Frequency Domain Spectral Analysis Research Articles

Experimental Study of the Hydrodynamic Characteristics of a Submerged Floating Tunnel under Freak Wave (II: Time-Frequency Domain Study)

A freak wave is a spike in a random wave series and hence the local characteristics in the time-domain are of key importance. When freak waves act on moored floating structures, the dynamic responses of the structures in the time and frequency domains change interdependently in a short period of time. It is difficult to comprehensively and accurately describe this physical process using a single-dimensional analysis method, such as time-domain statistical analysis or frequency-domain spectral analysis. The wavelet analysis method, which can simultaneously provide the time-domain and frequency-domain joint information of the physical process, is used to discuss the time-frequency joint variation characteristics of the dynamic responses of a two-dimensional submerged floating tunnel under a freak wave. The time-frequency characteristics of the dynamic responses induced by the freak wave and the differences from the action under random waves are investigated, with a particular emphasis on the ‘convex variation’ characteristics of the dynamic responses under a freak wave. The results show that: (1) The wavelet analysis method can effectively describe the basic characteristics of the dynamic responses of the SFT under a freak wave and clearly distinguish the differences in dynamic responses under freak and random waves. (2) Freak waves have dynamic amplification effects, which are related to the freak wave parameter α1, on a two-dimensional SFT. Following the action of freak waves on a two-dimensional SFT, significant energy concentration occurs in the time-frequency spectrum of the dynamic response in a certain time and frequency range. The degree of energy concentration increases nonlinearly with an increase in α1, and a certain high-frequency energy appears in the time-frequency spectrum of the motion response. The maximum values of the time-frequency spectra of the dynamic responses under a freak wave are much larger than those under a random wave with the identical wave spectrum. (3) Following the action of a freak wave on a two-dimensional SFT, the generalised energy spectra of surge, heave, pitch, and mooring tensions have convex peak values, which occur simultaneous with the occurrence of the freak wave, and the convex parts significantly increase as α1. (4) The time lengths of the influence of a freak wave on the dynamic responses exceeded the freak wave period. With an increase in α1, the time ranges of the large values of the time-frequency spectra of surge, heave, pitch, and mooring tensions increase nearly linearly.

Multi-window spectrum analysis of Búzios oil field PSDM seismic data applied to frequency attenuation study

The intrinsic attenuation is often quantified using the inverse quality factor Q. Methods to estimate Q are mainly based on time domain or frequency domain and sensitive to amplitude and/or frequency band variations. In this sense, noise, signal artifacts or processing steps can alter the amplitude, frequency content and the waveform, what may lead to inaccurate calculations of Q. A way to better understand the frequency band variation in seismic data and verify patterns or problems occurring in the signal frequency band is performing layered or window-by-window spectrum analysis. This work describes a multi-window spectrum analysis method used to better understand the frequency attenuation process as the seismic wave travels through the sediments from the sea bottom down to the reservoir depths in a 3D Kirchhoff Pre-Stack Depth Migrated (PSDM) seismic data from Búzios oil field. To perform the spectral analysis in frequency domain, the PSDM volume was converted to time domain using the same interval velocity volume used to depth-migrate the data. The variation of frequency band as the signal propagates through the sediment package was analyzed dividing the studied crossline sections in 13 layers of 200 ms each, from sea bottom down to the base of pre-salt reservoir formations. The results suggest that most part of higher frequency loss has been occurred in post-salt package. This may be an indication of significant viscoelastic behavior or strong stratigraphic filtering of this interval. Sequentially, higher frequency content is lost slowly from salt top down to the last layer located inside pre-salt formation. Very slight frequency spectrum variation below salt top indicates elastic behavior of the salt formation and underling pre-salt formation in this interval. The spectrum analysis method proposed here has shown to be useful and efficient to identify intervals of different attenuation patterns in seismic data. Additionally, the frequency band study produced by our spectrum analysis can be used to quality-control Q-factor estimation computed by different methods.

Honeybee Brain Oscillations Are Generated by Microtubules. The Concept of a Brain Central Oscillator.

Microtubules (MTs) are important structures of the cytoskeleton in neurons. Mammalian brain MTs act as biomolecular transistors that generate highly synchronous electrical oscillations. However, their role in brain function is largely unknown. To gain insight into the MT electrical oscillatory activity of the brain, we turned to the honeybee (Apis mellifera) as a useful model to isolate brains and MTs. The patch clamp technique was applied to MT sheets of purified honeybee brain MTs. High resistance seal patches showed electrical oscillations that linearly depended on the holding potential between ± 200 mV and had an average conductance in the order of ~9 nS. To place these oscillations in the context of the brain, we also explored local field potential (LFP) recordings from the Triton X-permeabilized whole honeybee brain unmasking spontaneous oscillations after but not before tissue permeabilization. Frequency domain spectral analysis of time records indicated at least two major peaks at approximately ~38 Hz and ~93 Hz in both preparations. The present data provide evidence that MT electrical oscillations are a novel signaling mechanism implicated in brain wave activity observed in the insect brain.

SpikeOnChip : A Custom Embedded Platform for Neuronal Activity Recording and Analysis.

In this paper we present SpikeOnChip, a custom embedded platform for neuronal activity recording and online analysis. The SpikeOnChip platform was developed in the context of automated drug testing and toxicology assessments on neural tissue made from human induced pluripotent stem cells. The system was developed with the following goals: to be small, autonomous and low power, to handle micro-electrode arrays with up to 256 electrodes, to reduce the amount of data generated from the recording, to be able to do computation during acquisition, and to be customizable. This led to the choice of a Field Programmable Gate Array System-On-Chip platform. This paper focuses on the embedded system for acquisition and processing with key features being the ability to record electrophysiological signals from multiple electrodes, detect biological activity on all channels online for recording, and do frequency domain spectral energy analysis online on all channels during acquisition. Development methodologies are also presented. The platform is finally illustrated in a concrete experiment with bicuculline being administered to grown human neural tissue through microfluidics, resulting in measurable effects in the spike recordings and activity. The presented platform provides a valuable new experimental instrument that can be further extended thanks to the programmable hardware and software.

EXPLORATORY SPECTRAL ANALYSIS IN THREE-DIMENSIONAL SPATIAL POINT PATTERNS

A spatial point pattern is a collection of points irregularly located within a bounded area (2D) or space (3D) that have been generated by some form of stochastic mechanism. Examples of point patterns include locations of trees in a forest, of cases of a disease in a region, or of particles in a microscopic section of a composite material. Spatial Point pattern analysis is used mostly to determine the absence (completely spatial randomness) or presence (regularity and clustering) of spatial dependence structure of the locations. Methods based on the space domain are widely used for this purpose, while methods conducted in the frequency domain (spectral analysis) are still unknown to most researchers. Spectral analysis is a powerful tool to investigate spatial point patterns, since it does not assume any structural characteristics of the data (ex. isotropy), and uses only the autocovariance function, and its Fourier transform. There are some methods based on the spectral frameworks for analyzing 2D spatial point patterns. There is no such methods available for the 3D situation and, therefore, the aim of this work is to develop new methods based on spectral framework for the analysis of three-dimensional point patterns. The emphasis is on relating periodogram structure to the type of stochastic process which could have generated a 3D observed pattern. The results show that the methods based on spectral analysis developed in this work are able to identify patterns of three typical three-dimensional point processes, and can be used, concurrently, with analyzes in the space domain for a better characterization of spatial point patterns.

Association of Postural Instability with Autonomic Dysfunction in Early Parkinson’s Disease

Background: There have been several pathologic data that support an association between postural instability (PI) and autonomic dysfunction in Parkinson’s disease (PD). The purpose of this study was to investigate the correlation of PI and autonomic deficits in early PD. Methods: We collected 17 patients with a diagnosis of early PD. PI was assessed by computerized dynamic posturography (CDP). Standardized autonomic function test (AFT) and time and frequency domain spectral analysis of heart rate variability (HRV) were performed. CDP data obtained from the 21 patients were compared to that from age- and sex-matched healthy controls. We collected HRV data from 18 other age- and sex-matched controls. All patients were evaluated in the “OFF” state. We used Mann–Whitney U-test to compare parameters of CDP between the early PD and control groups. Spearman correlation was used for correlation analysis between parameters of CDP and autonomic function test in PD patients. Results: Most patients (76.5%) showed mild or moderate autonomic dysfunction in the standardized AFT. In CDP, sensory ratios of equilibrium score (e.g., visual and vestibular) and composite scores were significantly lower in PD patients than in controls. In HRV, the low-frequency/high-frequency ratio during the tilt and the gap of low- frequency/high-frequency ratio from supine to tilt were significantly different in both groups. The parameters of time and frequency domains of HRV reflecting parasympathetic function were correlated with equilibrium scores for somatosensory organization test in CDP. Discussion: PI was associated with parasympathetic autonomic dysfunction in early PD. This result was in accordance with a previous assumption that PI in PD is related to parasympathetic cholinergic neuron loss in the brainstem.

Heart rate variability as a potential diagnostic tool to predict compensatory hyperhidrosis after sympathectomy in patients with primary focal hyperhidrosis.

BackgroundPrimary focal hyperhidrosis (PFH) is associated with autonomic nervous activity, and studies investigating this association in patients with PFH are very important. Heart rate variability (HRV) is a simple and noninvasive electrocardiographic test showing activity and balance in the autonomic nervous system, which consists of sympathetic and parasympathetic components. The aims of this study are to investigate associations between autonomic nervous activity and hyperhidrosis characteristics using HRV and to investigate the association between HRV findings and compensatory hyperhidrosis (CH) after sympathectomy.MethodsFrom March 2017 to March 2020, 105 subjects with PFH who underwent preoperative HRV tests and sympathectomy were analyzed. All subjects underwent bilateral thoracoscopic sympathectomy. T2 sympathectomy was conducted for craniofacial hyperhidrosis, and T3 sympathectomy was conducted for palmar hyperhidrosis. The following HRV parameters chosen to investigate the association between hyperhidrosis and autonomic nervous activity were measured by time and frequency domain spectral analysis: (I) time domain: standard deviation of normal-to-normal interval (SDNN) and square root of mean squared differences of successive normal-to-normal intervals (RMSSD), (II) frequency domain: total power (TP) of power spectral density, very low frequency (VLF), low frequency (LF), and high frequency (HF). HRV parameters were analyzed according to hyperhidrosis type (craniofacial vs. palmar type), sweat reduction, and CH after sympathectomy. In addition, the independent HRV parameters influencing CH after sympathectomy were investigated with multivariate analysis.ResultsCraniofacial hyperhidrosis was significantly more prevalent in the old age group (P<0.001). Sweat reduction after sympathectomy was significantly more prominent in palmar hyperhidrosis (P=0.037), and CH after sympathectomy was more prominent in craniofacial hyperhidrosis (P<0.001). Palmar type patients exhibited significantly larger SDNN, RMSSD, TP, LF, and HF than craniofacial type patients (all P<0.001). There were no significant differences in any HRV parameters according to sweat reduction after sympathectomy. Low-degree CH was associated with significantly larger SDNN, RMSSD, TP, LF, and HF than high-degree CH (P<0.001, P<0.001, P=0.002, P=0.001, and P<0.001, respectively). Multivariate analysis showed that HF and age group were associated with CH after sympathectomy (P=0.007 and P=0.010, respectively).ConclusionsThis study shows that HRV can provide useful insight into the pathophysiology of PFH and enhance preoperative risk stratification of CH. Large-scale, prospective studies are required to determine the predictive value of HRV in patients at risk for subsequent CH after sympathectomy.

Frequency Dependent Damage Pattern in Kathmandu Valley Due to Mw 7.8 Gorkha Earthquake

The Mw 7.8 Gorkha Earthquake (25th April 2015) is powerful earthquake ripped through Central Nepal occurs about 77 Km northwest of Kathmandu Valley. Several studies reveal the fact that comparatively larger earthquake damage in the Kathmandu valley are associated with the valley ground structure. Study focus on reason behind clustering of damages due to mainshock (7.8 Mw) inside Kathmandu valley in certain pattern and its dependency with frequency content of the shattered waves. Data used to meet objective of present research are ground motion data and damage data, for ground motion data seismic stations inside the valley are use. The damage data are collected by both primary and secondary sources. Frequency domain spectral analysis is incorporated in research and found that the maximum power and amplitude, associated, and attributed for particular narrow frequency band. Spatial component of frequency is wavelength which may indicate periodic repetition of maximum power with crest and trough. To estimate spatial distribution of maximum amplitude simplified wave relation is used. Study reveals that the lateral extension of the peak destruction zone as fourth of wavelength and the successive distance between peak destruction zones is half of wavelength. Peak destruction zone, the zone where the damage is maximum and lies either on crest or trough of the propagated wave. Study reveals that propagation of waves is S45oE form the epicenter of Gorkha Earthquake. Heterogeneity in damage on peak destruction zone can be contributed by the variation in geology of Kathmandu Valley.

Government Expenditure and Economic Growth Nexus in Mena Countries: Frequency Domain Spectral Causality Analysis

Abstract The paper aims at examining the causal relationship between economic growth and government expenditure in selected MENA countries over the period of 1987–2017. Unlike previous studies, we examine the causality in both panel data and time series data to get a clear idea about the causal relationships individually and as a full sample. We also revisited the causal relationship between the two variables within the framework of frequency domain causality. Our findings support the neutrality hypotheses in the short-run term for most of the countries. Thus, economic growth and government expenditure at most frequency levels evolve independently. On the other hand, we found the support of Wagner’s law, Keynes view, neutrality and bidirectional hypotheses in the long term.

주택자산과 인플레이션의 관계분석

This study examined the hedging effect of real estate assets against inflation through spectral analysis in frequency domain in addition to the commonly employed time series methodologies in time domain. Using the generalized Fisher hypothesis suggested by Fama and Schwertz, we estimated both expected and unexpected inflation rates and then analyzed the relationship between inflation and housing assets. We found that there was a statistically significant relationship between housing assets and inflation. In additional analysis, however, stock price was not found to have a significant impact on house prices. We also looked at the long-term relationship between house prices and inflation by conducting Johansen cointegration tests. The result showed that there was a long-term equilibrium relationship between house prices and inflation. The result of spectral analysis in frequency domain confirmed that there is a long-term relationship between inflation and house prices which follow a similar cycle in close relations with both leading and lagging indicators. We can say that the result provides a strong empirical evidence that supports the hedging effect of real estate assets against inflation that was found through time series analysis in time domain.

Aminophylline-associated irritable behaviour in preterm neonates

AimThis study investigated the effect of aminophylline on behaviour and autonomic function in the preterm period. MethodSubjects were preterm infants cared for in the Oita University hospital from August 2012 to October 2014. The group that was administered aminophylline (Am+) and the group that received no aminophylline (Am−) included 11 cases that exhibited a mean gestational age of 28weeks 5days and a mean birth weight of 1109g and 8 cases that exhibited a mean gestational age of 30weeks 5days and a mean birth weight of 1223g, respectively. Intravenous aminophylline was administered continuously at a dose of 4–6mg/kg/day followed by oral therapy when the infant suffered repetitive apnoea.Two-hour video recordings were obtained every 2weeks, and electrocardiograms were performed simultaneously. Onset-offset and tremulous movements in general movement (GM) optimality list were used as indices of behaviour. Autonomic functions were investigated via heart-rate and heart-rate variability measurements using frequency domain spectral analysis and the MemCalc method. We compared indices in 4 periods: 30–31, 32–33, 34–35 and 36–37weeks gestation. ResultsThe Am+ group exhibited significantly low optimality of tremulous movements at 32–33weeks gestation. The autonomic parameters did not differ significantly between the Am+ and Am− groups. There was no significant correlation between GMs optimality score and serum theophylline concentration. ConclusionAminophylline administration was associated with transient irritable behaviour without autonomic changes in the preterm period.

Dynamics of two-layer smart composite Timoshenko beams: Frequency domain spectral element analysis

Ultrasonic guided waves in a laminated composite structure can be excited or measured using piezoelectric transducers (PZTs). In this study, we propose a spectral element model for two-layer smart composite Timoshenko beams that consist of a host composite beam and a PZT layer. Contrary to the previous study (2012) where the Bernoulli-Euler beam theory was applied to the host composite beam, the Timoshenko beam theory and the Mindlin-Herrmann rod theory were applied in this study. The proposed spectral element model was evaluated first by comparison with standard finite element analyses, and it was then used to investigate the guided waves in some laminated composite beams.

Building energy consumption on-line forecasting using physics based system identification

Model based control has become a promising solution for building operation optimization and energy saving. Accuracy and computationally efficiency are two of the most important requirements for building energy models. Existing studies in this area have mostly been focusing on reducing computation burden using simplified physics based modeling approach. However, creating even the simplified physics based model is often challenging and time consuming. Pure date-driven statistical models have also been adopted in a lot of studies. Such models, unfortunately, often require long training period and are bounded to building operating conditions that they are trained for. Therefore, this study proposes a novel methodology to develop building energy estimation models for on-line building control and optimization using a system identification approach. Frequency domain spectral density analysis is implemented in this on-line modeling approach to capture the dynamics of building energy system and forecast the energy consumption with more than 90% accuracy and less than 2min computational speed. A systematic analysis of system structure, system order and system excitation selection are also demonstrated. The forecasting results from this proposed model are validated against detailed physics based simulation results using a mid-size commercial building EnergyPlus model.

Poor Autonomic Nervous System Functioning During Sleep in Recently Detoxified Alcohol‐Dependent Men and Women

Alcoholism is considered an important risk factor for cardiovascular (CV) disease. Autonomic nervous system (ANS) function is a major indicator of CV health. Sleep is a suitable model to investigate ANS activity free from wake-related confounders. We investigated nighttime ANS functioning, and the relation between ANS activity and severity of alcohol dependence in chronic alcoholism. Fourteen recently abstaining alcoholics (age: 42.0 ± 9.0 years, 7 women) and 16 age- and sex-matched controls (age: 45.2 ± 9.1 years, 8 women) underwent a night of standard clinical polysomnography, including electrocardiographic recording. Time- and frequency-domain spectral analysis of heart rate variability (HRV) was performed across hours of the night and during artifact-free epochs of stable sleep and wakefulness (presleep wakefulness, rapid-eye-movement [REM], and non-REM sleep). Alcoholics had a poorer subjective and objective sleep quality compared to controls. Across the night, alcoholic men and women had elevated heart rate, reduced total HRV, that is, lower standard deviation of normal-to-normal interbeat intervals, and reduced high frequency (HF) activity (assessed by the HF power and by the square root of the mean squared of successive heart period differences). This ANS pattern was most apparent at the beginning of the night. None of the ANS measures was associated with lifetime alcohol consumption or duration of alcohol dependence. Our results show that ANS functioning is disrupted during the night, even in undisturbed sleep periods, indicating poor CV functioning in recently detoxified alcohol-dependent men and women.

Guided waves in a Timoshenko beam with a bonded composite patch: Frequency domain spectral element modeling and analysis

Simulation of ultrasonic guided waves in a beam-type structure with a bonded composite patch repair requires a proven modeling and analysis technique that can provide accurate dynamic solutions at a high frequency range. We developed a spectral element model for a metallic beam with a bonded composite patch by using the variational method. To that end, the governing equations of motion are derived by adopting Timoshenko beam theory for the transverse bending motion, and Mindlin–Herrmann rod theory for the longitudinal motion of the composite patched beam to take into account the effects of lateral contraction in the thickness direction. The high accuracy of the spectral element model is then evaluated by comparison with the solutions obtained by the conventional finite element method (FEM) and by the commercial finite element (FE) analysis package ANSYS. By using the spectral element model, the effects of the composite patch on the characteristics of guided waves are numerically investigated. In addition, the effects of debonding are also numerically investigated with respect to monitoring the integrity of the bonded composite patch repair.

Transverse Vibration and Waves in a Membrane: Frequency Domain Spectral Element Modeling and Analysis

Although the spectral element method (SEM) has been well recognized as an exact continuum element method, its application has been limited mostly to one-dimensional (1D) structures, or plates that can be transformed into 1D-like problems by assuming the displacements in one direction of the plate in terms of known functions. We propose a spectral element model for the transverse vibration of a finite membrane subjected to arbitrary boundary conditions. The proposed model is developed by using the boundary splitting method and the waveguide FEM-based spectral super element method in combination. The performance of the proposed spectral element model is numerically validated by comparison with exact solutions and solutions using the standard finite element method (FEM).

Non-stationary frequency response function

Using the Duhamel’s integral concept, a non-stationary frequency response function (complete-FRF) for the dynamic response of a single degree of freedom system initially at rest has been developed. Although the procedure is devised to be applied in the frequency domain, this new function is time dependent and can be employed to calculate the transient response of a system in a forced vibration case. The method has been successfully checked with two different cases of loading in the time domain which have either analytical solution or accurate numerical solution using Newmark’s algorithm. The method has been compared with the solution obtained from the commonly used steady frequency response function, and a detailed analysis of the four parameters that appear in the complete-FRF function: time, damping ratio, natural period and input frequency is presented. Finally, the proposed non-steady FRF has been applied to the calculation of an elastic displacement response spectrum to confirm the great influence of the natural period of the system and the frequency content of the solicitation in frequency-domain spectral analysis.

Abstract 498: Increased Blood Pressure Variability and Baroreflex Impairment in Patients With End-stage Renal Disease Undergoing Hemodialysis

Background: Patients with end-stage renal disease (ESRD) undergoing hemodialysis are susceptible to the development of autonomic dysfunction, which is associated with an increased risk of sudden death. Experimental and clinical evidence suggest a crucial role of autonomic dysfunction for both, the progression of renal disease and for the high rate of cardiovascular events in these patients. In the present study, we evaluated the heart rate variability (HRV), the blood pressure variability (BPV) and the baroreflex sensitivity (BRS) in ESRD patients undergoing hemodialysis and normal controls. Methods: Nine ESRD patients undergoing hemodialysis (mean age 53.4±10.2 years, 4 male) and nine age-matched healthy controls (mean age 52.8±10.2 years, 4 male) were assessed. Non−invasive curves of blood pressure (BP) were recorded continuously (Finometer ®) for 10 minutes, at rest, in the supine position. The heart rate variability (HRV) and systolic blood pressure variability (BPV) were estimated in the time and frequency domain (spectral analysis). The BRS was quantified by alpha index. Statistical analyzes were performed by Student's t test and the results were expressed as mean ± standard deviation. Results: ESRD patients presented lower HRV in time domain than healthy controls (SDNN: 25.8±10.7 vs. 44.6±11.7 ms, p&lt;0.01; VAR NN: 768.3±607.4 vs. 2113.9±1261.6 ms 2 , p=0.01). All frequency domain analyzed indexes, i.e., total power (361.9±297.0 vs. 1227.2±696.3 ms 2 , p&lt;0.01), high-frequency (181.8±128.7 vs. 358.7±179.8 ms 2 , p=0.047), low-frequency (55.1±44.2 vs. 444.6±389.9 ms 2 , p=0.02) and very-low-frequency (72.5±75.1 vs. 279.2±119.5 ms 2 , p&lt;0.01) of HRV were lower in ESRD patients. The BPV was higher in ESRD patients when compared to controls (VAR PAS: 98.4±72.0 vs. 35.4±21.4 ms 2 , p=0.03) and BRS was lower in ESRD patients (alpha index: 4.34±3.05 vs. 7.56±2.50 ms/mmHg, p&lt;0.02). Conclusion: ESRD patients undergoing hemodialysis presents reduced HRV, increase in BPV and reduced baroreflex sensitivity. These impairments may be associated with mortality in ESRD.

Heart Rate Variability in Children with Tricyclic Antidepressant Intoxication

The aim of this study was to evaluate HRV in children requiring intensive care unit stays due to TCA poisoning between March 2009 and July 2010. In the time-domain nonspectral evaluation, the SDNN (P < 0.001), SDNNi (P < 0.05), RMSDD (P < 0.01), and pNN50 (P < 0.01) were found to be significantly lower in the TCA intoxication group. The spectral analysis of the data recorded during the first 5 minutes after intensive care unit admission showed that the values of the nLF (P < 0.05) and the LF/HF ratio (P = 0.001) were significantly higher in the TCA intoxication group, while the nHF (P = 0.001) values were significantly lower. The frequency-domain spectral analysis of the data recorded during the last 5 minutes showed a lower nHF (P = 0.001) in the TCA intoxication group than in the controls, and the LF/HF ratio was significantly higher (P < 0.05) in the intoxication group. The LF/HF ratio was higher in the seven children with seizures (P < 0.001). These findings provided us with a starting point for the value of HRV analysis in determining the risk of arrhythmia and convulsion in TCA poisoning patients. HRV can be used as a noninvasive testing method in determining the treatment and prognosis of TCA poisoning patients.

노인의 식후 저혈압과 심박동변이

Purpose: A study was designed to compare heart rate variability (HVR) of older adults with postprandial hypotension (PPH) with older adults with no PPH. Methods: The samples were community-dwelling older adults (≥ 60 years old) with PPH (n=35) and without PPH (n=35). HRV was measured by 10 minutes of electrocardiography using Physiolab 400 and analyzed in time domain (SDNN) and with power spectral analysis in frequency domain (TP, LF, HF, LF/HF). Blood pressure was measured every 15 minutes before and until 120 minutes after the meal. Results: All HRV parameters were lower in the PPH group compared to those with no PPH. Specifically the measures of SDNN, TP, LF, and LF/HF of the PPH group were significantly lower (U=385.0, p=.008; U=361.0, p=.003; U=375.0, p=.005; U=368.0, p=.004, respectively). Further, the LF and LF/HF of SBP (≥140 mmHg) group and the LF/HF of DBP (≥ 90 mmHg) group were significantly lower (x 2 =6.33, p=.042; x 2 =33.10, p<.001; x 2 =11.03, p=.004, respectively). Conclusion: These findings indicate that the autonomic nervous functions in persons with PPH are less activated than those persons with no PPH. The findings contribute to an understanding of HRV and the association of autonomic nervous function with the mechanism of PPH.