Mechanical Feedback Control for Multicellular Tissue Size Maintenance: A Minireview

All living tissues and organs have their respective sizes, critical to various biological functions, such as development, growth, and homeostasis. As tissues and organs generally converge to a certain size, intrinsic regulatory mechanisms may be involved in the maintenance of size regulation. In recent years, important findings regarding size regulation have been obtained from diverse disciplines at the molecular and cellular levels. Here, I briefly review the size regulation of biological tissues from the perspective of control systems. This minireview focuses on how feedback systems engage in tissue size maintenance through the mechanical interactions of constituent cell collectives through intracellular signaling. I introduce a general framework of a feedback control system for tissue size regulation, followed by two examples: maintenance of epithelial tissue volume and epithelial tube diameter. The examples deliver the idea of how cellular mechano-response works for maintaining tissue size.

Ламинарный хаос в связанных системах с запаздыванием

The possibility of the existence of laminar chaos in coupled time-delayed feedback systems is investigated. The cases of unidirectional and mutual coupling of time-delay systems are considered. It is shown for the first time that laminar chaos can exist not only in a system with a variable delay time, but also in a system with a constant delay time, if it is coupled with a system in the regime of laminar chaos.

Global Stability of Positive Discrete-time Time-varying Nonlinear Feedback Systems

The global stability of positive discrete-time time-varying nonlinear systems with time-varying scalar feedbacks is investigated. Sufficient conditions for the asymptotic stability of discrete-time positive time-varying linear systems are given. The new conditions are applied to discrete-time positive time-varying nonlinear systems with time-varying feedbacks. Sufficient conditions are established for the global stability of the discrete-time positive time-varying nonlinear systems with feedbacks.

RF system challenges for future $$\hbox {e}^+ \hbox {e}^-$$ circular colliders

The RF system is the centrepiece of any future circular lepton collider. In particular, the system is required to support the high intensity beams needed for pushing the luminosity at the lower energy regimes of future energy-frontier circular lepton colliders (e.g. for operation in the Z peak and at the WW threshold). Capturing, storing the beam and replacing energy losses from synchrotron radiation demand low frequency, low shunt resistance cavities, low number of cells and high RF power per cell. Controlling the beam both transversely and longitudinally requires sophisticated beam control and timing systems. Additional RF systems are used to ensure transverse stability (feedback systems) and to increase the luminosity (crab cavities). Operation at high energies (such as the ZH and $${\mathrm{t}{\overline{\mathrm{t}}}}$$ t t ¯ threshold) requires a very large accelerating voltage, since synchrotron radiation leads to significantly higher energy losses per turn which must be compensated. Since the RF system is to be optimised in size and energy efficiency for varying demands for the different operational modes, the spectrum of R&D challenges covers a wide range of technologies.

Artificial intelligence in constructing personalized and accurate feedback systems for students

Artificial Intelligence (AI) systems have evolved with digital learning developments to provide thriving soft groups with digital opportunities in response to feedback. When it comes to learning environments, educators’ training feedback is often used as a response recourse. Through the use of final evaluations, students receive feedback that improves their education abilities. To improve academic achievement and explore knowledge in the learning process, this section provides an AI-assisted personalized feedback system (AI-PFS). An individualized feedback system is implemented to learn more about the student’s lack of academic experience interactivity and different collaboration behaviors. According to their benchmark, PFS aims to establish a personalized and reliable feedback process for each class based on their collaborative process and learn analytics modules. It has been proposed to use multi-objective implementations to evaluate students regarding the learning results and teaching methods. With different series of questions sessions for students, AI-PFS has been designed, and the findings showed that it greatly enhances the performance rate of 95.32% with personalized and reasonable predictive.

Passive inertial damping improves high-speed gaze stabilization in hoverflies

Gaze stabilization reflexes reduce motion blur and simplify the processing of visual information by keeping the eyes level. These reflexes typically depend on estimates of the rotational motion of the body, head, and eyes, acquired by visual or mechanosensory systems. During rapid movements, there can be insufficient time for sensory feedback systems to estimate rotational motion, and additional mechanisms are required. The solutions to this common problem likely reflect an animal's behavioral repertoire. Here, we examine gaze stabilization in three families of dipteran flies, each with distinctly different flight behaviors. Through frequency response analysis based on tethered-flight experiments, we demonstrate that fast roll oscillations of the body lead to a stable gaze in hoverflies, whereas the reflex breaks down at the same speeds in blowflies and horseflies. Surprisingly, the high-speed gaze stabilization of hoverflies does not require sensory input from the halteres, their low-latency balance organs. Instead, we show how the behavior is explained by a hybrid control system that combines a sensory-driven, active stabilization component mediated by neck muscles, and a passive component which exploits physical properties of the animal's anatomy---the mass and inertia of the head. This solution requires hoverflies to have specializations of the head-neck joint that can be employed during flight. Our comparative study highlights how species-specific control strategies have evolved to support different visually-guided flight behaviors.