Active Compensation Research Articles

Monitoring Hip Joint Muscle Function in Osteoarthritis Patients Following Arthroplasty: A Prospective Cohort Study

Background/Objectives: Osteoarthritis (OA) is a chronic and progressive joint disease, leading to functional limitations and significantly impairing the quality of life. Muscle weakness, reduced mobility, and compensatory biomechanical changes are common consequences, further exacerbating functional decline. The aim of this study was to assess the impact of hip osteoarthritis on muscle functionality and to evaluate the effectiveness of hip arthroplasty using the MyotonPro device to measure key biomechanical parameters, i.e., tension, stiffness, and flexibility. Methods: This cohort study included 40 patients (17 women and 23 men; mean age 64.55 ± 10.49 years) with advanced hip OA (Kellgren–Lawrence grade III–IV) undergoing hip arthroplasty. Measurements of muscle tension (F), stiffness (S), and flexibility (D) in the gluteus maximus, rectus femoris, and biceps femoris were performed at three time points: before surgery, on postoperative days 8–10, and one month after hospital discharge. Pain (VAS), balance (Tinetti scale), and functional ability (WOMAC index) were also assessed. Results: Hip arthroplasty significantly reduced pain levels (VAS: 6.38 ± 0.28 preoperatively to 1.88 ± 0.22 postoperatively, p < 0.001) and improved functional ability (WOMAC: p < 0.001). Muscle tension and stiffness of the gluteus maximus initially increased after surgery (tension: 11.57 ± 0.32 to 12.15 ± 0.38, p = 0.009), reflecting compensatory stabilization but decreased by the final evaluation. Flexibility improved significantly over time (p = 0.014). The biceps femoris muscle exhibited a significant reduction in tension one month postoperatively (p = 0.015), alongside decreased stiffness (p = 0.015) and enhanced flexibility. The rectus femoris muscle showed minor changes in biomechanical properties, with no statistically significant differences detected. Conclusions: Osteoarthritis significantly impacts muscle function, reducing the gluteus muscle tension and stiffness, which compromises joint stability and triggers compensatory activity in the rectus femoris and biceps femoris muscles. Postoperative rehabilitation is essential for improving flexibility and addressing compensatory muscle tension.

Active axial motion compensation in multiphoton-excited fluorescence microscopy.

In living organisms, the natural motion caused by heartbeat, breathing, or muscle movements leads to the deformation of tissue caused by translation and stretching of the tissue structure. This effect results in the displacement or deformation of the plane of observation for intravital microscopy and causes motion-induced aberrations of the resulting image data. This, in turn, places severe limitations on the time during which specific events can be observed in intravital imaging experiments. These limitations can be overcome if the tissue motion can be compensated such that the plane of observation remains steady. We have developed a mathematical shape space model that can predict the periodic motion of a cylindrical tissue phantom resembling blood vessels. This model is then used to rapidly calculate the future position of the plane of observation of a two-photon laser scanning fluorescence microscope. The focal plane is continuously adjusted to the calculated position with a piezo-actuated objective lens holder. We demonstrate active motion compensation for non-harmonic axial displacements of the vessel phantom with a field of view up to 400 µm × 400 µm, vertical amplitudes of more than 100 µm, and at a rate of 0.5 Hz.

Background factors for postoperative eyebrow descent in blepharoptosis: A retrospective case-control study of 93 patients.

Upper blepharoplasty for ptosis aims to achieve functional and aesthetic outcomes. However, postoperative eyebrow descent is a potential complication that can affect surgical outcomes. This descent reflects the return of the brow to its normal position due to the release of compensatory frontalis muscle activity for ptosis. Identifying patients with this outcome may improve aesthetic results. This retrospective case-control study analyzed 93 patients who underwent upper blepharoplasty to identify factors associated with postoperative eyebrow descent and measure eyebrow positions before and 1.5 months after surgery. Data included patient age, sex, pre- and postoperative margin reflex distance-1, skin excision height, and levator aponeurosis advancement distance. The results showed that postoperative eyebrow descent (≥5%) occurred in 61% of the patients. Significant associations were found between postoperative eyebrow descent and sex (p = 0.028), preoperative eyebrow descent at eyelid closure (p < 0.001), and skin excision height (p = 0.012). Male patients had a significantly higher incidence of postoperative eyebrow descent, most likely due to larger skin excisions. For patients with preoperative eyebrow descent at eyelid closure and those requiring larger skin excisions, considering the possibility of postoperative eyebrow descent may improve aesthetic outcomes.

High-Speed and High-Resolution Polygon Mirror-Based Industrial Stereolithography With Advanced Active Error Compensation

High-Speed and High-Resolution Polygon Mirror-Based Industrial Stereolithography With Advanced Active Error Compensation

Design and Optimization of Bi-Planar Coils for Active Magnetic Compensation System Inside the MINI-Magnetically Shielded Room

Design and Optimization of Bi-Planar Coils for Active Magnetic Compensation System Inside the MINI-Magnetically Shielded Room

Active Compensation of Shear-Stress-Related Nonorthogonality in CMOS Vertical Hall-Based Angle Sensors

Active Compensation of Shear-Stress-Related Nonorthogonality in CMOS Vertical Hall-Based Angle Sensors

A new series‐parallel active compensator for DC microgrids based on three‐leg voltage source converter

AbstractDC microgrids are gaining increasing attention due to their advantages such as high reliability, high efficiency, ease of renewable energy sources integration, and the absence of frequency and reactive power regulation problems. Connection of AC energy sources and loads to the DC microgrids through AC/DC converters can distort the DC microgrids voltage and current. In addition, the fault occurrence in the DC or upstairs AC microgrids can cause voltage sag and swell. Compensating and reducing these voltage and current distortions requires efficient and cost‐effective solutions. This article proposes two new topologies of DC series‐parallel active compensators for voltage and current compensation in DC microgrids. In the first topology, the back‐to‐back connection of an isolated bidirectional DC/DC converter with a full‐bridge converter is used to compensate voltage and current. In the second one, to eliminate the transformer, simplify the converter structure and reduce its cost, an active compensator based on a three‐leg voltage source converter is proposed which can compensate both the microgrid voltage harmonics, sag and swell, and the load current harmonics. The proposed topologies performances are confirmed through their simulation in the MATLAB/SIMULINK environment. A simple experimental setup is also provided to validate the simulation results.

Enhanced prefrontal nicotinic signaling as evidence of active compensation in Alzheimer’s disease models

BackgroundCognitive reserve allows for resilience to neuropathology, potentially through active compensation. Here, we examine ex vivo electrophysiological evidence for active compensation in Alzheimer’s disease (AD) focusing on the cholinergic innervation of layer 6 in prefrontal cortex. Cholinergic pathways are vulnerable to neuropathology in AD and its preclinical models, and their modulation of deep layer prefrontal cortex is essential for attention and executive function.MethodsWe functionally interrogated cholinergic modulation of prefrontal layer 6 pyramidal neurons in two preclinical models: a compound transgenic AD mouse model that permits optogenetically-triggered release of endogenous acetylcholine and a transgenic AD rat model that closely recapitulates the human trajectory of AD. We then tested the impact of therapeutic interventions to further amplify the compensated responses and preserve the typical kinetic profile of cholinergic signaling.ResultsIn two AD models, we found potentially compensatory upregulation of functional cholinergic responses above non-transgenic controls after onset of pathology. To identify the locus of this enhanced cholinergic signal, we dissected key pre- and post-synaptic components with pharmacological strategies. We identified a significant and selective increase in post-synaptic nicotinic receptor signalling on prefrontal cortical neurons. To probe the additional impact of therapeutic intervention on the adapted circuit, we tested cholinergic and nicotinic-selective pro-cognitive treatments. Inhibition of acetylcholinesterase further enhanced endogenous cholinergic responses but greatly distorted their kinetics. Positive allosteric modulation of nicotinic receptors, by contrast, enhanced endogenous cholinergic responses and retained their rapid kinetics.ConclusionsWe demonstrate that functional nicotinic upregulation occurs within the prefrontal cortex in two AD models. Promisingly, this nicotinic signal can be further enhanced while preserving its rapid kinetic signature. Taken together, our work suggests that compensatory mechanisms are active within the prefrontal cortex that can be harnessed by nicotinic receptor positive allosteric modulation, highlighting a new direction for cognitive treatment in AD neuropathology.

Mixed reality alters motor planning and control

Compared to physical unmediated reality (UR), mixed reality technologies, such as Virtual (VR) and Augmented (AR) Reality, entail perturbations across multiple sensory modalities (visual, haptic, etc.) that could alter how actors move within the different environments. Because of the mediated nature, goal-directed movements in VR and AR may rely on planning and control processes that are different from movements in UR, resulting in less efficient motor control. The current study involved participants performing manual pointing movements on Müller-Lyer illusion stimuli to examine the relative contributions of movement planning and online control in UR, VR, and AR. Compared to UR, movements in VR were slower but were equally variable with a comparable level of online control, whereas movements in AR showed comparable speed but exhibited higher variability and less online control. Further, movements in VR and AR demonstrated a greater illusory effect in endpoint accuracy relative to UR. These findings suggested that participants in VR adopted an active compensation strategy to overcome the impact of less efficient online control, whereas participants in AR did not. The findings that movement planning and execution in VR and AR are fundamentally different from those in UR provide valuable insights into the potential neural systems engaged during movements in different realities.

The relationship between fractional amplitude of low-frequency fluctuations (fALFF) and the severity of neglect in patients with unilateral spatial neglect (USN) after stroke: A functional near-infrared spectroscopy study.

Unilateral spatial neglect (USN) following right hemisphere stroke is more pronounced, severe, and persistent than in the left hemisphere. However, the pathophysiological mechanisms underlying USN remain largely unknown. This study aims to investigate the relationship between the fractional amplitude of low-frequency fluctuations (fALFF) in the right hemisphere of patients with post-stroke USN and the severity of neglect using resting-state functional near-infrared spectroscopy (fNIRS) technology. This could provide new theoretical insights into the subtle changes in the pathophysiology of spontaneous neural activity in brain regions of patients with USN. Seventeen patients with post-stroke USN (USN group) and twenty-four control subjects (control group) were selected. A 22-channel fNIRS system was used to test the hemodynamic signals of the right hemisphere at rest for all subjects. Data preprocessing and analysis were performed using the NIRS-KIT toolbox. Patients in the USN group were assessed using the Behavioral Inattention Test-Conventional (BIT-C) and the Catherine Bergego Scale (CBS). Differences in fALFF values across channels between the two groups were compared, and the fALFF values from channels showing significant differences in the USN group were correlated with scores on scales evaluating the severity of USN. (1) Significant differences in fALFF values were observed between the USN and control groups in specific channels, with channels CH6 and CH11 showing significantly lower fALFF values in the USN group compared to the control group (p < 0.05), while channels CH12, CH16, and CH21 exhibited significantly higher fALFF values in the USN group (p < 0.05). (2) In patients with USN, fALFF values in CH12 were significantly negatively correlated with BIT-C scores (r = -0.4966, p = 0.0443), and fALFF values in CH21 were also significantly negatively correlated with BIT-C scores (r = -0.5270, p = 0.0318). (3) Only the fALFF values in CH21 were significantly positively correlated with CBS scores in patients with USN (r = 0.5512, p = 0.0236). The severity of symptoms of neglect towards the left side in patients with USN may be related to compensatory neural functional activity in the right dorsolateral prefrontal cortex area.

Towards Less Invasive Instruments For Cardiac Tissue Stabilizing

Abstract Beating-heart surgery is performed to reduce patient trauma but depending on the intervention requires tissue stabilization through vacuum cardiac tissue stabilizers. Current designs either require open chest sternotomy or display significant residual motion when used minimally invasively. Active motion compensation methods require complex control algorithms and expensive technology. We propose a novel design for a vacuum tissue stabilizer with expandable suction feet enabling a larger stabilized area and increased motion reduction. Its performance is evaluated on a heart phantom using a silicon membrane mimicking cardiac tissue properties. The motion of the membrane is captured using a stereo camera and marker points on the membrane surface. The results are then compared to a state-of-the-art tissue stabilizer. The extended stabilizer is found to stabilize a 110% larger area while achieving similar motion amplitude reduction. Thus, extendable stabilizers seem to be a promising solution for improved cardiac tissue stabilization in less invasive beating-heart surgery.

A hybrid active control method for a 3-DOF wave-compensated gangway

ABSTRACT Wave-compensated gangways are affected by forces from internal joint coupling and vessel motion, making the control process complex and challenging. Previously, three-degree-of-freedom gangways adopted passive compensation methods, utilizing end-effector sensor feedback for control. However, these methods are constrained by slow response times and significant lag. This study proposes an active hybrid compensation approach to enhance response speed and reduce tracking errors. The kinematics and dynamics of the gangway under vessel motion were analyzed. Subsequently, an improved velocity feedforward second-order super-twisting sliding mode control scheme was designed, complemented by fuzzy control for small torque compensation. Two experiments were conducted to evaluate and compare the performance of three control methods. Experiments demonstrated that the proposed hybrid control method exhibited superior performance in joint trajectory tracking, significantly reducing both root mean square and maximum errors, validating its effectiveness in improving tracking speed and accuracy.

UBR1 Promotes Sex-Dependent ACE2 Ubiquitination in Hypertension.

Ang-II (angiotensin II) impairs the function of the antihypertensive enzyme ACE2 (angiotensin-converting enzyme 2) by promoting its internalization, ubiquitination, and degradation, thus contributing to hypertension. However, few ACE2 ubiquitination partners have been identified, and their role in hypertension remains unknown. Proteomics and bioinformatic analyses were used to identify ACE2 ubiquitination partners in the brain, heart, and kidney of hypertensive C57BL6/J mice of both sexes. The interaction between UBR1 (ubiquitin protein ligase E3 component N-recognin) and ACE2 was validated in cells. Central and peripheral UBR1 knockdown was then performed in male mice to investigate its role in the maintenance of hypertension. Proteomics analysis of the hypothalamus identified UBR1 as a potential E3 (ubiquitin protein ligase) ligase promoting ACE2 ubiquitination. Enhanced UBR1 expression, associated with ACE2 reduction, was confirmed in various tissues from hypertensive male mice and human samples. Treatment of endothelial and smooth muscle cells with testosterone, but not 17β-estradiol, confirmed a sex-specific regulation of UBR1. In vivo silencing of UBR1 using chronic administration of small interference RNA resulted in the restoration of ACE2 levels in hypertensive male mice. A transient decrease in blood pressure after intracerebroventricular, but not systemic, infusion was also observed. Interestingly, UBR1 knockdown increased brain activation of Nedd4-2 (neural precursor cell expressed developmentally downregulated protein 4), an E3 ligase promoting ACE2 ubiquitination, and reduced expression of serum and glucocorticoid-regulated kinase 1, the kinase that inactivates Nedd4-2. These data demonstrate that UBR1 is a novel E3 ubiquitin ligase targeting ACE2 in hypertension. UBR1 and Nedd4-2 appear to work synergistically to ubiquitinate ACE2. Targeting these ubiquitin ligases may represent a novel strategy to restore ACE2 compensatory activity in hypertension.

Deciphering the Impact of the Active Lithium Reservoir in Anode-Free Pouch Cells

Anode-free batteries, which revolutionize energy storage by discarding traditional anodes in favor of copper foil to plate lithium directly from the cathode, offer increased energy densities and better safety than conventional lithium-metal cells. However, their advantage is tempered by a significantly reduced cycle life, attributed to lithium loss through parasitic reactions. As a result, inactive (‘dead’) lithium accumulates over cycling, including (electro)chemically formed Li+ compounds in the solid electrolyte interphase (SEI) and isolated unreacted metallic Li0, resulting in capacity loss and safety hazards. Consequently, to continue enhancing the performance of anode-free cells, it appears crucial to differentiate and quantify the various forms of lithium in these cells and monitor their distribution and evolution throughout the cycling process, depending on various conditions such as pressure or electrolytes.Compared to lithium metal cells, the problem might appear simplified for anode-free cells as there is no active lithium compensation from the anode, and all the active lithium is initially stored within the cathode. However, the intricate interplay of the cathode's first-cycle irreversibility and lithium plating/stripping efficiency significantly influences the shape of the capacity retention curves and the measurements of coulombic efficiency (CE). Herein we aim to clarify the contribution of the lithium reservoir to the anode-free cell performances. We report a systematic study of the active lithium reservoir and unreacted metallic Li0 evolution in anode-free LiNi0.6Mn0.2Co0.2O2 (NMC622)||Copper (Cu) commercial pouch cells. By taking advantage of a discharge characteristic of the NMC622 cathode at low voltage (<1.5 V), we could quantify the presence of remaining active lithium at the anode. Afterwards, titration gas chromatography was utilized to measure the remaining inactive Li0 on the discharged samples. By coupling the quantification techniques to observations of the anode local microstructure by cryogenic scanning electron microscopy, we elucidate the formation and evolution mechanism of the lithium reservoir and inactive metallic lithium in different types of electrolytes.As a result, we demonstrated that the once-considered drawback of Ni-rich layered oxide cathodes, namely the first cycled intrinsic irreversible capacity, can be manipulated to build a lithium reservoir at the anode and extend the cycle life of anode-free cells (see Figure 1, bottom left). Additionally, the formerly unclear reason for the capacity degradation discrepancy of anode-free cells under different C-rates was investigated and attributed to the correlation between lithium utilization and reservoirs (see Figure 1, bottom right). In contrast to the first-cycle irreversibility unique to certain types of cathode materials, this approach can be applied to all types of cells having polarization phenomena at high currents to enhance their longevity in anode-free configurations. Consequently, by employing protocols with slow charge and fast discharge, the lithium reservoir at the anode is maximized, and the performances of the anode-free cells appear stable for a longer number of cycles. With this knowledge, one can regulate the ratio between lithium utilization and lithium reservoirs for extended capacity retention or high initial reversible capacity designated for different applications. We believe the concept of this Li reservoir can be further extended to other approaches and opens new opportunities, taking advantage of cathode intrinsic irreversibility and kinetic limitations to extend anode-free cells’ lifespan. Figure 1

Enhancement of Magnetic Shielding Based on Low-Noise Materials, Magnetization Control, and Active Compensation: A Review.

Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic field, gradient, and low-frequency noise. However, the conventional method to improve the shielding performance by adding layers of materials is restricted by complex construction and inherent materials noise. This paper provides a comprehensive review about the enhancement of magnetic shielding in three aspects, including low-noise materials, magnetization control, and active compensation. The generation theorem and theoretical calculation of materials magnetic noise is summarized first, focusing on the development of spinel ferrites, amorphous, and nanocrystalline. Next, the principles and applications of two magnetization control methods, degaussing and magnetic shaking, are introduced. In the review of the active magnetic compensation system, the forward and inverse design methods of coil and the calculation method of the coupling effect under the ferromagnetic boundary of magnetic shield are explained in detail, and their applications, especially in magnetocardiography (MCG) and magnetoencephalogram (MEG), are also mainly described. In conclusion, the unresolved challenges of different enhancement methods in materials preparation, optimization of practical implementation, and future applications are proposed, which provide comprehensive and instructive references for corresponding research.

Deep water characteristics of electrodynamic transducers based on distributed-parameter equivalent circuit of acoustic cavity

The source level of the electrodynamic transducer with a passive pressure compensation airbag in ultra-low frequencies (bands below 100 Hz) decreases sharply with the increase in working depth. A theoretical model with a distributed-parameter equivalent circuit of the acoustic cavity was proposed to explore the mechanism of this phenomenon and find a way to improve the ultra-low frequency source level in deep water (over 200 m). The results indicate that the decrease in acoustic compliance of the cavity in deep water leads to an increase in resonant frequency, resulting in a decrease in source level in the ultra-low frequency band. The resonance frequency in deep water shows differences based on distributed and lumped parameter models. The resonance frequency test results of the prototype show that the theoretical results based on a distributed-parameter model proposed in this study are more consistent with the test values. The effects of the acoustic cavity's structural size, the acoustic parameters of the gas in the cavity, and the active pressure compensation method on the source level at different depths were analyzed. Results reveal that the acoustic performance in ultra-low frequency bands at large depths can be markedly improved using the active pressure compensation method.

Performance analysis of satellite-to-ground 16QAM coherent optical communication

Abstract Atmospheric turbulence and pointing errors are two major factors affecting satellite-to-ground coherent optical communication links. This study considers the effects of power scintillation and phase jitter caused by atmospheric turbulence, as well as active mode compensation for wavefront phase distortion. Additionally, residual pointing errors due to platform micro-vibrations are taken into account, and a statistical channel model is derived under the combined effects of atmospheric turbulence and residual pointing errors during tracking and acquisition. Based on this model, a closed-form approximate expression for the average bit error rate (BER) of 16QAM satellite-to-ground coherent optical communication is derived using the Meijer-G function. The results show that the derived BER expression matches well with numerical integration results, confirming its accuracy and applicability under various link conditions. Through numerical simulations, the effects of residual pointing error variance, turbulence strength, satellite zenith angle, and transceiver antenna aperture on the performance of 16QAM satellite-to-ground coherent optical communication are evaluated. The findings offer valuable theoretical insights for the design and optimization of future satellite-to-ground 16QAM coherent optical communication systems.

Development of 6DOF Hardware-in-the-Loop Ground Testbed for Autonomous Robotic Space Debris Removal

This paper presents the development of a hardware-in-the-loop ground testbed featuring active gravity compensation via software-in-the-loop integration, specially designed to support research in autonomous robotic removal of space debris. The testbed is designed to replicate six degrees of freedom (6DOF) motion maneuvering to accurately simulate the dynamic behaviors of free-floating robotic manipulators and free-tumbling space debris under microgravity conditions. The testbed incorporates two industrial 6DOF robotic manipulators, a three-finger robotic gripper, and a suite of sensors, including cameras, force/torque sensors, and tactile tensors. Such a setup provides a robust platform for testing and validating technologies related to autonomous tracking, capture, and post-capture stabilization within the context of active space debris removal missions. Preliminary experimental results have demonstrated advancements in motion control, computer vision, and sensor fusion. This facility is positioned to become an essential resource for the development and validation of robotic manipulators in space, offering substantial improvements to the effectiveness and reliability of autonomous capture operations in space missions.

Compensatory activity of the PC-ME1 metabolic axis underlies differential sensitivity to mitochondrial complex I inhibition.

Deficiencies in the electron transport chain (ETC) lead to mitochondrial diseases. While mutations are distributed across the organism, cell and tissue sensitivity to ETC disruption varies, and the molecular mechanisms underlying this variability remain poorly understood. Here we show that, upon ETC inhibition, a non-canonical tricarboxylic acid (TCA) cycle upregulates to maintain malate levels and concomitant production of NADPH. Our findings indicate that the adverse effects observed upon CI inhibition primarily stem from reduced NADPH levels, rather than ATP depletion. Furthermore, we find that Pyruvate carboxylase (PC) and ME1, the key mediators orchestrating this metabolic reprogramming, are selectively expressed in astrocytes compared to neurons and underlie their differential sensitivity to ETC inhibition. Augmenting ME1 levels in the brain alleviates neuroinflammation and corrects motor function and coordination in a preclinical mouse model of CI deficiency. These studies may explain why different brain cells vary in their sensitivity to ETC inhibition, which could impact mitochondrial disease management.

Design of a Flexure-Based XYZ Micropositioner With Active Compensation of Vertical Crosstalk

Design of a Flexure-Based XYZ Micropositioner With Active Compensation of Vertical Crosstalk