 for the two steps. When conditionally averaged on the proposed APV the scalar fluctuations about the conditional average are negligible. Further, it is shown that the probability density function of the APV can be reasonably approximated based on the first two moments of the APV and the fuel mass fraction. The APV probability density function (PDF) is approximated on rectangular slabs of cells normal to the flow direction using only these moments as a test case. Convolution of the PDF so approximated with conditional mean reaction rates—calculated from conditionally averaged scalar fields where the averaging was carried out over the entire domain—leads to an approximation for the unconditional mean reaction rates on each of these slabs typically within 10% of the true value for both steps. That the correlation between the reaction rates and the APV is strong, and that the PDF can be approximated for a situation where approximating the PDF for a product based progress variable is nontrivial, makes the proposed APV a strong alternative to traditional progress variables for both flamelet models and premixed conditional moment closure (CMC) approaches.

Grout, R. W.

2007-10-01

150

Influence of semen collection on salivary cortisol release, heart rate, and heart rate variability in stallions.  

PubMed

The aim of this study was to evaluate the stress response of stallions (n = 16) aged 3-13 years with previous sexual experience to semen collection by determination of heart rate, heart rate variability, and cortisol in saliva. Recordings were done on two consecutive days. The time intervals from leaving the box until arrival in the collection barn and from first exposure to the teaser mare until ejaculation as well as the number of mounts until ejaculation were neither affected by collection day nor by age, sexual experience (i.e., the number of breeding seasons the stallion experienced), or sexual workload of the stallion (i.e., the mean number of semen collections per week). Heart rate was continuously determined from 30 minutes before to 30 minutes after ejaculation and significantly increased in response to the semen collection procedure (P < 0.001). Changes in heart rate were significantly influenced by sexual experience (P < 0.01) and sexual workload (P < 0.05) but not by the age of the stallions. Day of semen collection did not have any effects. The heart rate variability variable root mean square of successive RR differences was not affected by semen collection procedures. Cortisol concentration in saliva was determined from 60 minutes before to 120 minutes after ejaculation and did not change significantly. The results indicate that semen collection is perceived as not more than a modest temporary stressor in sexually experienced and well-trained stallions. PMID:23664794

Pasing, Stephanie; von Lewinski, Mareike; Wulf, Manuela; Erber, Regina; Aurich, Christine

2013-08-01

151

Heart Rate Variability in Sleep-Related Migraine without Aura  

PubMed Central

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

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

2013-01-01

152

Heart rate variability in children with type 1 diabetes mellitus  

PubMed Central

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

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

2014-01-01

153

Heart rate variability biofeedback improves cardiorespiratory resting function during sleep.  

PubMed

The present study was designed to examine the effect of heart rate variability (HRV) biofeedback on the cardiorespiratory resting function during sleep in daily life. Forty-five healthy young adults were randomly assigned to one of three groups: HRV biofeedback, Autogenic Training(AT), and no-treatment control. Participants in the HRV biofeedback were instructed to use a handheld HRV biofeedback device before their habitual bedtime, those in the AT were asked to listen to an audiotaped instruction before bedtime,and those in the control were asked to engage in their habitual activity before bedtime. Pulse wave signal during sleep at their own residences was measured continuously with a wrist watch-type transdermal photoelectric sensor for three time points. Baseline data were collected on the first night of measurements, followed by two successive nights for HRV biofeedback, AT, or control. Cardiorespiratory resting function was assessed quantitatively as the amplitude of high frequency(HF) component of pulse rate variability, a surrogate measure of respiratory sinus arrhythmia. HF component increased during sleep in the HRV biofeedback group,although it remained unchanged in the AT and control groups. These results suggest that HRV biofeedback before sleep may improve cardiorespiratory resting function during sleep. PMID:23959190

Sakakibara, Masahito; Hayano, Junichiro; Oikawa, Leo O; Katsamanis, Maria; Lehrer, Paul

2013-12-01

154

Improvements in heart rate variability with exercise therapy  

PubMed Central

Heart rate variability (HRV) is a noninvasive, practical and reproducible measure of autonomic nervous system function. A heart rate that is variable and responsive to demands is believed to bestow a survival advantage, whereas reduced HRV may be associated with poorer cardiovascular health and outcomes. In recent years, many researchers have investigated the prognostic implications of HRV in a variety of clinical populations. Evidence suggests that reduced HRV has prognostic significance for individuals with myocardial infarction, chronic heart failure, unstable angina and diabetes mellitus. Interventions to increase HRV, such as exercise therapy, have also been examined. The findings of the present review suggest that exercise therapy may improve HRV in myocardial infarction, chronic heart failure and revascularization patients by increasing vagal tone and decreasing sympathetic activity. One hypothesis is that a shift toward greater vagal modulation may positively affect the prognosis of these individuals. While the underlying mechanisms by which exercise training improves vagal modulation are speculative at present, angiotensin II and nitric oxide may be potential mediators. PMID:20548976

Routledge, Faye S; Campbell, Tavis S; McFetridge-Durdle, Judith A; Bacon, Simon L

2010-01-01

155

Abnormal heart rate variability and atrial fibrillation after aortic surgery  

PubMed Central

Introduction Complete denervation of transplanted heart exerts protective effect against postoperative atrial fibrillation; various degrees of autonomic denervation appear also after transection of ascending aorta during surgery for aortic aneurysm. Objective This study aimed to evaluate if the level of cardiac denervation obtained by resection of ascending aorta could exert any effect on postoperative atrial fibrillation incidence. Methods We retrospectively analysed the clinical records of 67 patients submitted to graft replacement of ascending aorta (group A) and 132 with aortic valve replacement (group B); all episodes of postoperative atrial fibrillation occurred during the 1-month follow-up have been reported. Heart Rate Variability parameters were obtained from a 24-h Holter recording; clinical, echocardiographic and treatment data were also evaluated. Results Overall, 45% of patients (group A 43%, group B 46%) presented at least one episode of postoperative atrial fibrillation. Older age (but not gender, abnormal glucose tolerance, ejection fraction, left atrial diameter) was correlated with incidence of postoperative atrial fibrillation. Only among a subgroup of patients with aortic transection and signs of greater autonomic derangement (heart rate variability parameters below the median and mean heart rate over the 75th percentile), possibly indicating more profound autonomic denervation, a lower incidence of postoperative atrial fibrillation was observed (22% vs. 54%). Conclusion Transection of ascending aorta for repair of an aortic aneurysm did not confer any significant protective effect from postoperative atrial fibrillation in comparison to patients with intact ascending aorta. It could be speculated that a limited and heterogeneous cardiac denervation was produced by the intervention, creating an eletrophysiological substrate for the high incidence of postoperative atrial fibrillation observed. PMID:25859868

Compostella, Leonida; Russo, Nicola; D’Onofrio, Augusto; Setzu, Tiziana; Compostella, Caterina; Bottio, Tomaso; Gerosa, Gino; Bellotto, Fabio

2015-01-01

156

A CHEMICAL EXPLANATION OF THE VARIABILITY OF THE GROWTH RATE.  

PubMed

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. PMID:19872643

Rahn, O

1932-01-20

157

Heart rate variability during head down tilt and lower body negative pressure in the Russian Tschibis.  

PubMed

The cardiovascular function in space seems to be normal. However, abnormalities of cardiovascular responses have been found during lower body negative pressure suction in space. The etiology of the cardiovascular deconditioning in space is still unknown. A previous study showed, that short periods of head down tilt (HDT-6 degrees) induce changes in the spectral pattern of heart rate variabilty (HRV) and an increase in the sympathethic activation caused by orthostatic stress. The aim of this study was to test following hypotheses: 1. The dynamic of heart rate variability is different in the head down tilt and supine positions. 2. The application of lower body negative pressure (LBNP) during head down tilt induces similar heart rate variability patterns like the standing position. 3. After short term head down tilt the cardiovascular response to lower body negative pressure stressor is altered. PMID:11538895

Diedrich, A; Drescher, J; Nalishitij, V; Spatenko, J A; Rome, J L; Grüber, W

1995-01-01

158

Heart Rate Variability in Bipolar Mania and Schizophrenia  

PubMed Central

Background Autonomic nervous system (ANS) dysfunction and reduced heart rate variability (HRV) have been reported in a wide variety of psychiatric disorders, but have not been well characterized in bipolar mania. We recorded cardiac activity and assessed HRV in acutely hospitalized manic bipolar (BD) and schizophrenia (SCZ) patients compared to age- and gender-matched healthy comparison (HC) subjects. Method HRV was assessed using time domain, frequency domain, and nonlinear analyses in 23 manic BD, 14 SCZ, and 23 HC subjects during a 5 minute rest period. Psychiatric symptoms were assessed by administration of the Brief Psychiatric Rating Scale (BPRS) and the Young Mania Rating Scale (YMRS). Results Manic BD patients demonstrated a significant reduction in HRV, parasympathetic activity, and cardiac entropy compared to HC subjects, while SCZ patients demonstrated a similar, but non-significant, trend towards lower HRV and entropy. Reduction in parasympathetic tone was significantly correlated with higher YMRS scores and the unusual thought content subscale on the BPRS. Decreased entropy was associated with increased aggression and diminished personal hygiene on the YMRS scale. Conclusion Cardiac function in manic BD individuals is characterized by decreased HRV, PMID:19700172

Henry, Brook L.; Minassian, Arpi; Paulus, Martin P.; Geyer, Mark A.; Perry, William

2009-01-01

159

The relationship between resting heart rate variability and heart rate recovery  

Microsoft Academic Search

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

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

2010-01-01

160

Colliding Interests – Age as an Automobile Insurance Rating Variable: Equitable RateMaking or Unfair Discrimination?  

Microsoft Academic Search

Many private business relationships are increasingly characterized by claims that certain actions should not be permitted\\u000a since particular right claims are involved. Such claims should be taken seriously, but are they always ethically legitimate?\\u000a This paper analyzes one context, the use of age as a rating variable in the pricing of automobile insurance, where such claims\\u000a are made. By identifying,

Robert L. Brown; Darren Charters; Sally Gunz; Neil Haddow

2007-01-01

161

Characterizing heart rate variability by scale-dependent Lyapunov exponent  

NASA Astrophysics Data System (ADS)

Previous studies on heart rate variability (HRV) using chaos theory, fractal scaling analysis, and many other methods, while fruitful in many aspects, have produced much confusion in the literature. Especially the issue of whether normal HRV is chaotic or stochastic remains highly controversial. Here, we employ a new multiscale complexity measure, the scale-dependent Lyapunov exponent (SDLE), to characterize HRV. SDLE has been shown to readily characterize major models of complex time series including deterministic chaos, noisy chaos, stochastic oscillations, random 1/f processes, random Levy processes, and complex time series with multiple scaling behaviors. Here we use SDLE to characterize the relative importance of nonlinear, chaotic, and stochastic dynamics in HRV of healthy, congestive heart failure, and atrial fibrillation subjects. We show that while HRV data of all these three types are mostly stochastic, the stochasticity is different among the three groups.

Hu, Jing; Gao, Jianbo; Tung, Wen-wen

2009-06-01

162

Climatic variability in upper ocean ventilation rates diagnosed using chlorofluorocarbons  

NASA Astrophysics Data System (ADS)

The chlorofluorocarbon CFC-12 (CCl2F2) distributions from two occupations of a meridional hydrographic section in the eastern North Atlantic are used to describe the oceanic penetration of CFCs and change in the integrated ventilation patterns over the five years from 1988 to 1993. The CFC-12 water-column inventories increased by 30-40%, despite a slowing atmospheric growth rate (14%), because of continuing uptake by undersaturated subsurface water masses whose response is lagged by the ventilation time-scales. After removing the long-term CFC temporal trend using a tracer age based normalization technique, we observe a distinct dipole pattern in upper ocean ventilation, with reduced convection in the subpolar gyre and enhanced production of saline subtropical underwater in 1993. These differences are discussed in relation to interannual variability in atmospheric surface forcing, upper ocean anomalies, and convection patterns associated with the North Atlantic Oscillation.

Doney, Scott C.; Bullister, John L.; Wanninkhof, Rik

163

Chronomics of heart rate variability on earth and in space.  

PubMed

Chronomes are time structures consisting of multifrequency rhythms, elements of chaos, and trends in chaotic and rhythmic endpoints. Chronomics maps the dynamics of organisms' broad interactions with the environment near and far, rather than merely the daily routines. We introduced the chronomics of heart rate variability (HRV), characterized by a broad time structure, that includes the prominent circadians and also ultradian (notably about 8h and about 12h) and infradian (notably about-weekly, about-yearly, and about 10-yearly) changes, in addition to undergoing trends with aging. Alterations in these HRV chronomes are known to predict the presence of disease in the near future. Thus, for the health and safety of astronauts, HRV chronomes should be assessed before, during and after the mission in the International Space Station to check for any alteration. Future work should focus on how phenomena in the cosmos, including helio- and geomagnetics, can affect physiological chronomes, those of the HRV in particular. PMID:19833301

Otsuka, K; Izumi, R; Ishioka, N; Ohshima, H; Mukai, C

2009-10-01

164

Acupuncture and heart rate variability: a systematic review.  

PubMed

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 available publications until October 2009 without language restrictions. We included randomized clinical trials (RCTs) comparing acupuncture and sham acupuncture. The risk of bias in each study was assessed using the Cochrane criteria. Twelve RCTs met all of the inclusion criteria. One RCT evaluated the effects of acupuncture in patients with minor depression or anxiety disorders and another RCT examined the effect of acupuncture on migraine patients. Another four RCTs tested the effects of acupuncture in healthy subjects who were exposed to several conditions, including mental stress, fatigue from driving, and caffeine intake. The remaining six RCTs assessed the effects of acupuncture on healthy subjects in a normal state without any stressors. Five RCTs found significant differences in HRV between patients treated with acupuncture versus those treated with sham acupuncture (controls). However, the majority of the other RCTs showed inconsistent results or did not identify significant differences in HRV spectral parameters among individuals treated with acupuncture as compared to those treated with sham acupuncture. In conclusion, sham-controlled RCTs showed variable results and no clear evidence that acupuncture has any specific effects on HRV. Therefore, more rigorous research appears to be warranted. PMID:20304708

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

2010-06-24

165

Heart rate variability related to effort at work.  

PubMed

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 and HRV information. Nineteen healthy hospital workers were studied during two work days during the same work period. Daytime, work time and night time heart rate, as well as physical activity were recorded. An effort-reward imbalance (ERI) questionnaire was used to assess chronic work stress. The emotions of stress, irritation and satisfaction were assessed six times during both days. Seventeen subjects had an ERI ratio over 1, indicating imbalance between effort and reward, that is, chronic work stress. Of the daily emotions, satisfaction was the predominant emotion. The daytime relaxation percentage was higher on Day 2 than on Day 1 (4 ± 6% vs. 2 ± 3%, p < 0.05) and the night time relaxation (43 ± 30%) was significantly higher than daytime or work time relaxation on the both Days. Chronic work stress correlated with the vagal activity index of HRV. However, effort at work had many HRV correlates: the higher the work effort the lower daytime HRV and relaxation time. Emotions at work were also correlated with work time (stress and satisfaction) and night time (irritation) HRV. These results indicate that daily emotions at work and chronic work stress, especially effort, is associated with cardiac autonomic function. Neural network modelling of individual heart rate and HRV information may provide additional information in stress research in field conditions. PMID:21356531

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

2011-11-01

166

Heart rate recovery after exercise is related to the insulin resistance syndrome and heart rate variability in elderly men  

Microsoft Academic Search

Objective We investigated the associations between heart rate recovery after exercise (as a suggested measure of vagal activity), heart rate variability, and measurements of the insulin resistance syndrome. Material and Methods Seventy men aged 70 years were examined with a symptom-limited bicycle exercise test, a 24-hour heart rate variability test, and different measurements of different components of the insulin resistance

Lars Lind; Bertil Andrén

2002-01-01

167

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

168

Associations between the cortisol awakening response and heart rate variability.  

PubMed

The process of morning awakening is associated with a marked increase in cortisol secretion, the cortisol awakening response (CAR), as well as with a burst in cardiovascular (CV) activation. Whilst the CAR is largely driven by awakening-induced activation of hypothalamic-pituitary-adrenal axis, it is fine-tuned by direct sympathetic input to the adrenal gland. In parallel, awakening-induced activation of the CV system is associated with a shift towards dominance of the sympathetic branch of the autonomic nervous system. Moreover, the CAR, in common with trait-like heart rate variability (HRV), is widely reported to be associated with psychosocial variables and health outcomes. These commonalities led us to examine associations between the CAR and both concurrent awakening-induced changes and trait-like estimates in cardiovascular activity (heart rate (HR) and HRV). Self-report measures of difficulties in emotion regulation and chronic stress were also obtained. Forty-three healthy participants (mean age: 23 years) were examined on two consecutive weekdays. On both days, heart interbeat interval (IBI) data was obtained from sedentary laboratory recordings as well as from recordings over the peri-awakening period. Salivary free cortisol concentrations were determined on awakening and 15, 30, and 45min post-awakening on both study days. Data from a minimum of 36 participants were available for individual analyses. Results revealed significant awakening-induced changes in cortisol, HR and HRV measures; however, no associations were found between the simultaneous post-awakening changes of these variables. Similarly, awakening-induced changes in cortisol, HR and HRV measures were not significantly associated with perceived stress or measures of emotion regulation. However, the CAR was found to be significantly positively correlated with steady state measures of HR and negatively correlated with steady state measures of HRV, as determined during the laboratory sessions and the peri-awakening periods. This cross-sectional study indicates that, despite consistent associations between the CAR and indices of trait-like cardiovascular activity, the CAR is not related to concurrent changes of cardiac autonomic activation following awakening. PMID:20732747

Stalder, Tobias; Evans, Phil; Hucklebridge, Frank; Clow, Angela

2011-05-01

169

Effect of Methamphetamine Dependence on Heart Rate Variability  

PubMed Central

Background Methamphetamine (METH) is an increasing popular and highly addictive stimulant associated with autonomic nervous system (ANS) dysfunction, cardiovascular pathology, and neurotoxicity. Heart rate variability (HRV) has been used to assess autonomic function and predict mortality in cardiac disorders and drug intoxication, but has not been characterized in METH use. We recorded HRV in a sample of currently abstinent individuals with a history of METH dependence compared to age- and gender-matched drug-free comparison subjects. Method HRV was assessed using time domain, frequency domain, and nonlinear entropic analyses in 17 previously METH-dependent and 21 drug-free comparison individuals during a 5 minute rest period. Results The METH-dependent group demonstrated significant reduction in HRV, reduced parasympathetic activity, and diminished heartbeat complexity relative to comparison participants. More recent METH use was associated with increased sympathetic tone. Conclusion Chronic METH exposure may be associated with decreased HRV, impaired vagal function, and reduction in heart rate complexity as assessed by multiple methods of analysis. We discuss and review evidence that impaired HRV may be related to the cardiotoxic or neurotoxic effects of prolonged METH use. PMID:21182570

Henry, Brook L.; Minassian, Arpi; Perry, William

2010-01-01

170

Variable frame rate analysis for automatic speech recognition  

NASA Astrophysics Data System (ADS)

In this paper we investigate the use of variable frame rate (VFR) analysis in automatic speech recognition (ASR). First, we review VFR technique and analyze its behavior. It is experimentally shown that VFR improves ASR performance for signals with low signal-to-noise ratios since it generates improved acoustic models and substantially reduces insertion and substitution errors although it may increase deletion errors. It is also underlined that the match between the average frame rate and the number of hidden Markov model states is critical in implementing VFR. Secondly, we analyze an effective VFR method that uses a cumulative, weighted cepstral-distance criterion for frame selection and present a revision for it. Lastly, the revised VFR method is combined with spectral- and cepstral-domain enhancement methods including the minimum statistics noise estimation (MSNE) based spectral subtraction and the cepstral mean subtraction, variance normalization and ARMA filtering (MVA) process. Experiments on the Aurora 2 database justify that VFR is highly complementary to the enhancement methods. Enhancement of speech both facilitates the frame selection in VFR and provides de-noised speech for recognition.

Tan, Zheng-Hua

2007-09-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

172

Decreased heart rate variability in surgeons during night shifts  

PubMed Central

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

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

2014-01-01

173

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

E-print Network

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were to reduce postflight orthostatic intolerance. Key words: parabolic flight; heart rate; blood pressure

174

Air velocity distributions inside tree canopies from a variable-rate air-assisted sprayer  

Technology Transfer Automated Retrieval System (TEKTRAN)

A variable-rate, air assisted, five-port sprayer had been in development to achieve variable discharge rates of both liquid and air. To verify the variable air rate capability by changing the fan inlet diameter of the sprayer, air jet velocities impeded by plant canopies were measured at various loc...

175

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

PubMed Central

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

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

2014-01-01

176

Heart Rate Variability and Sensorimotor Polyneuropathy in Type 1 Diabetes  

PubMed Central

OBJECTIVE Reduced heart rate variability (HRV) is classically viewed as an early phenomenon in diabetic sensorimotor polyneuropathy (DSP). We aimed to determine the characteristics of HRV across the spectrum of clinical DSP in type 1 diabetes. RESEARCH DESIGN AND METHODS Eighty-nine diabetic subjects and 60 healthy volunteers underwent assessment of RR interval variation (RRvar) during deep breathing and clinical and electrophysiological examination. We examined the distribution of age-standardized RRvar across the spectrum of clinical DSP, identified variables associated with RRvar in multivariate regression, and compared RRvar with validated measures of neuropathy. RESULTS Age-standardized RRvar had a significant, step-wise, inverse relationship with ordinal categories of increasing DSP severity (? = ?5.4, P < 0.0001) among subjects with diabetes. Case subjects with DSP had substantially lower age-standardized RRvar compared with diabetic control subjects without DSP (? = ?5.2, P < 0.01), although there was substantial overlap of RRvar between diabetic case subjects and control subjects and the healthy volunteer cohort. In multivariate analysis, advanced age was independently associated with lower RRvar in both healthy volunteers and diabetic subjects, whereas higher glycated hemoglobin A1c and systolic blood pressure were independently associated with lower RRvar in diabetic subjects. RRvar had a significant association with validated measures of large and small fiber neuropathy. CONCLUSIONS HRV may be a biomarker for clinical DSP and is associated cross-sectionally with both early and late measures of neuropathy. The low HRV observed in some control subjects without DSP and in most case subjects with severe DSP may signify that HRV has different prognostic implications in these groups, requiring further longitudinal study. PMID:22357183

Orlov, Steven; Bril, Vera; Orszag, Andrej; Perkins, Bruce A.

2012-01-01

177

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

PubMed

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

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

2014-12-01

178

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

PubMed Central

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

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

2013-01-01

179

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. PMID:16259639

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

2005-01-01

180

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

PubMed Central

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

Chouchou, Florian; Desseilles, Martin

2014-01-01

181

Nonlinear Control of Heart Rate Variability in Human Infants  

NASA Astrophysics Data System (ADS)

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

Sugihara, George; Allan, Walter; Sobel, Daniel; Allan, Kenneth D.

1996-03-01

182

Effect of Acupuncture on Heart Rate Variability: A Systematic Review  

PubMed Central

Aim. To summarize all relevant trials and critically evaluate the effect of acupuncture on heart rate variability (HRV). Method. This was a systematic review with meta-analysis. Keyword search was conducted in 7 databases for randomized controlled trials (RCTs). Data extraction and risk of bias were done. Results. Fourteen included studies showed a decreasing effect of acupuncture on low frequency (LF) and low frequency to high frequency ratio (LF/HF ratio) of HRV for nonhealthy subjects and on normalized low frequency (LF norm) for healthy subjects. The overall effect was in favour of the sham/control group for high frequency (HF) in nonhealthy subjects and for normalized high frequency (HF norm) in healthy subjects. Significant decreasing effect on HF and LF/HF ratio of HRV when acupuncture was performed on ST36 among healthy subjects and PC6 among both healthy and nonhealthy subjects, respectively. Discussion. This study partially supports the possible effect of acupuncture in modulating the LF of HRV in both healthy and nonhealthy subjects, while previous review reported that acupuncture did not have any convincing effect on HRV in healthy subjects. More published work is needed in this area to determine if HRV can be an indicator of the therapeutic effect of acupuncture. PMID:24693326

Chung, Joanne W. Y.; Yan, Vincent C. M.

2014-01-01

183

Extraction of Heart Rate Variability from Smartphone Photoplethysmograms  

PubMed Central

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

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

2015-01-01

184

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

E-print Network

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

185

Heart rate variability and methylphenidate in children with ADHD.  

PubMed

Although an extensive number of studies support the efficacy and tolerability of stimulants in the treatment of attention deficit/hyperactivity disorder (ADHD), in recent years, increasing concerns have been raised about their cardiovascular safety. We investigated whether a time domain analysis of heart rate variability (HRV) recordings in 24-h ECG under medication with stimulants yielded new information about therapy control in ADHD. We analysed the HRV parameter standard deviation of all normal sinus RR intervals over 24 h (SDNN), percentage of successive normal sinus RR intervals > 50 ms (pNN50) and root-mean-square of the successive normal sinus RR interval difference (rMSSD) from 23 children diagnosed by ADHD (19 boys and 4 girls), aged 10.5 ± 2.2 years, who were consecutively referred to our outpatient clinic for paediatric cardiology. Eleven children received medication with methylphenidate (MPH), while twelve children were initially examined without medication. Of these, eight probands were re-examined after therapy with MPH was established. Controls comprised 19 children (10 boys, 9 girls) from our Holter ECG data base without any cardiac or circulatory disease. Compared to healthy controls, the ADHD children with and without MPH treatment showed significantly higher mean heart rates (ADHD without MPH: 94.3 ± 2.2; ADHD with MPH: 90.5 ± 1.8, controls: 84.7 ± 1.8). pNN50 (ADHD without MPH: 6.5 ± 2.7; ADHD with MPH: 14.2 ± 6.9, controls: 21.5 ± 9.0) and rMSSD (ADHD without MPH: 26.1 ± 4.1; ADHD with MPH: 36.7 ± 8.3, controls: 44.5 ± 10.1) were lowest in ADHD children without MPH, middle in ADHD children with MPH and highest in controls. SDNN values were not significantly different. The hourly analysis shows highly significant reduced pNN50 and rMSSD values in untreated ADHD children between 5:00 pm and 6:00 am while the pattern approaches to levels of controls during MPH treatment. Data of this pilot study indicate a decreased vagal tone with significantly diminished HRV and higher heart rates in unmedicated ADHD children. These parameters of autonomic activation are ameliorated by MPH treatment. No evidence for negative impact of MPH on HRV was detected. Further studies will clarify a potential cardio-protective effect of MPH in ADHD. PMID:22328340

Buchhorn, Reiner; Conzelmann, Annette; Willaschek, Christian; Störk, Dagmar; Taurines, Regina; Renner, Tobias J

2012-06-01

186

Population growth rates: issues and an application.  

PubMed Central

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

Godfray, H Charles J; Rees, Mark

2002-01-01

187

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

PubMed Central

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

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

2013-01-01

188

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

PubMed

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

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

2014-01-01

189

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

190

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

PubMed Central

Disturbances of fetal autonomic brain development can be evaluated from fetal heart rate patterns (HRP) reflecting the activity of the autonomic nervous system. Although HRP analysis from cardiotocographic (CTG) recordings is established for fetal surveillance, temporal resolution is low. Fetal magnetocardiography (MCG), however, provides stable continuous recordings at a higher temporal resolution combined with a more precise heart rate variability (HRV) analysis. A direct comparison of CTG and MCG based HRV analysis is pending. The aims of the present study are: (i) to compare the fetal maturation age predicting value of the MCG based fetal Autonomic Brain Age Score (fABAS) approach with that of CTG based Dawes-Redman methodology; and (ii) to elaborate fABAS methodology by segmentation according to fetal behavioral states and HRP. We investigated MCG recordings from 418 normal fetuses, aged between 21 and 40 weeks of gestation. In linear regression models we obtained an age predicting value of CTG compatible short term variability (STV) of R2 = 0.200 (coefficient of determination) in contrast to MCG/fABAS related multivariate models with R2 = 0.648 in 30 min recordings, R2 = 0.610 in active sleep segments of 10 min, and R2 = 0.626 in quiet sleep segments of 10 min. Additionally segmented analysis under particular exclusion of accelerations (AC) and decelerations (DC) in quiet sleep resulted in a novel multivariate model with R2 = 0.706. According to our results, fMCG based fABAS may provide a promising tool for the estimation of fetal autonomic brain age. Beside other traditional and novel HRV indices as possible indicators of developmental disturbances, the establishment of a fABAS score normogram may represent a specific reference. The present results are intended to contribute to further exploration and validation using independent data sets and multicenter research structures. PMID:25505399

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

2014-01-01

191

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

PubMed Central

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

Bidmon, Sonja; Röttl, Johanna

2014-01-01

192

Role of Editing of R–R Intervals in the Analysis of Heart Rate Variability  

PubMed Central

This paper reviews the methods used for editing of the R–R interval time series and how this editing can influence the results of heart rate (HR) variability analyses. Measurement of HR variability from short and long-term electrocardiographic (ECG) recordings is a non-invasive method for evaluating cardiac autonomic regulation. HR variability provides information about the sympathetic-parasympathetic autonomic balance. One important clinical application is the measurement of HR variability in patients suffering from acute myocardial infarction. However, HR variability signals extracted from R–R interval time series from ambulatory ECG recordings often contain different amounts of artifact. These false beats can be either of physiological or technical origin. For instance, technical artifact may result from poorly fastened electrodes or be due to motion of the subject. Ectopic beats and atrial fibrillation are examples of physiological artifact. Since ectopic and other false beats are common in the R–R interval time series, they complicate the reliable analysis of HR variability sometimes making it impossible. In conjunction with the increased usage of HR variability analyses, several studies have confirmed the need for different approaches for handling false beats present in the R–R interval time series. The editing process for the R–R interval time series has become an integral part of these analyses. However, the published literature does not contain detailed reviews of editing methods and their impact on HR variability analyses. Several different editing and HR variability signal pre-processing methods have been introduced and tested for the artifact correction. There are several approaches available, i.e., use of methods involving deletion, interpolation or filtering systems. However, these editing methods can have different effects on HR variability measures. The effects of editing are dependent on the study setting, editing method, parameters used to assess HR variability, type of study population, and the length of R–R interval time series. The purpose of this paper is to summarize these pre-processing methods for HR variability signal, focusing especially on the editing of the R–R interval time series. PMID:22654764

Peltola, Mirja A.

2011-01-01

193

Circadian variation of heart rate variability among welders  

PubMed Central

Objective To compare the circadian variation of hourly heart rate variability (HRV) on work and non-workdays among boilermaker construction workers. Method A panel study of 18 males monitored by 24-h ambulatory ECG over 44 observation-days on paired work and non-workdays was conducted. ECGs were analysed and the SD of normal-to-normal beats index (SDNNi) was calculated from 5-min data and summarised hourly. SDNNis over work and non-workdays were compared using linear mixed-effects models to account for repeated measures and harmonic regression to account for circadian variation. Results Both work and non-work hourly HRV exhibited circadian variation with an increase in the evening and a decrease in the afternoon. SDNNi was lower on workdays as compared with non-workdays with the largest, statistically significant differences observed between 10:00 and 16:00, during active working. Lower SDNNi, albeit smaller yet statistically significant differences, was also observed in the evening hours following work (17:00–21:00) and early morning (4:00). In regression models using all time periods, an average workday SDNNi was 8.1 ms (95% CI –9.8 to –6.3) lower than non-workday SDNNi. The circadian pattern of HRV exhibited two peaks which differed on work and non-workdays. Conclusion While workday and non-workday HRV followed a circadian pattern, decreased HRV and variation of the circadian pattern were observed on workdays. Declines and changes in the circadian pattern of HRV is a concern among this exposed population. PMID:20798005

Cavallari, Jennifer M; Fang, Shona C; Mittleman, Murray A; Christiani, David C

2011-01-01

194

Hierarchical Structure of Heart Rate Variability in Humans  

NASA Astrophysics Data System (ADS)

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

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

2004-03-01

195

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

196

Heart Rate Variability and Exercise in Aging Women  

PubMed Central

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

Blair, Steven N.; Church, Timothy S.

2012-01-01

197

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

198

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

E-print Network

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

Bhandarkar, Suchendra "Suchi" M.

199

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

E-print Network

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

200

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

E-print Network

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

Teich, Malvin C.

201

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

E-print Network

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

Boyer, Edmond

202

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

E-print Network

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

203

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

E-print Network

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

204

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

E-print Network

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

Abry, Patrice

205

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

E-print Network

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

Gonçalves, Paulo

206

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

E-print Network

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

207

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

E-print Network

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

Pikovsky, Arkady

208

The effect of heart rate on the heart rate variability response to autonomic interventions  

PubMed Central

Heart rate variability (HRV), the beat-to-beat variation in either heart rate (HR) or heart period (R-R interval), has become a popular clinical and investigational tool to quantify cardiac autonomic regulation. However, it is not widely appreciated that, due to the inverse curvilinear relationship between HR and R-R interval, HR per se can profoundly influence HRV. It is, therefore, critical to correct HRV for the prevailing HR particularly, as HR changes in response to autonomic neural activation or inhibition. The present study evaluated the effects of HR on the HRV response to autonomic interventions that either increased (submaximal exercise, n = 25 or baroreceptor reflex activation, n = 20) or reduced (pharmacological blockade: ?-adrenergic receptor, muscarinic receptor antagonists alone and in combination, n = 25, or bilateral cervical vagotomy, n = 9) autonomic neural activity in a canine model. Both total (RR interval standard deviation, RRSD) and the high frequency (HF) variability (HF, 0.24–1.04 Hz) were determined before and in response to an autonomic intervention. All interventions that reduced or abolished cardiac parasympathetic regulation provoked large reductions in HRV even after HR correction [division by mean RRsec or (mean RRsec)2 for RRSD and HF, respectively] while interventions that reduced HR yielded mixed results. ?-adrenergic receptor blockade reduced HRV (RRSD but not HF) while both RRSD and HF increased in response to increases in arterial blood (baroreceptor reflex activation) even after HR correction. These data suggest that the physiological basis for HRV is revealed after correction for prevailing HR and, further, that cardiac parasympathetic activity is responsible for a major portion of the HRV in the dog. PMID:23986716

Billman, George E.

2013-01-01

209

Heart Rate Variability as a Marker of Myocardial Perfusion  

Microsoft Academic Search

RR variability (HRV), an independent predictor of death following myocardial infarction, may also be related to other features of coronary artery disease. We evaluated its ability to differentiate among sedentary patients with chest pain ?45 years of age demonstrating either normal or abnormal myocardial perfusion with rest and exercise thallium-210 tomographic imaging. The major HRV difference between 48 men and

David Schechter; Dan Sapoznikov; Myron H. Luria; Susan Mendelson; Moshe Bocher; Roland Chisin

1998-01-01

210

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

211

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

212

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

PubMed

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

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

2014-12-01

213

Reflection of heart rate regulation on linear and nonlinear heart rate variability measures.  

PubMed

The aim of this study was to examine the dependence of heart rate variability (HRV) measures on RR interval length and to find out relationships between linear and nonlinear measures. The spectral powers in very low (VLF), low (LF) and high (HF) frequency regions, short-term scaling exponent alpha(1) and sample entropy (SampEn) were determined. All spectral powers increased with increasing RR interval length until they reached a plateau. Neighbouring spectral powers were strongly correlated. The largest fraction of the spectrum consisted of VLF (from about 40 to 95%) and the smallest of HF, although HF was most sensitive to changes in RR interval length. SampEn is also increased with increasing RR interval, reaching a plateau. The dependence of alpha(1) on RR showed a deflection point at 0.5 s. Nonlinear measures can be expressed by spectral powers: alpha(1) by a linear function of ln(LF/HF) and SampEn by a quadratic function of ln HF. We concluded that during the day an increase of HR up to 120 beats min(-1) was reflected in a reduction in HF and LF and to a smaller extent in VLF and by decreased complexity and increased correlation in RR interval series. In sleep, HRV measures are at a plateau. We suggest that below intrinsic value, HR is regulated mainly by changes of parasympathetic activity, reflected in linear and nonlinear HRV measures. PMID:16400201

Platisa, Mirjana M; Gal, Vera

2006-02-01

214

Variable bit rate video transmission through RF\\/FSO link  

Microsoft Academic Search

This paper presents a channel-adaptive video streaming scheme which adjusts video bit rate according to channel conditions and transmits video through an hybrid RF\\/free space optical (FSO) laser communication system. The design criteria of the FSO link for video transmission to 2.9 km distance have been given and adaptive bit rate video streaming according to the varying channel state over

Ahmet Akbulut; H. Alparslan Ilgin; Murat Efe

2011-01-01

215

COMPLEX VARIABLE BOUNDARY ELEMENT METHOD: APPLICATIONS.  

USGS Publications Warehouse

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

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

1985-01-01

216

Short-time nonlinear dynamical analysis of heart rate variability in dogs after acute myocardial infarction  

Microsoft Academic Search

This paper presents the concept of the short-time nonlinear dynamical analysis of heart rate variability for physiological animal experiments and pharmacological experiments as well as clinical diagnosis and prognosis. We established an animal experiment protocol of myocardial ischemia to observe the results of the short-time nonlinear dynamical analysis of heart rate variability and compared the nonlinear dynamical parameters of heart

Ming Xin Qin; Yi Min Zang; Xue Tao Shi; Feng Fu

1998-01-01

217

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

E-print Network

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

Paris-Sud XI, Université de

218

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

E-print Network

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

Meston, Cindy

219

Effect of exercise training on heart rate variability in healthy older adults  

Microsoft Academic Search

Objective To determine the effect of exercise training on cardiac autonomic modulation in normal older adults by using analysis of heart rate variability. Subjects The exercise group consisted of 7 men and 9 women aged 66 ± 4 years. The comparison group consisted of 7 men and 9 women also aged 66 ± 4 years. Method Heart rate variability was

Phyllis K. Stein; Ali A. Ehsani; Peter P. Domitrovich; Robert E. Kleiger; Jeffrey N. Rottman

1999-01-01

220

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

Microsoft Academic Search

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

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

1998-01-01

221

Review and classification of variability analysis techniques with clinical applications  

PubMed Central

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

2011-01-01

222

Rates of elementary reactions - Measurement and applications  

NASA Technical Reports Server (NTRS)

Techniques used for characterizing elementary chemical reaction kinetics are explored. Flash- or laser-photolysis (FP) involves producing reactive species on the psec time scale and monitoring the changes spectroscopically. In the discharge flow (DF) method, reactive species are produced continuously in a flow of an inert gas containing the reactants. FP avoids surface and transport effects, while DF allows several reactions to be studied in different regions of one flow. Transport and surface boundary layer models are defined for DF calculations and sample calculations are carried out to illustrate the difficulties inherent in theoretically defining the rate constants for elementary reactions. Applications of the models thus far derived in atmospheric science and combustion studies are discussed.

Kaufman, F.

1985-01-01

223

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

224

26 CFR 1.1275-5 - Variable rate debt instruments.  

Code of Federal Regulations, 2010 CFR

...that provides for annual interest payments at a rate equal to the value of 1-year French franc LIBOR as of the payment date. Variations in the value of French franc LIBOR do not measure contemporaneous changes in the cost of newly borrowed...

2010-04-01

225

Effect of Phototherapy on Neonatal Heart Rate Variability and Complexity  

Microsoft Academic Search

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

Amir Weissman; Elad Berkowitz; Tatiana Smolkin; Shraga Blazer

2009-01-01

226

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

227

Online smoothing of live, variable-bit-rate video  

Microsoft Academic Search

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

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

1997-01-01

228

Online Smoothing of Variable-Bit-Rate Streaming Video  

Microsoft Academic Search

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

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

2000-01-01

229

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. PMID:8198881

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

1994-01-01

230

Approximate entropy and point correlation dimension of heart rate variability in healthy subjects  

Microsoft Academic Search

The contribution of nonlinear dynamics to heart rate variability in healthy humans was examined using surrogate data analysis.\\u000a Several measures of heart rate variability were used and compared. Heart rates were recorded for three hours and original\\u000a data sets of 8192 R-R intervals created. For each original data set (n=34), three surrogate data sets were made by shuffling\\u000a the order

Robert J. Storella; Harrison W. Wood; Kenneth M. Mills; Jørgen K. Kanters; Michael V. Højgaard; Niels-Henrik Holstein-Rathlou

1998-01-01

231

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

E-print Network

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

Paris-Sud XI, Université de

232

A Bayesian classification of heart rate variability data  

NASA Astrophysics Data System (ADS)

We propose a simple Bayesian method for the classification of time series signals originating from mutually exclusive sources. In particular, the method is used to address the question of whether a 24-h recording of human heart rate data is produced by a normally functioning heart or by one exhibiting symptoms of congestive heart failure. Our method correctly classifies 18 of 18 normal heart data sets, and 38 of 44 congestive failure data sets.

Muirhead, R. J.; Puff, R. D.

2004-05-01

233

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.

234

Climatic variability in upper ocean ventilation rates diagnosed using chlorofluorocarbons  

Microsoft Academic Search

The chlorofluorocarbon CFC-12 (CCl2F2) distributions from two occupations of a meridional hydrographic section in the eastern North Atlantic are used to describe the oceanic penetration of CFCs and change in the integrated ventilation patterns over the five years from 1988 to 1993. The CFC-12 water-column inventories increased by 30-40%, despite a slowing atmospheric growth rate (14%), because of continuing uptake

Scott C. Doney; John L. Bullister; Rik Wanninkhof

1998-01-01

235

Climatic variability in upper ocean ventilation rates diagnosed using chlorofluorocarbons  

Microsoft Academic Search

The chlorofluorocarbon CFC-12 (CCl2F2) distributions from two occupations of a meridional hydrographic section in the eastern North Atlantic are used to describe the oceanic penetration of CFCs and change in the integrated ventilation patterns over the five years from 1988 to 1993. The CFC-12 water-column inventories increased by 30–40%, despite a slowing atmospheric growth rate (14%), because of continuing uptake

Scott C. Doney; John L. Bullister; Rik Wanninkhof

1998-01-01

236

Multiport solid-state imager characterization at variable pixel rates  

SciTech Connect

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

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

1993-08-01

237

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

PubMed

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

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

2015-02-01

238

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

239

Accounting for the spatial rainfall variability in urban modelling applications.  

PubMed

In hydrological and hydrodynamic modelling of urban catchments, the spatial variability of rainfall is often neglected. This spatial variability encloses two aspects: (1) the spatial variability of the statistical properties of rainfall, and (2) the non-uniform spatial distribution of rainfall over the modelled catchments. In an ongoing research project for the Ministry of the Flemish Community (Belgium), the influence of this spatial rainfall variability on the results of modelling applications is studied. At the same time, most efficient methods to reduce this influence are determined. The results of the research can be applied directly in Flanders. They consist of a combination of unified IDF-relationships, spatial correction factors (generally applicable formulas), a stochastic simulation model for spatial rainfall (software) and a methodology for improving the spatial correction factors in a case-specific way by performing simulations with the model. PMID:11888171

Willems, P; Berlamont, J

2002-01-01

240

Human heart rate variability relation is unchanged during motion sickness  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

241

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

PubMed Central

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

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

2013-01-01

242

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

E-print Network

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

243

Emergence of dynamical complexity related to human heart rate variability  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

244

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. PMID:8297686

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

1994-01-01

245

February 2005 Determining Optimum Nitrogen Application Rates for Corn  

E-print Network

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

Balser, Teri C.

246

Embedded computer controlled premixing inline injection system for air-assisted variable-rate sprayers  

Technology Transfer Automated Retrieval System (TEKTRAN)

Improvements to reduce chemical waste and environmental pollution for variable-rate sprayers used in orchards and ornamental nurseries require inline injection techniques. A microprocessor controlled premixing inline injection system implementing a ceramic piston chemical metering pump and two small...

247

IEEE Benelux EMBS Symposium December 6-7, 2007 HEART RATE VARIABILITY DURING ACTIVE AND QUIET  

E-print Network

of cardiac chaos in congestive heart failure. Nature, 389:492-495, 1997. [2] Poon C.-S. et al. TitrationIEEE Benelux EMBS Symposium December 6-7, 2007 HEART RATE VARIABILITY DURING ACTIVE AND QUIET SLEEP

248

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

E-print Network

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

Brown, Emery N.

249

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

EPA Science Inventory

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

250

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

Microsoft Academic Search

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

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

2007-01-01

251

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

Microsoft Academic Search

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

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

252

Highly variable spread rates in replicated biological invasions: fundamental limits to predictability.  

PubMed

Although mean rates of spread for invasive species have been intensively studied, variance in spread rates has been neglected. Variance in spread rates can be driven exogenously by environmental variability or endogenously by demographic or genetic stochasticity in reproduction, survival, and dispersal. Endogenous variability is likely to be important in spread but has not been studied empirically. We show that endogenously generated variance in spread rates is remarkably high between replicated invasions of the flour beetle Tribolium castaneum in laboratory microcosms. The observed variation between replicate invasions cannot be explained by demographic stochasticity alone, which indicates inherent limitations to predictability in even the simplest ecological settings. PMID:19762641

Melbourne, Brett A; Hastings, Alan

2009-09-18

253

Avalanche Photo-Detection for High Data Rate Applications  

E-print Network

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

H. B. Coldenstrodt-Ronge; C. Silberhorn

2007-09-19

254

Altered heart rate and blood pressure variability in mice lacking the Mas protooncogene  

Microsoft Academic Search

Heart rate variability is a relevant predictor of cardiovascular risk in humans. A significant genetic influence on heart rate variability is suggested, although the genes involved are ill-defined. The Mas- protooncogene encodes a G-protein-coupled receptor with seven trans- membrane domains highly expressed in testis and brain. Since this receptor is supposed to interact with the signaling of angiotensin II, which

T. Walther; N. Wessel; N. Kang; A. Sander; C. Tschöpe; H. Malberg; M. Bader; A. Voss

2000-01-01

255

Heart Rate Variability during Exercise Performed below and above Ventilatory Threshold  

Microsoft Academic Search

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

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

2004-01-01

256

Supporting Stored Video: Reducing Rate Variability and End-to-End Resource Requirements through Optimal Smoothing  

Microsoft Academic Search

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

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

1996-01-01

257

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

258

Parathyroidectomy and Heart Rate Variability in Patients with Stage 5 CKD  

PubMed Central

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

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

2013-01-01

259

Image coding - Variable rate differential pulse code modulation through fixed rate channel  

Microsoft Academic Search

A specific implementation of a generalized buffer feedback technique is introduced. It can control the average rate of a wide variety of compression techniques which can be locally adaptive both in quantizer structure and, more importantly, in compression rate. An important consideration in a compression system, in addition to performance, is implementation complexity. Buffer feedback introduces additional hardware complexity. However,

A. G. Tescher; R. V. Cox

1977-01-01

260

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...

261

Applications of Precision Doppler Velocity Measurements in Variable Star Studies  

Microsoft Academic Search

Techniques developed over the last 10 years have improved the precision of Doppler velocity measurements by more than two orders of magnitude. While most of this work has centered on the discovery of extrasolar planets, a number of applications have been developed for the study of variable stars. Work carried out with the Lick Observatory Iodine absorption cell has resulted

R. P. Butler

1998-01-01

262

Cooled variable nozzle radial turbine for rotor craft applications  

NASA Technical Reports Server (NTRS)

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

Rogo, C.

1981-01-01

263

Effects of propellant composition variables on acceleration-induced burning-rate augmentation of solid propellants  

NASA Technical Reports Server (NTRS)

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 function of the reference burning rate and not controlled by binder or catalyst type at a given reference rate. A nonaluminized propellant and a low rate double-base propellant exhibited strong transient rate augmentation due to surface pitting resulting from the retention of hot particles on the propellant surface.

Northam, G. B.

1972-01-01

264

Cost Bases for Incentive Rates Applicable to Industrial Loads  

E-print Network

COST BASES FOR INCENTIVE RATES APPLICABLE TO INDUSTRIAL LOADS CARL N. STOVER, JR. Executive Vice President C. H. Guernsey &Company Oklahoma City, Oklahoma ABSTRACT Incentive rates applicable to industrial customers are presently receiving a... considered. Conditions, in certain instances, have changed for both the electric utility and the industrial customer; an incentive type rate is one response to the changing conditions. There are, however, a variety of incentive rate options. Some...

Stover, C. N.

265

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

PubMed

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

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

2014-09-17

266

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

PubMed

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

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

2008-01-01

267

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

268

Power spectrum of heart rate variability in exercising humans: The effect of exercise intensity  

Microsoft Academic Search

Power spectral analysis of heart rate variability (HRV) has been estimated by means of a Fourier transform method at rest in seven healthy men and three women, during a 30?minutes steady state cycle exercise test at 40%, 50%, 60%, 70% and 80% respectively, of maximal heart rate reserve (MHRR) defined as (HRmax ? HRrest). Total power (PT) of HRV was

Pavel Stejskal; Jana Rechbergová; Jirí Salinger; Radim Šlachta; Milan Elfmark; Martn Kalina; Radim Jur?a; Iva Rehová

2001-01-01

269

Heart rate variability analysis before and during exposing to low pulsed microwaves in mammals  

Microsoft Academic Search

The main objective of this work is to study the effect of low pulsed microwaves on heart rate variability signals derived from electrocardiogram signals( ) of ten cats. The cats were irradiated with rectangular pulsed microwaves at . , peak, . us wide and repetition rate applied to their brains through horns and wave guides for min followed by a

Ahmed Kamal

2007-01-01

270

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

271

The Relationship Between Spectral Changes in Heart Rate Variability and Fatigue  

Microsoft Academic Search

Fatigue is a prevalent problem in the workplace and a common symptom of many diseases. However, its relationship with the autonomic nervous system, specifically with sympathetic arousal, needs clarification. The objective of this study was to determine the association between fatigue and heart rate variability (HRV). HRV is regarded as an indicator of the autonomic regulation activity of heart rate,

Yvonne Tran; Nirupama Wijesuriya; Mika Tarvainen; Pasi Karjalainen; Ashley Craig

2009-01-01

272

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

Microsoft Academic Search

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

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

2009-01-01

273

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

Microsoft Academic Search

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

L. T. LaCount; V. Napadow; B. Kuo; J. Kim; E. N. Brown; R. Barbieri

2009-01-01

274

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

PubMed

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

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

1995-11-01

275

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

E-print Network

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

276

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

ERIC Educational Resources Information Center

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

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

2011-01-01

277

Bayesian Analysis of Multi-Study Rank Data with Application to Primate Intelligence Ratings  

E-print Network

Bayesian Analysis of Multi-Study Rank Data with Application to Primate Intelligence Ratings Valen E the cognitive abilities of various primate genera. 1 Introduction In this paper, a Bayesian latent variable collected for the purpose of ranking nonhuman primate taxa according to their \\intelligence" (We use

West, Mike

278

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.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for evaluation of farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency doma...

279

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

280

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

281

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

PubMed Central

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

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

1994-01-01

282

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

283

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

284

Workshop on Thermonuclear Reaction Rates for Astrophysics Applications  

E-print Network

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

285

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. PMID:23437276

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

2013-01-01

286

Enamel-calibrated lamellar bone reveals long period growth rate variability in humans.  

PubMed

Mammalian teeth exhibit incremental structures representing successive forming fronts of enamel at varying time scales, including a short daily increment called a cross striation and a long period called a stria of Retzius, the latter of which, in humans, occurs on average every 8-9 days. The number of daily increments between striae is called the repeat interval, which is the same period as that required to form one increment of bone, i.e. the lamella, the fundamental - if not archetypal - unit of bone. Lamellae of known formation time nevertheless vary in width, and thus their measures provide time-calibrated growth rate variability. We measured growth rate variability for as many as 6 years of continuously forming primary incremental lamellar bone from midshaft femur histological sections of sub-Saharan Africans of Bantu origin and known life history. We observed periodic growth rate variability in approximately 6- to 8-week intervals, and in some cases annual rhythms were visible. Endogenous biological periodicities, cycles manifest in the external environment, and/or perturbations of development are all potentially contained within growth rate variability studies of lamellar incremental patterns. Because lamellae are formed within defined periods of time, quantitative measures of widths of individual lamellae provide time-resolved growth rate variability that may reveal rhythms in human bone growth heretofore unknown. PMID:21525718

Bromage, Timothy G; Juwayeyi, Yusuf M; Smolyar, Igor; Hu, Bin; Gomez, Santiago; Chisi, John

2011-01-01

287

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

PubMed

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

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

2009-01-01

288

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

PubMed Central

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

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

2013-01-01

289

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

PubMed Central

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

2014-01-01

290

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

Microsoft Academic Search

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

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

2010-01-01

291

Effect of cold or thermoneutral water immersion on post-exercise heart rate recovery and heart rate variability indices  

Microsoft Academic Search

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, 5min seated recovery, followed by 5min of submaximal running exercise), randomly followed by 5min of passive

Hani Al Haddad; Paul B. Laursen; Didier Chollet; Frédéric Lemaitre; Saïd Ahmaidi; Martin Buchheit

2010-01-01

292

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

293

Continuously variable transmission: Assessment of applicability to advance electric vehicles  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

294

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

Microsoft Academic Search

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

MARTIN BUCHHEIT; CHANTAL SIMON; ANNE CHARLOUX; GABRIELLE BRANDENBERGER

2005-01-01

295

Factors Influencing Blood Pressure and Heart Rate Variability in Hypertensive Humans  

Microsoft Academic Search

SUMMARY We examined the influence of baroreceptor reflex sensitivity (the increase in pulse interval in response to a phenylephrine-induced increase in blood pressure), age, blood pressure, and \\/3-adrenergic receptor blockade on the variability of blood pressure and heart rate in essential hypertension. Fifty-six subjects were studied before treatment; intra-arterial blood pressure was recorded outside the hospital for 24 hours. Variability

JOHN S. FLORAS; M. OSMAN HASSAN; JOHN VANN JONES; BARBARA A. OSIKOWSKA; PETER S. SEVER; PETER SLEIGHT

2010-01-01

296

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

NASA Astrophysics Data System (ADS)

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

Kuang, Boyan; Mouazen, Abdul

2014-05-01

297

Cotton Profitability with Alternative Lime Application Rates, Cover Crops, Nitrogen Rates, and Tillage Methods  

Microsoft Academic Search

Soil acidity and cotton (Gossypium hirsutum L.) yield may be influenced by cover crop, N, and tillage method. Application of half the recommended lime rate may be possible without reducing lint yield and net revenue. The objective was to determine cotton yields and profitability for full and half recommended rates of lime, cover crops, N rates, and tillage methods. Data

Rebecca L. Cochran; Roland K. Roberts; James A. Larson; Donald D. Tyler

2007-01-01

298

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

Microsoft Academic Search

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

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

2011-01-01

299

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

E-print Network

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

Cammarota, Camillo

300

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

301

Nonparametric spectral analysis of heart rate variability through penalized sum of squares.  

PubMed

Researchers in a variety of biomedical fields have utilized frequency domain properties of heart rate variability (HRV), or the elapsed time between consecutive heart beats. HRV is measured from the electrocardiograph signal through the interbeat interval series. Popular approaches for estimating power spectra from these interval data apply common spectral analysis methods that are designed for the analysis of evenly sampled time series. The application of these methods to the interbeat interval series, which is indexed over an uneven time grid, requires a bias-inducing transformation. The goal of this article is to explore the use of penalized sum of squares for nonparametric estimation of the spectrum of HRV directly from the interbeat intervals. A novel cross-validation procedure is introduced for smoothing parameter selection. Empirical properties of the proposed estimation procedure are explored and compared with popular methods in a simulation study. The proposed method is used in an analysis of data from an insomnia study, which seeks to illuminate the association between the power spectrum of HRV during different periods of sleep with response to behavioral therapy. PMID:24254401

Krafty, Robert T; Zhao, Mengyuan; Buysse, Daniel J; Thayer, Julian F; Hall, Martica

2014-04-15

302

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

303

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

PubMed

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

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

2015-03-01

304

Automatic Prediction of Cardiovascular and Cerebrovascular Events Using Heart Rate Variability Analysis  

PubMed Central

Background There is consensus that Heart Rate Variability is associated with the risk of vascular events. However, Heart Rate Variability predictive value for vascular events is not completely clear. The aim of this study is to develop novel predictive models based on data-mining algorithms to provide an automatic risk stratification tool for hypertensive patients. Methods A database of 139 Holter recordings with clinical data of hypertensive patients followed up for at least 12 months were collected ad hoc. Subjects who experienced a vascular event (i.e., myocardial infarction, stroke, syncopal event) were considered as high-risk subjects. Several data-mining algorithms (such as support vector machine, tree-based classifier, artificial neural network) were used to develop automatic classifiers and their accuracy was tested by assessing the receiver-operator characteristics curve. Moreover, we tested the echographic parameters, which have been showed as powerful predictors of future vascular events. Results The best predictive model was based on random forest and enabled to identify high-risk hypertensive patients with sensitivity and specificity rates of 71.4% and 87.8%, respectively. The Heart Rate Variability based classifier showed higher predictive values than the conventional echographic parameters, which are considered as significant cardiovascular risk factors. Conclusions Combination of Heart Rate Variability measures, analyzed with data-mining algorithm, could be a reliable tool for identifying hypertensive patients at high risk to develop future vascular events. PMID:25793605

Melillo, Paolo; Izzo, Raffaele; Orrico, Ada; Scala, Paolo; Attanasio, Marcella; Mirra, Marco; De Luca, Nicola; Pecchia, Leandro

2015-01-01

305

[Analysis of heart rate variability. Background, method, and possible use in anesthesia].  

PubMed

BACKGROUND AND METHODS. Small, periodic fluctuations in heart rate are well known to physicians, the respiratory sinus arrhythmia (RSA) being the most easily detectable form of this heart rate variability (HRV). Since it is caused by changing activity of the autonomic nervous system (ANS) controlling heart rate, HRV is investigated to gain information on the functional states of the ANS. Recent developments have led to computer-aided processing of EKG signals based on time and frequency domain methods--the latter using power spectral analysis by fast Fourier or autoregressive algorithms--to exactly describe and quantify HRV. Three major regions in the frequency spectrum between 0.03 and 0.5 Hz (the suitable range for shortterm recordings) have been established: (1) a region around the respiratory rate, usually between 0.2 and 0.35 Hz, called high frequency (HF), (2) a region around 0.1 Hz attributed to vasomotor activity feedback, called low (or mid-) frequency (LF), (3) a peak around 0.04-0.05 Hz correlated to thermoregulation, called very low (or low)frequency (VLF). Power spectral density of HRV is now commonly accepted as a measure of autonomic cardiovascular control activity. By studies on vagal or sympathetic blockade, the HF (or RSA) region has been attributed solely to vagal activity, while both parts of the ANS may contribute to the other two, with, however, the vagal part predominating the resting, healthy individuals. CLINICAL APPLICATIONS/ANAESTHESIA. Thus, spectral analysis of HRV provides a measure for quantifying sympatho-vagal balance in its physiological range. Additionally, reduction of HRV along with cardiovascular disease, including hypertension, myocardial infarction, heart failure and sudden cardiac death, as well as with autonomic dysregulation, has been reported. Since is also a striking reduction produced by most anaesthetic agents, RSA and HRV are investigated as measures of anaesthetic depth. There are contradictory data on the influence of ventilation, medication, and co-existing disease on the spectrum, and thus validation of the method is still to be achieved. It has, however, been proven useful in some studies as a parameter for risk assessment of perioperative or post-infarction cardiovascular complications. PMID:8533867

Baumert, J H; Frey, A W; Adt, M

1995-10-01

306

Association of Heart Rate With Blood Pressure Variability: Implications for Blood Pressure Measurement  

Microsoft Academic Search

BackgroundAntihypertensive ?-blocker use is associated with greater intervisit blood pressure variability (BPV) and with less favorable outcomes compared to other antihypertensive agents. A theoretical model demonstrated that accuracy and precision of BP measurement are affected by heart rate (HR) at a constant cuff deflation rate. We aimed to examine the empirical relationship between HR and BPV in a clinical setting.MethodsIntratracing

Amos Cahan; Iddo Z. Ben-Dov; Michael Bursztyn

2012-01-01

307

Effect of hypobaric hypoxia on heart rate variability during exercise: a pilot field study  

Microsoft Academic Search

The influence of hypoxia on heart rate variability (HRV) has been studied under resting conditions with mixed results. Differences\\u000a have been found in physiological responses to normobaric versus hypobaric hypoxia. Our aim was to study the influence of hypobaric\\u000a hypoxia on HRV during physical exercise to determine whether HRV changes due to the exercise-induced heart rate (HR) increase\\u000a or whether

Petra Zupet; Tanja Princi; Zarko Finderle

2009-01-01

308

A Variable-Rate Spread-Spectrum System for Underwater Acoustic Communications  

Microsoft Academic Search

A key research area in underwater acoustic (UWA) communication is the development of advanced modulation and detection schemes for improved performance and range-rate product. In this communication, we propose a variable-rate underwater data transmission system based on direct sequence spread spectrum (DSSS) and complementary code keying (CCK), particularly for shallow-water acoustic channels with severe multipath propagation. We provide a suboptimum

Chengbing He; Jianguo Huang; Zhi Ding

2009-01-01

309

Design of test method and detailed ratings of variable air volume fan-coil units  

Microsoft Academic Search

The purpose of this paper is to proceed with a series of performance tests for variable air volume (VAV) fan-coil units to establish complete testing and rating procedures. Based on the guidelines described in ASHRAE standard 79-1984 (ANSI\\/ASHRAE 79-1984. Methods in testing for rating room fan-coil air conditioners) for constant air-volume (CAV) fan-coil units, we have proposed a unique testing

M. T. Ke

2002-01-01

310

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

PubMed Central

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

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

2014-01-01

311

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

PubMed

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

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

2014-02-01

312

iHeartLift: A closed loop system with bio-feedback that uses music tempo variability to improve heart rate variability  

Microsoft Academic Search

“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

Thomas C. T. Ho; Xiang. Chen

2011-01-01

313

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

314

A real-time variable bit rate MPEG2 video coding method for digital storage media  

Microsoft Academic Search

A real-time coding that performs, in one coding pass, a variable bit rate coding that capitalizes on MPEG-2 video coding is proposed. In this method, coding is performed according to the degree of difficulty in image coding. To realize this objective, the relationship between quantization scale and generated bits is modeled as a bit amount assigning function. Based on this

S. Kondo; H. Fukuda

1997-01-01

315

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

Microsoft Academic Search

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

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

2000-01-01

316

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

317

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

EPA Science Inventory

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

318

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

E-print Network

dynamics in HRV of healthy, congestive heart failure (CHF), and atrial fibrillation subjects. We show, congestive heart failure (CHF), and atrial fibrillation (AF). We shall further compare SDLE with otherMultiscale Analysis of Heart Rate Variability: A Comparison of Different Complexity Measures JING

Gao, Jianbo

319

Heart rate variability characterization: time-frequency representation and nonlinear analysis  

Microsoft Academic Search

Time-frequency representation (TFR) and complexity measures based on the correlation dimension are applied to the characterization of the Heart Rate Variability, (HRV). For this study 117 subjects are analyzed from the IDEAL database, 53 patients with idiopathic dilated cardiomyopathy (IDC); 64 normal subjects (NRM). IDC patients are classified by means of their ejection fraction. The RR series are analyzed during

M. Vallverdu; F. Claria; R. Carvajal; P. Martinez; J. L. Alonso; W. Zareba; X. Vinolas; A. Bayes de Luna; P. Caminal

1999-01-01

320

Comparative Analysis of Heart Rate Variability Between Healthy and Morbid Group Based on Correlation Dimension  

Microsoft Academic Search

Heart rate variability(HRV) is an important index to express the tensility and balance of the parasympathetic- sympathetic nerve, and it is valuable to diagnose heart and blood disease in clinical diagnosis. It was approved that HRV signal possess nonlinear characteristic, and we can analysis and represent HRV signal by nonlinear dynamic parameter, such as correlation dimension. In this paper, We

Jiafu Zhu; Wei He; Hao Yang

2008-01-01

321

Dynamic analysis of the correlation integral of Heart Rate Variability in hypertrophic cardiomyopathy patients  

Microsoft Academic Search

A dynamic analysis of the Correlation Integral (Cm) of the Heart Rate Variability signal (HRV) was applied to 50 patients with Hypertrophic Cardiomyopathy (HCM). A group of 55 healthy subjects was considered as a control group. The Correlation Integral is calculated within a moving time window in order to characterize the nonlinear dynamical behavior of the HRV of HCM patients

R. Carvajal; D. Vallverdu; J. J. Zebrowski; R. Baranowski; L. Chojnowska; P. Caminal

2001-01-01

322

The Use of Heart Rate Variability as a Novel Method to Differentiate between Affective States  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

323

Use of heart rate variability differentiates between physical and psychological states  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

324

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

325

Identifying Genetic Variants for Heart Rate Variability in the Acetylcholine Pathway  

PubMed Central

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

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

2014-01-01

326

Reliability and accuracy of heart rate variability metrics versus ECG segment duration  

Microsoft Academic Search

Despite the exponential growth in heart rate variability (HRV) research, the reproducibility and reliability of HRV metrics continues to be de- bated. We estimated the reliability of 11 metrics cal- culated from 5 min records. We also compared the accuracy of the HRV metrics calculated from ECG records spanning 10 s to 10 min as compared with the metrics calculated

James McNames; Mateo Aboy

2006-01-01

327

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

328

Low Heart Rate Variability and the Effect of Depression on Post-Myocardial Infarction Mortality  

Microsoft Academic Search

Background: Depression is associated with an in- creased risk for mortality after acute myocardial infarc- tion (MI). The purpose of this study was to determine whether low heart rate variability (HRV) mediates the effect of depression on mortality. Methods: Twenty-four-hour ambulatory electrocardio- grams were obtained from 311 depressed patients with a recent acute MI who were enrolled in the Enhancing

Robert M. Carney; James A. Blumenthal; Kenneth E. Freedland

2005-01-01

329

Heart rate variability and particulate exposure in vehicle maintenance workers: a pilot study.  

PubMed

The association between occupational exposure to PM(2.5) and heart rate variability was investigated in a repeated measures, longitudinal study of vehicle maintenance workers occupationally exposed to automobile emissions. Five subjects were monitored for occupational exposure to fine particulate matter (PM(2.5)) on 6 workdays using an aerosol photometer, validated with side-by-side sampling with a gravimetric method. End-of-day heart rate variability statistics were derived using short-term electrocardiogram recordings for each participant. Workplace carbon monoxide and outdoor, ambient fine particulate matter were also monitored. Regression statistics were used to investigate associations between same-day PM(2.5) levels and heart rate variability statistics using mixed-effects multiple regression of pooled data. No statistically significant associations were observed between occupational PM(2.5) and measures of heart rate variability. A statistically significant increase in total spectral power was associated with ambient PM(2.5) (p < 0.05). The data suggest a threshold below which no degradation in cardiac autonomic control of healthy workers occurs when challenged by occupational PM(2.5) exposure. This study was limited in population, exposure level, and type of particulate exposures. Additional studies are recommended on broader occupational populations. PMID:15238301

Eninger, Robert M; Rosenthal, Frank S

2004-08-01

330

Spectral characteristics of heart rate and blood pressure variability in primary aldosteronism  

Microsoft Academic Search

A disturbance of the autonomic cardiovascular function has been postulated in primary aldosteronism as a possible mechanism for hypertension. Using the method of spectral analysis of heart rate and blood pressure variability, the aim of this study was to assess sympathovagal interactions modulating cardiovascular function and baroreflex control in patients with primary aldosteronism. Seventeen patients (7 with adenomas and 10

Franco Veglio; Remo Melchio; Franco Rabbia; Paola Molino; Gianpiero Martini; Livio Chiandussi

1995-01-01

331

Heart rate variability in diabetic patients during orthostatic load — A spectral analytic approach  

Microsoft Academic Search

Summary Spectral analysis of heart rate variability (HRV) was used to assess the autonomic nervous control of cardiac function during orthostatic load in insulin-dependent diabetic patients and healthy subjects. The diabetic patients were divided into three groups: diabetics without neuropathy (group 1), diabetics with peripheral neuropathy (group 2), and diabetics with peripheral and autonomic neuropathy (group 3). Resting mid-frequency (MF,

F. Weise; F. Heydenreich; W. Gehrig; U. Runge

1990-01-01

332

Heart Rate Variability on 7Day Holter Monitoring Using a Bootstrap Rhythmometric Procedure  

Microsoft Academic Search

Heart rate variability (HRV) markers have been widely used to characterize the autonomous regulation state of the heart from 24-h Holter monitoring, but long-term evolution of HRV indexes is mostly unknown. A dataset of 7-day Holter recordings of 22 patients with congestive heart failure was studied. A rhythmometric procedure was designed to characterize the infradian, circadian, and ultradian components for

Rebeca Goya-Esteban; Inmaculada Mora-Jiménez; José Luis Rojo-Álvarez; Óscar Barquero-Pérez; Francisco J. Pastor-Pérez; Sergio Manzano-Fernández; Domingo A. Pascual-Figal; Arcadi García-Alberola

2010-01-01

333

Hierarchical Structure in Healthy and Diseased Heart Rate Variability in Humans  

E-print Network

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

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

2003-12-12

334

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

335

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

336

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

337

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

Microsoft Academic Search

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

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

2006-01-01

338

QoS Based Scheduling for Incorporating Variable Rate Coded Voice in BLUETOOTH  

E-print Network

1 QoS Based Scheduling for Incorporating Variable Rate Coded Voice in BLUETOOTH Shuchi Chawla Indian Institute of Technology, Delhi, India Mitali Singh mitalisi@usc.edu Abstract| Bluetooth in Bluetooth. However most other wireless networks use com- pressed voice, which requires much lesser band

Chawla, Shuchi

339

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

E-print Network

of the HRV parame- ters obtained in the present study are compared to other data reported in literature. Keywords: heart rate variability, neonates, polysomnography, ALTE, spectral analysis, de- trended abnormal events. In addition to standardized HRV parameters, recently introduced methods such as detrended

340

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

ERIC Educational Resources Information Center

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

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

2014-01-01

341

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

ERIC Educational Resources Information Center

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

Srinivasan, Krishnamachari

2007-01-01

342

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

EPA Science Inventory

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

343

MultiScale Wavelet p-Leader based Heart Rate Variability Analysis for  

E-print Network

College - Princeton University IP4AI teams #12;Introductiong ´Ey Motivation Congestive Heart Failure (CHFMultiScale Wavelet p-Leader based Heart Rate Variability Analysis for Survival Probability Dept of Medical Education, Grad School of Medical Sciences, Nagoya City University, Japan 5 Dept

Herwig, Wendt

344

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

345

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

346

Long term rain rate and Ka-band attenuation variability in Aveiro  

Microsoft Academic Search

The paper presents and discusses a multiyear rain rate and concurrent attenuation propagation database at Ka- band in a Earth-Satellite link. Data is analysed in several temporal scales from hourly, monthly, seasonally to yearly periods concerning mainly variability issues. General local rain climate issues are highlighted. Long term seasonal attenuation distributions are also compared to the concurrent rain attenuation and

Armando Rocha; Claudia Camacho

2011-01-01

347

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

PubMed Central

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

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

2014-01-01

348

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

ERIC Educational Resources Information Center

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

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

2013-01-01

349

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

Microsoft Academic Search

Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting

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

2008-01-01

350

Heart rate variability in diabetic children: Sensitivity of the time- and frequency-domain methods  

Microsoft Academic Search

Heart rate variability (HRV) is a noninvasive index of the neural activity of the heart. Although also influenced by the sympathetic activity of the heart, HRV is essentially determined by the vagal stimulation of the heart. Several HRV abnormalities have been described in adults with diabetes mellitus. However, there are few data on HRV in children with diabetes mellitus. In

Ay?ehan Akinci; Alpay Çeliker; Engin Baykal; Tahsin Teziç

1993-01-01

351

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

352

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

353

Results of Propellant Mixing Variable Study Using Precise Pressure-Based Burn Rate Calculations  

NASA Technical Reports Server (NTRS)

A designed experiment was conducted in which three mix processing variables (pre-curative addition mix temperature, pre-curative addition mixing time, and mixer speed) were varied to estimate their effects on within-mix propellant burn rate variability. The chosen discriminator for the experiment was the 2-inch diameter by 4-inch long (2x4) Center-Perforated (CP) ballistic evaluation motor. Motor nozzle throat diameters were sized to produce a common targeted chamber pressure. Initial data analysis did not show a statistically significant effect. Because propellant burn rate must be directly related to chamber pressure, a method was developed that showed statistically significant effects on chamber pressure (either maximum or average) by adjustments to the process settings. Burn rates were calculated from chamber pressures and these were then normalized to a common pressure for comparative purposes. The pressure-based method of burn rate determination showed significant reduction in error when compared to results obtained from the Brooks' modification of the propellant web-bisector burn rate determination method. Analysis of effects using burn rates calculated by the pressure-based method showed a significant correlation of within-mix burn rate dispersion to mixing duration and the quadratic of mixing duration. The findings were confirmed in a series of mixes that examined the effects of mixing time on burn rate variation, which yielded the same results.

Stefanski, Philip L.

2014-01-01

354

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

PubMed Central

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

2013-01-01

355

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. PMID:18230624

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

2008-01-01

356

44 CFR 61.8 - Applicability of risk premium rates.  

Code of Federal Regulations, 2014 CFR

...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program INSURANCE COVERAGE...Risk premium rates are applicable to all flood insurance made available for: ...date of the initial FIRM, whichever is later. (b) Coverage which exceeds the...

2014-10-01

357

44 CFR 61.8 - Applicability of risk premium rates.  

Code of Federal Regulations, 2011 CFR

...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program INSURANCE COVERAGE...Risk premium rates are applicable to all flood insurance made available for: ...date of the initial FIRM, whichever is later. (b) Coverage which exceeds the...

2011-10-01

358

44 CFR 61.8 - Applicability of risk premium rates.  

Code of Federal Regulations, 2013 CFR

...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program INSURANCE COVERAGE...Risk premium rates are applicable to all flood insurance made available for: ...date of the initial FIRM, whichever is later. (b) Coverage which exceeds the...

2013-10-01

359

44 CFR 61.8 - Applicability of risk premium rates.  

Code of Federal Regulations, 2012 CFR

...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program INSURANCE COVERAGE...Risk premium rates are applicable to all flood insurance made available for: ...date of the initial FIRM, whichever is later. (b) Coverage which exceeds the...

2012-10-01

360

44 CFR 61.8 - Applicability of risk premium rates.  

Code of Federal Regulations, 2010 CFR

...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program INSURANCE COVERAGE...Risk premium rates are applicable to all flood insurance made available for: ...date of the initial FIRM, whichever is later. (b) Coverage which exceeds the...

2010-10-01

361

Autonomic response to tactical pistol performance measured by heart rate variability.  

PubMed

Thompson, AG, Swain, DP, Branch, JD, Spina, RJ, and Grieco, CR. Autonomic response to tactical pistol performance measured by heart rate variability. J Strength Cond Res 29(4): 926-933, 2015-This study evaluated changes in autonomic tone during a tactical pistol competition. At rest and during a match, heart rate variability (HRV) was examined in 28 healthy subjects. Heart rate variability time-domain variables (including interbeat interval [IBI]) and frequency-domain variables (low frequency [LF], high frequency [HF], total power [TP]) measured during shooting were subtracted from those measured during rest to produce ?s. The shooting task involved several, rapid tactical maneuvers. Raw time to completion and inaccurate shots (points down [PDs]) were recorded and combined to form a match score where lower values indicated superior shooting performance. Mean (±SD) raw time was 135.9 ± 34.1 seconds, PDs were 78 ± 34, and match score was 175.3 ± 39.8. Shooting decreased IBI (i.e., increased heart rate) and LF. ?LF, ?HF, and ?TP were independent of ?IBI. Raw time was significantly (p ? 0.05) correlated to shooting IBI (r = 0.404) and ?IBI (r = -0.426). Points down were significantly correlated to ?TP (r = 0.416) and ?LF (r = 0.376). Match score was significantly correlated to ?IBI (r = -0.458), ?HF (r = 0.467), ?LF (r = 0.377), and ?TP (r = 0.451). In conclusion, individuals with a greater decrease in IBI (and thus heart rate) performed better by accomplishing the match faster. Individuals with less change in stress-related HRV measures (LF, HF, and TP) performed better through improved accuracy. Thus, HRV-derived sympathetic response is significantly related to shooting performance and should be used to assess marksmanship effectiveness under duress. PMID:25029000

Thompson, Andrew G; Swain, David P; Branch, J David; Spina, Robert J; Grieco, Carmine R

2015-04-01

362

The relationship between heart rate variability and inflammatory markers in cardiovascular diseases  

PubMed Central

Summary Introduction Recent evidence implicates a cholinergic anti-inflammatory pathway. Because vagus nerve activity mediates some heart rate variability (HRV), this qualitative review examines the literature concerning circulating cytokines and HRV in cardiovascular function in humans. This qualitative review examines the literature concerning circulating cytokines and HRV in cardiovascular function in humans. Methods Thirteen studies on HRV, inflammation, and cardiovascular function were located by electronic library search and descriptively reviewed. Results The relationship between HRV and inflammation was studied in healthy controls, patients with acute or stable coronary heart disease (CHD), patients with metabolic syndrome or impaired glucose tolerance and patients with kidney failure. Investigations focused mainly on lnterleukin-6 (IL-6) and C-reactive peptide (CRP). The majority of reviewed studies reported that parasympathetic nervous system tone as inferred from heart rate variability is inversely related to inflammatory markers (r values between ?0.2 and ?0.4). The relationships with inflammatory markers were similar whether derived from ECG signals as short as 5–30 min or from 24-h ECG readings for HRV analyses. While inflammatory markers appear to be related to HRV, it is a mistake to assume that the traditional “vagal measures” of HRV (such as high frequency heart rate variability) are the driving factors. Indeed, low frequency heart rate variability, a complex measure reflecting both parasympathetic and sympathetic activity, is the more commonly associated measure linked to inflammatory markers. Discussion Heart rate variability is inversely correlated with inflammatory markers in healthy individuals as well as in those with cardiovascular diseases. PMID:18819754

Haensel, Alexander; Mills, Paul J.; Nelesen, Richard A.; Ziegler, Michael G.; Dimsdale, Joel E.

2014-01-01

363

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

E-print Network

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

364

A Conceptual Evaluation of Sustainable Variable-Rate Agricultural Residue Removal  

SciTech Connect

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

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

2012-10-01

365

Experiences with leak rate calculations methods for LBB application  

SciTech Connect

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

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

1997-04-01

366

Effects of variability and rate on battery charge storage and lifespan  

NASA Astrophysics Data System (ADS)

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

Krieger, Elena Marie

367

Heart rate variability in elite triathletes, is variation in variability the key to effective training? A case comparison.  

PubMed

Measures of an athlete's heart rate variability (HRV) have shown potential to be of use in the prescription of training. However, little data exists on elite athletes who are regularly exposed to high training loads. This case study monitored daily HRV in two elite triathletes (one male: 22 year, VO2max 72.5 ml kg min(-1); one female: 20 year, VO2max 68.2 ml kg min(-1)) training 23 ± 2 h per week, over a 77-day period. During this period, one athlete performed poorly in a key triathlon event, was diagnosed as non-functionally over-reached (NFOR) and subsequently reactivated the dormant virus herpes zoster (shingles). The 7-day rolling average of the log-transformed square root of the mean sum of the squared differences between R-R intervals (Ln rMSSD), declined towards the day of triathlon event (slope = -0.17 ms/week; r2 = -0.88) in the NFOR athlete, remaining stable in the control (slope = 0.01 ms/week; r2 = 0.12). Furthermore, in the NFOR athlete, coefficient of variation of HRV (CV of Ln rMSSD 7-day rolling average) revealed large linear reductions towards NFOR (i.e., linear regression of HRV variables versus day number towards NFOR: -0.65%/week and r2 = -0.48), while these variables remained stable for the control athlete (slope = 0.04%/week). These data suggest that trends in both absolute HRV values and day-to-day variations may be useful measurements indicative of the progression towards mal-adaptation or non-functional over-reaching. PMID:22367011

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

2012-11-01

368

Short-Term Heart Rate Variability—Influence of Gender and Age in Healthy Subjects  

PubMed Central

In the recent years, short-term heart rate variability (HRV) describing complex variations of beat-to-beat interval series that are mainly controlled by the autonomic nervous system (ANS) has been increasingly analyzed to assess the ANS activity in different diseases and under various conditions. In contrast to long-term HRV analysis, short-term investigations (<30 min) provide a test result almost immediately. Thus, short-term HRV analysis is suitable for ambulatory care, patient monitoring and all those applications where the result is urgently needed. In a previous study, we could show significant variations of 5-min HRV indices according to age in almost all domains (linear and nonlinear) in 1906 healthy subjects from the KORA S4 cohort. Based on the same group of subjects, general gender-related influences on HRV indices are to be determined in this study. Short-term 5-min HRV indices from linear time and frequency domain and from nonlinear methods (compression entropy, detrended fluctuation analysis, traditional and segmented Poincaré plot analysis, irreversibility analysis, symbolic dynamics, correlation and mutual information analysis) were determined from 782 females and 1124 males. First, we examined the gender differences in two age clusters (25–49 years and 50–74 years). Secondly, we investigated the gender-specific development of HRV indices in five age decade categories, namely for ages 25–34, 35–44, 45–54, 55–64 and 65–74 years. In this study, significant modifications of the indices according to gender could be obtained, especially in the frequency domain and correlation analyses. Furthermore, there were significant modifications according to age in nearly all of the domains. The gender differences disappeared within the last two age decades and the age dependencies disappeared in the last decade. To summarize gender and age influences need to be considered when performing HRV studies even if these influences only partly differ. PMID:25822720

Voss, Andreas; Schroeder, Rico; Heitmann, Andreas; Peters, Annette; Perz, Siegfried

2015-01-01

369

Structure of growing microtubule ends: two-dimensional sheets close into tubes at variable rates  

PubMed Central

Observation of microtubule growth at different rates by cryo-electron microscopy reveals that the ends range from blunt to long, gently curved sheets. The mean sheet length increases with the growth rate while the width of the distributions increases with the extent of assembly. The combination of a concentration dependent growth rate of the tubulin sheet with a variable closure rate of the microtubule cylinder, results in a model in which stochastic fluctuations in sheet length and tubulin conformation confine GTP-tubulins to microtubule ends. We propose that the variability of microtubule growth rate observed by video microscopy (Gildersleeve, R. F., A. R. Cross, K. E. Cullen, A. P. Fagen, and R. C. Williams. 1992. J. Biol. Chem. 267: 7995- 8006, and this study) is due to the variation in the rate of cylinder closure. The curvature of the sheets at the end of growing microtubules and the small oligomeric structures observed at the end of disassembling microtubules, indicate that tubulin molecules undergo conformational changes both during assembly and disassembly. PMID:7775577

1995-01-01

370

Reducing Application Runtime Variability on Jaguar XT5  

SciTech Connect

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

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

2010-01-01

371

Necessary conditions for the optimality of variable rate residual vector quantizers  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

372

Human fetal breathing: associated changes in heart rate and beat-to-beat variability.  

PubMed

A computerized quantification of fetal heart rate and beat-to-beat variability was performed during and between fetal breathing episodes. Sixteen healthy pregnant women at term participated in the study. The results indicate that fetal breathing is associated with a significant increase in beat-to-beat variability (from 4.48 +/- 1.66 between breathing episodes to 5.80 +/- 2.04 during breathing episodes, p less than 0.01) and a small but significant decrease in fetal heart rate (from 142.7 +/- 8.6 bpm between breathing episodes to 140.4 +/- 8.6 bpm during breathing episodes, p less than 0.05). PMID:3970108

Divon, M Y; Zimmer, E Z; Platt, L D; Paldi, E

1985-02-01

373

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

PubMed Central

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

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

2014-01-01

374

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

NASA Astrophysics Data System (ADS)

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

Mirzazadeh, Abolfazl

2009-08-01

375

Subjective probability Practical aspects Application to mortality rate estimation Summary A primer on Bayesian statistics, with an application to  

E-print Network

Subjective probability Practical aspects Application to mortality rate estimation Summary A primer on Bayesian statistics, with an application to mortality rate estimation Peter Hoff University of Washington #12;Subjective probability Practical aspects Application to mortality rate estimation Summary Outline

Hoff, Peter

376

Abstract--Cardiovascular variables such as heart rate (HR) and blood pressure (BP) are robustly regulated by an  

E-print Network

Abstract--Cardiovascular variables such as heart rate (HR) and blood pressure (BP) are robustly-5]. For instance, several authors have used the time series of heart rate (HR) and blood pressure (BP) to obtain

Chen, Yiling

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

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

NASA Technical Reports Server (NTRS)

The use of spectral techniques to quantify short term heart rate fluctuations on the order of seconds to minutes has helped define the autonomic contributions to beat-to-beat control of heart rate. We used similar techniques to quantify the entire spectrum (0.00003-1.0 Hz) of heart rate variability during 24 hour ambulatory ECG monitoring. The ECG from standard Holter monitor recordings from normal subjects was sampled with the use of a phase locked loop, and a heart rate time series was constructed at 3 Hz. Frequency analysis of the heart rate signal was performed after a nonlinear filtering algorithm was used to eliminate artifacts. A power spectrum of the entire 24 hour record revealed power that was inversely proportional to frequency, 1/f, over 4 decades from 0.00003 to 0.1 Hz (period approximately 10 hours to 10 seconds). Displaying consecutive spectra calculated at 5 minute intervals revealed marked variability in the peaks at all frequencies throughout the 24 hours, probably accounting for the lack of distinct peaks in the spectra of the entire records.

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

1988-01-01

379

Increase in the embedding dimension in the heart rate variability associated with left ventricular abnormalities  

NASA Astrophysics Data System (ADS)

In the present study, the authors report evidence that the existence of premature ventricular contractions increases the embedding dimension of the cardiac dynamics. They also analyze patients with congestive heart failure, a severe clinical condition associated with abnormal left ventricular function. Results also show an increase in the embedding dimension of the heart rate variability. They used electrocardiograms collected by themselves with quality standards that make them comparable with other databases.

Andrés, D. S.; Irurzun, I. M.; Mitelman, J.; Mola, E. E.

2006-10-01

380

Effects of dynamic resistance training on heart rate variability in healthy older women  

Microsoft Academic Search

  \\u000a Twenty healthy women aged between 65 and 74 years, trained three times a week, for 16 weeks, on a cycle ergometer, to determine\\u000a the effects of dynamic resistance training on heart rate variability (HRV). Subjects were allocated to two training groups,\\u000a high (HI, n=10) and low (LO, n=10) intensity. The HI group performed eight sets of 8 revolutions at 80% of the

Roberta Forte; Giuseppe De Vito; Francesco Figura

2003-01-01

381

An Embedded Variable Bit-Rate Audio Coder for Ubiquitous Speech Communications  

Microsoft Academic Search

In this paper, we propose an embedded variable bit-rate (VBR) audio coder to provide the flttest quality of service (QoS) and better connectivity of service for the ubiquitous speech communications. It has scalable bandwidth for narrowband to wideband speech signal, and embedded 8 32 kbit\\/s VBR corresponding to the network condition and terminal capacity. For the design of the embedded

Do Young Kim; Jong Won Park

2006-01-01

382

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

383

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

384

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

Microsoft Academic Search

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

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

2011-01-01

385

Diesel exhaust inhalation does not affect heart rhythm or heart rate variability  

Microsoft Academic Search

ObjectiveExposure to air pollution is associated with increases in cardiovascular morbidity and mortality. This study was undertaken to determine the effect of diesel exhaust inhalation on heart rhythm and heart rate variability in healthy volunteers and patients with coronary heart disease.Design and settingDouble-blind randomised crossover studies in a university teaching hospital.Patients32 healthy non-smoking volunteers and 20 patients with prior myocardial

Nicholas L Mills; Alexander E Finlayson; Manuel C Gonzalez; Håkan Törnqvist; Stefan Barath; Elen Vink; Colin Goudie; Jeremy P Langrish; Stefan Söderberg; Nicholas A Boon; Keith A A Fox; Ken Donaldson; Thomas Sandström; Anders Blomberg; David E Newby

2010-01-01

386

Signs of vagal reinnervation 4 years after heart transplantation in spectra of heart rate variability1  

Microsoft Academic Search

Several investigators have shown signs of possible sympathetic but not parasympathetic reinnervation in heart transplanted patients. Spectral analysis of heart rate and blood pressure variability is a noninvasive tool appropriate to detect a functional autonomous reinnervation to the heart. In a follow-up study, 13 patients after heart transplantation (HTx) were investigated, mean age 50.698.5 years, 18 healthy volunteers were selected

Peter U; Axel W. Frey; Alexandra Fuchs; Christina Paniara; Helmut Roskamm; Markus Schwaiger; Bruno Reichart

387

Power spectrum analysis of heart-rate variability in the young zucker rat  

Microsoft Academic Search

Cardiac autonomic control was studied in a group of five young hyperinsulinaemic, insulin resistant, Zucker fatty rats (ZFR) compared with a control group of five young Zucker lean rats (ZLR). Power spectrum analysis (PSA) of heart rate variability (HRV) was performed with autoregressive (AR) models. All rats were anaesthetised with sodium pentobarbital. Mean insulinaemia and glycaemia levels were 185+27 muU\\/ml

L. Burattini; R. Burattini; C. E. Cogo; E. Faelli; P. Ruggeri

2006-01-01

388

Hilbert-Huang Transform for Analysis of Heart Rate Variability in Cardiac Health  

Microsoft Academic Search

This paper introduces a modified technique based on Hilbert-Huang transform (HHT) to improve the spectrum estimates of heart rate variability (HRV). In order to make the beat-to-beat (RR) interval be a function of time and produce an evenly sampled time series, we first adopt a preprocessing method to interpolate and resample the original RR interval. Then, the HHT, which is

Helong Li; Sam Kwong; Lihua Yang; Daren Huang; Dongping Xiao

2011-01-01

389

Effects of exercise intensity and duration on nocturnal heart rate variability and sleep quality  

Microsoft Academic Search

Acute physical exercise may affect cardiac autonomic modulation hours or even days during the recovery phase. Although sleep\\u000a is an essential recovery period, the information on nocturnal autonomic modulation indicated by heart rate variability (HRV)\\u000a after different exercises is mostly lacking. Therefore, this study investigated the effects of exercise intensity and duration\\u000a on nocturnal HR, HRV, HR, and HRV-based relaxation,

Tero Myllymäki; Heikki Rusko; Heidi Syväoja; Tanja Juuti; Marja-Liisa Kinnunen; Heikki Kyröläinen

390

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

Microsoft Academic Search

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

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

1995-01-01

391

Is volcanic air pollution associated with decreased heart-rate variability?  

Microsoft Academic Search

ObjectivesTo determine the autonomic cardiovascular control among residents of Hawaii who are exposed to varying levels of volcanic air pollution (vog), which consists largely of sulfur dioxide (SO2) and acid aerosols.MethodsIn a cross-sectional study between April 2006 and June 2008, the authors measured cardiovagal autonomic function by heart-rate variability (HRV) in 72 healthy individuals who lived in four exposure zones

Dominic C Chow; Andrew Grandinetti; Ed Fernandez; A. J. Sutton; Tamar Elias; Barbara Brooks; Elizabeth K Tam

2010-01-01

392

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

Microsoft Academic Search

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

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

2008-01-01

393

Effect of lecturing to 200 students on heart rate variability and alpha-amylase activity  

Microsoft Academic Search

The aim of this study was to examine cardiovascular [heart rate variability (HRV)] and autonomic nervous system activation\\u000a (by evaluating salivary alpha-amylase activity) that occur in professors both to, and after, the delivery of a lecture to\\u000a 200 students and to determine whether gender is an influencing factor upon response. Fifty-two participants (26 women and\\u000a 26 men) collected eight unstimulated

Edith Filaire; Hugues Portier; Alain Massart; Luis Ramat; Anna Teixeira

2010-01-01

394

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

395

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

E-print Network

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

Sarkar, A

2006-01-01

396

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

397

Time-frequency analysis of heart rate variability signals in patients with autonomic dysfunction  

Microsoft Academic Search

An imbalance in the autonomic nervous system has been suspected in patients with coronary artery disease during episodes of silent ischemia. Frequency analysis of the beat-to-beat heart rate variability (HRV) signals reveals a signature of autonomic regulation of the heart. We performed time-frequency analysis of HRV records containing silent ischemic episodes. In 14 out of 17 (82%) HRV data sets

M. V. Kamath; T. Bentley; R. Spaziani; G. Tougas; E. L. Fallen; N. McCartney; J. Runions; A. R. M. Upton

1996-01-01

398

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

399

Perceived tiredness and heart rate variability in relation to overload during a field hockey World Cup.  

PubMed

The aim of the study was to examine the utility of perceived tiredness to predict cardiac autonomic response to overload among field hockey players during the 2006 World Cup. The French Society for Sports Medicine (SFMS) questionnaire was administered at the start of the Cup to evaluate perception of tiredness. Autonomic function was assessed nine days later at the semifinal match by time and frequency domain analysis of heart rate variability. An anxiety questionnaire was administered so that the effect of precompetitive anxiety on heart rate variability could be controlled. Results showed a negative correlation between perceived tiredness scores and time domain indexes, and a positive correlation of perceived tiredness scores and the high frequency component ratio (LF/HF ratio) of heart rate variability. Anxiety did not influence the precompetitive cardiac response despite somatic anxiety's correlation with sympathetic response (LF/HF ratio) and tiredness scores. Perceived tiredness predicted the autonomic cardiac response to competitive overload. Thus, the perceived tiredness assessment would be a good early marker of fatigue and overload states during competition. PMID:20681325

Parrado, Eva; Cervantes, Julio; Pintanel, Monica; Rodas, Gil; Capdevila, Lluís

2010-06-01

400

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

PubMed Central

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

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

2014-01-01

401

Cepheid variables and their application to the cosmological distance scale  

NASA Astrophysics Data System (ADS)

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

Hoffman, Samantha Leigh

402

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

PubMed

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

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

2014-12-01

403

[Voluntary alpha-power increasing training impact on the heart rate variability].  

PubMed

In order to study the effect of the alpha EEG power increasing training at heart rate variability (HRV) as the index of the autonomic regulation of cognitive functions there were follow tasks: (1) to figure out the impact of biofeedback in the voluntary increasing the power in the individual high-frequency alpha-band effect on heart rate variability and related characteristics of cognitive and emotional spheres, (2) to determine the nature of the relationship between alpha activity indices and heart rate variability, depending on the alpha-frequency EEG pattern at rest (3) to examine how the individual alpha frequency EEG pattern is reflected in changes HRV as a result of biofeedback training. Psychometric indicators of cognitive performance, the characteristics of the alpha-EEG activity and heart rate variability (HRV) as LF/HF and pNN50 were recorded in 27 healthy men aged 18-34 years, before, during, and after 10 sessions of training of voluntary increase in alpha power in the individual high-frequency alpha band with eyes closed. To determine the biofeedback effect on the alpha power increasing training, data subjects are compared in 2 groups: experimental (14) with the real and the control group (13 people)--with mock biofeedback. The follow up effect of trainings was studied through month over the 10 training sessions. Results showed that alpha biofeedback training enhanced the fluency and accuracy in cognitive performance, decreased anxiety and frontal EMG, increased resting frequency, width and power in individual upper alpha range only in participants with low baseline alpha frequency. While mock biofeedback increased resting alpha power only in participants with high baseline resting alpha frequency and did change neither cognitive performance, nor HRV indices. Biofeedback training eliminated the alpha power decrease in response to arithmetic task in both with high and low alpha frequency participants and this effect was followed up over the month. Mock biofeedback training has no such effect. The positive correlation between the alpha-peak frequency and pNN50 in patients with initially low, but negative--those with high baseline alpha frequency explains the multidirectional biofeedback effects on HRV in low and high alpha frequency subjects. The individual alpha-frequency EEG pattern determines the effectiveness of the alpha EEG biofeedback training in changing heart rate variability, which provides a basis for predicting the results and develop individual approaches to the biofeedback technology implementation that can be used in clinical practice for treatment and rehabilitation of psychosomatic syndromes and in educational training. PMID:23668077

Bazanova, O M; Balioz, N V; Muravleva, K B; Skoraia, M V

2013-01-01

404

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

405

Abstract The analysis of heart rate variability (HRV) aids in the diagnosis of various diseases related to the malfunction of  

E-print Network

presented a great reduction in .1 error for white noise, which is a good model for congestive heart failure Abstract² The analysis of heart rate variability (HRV) aids in the diagnosis of various diseases, with respect to .1 correlations. I. INTRODUCTION The analysis of heart rate variability (HRV) is a non

Carvalho, João Luiz

406

Intravenous cannulation of adolescents does not affect the modulation of autonomic tone assessed by heart rate and blood pressure variability  

Microsoft Academic Search

Invasive arterial monitoring alters autonomic tone. The effects of intravenous (IV) insertion are less clear. The author assessed the effects of IV insertion on autonomic activity in patients aged 11 to 19 years prior to head-up tilt by measuring heart rate, blood pressure, heart rate variability, blood pressure variability, and baroreceptor gain before and after IV insertion with continuous electrocardiography

Julian M. Stewart

2000-01-01

407

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

Microsoft Academic Search

The relation between heart rate variability, measured from standard 24 hour electrocardiogram recordings in patients convalescent after a myocardial infarction, and the occurrence of sudden death and spontaneous, symptomatic, sustained ventricular tachycardia were assessed in a consecutive series of 177 patients admitted with acute myocardial infarction and surviving to 7 days. In addition to the analysis of heart rate variability,

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

1991-01-01

408

The Relationship between Type D Personality and Heart Rate Variability in Community Mental Health Center Users  

PubMed Central

Objective Type D personality can be regarded as a promising cardiovascular risk marker that has been repeatedly linked to relevant indicators of mental health, quality of life, morbidity, and mortality in cardiac patients. Heart rate variability (HRV) is a non-invasive technology that can provide information regarding a patient's sympathetic/parasympathetic balance and the control mechanisms of the autonomic systems in the cardiovascular system. As both type D personality and HRV are parameters related to the cardiovascular system, we assumed a relationship between type D personality and HRV. This study set out to identify the relationship between type D and HRV and the differences in HRV variables between type D and non-type D personalities. Methods Patients who visited Guro Community Mental Health Center from January 2011 to December 2012 were surveyed. They were evaluated using both the Korean version of the Type D Personality-14 for type D personality and HRV. During the survey, those who reported major cardiovascular disease that can affect heart rate variability were excluded from the study. Results Our analysis included 559 participants, 249 of whom were classified as type D personality. No significant differences were found in the HRV variables between the type D group and the non-type D group. There were also no clinically meaningful correlations between HRV variables and type D total/subscale scores when controlled for patient age. Conclusion A relationship between HRV and type D personality was not identified using short-term HRV measurements in non-clinical patients with no definitive cardiovascular disease. Further studies using long-term HRV measurements in patients with cardiovascular disease are necessary to conclude an association between HRV and type D personality.

Kang, Noeul; Lim, Jeung-Suk; Hwang, Taik-Gun; Joe, Sook-Haeng

2015-01-01

409

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

PubMed

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

Lewis, Michael J; McNarry, Melitta A

2015-01-01

410

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

PubMed

The purpose of this prospective, placebo-controlled, randomized double-blind study was the examination of changes of the basic vegetative rhythms due to Cardiodoron, a composition of extracts of blossoms from Primula officinalis and Onopordon acanthium and from the herbs of Hyoscyamus niger. In its clinical use it is known as a modulating medicine in the treatment of functional disturbances of the cardiovascular system. With use of Holter monitoring, 24-h ECG recordings were obtained from 100 healthy subjects of whom 50 took the composition and 50 a placebo. Heart rate variability was evaluated from the 24-h ECGs by means of a power spectral analysis based on the Fast Fourier Transformation (FFT). Regulative influences on the rhythmic system due to the medicine were found. After four weeks of medication half of the verum group showed a tendency to an increased variability in the low and high frequency range at night (LFn: 0.04-0.15 Hz, HFn: 0.15-0.4 Hz) in contrast to the placebo group. The mean heart rate at night (HRn) showed a tendency towards a normalization in the verum group: in subjects with a low HRn the heart rate was increased and in subjects with a high HRn the heart rate was decreased. This effect could not be observed in the placebo group. After two further weeks without any medication this difference between verum and placebo was abolished. PMID:10858869

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

2000-05-01

411

Radiant heater assembly for limited reaction-rate processing applications  

Microsoft Academic Search

We discuss the design and performance of a radiant heating assembly for limited reaction-rate processing applications. The heating assembly is fabricated in stainless steel on a 300 mm bore flange for incorporation with an ultrahigh vacuum compatible low-pressure chemical vapor deposition system. The heating source is an array of 18 tungsten-halogen lamps; each lamp is rated at 360 W and

G. J. Parker; J. M. Bonar; C. M. K. Starbuck

1992-01-01

412

Providing Rate Guarantees for Internet Application Traffic Across ATM Networks  

Microsoft Academic Search

The Transmission Control Protocol\\/Internet Protocol (TCP\\/IP) protocol suite is the standard requirement for all applications that need to communicate over the Internet. As TCP\\/IP applications are unable to specify the QoS parameters needed for most of the Asynchronous Transfer Mode (ATM) services, they tend to use the Unspecified Bit Rate (UBR) service category when running across ATM networks. The UBR

Ilias Andrikopoulos; A. Liakopoulos; George Pavlou; Zhili Sun

1999-01-01

413

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

NASA Astrophysics Data System (ADS)

We investigate Ornstein Uhlenbeck and diffusion processes with variable drift rates as models of evidence accumulation in a visual discrimination task. We derive power-law and exponential drift-rate models and characterize how parameters of these models affect the psychometric function describing performance accuracy as a function of stimulus strength and viewing time. We fit the models to psychophysical data from monkeys learning the task to identify parameters that best capture performance as it improves with training. The most informative parameter was the overall drift rate describing the signal-to-noise ratio of the sensory evidence used to form the decision, which increased steadily with training. In contrast, secondary parameters describing the time course of the drift during motion viewing did not exhibit steady trends. The results indicate that relatively simple versions of the diffusion model can fit behavior over the course of training, thereby giving a quantitative account of learning effects on the underlying decision process.

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

2008-01-01

414

Evaluation of pulse rate variability obtained by the pulse onsets of the photoplethysmographic signal.  

PubMed

This work presents the evaluation of pulse rate variability (PRV) obtained from pulse onsets of photoplethysmographic (PPG) signals. Three published algorithms were used to determine the pulse onsets: diastolic point, maximum second derivative and tangent intersection. Temporal series of pulse onsets were obtained for each method, and several variability indices were derived from these series. Simultaneous ECG and PPG records were acquired from 37 healthy volunteers to evaluate the interchangeability between PRV indices and heart rate variability (HRV) indices by the Bland-Altman method. Furthermore, the concordance correlation coefficient was used to correlate the indices. In all the cases, PRV indices obtained through the tangent intersection method showed better accuracy and precision (Bland-Altman analysis, bias ± 1.96 standard deviation: low frequency, LF(ms)(2) = -28.06 ± 72.68; high frequency, HF(ms)(2) = -68.23 ± 192.85; high frequency in normalized units, HF(nu) =-2.02 ± 7.08; LF/HF = 0.17 ± 0.71) and higher correlation (concordance correlation coefficients: low frequency, LF(ms)(2) = 0.99; high frequency, HF(ms)(2) = 0.98; high frequency in normalized units, HF(nu) = 0.97; LF/HF = 0.90) with HRV indices than other methods, and could be used as a good surrogate of HRV. PMID:23348575

Posada-Quintero, H F; Delisle-Rodríguez, D; Cuadra-Sanz, M B; Fernández de la Vara-Prieto, R R

2013-02-01

415

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

416

Controlling Variable Emittance (MEMS) Coatings for Space Applications  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

417

Studying radon exhalation rates variability from phosphogypsum piles in the SW of Spain.  

PubMed

Nearly 1.0 × 10(8) tonnes of phosphogypsum were accumulated during last 50 years on a 1,200 ha disposal site near Huelva town (SW of Spain). Previous measurements of exhalation rates offered very variable values, in such a way that a worst case scenario could not be established. Here, new experimental data coupled to numerical simulations show that increasing the moisture contents or the temperature reduces the exhalation rate whilst increasing the radon potential or porosity has the contrary effect. Once the relative effects are compared, it can be drawn that the most relevant parameters controlling the exhalation rate are radon potential (product of emanation factor by (226)Ra concentration) and moisture saturation of PG. From wastes management point of view, it can be concluded that piling up the waste increasing the height instead of the surface allows the reduction of the exhalation rate. Furthermore, a proposed cover here is expected to allow exhalation rates reductions up to 95%. We established that the worst case scenario corresponds to a situation of extremely dry winter. Under these conditions, the radon exhalation rate (0.508 Bqm(-2)s(-1)) would be below though close to the upper limit established by U.S.E.P.A. for inactive phopsphogypsum piles (0.722 Bqm(-2)s(-1)). PMID:25194815

López-Coto, I; Mas, J L; Vargas, A; Bolívar, J P

2014-09-15

418

Effects of cold water immersion and active recovery on post-exercise heart rate variability.  

PubMed

The aim of the present study was to investigate the potential benefits of cold water immersion (CWI) and active recovery (AR) on blood lactate concentration ([Lac]) and heart rate variability (HRV) indices following high-intensity exercise. 20 male subjects were recruited. On the first visit, an incremental test was performed to determine maximal oxygen consumption and the associated speed (MAS). The remaining 3 visits for the performance of constant velocity exhaustive tests at MAS and different recovery methods (6 min) were separated by 7-day intervals [randomized: CWI, AR or passive recovery (PR)]. The CWI and AR lowered [Lac] (p<0.05) at 11, 13 and 15 min after exercise cessation in comparison to PR. There was a 'time' and 'recovery mode' interaction for 2 HRV indices: standard deviation of normal R-R intervals (SDNN) (partial eta squared=0.114) and natural log of low-frequency power density (lnLF) (partial eta squared=0.090). CWI presented significantly higher SDNN compared to PR at 15 min of recovery (p<0.05). In addition, greater SDNN values were found in CWI vs. AR during the application of recovery interventions, and at 30 and 75 min post-exercise (p<0.05 for all differences). The lnLF during the recovery interventions and at 75 min post-exercise was greater using CWI compared with AR (p<0.05). For square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) and natural log of high-frequency power density (lnHF), a moderate effect size was found between CWI and PR during the recovery interventions and at 15 min post-exercise. Our findings show that AR and CWI offer benefits regarding the removal of [Lac] following high-intensity exercise. While limited, CWI results in some improvement in post-exercise cardiac autonomic regulation compared to AR and PR. Further, AR is not recommended if the aim is to accelerate the parasympathetic reactivation. PMID:22722961

Bastos, F N; Vanderlei, L C M; Nakamura, F Y; Bertollo, M; Godoy, M F; Hoshi, R A; Junior, J N; Pastre, C M

2012-11-01

419

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

NASA Technical Reports Server (NTRS)

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

May, C. E.

1984-01-01

420

PERFORMANCE ANALYSIS OF LOW RATE WIRELESS TECHNOLOGIES FOR MEDICAL APPLICATIONS  

E-print Network

they perform in a healthcare/hospital environment. We consider the emerging low-rate Wireless Personal Area.15.4 standard and evaluate its suitability to the medical environment. We focus on scalability issues using IEEE 802.11b. Keywords ­Medical Applications, ECG, WLAN, WPAN, Healthcare systems, performance

421

C-fuzzy variable-branch decision tree with storage and classification error rate constraints  

NASA Astrophysics Data System (ADS)

The C-fuzzy decision tree (CFDT), which is based on the fuzzy C-means algorithm, has recently been proposed. The CFDT is grown by selecting the nodes to be split according to its classification error rate. However, the CFDT design does not consider the classification time taken to classify the input vector. Thus, the CFDT can be improved. We propose a new C-fuzzy variable-branch decision tree (CFVBDT) with storage and classification error rate constraints. The design of the CFVBDT consists of two phases-growing and pruning. The CFVBDT is grown by selecting the nodes to be split according to the classification error rate and the classification time in the decision tree. Additionally, the pruning method selects the nodes to prune based on the storage requirement and the classification time of the CFVBDT. Furthermore, the number of branches of each internal node is variable in the CFVBDT. Experimental results indicate that the proposed CFVBDT outperforms the CFDT and other methods.

Yang, Shiueng-Bien

2009-10-01

422

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

PubMed Central

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

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

2014-01-01

423

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

PubMed

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

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

2013-04-01

424

National Lung Screening Trial: Variability in Nodule Detection Rates in Chest CT Studies  

PubMed Central

Purpose: To characterize the variability in radiologists’ interpretations of computed tomography (CT) studies in the National Lung Screening Trial (NLST) (including assessment of false-positive rates [FPRs] and sensitivity), to examine factors that contribute to variability, and to evaluate trade-offs between FPRs and sensitivity among different groups of radiologists. Materials and Methods: The HIPAA-compliant NLST was approved by the institutional review board at each screening center; all participants provided informed consent. NLST radiologists reported overall screening results, nodule-specific findings, and recommendations for diagnostic follow-up. A noncalcified nodule of 4 mm or larger constituted a positive screening result. The FPR was defined as the rate of positive screening examinations in participants without a cancer diagnosis within 1 year. Descriptive analyses and mixed-effects models were utilized. The average odds ratio (OR) for a false-positive result across all pairs of radiologists was used as a measure of variability. Results: One hundred twelve radiologists at 32 screening centers each interpreted 100 or more NLST CT studies, interpreting 72 160 of 75 126 total NLST CT studies in aggregate. The mean FPR for radiologists was 28.7% ± 13.7 (standard deviation), with a range of 3.8%–69.0%. The model yielded an average OR of 2.49 across all pairs of radiologists and an OR of 1.83 for pairs within the same screening center. Mean FPRs were similar for academic versus nonacademic centers (27.9% and 26.7%, respectively) and for centers inside (25.0%) versus outside (28.7%) the U.S. “histoplasmosis belt.” Aggregate sensitivity was 96.5% for radiologists with FPRs higher than the median (27.1%), compared with 91.9% for those with FPRs lower than the median (P = .02). Conclusion: There was substantial variability in radiologists’ FPRs. Higher FPRs were associated with modestly higher sensitivity. © RSNA, 2013 PMID:23592767

Pinsky, Paul F.; Gierada, David S.; Nath, P. Hrudaya; Kazerooni, Ella; Amorosa, Judith

2013-01-01

425

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

NASA Astrophysics Data System (ADS)

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

Chen, Su-ting

2009-07-01

426

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

427

Poincaré plot of heart rate variability allows quantitative display of parasympathetic nervous activity in humans.  

PubMed

1. Time domain summary statistics and frequency domain parameters can be used to measure heart rate variability. More recently, qualitative methods including the Poincaré plot have been used to evaluate heart rate variability. The aim of this study was to validate a novel method of quantitative analysis of the Poincaré plot using conventional statistical techniques. 2. Beat-to-beat heart rate variability was measured over a relatively short period of time (10-20 min) in 12 healthy subjects aged between 20 and 40 years (mean 30 +/- 7 years) during (i) supine rest, (ii) head-up tilt (sympathetic activation, parasympathetic nervous system activity withdrawal), (iii) intravenous infusion of atropine (parasympathetic nervous system activity withdrawal), and (iv) after overnight administration of low-dose transdermal scopolamine (parasympathetic nervous system augmentation). 3. The "width' of the Poincaré plot, as quantified by SD delta R-R (the difference between successive R-R intervals), was determined at rest (median 48.9, quartile range 20 ms) and found to be significantly reduced during tilt (median 19.1, quartile range 13.7 ms, P < 0.01) and atropine administration (median 7.1, quartile range 5.7 ms, P < 0.01) and increased by scopolamine (median 79.3, quartile range 33 ms, P < 0.01). Furthermore, log variance of delta R-R intervals correlated almost perfectly with log high-frequency (0.15-0.4 Hz) power (r = 0.99, P < 0.01). 4. These findings strongly suggest that the "width' of the Poincaré plot is a measure of parasympathetic nervous system activity. The Poincaré plot is therefore a quantitative visual tool which can be applied to the analysis of R-R interval data gathered over relatively short time periods. PMID:8795444

Kamen, P W; Krum, H; Tonkin, A M

1996-08-01

428

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

PubMed Central

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

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

2013-01-01

429

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

430

Not so fast! Talker variability in serial recall at standard presentation rates.  

PubMed

In serial recall tasks, presenting items in alternating female and male voices impairs performance relative to the single-voice presentation. This phenomenon, termed the talker-variability effect (TVE), was recently reexamined by Hughes, Marsh, and Jones (2009, 2011), who used the effect as confirmatory evidence for their perceptual-gestural account of serial recall performance. Despite the authors' claim of generalisability, the serial recall paradigm employed did not reflect the standard parameters more generally adopted in verbal short-term memory research. Specifically, the presentation rate of the stimuli was almost 3 times that typically used. We sought to determine if the TVE, as observed by Hughes et al., was generalisable to the standard serial recall task by directly comparing recall performance in talker-variable conditions at fast and slow stimulus presentation rates. Experiment 1 employed a systematic replication of the foundational study undertaken by Hughes et al. (2009). Utilising a novel stimulus set, Experiment 2 provided a subsequent test of the generalisability of the TVE, examining the influence of item properties. Both experiments showed a robust TVE at the atypical fast presentation rate; however, for the slower item presentation, the TVE was unreliable. Furthermore, error analysis suggests that item recall also contributes to the TVE, contrary to the current explanation proposed by Hughes et al. (2009, 2011). The challenge of the present data to the perceptual-gestural account of the TVE is explored. Alternative accounts that focus on the resource cost of categorical speech perception in the context of talker variability are posited. (PsycINFO Database Record (c) 2015 APA, all rights reserved). PMID:25730639

Mogensen, Claire; Miller, Leonie M; Roodenrys, Steven

2015-03-01

431

Temporal variability of transformation, formation, and subduction rates of upper Southern Ocean waters  

NASA Astrophysics Data System (ADS)

Kinematic and thermodynamic approaches are employed to diagnose the time-dependent transformation, formation, and subduction rates of upper Southern Ocean waters in a multidecadal simulation within an eddy-permitting coupled climate model. In the Subantarctic Mode Water (SAMW) density class, a convergence of diapycnal volume fluxes leads to the formation and inflation of mixed layer waters during winter. A portion of this water is detrained into the pycnocline during early spring, when surface heating restratifies the deep winter mixed layer. The annually averaged subduction rate of SAMW shows pronounced interannual variability, partly controlled by the temporal tendency of the winter mixed layer depth from one year to the next. No significant correlation between the Southern Annular Mode (SAM) and the isopycnally integrated SAMW subduction rate is apparent. However, Ekman downwelling/upwelling intensities modulated by the SAM influence interannual variations in the subduction rates of water masses lighter and heavier than SAMW with an opposing sign: during positive phases of the SAM, more pycnocline waters are entrained into the mixed layer and transformed into lighter densities within the Antarctic Intermediate Water density class, whereas more mixed layer waters are subducted into the pycnocline within the Subtropical Mode Water density class. Such distinct responses of upper Southern Ocean water masses to the SAM are qualitatively consistent with observational constraints. Based on a comparison between offline kinematic and thermodynamic diagnostics, we infer that diapycnal mixing within the mixed layer may contribute up to 50% of the formation rate of SAMW on interannual timescales.

Kwon, Eun Young

2013-11-01

432

Spectral analysis of heart rate and blood pressure variability in primary Sjogren's syndrome  

Microsoft Academic Search

BACKGROUND: Autonomic dysfunction has been described in primary Sjogren's\\u000a syndrome (SS). OBJECTIVE: To investigate the circulatory autonomic\\u000a regulation in patients with primary SS by power spectral analysis of heart\\u000a rate and blood pressure variability. METHODS: Forty three (42 female)\\u000a patients with primary SS, mean age 52 years (range 23-80), with a mean\\u000a disease duration of eight years (range 1-30) and

P. J. Barendregt; J. H. M. Tulen; Meiracker van den A. H; H. M. Markusse

2002-01-01

433

Ultrasonic Phased Arrays with Variable Geometric Focusing for Hyperthermia Applications.  

NASA Astrophysics Data System (ADS)

The objective of this research has been to investigate the characteristics and design of a variable-focus ultrasonic liquid-lens for use with a linear phased array in hyperthermia applications. The ultrasonic liquid lens adds a dynamic geometrical focusing capability, determined by the radius of curvature of the lens and speed of sound in the liquid, to the linear phased array. By controlling the volume of liquid in the lens (and thus the radius of curvature of its membrane), dynamic control of the geometrical focus can be achieved. Geometrical focusing reduces the focal spot size in the elevation dimension of the linear phased array thereby increasing its intensity gain, and allows fewer array elements to be used, for a given aperture size, while still maintaining grating lobe suppression. In this research, two ultrasonic liquid-lens transducers were fabricated and investigated. The first, a spherical liquid-lens with an unfocused square piezo-electric ceramic, was designed to determine the basic properties of a liquid -lens system. Several types of silicon oils and perfluorocarbons were examined for use in the lens of this transducer. The second was a linear phased array coupled to a spherical liquid lens. This system electronically focuses and scans the beam in the azimuthal direction by controlling the phase of each element in addition to the geometric focusing of the spherical lens. Theoretical simulations of field intensity profiles for both transducers compared well with the experimental measurements. A clinical prototype of a spherical liquid-lens phased array hyperthermia applicator was designed to maximize the volume of a tumor which can be preferentially heated with given constraints on the maximum applicator aperture size and maximum heating depth. The clinical potential of the applicator was assessed using predictions of temperature distributions in a tissue model. With three electronic foci mechanically scanned, up to a 60 -mm cubic tumor located at the depth of 165 mm from the transducer can be treated. The maximum treatment size of tumor can be increased by adding more electronic foci and changing the radius of curvature of the lens.

Yoon, Young Joong

434

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

PubMed

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

Hua, Pei; Vasyukova, Ekaterina; Uhl, Wolfgang

2015-05-15

435

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

Federal Register 2010, 2011, 2012, 2013, 2014

...permit open-end management investment companies relying...Variable Insurance Portfolios (the ``Trust''), Waddell & Reed Investment Management Company (``WRIMCO...Applicants' Legal Analysis 1. Section...

2013-03-22

436

Considerations in the assessment of heart rate variability in biobehavioral research  

PubMed Central

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

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

2014-01-01

437

A new algorithm for wavelet-based heart rate variability analysis  

E-print Network

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

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

2014-01-01

438

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

PubMed Central

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

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

2012-01-01

439

Depression and heart rate variability in patients with coronary heart disease  

PubMed Central

Depression is common in patients with coronary heart disease (CHD) and is a risk factor for cardiac morbidity and mortality in these patients. Depression is associated with autonomic nervous system dysfunction, which may at least partially explain this increased risk. Low heart rate variability (HRV), which reflects excessive sympathetic and/or inadequate parasympathetic modulation of heart rate, is a strong predictor of mortality in patients with CHD. Most studies—both in patients with stable CHD and in patients with a recent acute coronary event—have found HRV to be lower in depressed patients than in their nondepressed counterparts. This manuscript provides an overview of this literature and concludes that HRV may account for a substantial part of the risk associated with depression in CHD. PMID:19376975

CARNEY, ROBERT M.; FREEDLAND, KENNETH E.

2012-01-01

440

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

PubMed Central

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

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

2012-01-01

441

Financial applications of a Tabu search variable selection model  

Microsoft Academic Search

We illustrate how a comparatively new technique, a Tabu search variable selection model (Drezner, Marcoulides and Salhi (1999)), can be applied eciently within finance when the researcher must select a subset of variables from among the whole set of explanatory variables under consideration. Several types of problems in finance, including corporate and personal bankruptcy prediction, mortgage and credit scoring, and

Zvi Drezner; George A. Marcoulides; Mark Hoven Stohs

2001-01-01

442

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

NASA Astrophysics Data System (ADS)

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

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

443

Variable-Temperature Rate Coefficients of Proton-Transfer Equilibrium Reaction C2H4 + H3O+  

E-print Network

Variable-Temperature Rate Coefficients of Proton-Transfer Equilibrium Reaction C2H4 + H3O+ C2H5 the observed rate coefficients, a new type of reaction temperature was defined in these studies that considered rate coefficients of this reaction, with molecular beam and ion temperatures varied independently from

Sanov, Andrei

444

Application of semiclassical methods to reaction rate theory  

SciTech Connect

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

Hernandez, R.

1993-11-01

445

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. PMID:22291638

Migliorini, Matteo; Mendez, Martin O.; Bianchi, Anna M.

2012-01-01

446

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

PubMed

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

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

2015-04-30

447

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

PubMed

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

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

2015-01-01

448

The Forgotten Role of Central Volume in Low Frequency Oscillations of Heart Rate Variability  

PubMed Central

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

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

2015-01-01

449

Sleep Quality Estimation based on Chaos Analysis for Heart Rate Variability  

NASA Astrophysics Data System (ADS)

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

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

450

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

451

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. PMID:23840888

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

2013-01-01

452

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

PubMed

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

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

2013-01-01