Power Of High Frequency Component Research Articles

Energy Management System for Grid-Connected Nanogrid during COVID-19

An effective energy management system (EMS) was designed based on the Stateflow (SF) approach for a grid-connected nanogrid (NG) composed of a photovoltaic (PV) array with a battery bank and supercapacitor (SC) energy storage system (ESS). The PV energy system, battery bank and SC (ESS), dual active bridge DC/DC converters, DC/AC inverters, control algorithms, and controllers were developed to test the operation of the NG. The average and high-frequency power components are separated using frequency division of the ESS power utilizing a low-pass filter; the average power is absorbed by the battery bank, while the high-frequency power is absorbed by the SC. The aim of this paper is to design an EMS to manage the energy of a grid-connected NG system considering the availability of the PV array, ESS, and demand requirements. Different scenarios of operation were tested to check the EMS behaviour during the day with a random demand profile, including: (1) a PV array with the grid supplying the load without an EMS; (2) a PV array, batteries, and the grid supplying the load with an EMS; (3) a PV array, batteries, an SC, and the grid supplying the load with an EMS; (4) a PV array, batteries, an SC, and the grid supplying the load with an EMS, with load profile reduction by 20% due to COVID-19. As per the simulation results, the proposed EMS enables the flow of power in the NG system and demonstrates the impact on the ESS by minimising carbon emissions via a reduction in grid consumption. Furthermore, the SF method is regarded as a helpful alternative to popular design approaches employing conventional software tools.

Association of Gut Microbial Genera with Heart Rate Variability in the General Japanese Population: The Iwaki Cross-Sectional Research Study.

The gut microbiota has become a significant factor associated with health and disease. Although many studies have reported the implications of changes in the gut microbiota on cardiovascular diseases, there are no reports on the relationship between heart rate variability (HRV) and the gut microbiota. Therefore, we investigated the association between gut microbiota abundance and HRV parameters in this cross-sectional study of the general Japanese population. This study included 950 participants of the Iwaki Health Promotion Project who underwent a medical examination in 2019 that included HRV and gut microbiota measurements. At the genus level, multivariate regression analysis showed that higher gut microbial diversity was associated with a higher standard deviation of RR intervals (SDNN). Moreover, a higher SDNN was associated with a higher relative count of Lachnospiraceae incertae sedis. L. incertae sedis abundance was associated with higher HRV parameters such as SDNN, coefficient of variation of RR intervals, low-frequency component power (LF)/high-frequency component power, and LF. In the general Japanese population, higher gut microbial diversity and L. incertae sedis abundance were associated with higher HRV parameters.

A Multi-Filter Based Dynamic Power Sharing Control for a Hybrid Energy Storage System Integrated to a Wave Energy Converter for Output Power Smoothing

The output power fluctuations from the wave energy converters (WECs) with a high peak-to-average ratio need to be smoothed out before supplying power to electric loads or power grids. Usually, short-term energy storage is used to smooth out the output power fluctuations of WECs. In this article, a novel multi-filter-based dynamic power-sharing control is devised for a hybrid energy storage system (HESS) integrated with a grid-connected WEC. An advanced model of HESS-integrated WEC consisting of a direct-drive permanent magnet linear generator, a supercapacitor, and a battery system is developed to test the proposed multi-filter-based dynamic control strategy under realistic conditions. The distinguishing features of this study are as follows; 1) the power-sharing strategy is based on a dynamic filter that is designed to change its corner frequency depending upon the incoming ocean wave, 2) the low and the high-frequency power components are allocated based on ocean wave conditions, 3) the proposed strategy is suitable for the real-time control of the proposed HESS integrated with the WEC, and 4) a detailed model of the WEC is used instead of using a pre-saved power profile. The results suggest that with the implementation of the proposed multi-filter-based dynamic power-sharing scheme in the HESS integrated WECs, the output power can be effectively smoothed out before supplying the power to the grid.

Design and Analysis of Sliding-Mode Artificial Neural Network Control Strategy for Hybrid PV-Battery-Supercapacitor System

Nowadays, the growing integration of renewable energy sources poses several challenges to electrical energy systems. The latter need be controlled by grid rules to ensure their stability and maintain the efficiency of renewable energy consumption. In this context, a novel HESS (hybrid energy storage system) control strategy, combining the PV (photovoltaic) generator with FLC (fuzzy logic control), SC (super-capacitor), and lithium-ion battery modules, is advanced. The proposed energy control rests on monitoring of the low-frequency and high-frequency electrical power components of the mismatch between power demand and generation, while applying the error component of the lithium-ion battery current. On accounting for the climatic condition and load variation considerations, the SC undertakes to momentarily absorb the high-frequency power component, while the low-frequency component is diverted to the lithium-ion battery. To improve the storage system’s performance, lifetime, and avoid load total disconnection during sudden variations, we consider equipping the envisioned energy control design with controllers of SM and ANN types. The MATLAB/Simulink based simulation results turn out to testify well the investigated HESS control scheme’s outstanding performance and efficiency in terms of DC bus voltage rapid regulation, thereby enhancing the battery’s lifetime and ensuring the PV system’s continuous flow.

Modified algorithm for automatic control of the mining harvester according to the load of the engine of the cutting drive

Purpose. To increase the productivity of the cutter-loader by creating a modified algorithm for automatic control of its speed with correction of stable power of cutting drive motors based on the results of statistical analysis of power during operation of the cutter-loader. Research methodology. As a research tool, a complex simulation model of the cutter-loader’scontrol system is used, which includes well-known mathematical models, describing the mining and geological properties of coal seams, as well as processes occurring in the structural elements of the cutter-loader. With the help of calculational experiments, the regularities of changes of statistical estimates of the power of the cutting drive engine for different mining and geological properties of the coal seam and the dynamics of the cutter-loader are established. The analysis of these regularities allowed to establish the dependence of the stable power of the cutting drive motor on the mining and geological parameters of the formation, and on their basis to propose a method of correction of the stable power during the working of the cutter-loader. A study of the effectiveness of the algorithm for automatic control of the speed of the cutter-loader using the proposed method in comparison with the existing algorithm. Research results. It is established, that the steady power of the cutting drive motor, corrected taking into account the standard deviation of the high-frequency component of the cutting drive motor power on a short section of the array, has a clearly determined deterministic component, which is determined by the change of resistance of coal to cutting along the coal seam. Also, steady power has a random component with the weight 15%, which is associated with the unpredictable oscillating nature of the movement of the cutter-loader, and with the complex and random nature of the process of destruction of the coal seam by the executive body. It is determined, that the double value of the standard deviation of the high-frequency power component of the cutting drive motor, as a power reserve, provides the percentage of exceeding by instantaneous power of allowable value, which is as close as possible to its acceptable level without exceeding it. Scientific novelty. For the first time, the dependence of the percentage of instantaneous power, exceeding its allowable value, on the coefficient of proportionality between the power margin and the standard deviation of the high-frequency power component under the condition of calculating the steady power of the cutting drive motor. This allowed us to determine the coefficient of proportionality, at which the percentage of cases of exceeding the instantaneous power of its permissible value is as close as possible to its acceptable level, but without exceeding it. Practical meaning. The method of correcting the stable power of the cutting drive motor during the operation of the cutter-loader is proposed. At the same time, the parameters of the algorithm for calculating the stable power of the cutting drive motor based on statistical processing of the values of the instantaneous motor power are substantiated.

Brain-Heart Link in Schizophrenia: Cognitive Inhibitory Control Deficit in Patients Is Specifically Related to Parasympathetic Dysregulation.

BackgroundThis study examined the connection between two prominent deficits in schizophrenia: the deficit in parasympathetic regulation and the deficit in cognitive inhibitory control, within the framework of the Neurovisceral Integration Model (NIM).Study DesignThirty healthy controls and 30 patients with schizophrenia performed the internationally standardized antisaccade protocol while their electrocardiographic data were recorded. The interaction between the group, the cognitive inhibitory control as measured with error rate (ER) in the antisaccade task and parasympathetic activity as measured with the High Frequency power component of Heart Rate Variability (HF-HRV) was tested.Study ResultsFindings confirmed that decreased HF-HRV was specifically related to increased ER in patients with schizophrenia. In contrast, patient deficits in other oculomotor function measures such as reaction time and reaction time variability related to volitional movement control and cognitive stability respectively were not linked to the deficit in parasympathetic regulation.ConclusionsOur study validates the theory behind NIM proposing that cognitive inhibition has common physiological substrate with parasympathetic regulation. Future research could test this brain-heart link in other mental disorders especially those with a prominent deficit in inhibitory cognitive function.

A Coordination Control between Battery and Supercapacitor Energy Storage Systems to Segregate Power for On-Grid Application

Abstract The present work describes a control methodology for a hybrid energy storage system (HESS) to improve its transient performance under dynamic load conditions. The proposed coordination control enhanced life cycle performance by segregating the power between battery energy storage systems (BESS) and a supercapacitor (SC). The BESS and SC are connected parallel to each other, and two individual DC–DC bidirectional converters connect them to a common DC bus. The coordination control is established between the controllers of BESS and the SC of HESS, which helps to utilise the usable energy capacity of the HESS. The charging/discharging current of the BESS is controlled within the allowable safety range based on the slope and magnitude of the BESS current. The high-frequency power component is handled by the SC, which helps to reduce the extra exhaustion on the BESS during operation with a higher current. The proposed coordination control of HESS is validated through simulation and the results show the effectiveness of the proposed controller.

Effects of Alzheimer's disease of varying severity on cardiac and autonomic function.

Alzheimer’s disease (AD) is one of the most common neurodegenerative diseases in the elderly. The aim of this study was to explore the effects of AD on cardiac function and autonomic nervous function, and the feasibility of electrocardiogram (ECG) in monitoring the development of AD. APP/PS1 double transgenic mice were used in the Morris water maze (MWM) experiment to evaluate the changes of cognitive ability of AD mice, then the non-invasive ECG acquisition system was used and the changes of ECG intervals and heart rate variability (HRV) were analyzed. AD mice already had cognitive dysfunction at the age of 5 months, reaching the level of mild dementia, and the degree of dementia increased with the course of disease. There were no significant changes in ECG intervals in the AD group at each month. The mean square of successive RR interval differences, percentage of intervals >6 ms different from preceding interval, and normalized high frequency power component in the AD group were decreased and low-to-high frequency power ratio and normalized low frequency power component were increased. Combined with the results of the MWM, it was shown that the regulation mechanism of sympathetic and parasympathetic nerves in mice was already imbalanced in early stage AD, which was manifested as the increase of excessive activity of sympathetic nerves and the inhibition of parasympathetic activities. Therefore, ECG-based analysis of HRV may become a means of daily monitoring of AD and provide an auxiliary basis for clinical diagnosis.

A Modular Multilevel Converter Topology With Novel Middle Submodules to Reduce Capacitor Voltage Fluctuations

This letter proposes a modified topology of modular multilevel converter for medium-voltage applications, which can reduce the ac-voltage fluctuation in the submodule (SM) capacitor at low-frequency operation. A novel structure of middle SM is inserted between the upper and lower arms, which has lesser count of components compared with the existing ones, leading to the reduction in cost and power losses. At the low operating frequency, furthermore, the middle SM can attenuate the power fluctuation in arms by distributing the high-frequency power components. Therefore, the SM capacitor voltage fluctuation is significantly alleviated without imposing the common-mode voltage on the ac side. The effectiveness of the proposed topology has been verified by experimental results.

GaN-Based Full-Bridge Converter With Digitally Adjustable Voltage Slopes for Characterization of Interwinding Insulation Properties of Magnetic High-Frequency Power Components

GaN-Based Full-Bridge Converter With Digitally Adjustable Voltage Slopes for Characterization of Interwinding Insulation Properties of Magnetic High-Frequency Power Components

Sugar‐Sweetened Soft Drink Consumption Acutely Modifies Cardiovascular Control in Healthy Adults

Long-term consumption of sugar-sweetened soft drinks is associated with an increased prevalence of cardiometabolic diseases. Previous reports demonstrate that consuming a bolus of fructose-sweetened water acutely increases blood pressure variability (BPV) and decreases spontaneous cardiovagal baroreflex sensitivity (cBRS) and heart rate variability (HRV). If caffeinated soft drinks containing high levels of fructose elicit similar responses is unknown. Objective Test the hypothesis that high-fructose corn syrup (HFCS) sweetened soft drink consumption increases BPV and decreases cBRS and HRV compared to water and artificially-sweetened (Diet) and sucrose-sweetened (Sucrose) soft drinks. Methods Twelve subjects (2 females; age 24 ± 4 y; body mass index: 24.1 ± 3.1 kg/m2) completed four randomized, double-blinded trials in which they drank 500 mL of water or commercially available soft drinks matched for taste and caffeine content (~77 mg). Subjects were not naïve to caffeine and consumed 346 ± 481 mL of soft drinks per week. We continuously measured beat-to-beat blood pressure (finger photoplethysmography) and R-R interval (ECG) before and 30 minutes after drink consumption during supine rest for 5 minutes during spontaneous and paced breathing (frequency of 15 breathes/minute). BPV was evaluated using standard deviation, average real variability, and successive variation methods for systolic and diastolic blood pressure. cBRS was assessed using the sequence method for up and down sequences. Overall cBRS was calculated as the average of up and down sequences. HRV was evaluated using the root mean square of successive differences in R-R interval (RMSSD) and the high frequency power component following power spectral density analysis (HF). Due to variation at baseline, data were analyzed as the magnitude of change (∆) from pre-drink consumption using a mixed-effects model with post hoc Sidak's test comparisons. Data are reported as mean ± SD. Results There were no differences between conditions for indices of BPV in standard deviation, average real variability, and successive variation during spontaneous and paced breathing (P≥0.07). Overall cBRS during spontaneous breathing was reduced in the HFCS (-3 ± 5 ms/mmHg) and Sucrose (-3 ± 5 ms/mmHg) trials compared to Water (+1 ± 5 ms/mmHg, P<0.03). Sucrose also elicited greater reductions in overall cBRS during spontaneous breathing compared to Diet (+1 ± 4 ms/mmHg, P=0.01) and HFCS was reduced during down sequences compared to Diet (-3 ± 5 vs. +2 ± 3 ms/mmHg, P=0.057). HFCS evoked greater reductions in RMSSD during paced breathing compared to Water (-26 ± 34 vs. +2 ± 26 ms, P<0.01), but not Diet (-11 ± 26 ms, P=0.43) nor Sucrose (-12 ± 11 ms, P=0.51). There were no differences in HF during paced breathing between HFCS and the other trials (Water: -408 ± 1178; Diet: -62 ± 1270; Sucrose: -871 ± 1549; HFCS: -155 ± 1505 ms2, P≥0.13). Conclusion These findings suggest that in healthy young adults, sugar-sweetened soft drink consumption acutely reduces cBRS and HRV but does not alter BPV.

How the first years of motherhood impact the cardiac autonomic profile of female healthcare professionals: a study by heart rate variability analysis

The conciliation between career and family is a relevant issue for working women, in particular during the first years of motherhood. Data about the state of the cardiac autonomic regulation in working women with preschoolers are lacking. Aim of this study was to compare the cardiac autonomic profile of female healthcare professionals with and without preschoolers via the analysis of the variability of the time distance between two consecutive R-wave peaks (RR) from standard 24-h Holter electrocardiogram (ECG). Fifty healthy active female healthcare professionals were enrolled: 25 with at least one preschooler (W_KID) and 25 without (W_NOKID). A standard Holter ECG was obtained during a regular working day. Segments of 5000 consecutive RRs were selected during daytime (DAY) and nighttime (NIGHT). Heart rate variability analysis was performed and the following parameters were considered for comparison between the two groups: mean (μRR), variance (σ2RR), and the absolute power in high frequency component (HF) of RR (HFRR) series. HFRR was considered as a marker of vagal cardiac modulation. Only µRR significantly increased from DAY to NIGHT in both groups (699 ± 88 vs 887 ± 140 ms in W_KID and 728 ± 90 vs 942 ± 166 ms in W_NOKID). Instead, σ2RR and HFRR increased from DAY to NIGHT only in W_NOKID (from 3334 ± 2153 to 4816 ± 4063 ms2 and from 356 ± 334 to 1397 ± 1629 ms2, respectively). W_KID showed lower σ2RR and HFRR during NIGHT, compared to W_NOKID (2336 ± 3170 vs 4816 ± 4063 ms2 and 556 ± 950 vs 1397 ± 1629 ms2, respectively). The perceived stress according to the visual analogue scale was similar in the two groups (4.7 ± 2.1 in W_KID, 5.7 ± 2.1 in W_NOKID). The presence of preschoolers lowered nocturnal cardiac vagal modulation in female healthcare professionals. This might represent an adaptation with a finalistic purpose, scilicet the facilitation of a prompt reaction in case of a child’s need.

Comparison of Morning Heart Rate Variability at the Beginning and End of a Competition Season in Elite Speed Skaters.

The aim of this study was to clarify whether the physiological fatigue status of elite speed skaters is influenced by the approximately five-month international competition season by comparing morning heart rate variability (HRV) at the beginning of the competition season (Japan Single Distances Championships: JSDC) with that at the end of the competition season (World Single Distances Championships: WSDC). Five international-class speed skaters participated in the study. HRV indices and subjective fatigue were measured each morning of the four days prior to the first races of the JSDC and WSDC in the 2007/2008 season. The parasympathetic HRV indices: root mean square of the successive R-R interval differences (RMSSD) (JSDC, 61.0 ms; WSDC, 42.1 ms; p < 0.05), high-frequency component power (HF) (JSDC, 1393 ms2; WSDC, 443 ms2; p < 0.05), and normalized unit of HF (HFnu) (JSDC, 53.2%; WSDC, 25.5%; p < 0.05) were lower for the WSDC than for the JSDC. The decrease in these indices may reflect the skaters’ accumulated fatigue during the course of the competition season. Morning measurements of HRV may thus be an efficient way for elite speed skaters and coaches to objectively monitor physiological fatigue throughout the competition season.

Morning Heart Rate Variability as an Indication of Fatigue Status in Badminton Players during a Training Camp.

This study aimed to clarify whether changes in the fatigue status of elite athletes during a precompetition period could be evaluated using morning heart rate variability (HRV) indices. Eight Japanese National Badminton Team players (age, 23.0 ± 2.8 years) participated in this study. HRV and subjective fatigue were measured during the first (days 1–4: Phase 1) and the second half (days 5–8: Phase 2) of an 8-day national team training camp. The global and parasympathetic HRV indices were as follows: standard deviation of all R-R intervals (SDNN) (Phase 1, 87.5 ms; Phase 2, 104.3 ms; p < 0.05), root mean square of the successive R-R interval differences (RMSSD) (Phase 1, 66.6 ms; Phase 2, 103.6 ms; p < 0.05), and high-frequency component power (HF) (Phase 1, 1412.0 ms2; Phase 2, 3318.5 ms2; p < 0.05). All the aforementioned indices increased significantly from Phase 1 to Phase 2. Significant correlations were observed between the change in subjective fatigue and changes in SDNN, RMSSD, and HF (ρ = −0.80, p = 0.017; ρ = −0.77, p = 0.027; and ρ = −0.80, p = 0.017, respectively). Measuring morning HRV indices may be effective for objectively evaluating changes in the fatigue status of elite athletes during a precompetition period.

Cognitive Demand and Accommodative Microfluctuations.

Previous studies have shown cognition to have an influence on accommodation. Temporal variation in the accommodative response occurs during the fixation on a stationary target. This constantly shifting response has been called accommodative micro-fluctuations (AMFs). The aim of this study is to determine the effects of increasing task cognitive demand on the ocular accommodation response. AMFs for 12 myopes and 12 emmetropes were measured under three conditions of varying cognitive demand and comprising reading of numbers (Num), simple arithmetic (SA), and complex arithmetic (CA). Fast Fourier transforms were used to analyze the different frequency band components of the AMFs. Other aspects of AMFs including root mean square accommodation values and chaos analysis was applied. A repeated measures ANOVA revealed a significant main effect of cognition in the mean power of the high frequency component (HFC) (F2,44 = 10.03, p < 0.005). Pairwise analyses revealed that these differences exist between SA and CA tasks (p < 0.005) and the Num and CA (p < 0.005) tasks with the HFC power being the highest for the CA condition. It appears that the difficulty of a task does affect active accommodation but to a lesser extent than other factors affecting accommodation.

Rule-based energy management for dual-source electric buses extracted by wavelet transform

Abstract This paper aims at studying the energy management of the dual-source electric bus. Based on the characteristics of the power demand and the energy storage system of the dual-source electric bus, a rule-based control strategy based on wavelet transform is proposed to allocate the energy flow among the energy units to obtain efficient energy transfer. The high and low frequency component power demand are decomposed and reconstructed by wavelet transform theory. The high frequency component power is assigned to the super capacitor, and the low frequency one is assigned to the battery pack or power grid, which can obviously reduce the damage, caused by the power rapid change and surge load, to the battery pack and power grid. The effectiveness of the proposed method is evaluated by the benchmark solved by dynamic programming under both a real driving cycle and the standard China bus driving cycle. Simulation experiments are carried out and the results show that the average power consumption is 0.9335 kWh/km, which has only a difference of 8.25% compared with the benchmark under a real driving cycle. In addition, a 9.02% difference is realized under the standard China bus driving cycle. Finally, the hardware-in-loop experiment is performed and the results show that the proposed strategy is reasonable.

Single Osteopathic Manipulative Therapy Session Dampens Acute Autonomic and Neuroendocrine Responses to Mental Stress in Healthy Male Participants.

The efficacy of osteopathic manipulative therapy (OMTh; manipulative care provided by foreign-trained osteopaths) is supported by observational data and patient feedback, but there is still a need for objective, quantitative biomarkers that allow measurement of the underlying mechanisms. No study exploring the protective potential of OMTh for mental stress has been published, to the authors' knowledge. To explore the modulating effect of OMTh on autonomic neural regulation of the heart and verifiy its ability to influence the activity of the hypothalmic-pituitary-adrenocortical axis. Healthy young adult men who had never received OMTh were exposed to either a brief protocol using craniosacral techniques or sham therapy (control) involving the same anatomical areas. A laboratory stress episode consisting of a 5-minute arithmetic task participants were required to perform in front of a committee preceded the therapy sessions. Continuous electrocardiograph recordings were done before, during, and after the stress episode. Heart rate and frequency-domain parameters of heart rate variability (specifically, high-frequency component power in normalized units and the ratio of low-frequency to high-frequency power) were measured to quantify the activity of the parasympathetic nervous system and the state of sympathovagal balance at the level of the heart, respectively. Saliva samples were also collected at points throughout the study to determine cortisol levels. Osteopathic manipulative therapy reduced the overall chronotropic effect of the stressor (t=-2.9, P<.05) and counteracted the vagal withdrawal and the shift of autonomic balance toward sympathetic prevalence (t=-2.8, P<.05) that were observed in control participants. Moreover, OMTh participants had a much lower overall cortisol level during the mental stressor compared with control participants (t=-2.3, P<.05). Participants in the OMTh group did not show the statistically significant reduction in the amplitude of the cortisol awakening response observed in their control counterparts after the stress episode (control: t=2.7, P<.05; OMT: P=.83). The application of a single OMTh session to healthy participants induced a faster recovery of heart rate and sympathovagal balance after an acute mental stressor by substantially dampening parasympathetic withdrawal and sympathetic prevalence. The OMTh session also prevented the typical increase in cortisol levels observed immediately after a brief mental challenge.

Effect of a 16-week Bikram yoga program on heart rate variability and associated cardiovascular disease risk factors in stressed and sedentary adults: A randomized controlled trial

BackgroundChronic activation of the stress-response can contribute to cardiovascular disease risk, particularly in sedentary individuals. This study investigated the effect of a Bikram yoga intervention on the high frequency power component of heart rate variability (HRV) and associated cardiovascular disease (CVD) risk factors (i.e. additional domains of HRV, hemodynamic, hematologic, anthropometric and body composition outcome measures) in stressed and sedentary adults.MethodsEligible adults were randomized to an experimental group (n = 29) or a no treatment control group (n = 34). Experimental group participants were instructed to attend three to five supervised Bikram yoga classes per week for 16 weeks at local studios. Outcome measures were assessed at baseline (week 0) and completion (week 17).ResultsSixty-three adults (37.2 ± 10.8 years, 79% women) were included in the intention-to-treat analysis. The experimental group attended 27 ± 18 classes. Analyses of covariance revealed no significant change in the high-frequency component of HRV (p = 0.912, partial η2 = 0.000) or in any secondary outcome measure between groups over time. However, regression analyses revealed that higher attendance in the experimental group was associated with significant reductions in diastolic blood pressure (p = 0.039; partial η2 = 0.154), body fat percentage (p = 0.001, partial η2 = 0.379), fat mass (p = 0.003, partial η2 = 0.294) and body mass index (p = 0.05, partial η2 = 0.139).ConclusionsA 16-week Bikram yoga program did not increase the high frequency power component of HRV or any other CVD risk factors investigated. As revealed by post hoc analyses, low adherence likely contributed to the null effects. Future studies are required to address barriers to adherence to better elucidate the dose-response effects of Bikram yoga practice as a medium to lower stress-related CVD risk.Trial registrationRetrospectively registered with Australia New Zealand Clinical Trials Registry ACTRN12616000867493. Registered 04 July 2016.

Post-surgical heart rate variability in patients with brain tumor and epileptic seizures

Aim. To identify post-surgical perculiarities of heart rate variability in patients with brain tumors and symptomatic epilepsy.Methods. The study group consisted of 85 patients (43 males and 42 females) aged 22 to 83 years admitted to neurosurgical department of Ryazan regional clinical hospital with brain tumor. The control group consisted of 20 relatively healthy individuals. The study group was divided into 2 subgroups of patients with brain tumor associated with symptomatic epilepsy and brain tumors without epileptic seizures. Five-minute ECGs in 3 functional probes (baseline, hyperventilation and post-hyperventilation) before and after craniotomy with tumor resection were recorded. The following statistical analysis of time and frequency parameters of heart rate variability was performed.Results. Statistically significant differences in heart rate variability in pre- and post-surgical periods were found only in patients with epilepsy syndrome caused by brain tumor: mode increased by 11% in baseline and post-hyperventilation probes. Coefficient of variation and standard deviation were decreased by 29% in hyperventilation probe, index of centralization decreased by 60% in baseline probe and by 42% in post-hyperventilation probe. Statistically significant increase of high frequency power component by 46% was registered after surgical intervention in baseline probe and by 10% in post-hyperventilation probe. As opposed to this in the subgroup of patients with brain tumors and without epilepsy this parameter decresed by 10% in baseline probe.Conclusion. The obtained results demonstrate significant post-surgical improvement of autonomic nervous system homeostasis and restoration of cardiovascular functional reserves in patients with brain tumor associated with epilepsy compared to those with no epileptic seizures.

Cerebral and neural regulation of cardiovascular activity during mental stress.

BackgroundMental arithmetic has been verified inducing cerebral and cardiovascular responses. However, the mechanism and sequential responses are still ambiguous. This study aims to reveal the mechanism of cardiovascular and autonomic responses and the related scalp positions that regulate the autonomic nerves system (ANS) during MA task.Methods34 healthy male subjects aged between 19 and 27 years old (mean age 23.6 ± 2.3 years) were recruited in. Electrocardiogram, impedance cardiography, beat-to-beat blood pressure and electroencephalography were measured simultaneously and continuously during the experiments. And the analysis of time–frequency, approximate entropy and Pearson correlation coefficient were adopted. For statistical comparison, paired t test is utilized in the study.ResultsThe results showed that mental arithmetic task increased heart rate (from 72.35 ± 1.88 to 80.38 ± 2.34), blood pressure (systolic blood pressure: from 112.09 ± 3.23 to 126.79 ± 3.44; diastolic blood pressure: from 74.15 ± 1.93 to 81.20 ± 1.97), and cardiac output (from 8.71 ± 0.30 to 9.68 ± 0.35), and the mental arithmetic induced physiological responses could be divided into two stages, the first stage (10–110 s) and late stage (150–250 s). The high frequency power component (HF) of HRV decreased during MA, but the normalized low frequency power component (nLF) and LF/HF ratio of HRV increased only at the late stage. Moreover, during first stage, the correlations between approximate entropy of electroencephalography at Fp2, Fz, F4, F7 and the corresponding time–frequency results of HF were significant. During the late stage, the correlations between approximate entropy of electroencephalography at Fp2, Fz, C3, C4 and the corresponding nLF was significant.ConclusionsOur results demonstrated that (1) mental stress induces time-dependent ANS activity and cardiovascular response. (2) Parasympathetic activity is lower during mental arithmetic task, but sympathetic nerve is activated only during late stage of mental arithmetic task. (3) Brain influences the cardiac activity through prefrontal and temporal cortex with the activation of ANS during mental arithmetic.