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Christoph Ratzke, Jeff Gore
Microbes usually exist in communities consisting of myriad different but interacting species. These interactions are typically mediated through environmental modifications; microbes change the environment by taking up resources and excreting metabolites, which affects the growth of both themselves and also other microbes. We show here that the way microbes modify their environment and react to it sets the interactions within single-species populations and also between different species. A very common environmental modification is a change of the environmental pH...
March 14, 2018: PLoS Biology
Jessica L Hite, Clayton E Cressler
What drives the evolution of parasite life-history traits? Recent studies suggest that linking within- and between-host processes can provide key insight into both disease dynamics and parasite evolution. Still, it remains difficult to understand how to pinpoint the critical factors connecting these cross-scale feedbacks, particularly under non-equilibrium conditions; many natural host populations inherently fluctuate and parasites themselves can strongly alter the stability of host populations. Here, we develop a general model framework that mechanistically links resources to parasite evolution across a gradient of stable and unstable conditions...
May 5, 2018: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Nataliya Kraynyukova, Tatjana Tchumatchenko
A hallmark of cortical circuits is their versatility. They can perform multiple fundamental computations such as normalization, memory storage, and rhythm generation. Yet it is far from clear how such versatility can be achieved in a single circuit, given that specialized models are often needed to replicate each computation. Here, we show that the stabilized supralinear network (SSN) model, which was originally proposed for sensory integration phenomena such as contrast invariance, normalization, and surround suppression, can give rise to dynamic cortical features of working memory, persistent activity, and rhythm generation...
March 12, 2018: Proceedings of the National Academy of Sciences of the United States of America
Xiaotian Zhang, Jiteng Sheng, Haibin Wu
We explore theoretically the optomechanical interaction between a light field and a mechanical mode mediated by a Kerr nonlinear medium inside a Fabry-Perot cavity. When the system is driven by a strong and fast amplitude-modulated light field, i.e., in the so-called temporal rocking region, the cavity field and the mechanical oscillator show the characteristics of multistability. The rocking breaks down the continuous phase symmetry of the cavity field to a bistable case of two equivalent states with exact π phase difference...
March 5, 2018: Optics Express
Haichun Zhou, Jie Guo, Kun Xu, Zhe Li, Junqi Tang, Shiqing Man
The reflection of a TM-polarized light beam from a Kretschmann configuration with a saturable gain medium is investigated theoretically. Here, the dielectric constant of the gain medium is described by a classical Lorentzian oscillator model. When surface plasmon polaritons are effectively excited in this structure, it is demonstrated that the curves of enhanced total reflection (ETR) show different shaped hysteresis loops associated with optical bistability owing to gain saturation effect. The effects of the angle of incidence, the thickness of metal film, and the value of small-signal gain on bistable ETR are discussed in detail in a homogeneously broadened (HB) gain medium at line center...
March 5, 2018: Optics Express
Hao Ge, Pingping Wu, Hong Qian, Sunney Xiaoliang Xie
Within an isogenic population, even in the same extracellular environment, individual cells can exhibit various phenotypic states. The exact role of stochastic gene-state switching regulating the transition among these phenotypic states in a single cell is not fully understood, especially in the presence of positive feedback. Recent high-precision single-cell measurements showed that, at least in bacteria, switching in gene states is slow relative to the typical rates of active transcription and translation...
March 12, 2018: PLoS Computational Biology
Shakir Bilal, Edwin Michael
We study implications of complexity and seasonality in vector-host epidemiological models exhibiting backward bifurcation. Vector-host diseases represent complex infection systems that can vary in the transmission processes and population stages involved in disease progression. Seasonal fluctuations in external forcing factors can also interact in a complex way with internal host factors to govern the transmission dynamics. In backward bifurcation, the insufficiency of R 0  < 1 for predicting the stability of the disease-free equilibrium (DFE) state arises due to existence of bistability (coexisting DFE and endemic equilibria) for a range of R 0 values below one...
February 2018: Royal Society Open Science
Demetris Bates, Craig M Robertson, Alicea A Leitch, Paul A Dube, Richard T Oakley
Crystals of the heterocyclic radical naphtho-1,3,2-dithiazolyl NDTA display magnetic bistability with a well-defined hysteretic phase transition at Tc ↓ = 128(2) K and Tc ↑ = 188(2) K. The magnetic signature arises from a radical/dimer interconversion involving one of the two independent π-radicals in the P1̅ unit cell. Variable temperature X-ray crystallography has established that while all the radicals in HT-NDTA serve as paramagnetic ( S = 1/2) centers, half of the radicals in LT-NDTA form closed-shell N-N σ-bonded dimers ( S = 0) and half retain their S = 1/2 spin state...
March 7, 2018: Journal of the American Chemical Society
Hongbin Fang, Shih-Cheng A Chu, Yutong Xia, Kon Well Wang
Developing mechanical metamaterials with programmable properties is an emerging topic receiving wide attention. While the programmability mainly originates from structural multistability in previously designed metamaterials, here it is shown that nonflat-foldable origami provides a new platform to achieve programmability via its intrinsic self-locking and reconfiguration capabilities. Working with the single-collinear degree-4 vertex origami tessellation, it is found that each unit cell can self-lock at a nonflat configuration and, therefore, possesses wide design space to program its foldability and relative density...
March 7, 2018: Advanced Materials
Orsolya Kapuy, Diána Papp, Tibor Vellai, Gábor Bánhegyi, Tamás Korcsmáros
Although the primary role of autophagy-dependent cellular self-eating is cytoprotective upon various stress events (such as starvation, oxidative stress, and high temperatures), sustained autophagy might lead to cell death. A transcription factor called NRF2 (nuclear factor erythroid-related factor 2) seems to be essential in maintaining cellular homeostasis in the presence of either reactive oxygen or nitrogen species generated by internal metabolism or external exposure. Accumulating experimental evidence reveals that oxidative stress also influences the balance of the 5' AMP-activated protein kinase (AMPK)/rapamycin (mammalian kinase target of rapamycin or mTOR) signaling pathway, thereby inducing autophagy...
March 5, 2018: Antioxidants (Basel, Switzerland)
Yang Liu, Joseph Páez Chávez, Ekaterina Pavlovskaia, Marian Wiercigroch
This paper studies a position feedback control strategy for controlling a higher order drifting oscillator which could be used in modelling vibro-impact drilling. Special attention is given to two control issues, eliminating bistability and suppressing chaos, which may cause inefficient and unstable drilling. Numerical continuation methods implemented via the continuation platform COCO are adopted to investigate the dynamical response of the system. Our analyses show that the proposed controller is capable of eliminating coexisting attractors and mitigating chaotic behaviour of the system, providing that its feedback control gain is chosen properly...
February 2018: Proceedings. Mathematical, Physical, and Engineering Sciences
Marco Turi, David Charles Burr, Paola Binda
The pupil is primarily regulated by prevailing light levels but is also modulated by perceptual and attentional factors. We measured pupil-size in typical adult humans viewing a bistable-rotating cylinder, constructed so the luminance of the front surface changes with perceived direction of rotation. In some participants, pupil diameter oscillated in phase with the ambiguous perception, more dilated when the black surface was in front. Importantly, the magnitude of oscillation predicts autistic traits of participants, assessed by the Autism-Spectrum Quotient AQ...
March 6, 2018: ELife
Orsolya Kapuy, P K Vinod, Gábor Bánhegyi, Béla Novák
Ostreococcus tauri is the smallest free-living unicellular organism with one copy of each core cell cycle genes in its genome. There is a growing interest in this green algae due to its evolutionary origin. Since O. tauri is diverged early in the green lineage, relatively close to the ancestral eukaryotic cell, it might hold a key phylogenetic position in the eukaryotic tree of life. In this study, we focus on the regulatory network of its cell division cycle. We propose a mathematical modelling framework to integrate the existing knowledge of cell cycle network of O...
February 19, 2018: Plant Physiology and Biochemistry: PPB
Dola Sengupta, Sandip Kar
Neural stem cells (NSCs) often give rise to a mixed population of cells during differentiation. However, the dynamical origin of these mixed states is poorly understood. In this article, our mathematical modeling study demonstrates that the bone morphogenetic protein 2 (BMP2) mediated disparate differentiation dynamics of NSCs in central and peripheral nervous systems essentially function through two distinct bistable switches that are mutually interconnected via a mushroom-like bifurcation. Stochastic simulations of the model reveal that the mixed population originates due to the existence of these bistable switching regulations and that the maintenance of such mixed states depends on the level of stochastic fluctuations of the system...
February 27, 2018: Biophysical Journal
Myungwon Hwang, Andres F Arrieta
We demonstrate the utilisation of transition waves for realising input-invariant, frequency-independent energy harvesting in 1D lattices of bistable elements. We propose a metamaterial-inspired design with an integrated electromechanical transduction mechanism to the unit cell, rendering the power conversion capability an intrinsic property of the lattice. Moreover, focusing of transmitted energy to desired locations is demonstrated numerically and experimentally by introducing engineered defects in the form of perturbation in mass or inter-element forcing...
February 26, 2018: Scientific Reports
Yi-Pu Wang, Guo-Qiang Zhang, Dengke Zhang, Tie-Fu Li, C-M Hu, J Q You
We report the first observation of the magnon-polariton bistability in a cavity magnonics system consisting of cavity photons strongly interacting with the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors emerged as sharp frequency switchings of the cavity magnon polaritons (CMPs) and related to the transition between states with large and small numbers of polaritons. In our experiment, we align, respectively, the [100] and [110] crystallographic axes of the YIG sphere parallel to the static magnetic field and find very different bistable behaviors (e...
February 2, 2018: Physical Review Letters
A Zubillaga, P Ferreira, A J Parola, S Gago, N Basílio
A fluorescent bistable pseudorotaxane was devised and shown to display pH-gated photoresponsive ring shuttling. At pH > 7.5 shuttling does not take place after light stimulation while at pH ≈ 5 the macrocycle is quantitatively translocated.
February 26, 2018: Chemical Communications: Chem Comm
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
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
Bert Wuyts, Alan R Champneys, Joanna I House
This corrects the article DOI: 10.1038/ncomms15519.
February 21, 2018: Nature Communications
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