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Bistable systems

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https://www.readbyqxmd.com/read/29473072/numerical-experimental-observation-of-shape-bistability-of-red-blood-cells-flowing-in-a-microchannel
#1
Achim Guckenberger, Alexander Kihm, Thomas John, Christian Wagner, Stephan Gekle
Red blood cells flowing through capillaries assume a wide variety of different shapes owing to their high deformability. Predicting the realized shapes is a complex field as they are determined by the intricate interplay between the flow conditions and the membrane mechanics. In this work we construct the shape phase diagram of a single red blood cell with a physiological viscosity ratio flowing in a microchannel. We use both experimental in vitro measurements as well as 3D numerical simulations to complement the respective other one...
February 23, 2018: Soft Matter
https://www.readbyqxmd.com/read/29467641/propensity-for-bistability-of-bursting-and-silence-in-the-leech-heart-interneuron
#2
Tatiana Dashevskiy, Gennady Cymbalyuk
The coexistence of neuronal activity regimes has been reported under normal and pathological conditions. Such multistability could enhance the flexibility of the nervous system and has many implications for motor control, memory, and decision making. Multistability is commonly promoted by neuromodulation targeting specific membrane ionic currents. Here, we investigated how modulation of different ionic currents could affect the neuronal propensity for bistability. We considered a leech heart interneuron model...
2018: Frontiers in Computational Neuroscience
https://www.readbyqxmd.com/read/29463760/a-comprehensive-model-for-the-proliferation-quiescence-decision-in-response-to-endogenous-dna-damage-in-human-cells
#3
Frank S Heldt, Alexis R Barr, Sam Cooper, Chris Bakal, Béla Novák
Human cells that suffer mild DNA damage can enter a reversible state of growth arrest known as quiescence. This decision to temporarily exit the cell cycle is essential to prevent the propagation of mutations, and most cancer cells harbor defects in the underlying control system. Here we present a mechanistic mathematical model to study the proliferation-quiescence decision in nontransformed human cells. We show that two bistable switches, the restriction point (RP) and the G1/S transition, mediate this decision by integrating DNA damage and mitogen signals...
February 20, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29462989/memristic-characteristics-from-bistable-to-tristable-memory-with-controllable-charge-trap-carbon-nanotubes
#4
Lei Li, Dianzhong Wen
The incorporation of the one-dimensional carbon nanomaterial carbon nanotubes (CNTs) in poly(methyl methacrylate) (PMMA) was found to successfully develop a resistive switching. It implements memristic characteristics which shift from bistable to tristable memory. The localized current pathways in the organic nanocomposite layers for each intermediate resistive state (IRS) are attributed to the trapping mechanism consistent with the fluorescent measurements. Multi-bit organic memories have attracted considerable interest, which provide an effective way to increase the memory density per unit cell area...
February 17, 2018: Nanomaterials
https://www.readbyqxmd.com/read/29445020/trade-offs-between-microbial-growth-phases-lead-to-frequency-dependent-and-non-transitive-selection
#5
Michael Manhart, Bharat V Adkar, Eugene I Shakhnovich
Mutations in a microbial population can increase the frequency of a genotype not only by increasing its exponential growth rate, but also by decreasing its lag time or adjusting the yield (resource efficiency). The contribution of multiple life-history traits to selection is a critical question for evolutionary biology as we seek to predict the evolutionary fates of mutations. Here we use a model of microbial growth to show that there are two distinct components of selection corresponding to the growth and lag phases, while the yield modulates their relative importance...
February 14, 2018: Proceedings. Biological Sciences
https://www.readbyqxmd.com/read/29414696/dynamics-of-posttranslational-modification-systems-recent-progress-and-future-directions
#6
REVIEW
Carsten Conradi, Anne Shiu
Posttranslational modification of proteins is important for signal transduction, and hence significant effort has gone toward understanding how posttranslational modification networks process information. This involves, on the theory side, analyzing the dynamical systems arising from such networks. Which networks are, for instance, bistable? Which networks admit sustained oscillations? Which parameter values enable such behaviors? In this Biophysical Perspective, we highlight recent progress in this area and point out some important future directions...
February 6, 2018: Biophysical Journal
https://www.readbyqxmd.com/read/29410453/flip-flop-converter-of-dual-bistability-using-cavity-and-parametric-amplified-four-wave-mixing
#7
Kangkang Li, Renan Bu, Xiuxiu Wang, Haixia Chen, Dan Zhang, Xinghua Li, Yanpeng Zhang
We study the realization of dual-bistability flip-flop converter in cavity and parametrically amplified four-wave mixing (FWM) process at a four-level cavity atomic system. Using the effect of nonreciprocity optical dual-bistability, we can obtain different output multi-mode states of probe transmission signal and FWM signal. We find the channel equalization ratio and optical contrast between multi-mode states is related to the degree of dual-bistability. Besides, the degree of dual-bistability can be controlled by the input parameters (frequency detuning and powers of the dressing beams)...
February 6, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29401958/all-optical-control-of-polarization-splitting-with-a-dielectric-clad-azobenzene-liquid-crystal
#8
Hung-Chang Jau, Pei-Chieh Chou, Chun-Wei Chen, Cheng-Chang Li, Shi-Ee Leng, Chun-Hong Lee, Tsung-Hsien Lin
We report the design, fabrication, and characterization of an optically switchable polarizing beam splitter with a prism/azobenzene liquid crystal/prism hybrid structure. The beam splitter can operate in the polarization-splitting mode and the non-splitting mode. The switching between the modes is realized by the photoisomerization-induced phase transitions in the azobenzene liquid crystal, featuring all-optical control, bistability, and fast response. Such an active polarization-handling element is highly desirable as it not only simplifies and compacts sophisticated optical systems but also increases the degree of freedom in optical circuit design...
January 22, 2018: Optics Express
https://www.readbyqxmd.com/read/29401445/simulating-genetic-circuits-in-bacterial-populations-with-growth-heterogeneity
#9
Anjan Roy, Stefan Klumpp
We computationally study genetic circuits in bacterial populations with heterogeneities in the growth rate. To that end, we present a stochastic simulation method for gene circuits in populations of cells and propose an efficient implementation that we call the "Next Family Method". Within this approach, we implement different population setups, specifically Chemostat-type growth and growth in an ideal Mother Machine and show that the population structure and its statistics are different for the different setups whenever there is growth heterogeneity...
January 23, 2018: Biophysical Journal
https://www.readbyqxmd.com/read/29378933/on-the-complex-dynamics-of-savanna-landscapes
#10
Jonathan David Touboul, Ann Carla Staver, Simon Asher Levin
Simple mathematical models can exhibit rich and complex behaviors. Prototypical examples of these drawn from biology and other disciplines have provided insights that extend well beyond the situations that inspired them. Here, we explore a set of simple, yet realistic, models for savanna-forest vegetation dynamics based on minimal ecological assumptions. These models are aimed at understanding how vegetation interacts with both climate (a primary global determinant of vegetation structure) and feedbacks with chronic disturbances from fire...
January 29, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29355542/no-appendix-necessary-fecal-transplants-and-antibiotics-can-resolve-clostridium-difficile-infection
#11
Tejas Joshi, Bret D Elderd, Karen C Abbott
The appendix has been hypothesized to protect the colon against Clostridium difficile infection (CDI) by providing a continuous source of commensal bacteria that crowd out the potentially unhealthy bacteria and/or by contributing to defensive immune dynamics. Here, a series of deterministic systems comprised of ordinary differential equations, which treat the system as an ecological community of microorganisms, model the dynamics of colon microbiome. The first model includes migration of commensal bacteria from the appendix to the gut, while the second model expands this to also include immune dynamics...
April 7, 2018: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/29348614/noise-induced-bistability-in-the-fate-of-cancer-phenotypic-quasispecies-a-bit-strings-approach
#12
Josep Sardanyés, Tomás Alarcón
Tumor cell populations are highly heterogeneous. Such heterogeneity, both at genotypic and phenotypic levels, is a key feature during tumorigenesis. How to investigate the impact of this heterogeneity in the dynamics of tumors cells becomes an important issue. Here we explore a stochastic model describing the competition dynamics between a pool of heterogeneous cancer cells with distinct phenotypes and healthy cells. This model is used to explore the role of demographic fluctuations on the transitions involving tumor clearance...
January 18, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29347734/electrically-induced-structure-transition-in-nematic-liquid-crystal-droplets-with-conical-boundary-conditions
#13
V Yu Rudyak, M N Krakhalev, V S Sutormin, O O Prishchepa, V Ya Zyryanov, J-H Liu, A V Emelyanenko, A R Khokhlov
Polymer-dispersed liquid crystal composites have been a focus of study for a long time for their unique electro-optical properties and manufacturing by "bottom-up" techniques at large scales. In this paper, nematic liquid crystal oblate droplets with conical boundary conditions (CBCs) under the action of electric field were studied by computer simulations and polarized optical microscopy. Droplets with CBCs were shown to prefer an axial-bipolar structure, which combines a pair of boojums and circular disclinations on a surface...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347692/effect-of-the-correlation-between-internal-noise-and-external-noise-on-logical-stochastic-resonance-in-bistable-systems
#14
Lei Zhang, Wenbin Zheng, Fei Xie, Aiguo Song
Some noisy nonlinear systems could be exploited to operate reliable logic operation in an optimal window of noise intensity, which is termed as logical stochastic resonance (LSR). We investigated the LSR phenomenon in bistable systems when internal noise and external noise are correlated. The LSR effect is evaluated by the success probability of the obtained desired output with various combinations of logic inputs. It is shown that the or-nor, and-nand, and Latch operations still can operate reliably with the correlated internal noise and external noise...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347512/symmetry-breaking-in-two-interacting-populations-of-quadratic-integrate-and-fire-neurons
#15
Irmantas Ratas, Kestutis Pyragas
We analyze the dynamics of two coupled identical populations of quadratic integrate-and-fire neurons, which represent the canonical model for class I neurons near the spiking threshold. The populations are heterogeneous; they include both inherently spiking and excitable neurons. The coupling within and between the populations is global via synapses that take into account the finite width of synaptic pulses. Using a recently developed reduction method based on the Lorentzian ansatz, we derive a closed system of equations for the neuron's firing rates and the mean membrane potentials in both populations...
October 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347056/force-linearization-closure-for-non-markovian-langevin-systems-with-time-delay
#16
Sarah A M Loos, Sabine H L Klapp
This paper is concerned with the Fokker-Planck (FP) description of classical stochastic systems with discrete time delay. The non-Markovian character of the corresponding Langevin dynamics naturally leads to a coupled infinite hierarchy of FP equations for the various n-time joint distribution functions. Here, we present an approach to close the hierarchy at the one-time level based on a linearization of the deterministic forces in all members of the hierarchy starting from the second one. This leads to a closed equation for the one-time probability density in the steady state...
July 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347037/escape-of-coupled-brownian-particles-across-a-fluctuating-barrier
#17
R K Singh
The escape of two harmonically coupled Brownian particles across the fluctuating barrier of a bistable potential is investigated with correlated additive and multiplicative fluctuations. Positive correlations enhance the rate of escape across the barrier when the coupling is effective, whereas for weakly coupled particles, escape becomes difficult. It is found that the system exhibits the phenomenon of resonant activation when the rate of barrier fluctuations is comparable to the relaxation time in the bistable potential...
September 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347036/front-propagation-in-weakly-subcritical-pattern-forming-systems
#18
Benjamin C Ponedel, Hsien-Ching Kao, Edgar Knobloch
The speed and stability of fronts near a weakly subcritical steady-state bifurcation are studied, focusing on the transition between pushed and pulled fronts in the bistable Ginzburg-Landau equation. Exact nonlinear front solutions are constructed and their stability properties investigated. In some cases, the exact solutions are stable but are not selected from arbitrary small amplitude initial conditions. In other cases, the exact solution is unstable to modulational instabilities which select a distinct front...
September 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347033/basins-of-attraction-of-the-bistable-region-of-time-delayed-cutting-dynamics
#19
Yao Yan, Jian Xu, Marian Wiercigroch
This paper investigates the effects of bistability in a nonsmooth time-delayed dynamical system, which is often manifested in science and engineering. Previous studies on cutting dynamics have demonstrated persistent coexistence of chatter and chatter-free responses in a bistable region located in the linearly stable zone. As there is no widely accepted definition of basins of attraction for time-delayed systems, bistable regions are coined as unsafe zones (UZs). Hence, we have attempted to define the basins of attraction and stability basins for a typical delayed system to get insight into the bistability in systems with time delays...
September 2017: Physical Review. E
https://www.readbyqxmd.com/read/29330362/dynamic-modelling-of-the-mtor-signalling-network-reveals-complex-emergent-behaviours-conferred-by-deptor
#20
Thawfeek M Varusai, Lan K Nguyen
The mechanistic Target of Rapamycin (mTOR) signalling network is an evolutionarily conserved network that controls key cellular processes, including cell growth and metabolism. Consisting of the major kinase complexes mTOR Complex 1 and 2 (mTORC1/2), the mTOR network harbours complex interactions and feedback loops. The DEP domain-containing mTOR-interacting protein (DEPTOR) was recently identified as an endogenous inhibitor of both mTORC1 and 2 through direct interactions, and is in turn degraded by mTORC1/2, adding an extra layer of complexity to the mTOR network...
January 12, 2018: Scientific Reports
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