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Bistable systems

Rosa D Hernansaiz-Ballesteros, Luca Cardelli, Attila Csikász-Nagy
BACKGROUND: Switch-like and oscillatory dynamical systems are widely observed in biology. We investigate the simplest biological switch that is composed of a single molecule that can be autocatalytically converted between two opposing activity forms. We test how this simple network can keep its switching behaviour under perturbations in the system. RESULTS: We show that this molecule can work as a robust bistable system, even for alterations in the reactions that drive the switching between various conformations...
June 18, 2018: BMC Systems Biology
L Pickup, K Kalinin, A Askitopoulos, Z Hatzopoulos, P G Savvidis, N G Berloff, P G Lagoudakis
We realize bistability in the spinor of polariton condensates under nonresonant optical excitation and in the absence of biasing external fields. Numerical modeling of the system using the Ginzburg-Landau equation with an internal Josephson coupling between the two spin components of the condensate qualitatively describes the experimental observations. We demonstrate that polariton spin bistability strongly depends on the condensate's overlap with the exciton reservoir by tuning the excitation geometry and sample temperature...
June 1, 2018: Physical Review Letters
Albert Goldbeter
The goal of this review article is to assess how relevant is the concept of dissipative structure for understanding the dynamical bases of non-equilibrium self-organization in biological systems, and to see where it has been applied in the five decades since it was initially proposed by Ilya Prigogine. Dissipative structures can be classified into four types, which will be considered, in turn, and illustrated by biological examples: (i) multistability, in the form of bistability and tristability, which involve the coexistence of two or three stable steady states, or in the form of birhythmicity, which involves the coexistence between two stable rhythms; (ii) temporal dissipative structures in the form of sustained oscillations, illustrated by biological rhythms; (iii) spatial dissipative structures, known as Turing patterns; and (iv) spatio-temporal structures in the form of propagating waves...
July 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Linda Irons, Markus R Owen, Reuben D O'Dea, Bindi S Brook
Integrin-mediated adhesions between airway smooth muscle (ASM) cells and the extracellular matrix (ECM) regulate how contractile forces generated within the cell are transmitted to its external environment. Environmental cues are known to influence the formation, size, and survival of cell-matrix adhesions, but it is not yet known how they are affected by dynamic fluctuations associated with tidal breathing in the intact airway. Here, we develop two closely related theoretical models to study adhesion dynamics in response to oscillatory loading of the ECM, representing the dynamic environment of ASM cells in vivo...
June 5, 2018: Biophysical Journal
Stefan Vet, Sophie de Buyl, Karoline Faust, Jan Danckaert, Didier Gonze, Lendert Gelens
We theoretically study the dynamics of two interacting microbial species in the chemostat. These species are competitors for a common resource, as well as mutualists due to cross-feeding. In line with previous studies (Assaneo, et al., 2013; Holland, et al., 2010; Iwata, et al., 2011), we demonstrate that this system has a rich repertoire of dynamical behavior, including bistability. Standard Lotka-Volterra equations are not capable to describe this particular system, as these account for only one type of interaction (mutualistic or competitive)...
2018: PloS One
Luis G Lopez, Rikkert J Nap
Sensitive switching between OFF and ON states is a desirable feature in stimuli-responsive nanopores and nanochannels. In this work, we show that nanogates modified with weak polyelectrolytes can be controlled by multivalent counterions and, more remarkably, can exhibit sensitive pH-gating due to an interplay between ionic bridging and nanoconfinement. We demonstrate these general features by systematically studying the effects of Ca2+ binding on the molecular organization and transport properties of poly(acrylic acid)-functionalized nanochannels...
June 6, 2018: Physical Chemistry Chemical Physics: PCCP
Peter Helfer, Thomas R Shultz
In long-term potentiation (LTP), one of the most studied types of neural plasticity, synaptic strength is persistently increased in response to stimulation. Although a number of different proteins have been implicated in the sub-cellular molecular processes underlying induction and maintenance of LTP, the precise mechanisms remain unknown. A particular challenge is to demonstrate that a proposed molecular mechanism can provide the level of stability needed to maintain memories for months or longer, in spite of the fact that many of the participating molecules have much shorter life spans...
May 29, 2018: PLoS Computational Biology
Li Zhou, Jing-Yu Mao, Yi Ren, Jia-Qin Yang, Shi-Rui Zhang, Ye Zhou, Qiufan Liao, Yu-Jia Zeng, Haiquan Shan, Zongxiang Xu, Jingjing Fu, Yan Wang, Xiaoli Chen, Ziyu Lv, Su-Ting Han, Vellaisamy A L Roy
Inspired by the highly parallel processing power and low energy consumption of the biological nervous system, the development of a neuromorphic computing paradigm to mimic brain-like behaviors with electronic components based artificial synapses may play key roles to eliminate the von Neumann bottleneck. Random resistive access memory (RRAM) is suitable for artificial synapse due to its tunable bidirectional switching behavior. In this work, a biological spiking synapse is developed with solution processed Au@Ag core-shell nanoparticle (NP)-based RRAM...
May 27, 2018: Small
Sachi Yamaguchi, Yoh Iwasa
Various species of fish living in coral reef communities show sequential hermaphroditism, or sex change. In a typical case, an individual first matures as a female, and later, when it becomes dominant in the mating group, it becomes a male (i.e., protogynous sex change). Many species show only unidirectional changes but some of coral reef fishes exhibit bidirectional sex changes, in which even a dominant male may revert to female when a socially more dominant competitor arrives. However, bidirectional sex change has rarely been observed in natural conditions, even among those species exhibiting it under experimental conditions...
May 22, 2018: Journal of Theoretical Biology
Lianchun Yu, Zhou Shen, Chen Wang, Yuguo Yu
Selective pressure may drive neural systems to process as much information as possible with the lowest energy cost. Recent experiment evidence revealed that the ratio between synaptic excitation and inhibition (E/I) in local cortex is generally maintained at a certain value which may influence the efficiency of energy consumption and information transmission of neural networks. To understand this issue deeply, we constructed a typical recurrent Hodgkin-Huxley network model and studied the general principles that governs the relationship among the E/I synaptic current ratio, the energy cost and total amount of information transmission...
2018: Frontiers in Cellular Neuroscience
Lijie Hao, Zhuoqin Yang, Jinzhi Lei
Long-term potentiation (LTP) is a specific form of activity-dependent synaptic plasticity that is a leading mechanism of learning and memory in mammals. The properties of cooperativity, input specificity, and associativity are essential for LTP; however, the underlying mechanisms are unclear. Here, based on experimentally observed phenomena, we introduce a computational model of synaptic plasticity in a pyramidal cell to explore the mechanisms responsible for the cooperativity, input specificity, and associativity of LTP...
2018: Frontiers in Computational Neuroscience
Tian Chen, Osama R Bilal, Kristina Shea, Chiara Daraio
In most macroscale robotic systems, propulsion and controls are enabled through a physical tether or complex onboard electronics and batteries. A tether simplifies the design process but limits the range of motion of the robot, while onboard controls and power supplies are heavy and complicate the design process. Here, we present a simple design principle for an untethered, soft swimming robot with preprogrammed, directional propulsion without a battery or onboard electronics. Locomotion is achieved by using actuators that harness the large displacements of bistable elements triggered by surrounding temperature changes...
May 15, 2018: Proceedings of the National Academy of Sciences of the United States of America
Liu-Suo Wang, Ning-Xi Li, Jing-Jia Chen, Xiao-Peng Zhang, Feng Liu, Wei Wang
A positive and a negative feedback loop can induce bistability and oscillation, respectively, in biological networks. Nevertheless, they are frequently interlinked to perform more elaborate functions in many gene regulatory networks. Coupled positive and negative feedback loops may exhibit either oscillation or bistability depending on the intensity of the stimulus in some particular networks. It is less understood how the transition between the two dynamic modes is modulated by the positive and negative feedback loops...
April 2018: Physical Review. E
S A Carvalho, M L Martins
Microorganisms and plants very commonly release toxic secondary chemical compounds (allelochemicals) that inhibit or kill sensitive strains or individuals from their own or other species. In this work we study a model that describes two species interacting through allelopathic suppression and competing for resources. Employing linear stability analysis, the conditions for coexistence or extinction of species in spatially homogeneous systems were determined. We found that the borders between the regimes of bistability, coexistence, and the extinction of the weaker by the stronger competitor, are altered by allelopathic interactions...
April 2018: Physical Review. E
Saeed Khan, Hakan E Türeci
We investigate the dynamics of a microwave-driven Josephson junction capacitively coupled to a lumped-element LC oscillator. In the regime of driving where the Josephson junction can be approximated as a Kerr oscillator, this minimal nonlinear system has been previously shown to exhibit a bistability in phase and amplitude. In the present study, we characterize the full phase diagram and show that besides a parameter regime exhibiting bistability, there is also a regime of self-oscillations characterized by a frequency comb in its spectrum...
April 13, 2018: Physical Review Letters
Marco Faggian, Francesco Ginelli, Francesco Marino, Giovanni Giacomelli
Experimental evidence of an absorbing phase transition, so far associated with spatiotemporal dynamics, is provided in a purely temporal optical system. A bistable semiconductor laser, with long-delayed optoelectronic feedback and multiplicative noise, shows the peculiar features of a critical phenomenon belonging to the directed percolation universality class. The numerical study of a simple, effective model provides accurate estimates of the transition critical exponents, in agreement with both theory and our experiment...
April 27, 2018: Physical Review Letters
Susan L Denham, Dávid Farkas, Raymond van Ee, Mihaela Taranu, Zsuzsanna Kocsis, Marina Wimmer, David Carmel, István Winkler
The dynamics of perceptual bistability, the phenomenon in which perception switches between different interpretations of an unchanging stimulus, are characterised by very similar properties across a wide range of qualitatively different paradigms. This suggests that perceptual switching may be triggered by some common source. However, it is also possible that perceptual switching may arise from a distributed system, whose components vary according to the specifics of the perceptual experiences involved. Here we used a visual and an auditory task to determine whether individuals show cross-modal commonalities in perceptual switching...
May 8, 2018: Scientific Reports
Imke Spöring, Sebastian Felgner, Matthias Preuße, Denitsa Eckweiler, Manfred Rohde, Susanne Häussler, Siegfried Weiss, Marc Erhardt
Flagellum-driven motility of Salmonella enterica serovar Typhimurium facilitates host colonization. However, the large extracellular flagellum is also a prime target for the immune system. As consequence, expression of flagella is bistable within a population of Salmonella , resulting in flagellated and nonflagellated subpopulations. This allows the bacteria to maximize fitness in hostile environments. The degenerate EAL domain protein RflP (formerly YdiV) is responsible for the bistable expression of flagella by directing the flagellar master regulatory complex FlhD4 C2 with respect to proteolytic degradation...
May 1, 2018: MBio
Abby R Kroken, Camille K Chen, David J Evans, Timothy L Yahr, Suzanne M J Fleiszig
Pseudomonas aeruginosa is internalized into multiple types of epithelial cell in vitro and in vivo and yet is often regarded as an exclusively extracellular pathogen. Paradoxically, ExoS, a type three secretion system (T3SS) effector, has antiphagocytic activities but is required for intracellular survival of P. aeruginosa and its occupation of bleb niches in epithelial cells. Here, we addressed mechanisms for this dichotomy using invasive (ExoS-expressing) P. aeruginosa and corresponding effector-null isogenic T3SS mutants, effector-null mutants of cytotoxic P...
May 1, 2018: MBio
Christian Petermayer, Henry Dube
Indigoid photoswitches comprise a class of chromophores that are derived from the parent and well-known indigo dye. Different from most photoswitches their core structures absorb in the visible region of the spectrum in both isomeric states even without substitutions, which makes them especially interesting for applications not tolerant of high-energy UV light. Also different from most current photoswitching systems, they provide highly rigid structures that undergo large yet precisely controllable geometry changes upon photoisomerization...
May 15, 2018: Accounts of Chemical Research
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