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Bistable systems

Giulio Ragazzon, Alberto Credi, Benoit Colasson
Bistable [2]rotaxanes in which the affinities of the two stations can be reversed form the basis of molecular shuttles. Gaining quantitative information on such rotaxanes in which the ring distribution between the two stations is largely nonsymmetric has proven to be very challenging. Here we report on two independent experimental methodologies - based on luminescence lifetime measurement and acid-base titrations - to determine the relative populations of the two co-conformations of a [2]rotaxane. The assays yield convergent results and are sensitive enough to measure an equilibrium constant (K ~ 4000) out of reach for NMR spectroscopy...
December 5, 2016: Chemistry: a European Journal
Che-Chi Shu, Chen-Chao Yeh, Wun-Sin Jhang, Shih-Chiang Lo
The stochastic nature of gene regulatory networks described by Chemical Master Equation (CME) leads to the distribution of proteins. A deterministic bistability is usually reflected as a bimodal distribution in stochastic simulations. Within a certain range of the parameter space, a bistable system exhibits two stable steady states, one at the low end and the other at the high end. Consequently, it appears to have a bimodal distribution with one sub-population (mode) around the low end and the other around the high end...
2016: PloS One
Satoru Mochida, Scott Rata, Hirotsugu Hino, Takeharu Nagai, Béla Novák
The abrupt and irreversible transition from interphase to M phase is essential to separate DNA replication from chromosome segregation. This transition requires the switch-like phosphorylation of hundreds of proteins by the cyclin-dependent kinase 1 (Cdk1):cyclin B (CycB) complex. Previous studies have ascribed these switch-like phosphorylations to the auto-activation of Cdk1:CycB through the removal of inhibitory phosphorylations on Cdk1-Tyr15 [1, 2]. The positive feedback in Cdk1 activation creates a bistable switch that makes mitotic commitment irreversible [2-4]...
November 15, 2016: Current Biology: CB
Denggui Fan, Suyu Liu, Qingyun Wang
Epileptic absence seizure characterized by the typical 2-4 Hz spike-wave discharges (SWD) are known to arise due to the physiologically abnormal interactions within the thalamocortical network. By introducing a second inhibitory neuronal population in the cortical system, here we propose a modified thalamocortical field model to mathematically describe the occurrences and transitions of SWD under the mutual functions between cortex and thalamus, as well as the disinhibitory modulations of SWD mediated by the two different inhibitory interneuronal populations...
November 23, 2016: Scientific Reports
Pranay Podder, Dhiman Mallick, Andreas Amann, Saibal Roy
Ambient mechanical vibrations have emerged as a viable energy source for low-power wireless sensor nodes aiming the upcoming era of the 'Internet of Things'. Recently, purposefully induced dynamical nonlinearities have been exploited to widen the frequency spectrum of vibration energy harvesters. Here we investigate some critical inconsistencies between the theoretical formulation and applications of the bistable Duffing nonlinearity in vibration energy harvesting. A novel nonlinear vibration energy harvesting device with the capability to switch amidst individually tunable bistable-quadratic, monostable-quartic and bistable-quartic potentials has been designed and characterized...
November 22, 2016: Scientific Reports
Kevin Montagne, Guillaume Gines, Teruo Fujii, Yannick Rondelez
Molecular programming takes advantage of synthetic nucleic acid biochemistry to assemble networks of reactions, in vitro, with the double goal of better understanding cellular regulation and providing information-processing capabilities to man-made chemical systems. The function of molecular circuits is deeply related to their topological structure, but dynamical features (rate laws) also play a critical role. Here we introduce a mechanism to tune the nonlinearities associated with individual nodes of a synthetic network...
November 15, 2016: Nature Communications
Jing Li, T C H Liew
We propose theoretically a photonic Turing machine based on cellular automata in arrays of nonlinear cavities coupled with artificial gauge fields. The state of the system is recorded making use of the bistability of driven cavities, in which losses are fully compensated by an external continuous drive. The sequential update of the automaton layers is achieved automatically, by the local switching of bistable states, without requiring any additional synchronization or temporal control.
October 31, 2016: Optics Express
Mostafa Sahrai, Solmaz Ebadollahi-Bakhtevar, Hamed Sattari
A compact design for semiconductor cavities including coupled AlGaN/AlGaAs quantum wells is proposed for all-optical switching of the bistability process. First, physical and geometrical parameters are optimized to engineer the conducting electrons' energy levels in the quantum wells. Then, finite element simulations based on Schrödinger equations are executed to estimate the states of the charge carriers for AlGaN/AlGaAs as the active region. Next, the optical coupling and pumping fields are applied to the active region to both initiate the bistability and facilitate its real-time control...
October 1, 2016: Applied Optics
Ruben Perez-Carrasco, Pilar Guerrero, James Briscoe, Karen M Page
During tissue development, patterns of gene expression determine the spatial arrangement of cell types. In many cases, gradients of secreted signalling molecules-morphogens-guide this process by controlling downstream transcriptional networks. A mechanism commonly used in these networks to convert the continuous information provided by the gradient into discrete transitions between adjacent cell types is the genetic toggle switch, composed of cross-repressing transcriptional determinants. Previous analyses have emphasised the steady state output of these mechanisms...
October 2016: PLoS Computational Biology
Yunshun Zhang, Rencheng Zheng, Keisuke Shimono, Tsutomu Kaizuka, Kimihiko Nakano
The collection of clean power from ambient vibrations is considered a promising method for energy harvesting. For the case of wheel rotation, the present study investigates the effectiveness of a piezoelectric energy harvester, with the application of stochastic resonance to optimize the efficiency of energy harvesting. It is hypothesized that when the wheel rotates at variable speeds, the energy harvester is subjected to on-road noise as ambient excitations and a tangentially acting gravity force as a periodic modulation force, which can stimulate stochastic resonance...
October 17, 2016: Sensors
Evgeniy Khain, Leonard M Sander
The granular Leidenfrost effect [B. Meerson, et al., Phys. Rev. Lett. 91, 024301 (2003)PRLTAO0031-900710.1103/PhysRevLett.91.024301; P. Eshuis et al., Phys. Rev. Lett. 95, 258001 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.258001] is the levitation of a mass of granular matter when a wall below the grains is vibrated, giving rise to a hot granular gas below the cluster. We find by simulation that for a range of parameters the system is bistable: the levitated cluster can occasionally break and give rise to two clusters and a hot granular gas above and below...
September 2016: Physical Review. E
Song Feng, Meritxell Sáez, Carsten Wiuf, Elisenda Feliu, Orkun S Soyer
Bistability, and more generally multistability, is a key system dynamics feature enabling decision-making and memory in cells. Deciphering the molecular determinants of multistability is thus crucial for a better understanding of cellular pathways and their (re)engineering in synthetic biology. Here, we show that a key motif found predominantly in eukaryotic signalling systems, namely a futile signalling cycle, can display bistability when featuring a two-state kinase. We provide necessary and sufficient mathematical conditions on the kinetic parameters of this motif that guarantee the existence of multiple steady states...
October 2016: Journal of the Royal Society, Interface
S Bozdech, K Krischer, D A Crespo-Yapur, E Savinova, A Bonnefont
The formation of a self-organized spatial domain during current-controlled CO oxidation, a kinetically bistable reaction, is investigated experimentally and by deterministic simulations as a function of the electrode size and of the supporting electrolyte concentration. Decreasing the microelectrode size leads to the suppression of the spatial instability at the electrode and thus stabilizes the S-NDR branch of the reaction. The critical microelectrode size capable of supporting sustained domain formation is shown to be strongly affected by the sulfuric acid concentration, the characteristic time of the positive feedback loop increasing with the sulfate concentration...
September 16, 2016: Faraday Discussions
Sergey N Semenov, Lewis J Kraft, Alar Ainla, Mengxia Zhao, Mostafa Baghbanzadeh, Victoria E Campbell, Kyungtae Kang, Jerome M Fox, George M Whitesides
Networks of organic chemical reactions are important in life and probably played a central part in its origin. Network dynamics regulate cell division, circadian rhythms, nerve impulses and chemotaxis, and guide the development of organisms. Although out-of-equilibrium networks of chemical reactions have the potential to display emergent network dynamics such as spontaneous pattern formation, bistability and periodic oscillations, the principles that enable networks of organic reactions to develop complex behaviours are incompletely understood...
September 28, 2016: Nature
Pilkee Kim, Minh Sang Nguyen, Ojin Kwon, Young-Jin Kim, Yong-Jin Yoon
A system of magnetically coupled oscillators has been recently considered as a promising compact structure to integrate multiple bistable energy harvesters (BEHs), but its design is not straightforward owing to its varying potential energy pattern, which has not been understood completely yet. This study introduces the concept of phase-dependent dynamic potential in a magnetically coupled BEH system with two degrees of freedom (DOFs) to explain the underlying principle of the complicated dynamics of the system...
September 28, 2016: Scientific Reports
Daozhou Gao, Travis C Porco, Shigui Ruan
A susceptible-infectious-susceptible (SIS) epidemic model that describes the coinfection and cotransmission of two infectious diseases spreading through a single population is studied. The host population consists of two subclasses: susceptible and infectious, and the infectious individuals are further divided into three subgroups: those infected by the first agent/pathogen, the second agent/pathogen, and both. The basic reproduction numbers for all cases are derived which completely determine the global stability of the system if the presence of one agent/pathogen does not affect the transmission of the other...
October 1, 2016: Journal of Mathematical Analysis and Applications
Nicolas Perrin
Sex-determining factors are usually assumed to be either genetic or environmental. The present paper aims at drawing attention to the potential contribution of developmental noise, an important but often-neglected component of phenotypic variance. Mutual inhibitions between male and female pathways make sex a bistable equilibrium, such that random fluctuations in the expression of genes at the top of the cascade are sufficient to drive individual development toward one or the other stable state. Evolutionary modeling shows that stochastic sex determinants should resist elimination by genetic or environmental sex determinants under ecologically meaningful settings...
September 19, 2016: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
Sayuri K Hahl, Andreas Kremling
In the mathematical modeling of biochemical reactions, a convenient standard approach is to use ordinary differential equations (ODEs) that follow the law of mass action. However, this deterministic ansatz is based on simplifications; in particular, it neglects noise, which is inherent to biological processes. In contrast, the stochasticity of reactions is captured in detail by the discrete chemical master equation (CME). Therefore, the CME is frequently applied to mesoscopic systems, where copy numbers of involved components are small and random fluctuations are thus significant...
2016: Frontiers in Genetics
A V Yulin, A Aladyshkina, A S Shalin
The dynamics of domain walls in optical bistable systems with pump and loss is considered. It is shown that an oscillating component of the pump affects the average drift velocity of the domain walls. The cases of harmonic and biharmonic pumps are considered. It is demonstrated that in the case of biharmonic pulse the velocity of the domain wall can be controlled by the mutual phase of the harmonics. The analogy between this phenomenon and the ratchet effect is drawn. Synchronization of the moving domain walls by the oscillating pump in discrete systems is studied and discussed...
August 2016: Physical Review. E
E A Gopalakrishnan, J Tony, E Sreelekha, R I Sujith
We study the influence of noise in a prototypical thermoacoustic system, which represents a nonlinear self-excited bistable oscillator. We analyze the time series of unsteady pressure obtained from a horizontal Rijke tube and a mathematical model to identify the effect of noise. We report the occurrence of stochastic bifurcations in a thermoacoustic system by tracking the changes in the stationary amplitude distribution. We observe a complete suppression of a bistable zone in the presence of high intensity noise...
August 2016: Physical Review. E
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