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Introduction: Circulating branched chain amino acid (BCAA) levels are associated with the development of diabetes mellitus (DM) and downstream ASCVD in middle-aged women. It is unknown if BCAAs in young adult men and women are associated with ASCVD events. BCAA levels may be dynamic in middle-aged adults prior to the development of DM or ASCVD events, thus cumulative BCAA measures in early life may better quantify exposure risk than a single measure at mid-life. Methods: We measured plasma BCAA levels in 3110 Coronary Artery Risk Development in Young Adults study participants using nuclear magnetic resonance (NMR) at Years (y) 2, 7, 15, and 20. To minimize missingness bias, BCAA levels were imputed for the residual 1835 participants without NMR measures. Cumulative BCAA exposure from 19-40y of age was calculated as the area under the curve using a spline-based mixed-effects model to estimate subject-specific BCAA trajectories from 19-40y. Sex-specific associations between cumulative BCAA exposure and incident ASCVD events after 40y of age were assessed by multivariable (Table) Cox proportional hazards regression models including BCAA levels and fasting blood glucose (FBG) at age 40y and further stratified by DM status. Results: Among 4945 participants (55.3% female), there were 255 ASCVD events and 675 DM cases over a median of 18.8 years of follow-up after age 40y. In adjusted models, cumulative BCAA exposure from 19-40y was associated with ASCVD events after 40y of age in women, but not men (Table). The associations in women were robust to adjustment for BCAAs and FBG at age 40y. There was no significant difference in the cumulative BCAA-ASCVD association among men or women who developed DM before ASCVD versus those who did not. Conclusions: Cumulative BCAA exposure in early adulthood is associated with ASCVD in women independent of mid-life BCAA levels. Elevated BCAA levels in women during early adulthood may reflect behaviors and/or metabolic pathways that increase risks for ASCVD independent of the development of hyperglycemia.

Introduction: HDL particles vary in size and concentration. Indices of overall HDL particle concentration (HDL-P) and the concentrations of different HDL size subspecies (small: H1-H3, medium: H4, H5, and large: H6, H7) have differential associations with near-term CVD events in middle-aged adults. It is unclear if measures of HDL particle concentration predict long-term ASCVD risk in young adults. Methods: Among CARDIA participants (ppts), NMR was used to measure HDL-P and HDL particle size subgroup H1-H7 concentrations. HDL cholesterol (HDL-C) was measured using standard assays. We stratified the ppts into 2 age windows: 20-30y (n= 1645) and 30-40y (n=2922). We used adjusted Cox proportional hazards models to assess the associations between a 1SD higher HDL-C, HDL-P, and HDL1-7 subgroups with incident ASCVD events. We added HDL-P, HDL H1-H7, and HDL-C separately to a modified Pooled Cohort Equation (PCE) model; model performance (discrimination and reclassification) was evaluated. Results: 81 and 163 ASCVD events occurred over (median (IQR)) 31.8y (31.1-32.0y) for the 20-30y age window and over 26.8y (19.1-27.1y) for the 30-40y age window, respectively. In ppts age 20-30y, a higher HDL-P and HDL-C were not associated with ASCVD events, however a higher HDL H6 subgroup level was associated with lower risk for ASCVD in demographic adjusted models. In the age 30-40y group, higher HDL-P, HDL-C, and H6 subgroup were significantly associated with lower ASCVD risks in all models. There were no significant differences in c-statistics across PCE models. However, there were improvements in reclassification for all HDL measures when added to the PCE model in the 20-30y age window, and significant improvements in reclassification when HDL H1-7 were added to the PCE for the 30-40y age window. Conclusion: At younger ages (

Introduction: Measures of atherogenic particle number (apoB and LDL particle number [LDL-P]) are stronger predictors of atherosclerotic cardiovascular disease (ASCVD) risk than measures of cholesterol concentration (LDL-C, non-HDL-C, total cholesterol [TC]) in middle-aged adults. It is unclear if this is true for younger adults. Methods: Among CARDIA participants (ppts), NMR was used to measure apoB and LDL-P. Non-HDL-C and TC were measured using standard assays; LDL-C was calculated using the Friedewald equation. We stratified the ppts into two age windows: age 20-30y (n=1645) and age 30-40y (n=2922). We used adjusted Cox proportional hazards models to assess the associations of 1SD higher apoB, LDL-P, non-HDL-C, LDL-C, or TC with incident ASCVD events. We substituted each measure of atherogenic lipid burden for TC in a modified Pooled Cohort Equation (PCE) model (with and without HDL-C); and model performance (discrimination and reclassification) was evaluated. Results: There were 81 and 163 ASCVD events over (median [IQR]) 31.8y (31.1-32.0y) for the age 20-30 age window and over 26.8y (19.1-27.1y) for the 30-40y age window, respectively. In ppts age 20-30y, a 1SD higher apoB, LDL-P, non-HDL-C, and LDL-C were significantly associated with incident ASCVD in demographic adjusted models. The strengths of associations with ASCVD were not significantly different across these measures. For the 30-40y age window, all measures of atherogenic lipoproteins were significantly associated with ASCVD; the strengths of association were not significantly different across atherogenic lipid measures in all models. There were no significant differences in the C-statistic and no improvement in reclassification when each measure was used to replace TC in the PCE model. Conclusions: ApoB, LDL-P, LDL-C or non-HDL-C may be slightly better markers of long-term ASCVD risk than TC in adults < 30y. However, in adults between 30-40y all measures of atherogenic lipid burden appeared to be equivalent predictors of long-term risk.

Iron is essential to the production of myocardial energy and proteins critical for cardiovascular function. Nearly 50% of patients with heart failure with reduced ejection fraction (HFrEF) meet current criteria for iron deficiency, and there has been considerable interest in intravenous repletion of iron stores as a therapeutic strategy to improve HFrEF outcomes. However, the data on intravenous iron therapy in HFrEF have been mixed.

Genetic variation in genes regulating metabolism may be advantageous in some settings but not others. The non-failing adult heart relies heavily on fatty acids as a fuel substrate and source of ATP. In contrast, the failing heart favors glucose as a fuel source. A bootstrap analysis for genes with deviant allele frequencies in cardiomyopathy cases versus controls identified the MTCH2 gene as having unusual variation. MTCH2 encodes an outer mitochondrial membrane protein, and prior genome-wide studies associated MTCH2 variants with body mass index, consistent with its role in metabolism. We identified the referent allele of rs1064608 (p.Pro290) as being overrepresented in cardiomyopathy cases compared to controls, and linkage disequilibrium analysis associated this variant with the MTCH2 cis eQTL rs10838738 and lower MTCH2 expression. To evaluate MTCH2, we knocked down Mtch in Drosophila heart tubes which produced a dilated and poorly functioning heart tube, reduced adiposity and shortened life span. Cardiac Mtch mutants generated more lactate at baseline, and they displayed impaired oxygen consumption in the presence of glucose but not palmitate. Treatment of cardiac Mtch mutants with dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, reduced lactate and rescued lifespan. Deletion of MTCH2 in human cells similarly impaired oxygen consumption in the presence of glucose but not fatty acids. These data support a model in which MTCH2 reduction may be favorable when fatty acids are the major fuel source, favoring lean body mass. However, in settings like heart failure, where the heart shifts toward using more glucose, reduction of MTCH2 is maladaptive.

One of the performance-limiting factors in the design of robust controllers for active magnetic bearing systems is the fact that the controller needs to be robust to the gyroscopic effects, that is rotational speed-dependent dynamics of the system. Studies in the literature show that better performance and stability can be achieved when gyroscopic effects are explicitly handled by a cross-feedback control for rigid rotor-active magnetic bearing systems. For flexible rotor-active magnetic bearing systems, gyroscopic effects are mainly dealt by defining the rotational speed as an uncertain parameter of the model or with linear parameter-varying controllers. This study explores the novel idea of compensating gyroscopic effects of a flexible rotor-active magnetic bearing system with an add-on controller and investigates its effects on the achieved performance of μ-controllers. The study is carried out on an experimental active magnetic bearing test rig with relatively high gyroscopic effects. An add-on controller is designed to compensate the gyroscopic effects of the first and second flexible modes of the rotor. Two μ-controllers are designed for the system: (1) benchmark controller that is designed using a standard control approach for active magnetic bearing systems and (2) controller designed with a modified model of the system in which the gyroscopic effects for the first and second flexible modes are reduced because of the presence of the add-on controller. Both controllers are implemented, and their performances are compared for initial levitation, run-up test from 0 to 10,000 r/min, orbit sizes at various speeds, and the computational cost of implementing each controller. The results suggest that better performance is potentially possible at the cost of significant increase in the computational complexity of the controller.

Vasospastic angina is an uncommon cause of cardiac arrest. We describe a patient who presented with sudden cardiac arrest due to severe coronary vasospasm. Telemetry during the event revealed ventricular arrhythmias and asystole followed by spontaneous self-conversion back to normal sinus rhythm. The patient underwent implantable cardioverter-defibrillator therapy. (Level of Difficulty: Beginner.).

The aim of this study was to determine the profile of phenolic acids and flavonoids in red beetroot products and these compounds fate in the human body after long-term exposure to fermented red beet juice. Phenolic acids and flavonoids were analyzed by HPLC-MS/MS. The performed analysis revealed that beetroot and its products were the notable sources of phenolic acids and flavonoids, with isoferulic acid, protocatechuic acid, epicatechin, and apigenin predominating among the twenty compounds detected. However, the compounds analyzed appeared mainly in the bound form in the fresh material. The results obtained indicate that the fermentation process caused an increase in the content of free phenolic acids and reduced the content of conjugated phenolic acids. Contrarily to phenolic acids, the same process caused a reduction in the content of free flavonoids and an increase in the content of conjugated flavonoids. Moreover, the 14-day spontaneous fermentation process resulted in a significant reduction (by 45.18%) in the total content of phenolics (phenolic acids and flavonoids). However, it was observed that forty-two days of the regular intake of the fermented beetroot juice (200 mL/60 kg body weight) generally did not affect concentrations of phenolic acids and flavonoids in the volunteers' body fluids compared to their concentrations in fluids before fermented beetroot juice consumption.

Hybrid zero dynamics (HZD) control creates dynamically stable gaits by driving a hybrid robot model toward an optimally generated state-dependent reference signal. This paper presents the first application of HZD to an underactuated lower-limb exoskeleton for gait guidance. A phase-based reference gait is generated to follow a nominal walking pattern. Simulation results using a phase-based proportional-derivative (PD) controller validate that stable periodic gait similar to nominal gait is possible for the identified human-exoskeleton model. For hardware application, a bilateral mixing strategy is taken to accommodate the presence of the double support phase, which was assumed to be instantaneous in the hybrid model. A treadmill experiment is conducted with a healthy subject using the Indego Explorer exoskeleton. Comparing the recorded gait to the optimal phase-based reference, the root-mean-square joint tracking errors (RMSE) are 2.87 deg, 2.79 deg, 3.20 deg, and 11.0 deg at the stance hip, stance knee, swing hip, and swing knee, respectively. Similarly, compared to the commanded reference, the RMSE are 2.04 deg, 4.40 deg, 4.58 deg, and 6.83 deg, respectively. A second experiment was conducted wherein the treadmill speed varied from 0.3 to 0.5 m/s. The results show how the HZD controller exhibits remarkable flexibility and robustness for multiple walking speeds and grants the operator greater level of volitional control due to the time-invariant, phase-based nature of the implementation. Taken altogether, the presented results suggest that HZD control can serve as a rehabilitative control method capable of providing gait guidance in underactuated exoskeleton systems.

Generalized multiple-input-multiple-output (MIMO) controllers such as H∞ and μ have not been widely adopted in the magnetic bearing industry, partially due to high computational cost relative to simpler single-input-single-output schemes. Computational cost is important to industrial magnetic bearing vendors as their controller hardware is based on embedded processors that have limited bandwidth. Studies to mitigate the problem of high-order controllers show the limit of the existing methods in order reduction while still maintaining satisfying robust performance. A novel method is proposed to reduce the computational cost of robust controllers by identifying bounds in their dynamic response, such that an implementation of a controller within those bounds results in the robust performance. The bounds are used to develop two computational cost reduction schemes for controller implementation, i.e., (1) identifying a dual-rate implementation of a single-rate controller which uniformly reduces the computational cost via interlacing technique, and (2) redesign of a controller by identifying its negligible dynamics based on the identified bounds in the controllers' dynamic response. The results of both approaches are demonstrated on two active magnetic bearing (AMB) systems, a model of a 300 kW turbine generator with permanent magnet biased AMBs, and an experimental high-speed AMB machining spindle. μ-synthesis controllers are designed for both systems, and the proposed method and schemes are applied accordingly. The comparison of standard implementations of the synthesized controllers and the proposed new implementations is presented. The results demonstrate considerable reduction in the computational cost in terms of required number of multiply accumulate (MAC) operations.

Background Inhibitors of the sodium-glucose linked transporter 2 improve cardiovascular outcomes in patients with or without type 2 diabetes mellitus, but the effects on cardiac energetics and mitochondrial function are unknown. We assessed the effects of sodium-glucose linked transporter 2 inhibition on mitochondrial function, high-energy phosphates, and genes encoding mitochondrial proteins in hearts of mice with and without diet-induced diabetic cardiomyopathy. Methods and Results Mice fed a control diet or a high-fat, high-sucrose diet received ertugliflozin mixed with the diet (0.5 mg/g of diet) for 4 months. Isolated mitochondria were assessed for functional capacity. High-energy phosphates were assessed by

Adrenal insufficiency is a rare cause of heart failure. We describe a young patient who presented with new-onset biventricular systolic heart failure due to primary adrenal insufficiency. The patient was initiated on hydrocortisone, with rapid improvement of both left and right ventricular systolic function. (Level of Difficulty: Beginner.).

This paper presents a novel impedance controller modified with a switching strategy for the purpose of improving safety in human–robot interactions. Under normal operating conditions, an impedance controller is enabled when adequate tracking performance is maintained in the presence of bounded disturbances. However, if disturbances are greater than anticipated such that tracking performance is degraded, the proposed controller temporarily switches modes to a control strategy better apt to limit control inputs. With disturbances returning to the prescribed bounds, tracking performance will be restored and the impedance controller will resume for nominal operation. The control parameters are constrained by a few conditions necessary for smooth operation. First, a pair of equality constraints is required for the control signal to be continuous when switching control modes. Second, a Lyapunov analysis is performed to formulate an equality constraint on the control parameters to ensure only a single switch occurs when changing control modes to avert control chatter. Third, a matrix inequality constraint is necessary to ensure a robust positive invariant set is formed for when impedance control is active. Numerical simulations are provided to illustrate the controller and conditions. The simulation results successfully validate the presented theory, demonstrating how the constraints yield a continuous control signal, eliminate switching chatter, and permit robustness to disturbances.

Chronic loss of Augmenter of Liver Regeneration (ALR) results in mitochondrial myopathy with cataracts; however, the mechanism for this disorder remains unclear. Here, we demonstrate that loss of ALR, a principal component of the MIA40/ALR protein import pathway, results in impaired cytosolic Fe/S cluster biogenesis in mammalian cells. Mechanistically, MIA40/ALR facilitates the mitochondrial import of ATP-binding cassette (ABC)-B8, an inner mitochondrial membrane protein required for cytoplasmic Fe/S cluster maturation, through physical interaction with ABCB8. Downregulation of ALR impairs mitochondrial ABCB8 import, reduces cytoplasmic Fe/S cluster maturation, and increases cellular iron through the iron regulatory protein-iron response element system. Our finding thus provides a mechanistic link between MIA40/ALR import machinery and cytosolic Fe/S cluster maturation through the mitochondrial import of ABCB8, and offers a potential explanation for the pathology seen in patients with ALR mutations.

Anthracyclines are the cornerstone of many chemotherapy regimens for a variety of cancers. Unfortunately, their use is limited by a cumulative dose-dependent cardiotoxicity. Despite more than five decades of research, the biological mechanisms underlying anthracycline cardiotoxicity are not completely understood. In this review, we discuss the incidence, risk factors, types, and pathophysiology of anthracycline cardiotoxicity, as well as methods to prevent and treat this condition. We also summarize and discuss advances made in the last decade in the comprehension of the molecular mechanisms underlying the pathology.

Lower-limb exoskeletons have undergone significant developments for aiding in the ambulation of adults with gait impairment. However, advancements in exoskeletons for the pediatric population have comparatively been lacking. This paper presents a newly developed joint actuator designed to drive the hip and knee joints of a pediatric lower-limb exoskeleton. The performance requirements associated with the actuators were determined based on a target audience of children ages 6&ndash, 11 years old. The developed actuators incorporate a hybrid belt-chain transmission driven by a frameless brushless DC motor. One actuator underwent benchtop testing to evaluate its performance with respect to their torque production, bandwidth properties, backdrivability in terms of inertia and friction characteristics, speed capabilities, and operational noise levels. As a preliminary validation, a set of actuators were placed in a prototype orthosis to move a pediatric test dummy in gait tracking via state-feedback control. The results showed that the newly developed actuators meet the design specifications and are suitable for use in the pediatric exoskeleton being developed.

Chronic loss of Augmenter of Liver Regeneration (ALR) results in mitochondrial myopathy with cataracts, however, the mechanism for this disorder remains unclear. Here, we demonstrate that loss of ALR, a principal component of the MIA40/ALR protein import pathway, results in impaired cytosolic Fe/S cluster biogenesis in mammalian cells. Mechanistically, MIA40/ALR facilitates the mitochondrial import of ATP binding cassette (ABC)-B8, an inner mitochondrial membrane protein required for cytoplasmic Fe/S cluster maturation, through physical interaction with ABCB8. Downregulation of ALR impairs mitochondrial ABCB8 import, reduces cytoplasmic Fe/S cluster maturation, and increases cellular iron through the iron regulatory protein-iron response element system. Our finding provides a mechanistic link between MIA40/ALR import machinery and cytosolic Fe/S cluster maturation through the mitochondrial import of ABCB8, and offers a potential explanation for the pathology seen in patients with ALR mutations.

This paper presents an innovative design methodology for development of lower limb exoskeletons with the fabrication and experimental evaluation of prototype hardware. The proposed design approach is specifically conceived to be suitable for the pediatric population and uses additive manufacturing and a model parameterized in terms of subject anthropometrics to give a person-specific custom fit. The methodology is applied to create computer-aided design models using average anthropometrics of children 6–11 years old and using anthropometrics of an individual measured by the researchers. This demonstrates that the approach can scale to subject weight and height. A prototype exoskeleton is fabricated, which can actuate the hip and knee joints without restricting hip abduction-adduction motion. In order to test usability of the device and evaluate walking assistance, user effort is quantified in an assisted condition where the subject walks on a level treadmill with the exoskeleton powered. This is compared to an unassisted condition with the exoskeleton unpowered and a baseline condition with the subject not wearing the exoskeleton. Comparing assisted to baseline conditions, torque magnitudes increased at the hip and knee, mechanical energy generated increased at the hip but decreased at the knee, and muscle activations increased in the Vastus Lateralis but decreased in the Biceps Femoris. While the preliminary evidence for walking assistance is not entirely convincing for the tested conditions, the presented design methodology itself is promising as it has been successfully validated through the creation of computer-aided design models for children and fabrication of a serviceable exoskeleton prototype.

Coronavirus Disease 2019 (COVID‐19) has infected more than 3.0 million people worldwide and killed more than 200,000 as of April 27, 2020. In this White Paper, we address the cardiovascular co‐morbidities of COVID‐19 infection; the diagnosis and treatment of standard cardiovascular conditions during the pandemic; and the diagnosis and treatment of the cardiovascular consequences of COVID‐19 infection. In addition, we will also address various issues related to the safety of healthcare workers and the ethical issues related to patient care in this pandemic.

Linear robust control techniques such as μ-synthesis can be used to design controllers for linear systems to guarantee specified performance criteria in the presence of modeling uncertainties, disturbances, and sensor noise. However, these techniques are rather uncommon in robotics due to the nonlinear nature of the plant where direct application would require large model uncertainties and therefore may only create a satisfactory controller if using lenient performance criteria. The inclusion of feedback linearization can rectify this by effectively converting the plant from a nonlinear system to a linear one, resulting in smaller model uncertainties. This paper proposes the use of feedback linearization to enable the use of linear robust control techniques on nonlinear systems. This approach is applied to a provisional version of a powered pediatric lower-limb orthosis. Sine sweep experiments are conducted to determine frequency response data for the system with and without feedback linearization. Models are identified to match the recorded data using optimization for both cases. Uncertainties are manually applied such that they encapsulate the observed measurements. The amount of uncertainties in the two models are quantified and a comparison shows that the uncertainties in the feedback-linearized system are smaller than in the system without feedback linearization.

For active magnetic bearing (AMB) systems with rotors having significant polar to transverse moments of inertia ratio, the influence of gyroscopic effects needs to be considered in controller design procedures to prevent excessive vibrations and potential instability during operation. This consideration leads to conservative controllers due to large uncertainties caused by the rotational speed range of the rotor, or gain-scheduled controllers that require larger computational power, both of which are not desirable. A cross-feedback control has been applied in the literature to compensate for the gyroscopic effects of AMB systems with rigid rotors. However, the method is not applicable to AMB systems with flexible rotors due to lack of full-state sensory information and under actuation. This paper proposes a novel modal state feedback control as an addon controller for AMB systems with flexible rotors to compensate for the gyroscopic effects of selected modes. The aim of the add-on controller is to alter the open loop AMB system such that the open loop dynamics presents reduced gyroscopic effects of the selected modes from a controller point of view, reducing the uncertainties in the model for robust controller design. The proposed approach is demonstrated on an AMB rotor test rig with a rotor configuration featuring noticeable gyroscopic effects. The comparison of the frequency response data of the open loop AMB system with and without the proposed add-on controller shows the feasibility of the approach.

SIRT2 is a cytoplasmic sirtuin that plays a role in various cellular processes, including tumorigenesis, metabolism, and inflammation. Since these processes require iron, we hypothesized that SIRT2 directly regulates cellular iron homeostasis. Here, we have demonstrated that SIRT2 depletion results in a decrease in cellular iron levels both in vitro and in vivo. Mechanistically, we determined that SIRT2 maintains cellular iron levels by binding to and deacetylating nuclear factor erythroid-derived 2-related factor 2 (NRF2) on lysines 506 and 508, leading to a reduction in total and nuclear NRF2 levels. The reduction in nuclear NRF2 leads to reduced ferroportin 1 (FPN1) expression, which in turn results in decreased cellular iron export. Finally, we observed that Sirt2 deletion reduced cell viability in response to iron deficiency. Moreover, livers from Sirt2-/- mice had decreased iron levels, while this effect was reversed in Sirt2-/- Nrf2-/- double-KO mice. Taken together, our results uncover a link between sirtuin proteins and direct control over cellular iron homeostasis via regulation of NRF2 deacetylation and stability.

Excess cellular iron increases reactive oxygen species (ROS) production and causes cellular damage. Mitochondria are the major site of iron metabolism and ROS production; however, few studies have investigated the role of mitochondrial iron in the development of cardiac disorders, such as ischemic heart disease or cardiomyopathy (CM). We observe increased mitochondrial iron in mice after ischemia/reperfusion (I/R) and in human hearts with ischemic CM, and hypothesize that decreasing mitochondrial iron protects against I/R damage and the development of CM. Reducing mitochondrial iron genetically through cardiac‐specific overexpression of a mitochondrial iron export protein or pharmacologically using a mitochondria‐permeable iron chelator protects mice against I/R injury. Furthermore, decreasing mitochondrial iron protects the murine hearts in a model of spontaneous CM with mitochondrial iron accumulation. Reduced mitochondrial ROS that is independent of alterations in the electron transport chain's ROS producing capacity contributes to the protective effects. Overall, our findings suggest that mitochondrial iron contributes to cardiac ischemic damage, and may be a novel therapeutic target against ischemic heart disease.

This paper proposes a novel method for implementing robust controllers for active magnetic bearing (AMB) systems in a computationally cost-effective manner without affecting robust performance. The method decomposes the single-rate LTI controller into two parts, one containing slow modes and the other fast modes, where the slow and fast modes refer to the low and high-frequency modes, respectively, relative to a threshold frequency. Slow modes of the controller do not need to be implemented at a fast rate to achieve an accurate response and, therefore, can be implemented at a slow rate. This transforms the single-rate LTI controller into a dual-rate periodically time-varying controller and can significantly reduce the computational cost of necessary algebra at each time step using the interlacing technique. The novel part of the method is the selection of the dual-rate configuration, i.e., selection of the threshold frequency for the decomposition and the implementation rate of the slow modes. The proposed method utilizes the largest singular values of the closed-loop system along with μ-analysis and lifting technique to analyze robust performance of different dual-rate implementations and determines the optimal dual-rate configuration that maintains robust performance while maximizing computational savings. The presented method is demonstrated experimentally on an AMB test stand. A dual-rate configuration is identified that reduces the computational cost of the necessary controller algebra by 35% while maintaining robust performance. Experimental comparison of the performance and computational cost of the single-rate and the dual-rate implementations of the controller are shown. The results demonstrate the feasibility and potential of the presented method.

Vasospastic angina due to coronary vasospasm can lead to cardiac arrest. A 60-year-old man, active smoker, presented to the emergency department after being found unresponsive. An initial electrocardiogram showed a wide QRS, lateral ST-elevations, and massive reciprocal ST-depressions, which

This paper discusses designing of weights for both mixed-sensitivity and signal-based H∞ controller synthesis for active magnetic bearing (AMB) systems using genetic algorithm (GA) optimization. In mixed-sensitivity problem formulation, the weights represent desired upper bounds to closed loop transfer functions and in signal-based problem formulation, the weights represent desired system response under sinusoidal exogenous inputs. In order to cast weight design process as an optimization problem, appropriate cost functions are chosen to guarantee that desired performance objectives are satisfied with a stable controller. First, the validity of the method is demonstrated in simulation by comparing performances achieved using weights designed through the optimization to the weights selected as performance objectives. Then, the weight design via GA for H∞ controller synthesis is tested experimentally on a small AMB test rig in a disturbance rejection scheme. The designed H∞ controllers are implemented on the AMB system and tested up to the maximum design speed of 6000 rpm, where the rotor safely passed the first critical speed. Achieved performances are compared to a benchmark PID controller. Results demonstrate validity of using GA for weights design and show the superiority of H∞ controllers over PID controller for disturbance rejection in AMB systems.