226 research outputs found
AN IMPACT-BASED PIEZOELECTRIC ENERGY HARVESTER UTILIZING SPHERICAL MASS COLLISION PHENOMENON
The base-excitation piezoelectric energy harvesters have been vastly investigated under periodic base excitation as a conventional method. However, the waveforms of environment’s vibrations are mostly non-harmonic low-frequency periodic signals that reduce the efficiency of the harmonic-based resonance harvester. This study presents an alternative piezoelectric energy generation, the impact-based piezoelectric energy harvester concept rather than the typical harmonic-based one. The harvester benefits from impact excitation, leading to higher frequencies around the harvester’s natural frequencies. The impact concept is utilized for energy harvesting based on contact between a piezoelectric patch and a miniatured spherical mass. An experimental study was carried out to evaluate the effects of impact velocity and boundary condition on the dynamic behavior and power generation of the piezoelectric energy harvester. Moreover, a finite element model implemented a feasible framework to investigate the output power of the energy harvester under various impact forces. The results demonstrated μJ-scale energy generation by a single impact, indicating great energy generation possibilities for ultra-low-frequencies. The results also indicated that the boundary condition plays a critical role in energy harvesting, affecting the probability of voltage cancelation phenomenon occurrence. It was shown that the optimal boundary condition decreases the negative effects of voltage cancelation to improve the performance of the impact-based energy harvester
Harnessing cardiac power: heart kinetic motion analysis for energy harvesters
Accurately estimating the complex motion of the heart can unlock enormous
potential for kinetic energy harvesting. This paper presents a foundational
dataset for heart kinetic motion through in-vivo tests and investigates the
most influential factors in heart kinetic motion. In-vivo tests on a living
pig's heart, with signal processing, were carried out to study the heart
movement by heart beating and respiration motions. A network of nine points on
the heart was employed for in vivo measurements. These measurements illustrated
the kinetic energy signals in displacement, velocity, and acceleration. The
results indicated that the motion level varies in distinct locations over
epicardium. The statistical features and autocorrelations were reported for
these points, illustrating the highest displacement and acceleration. Each
heartbeat generated an energy of 14.35 mJ and a power of 1.03 W. However, this
available energy is not uniformly distributed. The results illustrated that not
only is cardiac movement location-dependent, but the speed of cardiac
displacement cycles is also location-dependent. The right atrium has the
highest cardiac kinetic movement with an amplitude of 16.19 mm displacement and
16.3 m/s2 acceleration. To evaluate the energy harvesting possibility from the
heart's motion, a piezoelectric energy harvester was simulated by the finite
element method, implying that the energy harvesting level significantly depends
on implant location over epicardium. The results of this study open the
potential of designing novel energy harvesters based on accurate heart
movements and provide a foundation for future investigations of energy
harvesting for leadless pacemaker energy systems
Effects of Marine n-3 Fatty Acids on Heart Rate Variability and Arrhythmias in Patients Receiving Chronic Dialysis (Renal Rhythm Stdy II) - Rationale and Design
Is the Pattern Changing?:Atrial Fibrillation and Screening with Holter Electrocardiograms among Ischemic Stroke Patients in Greenland from 2016 to 2021
A standardized examination regime for ischemic stroke (IS) patients was implemented in Greenland in 2010. Prevalence of atrial fibrillation (AF) of 32% was found among discharged IS patients from 2011 to 2012, and our study aims to estimate the use of Holter ECGs for AF diagnostics and the current prevalence of AF among IS patients in Greenland. Patients discharged from Queen Ingrid’s Hospital in Nuuk between 2016 and 2021 with an ICD-10 diagnosis of IS or stroke without specification were included. Data on Holter recordings, age, gender, medical treatment with rivaroxaban or warfarin, and ICD-10 and ICPC codes for AF were extracted for each patient. The overall incidence of IS from 2016 to 2021 was 133/100,000 and unchanged since 2012. Sixty-eight of the study’s IS patients (14.5%) had AF, and 46% of IS patients with Holter data accessible had a recording according to international recommendations. Our results indicate that fewer IS patients in Greenland have AF than previously. However, the insufficient use of Holter as a diagnostic tool may explain part of the drop, as well as improved preventive treatment with rivaroxaban among AF patients in Greenland. Regardless, IS remains common, and a focus on diagnostics and preventable risk factors should be maintained
Marine <i>n</i>-3 PUFA, heart rate variability and ventricular arrhythmias in patients on chronic dialysis:a cross-sectional study
AbstractMarine n-3 PUFA may improve autonomic dysfunction by an increase in heart rate variability (HRV) and may reduce the risk of malignant ventricular arrhythmias. Only a few smaller studies have examined such effects in patients on chronic dialysis, who often have autonomic dysfunction and a high risk of sudden cardiac death, which accounts for almost 30 % of all deaths. This cross-sectional study investigated the association between the plasma phospholipid content of n-3 PUFA and 24-h HRV or ventricular arrhythmias in patients on chronic dialysis. A 48-h Holter monitoring was performed on 169 patients on in-centre dialysis (83 %), home haemodialysis (10 %) or peritoneal dialysis (7 %) obtaining data on arrhythmias (n 152) and 24-h HRV (n 135). The mean overall HRV (standard deviation of normal intervals (SDNN)) was low and 71 % had a reduced overall HRV (SDNN<100 ms) indicating autonomic dysfunction. No significant associations between plasma phospholipid content of total marine n-3 PUFA, EPA (22 : 5n-3) or DHA (22 : 6n-3) and time-domain or frequency-domain HRV were detected in crude or adjusted linear regression analysis. However, a higher plasma phospholipid content of DHA was associated with a significantly lower proportion of patients with ventricular tachycardia (higher DHA-tertile: 9 % v. lower DHA-tertile: 28 %, P=0·02). In conclusion, the content of marine n-3 PUFA in plasma phospholipids was not associated with 24-h HRV, but a higher plasma phospholipid content of DHA was associated with a lower occurrence of ventricular tachycardia suggesting an antiarrhythmic effect of marine n-3 PUFA in patients on chronic dialysis.</jats:p
Moderate consumption of marine n-3 fatty acids is associated with a lower risk of atrial fibrillation – a Danish cohort study
Mortality and risk of cardiac complications among immediate survivors of accidental electric shock:a Danish nationwide cohort study
Using the C<sub>2</sub>HEST score for predicting postoperative atrial fibrillation after cardiac surgery: A report from the Western Denmark Heart Registry, the Danish National Patient Registry, and the Danish National Prescription Registry
ObjectivesNew-onset postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery. A targeted approach is necessary for prophylactic handling of the complication. The authors tested the performance of the C2HEST score to predict POAF in patients undergoing cardiac surgery.DesignRegister-based cohort study.SettingThree cardiothoracic centers.ParticipantsAll adult patients undergoing cardiac surgery in Western Denmark between January 1, 2010, and December 31, 2018, were included. Data on patient comorbidities before surgery were obtained from the Western Denmark Heart Registry, the Danish National Patient Registry, and the Danish National Prescription Registry.InterventionsThe C2HEST score (C2: Coronary Artery Disease/Chronic Obstructive Pulmonary Disease [1 point each]; H: Hypertension; E: Elderly [Age ≥75, 2 points]; S: Systolic Heart Failure [2 points]; T: Thyroid disease [hyperthyroidism]) was calculated for each patient. The primary outcome was POAF within the primary hospital stay. The C2HEST score's discriminative ability was evaluated and compared with an age-stratified version (mC2HEST) as well as 2 validated clinical risk models (CHADS2 and CHA2DS2-VASc).Measurements and main resultsAmong the 14,279 patients included, 4,298 (30.1%) developed POAF. The C2HEST score's performance was not significantly better than the CHADS2 and CHA2DS2-VASc scores (area under the curve [AUC] 0.553 [95% confidence interval {CI} 0.543; 0.563] v 0.543 [95% CI 0.535; 0.552] and 0.565 [95% CI 0.555; 0.574], respectively). The age-modified (mC2HEST) score showed only modest improvement in the risk model, with an AUC of 0.580 (95% CI 0.570; 0.590).ConclusionThe discriminative ability of the C2HEST score, measured by the AUC, was limited in this population, and was not proven to be superior to the CHADS2, CHA2DS2-VASc, and mC2HEST scores in predicting POAF after cardiac surgery
U-Shaped Association Between Consumption of Marine n-3 Fatty Acids and Development of Atrial Fibrillation:a Danish Cohort Study
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