Low-frequency Power Research Articles

Pitfalls and possibilities of using Root SedLine for continuous assessment of EEG waveform-based metrics in intensive care research

Objective. The Root SedLine device is used for continuous electroencephalography (cEEG)-based sedation monitoring in intensive care patients. The cEEG traces can be collected for further processing and calculation of relevant metrics not already provided. Depending on the device settings during acquisition, the acquired traces may be distorted by max/min value cropping or high digitization errors. We aimed to systematically assess the impact of these distortions on metrics used for clinical research in the field of neuromonitoring. Approach. A 16 h cEEG acquired using the Root SedLine device at the optimal screen settings was analyzed. Cropping and digitization error effects were simulated by consecutive reduction of the maximum cEEG amplitude by 2 µV or by reducing the vertical resolution. Metrics were calculated within ICM+ using minute-by-minute data, including the total power, alpha delta ratio (ADR), and 95% spectral edge frequency. Data were analyzed by creating violin- or box-plots. Main Results. Cropping led to a continuous reduction in total and band power, leading to corresponding changes in variability thereof. The relative power and ADR were less affected. Changes in resolution led to relevant changes. While the total power and power of low frequencies were rather stable, the power of higher frequencies increased with reducing resolution. Significance. Care must be taken when acquiring and analyzing cEEG waveforms from Root SedLine for clinical research. To retrieve good quality metrics, the screen settings must be kept within the central vertical scale, while pre-processing techniques must be applied to exclude unacceptable periods.

Interplays between Metabolic Hormones, Metabolic Factors, Kidney Function Parameters, and Heart Rate Variability

Metabolic Syndrome (MetS) is associated with autonomic cardiac dysregulation, reflected by changes in heart rate variability (HRV) and detrimental effects on kidney function. This study aimed to 1) compare metabolic factors and hormones, kidney function profiles, and HRV parameters, including SDSD, RMSSD, pNN50, high-frequency power (HF), low-frequency power (LF), LF/HF ratio, between subjects with/without MetS or insulin resistance and 2) determine the correlations among these variables. We hypothesized that these factors differed between subjects with and without metabolic disturbances. Furthermore, we expected that metabolic factors and hormones and kidney function parameters were associated with HRV. In Thai obese subjects, characterized by BMI ≥ 25 kg/m2 for an Asian population (n = 45), fasting blood samples and spontaneous 5-minute HRV were obtained. The criteria for MetS were defined by The NCEP ATP III 2005 definition, except waist circumference which is ≥ 90 cm in men and 80 cm in women for Asians. Insulin resistance was determined by homeostatic model assessment for insulin resistance (HOMA-IR) > 2.3. In subjects with MetS (n = 19), percent fat, HOMA-IR, and serum leptin were significantly higher than those without MetS (n = 26), all with P < 0.05. Serum adiponectin, SDSD, RMSSD, and LF in ms2 tended to decrease in subjects with MetS. In subjects with insulin resistance (n = 30), BMI and serum leptin were significantly higher than those without insulin resistance (n = 15), all with P < 0.05. HDL-cholesterol (HDL-C) was significantly lower in subjects with insulin resistance, all with P < 0.05. Serum leptin exhibited positive correlations with BMI, creatinine clearance (CrCl), serum insulin, and HOMA-IR (R = 0.433-0.778) but had a negative correlation with HDL-C (R = -0.303), all with P < 0.05. Serum insulin showed positive correlations with BMI, CrCl, and serum leptin (R = 0.328-0.437); while it had negative correlations with age and HDL-C (R = (-0.310)-(-0.438)), all with P < 0.05. Serum adiponectin demonstrated positive correlations with HDL-C and pNN50 (R = 0.329-0.473), all with P < 0.05. CrCl had positive correlations with BMI, HOMA-IR, serum insulin and leptin, and HF in normal unit (nu) (R = 0.304-0.617); and negative correlations with LFnu, and LF/HF ratio (R = (-0.317)-(-0.386)), all with P < 0.05. HDL-C demonstrated significant positive correlations with serum adiponectin, SDSD, and RMSSD (R = 0.329-0.331); while showed negative correlations with the number of criteria met for MetS, BMI, triglyceride, serum insulin and leptin, and HOMA-IR (P = (-0.303)-(-0.595)), all with P < 0.05. LDL-cholesterol (LDL-C) had negative correlations with percent fat and pNN50 (R = (-0.313)-(-0.340)), all with P < 0.05. Subjects with metabolic syndrome tended to have decreased insulin sensitivity, serum adiponectin, as well as parasympathetic (SDSD, RMSSD) and sympathetic (LF) HRV. Those with insulin resistance showed lower level of HDL-C. Leptin and insulin were correlated with obesity, metabolic factors, insulin resistance, and kidney function parameters but not HRV. Interestingly, serum adiponectin exhibited a positive correlation with HDL-C, and both serum adiponectin and HDL-C, which are protective factors, had positive correlations with parasympathetic HRV (pNN50, SDSD, and/or RMSSD). Conversely, LDL-C showed a negative correlation with parasympathetic HRV (pNN50). Creatinine clearance was positively correlated with parasympathetic HRV (HF) and negatively correlated with sympathetic HRV (LFnu and LF/HF ratio). In conclusion, MetS was linked to shifts in HRV, with reductions in both parasympathetic and sympathetic components. HDL-C exhibited a protective role in metabolic disturbances. Parasympathetic HRV was positively correlated with protective factors but negatively with LDL-C. Deteriorating kidney function was associated with increased sympathetic HRV and decreased parasympathetic HRV. The research was funded by the Faculty of Medicine Siriraj Hospital Research Fund ((IO) R015932003, R0159333013 and R016132012. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Influence of Perceived Discrimination on Heart Rate Variability in Young Black Adults

Introduction: Cardiovascular disease (CVD) is the leading cause of death in the United States, with a disproportional precedence in Black adults. Heart rate variability (HRV) is used to help predict future CVD, with lower HRV indicative of a compromised cardiovascular system. Prior evidence has suggested that experienced racial discrimination is associated with CVD risk. However, there is limited information regarding experienced racial discrimination on HRV in young Black adults. Purpose/hypothesis: The purpose of this study was to determine whether personal-level and group-level racial discrimination was associated with worse HRV in young Black adults. Methods: Black adults aged 18-25 (n=18, 44.45% female) volunteered to participate in this study, arriving at the lab at 7am in a fasted state. Following 30 minutes of rest, HRV measures were assessed using a SphygmoCor 3-lead ECG in a supine position. The HRV measure included the standard deviation of all R-R intervals (SDNN), the mean number of times an hour successive NN intervals exceeds 50ms (pNN50), the root mean square of successive differences (RMSSD), the low-frequency (LF) power domain, high-frequency (HF) power domain, and their ratio (LF:HF). Participants were given a perceived racial discrimination questionnaire that assessed personal-level and group-level discrimination. Pearson correlations were used to analyze the association between perceived racial discrimination measures and HRV measures. Results: In Black males, perceived personal-level racial discrimination was negatively associated with sympathetic activity (LF, R2 = -0.704, p = 0.023) and sympathovagal balance (LF:HF, R2 = -0.749, p = 0.013), and positively associated with parasympathetic activity (HF, R2 = 0.704, p = 0.023). Perceived group-level racial discrimination was not associated with HRV measures. Furthermore, perceived racial discrimination was not associated with HRV in Black females. Conclusion: Although decreased HRV has been associated with increased risk for CVD, higher HRV has been shown to be associated with left ventricular mass in Black adults. Therefore, HRV implications may be dependent on social determinants of health and other covariates that are associated with race/ethnicity. In the current study, higher HRV was observed in Black males who reported higher personal-level discrimination, which may be an important factor in sympathetic and parasympathetic cardiac control and CVD risk. Given our preliminary findings, more research is warranted that investigates the impact of racial identity, resiliency, coping, and healthy lifestyle behaviors on mitigating the detrimental impact of perceived racial discrimination on the cardiovascular health of young Black adults. Summer Undergraduate Research Fellowship Recipient from the American Physiological Society. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The X-ray variability of active galactic nuclei: Power spectrum and variance analysis of the Swift/BAT light curves

Aims. We study the X-ray power spectrum of active galactic nuclei (AGN) in order to investigate whether Seyfert I and II power spectra are similar or not and whether AGN variability depends on the mass and accretion rate of black holes as well as to compare the power spectra of AGN with the power spectra of Galactic X-ray black hole binaries. Method. We used 14–195 keV band light curves from the 157-month Swift/BAT hard X-ray survey, and we computed the mean power spectrum and excess variance of AGN in narrow black hole mass and AGN luminosity bins. We fitted a power-law model to the AGN power spectra, and we investigated whether the power spectrum parameters and the excess variance depend on the black hole mass, luminosity, and accretion rate of AGN. Results. We found the Seyfert I and Seyfert II power spectra to be identical, in agreement with AGN unification models. The mean AGN X-ray power spectrum has the same power-law like shape, with a slope of −1 in all AGN irrespective of their luminosity and black hole mass. We did not detect any flattening to a slope of zero at frequencies as low as 10−9 Hz. We detected an anti-correlation between the power spectral density function (PSD) amplitude and the accretion rate, similar to what has been seen in the past in the 2–10 keV band. This implies that the variability amplitude in AGN decreases with an increasing accretion rate. The universal AGN power spectrum is consistent with the mean 2–9 keV band Cyg X-1 power spectrum in its soft state. We detected a small difference in amplitude, but this is probably due to the difference in energy. Conclusions. The mean low-frequency AGN X-ray power spectrum is consistent with the extension of the mean 0.01–25 Hz Cyg X-1 power spectrum in its soft state to lower frequencies. We cannot prove that the mean AGN PSD is analogous to the mean Cyg X-1 PSD in its soft state, as we do not know the location of the high-frequency break in the hard X-ray AGN PSDs. However, if this is the case, then the accretion disc in AGN probably extends to the radius of the innermost circular stable orbit (as is probably the case with the black hole binaries in their soft state). The X-ray corona will then be located on top, illuminating the disc and producing the X-ray reflection and disc reverberation phenomena commonly observed in these objects. Furthermore, the agreement between the PSD amplitude in AGN and the Cyg X-1 (either in the soft or the hard state) over many decades in frequency indicates that the X-ray variability process is probably the same in all accreting objects, irrespective of the mass of the compact object. We plan to investigate this issue further in the near future.

3D hydrodynamic simulations of massive main-sequence stars – II. Convective excitation and spectra of internal gravity waves

ABSTRACT Recent photometric observations of massive stars have identified a low-frequency power excess which appears as stochastic low-frequency variability in light-curve observations. We present the oscillation properties of high-resolution hydrodynamic simulations of a $25\,\,{\rm{M}_\odot }$ star performed with the PPMstar code. The model star has a convective core mass of $\approx 12\,\,{\rm{M}_\odot }$ and approximately half of the envelope simulated. From this simulation, we extract light curves from several directions, average them over each hemisphere, and process them as if they were real photometric observations. We show how core convection excites waves with a similar frequency as the convective time-scale in addition to significant power across a forest of low and high angular degree l modes. We find that the coherence of these modes is relatively low as a result of their stochastic excitation by core convection, with lifetimes of the order of 10s of days. Thanks to the still significant power at higher l and this relatively low coherence, we find that integrating over a hemisphere produces a power spectrum that still contains measurable power up to the Brunt–Väisälä frequency. These power spectra extracted from the stable envelope are qualitatively similar to observations, with the same order of magnitude yet lower characteristic frequency. This work further shows the potential of long-duration, high-resolution hydrodynamic simulations for connecting asteroseismic observations to the structure and dynamics of core convection and the convective boundary.

EGCG’s effects on Mean Arterial Pressure and Heart Rate Variability and Their Correlations with Metabolic and Hormonal Profiles in Obese Subjects

This study aimed to investigate the effects of epigallocatechin gallate (EGCG), a potent polyphenol found in green tea, on mean arterial pressure (MAP) and heart rate variability (HRV) in obese subjects along with their associations with metabolic factors. We hypothesized that EGCG treatment could significantly reduce MAP and sympathetic tone, represented by decreased low-frequency power (LF) and LF-to-high frequency power (HF) ratio. Furthermore, we expected that systolic blood pressure (SBP), diastolic blood pressure (DBP), and MAP would be positively correlated with obesity parameters, LF, and LF-to-HF ratio. This study is a double-blind, randomized controlled trial. Thai obese subjects with a body mass index (BMI) ≥ 25 kg/m2 (criteria for an Asian population) were randomly allocated into EGCG and placebo groups and received a capsule of 150 mg of EGCG or starch, respectively, twice a day without any dietary restrictions. Clinical and anthropometric data, as well as spontaneous 5-minute HRV measurements in both time and frequency domains, were assessed at baseline (week 0), week 4, and week 8. Additionally, 8-hour fasting blood samples were collected at weeks 0 and 8 to measure metabolic and hormonal levels. EGCG treatment for 8 weeks significantly reduced MAP compared to week 0 and week 4 (P < 0.05 for all). In the EGCG treatment group, there was a significant increase in the LF-to-HF ratio and a nonsignificant decrease in HF at week 8 compared to week 0. LF showed a trend toward increasing in week 8 of EGCG treatment compared to week 4. For correlation analysis at week 0, SBP had significant positive correlations with BMI, percent fat, fat mass, serum leptin and insulin levels, and the homeostatic model assessment for insulin resistance (HOMA-IR) (R = 0.468-0.593, p<0.05 for all) but had negative correlations with the quantitative insulin sensitivity check index (QUICKI) and HDL-cholesterol (R = (-0.437)-(-0.468), P <0.05 for all). DBP was positively correlated with age and HF in normal units (nu) (R = 0.412-0.568, p<0.05 for all), but was negatively correlated with height, HDL-cholesterol, LF in ms (R = (-0.379)-(-0.509), P <0.05 for all). MAP showed significant positive correlations with age, BMI, percent fat, fat mass, serum leptin levels, and HOMA-IR (R = 0.370-0.459, P < 0.05 for all), but had a negative correlation with HDL-cholesterol (R = -0.522, P = 0.004). EGCG treatment over an 8-week duration reduced MAP, a pivotal component of overall blood pressure in obese individuals, and exhibited a significant increase in the LF/HF ratio, tending toward an increase in LF and a non-significant decrease in HF. We postulate that the decrease in MAP may be attributed to EGCG's direct or indirect vasodilatory effects, potentially through the stimulation of nitric oxide production, reduced oxidative stress, and/or decreased levels of kisspeptin, a vasoconstrictive substance, as reported by previous studies. An increase in the LF/HF ratio could reflect a shift toward sympathetic nervous system dominance (LF) and/or a decrease in parasympathetic nervous system activity (HF) indicating a compensatory response to the reduced blood pressure post-vasodilation. HDL cholesterol showed negative correlations with SBP, DBP, and MAP, reflecting its protective benefit against high blood pressure. In summary, 8 weeks of EGCG treatment resulted in a significant decrease in MAP and an increase in the LF/HF ratio, reflecting EGCG’s primary vasodilatory effects and a compensatory increase in sympathetic nervous system activity. The research was funded by the Faculty of Medicine Siriraj Hospital Research Fund ((IO) R015932003, R0159333013 and R016132012). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Association Between Physical Activity/Heart Rate Variability Data Obtained Using a Wearable Device and Timed Motor Functional Tests in Patients with Duchenne Muscular Dystrophy: A Pilot Study.

Duchenne muscular dystrophy (DMD) is a devastating X-linked muscle disease. Clinical evaluation of DMD uses patient-intensive motor function tests, and the recent development of wearable devices allows the collection of a variety of biometric information, including physical activity. In this study, we examined differences in physical activity and heart rate variability (HRV) between patients with DMD and healthy subjects using a wearable device, and investigated any association between these parameters and motor function in patients with DMD. Participants were 7 patients with DMD and 8 healthy males, whose physical activity and HRV were provided by a wearable device. These data were used to investigate the relationship between both physical activity and HRV parameters and timed motor functional tests [Time to stand from supine, 10-meter walking time (10MWT), North Star Ambulatory Assessment (NSAA), and 6-minute walking test (6MWT)] in patients with DMD. Results of 24-hours physical activity, fat burning, total number of steps and active distance, average step rate, average exercise intensity during walking, exercise, degree of forward lean during walking, maximum heart rate, normalized low frequency power (LF norm), and maximum exercise intensity in patients with DMD were lower than those in control subjects. Physical activity and HRV parameters did not correlate with the time to stand from supine. The 10MWT positively correlated with average heart rate, while NSAA negatively correlated with average heart rate, total frequency power (TF), and very low frequency power (VLF) during arousal. The 6MWT negatively correlated with ratio LF/high frequency power (HF). Physical activity and HRV indices that differ from those of normal children and that correlate with motor function assessment may serve as digital biomarkers.

Human local field potentials in motor and non-motor brain areas encode upcoming movement direction

Limb movement direction can be inferred from local field potentials in motor cortex during movement execution. Yet, it remains unclear to what extent intended hand movements can be predicted from brain activity recorded during movement planning. Here, we set out to probe the directional-tuning of oscillatory features during motor planning and execution, using a machine learning framework on multi-site local field potentials (LFPs) in humans. We recorded intracranial EEG data from implanted epilepsy patients as they performed a four-direction delayed center-out motor task. Fronto-parietal LFP low-frequency power predicted hand-movement direction during planning while execution was largely mediated by higher frequency power and low-frequency phase in motor areas. By contrast, Phase-Amplitude Coupling showed uniform modulations across directions. Finally, multivariate classification led to an increase in overall decoding accuracy (>80%). The novel insights revealed here extend our understanding of the role of neural oscillations in encoding motor plans.

Modulation of Heart Rate Variability and Brain Excitability through Acute Whole-Body Vibration: The Role of Frequency.

This cross-over study aimed to explore effects of acute whole-body vibration (WBV) at frequencies of 5-35 Hz on heart rate variability and brain excitability. Thirteen healthy physically active college students randomly completed eight interventions under the following conditions: static upright standing without vibration (CON), static squat exercise (knee flexion 150°) on the vibration platform (SSE), and static squat exercise (knee flexion 150°) combined with WBV at vibration frequency of 5, 9, 13, 20, 25, and 35 Hz. Five bouts × 30 s with a 30-s rest interval were performed for all interventions. The brain's direct current potentials (DCPs), frequency domain variables (FDV) including normalized low frequency power (nLF), normalized high frequency power (nHF) and the ratio of LF to HF (LF/HF), along with the mean heart rate (MHR) were collected and calculated before and after the WBV intervention. Results suggested that WBV frequency at 5 Hz had a substantial effect on decreasing DCPs [-2.13 μV, t(84) = -3.82, p < 0.05, g = -1.03, large] and nLF [-13%, t(84) = -2.31, p = 0.04, g = -0.62, medium]. By contrast, 20-35 Hz of acute WBV intervention considerably improved DCPs [7.58 μV, t(84) = 4.31, p < 0.05, g = 1.16, large], nLF [17%, t(84) = 2.92, p < 0.05, g = 0.79, large] and the LF/HF [0.51, t(84) = 2.86, p < 0.05, g = 0.77, large]. A strong (r = 0.7, p < 0.01) correlation between DCPs and nLF was found at 5 Hz. In summary, acute WBV at 20-35 Hz principally activated the sympathetic nervous system and increased brain excitability, while 5-Hz WBV activated the parasympathetic nervous system and reduced brain excitability. The frequency spectrum of WBV might be manipulated according to the intervention target on heart rate variability and brain excitability.

Ambulatory electrocardiographic longitudinal monitoring in a canine model for Duchenne muscular dystrophy identifies decreased very low frequency power as a hallmark of impaired heart rate variability.

Duchenne muscular dystrophy (DMD) patients exhibit a late left ventricular systolic dysfunction preceded by an occult phase, during which myocardial fibrosis progresses and some early functional impairments can be detected. These latter include electrocardiographic (ECG) and heart rate variability (HRV) abnormalities. This longitudinal study aimed at describing the sequence of ECG and HRV abnormalities, using Holter ECG in the GRMD (Golden retriever muscular dystrophy) dog model, known to develop a DMD-like disease, including cardiomyopathy. Most of the known ECG abnormalities described in DMD patients were also found in GRMD dogs, including increased heart rate, prolonged QT and shortened PR intervals, ventricular arrhythmias, and several of them could be detected months before the decrease of fractional shortening. The HRV was impaired like in DMD patients, one of the earliest evidenced abnormalities being a decrease in the very low frequency (VLF) component of the power spectrum. This decrease was correlated with the further reduction of fractional shortening. Such decreased VLF probably reflects impaired autonomic function and abnormal vasomotor tone. This study provides new insights into the knowledge of the GRMD dog model and DMD cardiomyopathy and emphasizes the interest to monitor the VLF power in DMD patients, still unexplored in this disease, whilst it is highly predictive of deleterious clinical events in many other pathological conditions.

Exploratory analysis of spontaneous versus paced breathing on heart rate variability in veterans with combat-related traumatic injury.

Respiration is a crucial determinant of autonomic balance and heart rate variability (HRV). The comparative effect of spontaneous versus paced breathing on HRV has been almost exclusively explored in healthy adults and never been investigated in an injured military cohort. To examine the effect of spontaneous versus paced breathing on HRV in veterans with combat-related traumatic injury (CRTI). Observational cohort study. ArmeD serVices trAuma rehabilitatioN outComE (ADVANCE) study, Stanford Hall, UK. The sample consisted of 100 randomly selected participants who sustained CRTI (eg, amputation) during their deployment (Afghanistan 2003-2014) and were recruited into the ongoing ADVANCE prospective cohort study. Not applicable. HRV was recorded using a single-lead ECG. HRV data were acquired during a sequential protocol of 5-minute spontaneous breathing followed immediately by 5 minutesof paced breathing (six cycles/minute) among fully rested and supine participants. HRV was reported using time domain (root mean square of successive differences), frequency domain (low frequency and high frequency) and nonlinear (sample entropy) measures. The agreement between HRV during spontaneous versus paced breathing was examined using the Bland-Altman analysis. The mean age of participants was 36.5 ± 4.6 years. Resting respiratory rate was significantly higher with spontaneous versus paced breathing (13.4 ± 3.4 vs. 7.6 ± 2.0 breaths/minute; p < .001), respectively. Resting mean heart rate and root mean square of successive differences were significantly higher with paced breathing than spontaneous breathing (p < .001). Paced breathing significantly increased median low frequency power than spontaneous breathing (p < .001). No significant difference was found in the absolute power of high frequency between the two breathing protocols. The Bland-Altman analysis revealed poor agreement between HRV values during spontaneous and paced breathing conditions with wide limits of agreement. Slow-paced breathing leads to higher HRV than spontaneous breathing and could overestimate resting "natural-state" HRV.

Effect of dynamic binaural beats on sleep quality: a proof-of-concept study with questionnaire and biosignals.

Binaural beat (BB) has been investigated as a potential modality to enhance sleep quality. In this study, we introduce a new form of BB, referred to as dynamic BB (DBB), which incorporates dynamically changing carrier frequency differences between the left and right ears. Specifically, the carrier frequency of the right ear varied between 100 and 103 Hz over a period, while the left ear remained fixed at 100 Hz, yielding a frequency difference range of 0 to 3 Hz. The objective of this study was to examine the effect of DBB on sleep quality. Ten healthy participants were included in a cross-over design, where they experienced both DBB and a SHAM (absence of sound) condition across two consecutive nights, with polysomnography evaluation. DBB was administrated during pre-sleep initiation, sleep onset, and transition from rapid eye movement (REM) to non-REM stage. DBB significantly reduced sleep latency compared to the SHAM condition. Electrocardiogram analysis revealed that exposure to DBB led to diminished heart rate variability during the pre-sleep initiation and sleep onset periods, accompanied by a decrease in low-frequency power of heart rate during the sleep onset period. DBB might be effective in improving sleep quality, suggesting its possible application in insomnia treatments.

Electromagnetic telemetry signal denoising: An interference elimination via parameter estimation

Electromagnetic telemetry has emerged as a promising technique for the real-time acquisition of downhole data. However, the transmission of electromagnetic waves through the formation encounters attenuation, leading to a weakened received signal at the surface, typically registering at the microvolt level. The growing presence of surface electrical equipment in well-site environments has engendered heightened electromagnetic interference, thus deteriorating the signal-to-noise ratio (SNR) of received signals. The conventional linear filtering method can effectively eliminate the electromagnetic interference at the wellsite, but it has no effect on the low frequency interference close to the carrier frequency, especially the common low-frequency pulse interference (LPI) and power line interference (PLI). To mitigate the adverse effects of surface noise, we propose a nonlinear processing method based on parameter estimation algorithms. Generally, the proposed method entails reconstructing the interference by accurate parameter estimation and subtracting it from the received signal, aiming to enhance the SNR of the received signal. Simulation data and real noise data collected in the field are processed to verify the effectiveness of the proposed method. The results demonstrate the superiority of this approach over traditional filtering techniques in effectively eradicating surface interference.

Psychological Stress Analysis to Evaluate the Effects of Transcranial Magnetic Stimulation on Mood Regulation and Quality of Life in Patients with Bipolar Disorder.

To explore the impact of transcranial magnetic stimulation on emotion regulation and quality of life in patients with bipolar disorder (BD) and to evaluate the effectiveness of the mental stress analyzer. Patients with BD admitted to our hospital from August 2022 to August 2023 were retrospectively selected. For the present study, 60 patients who received drug therapy served as the control group, and the other 60 patients who received repeated transcranial stimulation on this basis served as the observation group. The heart rate variability (HRV) of the two groups of patients was detected by a mental stress analyzer/HRV analysis system. Hamilton Depression Rating Scale (HAMD), Self-Rating Anxiety Scale (SAS), and Self-Rating Depression Scale (SDS) were used to evaluate the mental state of the two groups of patients. The quality of life of the two groups was assessed using the Comprehensive Quality of Life Questionnaire 74 (GQOLI-74). Clinical effectiveness global rating scale-illness severity (CGI-SI) was used to evaluate the clinical symptoms of the two groups of patients, and the incidence of adverse reactions was calculated. In comparison to the control group, the high-frequency power (HF) of the patients demonstrated an elevation in the observation group, and the low-frequency power (LF) and LF/HF were significantly reduced (p < 0.05). The standard deviation of NN intervals (SDNN), standard deviation of all five-minute NN intervals (SDANN), root mean square of successive differences (rMSSD), and percent RR intervals with a difference in duration higher than 50 ms (PNN50) of patients in the observation group showed a notable increase compared to the control group (p < 0.05). Compared with the control group, the HAMD, SAS, and SDS scores of the patients in the observation group demonstrated a substantial decline relative to the control group (p < 0.05). In contrast to the control group, there was a significant increase in the overall clinical effectiveness rate among patients in the observation group, and the incidence of adverse reactions was significantly reduced (p < 0.05). Repetitive transcranial magnetic stimulation (rTMS) has significant clinical effects in treating BD and can effectively improve patients' anxiety, suppress emotions, and regulate patients' emotions. At the same time, rTMS has high safety and little impact on the balance of patients' autonomic nervous function, reduces the incidence of adverse reactions, accelerates the patient's recovery process, and is suitable for clinical promotion.

Active Damping for Dynamic Improvement of Multiple Grid-Tied Virtual Synchronous Generators

To eliminate low-frequency oscillations, this paper proposes an active-damping method for multiple grid-tied virtual synchronous generators (VSGs) in a power plant. Firstly, using the Lyapunov's indirect method, the damping ratio of multiple VSGs in parallel is analyzed. The average damping ratio reveals that this multi-VSG power plant can be poorly damped in a wide range of inertia and damping settings. Then, self- and mutual-damping controllers are developed to suppress self- and mutually induced low-frequency power oscillations, respectively. For the practical implementation, an adaptive tuning algorithm that enables automatic realization is proposed. Through a reassessment, a remarkable damping-ratio improvement is validated. Moreover, the inertial response improvement is validated by the frequency response analysis. Finally, simulations in Digsilent/PowerFactory and experiments are performed to demonstrate the accuracy of the analyses and the effectiveness of the proposed method.

Characterizing Heart Rate Variability Response to Maximal Exercise Testing in People with Huntington's Disease.

Huntington's disease (HD) is an autosomal dominant, neurodegenerative disease that involves dysfunction in the autonomic nervous system (ANS). Heart rate variability (HRV) is a valid and noninvasive measure for ANS dysfunction, yet no study has characterized HRV response to exercise in people with HD. Characterize HRV response to exercise in individuals with HD and explore its implications for exercise prescription and cardiac dysautonomia mechanisms. 19 participants with HD were recruited as part of a cohort of individuals enrolled in the Physical Activity and Exercise Outcomes in Huntington's Disease (PACE-HD) study at Teachers College, Columbia University (TC). 13 non-HD age- and gender-matched control participants were also recruited from TC. HRV was recorded with a Polar H10 heart rate (HR) monitor before, during, and after a ramp cycle-ergometer exercise test. Participants with HD showed reduced HR peak (p < 0.01) and HR reserve (p < 0.001) compared with controls. Participants with HD demonstrated reduced root mean square of successive differences between normal-to-normal intervals (RMSSD) and successive differences of normal-to-normal intervals (SDSD) at rest (p < 0.001). Participants with HD also showed differences for low frequency (LF) power (p < 0.01), high frequency (HF) normalized units (nu) (p < 0.05), LF (nu) (p < 0.001), and HF/LF ratio (p < 0.05) compared with controls. We found reduced aerobic exercise capacity and sympathovagal dysautonomia both at rest and during post-exercise recovery in people with HD, suggesting modified exercise prescription may be required for people with HD. Further investigations focusing on cardiac dysautonomia and underlying mechanisms of sympathovagal dysautonomia in people with HD are warranted.

A Modular Multilevel Converter-Shunt Active Power Filter-Based Hybrid Topology for Grid Power Quality Improvement

With the increasing penetration of renewable energy sources and active loads into the electrical power system, the limitations of traditional low-frequency power grids are becoming apparent. The solid-state transformer (SST), with its multiple conversion stages offering various power ports, is an innovative solution to these challenges. However, the high cost of the SST, due to its heavy reliance on power electronic components, makes the complete replacement of traditional grids an economically nonviable option. Therefore, this paper proposes a parallel connection of the SST to an existing traditional power grid in order to divide the transmitted power, thus reducing the investment costs. Furthermore, a hybrid topology based on modular multilevel converter (MMC) and shunt active power filter (SAPF) is proposed in this paper in order to compensate the harmonic currents caused by non-linear loads while maintaining steady energy delivery. Additionally, an artificial neural network (ANN) controller is adopted for the MMC output DC voltage control to ensure a regular DC-link voltage for both the SAPF and the DC-to-DC converter of the SST. The proposed topology is implemented and evaluated in MATLAB/Simulink software, and various simulation results are presented.

Abstract P353: Effect of Exergaming-Based Dance Training Paradigm in Improving Cardiovascular Function and Functional Mobility Among People With Chronic Stroke

Background: Dance-based exergaming (DBExG) , could potentially facilitate cardiovascular conditioning and functional mobility while enhancing physical activity behavior among people with chronic stroke (PwCS). Albeit, PwCS exhibits limitations (e.g., health care, and travel) in laboratory/outpatient rehabilitation programs, making them inaccessible. The DBExG from the laboratory (phase 1) to a safe and feasible home-based exercise program (phase 2) could effectively improve cardiovascular and functional mobility and address the accessibility limitations. Aim: To evaluate the feasibility, effect, and adherence of DBExG in promoting heart rate variability (HRV) and functional mobility in a laboratory and home-based rehabilitation approach. Design: Pre-post interventional study. Setting: Laboratory (phase 1) and home-based (phase 2) settings. Methods: Community-dwelling PwCS (n=10) participated in the study and received DBExG training using the commercially available Kinect dance gaming “Just Dance 3”. The first 6 weeks of training were provided in the laboratory setting and were delivered in a high-intensity tapering method with the first two weeks consisting of 5 sessions/week, the next two weeks of 3 sessions/week, and the last two weeks of 2 sessions/week, with a total of 20 sessions. Followed by 4 more weeks of DBExG training in the participant’s house (3 days/week), with a total of 12 sessions. Feasibility was addressed by acceptability and retention. Data obtained for HRV analysis pre- and post-intervention consists of HRV for ten minutes in (1) supine resting position; and (2) quiet standing. High-frequency (HF) power measures as indicators of cardiac parasympathetic activity, low-frequency (LF) power of parasympathetic-sympathetic balance, and LF/HF of sympatho-vagal balance were calculated. Six-minute walk test (6-MWT) was used to assess functional mobility. Changes in physical activity during pre- and post-intervention for one week and also during dance training were assessed using Fibit. Results: All participants completed the laboratory and home-based DBExG. All participants reported enjoying the sessions and most felt they were beneficial. Study retention and session adherence was 90% and 96%, in phase 1, and 2 respectively. There were no falls, or adverse safety events reported in either phase of the study. The results showed improvements in HRV HF, LF, and LF/HF. The result findings indicated significant improvement in the 6-MWT. The number of steps during dance intervention increased significantly from 1 st to the 32 nd session. Conclusions: A combination of laboratory, transitioned to home-based maintenance therapy approach appears feasible, safe, and effective thus promising for post-stroke rehabilitation. A larger randomized controlled trial is recommended to further investigate efficacy.

A low-power artificial spiking neuron based on ionic memristor for modulated frequency coding

Neurons encode information through firing spikes with rich spatiotemporal dynamics. Using artificial neuron hardware based on memristors to emulate neuronal firing is of great significance for advancing the development of brain-like computing and artificial intelligence. However, it is still challenging to achieve low power frequency coding in memristive artificial neurons. Here, a low-power ionic memristor based on Pt/HfO2/Ag is reported for artificial spiking neurons. The device is driven by a low bias current and the filament dynamically ruptures and forms, producing oscillated voltage spikes that resemble neuronal spikes. The oscillation frequency increases from 0.5 Hz to ∼2.18 Hz with the stimulation current increasing from 1 nA to 5 nA, enabling the emulation of neuronal frequency-coding function. The low power consumption of ∼70 pJ per pulse indicates that the device is promising for energy-efficient neuromorphic computing applications. In addition, the device is found to be capable of simulating the phasic,adaptive, and burst firing modes of neurons.

Characterizing B stars from Kepler /K2 Campaign 11. Optical analysis and seismic diagnostics

In this study, we analyze 122 B-type star candidates observed during Campaign 11 of the Kepler /K2 mission to investigate their variability and pulsation characteristics. A subset of 45 B star candidates was observed during the Kepler /K2 mission's Campaign 11 between September and December 2016. Our analyses aim to gain a deeper understanding of the physical characteristics of these massive stars. Our methods involve both spectroscopy and seismology. The spectroscopic analysis was performed through medium-resolution blue spectra, which also allowed us to perform a spectral classification of the objects. Our results will contribute to the ongoing effort to expand our knowledge of variable B stars and the processes that drive their variability. We used the iterative prewhitening and wavelet frequency searching algorithms to analyze the light curves to identify the different types of variability in the data. The frequencies were carefully chosen based on the signal-to-noise ratio and the magnitude of errors. We applied spectroscopic analysis techniques to enhance our understanding of the observed stars, including sme and mesa algorithms. A spectral classification was performed based on the observed spectra. The resulting astrophysical parameters were compared to Gaia mission data. Additionally, a seismology technique was applied to determine the average internal rotation frequency ($ rot $) and buoyancy travel time ($P_0$) for selected stars in the sample. We detected several types of variability among the B-type stars, including slowly pulsating B (SPB) stars, hybrid pulsators showing both beta Cep and SPB pulsations, stars with stochastic low-frequency (SLF) variability, Maia variables, and SPB/Maia hybrids. Their positions in our Gaia and classical HR diagrams are compatible with the theoretical expectations. We also found stars exhibiting variability attributed to binarity and rotation. We determined the physical characteristics for 45 of our targets and conducted a seismic analysis for 14 objects. Two SPB/Maia stars show internal velocities comparable to those of fast SPB stars. The derived average rotation frequencies, $ rot $, for these 14 stars lie between the critical $ crit Roche $ and the minimal frequency values of $ lim rot $ implied by the $ i $ measured from the spectra. Our analysis classified 41 stars as SPB stars and attributed the primary variability of 53 objects to binarity, rotation, or both. We identified five stars as Maia/fast-rotating SPB variables. Two stars were classified as hybrid SPB/beta Cep pulsators, and one as a beta Cep binary. Thirteen stars exhibited prominent, low-frequency power excess, indicating SLF variability. Additionally, we found a positive correlation between the dominant $ f g $ frequency and the internal average rotation frequency.