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[This corrects the article DOI: 10.1371/journal.pcbi.1005154.].
May 2017: PLoS Computational Biology
Keiichi Kojima, Takahiro Yamashita, Yasushi Imamoto, Takehiro G Kusakabe, Motoyuki Tsuda, Yoshinori Shichida
Ci-opsin1 is a visible light-sensitive opsin present in the larval ocellus of an ascidian, Ciona intestinalis This invertebrate opsin belongs to the vertebrate visual and nonvisual opsin groups in the opsin phylogenetic tree. Ci-opsin1 contains candidate counterions (glutamic acid residues) at positions 113 and 181; the former is a newly acquired position in the vertebrate visual opsin lineage, whereas the latter is an ancestral position widely conserved among invertebrate opsins. Here, we show that Glu113 and Glu181 in Ci-opsin1 act synergistically as counterions, which imparts molecular properties to Ci-opsin1 intermediate between those of vertebrate- and invertebrate-type opsins...
May 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
A Quesada, R Gargallo-Caballero, Y Montaña, M Foerster, L Aballe, J F Fernández, J de la Figuera
High aspect-ratio Fe nanostrips are known to reversibly switch from a single-domain magnetic state to a multidomain diamond pattern as a function of temperature (T) and width. This magnetic bistability can be understood by the temperature-dependent balance between magnetocrystalline, shape and magnetoelastic anisotropies and has potential applications in magnetic logic devices. However, as Fe nanostructures easily oxidize, protecting the surface with capping layers may be required, which could largely affect the anisotropy balance...
May 13, 2017: Ultramicroscopy
Mattia D'Andola, Beatriz Rebollo, Adenauer G Casali, Julia F Weinert, Andrea Pigorini, Rosa Villa, Marcello Massimini, Maria V Sanchez-Vives
Measuring the spatiotemporal complexity of cortical responses to direct perturbations provides a reliable index of the brain's capacity for consciousness in humans under both physiological and pathological conditions. Upon loss of consciousness, the complex pattern of causal interactions observed during wakefulness collapses into a stereotypical slow wave, suggesting that cortical bistability may play a role. Bistability is mainly expressed in the form of slow oscillations, a default pattern of activity that emerges from cortical networks in conditions of functional or anatomical disconnection...
May 19, 2017: Cerebral Cortex
Alan Basset, Muriel Herd, Raecliffe Daly, Simon L Dove, Richard Malley
In Streptococcus pneumoniae, the type 1 pilus is involved in many steps of pathogenesis, including adherence to epithelial cells, mediation of inflammation, escape from macrophages, and the formation of biofilms. The type 1 pilus genes are expressed in a bistable fashion with cells switching between ON and OFF expression states. Bistable expression of these genes is due to their control by RlrA, a positive regulator subject to control by a positive feedback loop. The type 1 pilus genes are also thought to be negatively regulated by a large number of repressors...
May 15, 2017: Journal of Bacteriology
Nikos E Kouvaris, Michael Sebek, Albert Iribarne, Albert Díaz-Guilera, István Z Kiss
We present theoretical and experimental studies on pattern formation with bistable dynamical units coupled in a star network configuration. By applying a localized perturbation to the central or the peripheral elements, we demonstrate the subsequent spreading, pinning, or retraction of the activations; such analysis enables the characterization of the formation of stationary patterns of localized activity. The results are interpreted with a theoretical analysis of a simplified bistable reaction-diffusion model...
April 2017: Physical Review. E
Kiran Yadav, Neeraj Kumar Kamal, Manish Dev Shrimali
We present a method for attractor selection in multistable dynamical systems. It involves a feedback term that is active only when the dynamics of the system is in a particular fraction of state space of the attractor. We implement this method first on a simplest symmetric chaotic flow and then on a bistable neuronal system. We find that adding this space-dependent feedback term to the dynamical equations of these systems will drive the dynamics to the desired attractor by annihilating the other. We further demonstrate that the attractor selection due to this feedback term can be used in construction of logic gates, which is one of the practical applications of the proposed method...
April 2017: Physical Review. E
R K Singh
The Kramers problem for a dimer in a bistable piecewise linear potential is studied in the presence of correlated noise processes. The effect of such a correlation is to redistribute the thermal power between the dynamical degrees of freedom, and this leads to significant deviations in the dynamics of the system from the case of independent noise processes. The distribution of first passage times from one minima to the basin of attraction of the other minima is found to have exponentially decaying tails with the parameter dependent on the amount of correlation and the coupling between the particles...
April 2017: Physical Review. E
Jan O Haerter, Albert Díaz-Guilera, M Ángeles Serrano
The combination of bistability and noise is ubiquitous in complex systems, from biology to social interactions, and has important implications for their functioning and resilience. Here we use a simple three-state dynamical process, in which nodes go from one pole to another through an intermediate state, to show that noise can induce polarization switching in bistable systems if dynamical correlations are significant. In large, fully connected networks, where dynamical correlations can be neglected, increasing noise yields a collapse of bistability to an unpolarized configuration where the three possible states of the nodes are equally likely...
April 2017: Physical Review. E
Veith Weilnhammer, Heiner Stuke, Guido Hesselmann, Philipp Sterzer, Katharina Schmack
In bistable vision, subjective perception wavers between two interpretations of a constant ambiguous stimulus. This dissociation between conscious perception and sensory stimulation has motivated various empirical studies on the neural correlates of bistable perception, but the neurocomputational mechanism behind endogenous perceptual transitions has remained elusive. Here, we recurred to a generic Bayesian framework of predictive coding and devised a model that casts endogenous perceptual transitions as a consequence of prediction errors emerging from residual evidence for the suppressed percept...
May 15, 2017: PLoS Computational Biology
Yun Gao, Wen Zhou, Xiankai Sun, Hon Ki Tsang, Chester Shu
Cavity-enhanced thermo-optic bistability is studied in a graphene-on-Si<sub>3</sub>N<sub>4</sub> ring resonator. By engineering the coverage of the monolayer graphene on top of the Si<sub>3</sub>N<sub>4</sub> ring resonator, we observed a two-fold enhancement in the thermo-optically induced resonance shift rate and an 18-fold increase in the effective thermal nonlinear refractive index compared with the devices without graphene. The thermo-optic hysteresis loop was also characterized in this hybrid structure, where the experimental results agree well with the theoretical calculations...
May 15, 2017: Optics Letters
Dominique Zander, Daniel Samaga, Ronny Straube, Katja Bettenbrock
The Escherichia coli lac operon is regulated by a positive feedback loop whose potential to generate an all-or-none response in single cells has been a paradigm for bistable gene expression. However, so far bistable lac induction has only been observed using gratuitous inducers, raising the question about the biological relevance of bistable lac induction in the natural setting with lactose as the inducer. In fact, the existing experimental evidence points to a graded rather than an all-or-none response in the natural lactose uptake system...
May 9, 2017: Biophysical Journal
Maria D Manrique-Juarez, Fabrice Mathieu, Victoria Shalabaeva, Jean Cacheux, Sylvain Rat, Liviu Nicu, Thierry Leïchlé, Lionel Salmon, Gábor Molnár, Azzedine Bousseksou
We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)3 )2 ] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex...
May 10, 2017: Angewandte Chemie
F Ricci, R A Rica, M Spasenović, J Gieseler, L Rondin, L Novotny, R Quidant
Nano-mechanical resonators have gained an increasing importance in nanotechnology owing to their contributions to both fundamental and applied science. Yet, their small dimensions and mass raises some challenges as their dynamics gets dominated by nonlinearities that degrade their performance, for instance in sensing applications. Here, we report on the precise control of the nonlinear and stochastic bistable dynamics of a levitated nanoparticle in high vacuum. We demonstrate how it can lead to efficient signal amplification schemes, including stochastic resonance...
May 9, 2017: Nature Communications
Xinyu Tian, Bo Huang, Xiao-Peng Zhang, Mingyang Lu, Feng Liu, José N Onuchic, Wei Wang
Intrinsic tumor-suppressive mechanisms protect normal cells against aberrant proliferation. Although cellular signaling pathways engaged in tumor repression have been largely identified, how they are orchestrated to fulfill their function still remains elusive. Here, we built a tumor-suppressive network model composed of three modules responsible for the regulation of cell proliferation, activation of p53, and induction of apoptosis. Numerical simulations show a rich repertoire of network dynamics when normal cells are subject to serum stimulation and adenovirus E1A overexpression...
May 8, 2017: Proceedings of the National Academy of Sciences of the United States of America
Hirohito M Kondo, Takanori Kochiyama
Age-related changes in auditory and visual perception have an impact on the quality of life. It has been debated how perceptual organization is influenced by advancing age. From the neurochemical perspective, we investigated age effects on auditory and visual bistability. In perceptual bistability, a sequence of sensory inputs induces spontaneous switching between different perceptual objects. We used different modality tasks of auditory streaming and visual plaids. Young and middle-aged participants (20-60years) were instructed to indicate by a button press whenever their perception changed from one stable state to the other...
May 4, 2017: Neuroscience
Gerold Baier, Peter N Taylor, Yujiang Wang
Electro-cortical activity in patients with epilepsy may show abnormal rhythmic transients in response to stimulation. Even when using the same stimulation parameters in the same patient, wide variability in the duration of transient response has been reported. These transients have long been considered important for the mapping of the excitability levels in the epileptic brain but their dynamic mechanism is still not well understood. To investigate the occurrence of abnormal transients dynamically, we use a thalamo-cortical neural population model of epileptic spike-wave activity and study the interaction between slow and fast subsystems...
2017: Frontiers in Computational Neuroscience
Thomas Pugh, Nicholas F Chilton, Richard A Layfield
Single-molecule magnets (SMMs) are coordination compounds that exhibit magnetic bistability below a characteristic blocking temperature. Research in this field continues to evolve from its fundamental foundations towards applications of SMMs in information storage and spintronic devices. Synthetic chemistry plays a crucial role in targeting the properties that could ultimately produce SMMs with technological potential. The ligands in SMMs are invariably based on non-metals; we now report a series of dysprosium SMMs (in addition to their magnetically dilute analogues embedded in yttrium matrices) that contain ligands with the metalloid element antimony as the donor atom, i...
March 1, 2017: Chemical Science
Johannes Falk, Marc Mendler, Barbara Drossel
We investigate the influence of intrinsic noise on stable states of a one-dimensional dynamical system that shows in its deterministic version a saddle-node bifurcation between monostable and bistable behaviour. The system is a modified version of the Schlögl model, which is a chemical reaction system with only one type of molecule. The strength of the intrinsic noise is varied without changing the deterministic description by introducing bursts in the autocatalytic production step. We study the transitions between monostable and bistable behavior in this system by evaluating the number of maxima of the stationary probability distribution...
2017: PloS One
Zhaoyang Zhang, Danmeng Ma, Jun Liu, Yanyong Sun, Lin Cheng, Ghulam Abbas Khan, Yanpeng Zhang
By making use of the changes in optical properties such as absorption and dispersion around the resonance generated via electromagnetically induced transparency (EIT), we theoretically and experimentally investigate a "∞"-shape optical bistability (OB) versus frequency on the probe transmission with a Λ-shape EIT window in a rubidium atomic ensemble confined in a three-mirror optical ring cavity. Compared to the traditional OB reflected by a hysteresis loop versus power, such newly demonstrated optical bistable behavior (represented by a "∞"-shape non-overlapping region) by scanning probe and cavity detuning can experience dual bistabilities and be more sensitive to the change of experimental parameters...
April 17, 2017: Optics Express
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