Inherent Feedback Research Articles

Active Acoustics with a Phase Cancelling Modal Reverberator

Active acoustics (AA) systems are used to electronically modify the acoustics of a room (e.g., in live music venues). AA systems have an inherent feedback component and can suffer from instability and coloration artifacts resulting from too high feedback gains. State-of-the-art methods can improve system stability and coloration, usually at the cost of complex implementations and long parameter-tuning sessions. They can also cause sound artifacts due to time-varying components, limiting the enhancement at low frequencies. This work proposes a time-invariant feedback attenuation method for low frequencies based on a modal reverberator. The attenuation is achieved through destructive acoustic interference, obtained via phase shifts between the input and output signals. The analyzed frequency range is 0–500 Hz, where the room transfer functions are considered highly invariant over time. The results show a gain-before-instability increase of more than 5 dB for a modal reverberator with high mode density in this frequency range. The improvement is also stable for low-magnitude changes in the room transfer functions over time. The proposed method provides a robust AA system with artificial reverberation for the low-frequency range and can be used alongside other established methods.

Food Preservation in the Industrial Revolution Epoch: Innovative High Pressure Processing (HPP, HPT) for the 21st-Century Sustainable Society.

The paper presents the 'progressive review' for high pressure preservation/processing (HPP) (cold pasteurization) of foods and the next-generation high-pressure and high temperature (HPHT, HPT) food sterilization technologies. It recalls the basics of HPP and HPT, showing their key features and advantages. It does not repeat detailed results regarding HPP and HPT implementations for specific foods, available in numerous excellent review papers. This report focuses on HPP and HPT-related issues that remain challenging and can hinder further progress. For HPP implementations, the reliable modeling of microorganisms' number decay after different times of high pressure treatment or product storage is essential. This report indicates significant problems with model equations standard nonlinear fitting paradigm and introduces the distortion-sensitive routine enabling the ultimate validation. An innovative concept based on the barocaloric effect is proposed for the new generation of HPT technology. The required high temperature appears only for a strictly defined short time period controlled by the maximal pressure value. Results of the feasibility test using neopentyl glycol as the barocaloric medium are presented. Attention is also paid to feedback interactions between socioeconomic and technological issues in the ongoing Industrial Revolution epoch. It indicates economic constraints for HPP and HPT developments and emerging business possibilities. The discussion recalls the inherent feedback interactions between technological and socioeconomic innovations as the driving force for the Industrial Revolution epoch.

Direct sampling of femtosecond electric-field waveforms from an optical parametric oscillator

Detecting the electric-field waveform of an optical pulse from the terahertz to the visible spectral domain provides a complete characterization of the average field waveform and holds great potential for quantum optics, time-domain (including frequency-comb) spectroscopy, high-harmonic generation, and attosecond science, to name a few. The field-resolved measurements can be performed using electro-optic sampling, where a laser pulse is characterized through an interaction with another pulse of a much shorter duration. The measured pulse train must consist of identical pulses, including their equal carrier-envelope phase (CEP). Due to the limited coverage of broadband laser gain media, creating CEP-stable pulse trains in the mid-infrared typically requires nonlinear frequency conversion, such as difference frequency generation, optical parametric amplification, or optical rectification. These techniques operate in a single-pass geometry, often limiting efficiency. In this work, we demonstrate field-resolved analysis of the pulses generated in a resonant system, an optical parametric oscillator (OPO). Due to the inherent feedback, this device exhibits a relatively high conversion efficiency at a given level of input power. By electro-optic sampling, we prove that a subharmonic OPO pumped with CEP-stable few-cycle fiber-laser pulses generates a CEP-stable mid-infrared output. The full amplitude and phase information renders dispersion control straightforward. We also confirm the existence of an exotic “flipping” state of the OPO directly in the time domain, where the electric field of consecutive pulses has the opposite sign.

Effect of Vibrotactile Feedback on the Control of the Interaction Force of a Supernumerary Robotic Arm

Supernumerary robotic limbs are mainly designed to augment the physical capabilities of able-bodied individuals, in a wide range of contexts from body support to surgery. When they are worn as wearable devices, they naturally provide inherent feedback due to the mechanical coupling with the human body. The user can, thus, perceive the interaction with the environment by relying on a combination of visual and inherent feedback. However, these can be inefficient in accomplishing complex tasks, particularly in the case of visual occlusion or variation in the environment stiffness. Here, we investigated whether, in a force-regulation task using a wearable supernumerary robotic arm (SRA), additional vibrotactile feedback can increase the control performance of participants compared to the inherent feedback. Additionally, to make the scenario more realistic, we introduced variations in the SRA’s kinematic posture and in the environment stiffness. Notably, our findings revealed a statistically significant improvement in user performance over all the evaluated metrics while receiving additional vibrotactile feedback. Compared to inherent feedback alone, the additional vibrotactile feedback allowed participants to exert the required force faster (p < 0.01), to maintain it for longer (p < 0.001), and with lower errors (p < 0.001). No discernible effects related to the SRA’s posture or environment stiffness were observed. These results proved the benefits of providing the user with additional vibrotactile feedback to convey the SRA’s force during interaction tasks.

To addend or not to addend? Exploring medical student and resident perceptions of the use of student notes for billing purposes

Background: Clinical documentation is an essential skill for which medical students are often not prepared. Changes in documentation rules for medical students allow the utilization of student notes for official billing purposes, which requires investigation for possible educational intervention. Potential benefits to medical learners and impacts on feasibility and workflow must be explored. Methods: Pediatric clerkship students were randomly assigned to one of two inpatient hospitalist teams: control group students wrote daily notes that were not addended or used for billing; study group students’ notes were used for billing after being addended by resident and faculty members. At the end of the clerkship, residents and medical students completed surveys and focus groups. Results: In surveys, residents from both groups reported similar satisfaction with medical student documentation. Study group students spent more time reviewing notes, found the feedback from residents beneficial, and felt their experience with documentation was more valuable than control group students. Focus group themes included: educational value for learners, increased student engagement, possible negative impact on workflow, inherent feedback in reviewing edits, the importance of clear communication, and minimal effects on patient care. Conclusions: Our results highlight the potential educational benefits of using student notes as official documentation and provide evidence that this practice may not negatively impact resident learners.

AhR diminishes the efficacy of chemotherapy via suppressing STING dependent type-I interferon in bladder cancer

The induction of type-I interferons (IFN-Is) is important for the efficacy of chemotherapy. By investigating the role of amino acids in regulation of IFN-I production under chemo-drug treatment in bladder cancer (BC) cells, we find an inherent AhR-dependent negative feedback to restrain STING signaling and IFN-I production. Mechanistically, in a ligand dependent manner, AhR bridges STING and CUL4B/RBX1 E3 ligase complex, facilitating STING degradation through ubiquitin-proteasome pathway. Inhibition of AhR increases STING levels and reduces tumor growth under cisplatin or STING agonist treatment. Endogenous AhR ligands are mainly consisted of tryptophan (Trp) metabolites; dietary Trp restriction, blocking the key Trp metabolism rate-limiting enzyme IDO1 or inhibition of cellular Trp importation also show similar effect as AhR inhibition. Clinically, BC patients with higher intratumoral expression of AhR or stronger intratumoral Trp metabolism (higher IDO1 or Kyn levels) that lead to higher AhR activation show worse response rate to neoadjuvant chemotherapy (NAC).

Analysis of coupled two-phase natural circulation loops by developing HEM and DFM based numerical models

The coupled two-phase natural circulation loop based passive systems find numerous applications, particularly in nuclear reactors where safety is paramount. However, the loops coupling, system conditions (specific to the reactor type), and inherent coupled loops feedback make their dynamics more complex. Hence, the models used should be capable of predicting such intricate coupled dynamics for precise forecasting of passive systems performance. With this objective, the present analyses deliberate the transients of such coupled two-phase loops linked to coupling configurations and operating conditions. Generalized two-phase models based on Homogeneous Equilibrium (HEM) and Drift Flux (DFM) with flashing, wall and fluid conduction, water-steam property formulation, etc., are developed and employed. Validation studies substantiate the prediction capability of these models for various cooler-heater orientations. Subsequently, predicted the start-up transients of vertically and horizontally coupled two-phase loops. The analyses revealed that coupling configurations, heater-cooler orientations and system conditions significantly influence the coupled loops. Further, the influences of various geometrical and operating parameters on the dynamics of coupled loops are investigated. It elucidated the differences in the parameter's effect on single-phase and two-phase coupled loops. The study also identified the vital parameters strongly influencing the coupled loops based on sensitivity analysis. The models and findings will be applied to evaluate the performance of coupled loop-based passive safety systems in nuclear reactors.

The sensorimotor system modulates muscular co-contraction relative to visuomotor feedback responses to regulate movement variability.

The naturally occurring variability in our movements often poses a significant challenge when attempting to produce precise and accurate actions, which is readily evident when playing a game of darts. Two differing, yet potentially complementary, control strategies that the sensorimotor system may use to regulate movement variability are impedance control and feedback control. Greater muscular co-contraction leads to greater impedance that acts to stabilize the hand, while visuomotor feedback responses can be used to rapidly correct for unexpected deviations when reaching toward a target. Here, we examined the independent roles and potential interplay of impedance control and visuomotor feedback control when regulating movement variability. Participants were instructed to perform a precise reaching task by moving a cursor through a narrow visual channel. We manipulated cursor feedback by visually amplifying movement variability and/or delaying the visual feedback of the cursor. We found that participants decreased movement variability by increasing muscular co-contraction, aligned with an impedance control strategy. Participants displayed visuomotor feedback responses during the task but, unexpectedly, there was no modulation between conditions. However, we did find a relationship between muscular co-contraction and visuomotor feedback responses, suggesting that participants modulated impedance control relative to feedback control. Taken together, our results highlight that the sensorimotor system modulates muscular co-contraction, relative to visuomotor feedback responses, to regulate movement variability and produce accurate actions.NEW & NOTEWORTHY The sensorimotor system has the constant challenge of dealing with the naturally occurring variability in our movements. Here, we investigated the potential roles of muscular co-contraction and visuomotor feedback responses to regulate movement variability. When we visually amplified movements, we found that the sensorimotor system primarily uses muscular co-contraction to regulate movement variability. Interestingly, we found that muscular co-contraction was modulated relative to inherent visuomotor feedback responses, suggesting an interplay between impedance and feedback control.

Policy mixes across vertical levels of governance in the EU: The case of the sustainable energy transition in Latvia

The European Green Deal requires policy alignment horizontally across policy areas but also vertically across governance levels. Accordingly, the diversity of actors and their preferences can hinder sociotechnical transitions. We, therefore, ask: How do policy mixes unfold across vertical scales of governance in sociotechnical transitions? We analyse vertical policy mix characteristics, considering consistency, coherence, comprehensiveness, and credibility, and the inherent feedback loops between politics and policy. Drawing on empirical evidence from Latvia, gathered through content analysis and interviews with senior stakeholders, we highlight two key findings: First, friction points in policy coherence between the national-local governance levels feed back into the vertical policy mix, as EU-level policy strategies are not substantiated with corresponding policy instruments. Second, the lack of political commitment to the transition at the national level perpetuates friction points in comprehensiveness and credibility of the vertical policy mix, hindering transition processes.

Characterizing the Force-Motion Tradeoff in Body-Powered Transmission Design.

Upper-limb prosthesis users continue to reject devices despite continued research efforts. Today, the passive topology of body-powered prehensors, which physically transmits grasp force and position data between user and device, results in improved performance over myoelectric alternatives. However, the loads and postures on the user's body also result in discomfort, fatigue, and worsened grasp force control. Despite the long history and everyday adoption of body-powered prehensors in society, the measurement of how specific body loads and postures affect grasp performance and user experience has yet to be systematically studied. In this work, we present a body-powered prosthesis emulator to independently change required input forces and motions to study the positive and negative effects provided by the inherent haptic feedback. Using a simulated grasping task, we collect functional and qualitative data from 15 participants using a shoulder harness interface. Outcomes show that lowering required input motions and forces independently reduces negative outcomes, with diminishing returns below 1:1 output mappings. Given the tradeoff between force and motion in traditional body-powered transmissions, a transmission ratio of 1:1 balances both requirements. The purpose of this study is to inform future prehensor designs that leverage the transparency of body-power to deliver high functionality while mitigating user discomfort.

A Physics-Guided Data-Driven Feedforward Tracking Controller for Systems With Unmodeled Dynamics—Applied to 3D Printing

A hybrid (i.e., physics-guided data-driven) feedforward tracking controller is proposed for systems with unmodeled linear or nonlinear dynamics. The proposed controller is based on the filtered basis functions (FBF) approach, and hence called a hybrid FBF controller. It formulates the feedforward control input to a system as a linear combination of a set of basis functions whose coefficients are selected to minimize tracking errors. To predict the system response and thereby the tracking errors, the basis functions are filtered using a combination of two linear models. The first model is physics-based and remains unaltered during the execution of the controller, while the second is data-driven and is continuously updated during the execution of the controller. To ensure its practicality and safe learning, the proposed hybrid FBF controller is equipped with the abilities to handle delays in data acquisition and to detect impending instability due to its inherent data-driven feedback loop. The effectiveness of the hybrid FBF controller is demonstrated via application to vibration compensation of a 3D printer with unmodeled linear and nonlinear dynamics. Thanks to the proposed hybrid FBF controller, the tracking accuracy of the 3D printer and the print quality are both significantly improved in experiments involving high-speed printing, compared to standard FBF controller that does not incorporate a data-driven model. Furthermore, the ability of the hybrid FBF controller to detect, and hence to potentially avoid, impending instability is demonstrated offline using data collected online from experiments.

A 6-GHz Bandwidth Input Buffer Based on AC-Coupled Flipped Source Follower for 12-bit 8-GS/s ADC in 28-nm CMOS

This brief presents an input buffer based on AC-coupled flipped source follower (SF) for a 12-bit 8-GS/s time-interleaved (TI) ADC. The flipped SF can drive the ADC’s sampling capacitance with high linearity because the input MOS’s drain current is almost independent of the load capacitance. In addition, the inherent feedback reduces the input buffer’s output impedance, which improves the bandwidth when driving the complex wiring network of TI ADCs. The proposed AC-coupling structure enlarges the input signal range of the flipped SF extensively, making it practical to be used for high-speed ADCs. A compensation capacitor is used to compensate for the nonlinear parasitic capacitance of the input MOS to further improve the linearity. An 8-channel 12-bit 8GS/s TI ADC prototype with the proposed input buffer is implemented in a 28-nm mixed-signal CMOS process. Measured results show that the input bandwidth of the input buffer exceeds 6 GHz with 137-mW power supply. The ADC achieves SFDR of 68 dBFS and SNDR of 54.9 dB with 3.9-GHz, −1-dBFS input signal under 8-GS/s sampling rate. The total power consumption of the ADC is 1.05 W.

Genetic tuning of β-carotene oxygenase-1 activity rescues cone photoreceptor function in STRA6-deficient mice.

Rod and cone photoreceptors in the retina mediate dim light and daylight vision, respectively. Despite their distinctive functions, rod and cone visual pigments utilize the same vitamin A-derived chromophore. To sustain vision, vitamin A precursors must be acquired in the gut, metabolized, and distributed to the eyes. Deficiencies in this pathway in inherited ocular disease states deplete cone photoreceptors from chromophore and eventually lead to cell death, whereas the more abundant rod photoreceptors are less affected. However, pathways that support cone function and survival under such conditions are largely unknown. Using biochemical, histological, and physiological approaches, we herein show that intervention with β-carotene in STRA6-deficient mice improved chromophore supply to cone photoreceptors. Relieving the inherent negative feedback regulation of β-carotene oxygenase-1 activity in the intestine by genetic means further bolstered cone photoreceptor functioning in the STRA6-deficient eyes. A vitamin A-rich diet, however, did not improve cone photoreceptor function in STRA6-deficiency. We provide evidence that the beneficial effect of β-carotene on cones results from favorable serum kinetics of retinyl esters in lipoproteins. The respective alterations in lipoprotein metabolism maintained a steady supply of retinoids to the STRA6-deficient eyes, which ameliorated the competition for chromophore between rod and cone photoreceptors. Together, our study elucidates a cone photoreceptor-survival pathway and unravels an unexpected metabolic connection between the gut and the retina.

Startup analyses of a megawatt heat pipe cooled reactor

Heat pipe cooled reactors experience temperature rises of up to 800 K during startup. The in-core heat pipes and the energy conversion system are initially frozen, which leads to a highly coupled heat transfer system that has significant safety challenges. This work modeled the system startup using a two-dimensional heat pipe model and an open-air Brayton cycle model coupled to the Heat Pipe Reactor TRANsient analysis code, HPRTRAN. The heat pipe model was validated with startup experiments showing that the predicted heat pipe wall temperature was within 30 K of the measured temperatures. The Brayton cycle model was validated against experimental data in the literature. The analysis code was then used to analyze a megawatt heat pipe reactor connected to an open-air Brayton cycle, which was used to study the influence of the external reactivity and the inherent feedback on the startup process. The simulations show that the reactor startup process is sensitive to the heat pipe operating state. The startup process can be divided into the subcritical stage, heat pipe startup stage, and increasing power stage. The power peak amplitudes are significantly reduced by slowing the angular speed of the control drum. Reducing the control drum angular speed from 0.1°/min to 0.05°/min reduced the first power peak from 2000 kW to 1000 kW. A modified reactor startup control strategy was then developed that ensures the core safety with the reactivity introduced in steps. Smaller reactivity insertions reduce the power peaks during the initial startup but lead to much longer startup times. A reasonable balance was obtained by repeated insertions of either 30 pcm or 60 pcm for safe startups of the heat pipe cooled reactor.

Preliminary Analysis of Reactivity Feedbacks for Inner-Side Chromium Coating

Abstract Protective coatings were proposed as near-term concepts to enhance the accident tolerance of nuclear fuel claddings; it is expected to improve corrosion resistance in severe events, and enhance cladding performance during normal operation, without introducing major design changes. Various aspects such as corrosion resistance, thermal and neutronic performances are being evaluated. However, the fact that inner uncoated side of fuel cladding may expose to the oxidizing environment under some circumstances is still a concern. Thus, a complementary inner-side coating was proposed. Metallic chromium is extensively studied as a potential coating material, and showed promising performance. Neutronic penalties are expected if chromium used as protective coating. In this study, reactor's inherent safety feedback, when chromium coatings used for fuel claddings inner-side protection, is evaluated and compared with the case of using external coatings. These parameters have not been studied before. Five different coating thicknesses were used in this evaluation. Results showed that inner side coatings will induce less negative moderator temperature feed backs, while feedback to changes in fuel temperature will be more negative than the reference uncoated case. Boron coefficient was found to be less negative compared to the reference. It was found that each coating thickness will induce unique changes in neutrons flux; generally, there will be reduction in thermal portion of neutron flux, which will be less for the case of inner-side coatings, when compared to external coatings. The magnitude of feedback varies from thickness to another. Reactivity feedbacks also calculated for some cases where inner and external coatings used simultaneously, results showed similar behavior, with the magnitude varying from a combination to another. The presence of chromium coatings will introduce some changes in reactor's neutron flux; nevertheless, the reactor will still keep its inherent negative feedback to changes in different operation parameters studied.

The System of Public Power and Integration of Cybernetic and Synergetic Approaches in Public Administration

The paper examines the cyclical process of alternating periods of centralization and decentralization in the state administration of the USSR and post-Soviet Russia. Based on the system-informational understanding of public administration, the author identifies the causes of this phenomenon that are associated with certain advantages and disadvantages in both centralization and decentralization of administration. It is shown that implementation of a particular style of administration is determined by its relevance in a specific economic and social situation. At the same time, in order to ensure the effectiveness and sustainability of the public administration system, it is usually advisable to simultaneously use several administation styles: centralization, partial decentralization, self-government. Since centralized models are associated with the implementation of cybernetic, and self-government — synergetic approaches, the author analyzes the essence of cybernetic and synergetic control systems, their similarities and differences, the mechanisms of their functioning and the features of their inherent feedback channels. The paper examines the prospects of synergetic approaches in public administration. The author notes that unlike cybernetic management models that are more effective in large territorial and industrial structures, synergetic systems provide a tangible advantage for small entities. A serious issue in the integration of these two models of administrative activity is the need for an optimal combination of appropriate information resources. The paper shows that one of the solutions to the problem is the development of a unified system of public power in the Russian Federation, as it is able to largely ensure the integration of cybernetic and synergetic approaches in public administration.

Bistable reflection and beam shifts with excitation of surface plasmons in a saturable absorbing medium.

We investigate the nonlinear reflection of a light beam from a Kretschmann configuration with saturable absorbing medium. The absorption of medium has direct influence on the intrinsic loss of the system, thus affecting the reflectivity and the phase variation when the surface plasmons are resonantly excited. As the incident power changes, the reflectivity can be switched between high and low values and exhibits absorptive optical bistability as a result of the inherent positive feedback by the intensity-dependent saturation effect. The Goos-Hänchen and the Imbert-Fedorov shifts of the reflected beam have the same bistable behavior as the reflectance. The effects of the thickness of metal film and the linear absorption coefficient on the hysteresis loop are analyzed in detail by considering the system losses and the saturated absorption. The bistable reflection and beam shifts may have applications in all-optical devices, such as optical switching.

Analysis of the anticipated transient without scram (ATWS) initiated by emergency power mode through the full scope simulator

Abstract The integrity of the reactor coolant system is severely challenged as a result of an Emergency Power Mode – ATWS event. The purpose of this paper is to simulate the Anticipated Transient without Scram (ATWS) using the full scope simulator of Angra 2 Nuclear Power Plant with the Emergency Power Case as a precursor event. The results are discussed and will be used to examine the integrity of the reactor coolant system. In addition, the results were compared with the data presented in Final Safety Analysis Report (FSAR – Angra 2) in order to guarantee the validation of the methodology and from there analyze other precursor events of ATWS which presented only plausibility studies in FSAR – Angra 2. In this way, the aim is to provide and develop the knowledge and skill necessaries for control room operating personnel to ensure safe and reliable plant operation and stimulate information in the nuclear area through the academic training of new engineers. In the presented paper the most severe scenario is analyzed in which the Reactor Coolant System reaches its highest level of coolant pressure. This scenario is initiated by the turbine trip jointly with the loss of electric power systems (Emergency Power Mode). In addition, the failure of the reactor shutdown system occurs, i.e., control rods fail to drop into the reactor core. The reactor power is safely reduced through the inherent reactivity feedback of the moderator and fuel, together with an automatic boron injection. Several operational variables were analyzed and their profiles over time are shown in order to provide data and benchmarking references. At the end of the event, it was noted that Reactor shutdown is assured, as is the maintenance of subcriticality. Residual heat removal is ensured.

Fluorescence turn-on by photoligation - bright opportunities for soft matter materials.

Photochemical ligation has become an indispensable tool for applications that require spatially addressable functionalisation, both in biology and materials science. Interestingly, a number of photochemical ligations result in fluorescent products, enabling a self-reporting function that provides almost instantaneous visual feedback of the reaction's progress and efficiency. Perhaps no other chemical reaction system allows control in space and time to the same extent, while concomitantly providing inherent feedback with regard to reaction success and location. While photoactivable fluorescent properties have been widely used in biology for imaging purposes, the expansion of the array of photochemical reactions has further enabled its utility in soft matter materials. Herein, we concisely summarise the key developments of fluorogenic-forming photoligation systems and their emerging applications in both biology and materials science. We further summarise the current challenges and future opportunities of exploiting fluorescent self-reporting reactions in a wide array of chemical disciplines.

Augmented KCa2.3 Channel Feedback Regulation of Oxytocin Stimulated Uterine Strips from Nonpregnant Mice.

Uterine contractions prior to 37 weeks gestation can result in preterm labor with significant risk to the infant. Current tocolytic therapies aimed at suppressing premature uterine contractions are largely ineffective and cause serious side effects. Calcium (Ca2+) dependent contractions of uterine smooth muscle are physiologically limited by the opening of membrane potassium (K+) channels. Exploiting such inherent negative feedback mechanisms may offer new strategies to delay labor and reduce risk. Positive modulation of small conductance Ca2+-activated K+ (KCa2.3) channels with cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA), effectively decreases uterine contractions. This study investigates whether the receptor agonist oxytocin might solicit KCa2.3 channel feedback that facilitates CyPPA suppression of uterine contractions. Using isometric force myography, we found that spontaneous phasic contractions of myometrial tissue from nonpregnant mice were suppressed by CyPPA and, in the presence of CyPPA, oxytocin failed to augment contractions. In tissues exposed to oxytocin, depletion of internal Ca2+ stores with cyclopiazonic acid (CPA) impaired CyPPA relaxation, whereas blockade of nonselective cation channels (NSCC) using gadolinium (Gd3+) had no significant effect. Immunofluorescence revealed close proximity of KCa2.3 channels and ER inositol trisphosphate receptors (IP3Rs) within myometrial smooth muscle cells. The findings suggest internal Ca2+ stores play a role in KCa2.3-dependent feedback control of uterine contraction and offer new insights for tocolytic therapies.