Low-frequency Spectral Components Research Articles

Acoustic detection of drone range and type using nonuniform band energy features

With increased use of drones in a variety of situations, it is imperative that efficient means of detecting the type of unmanned aerial vehicle and/or its range are developed from security, privacy, and safety perspective. This paper describes the application of an acoustic feature set in a deep learning network for the estimation of the line-of-sight range of drones. The set of spectral energy values over nonuniform bands within the range of audio recordings of open space drone noise has been shown to predict the range to a reasonable degree of accuracy. The energy feature set, when augmented with low frequency spectral components, raised prediction accuracy to within 85 cm of mean error and a standard deviation of 12 m for test cases ranging from 10 m to 935 m. Additionally, the spectral band energy applied to classify the range quantized into 1 m intervals resulted in better than 87% accuracy with a fixed error of ±50 cm over the entire range. Adding low frequency spectral components to the band energy set raised the correct range classification to 97%. For classification of seven tethered drones, the band energy feature set resulted in 99.9% accuracy.

Classification of Rhythmic Cortical Activity Elicited by Whole-Body Balance Perturbations Suggests the Cortical Representation of Direction-Specific Changes in Postural Stability.

Postural responses that effectively recover balance following unexpected postural changes need to be tailored to the characteristics of the postural change. We hypothesized that cortical dynamics involved in top-down regulation of postural responses carry information about directional postural changes (i.e., sway) imposed by sudden perturbations to standing balance (i.e., support surface translations). To test our hypothesis, we evaluated the single-trial classification of perturbation-induced directional changes in postural stability from high-density EEG. We analyzed EEG recordings from six young able-bodied individuals and three older individuals with chronic hemiparetic stroke, which were acquired while individuals reacted to low-intensity balance perturbations. Using common spatial patterns for feature extraction and linear discriminant analysis or support vector machines for classification, we achieved classification accuracies above random level (p < 0.05; cross-validated) for the classification of four different sway directions (one vs. the rest scheme). Screening of spectral features (3-50 Hz) revealed that the highest classification performance occurred when low-frequency (3-10 Hz) spectral features were used. Strikingly, the participant-specific classification results were qualitatively similar between young able-bodied individuals and older individuals with chronic hemiparetic stroke. Our findings demonstrate that low-frequency spectral components, corresponding to the cortical theta rhythm, carry direction-specific information about changes in postural stability. Our work presents a new perspective on the cortical representation of postural stability and the possible role of the theta rhythm in the modulation of (directional) reactive balance responses. Importantly, our work provides preliminary evidence that the cortical encoding of direction-specific changes in postural stability is present in chronic hemiparetic stroke.

Daily Heart Rate Variability Indices in Subjects with and Without Metabolic Syndrome Before and After the Elimination of the Influence of Day-Time Physical Activity.

Background and Objectives: The available research shows conflicting data on the heart rate variability (HRV) in metabolic syndrome (MetS) subjects. The discrepancy suggests a methodical shortcoming: due to the influence of physical activity, the standard measuring of HRV at rest is not comparable with HRV assessment based on 24 h Holter monitoring, which is preferred because of its comprehensiveness. To obtain a more reliable measure and to clarify to what extent HRV is altered in MetS, we assessed a 24 h HRV before and after the elimination of the influence of physical activity. Materials and Methods: We investigated 69 metabolic syndrome (MetS) and 37 control subjects, aged 50–55. In all subjects, 24 h monitoring of electrocardiogram, blood pressure, and actigraphy profiles were conducted. To eliminate the influence of day-time physical activity on RR intervals (RRI), a linear polynomial autoregressive model with exogenous terms (ARX) was used. Standard spectral RRI analysis was performed. Results: Subjects with MetS had blunted HRV; the diurnal SDNN index was reliably lower in the MetS group than in control subjects. The elimination of the influence of physical activity did not reveal a significant HRV change in long-term indices (SDNN, SDANN, and SD2), whilst adjacent RRI values (RMSSD, pNN50, and SD1) and SDNN index significantly increased (p < 0.001). An increase in the latter indices highlighted the HRV difference between the MetS and control groups; a significant (p < 0.001) decrease of all short-term HRV variables was found in the MetS group (p < 0.01), and low-frequency spectral components were less pronounced in the MetS group. Conclusion: The application of a polynomial autoregressive model in 24 h HRV assessment allowed for the exclusion of the influence of physical activity and revealed that MetS is associated with blunted HRV, which reflects mitigated parasympathetic tone.

Usefulness of cardiac parasympathetic index in CPAP-treated patients with obstructive sleep apnea: A preliminary study.

Cardiac autonomic indexes, including cardiac parasympathetic index and cardiac sympathetic index, have been reported to accurately identify patients with sleep disorders such as obstructive sleep apnea. Our study aimed to assess cardiac autonomic indexes in patients with obstructive sleep apnea before and during a single full-night continuous positive airway pressure therapy using a combined approach. Our simultaneous heart rate variability-polysomnographic study included 16 never-treated obstructive sleep apnea patients. Two patients dropped out. Patients underwent combined recordings in two consecutive days, at baseline and during a single full-night of acute continuous positive airway pressure treatment. We calculated cardiac parasympathetic index and cardiac sympathetic index as night/day ratio for high-frequency and low-frequency heart rate variability spectral components, respectively. Continuous positive airway pressure treatment significantly reduced cardiac autonomic indexes values in comparison with baseline values (cardiac parasympathetic index: p<.0001; cardiac sympathetic index: p=.001). After acute continuous positive airway pressure treatment, the percentage of decrease of cardiac parasympathetic index was greater than that of cardiac sympathetic index (51.02±15.72 versus 34.64±26.93). A positive statistical correlation was also found between decrease of cardiac parasympathetic index and decrease of apnea-hypopnea index after continuous positive airway pressure (p<.001). This study improves the knowledge on cardiac autonomic modulation during acute continuous positive airway pressure therapy in obstructive sleep apnea. Our results demonstrate that both autonomic indexes decreased significantly after a single-night of acute continuous positive airway pressure therapy. Cardiac parasympathetic index more than cardiac sympathetic index was related to decrease of apnea-hypopnea index after continuous positive airway pressure therapy, thus representing a potential help in everyday clinical practice.

Predation and Crypsis in the Evolution of Electric Signaling in Weakly Electric Fishes

Eavesdropping by electroreceptive predators poses a conflict for weakly electric fish, which depend on their Electric Organ Discharge (EOD) signals both for navigation and communication in the dark. The EODs that allow weakly electric fish to electrolocate and communicate in the dark may attract electroreceptive predators such as catfishes and Electric Eels. These predators share with their prey the synapomorphy of passive electric sense supported by ampullary electroreceptors that are highly sensitive to low-frequency electric fields. Any low-frequency spectral components of the EOD make weakly electric fish conspicuous and vulnerable to attack from electroreceptive predators. Accordingly, most weakly electric fish shift spectral energy upwards or cloak low-frequency energy with compensatory masking signals. Subadults and females in particular emit virtually no low-frequency energy in their EODs, whereas courting males include a significant low-frequency component, which likely attracts females, but makes the signals conspicuous to predators. Males of species that coexist with the most predators tend to produce the least low-frequency signal energy, expressing sexual dimorphism in their signals in less risky ways. In these respects, electric signals follow the classic responses to opposing forces of natural and sexual selection, as exemplified in the visual signals of guppies and the acoustic signals of Tungara frogs. Unique to electric fish is that the electric signal modifications that help elude detection by electroreceptive predators are additions to the basal signal rather than losses of attractive components. These enhancements that enable crypsis are energetically costly, but have also provided the evolutionary substrates for subsequent sexual selection and species identity characters.

Features of the Supersonic Gravity Wave Penetration from the Earth’s Surface to the Upper Atmosphere

Using a high-resolution numerical model, we simulate the gravity wave (GW) modes having supersonic horizontal phase velocities on the Earth’s surface and propagating to the upper atmosphere. Such GWs can be produced, for example, by low-frequency spectral components of the seismic waves propagating over the Earth’s crust surface with horizontal velocities of up to a few kilometers per second. According to the linear theory, GW modes with so high horizontal velocities should be trapped, with their amplitudes exponentially decreasing with the altitude. Numerical experiments with a nonlinear wave model showed that the initial acoustic–gravity wave pulse occurring when a non-stationary ground wave source is “switched on” can create a system of relatively slow moving mesoscale irregularities at altitudes from the Earth’s surface to the upper atmosphere. The trapped GW modes excited by a supersonic surface source may feed this system of irregularities with energy and ensure its existence within time intervals of up to tens of wave periods. The irregularities can form undulatory inclined wave fronts, similar to effective upward propagating GWs. Thus, the supersonic trapped modes excited on the Earth’s surface can create atmospheric internal GWs having subsonic horizontal phase velocities and spreading to high altitudes.

Mozart's and Bach's music yielded little relaxation effect as indicated HR, BP, and autonomic nervous activity

BackgroundSince the Mozart effect was first reported in 1993, it has been commonly proposed that listening to music has beneficial effects on physical and mental health. The putative relaxation effect of Mozart's music has been exploited for commercial purposes. Moreover, it has been reported that Bach's music has a relaxation similar to Mozart's music. Despite these widespread claims, few scientific or clinical investigations have shown compelling evidence demonstrating relaxation effects of Mozart's and/or Bach's music.ObjectiveThe purpose of this study was to evaluate the effects of Mozart's Sonata for Four Hands in D‐major (K448) and Bach's Brandenburg Concerto No.4 in G‐major (BWV1049) on heart rate (HR), blood pressure (BP), and autonomic nervous activity in healthy young adults.MethodsWe enrolled seventeen healthy young adults with an average age of 21.9 ± 0.9 years in our study. After 10 minutes of rest, all volunteers underwent three tasks in a randomized order: an examination to induce a mental work load and two 8‐minute intervals of music listening. The control group underwent two 8‐minute periods of silence rather than music. We assessed the electrocardiogram continuously from the start of each experiment to completion. Spectral analysis was performed to determine the low frequency (LF, 0.04–0.15 Hz) and high frequency (HF, 0.15–0.40 Hz) spectral components of heart late variability (HRV). The HF component was used as an index of parasympathetic nervous activity, and the ratio of LF to HF components (LF/HF) was used as an index of sympathetic nervous activity. Additionally, we measured BP before and after each workload‐inducing examination, and after each music‐listening or silence period. The selected music consisted of K448 and BWV1049. All data are expressed as mean ± SE. One‐way repeated‐measures ANOVA and multiple comparison tests were performed to compare each index. A value of P &lt; 0.05 was considered significant.ResultsThere were significant decrease in HR and diastolic blood pressure (DBP) upon listening to K448 and BWV1049, or during silence in the case of control, but no significant change in systolic blood pressure (SBP) in any condition. HF spectral components of HRV showed insignificant changes in BWV1049 and control; however, it was significantly decreased in K448. LF/HF was not significantly lower after the examination compared to other task conditions in the K448, BWV1049, or control groups. There were no significant differences in the rate of change in HR, SBP, DBP, HF, and LF/HF during K448, BWV1049, or silence (control).ConclusionWe did not identify significant changes in HR, BP, or LF/HF in healthy young adults while they listened to K448 or BWV1049. However, HF did decrease after listening to K448. Overall, our findings suggested that Mozart's and Bach's music yielded little relaxation effect as indicated HR, BP, and autonomic nervous activity.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract P019: Insulin resistance indexes and lower heart rate variability in older adults: the Atherosclerosis Risk in Communities Study (ARIC)

Introduction: Lower heart rate variability (HRV) is an indicator of cardiac autonomic dysfunction which is associated with cardiovascular disease in diabetes. Whether pre-diabetes insulin resistance contributes to lower HRV is not clear; insulin resistance (IR) indexes reflect different aspects of IR, including dysregulation of glucose, insulin, and lipids. We hypothesized that IR indexes are inversely associated with HRV. Methods: We analyzed 48-hour ambulatory electrocardiograms on 759 adults in a sample of the ARIC Study, excluding diabetes, antiarrhythmic medications, and missing/poor quality recordings. Insulin resistance indexes were defined as quartiles for the homeostatic model assessment of insulin resistance (HOMA-IR), triglyceride to HDL-C ratio (TG/HDL-C), and triglyceride-glucose index (TyG). Low HRV was defined as &lt;25 th percentile for time domain measures -- including the standard deviation of all NN intervals (SDNN) and square root of the mean squared differences of successive NN intervals (RMSSD), and frequency domain measures -- including the high-frequency (HF) and low-frequency (LF) spectral components. Logistic regression with weights for sampling and nonresponse was used to estimate odds ratios and 95% confidence intervals (OR, 95% CI). Results: Mean age was 75 years [993 (63%) women, 688 (43%) African American]. The following results are reported for TyG. For time domain measures, high IR indexes were significantly associated with low SDNN (OR 1.83, 95% CI 1.09, 3.07), but not with low RMSSD (OR 1.48, 95% CI 0.89, 2.46). For frequency domain measures, high IR indexes were not associated with low HF (OR 1.62, 95% CI 0.96, 2.74), but significantly associated with low LF (OR 1.95, 95% CI 1.15, 3.30). Although results for other indexes were in the same direction, most were not statistically significant. Conclusions: Insulin resistance indexes may be inversely associated with HRV. An understanding of this relationship informs public health strategies for prevention of cardiovascular risk.

Pulse photoplethysmographic amplitude and heart rate variability during laparoscopic cholecystectomy: A prospective observational study.

Surgical stress affects the autonomic nervous system by increasing sympathetic outflow. One method of monitoring sympathetic activity is pulse photoplethysmographic analysis. From this two indices can be derived - autonomic nervous system state (ANSS) and ANSS index (ANSSi). It has recently been claimed that these indices can be used to measure sympathetic activity in anaesthetised patients, but their validity has not yet been demonstrated. To measure changes in pulse photoplethysmographic indices and determine any agreement with autonomic nervous system modulation of the cardiovascular system in healthy study participants during surgery under general anaesthesia. Prospective observational study. Single-centre study based at a tertiary care centre in Milan, Italy. Healthy patients undergoing general anaesthesia for elective laparoscopic cholecystectomy. ANSS, ANSSi, and heart rate variability (HRV) were analysed at three main times: baseline, after induction of general anaesthesia, and after pneumoperitoneum insufflation. The magnitude of changes in photoplethysmographic and HRV indices was measured. The agreement between pulse photoplethysmographic and HRV-derived indices was assessed by Bland-Altman plots. In total, 52 patients were enrolled and their data analysed. Both pulse photoplethysmographic and HRV indices changed during the study phases. An agreement was found between ANSSi and low frequency spectral components of HRV [bias 10.2nu, 95% confidence interval (CI) -13 to 33.4], high frequency spectral components of HRV (bias 6.1 nu, 95% CI -16.3 to 28.6), and low frequency/high frequency ratio (bias 16.1nu, 95% CI -1.4 to 33.5). The agreement was weaker between ANSSI and HRV indices. The study endorses the use of pulse photoplethysmographic indices ANSS and ANSSi as surrogates to estimate changes of autonomic modulation of the cardiovascular system in healthy adults during surgery under general anaesthesia.Orcid ID: orcid.org/0000-0002-9616-803X.

Synchronization to metrical levels in music depends on low-frequency spectral components and tempo.

Previous studies have found relationships between music-induced movement and musical characteristics on more general levels, such as tempo or pulse clarity. This study focused on synchronization abilities to music of finely-varying tempi and varying degrees of low-frequency spectral change/flux. Excerpts from six classic Motown/R&B songs at three different tempos (105, 115, and 130 BPM) were used as stimuli in this experiment. Each was then time-stretched by a factor of 5% with regard to the original tempo, yielding a total of 12 stimuli that were presented to 30 participants. Participants were asked to move along with the stimuli while being recorded with an optical motion capture system. Synchronization analysis was performed relative to the beat and the bar level of the music and four body parts. Results suggest that participants synchronized different body parts to specific metrical levels; in particular, vertical movements of hip and feet were synchronized to the beat level when the music contained large amounts of low-frequency spectral flux and had a slower tempo, while synchronization of head and hands was more tightly coupled to the weak flux stimuli at the bar level. Synchronization was generally more tightly coupled to the slower versions of the same stimuli, while synchronization showed an inverted u-shape effect at the bar level as tempo increased. These results indicate complex relationships between musical characteristics, in particular regarding metrical and temporal structure, and our ability to synchronize and entrain to such musical stimuli.

A new analysis of heart rate variability in the assessment of fetal parasympathetic activity: An experimental study in a fetal sheep model.

Analysis of heart rate variability (HRV) is a recognized tool in the assessment of autonomic nervous system (ANS) activity. Indeed, both time and spectral analysis techniques enable us to obtain indexes that are related to the way the ANS regulates the heart rate. However, these techniques are limited in terms of the lack of thresholds of the numerical indexes, which is primarily due to high inter-subject variability. We proposed a new fetal HRV analysis method related to the parasympathetic activity of the ANS. The aim of this study was to evaluate the performance of our method compared to commonly used HRV analysis, with regard to i) the ability to detect changes in ANS activity and ii) inter-subject variability. This study was performed in seven sheep fetuses. In order to evaluate the sensitivity and specificity of our index in evaluating parasympathetic activity, we directly administered 2.5 mg intravenous atropine, to inhibit parasympathetic tone, and 5 mg propranolol to block sympathetic activity. Our index, as well as time analysis (root mean square of the successive differences; RMSSD) and spectral analysis (high frequency (HF) and low frequency (LF) spectral components obtained via fast Fourier transform), were measured before and after injection. Inter-subject variability was estimated by the coefficient of variance (%CV). In order to evaluate the ability of HRV parameters to detect fetal parasympathetic decrease, we also estimated the effect size for each HRV parameter before and after injections. As expected, our index, the HF spectral component, and the RMSSD were reduced after the atropine injection. Moreover, our index presented a higher effect size. The %CV was far lower for our index than for RMSSD, HF, and LF. Although LF decreased after propranolol administration, fetal stress index, RMSSD, and HF were not significantly different, confirming the fact that those indexes are specific to the parasympathetic nervous system. In conclusion, our method appeared to be effective in detecting parasympathetic inhibition. Moreover, inter-subject variability was much lower, and effect size higher, with our method compared to other HRV analysis methods.

LeafletAnalyzer, an Automated Software for Quantifying, Comparing and Classifying Blade and Serration Features of Compound Leaves during Development, and among Induced Mutants and Natural Variants in the Legume Medicago truncatula.

Diverse leaf forms ranging from simple to compound leaves are found in plants. It is known that the final leaf size and shape vary greatly in response to developmental and environmental changes. However, changes in leaf size and shape have been quantitatively characterized only in a limited number of species. Here, we report development of LeafletAnalyzer, an automated image analysis and classification software to analyze and classify blade and serration characteristics of trifoliate leaves in Medicago truncatula. The software processes high quality leaf images in an automated or manual fashion to generate size and shape parameters for both blades and serrations. In addition, it generates spectral components for each leaflets using elliptic Fourier transformation. Reconstruction studies show that the spectral components can be reliably used to rebuild the original leaflet images, with low, and middle and high frequency spectral components corresponding to the outline and serration of leaflets, respectively. The software uses artificial neutral network or k-means classification method to classify leaflet groups that are developed either on successive nodes of stems within a genotype or among genotypes such as natural variants and developmental mutants. The automated feature of the software allows analysis of thousands of leaf samples within a short period of time, thus facilitating identification, comparison and classification of leaf groups based on leaflet size, shape and tooth features during leaf development, and among induced mutants and natural variants.

Atypical autonomic nervous system complexity accompanies social cognition task performance in ASD

BackgroundEmerging evidence suggests that autonomic nervous system (ANS) function is affected in ASD. Existing literature has focused on quantifying the activity of ANS components (i.e. sympathetic/parasympathetic systems) individually. To this end, measures such as respiratory sinus arrhythmia (RSA) and high- and low-frequency spectral components of heart rate variability have been employed. Recent findings indicate that these methods employ assumptions that do not fully consider the complexity of the ANS system and the interaction of its components. To this end, we propose a new method for examining ANS function in ASD. MethodsA sample of typically developing (TD) children (n=34) and children with ASD (n=45) performed the Reading the Mind in the Eyes Task (RMET), preceded and followed by periods of baseline movie-watching. Multiscale Entropy (MSE) was employed as a new tool to examine the complexity of the cardiac signal. ResultsSignificant group differences in MSE emerged to suggest atypicality in the regularity of the autonomic signal at short and long time scales in the ASD group during the RMET task. ConclusionsFor the RMET task, our results may suggest atypical activation of parasympathetic influences on the heart, which contributes to short-term patterns in the heartbeat signal, as well as atypicalities in the slower acting processes. Results also suggest that the coupling between the fast-acting and slow-acting influences may be atypical in ASD during the examined social cognition task.

Changes in linear and nonlinear measures of RR and QT interval series after beer intake

Background/Aim. There are only several studies on the acute effect of alcoholic drinks intake on heart rhythm and this phenomenon is still not well understood. We wanted to examine whether linear and nonlinear measures of RR interval and QT interval series could quantify the effect of beer in healthy subjects. Methods. Eighteen young volunteers drank 500 mL of beer (21 g of ethanol). Electrocardiogram (ECG) recordings were taken in supine position: 20 minutes before (relaxation) and 60 minutes after drink intake. The RR interval series and the QT interval series were extracted from ECG and we calculated short-term (?1) and long-term (?2) scaling exponents and sample entropy (SampEn) for both series; low frequency (LF) and high frequency (HF) spectral components from RR interval series and QT variability (QTV). Blood pressure was measured every 10 minutes. Results. It was shown that beer induced changes in variability and correlation properties of these series. Immediate effect of beer intake was detected as a transient increase in the QT variability, heart rate and blood pressure. Delayed effects of beer were shortening of the RR and QT intervals and reduction of the HF spectral component. Beer intake also increased short-term scaling exponent (?1) of the RR time series and long-term scaling exponent (?2) of the QT time series. Conclusion. Our results suggest that acute effects of beer are reduced parasympathetic control of the heart and changed dynamic complexity of the ventricular repolarization.

Hydrocarbon detection for Ordovician carbonate reservoir using amplitude variation with offset and spectral decomposition

We have developed an example of hydrocarbon detection for an Ordovician cavern carbonate reservoir in western China with a burial depth exceeding 6600 m using amplitude variation with offset (AVO) and spectral decomposition. We selected six production wells, three prolific oil wells, and three brine wells to test the hydrocarbon detection method. The three oil wells have been producing for more than three years, and the three water wells only produce brine. We performed spectral decomposition to the angle gathers and analyzed amplitude variation patterns with incidence angles for different spectral components. Specifically, we compared the time corresponding to the peak spectral amplitude for different spectral components for the oil- and brine-saturated carbonate reservoirs. The main findings are as follows: (1) Oil-saturated cavern carbonate reservoirs show decreasing peak time with increasing frequency; i.e., the high-frequency components travel faster than do the low-frequency components. The maximum time difference between the 10 and 50 Hz spectral components could reach 35 ms. In contrast, the brine-saturated carbonate reservoirs do not exhibit conspicuous variation in the peak time, (2) AVO attributes extracted from the low-frequency spectral gathers are more robust than those extracted from the original seismic gathers, (3) oil-saturated cavern carbonate reservoirs cause strong energies in the low-frequency spectral components and severe attenuation to the high-frequency spectral components at large incidence angles. In contrast, the brine-saturated carbonate reservoirs do not produce such phenomenon. Rock physics analysis for carbonate reservoirs under different saturation conditions was conducted. The synthetic gathers were generated for carbonate reservoirs under oil- and brine-saturated conditions. The spectrally decomposed synthetic gathers are in agreement with the real gathers. The results indicate that AVO analysis of spectrally decomposed prestack gathers could be used as an effective hydrocarbon detection method for carbonate reservoirs.

Quantification of autonomic nervous activity by heart rate variability and approximate entropy in high ultrafiltration rate during hemodialysis.

Few studies have focused on the imbalance of the autonomic nervous system in ultrafiltration rate (UFR) subjects without blood pressure variation during maintenance hemodialysis (HD), although the role of autonomic nervous system activation during HD has been proposed to be an important factor for the maintenance of blood pressure. Variations over time in autonomic nervous activity due to differences in UFR were evaluated by measuring heart rate variability (HRV) and approximate entropy (ApEn) in 35 HD patients without blood pressure variations during HD session. The subjects were divided into 3 groups, those with UFR<10ml/h/kg;≥10ml/h/kg but≤15ml/h/kg; and>15ml/h/kg, and Holter ECG was recorded continuously during HD session using frequency analysis of RR intervals. High frequency (HF) and low frequency (LF) spectral components are found to be representative of the parasympathetic nervous system and sympathovagal balance, respectively, with the ratio of LF to HF of HRV providing a measure of sympathetic nervous system. In subjects with UFR>15ml/h/kg, HF components were significantly lower, and LF/HF and ApEn values were significantly higher, in the latter half of an HD session than before starting HD. Removing water from these subjects would promote sustained sympathetic nervous overactivity. These findings indicate that the UFR during HD needs to be set at≤15ml/h/kg.

Experimental studies of sound field suppression at discrete frequencies

Practical implementation of an active sound control system ensuring sound suppression in outer space is described as applied to sound insulation problems for equipment whose total noise level is mainly due to low-frequency discrete spectral components. The operational principle of the proposed system is based on inverse field generation with respect to the field of the initial source of quasi-monochromatic signals. The inverse field is formed by a set of radiators, which are controlled by the signals of pressure receivers positioned in the near field of the source. Experimental studies carried out with the proposed sound control system demonstrate its efficiency and testify to the stability of its operation.

Gender comparison of cardiac autonomic functions as measured by heart rate variability in a tertiary care hospital

Introduction: Heart rate variability (HRV) has been proposed as an indicator of cardiovascular health. Compared to their male counterparts, women are at less risk of coronary heart disease, and of serious arrhythmias, with women lagging behind men in the incidenceof sudden death by 20 years since women have a lower cardiovascular risk, a hypothesis was generated that there exist gender differences in autonomic modulation. Methods: We studied 100 subjects (50 males and 50 females). Anthropometric parameters like age; height; weight and BMI were measured. The baseline characteristics like resting heart rate; systolic blood pressure and diastolic blood pressure were recorded at supine rest for 5 minutes. Using HRV software, recording and analysis of HRV parameters like Total power; Low frequency; Low frequency normalized units; High frequency; High frequency normalized units and Low frequency / High frequency ratio were done. Results: Frequency domain measures of HRV were compared in age-matched populations of 50 males and 50 females. The mean and standard deviation of the low-frequency spectral components of HRV analyzed as absolute units as well as normalised units were high in males as compared to females (p

Cardiovascular variability is similarly altered in coronary patients with normal left ventricular function and in heart failure patients.

After myocardial infarction (MI), baroreflex function is impaired and heart rate (HR) variability is reduced. An impaired baroreflex has been observed also in coronary patients with no previous MI, leading to hypothesize alterations of HR variability also in these patients. The aim of the present work was, therefore, to study whether and to what extent cardiovascular variability is altered in coronary patients with no previous MI. Thirty-two individuals were studied: eleven patients with coronary artery disease but no previous MI [coronary artery disease (CAD)], eleven patients with a reduced left ventricular ejection fraction [congestive heart failure (CHF)] and ten age-matched controls (CNT). Overall HR variability was significantly and similarly reduced in CAD (630 ± 272 ms) and CHF patients (594 ± 395 ms) with respect to CNT (1405 ± 837 ms), this being the case also for the low and high frequency spectral components. Low-frequency oscillations of blood pressure (BP) were also significantly and similarly less pronounced in CAD (0.7 ± 0.7 mmHg) and CHF patients (0.7 ± 0.7 mmHg) compared with CNT (1.8 ± 1.4 mmHg). Moreover, both CAD and CHF patients showed a significantly reduced baroreflex function and an increased pulse-wave velocity with respect to CNT. Our study shows that in coronary patients with no MI and no left ventricular dysfunction, there is a profound alteration of both HR and BP variability as in CHF patients, presumably because of a marked impairment of the autonomic modulation of the heart and blood vessels.

Double wavelet transform of frequency-modulated nonstationary signal

A mathematical model is proposed for a frequency-modulated signal in the form of a system of Gaussian peaks randomly distributed in time. An analytic expression is obtained for continuous wavelet transform (CWT) of the model signal. For signals with time-varying sequence of peaks, the main ridge of the skeleton characterized by frequency νmaxMFB (t) is analyzed. The value of νmaxMFB (t) is determined for any instant t from the condition of the CWT maximum in the spectral range of the main frequency band (MFB). Double CWT of function νmaxMFB (t) is calculated for a frequency-modulated signal with a transition regions of smooth frequency variation (trend) as well as with varying frequency oscillations relative to the trend. The duration of transition periods of the signal is determined using spectral integrals Eν(t). The instants of emergence and decay of low-frequency spectral components of the signal are determined. The double CWT method can be used for analyzing cardiac rhythms and neural activity, as well as nonstationary processes in quantum radio physics and astronomy.