Feedback Signal Research Articles

A biochemical feedback signal for hypothermia treatment for neonatal hypoxic-ischemic encephalopathy: focusing on central nervous system proteins in biofluids.

Hypothermia has been widely used to treat moderate to severe neonatal hypoxic-ischemic encephalopathy (HIE), yet evaluating the effects of hypothermia relies on clinical neurology, neuroimaging, amplitude-integrated electroencephalography, and follow-up data on patient outcomes. Biomarkers of brain injury have been considered for estimating the effects of hypothermia. Proteins specific to the central nervous system (CNS) are components of nervous tissue, and once the CNS is damaged, these proteins are released into biofluids (cerebrospinal fluid, blood, urine, tears, saliva), and they can be used as markers of brain damage. Clinical reports have shown that CNS-specific marker proteins (CNSPs) were early expressed in biofluids after brain damage and formed unique biochemical profiles. As a result, these markers may serve as an indicator for screening brain injury in infants, monitoring disease progression, identifying damage region of brain, and assessing the efficacy of neuroprotective measures. In clinical work, we have found that there are few reports on using CNSPs as biological signals in hypothermia for neonatal HIE. The aim of this article is to review the classification, origin, biochemical composition, and physiological function of CNSPs with changes in their expression levels after hypothermia for neonatal HIE. Hopefully, this review will improve the awareness of CNSPs among pediatricians, and encourage future studies exploring the mechanisms behind the effects of hypothermia on these CNSPs, in order to reduce the adverse outcome of neonatal HIE.

Asymmetric Doherty power amplifier design considering the effects of peaking power amplifier early conduction

During the design of a Doherty power amplifier (DPA), the phenomenon of peaking PA turning on in advance is commonly observed. This is mainly due to the feedback of the main PA signal to the gate of the peaking PA through the gate-drain feedback capacitor, which results in an increase in its gate voltage. As a result, the overall efficiency of the back-off region is significantly reduced. This paper first describes the phenomenon of peaking PA turning on in advance. The formula for the voltage (referred to as the feedback gate voltage, FGV) imposed on the gate of the peaking PA by the main PA signal is then deduced. On this basis, the FGV is analysed numerically. For verification, an asymmetric DPA with a 9 dB output back-off (OBO) power level is designed and fabricated in this paper using GaN CGH40010F and CGH40025F transistors. According to the measurement results, the saturated drain efficiency of the DPA is 53.5%–63.3% in the 0.75–1.25 GHz band, the efficiency at the 9 dB OBO level is between 45.5%–54%, and the saturated output power is between 45 dBm–45.7 dBm, with a saturation gain of more than 8 dB.

Effects of passive ankle exoskeletons on neuromuscular function during exaggerated standing sway

Wearable robotic exoskeletons designed to assist human movement should integrate with the neuromusculoskeletal system. This means assisting movement while not perturbing motor control. We sought to test if passive ankle exoskeletons, which have been shown to successfully assist human gait, affect neuromuscular control of an exaggerated anterior–posterior standing sway task. Participants actively swayed while wearing an ankle exoskeleton that provided 0, 42 or 85 Nm rad −1 of additional stiffness to the ankle joint in resistance to dorsiflexion. Sway amplitude was controlled via biofeedback to elicit similar ankle angle displacements across conditions. With greater exoskeleton stiffness, participants swayed at lower sway-cycle frequencies and slower centre of pressure speeds. Furthermore, increasing exoskeleton stiffness resulted in longer operating lengths of the medial gastrocnemius and overall reduced plantar flexor muscle activation. For the soleus, there was also a temporal shift in the cross-correlation of its electromyogram with the centre of pressure displacement, meaning that muscle activation peaked later than anterior sway displacement. Together, these data suggest that assistive ankle exoskeletons influence neuromuscular control of ankle-based sway tasks. Changes in fascicle lengths could influence afferent feedback signals and the short-range stiffness of ankle muscles, while shifts in muscle activation timing suggest changes in neural control. The observed neuromuscular adaptations to exoskeleton assistance demonstrate the potential implications for standing balance and overall movement control, prompting future investigations.

Decision Feedback Signal Combining for Cell-Free Massive MIMO With Distributed Implementation

Decision Feedback Signal Combining for Cell-Free Massive MIMO With Distributed Implementation

Pip5k1γ regulates axon formation by limiting Rap1 activity.

During their differentiation, neurons establish a highly polarized morphology by forming axons and dendrites. Cortical and hippocampal neurons initially extend several short neurites that all have the potential to become an axon. One of these neurites is then selected as the axon by a combination of positive and negative feedback signals that promote axon formation and prevent the remaining neurites from developing into axons. Here, we show that Pip5k1γ is required for the formation of a single axon as a negative feedback signal that regulates C3G and Rap1 through the generation of phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Impairing the function of Pip5k1γ results in a hyper-activation of the Fyn/C3G/Rap1 pathway, which induces the formation of supernumerary axons. Application of a hyper-osmotic shock to modulate membrane tension has a similar effect, increasing Rap1 activity and inducing the formation of supernumerary axons. In both cases, the induction of supernumerary axons can be reverted by expressing constitutively active Pip5k. Our results show that PI(4,5)P2-dependent membrane properties limit the activity of C3G and Rap1 to ensure the extension of a single axon.

Optimization stability and performance of the TPS storage ring dipole magnet power supply

This article focuses on the current status of the dipole magnet power supply (DMPS) and improvement in the Taiwan Photon Source (TPS) storage ring. The DMPS provides a stable and precise magnetic field for the storage ring operation. Appropriate wiring methods are employed to minimize magnetic field interference across the entire TPS area to meet the demands of high-energy output and overcome the challenges of operating at high currents. The target energy is set at 850 V and 750 A, utilizing a single-pole switching voltage regulator as a high-precision constant current source output structure. The system incorporates a closed control loop that uses the Direct Current Current Transducer (DCCT) to provide current signal feedback to the system. FPGA (Field-Programmable Gate Array) calculates PID (Proportional-Integral-Derivative) compensation values, generating a 2.1 kHz pulse width modulation (PWM) signal to regulate the output current. At the same time, insulated gate bipolar transistor (IGBT) modules are switching components. However, even after several years of practical operation, the stability and performance of the DMPS in the storage ring still require improvements. To enhance long-term output current stability and address peripheral issues, the current TPS utilizes the Beam Orbit Feedback (FOFB) system to suppress and fine-tune the magnetic field and compensate for the impact of temperature drift on the DMPS's output current. This improvement ensures a more stable circulation of the photon beam within the storage ring. By optimizing the temperature control circuit of the main control card, the long-term output current stability has been successfully enhanced to within ± 10 ppm. Simultaneously, the FOFB system reduces uncertainties in adjusting the X-axis beam position, improving beam stability and quality. Furthermore, relevant protective measures have been implemented to ensure robust system operation. Ultimately, these improvement measures have successfully met TPS's stringent requirements for the DMPS, enabling the synchrotron accelerator light source to operate at higher performance levels and fostering advanced scientific research. The results of these upgrades underscore the success of the power supply enhancements, making significant contributions to the overall improvement of the Taiwan Photon Source facility.

Piezoelectric dual network dressing with adaptive electrical stimulation for diabetic infected wound repair via antibacterial, antioxidant, anti-inflammation, and angiogenesis

Electrical stimulation therapy plays a crucial role in the healing of wounds. However, electrical stimulation based on piezoelectric materials faces limitations in dynamically matching cell activity and lacks anti-infection properties, thereby restricting its broader clinical application. Herein, a piezoelectric dual network nanofiber dressing (CuEG/PVDF) was prepared using copper/ epigallocatechin 3-gallate (Cu2+/EGCG) and polyvinylidene fluoride (PVDF). This dressing constructs dynamic force-electrical closed-loop feedback signals through cell adhesion and adaptive electrical stimulation to accelerate the healing of infectious diabetic wounds. Benefiting for the Cu2+-EGCG metal-polyphenol network, it enhances the electromechanical coupling properties, hydrophilicity, and cell adhesion of the piezoelectric double network dressing. Cell proliferation and migration were promoted by increased adhesion area, enhanced adaptive electrical stimulation, and active calcium influx. Moreover, CuEG/PVDF demonstrate significant antibacterial, antioxidant, anti-inflammatory, and angiogenic activities. In vivo experiments demonstrate that this dual-network piezoelectric dressing reduces the inflammatory response in rats, eliminates Methicillin-resistant Staphylococcus aureus (MRSA), and accelerates wound repair. Overall, this study presents a promising strategy for implementing electrical stimulation in the treatment of infected wounds.

Coordination of Controllers to Development of Wide-Area Control System for Damping Low-Frequency Oscillations Incorporating Large Renewable and Communication Delay

The modern power systems incorporate high penetration of renewable is a large, composite, interconnected network with dynamic behavior. The small disturbances occurring in the system may induce low-frequency oscillations (LFOs) in the system. If the (LFOs) are not suppressed within a stipulated time, it may cause system islanding or even blackouts. Hence, it is essential to investigate the behavior of the system under various levels of disturbances and control action must be taken to damp these oscillations. The established approach to damping the LFOs is by installing power system stabilizers (PSS). PSS uses the local signals from generators to control the oscillations. The dominant source of inter-area oscillations in power systems is due to overloaded weak interconnected lines, converter-interfaced generation, and the action of the high gain exciter present in the system. Consequently, wide area control is needed to control the inter-area oscillations existent in the system. This paper developed a coordinated design of conventional PSS, static compensator, renewable converters, and wide area controller for damping the local and inter-area oscillations in renewable incorporated power systems. The performance of the developed controller is evaluated through the time domain analysis and eigenvalue analysis. A comparison of the introduced controller has been done with other standard conventional methods. The choice of input signals for the wide area controller from the wide-area measurement system is done based on the controllability index. Additionally, the location of the controller must be identified to dampen the inter-area oscillations in the system. In this paper, the controllability index is calculated to find out the highly affected wide area signals for considering it as the feedback signal to a developed controller. The location of the controller is recognized by computing the participation factor. The developed controller has experimented on renewable incorporated large study power systems when time delay and noise are present in wide area signals.

Connected in Bad Times and in Good Times: Empathy Induces Stable Social Closeness.

Humans need social closeness to prosper. There is evidence that empathy can induce social closeness. However, it remains unclear how empathy-related social closeness is formed and how stable it is as time passes. We applied an acquisition-extinction paradigm combined with computational modeling and fMRI, to investigate the formation and stability of empathy-related social closeness. Female participants observed painful stimulation of another person with high probability (acquisition) and low probability (extinction) and rated their closeness to that person. The results of two independent studies showed increased social closeness in the acquisition block that resisted extinction in the extinction block. Providing insights into underlying mechanisms, reinforcement learning modeling revealed that the formation of social closeness is based on a learning signal (prediction error) generated from observing another's pain, whereas maintaining social closeness is based on a learning signal generated from observing another's pain relief. The results of a reciprocity control study indicate that this feedback recalibration is specific to learning of empathy-related social closeness. On the neural level, the recalibration of the feedback signal was associated with neural responses in anterior insula and adjacent inferior frontal gyrus and the bilateral superior temporal sulcus/temporoparietal junction. Together, these findings show that empathy-related social closeness generated in bad times, that is, empathy with the misfortune of another person, transfers to good times and thus may form one important basis for stable social relationships.

Quantifying local field potential dynamics with amplitude and frequency stability between ON and OFF medication and stimulation in Parkinson's disease

Neural oscillations are critical to understanding the synchronisation of neural activities and their relevance to neurological disorders. For instance, the amplitude of beta oscillations in the subthalamic nucleus has gained extensive attention, as it has been found to correlate with medication status and the therapeutic effects of continuous deep brain stimulation in people with Parkinson's disease. However, the frequency stability of subthalamic nucleus beta oscillations, which has been suggested to be associated with dopaminergic information in brain states, has not been well explored. Moreover, the administration of medicine can have inverse effects on changes in frequency and amplitude. In this study, we proposed a method based on the stationary wavelet transform to quantify the amplitude and frequency stability of subthalamic nucleus beta oscillations and evaluated the method using simulation and real data for Parkinson's disease patients. The results suggest that the amplitude and frequency stability quantification has enhanced sensitivity in distinguishing pathological conditions in Parkinson's disease patients. Our quantification shows the benefit of combining frequency stability information with amplitude and provides a new potential feedback signal for adaptive deep brain stimulation.

Tong-Xie-Yao-Fang strengthens intestinal feedback control of bile acid synthesis to ameliorate irritable bowel syndrome by enhancing bile salt hydrolase-expressing microbiota

Ethnopharmacological relevanceA herbal formula Tong-Xie-Yao-Fang (TXYF) is traditionally used to treat irritable bowel syndrome (IBS), modern pharmacological evidence supports that the formula efficacy is associated with altered gut microbiota. Yet, the mechanistic role of gut microbiota in the therapy of TXYF remains unclear. We previously clarified that gut microbiota-dysregulated bile acid (BA) metabolism contribute to the pathogenesis of IBS, deriving a hypothesis that microbiota-BA metabolic axis might be a potential target of TXYF. Aim of the studyWe aim to investigate a new gut microbiota-mediated mechanism underlying anti-IBS efficacy of TXYF. Materials and methodsWe established an IBS rat model with a combination of stressors, compared the herbal efficacy in models undergone gut bacterial manipulations, also examined BA metabolism-related microbiota, metabolites, genes and proteins by 16S rRNA gene sequencing, targeted metabolomics, qPCR and multiplex immunofluorescence staining. ResultsWe observed that TXYF attenuated visceral hyperalgesia and diarrhea in IBS rats but not in those underwent gut bacteria depletion. Transferring gut microbiota from TXYF-treated donors also decreased visceral sensitivity and slightly relief diarrhea-like behaviors in IBS recipient rats. Fecal 16S rRNA gene sequencing revealed that TXYF modulated microbial β-diversity and taxonomic structure of IBS rats, with a significant increase in relative abundance of bile salt hydrolase (BSH)-expressing Bacteroidaceae. qPCR and culturing data validated that TXYF had a promotive effect on the growth and BSH activity of Bacteroides species. TXYF-reshaped microbiota upregulated the expression of intestinal Fgf15, a feedback signal to control BA synthesis in the liver. As a result, the BA synthetic and excretory levels in IBS rats were decreased by TXYF, so as that colonic BA membrane receptor Tgr5 sensing and its mediated Calcitonin gene-related peptide (Cgrp)-positive neuronal response were attenuated. ConclusionThis study poses a new microbiota-driven therapeutic action for TXYF, highlighting the potential of developing new anti-IBS strategies from the herbal formula targeting BSH-expressing gut bacteria.

Immersive virtual reality for learning about ecosystems: effect of two signaling levels and feedback on action decisions.

The goal of the present study was to test the effect of signaling associated with feed-back in learning forest ecosystems in the context of realistic living forest simulator, in IVR conditions for students in agriculture. Two signaling modalities, corresponding to two signaling levels, were investigated: visual flashing of forest elements (tree species, plants, flowers, fungi, wet-areas etc.) and marker-stones, both with text in pop-up windows, in a 2x2 experimental plan. Ninety-three pupils of an agricultural technological high school had to explore (including physically), interrogate (search for) and select (using the joysticks) relevant elements of the forest in three living forest areas (visually delimited inside of a broader forest area) in order to choose (and justify) the best area, among the three, in which an equipped public-tourist reception site (picnic, resting, reception site) could be built. The chosen site must have the least possible negative impact on the ecosystem of the forest and its development over time. After their decision (and justification) they were provided a feed-back with a series of VR desktop multimedia slides showing the effect of this choice on the ecosystem of the chosen area. After the feed-back they had to decide and justify again whether they would change or maintain their first decision. Finally, subjective scales were also used in order to investigate presence, cognitive complexity, sickness and overall enjoyment. Results showed significant positive effects of both signaling levels, and of the feed-back on the correct decision answers. Further, the combination, and interaction, between signaling and feedback seemed to enhance, the activation and retrieval from memory, of the task-relevant concepts. In addition, the results indicated a significant positive effect (medium size) of presence on decision performances, a finding which is consistent with the immersion principle.

Steering Mirror System with Closed-Loop Feedback for Free-Space Optical Communication Terminals

Precision beam pointing plays a critical role in free-space optical communications terminals in uplink, downlink and inter-satellite link scenarios. Among the various methods of beam steering, the use of fast steering mirrors (FSM) is widely adopted, with many commercial solutions employing diverse technologies, particularly focusing on small, high-bandwidth mirrors. This paper introduces a method using lightweight, commercial off-the-shelf components to construct a custom closed-loop steering mirror platform, suitable for mirror apertures exceeding 100 mm. The approach involves integrating optical encoders into two off-the-shelf open-loop actuators. These encoders read the signal reflected on purposefully diamond-machined knurled screw knobs, providing maximum contrast between light and dark lines. The resulting steering mirror has the potential to complement or replace FSM in applications requiring a larger stroke, at the expense of motion speed. In the presented setup, the mirror tilt resolution achieved based on the encoder closed-loop signal feedback is 45 μrad, with a mean slew rate of 1.5 mrad/s. Importantly, the steering assembly is self-locking, requiring no power to maintain a steady pointing angle. Using the mirror to actively correct for a constantly moving incoming beam, a 5-fold increase in concentration of the beam spot on the center of the detector was obtained compared to a fixed position mirror, demonstrating the mirrors ability to correct for satellite platform jitter and drift.

A spatiotemporal atlas of cholestatic injury and repair in mice.

Cholestatic liver injuries, characterized by regional damage around the bile ductular region, lack curative therapies and cause considerable mortality. Here we generated a high-definition spatiotemporal atlas of gene expression during cholestatic injury and repair in mice by integrating spatial enhanced resolution omics sequencing and single-cell transcriptomics. Spatiotemporal analyses revealed a key role of cholangiocyte-driven signaling correlating with the periportal damage-repair response. Cholangiocytes express genes related to recruitment and differentiation of lipid-associated macrophages, which generate feedback signals enhancing ductular reaction. Moreover, cholangiocytes express high TGFβ in association with the conversion of liver progenitor-like cells into cholangiocytes during injury and the dampened proliferation of periportal hepatocytes during recovery. Notably, Atoh8 restricts hepatocyte proliferation during 3,5-diethoxycarbonyl-1,4-dihydro-collidin damage and is quickly downregulated after injury withdrawal, allowing hepatocytes to respond to growth signals. Our findings lay a keystone for in-depth studies of cellular dynamics and molecular mechanisms of cholestatic injuries, which may further develop into therapies for cholangiopathies.

A bit rate condition for feedback stabilization of uncertain switched systems with external disturbances based on event triggering

AbstractThis paper studies the input‐to‐state stability of an uncertain switched linear system with external disturbances, whose feedback loop is closed over a digital communication network. In the network, only a finite bit rate can be provided to transmit the feedback signal and unknown network delay always exists. By using reachable set approximation and propagation methods, it can well handle with the effects of model uncertainty, external disturbances and network delay on the stability of the system. To save network resources, event‐triggered sampling is taken here. Under the event‐triggered sampling strategies, a new encoder is proposed, which consumes less feedback bits than the conventional time‐triggered encoders. It is proven that even in the existence of model uncertainty, external disturbances and network delay, the proposed event‐triggered sampling strategies require a lower feedback bit rate to stabilize the switched system than conventional periodic sampling methods.

Improving the robustness of distributed secondary control in autonomous microgrids to mitigate the effects of communication delays

Distributed control has been employed in autonomous microgrids (MGs) to attain secondary control goals. However, the reliance of MG’s distributed secondary control on communication makes it vulnerable to degraded performance and the risk of instability due to communication delays. This paper enhances the flexibility of the MG control framework, with each distributed generator incorporating supplementary local feedback signals. This added flexibility strengthens the MG’s ability to counteract disturbances caused by delays and enhances its dynamic performance. The introduction of extra feedback signals has a direct impact on the dynamic response of the MG, leaving its steady-state condition unaffected. In comparison to the methods found in existing literature, the increased flexibility relaxes the inherent trade-off between the objectives of improved transient response and the system’s ability to mitigate disturbances caused by delays. To model the MG, a set of delay differential–algebraic equations (DDAEs) is used. The small-signal linearized model is derived and employed to evaluate the stability of the MG as well as fine-tune the control parameters. The effectiveness of this proposed control structure is demonstrated using the MATLAB/Simulink environment and a controller in the loop (CIL) setup, tested against both fixed universal and asynchronous delays, as well as time-varying delays.

Megahertz multi-parametric ophthalmic OCT system for whole eye imaging

An ultrahigh-speed, wide-field OCT system for the imaging of anterior, posterior, and ocular biometers is crucial for obtaining comprehensive ocular parameters and quantifying ocular pathology size. Here, we demonstrate a multi-parametric ophthalmic OCT system with a speed of up to 1 MHz for wide-field imaging of the retina and 50 kHz for anterior chamber and ocular biometric measurement. A spectrum correction algorithm is proposed to ensure the accurate pairing of adjacent A-lines and elevate the A-scan speed from 500 kHz to 1 MHz for retinal imaging. A registration method employing position feedback signals was introduced, reducing pixel offsets between forward and reverse galvanometer scanning by 2.3 times. Experimental validation on glass sheets and the human eye confirms feasibility and efficacy. Meanwhile, we propose a revised formula to determine the “true” fundus size using all-axial length parameters from different fields of view. The efficient algorithms and compact design enhance system compatibility with clinical requirements, showing promise for widespread commercialization.

Feedback signal detection and drive signal compensation for electromagnetic MEMS scanning mirror based on FPGA

Feedback signal detection and drive signal compensation for electromagnetic MEMS scanning mirror based on FPGA

IoT Smart Control System: Smoke and Fire Detection Using SIM900A Module

The main focus of this system is to detect smoke and fire effectively in potential hazard situations. This system utilizes sensor technology to monitor changes in environmental conditions, with the aim of providing quick responses and notifications to users or relevant authorities via a cellular connection. This approach combines feedback signals from sensors and cellular connectivity using the SIM900A module processed with a microcontroller to increase the efficiency and reliability of hazard detection. This system was designed with the aim of providing an efficient and affordable solution for detecting potential fires or other hazardous situations in various environments, including homes, offices and industrial areas. Trial results show that this system is capable of detecting smoke and fire with high accuracy, as well as providing instant notifications via text messages or digital notifications. This innovation is expected to make a positive contribution in improving safety and security in various sectors, while leveraging the potential of IoT connectivity to provide smarter solutions in hazard detection.

Modulation of subthalamic beta oscillations by movement, dopamine, and deep brain stimulation in Parkinson’s disease

Subthalamic beta band activity (13–35 Hz) is known as a real-time correlate of motor symptom severity in Parkinson’s disease (PD) and is currently explored as a feedback signal for closed-loop deep brain stimulation (DBS). Here, we investigate the interaction of movement, dopaminergic medication, and deep brain stimulation on subthalamic beta activity in PD patients implanted with sensing-enabled, implantable pulse generators. We recorded subthalamic activity from seven PD patients at rest and during repetitive movements in four conditions: after withdrawal of dopaminergic medication and DBS, with medication only, with DBS only, and with simultaneous medication and DBS. Medication and DBS showed additive effects in improving motor performance. Distinct effects of each therapy were seen in subthalamic recordings, with medication primarily suppressing low beta activity (13–20 Hz) and DBS being associated with a broad decrease in beta band activity (13–35 Hz). Movement suppressed beta band activity compared to rest. This suppression was most prominent when combining medication with DBS and correlated with motor improvement within patients. We conclude that DBS and medication have distinct effects on subthalamic beta activity during both rest and movement, which might explain their additive clinical effects as well as their difference in side-effect profiles. Importantly, subthalamic beta activity significantly correlated with motor symptoms across all conditions, highlighting its validity as a feedback signal for closed-loop DBS.